TY - JOUR A1 - Movahedifar, Fahimeh A1 - Modarresi-Alam, Ali Reza A1 - Kleinpeter, Erich A1 - Schilde, Uwe T1 - Dynamic H-1-NMR study of unusually high barrier to rotation about the partial C-N double bond in N,N-dimethyl carbamoyl 5-aryloxytetrazoles JF - Journal of molecular structure N2 - The synthesis of new N,N-dimethyl carbamoyl 5-aryloxytetrazoles have been reported. Their dynamic H-1-NMR via rotation about C-N bonds in moiety of urea group [a; CO-NMe2 and b; (2-tetrazolyl)N-CO rotations] in the solvents CDCl3 (223-333 K) and DMSO (298-363 K) is studied. Accordingly, the free energies of activation, obtained 16.5 and 16.9 kcal mol(-1) respectively, attributed to the conformational isomerization about the Me2N-C=O bond (a rotation). Moreover, a and b barrier to rotations in 5-((4-methylphenoxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide (P) also were computed at level of B3LYP using 6-311++G** basis set. The optimized geometry parameters are in good agreement with X-ray structure data. The computation of energy barrier for a and b was determined 16.9 and 2.5 kcal mol(-1), respectively. The former is completely in agreement with the result obtained via dynamic NMR. X-ray structure analysis data demonstrate that just 2-acylated tetrazole was formed in the case of 5-(p-tolyloxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide. X-ray data also revealed a planar trigonal orientation of the Me2N group which is coplanar to carbonyl group with the partial double-bond C-N character. It also demonstrates the synperiplanar position of C=O group with tetrazolyl ring. On average, in solution the plane containing carbonyl bond is almost perpendicular to the plane of the tetrazolyl ring (because of steric effects as confirmed by B3LY12/6-311++G**) while the plane containing Me2N group is coplanar with carbonyl bond which is in contrast with similar urea derivatives and it demonstrates the unusually high rotational energy barrier of these compounds. (C) 2016 Elsevier B.V. All rights reserved. KW - Dynamic H-1-NMR KW - Carbamoyl tetrazoles KW - Barrier to rotation about C-N bond KW - pi-Stacking KW - B3LYP/6-311++G** Y1 - 2017 U6 - https://doi.org/10.1016/j.molstruc.2016.12.010 SN - 0022-2860 SN - 1872-8014 VL - 1133 SP - 244 EP - 252 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hansen, Poul Erik A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Ring current and anisotropy effects on OH chemical shifts in resonance-assisted intramolecular H-bonds JF - Tetrahedron letters N2 - Ring current effects on resonance-assisted and intramolecularly bridged hydrogen bond protons for 10-hydroxybenzo[h]quinoline 1 and a number of related compounds were calculated and the through-space NMR shieldings (TSNMRS) obtained hereby visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. These calculations revealed that this through-space effect is comparably large (up to 2 ppm) dependent on the position of the intramolecularly bridged OH proton, and therefore, contribute considerably to the chemical shift of the latter making it questionable to use delta(OH)/ppm in the estimation of intramolecular hydrogen bond strength without taking this into account. Furthermore, the anisotropy effects of additional groups on the aromatic moiety (e.g. the carbonyl group in salicylaldehyde or in o-hydroxyacetophenone of ca. 0.6 ppm deshielding) should also be considered. These through-space effects need to be taken into account when using OH chemical shifts to estimate hydrogen bond strength. KW - RA-intramolecular hydrogen bond KW - Through-space NMR shieldings (TSNMRS) KW - Iso-chemical-shielding surfaces (ICSS) KW - Ring current effect KW - Anisotropy effect Y1 - 2018 U6 - https://doi.org/10.1016/j.tetlet.2018.05.006 SN - 0040-4039 VL - 59 IS - 23 SP - 2288 EP - 2292 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Buyinza, Daniel A1 - Derese, Solomon A1 - Ndakala, Albert A1 - Heydenreich, Matthias A1 - Yenesew, Abiy A1 - Koch, Andreas A1 - Oriko, Richard T1 - A coumestan and a coumaronochromone from Millettia lasiantha JF - Biochemical systematics and ecology N2 - The manuscript describes the phytochemical investigation of the roots, leaves and stem bark of Millettia lasiantha resulting in the isolation of twelve compounds including two new isomeric isoflavones lascoumestan and las-coumaronochromone. The structures of the new compounds were determined using different spectroscopic techniques. KW - Millettia lasiantha KW - Leguminosae KW - Coumestan KW - Coumaronochromone Y1 - 2021 U6 - https://doi.org/10.1016/j.bse.2021.104277 SN - 0305-1978 SN - 1873-2925 VL - 97 PB - Elsevier CY - Oxford ER - TY - THES A1 - Heinz, Markus T1 - Synthese von Monomeren auf der Basis nachwachsender Rohstoffe und ihre Polymerisation T1 - Synthesis of Monomers based on Renewable Resources and their Polymerization N2 - Die vorliegende Arbeit thematisiert die Synthese und die Polymerisation von Monomeren auf der Basis nachwachsender Rohstoffe wie zum Beispiel in Gewürzen und ätherischen Ölen enthaltenen kommerziell verfügbaren Phenylpropanoiden (Eugenol, Isoeugenol, Zimtalkohol, Anethol und Estragol) und des Terpenoids Myrtenol sowie ausgehend von der Rinde einer Birke (Betula pendula) und der Korkeiche (Quercus suber). Ausgewählte Phenylpropanoide (Eugenol, Isoeugenol und Zimtalkohol) und das Terpenoid Myrtenol wurden zunächst in den jeweiligen Laurylester überführt und anschließend das olefinische Strukturelement epoxidiert, wobei 4 neue (2-Methoxy-4-(oxiran-2-ylmethyl)phenyldodecanoat, 2-Methoxy-4-(3-methyl-oxiran-2-yl)phenyldodecanoat, (3-Phenyloxiran-2-yl)methyldodecanoat, (7,7-Dimethyl-3-oxatricyclo[4.1.1.02,4]octan-2-yl)methyldodecanoat) und 2 bereits bekannte monofunktionelle Epoxide (2-(4-Methoxybenzyl)oxiran und 2-(4-Methoxyphenyl)-3-methyloxiran) erhalten wurden, die mittels 1H-NMR-, 13C-NMR- und FT-IR-Spektroskopie sowie mit DSC untersucht wurden. Die Photo-DSC Untersuchung der Epoxidmonomere in einer kationischen Photopolymerisation bei 40 °C ergab die maximale Polymerisationsgeschwindigkeit (Rpmax: 0,005 s-1 bis 0,038 s-1) sowie die Zeit (tmax: 13 s bis 26 s) bis zum Erreichen des Rpmax-Wertes und führte zu flüssigen Oligomeren, deren zahlenmittlerer Polymerisationsgrad mit 3 bis 6 mittels GPC bestimmt wurde. Die Umsetzung von 2-Methoxy-4-(oxiran-2-ylmethyl)phenyldodecanoat mit Methacrylsäure ergab ein Isomerengemisch (2-Methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyldodecanoat und 2-Methoxy-4-(2-(methacryl-oyloxy)-3-hydroxypropyl)phenyldodecanoat), das mittels Photo-DSC in einer freien radikalischen Photopolymerisation untersucht wurde (Rpmax: 0,105 s-1 und tmax: 5 s), die zu festen in Chloroform unlöslichen Polymeren führte. Aus Korkpulver und gemahlener Birkenrinde wurden selektiv 2 kristalline ω-Hydroxyfettsäuren (9,10-Epoxy-18-hydroxyoctadecansäure und 22-Hydroxydocosansäure) isoliert. Die kationische Photopolymerisation der 9,10-Epoxy-18-hydroxyoctadecansäure ergab einen nahezu farblosen transparenten und bei Raumtemperatur elastischen Film, welcher ein Anwendungspotential für Oberflächenbeschichtungen hat. Aus der Reaktion von 9,10-Epoxy-18-hydroxyoctadecansäure mit Methacrylsäure wurde ein bei Raumtemperatur flüssiges Gemisch aus zwei Konstitutionsisomeren (9,18-Dihydroxy-10-(methacryloyloxy)octadecansäure und 9-(Methacryloyloxy)-10,18-dihydroxyoctadecansäure) erhalten (Tg: -60 °C). Die radikalische Photopolymerisation dieser Konstitutionsisomere wurde ebenfalls mittels Photo-DSC untersucht (Rpmax: 0,098 s-1 und tmax: 3,8 s). Die Reaktion von 22-Hydroxydocosansäure mit Methacryloylchlorid ergab die kristalline 22-(Methacryloyloxy)docosansäure, welche ebenfalls in einer radikalischen Photopolymerisation mittels Photo-DSC untersucht wurde (Rpmax: 0,023 s-1 und tmax: 9,6 s). Die mittels AIBN in Dimethylsulfoxid initiierte Homopolymerisation der 22-(Methacryloyloxy)docosansäure und der Isomerengemische bestehend aus 2-Methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyldodecanoat und 2-Methoxy-4-(2-(methacryl-oyloxy)-3-hydroxypropyl)phenyldodecanoat sowie aus 9,18-Dihydroxy-10-(methacryloy-loxy)octadecansäure und 9-(Methacryloyloxy)-10,18-dihydroxyoctadecansäure ergab feste lösliche Polymere, die mittels 1H-NMR- und FT-IR-Spektroskopie, GPC (Poly(2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyldodecanoat / 2-methoxy-4-(2-(methacryloyloxy)-3-hydroxypropyl)phenyldodecanoat): Pn = 94) und DSC (Poly(2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyldodecanoat / 2-methoxy-4-(2-(methacryloyloxy)-3-hydroxypropyl)phenyldodecanoat): Tg: 52 °C; Poly(9,18-dihydroxy-10-(methacryloyloxy)-octadecansäure / 9-(methacryloyloxy)-10,18-dihydroxyoctadecansäure): Tg: 10 °C; Poly(22-(methacryloyloxy)docosansäure): Tm: 74,1 °C, wobei der Schmelzpunkt mit dem des Photopolymers (Tm = 76,8 °C) vergleichbar ist) charakterisiert wurden. Das bereits bekannte Monomer 4-(4-Methacryloyloxyphenyl)butan-2-on wurde ausgehend von 4-(4-Hydroxyphenyl)butan-2-on hergestellt, welches aus Birkenrinde gewonnen werden kann, und unter identischen Bedingungen für einen Vergleich mit den neuen Monomeren polymerisiert. Die freie radikalische Polymerisation führte zu Poly(4-(4-methacryloyloxyphenyl)butan-2-on) (Pn: 214 und Tg: 83 °C). Neben der Homopolymerisation wurde eine statistische Copolymerisation des Isomerengemisches 2-Methoxy-4-(2-hydroxy-3-(methacryl-oyloxy)propyl)phenyldodecanoat / 2-Methoxy-4-(2-(methacryloyloxy)-3-hydroxypropyl)-phenyldodecanoat mit 4-(4-Methacryloyloxyphenyl)butan-2-on untersucht, wobei ein äquimolarer Einsatz der Ausgangsmonomere zu einem Anstieg der Ausbeute, der Molmassenverteilung und der Dispersität des Copolymers (Tg: 44 °C) führte. Die unter Verwendung von Diethylcarbonat als „grünes“ Lösungsmittel mittels AIBN initiierten freien radikalischen Homopolymerisationen von 4-(4-Methacryloyloxyphenyl)butan-2-on und von Laurylmethacrylat ergaben vergleichbare Polymerisationsgrade der Homopolymere (Pn: 150), welche jedoch aufgrund ihrer Strukturunterschiede deutlich unterschiedliche Glasübergangstemperaturen hatten (Poly(4-(4-methacryloyloxyphenyl)butan-2-on): Tg: 70 °C, Poly(laurylmethacrylat) Tg: -49 °C. Eine statistische Copolymerisation äquimolarer Stoffmengen der beiden Monomere in Diethylcarbonat führte bei einer Polymerisationszeit von 60 Minuten zu einem leicht bevorzugten Einbau des 4-(4-Methacryloyloxyphenyl)butan-2-on in das Copolymer (Tg: 17 °C). Copolymerisationsdiagramme für die freien radikalischen Copolymerisationen von 4-(4-Methacryloyloxyphenyl)butan-2-on mit n-Butylmethacrylat beziehungsweise 2-(Dimethylamino)ethylmethacrylat (t: 20 min bis 60 min; Molenbrüche (X) für 4-(4-Methacryloyloxyphenyl)butan-2-on: 0,2; 0,4; 0,6 und 0,8) zeigten ein nahezu ideales azeotropes Copolymerisationsverhalten, obwohl ein leicht bevorzugter Einbau von 4-(4-Methacryloyloxyphenyl)butan-2-on in das jeweilige Copolymer beobachtet wurde. Dabei korreliert ein Anstieg der Ausbeute und der Glasübergangstemperatur der erhaltenen Copolymere mit einem zunehmenden Gehalt an 4-(4-Methacryloyloxyphenyl)butan-2-on im Reaktionsgemisch. Die unter Einsatz der modifizierten Gibbs-DiMarzio-Gleichung berechneten Glasübergangstemperaturen der Copolymere stimmten mit den gemessenen Werten gut überein. Das ist eine gute Ausgangsbasis für die Bestimmung der Glasübergangstemperatur eines Copolymers mit einer beliebigen Zusammensetzung. N2 - The subject of this work is the synthesis and polymerization of monomers based on renewable material e. g. commercially available phenylpropanoides (eugenol, iso-eugenol, cinnamyl alcohol, anethol, and estragol) containing in spices and essential oils, the terpenoid myrtenol, as well as material derived from the bark of a birch (Betula pendula) and cork oak (Quercus suber). Selected phenylpropanoides (eugenol, iso-eugenol and cinnamyl alcohol) and the terpenoid myrtenol were first transferred to the lauryl ester followed by epoxidation of the olefinic structure to yield 4 new (2-methoxy-4-(oxiran-2-ylmethyl)-phenyl dodecanoate, 2-methoxy-4-(3-methyloxiran-2-yl)phenyl dodecanoate, (3-phenyloxiran-2-yl)methyl dodecanoate, (7,7-dimethyl-3-oxatricyclo[4.1.1.02,4]octan-2-yl)methyl dodecanoate) and 2 already known monofunctional epoxides (2-(4-methoxybenzyl)oxirane and 2-(4-methoxy-phenyl)-3-methyloxirane), which were investigated using 1H-NMR-, 13C-NMR- and FT-IR- spectroscopy, and DSC. Photo-DSC investigation of the cationic polymerization of the epoxy monomers at 40 °C revealed the maximum polymerization rate (Rpmax: 0,005 s-1 to 0,038 s-1) and the time (tmax: 13 s to 26 s) to obtain the Rpmax value. Liquid oligomers were obtained with a number average degree of polymerization between 3 and 6, as determined by GPC. The reaction of 2-methoxy-4-(oxiran-2-ylmethyl)phenyl dodecanoate with methacrylic acid resulted in a mixture of isomers (2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)-phenyl dodecanoate and 2-methoxy-4-(2-(methacryloyloxy)-3-hydroxypropyl)phenyl dodecanoate). Free radical photopolymerization of this isomeric mixture, studied by photo-DSC (Rpmax: 0,105 s-1 and tmax: 5 s), resulted in solid polymers that were insoluble in chloroform. Two crystalline ω-hydroxy fatty acids (9,10-epoxy-18-hydroxyoctadecanoic acid and 22-hydroxydocosanoic acid) were selectively isolated from cork powder and powdered birch bark. The cationic photopolymerization of 9,10-epoxy-18-hydroxyoctadecanoic acid resulted in a nearly colorless transparent film that was elastic at room temperature. Therefore, it has an application potential in the manufacture of coatings. The reaction of 9,10-epoxy-18-hydroxyoctadecanoic acid with methacrylic acid resulted in a mixture of two constitutional isomers (9,18-dihydroxy-10-(methacryloyloxy)octadecanoic acid and 9-(methacryloyloxy)-10,18-dihydroxyoctadecanoic acid), which is liquid at room temperature (Tg: -60 °C). The radical photopolymerization of these constitutional isomers was also studied by photo-DSC (Rpmax: 0,098 s-1 and tmax: 3,8 s). The reaction of 22-hydroxydocosanoic acid with methacryloyl chloride yielded crystalline 22-(methacryloyloxy)docosanoic acid, which was studied by photo-DSC in a radical photopolymerization (Rpmax: 0,023 s-1 and tmax: 9,6 s). The homopolymerization of both 22-(methacryloyloxy)docosanoic acid and the isomeric mixtures consisting of 2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyl dodecanoate and 2-methoxy-4-(2-(methacryloyloxy)-3-hydroxypropyl)phenyl dodecanoat as well as 9,18-dihydroxy-10-(methacryloyloxy)octadecanoic acid and 9-(methacryloyloxy)-10,18-dihydroxyoctadecanoic acid resulted in solid soluble polymers, which were characterized by 1H-NMR- and FT-IR-spectroscopy, GPC (poly(2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyl dodecanoat / 2-methoxy-4-(2-(methacryloyloxy)-3-hydroxy-propyl)phenyl dodecanoate): Pn = 94), and DSC (poly(2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyl dodecanoate / 2-methoxy-4-(2-(methacryloyloxy)-3-hydroxy-propyl)phenyl dodecanoate): Tg: 52 °C; poly(9,18-dihydroxy-10-(methacryloyloxy)-octadecanoic acid / 9-(methacryloyloxy)-10,18-dihydroxyoctadecanoic acid): Tg: 10 °C; poly(22-(methacryloyloxy)docosanoic acid): Tm: 74,1 °C, this melting temperature is comparable to that of the photopolymer (Tm = 76,8 °C)). The already known monomer 4-(4-methacryloyloxyphenyl)butane-2-one was synthesized from 4-(4-hydroxyphenyl)butan-2-one obtained from birch bark and polymerized under identical conditions for comparison with the new monomers. The free radical polymerization resulted in poly(4-(4-methacryloyloxyphenyl)butan-2-one) (Pn: 214 and Tg: 83 °C). Besides the homopolymerization, a random copolymerization of the 2-methoxy-4-(2-hydroxy-3-(methacryloyloxy)propyl)phenyl dodecanoate / 2-methoxy-4-(2-(methacryloyl-oxy)-3-hydroxypropyl)phenyl dodecanoate isomer mixture with 4-(4-methacryloyloxyphenyl)butan-2-one was also investigated, which resulted in an increase in the yield, molecular weight distribution and dispersity of the copolymer (Tg: 44 °C) at a stoichiometric ratio of the monomers. The application of diethyl carbonate as „green“ solvent in the free radical homopolymerization of both 4-(4-methacryloyloxyphenyl)butan-2-one and lauryl methacrylate initiated with AIBN resulted in a comparable degree of polymerization of the homopolymers obtained (Pn: 150). However, due to the structural differences of the monomer segments, different glass transition temperatures were obtained for poly(4-(4-methacryloyloxyphenyl)butan-2-one) (Tg: 70 °C) and poly(lauryl methacrylate) (Tg: -49 °C). A random copolymerization of a stoichiometric ratio of the monomers in diethyl carbonate resulted in a slightly preferential incorporation of the 4-(4-methacryloyloxyphenyl)butan-2-one in the copolymer (Tg: 17 °C) after a polymerization time of 60 min. Copolymerization diagrams for free radical copolymerizations of 4-(4-methacryloyloxyphenyl)butan-2-one with either n-butyl methacrylate or 2-(dimethylamino)ethyl methacrylate (t: 20 min to 60 min; molar fraction (X) for 4-(4-methacryloyloxyphenyl)butan-2-one: 0,2; 0,4; 0,6 and 0,8) showed an almost ideal azeotropic copolymerization behavior, although a slightly preferential incorporation of the 4-(4-methacryloyloxyphenyl)butan-2-one was observed in the copolymers. An increase in both yield and glass transition temperature of the copolymers obtained correlated with an increasing content on 4-(4-methacryloyloxyphenyl)butan-2-one in the reaction mixture. Good agreement was found between the glass transition temperatures calculated using the modified Gibbs-DiMarzio equation and the measured values for the copolymers. This is a good basis for determining the glass transition temperature of a copolymer of any composition. KW - photoinitiierte kationische Polymerisation KW - Epoxide KW - epoxidierte Phenylpropanoide KW - epoxidierte Terpene KW - Copolymerisationsdiagramme KW - freie radikalische Polymerisation KW - Glasübergangstemperaturen KW - Methacrylate KW - Molmassen KW - statistische Copolymere KW - 9,10-Epoxy-18-hydroxyoctadecansäure KW - biobasierte Methacrylate KW - biobasierte Monomere KW - nachwachsende Rohstoffe KW - 22-Hydroxydocosansäure KW - photoinitiierte Polymerisation KW - Polymerisation KW - Betula pendula KW - Quercus suber KW - Birke KW - Korkeiche KW - Biomasse KW - Birkenrinde KW - grüne Chemie KW - Polymere KW - photoinitiierte freie radikalische Polymerisation KW - 22-hydroxydocosanoic acid KW - 9,10-epoxy-18-hydroxyoctadecanoic acid KW - Betula pendula KW - biomass KW - birch KW - birch bark KW - copolymerization diagrams KW - Epoxides KW - Glass transition temperatures KW - Cork oak KW - Methacrylates KW - Molar masses KW - polymers KW - polymerization KW - Quercus suber KW - bio-based methacrylates KW - bio-based monomers KW - epoxidized phenylpropanoids KW - epoxidized terpenes KW - free radical polymerization KW - green chemistry KW - renewable raw materials KW - photoinitiated polymerization KW - photoinitiated free radical KW - photoinitiated cationic polymerization KW - random copolymers KW - photopolymerization KW - Baumrinde KW - Rinde KW - tree bark KW - bark KW - Photopolymerisation Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-637943 ER - TY - JOUR A1 - Xu, Xun A1 - Nie, Yan A1 - Wang, Weiwei A1 - Ma, Nan A1 - Lendlein, Andreas T1 - Periodic thermomechanical modulation of toll-like receptor expression and distribution in mesenchymal stromal cells JF - MRS communications / a publication of the Materials Research Society N2 - Toll-like receptor (TLR) can trigger an immune response against virus including SARS-CoV-2. TLR expression/distribution is varying in mesenchymal stromal cells (MSCs) depending on their culture environments. Here, to explore the effect of periodic thermomechanical cues on TLRs, thermally controlled shape-memory polymer sheets with programmable actuation capacity were created. The proportion of MSCs expressing SARS-CoV-2-associated TLRs was increased upon stimulation. The TLR4/7 colocalization was promoted and retained in the endoplasmic reticula. The TLR redistribution was driven by myosin-mediated F-actin assembly. These results highlight the potential of boosting the immunity for combating COVID-19 via thermomechanical preconditioning of MSCs. KW - Actuation KW - Antiviral KW - Biomaterial KW - COVID-19 KW - Shape memory Y1 - 2021 U6 - https://doi.org/10.1557/s43579-021-00049-5 SN - 2159-6867 VL - 11 IS - 4 SP - 425 EP - 431 PB - Springer CY - Berlin ER - TY - JOUR A1 - Zude, Manuela A1 - Hashim, Norhashila A1 - Hass, Roland A1 - Polley, Nabarun A1 - Regen, Christian T1 - Validation study for measuring absorption and reduced scattering coefficients by means of laser-induced backscattering imaging JF - Postharvest Biology and Technology N2 - Decoupling of optical properties appears challenging, but vital to get better insight of the relationship between light and fruit attributes. In this study, nine solid phantoms capturing the ranges of absorption (μa) and reduced scattering (μs’) coefficients in fruit were analysed non-destructively using laser-induced backscattering imaging (LLBI) at 1060 nm. Data analysis of LLBI was carried out on the diffuse reflectance, attenuation profile obtained by means of Farrell’s diffusion theory either calculating μa [cm−1] and μs’ [cm−1] in one fitting step or fitting only one optical variable and providing the other one from a destructive analysis. The nondestructive approach was approved when calculating one unknown coefficient non-destructively, while no ability of the method was found to analysis both, μa and μs’, non-destructively. Setting μs’ according to destructive photon density wave (PDW) spectroscopy and fitting μa resulted in root mean square error (rmse) of 18.7% in comparison to fitting μs’ resulting in rmse of 2.6%, pointing to decreased measuring uncertainty, when the highly variable μa was known. The approach was tested on European pear, utilizing destructive PDW spectroscopy for setting one variable, while LLBI was applied for calculating the remaining coefficient. Results indicated that the optical properties of pear obtained from PDW spectroscopy as well as LLBI changed concurrently in correspondence to water content mainly. A destructive batch-wise analysis of μs’ and online analysis of μa may be considered in future developments for improved fruit sorting results, when considering fruit with high variability of μs’. KW - Absorption KW - European pear KW - Fruit quality KW - Phantoms KW - Reduced scattering coefficient KW - Scattering KW - Spatially resolved spectroscopy Y1 - 2019 U6 - https://doi.org/10.1016/j.postharvbio.2019.04.002 SN - 0925-5214 SN - 1873-2356 VL - 153 SP - 161 EP - 168 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Adebayo, Segun Emmanuel A1 - Hashim, Norhashila A1 - Hass, Roland A1 - Reich, Oliver A1 - Regen, Christian A1 - Münzberg, Marvin A1 - Abdan, Khalina A1 - Hanafi, Marsyita A1 - Zude, Manuela T1 - Using absorption and reduced scattering coefficients for non-destructive analyses of fruit flesh firmness and soluble solids content in pear JF - Postharvest Biology and Technology N2 - Quality attributes of fruit determine its acceptability by the retailer and consumer. The objective of this work was to investigate the potential of absorption (μa) and reduced scattering (μs’) coefficients of European pear to analyze its fruit flesh firmness and soluble solids content (SSC). The absolute reference values, μa* (cm−1) and μs’* (cm−1), of pear were invasively measured, employing multi-spectral photon density wave (PDW) spectroscopy at preselected wavelengths of 515, 690, and 940 nm considering two batches of unripe and overripe fruit. On eight measuring dates during fruit development, μa and μs’ were analyzed non-destructively by means of laser light backscattering imaging (LLBI) at similar wavelengths of 532, 660, and 830 nm by means of fitting according to Farrell’s diffusion theory, using fix reference values of either μa* or μs’*. Both, the μa* and the μa as well as μs’* and μs’ showed similar trends. Considering the non-destructively measured data during fruit development, μa at 660 nm decreased 91 till 141 days after full bloom (dafb) from 1.49 cm−1 to 0.74 cm−1 due to chlorophyll degradation. At 830 nm, μa only slightly decreased from 0.41 cm−1 to 0.35 cm−1. The μs’ at all wavelengths revealed a decreasing trend as the fruit developed. The difference measured at 532 nm was most pronounced decreasing from 24 cm−1 to 10 cm−1, while at 660 nm and 830 nm values decreased from 15 cm−1 to 13 cm−1 and from 10 cm−1 to 8 cm−1, respectively. When building calibration models with partial least-squares regression analysis on the optical properties for non-destructive analysis of the fruit SSC, μa at 532 nm and 830 nm resulted in a correlation coefficient of R = 0.66, however, showing high measuring uncertainty. The combination of all three wavelengths gave an enhanced, encouraging R = 0.89 for firmness analysis using μs’ in the freshly picked fruit. KW - Absorption KW - Non-destructive KW - Pear KW - Quality KW - Scattering Y1 - 2017 U6 - https://doi.org/10.1016/j.postharvbio.2017.04.004 SN - 0925-5214 SN - 1873-2356 VL - 130 SP - 56 EP - 63 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Erler, Alexander T1 - Entwicklung von online-Detektionsverfahren für landwirtschaftlich relevante Analyten N2 - Die Entwicklung nachhaltiger Bewirtschaftungs- und Produktionsmethoden ist eine der zentralen Fragestellungen der modernen Agrarwirtschaft. Die vorliegende Arbeit beschäftigt sich mit zwei Forschungsthemen, die das Konzept Nachhaltigkeit beinhalten. In beiden Fällen werden analytische Grundlagen für die Entwicklung entsprechender landwirtschaftlicher Arbeitsmethoden gelegt. Das erste Thema ist an den sogenannten Präzisionsackerbau angelehnt. Bei diesem wird die Bearbeitung von Agrarflächen ortsabhängig ausgeführt. Das heißt, die Ausbringung von Saatgut, Dünger, Bewässerung usw. richtet sich nach den Eigenschaften des jeweiligen Standortes und wird nicht pauschal gleichmäßig über ein ganzes Feld verteilt. Voraussetzung hierfür ist eine genaue Kenntnis der Bodeneigenschaften. In der vorliegenden Arbeit sollten diese Parameter mittels der analytischen Technik der Laser-induzierten Breakdown Spektroskopie (LIBS), die eine Form der Elementaranalyse darstellt, bestimmt werden. Bei den hier gesuchten Bodeneigenschaften handelte es sich um die Gehalte von Nährstoffen sowie einige sekundäre Parameter wie den Humusanteil, den pH-Wert und den pflanzenverfügbaren Anteil einzelner Nährstoffe. Diese Eigenschaften wurden durch etablierte Referenzanalysen bestimmt. Darauf aufbauend wurden die Messergebnissen der LIBS-Untersuchungen durch verschiedene Methoden der sogenannten multivariaten Datenanalyse (MVA) ausgewertet. Daraus sollten Modelle zur Vorhersage der Bodenparameter in zukünftigen LIBS-Messungen erarbeitet werden. Die Ergebnisse dieser Arbeit zeigten, dass mit der Kombination von LIBS und MVA sämtliche Bodenparameter erfolgreich vorhergesagt werden konnten. Dies beinhaltete sowohl die tatsächlich messbaren Elemente als auch die sekundären Eigenschaften, welche durch die MVA mit den Elementgehalten in Zusammenhang gebracht wurden. Das zweite Thema beschäftigt sich mit der Vermeidung von Verlusten durch Schädlingsbefall bei der Getreidelagerung. Hier sollten mittels der Ionenmobilitätsspektrometrie (IMS) Schimmelpilzkontaminationen detektiert werden. Dabei wurde nach den flüchtigen Stoffwechselprodukten der Pilze gesucht. Die durch Referenzmessungen mit Massenspektrometern identifizierten Substanzen konnten durch IMS im Gasvolumen über den Proben, dem sogenannten Headspace, nachgewiesen werden. Dabei wurde nicht nur die Anwesenheit einer Kontamination festgestellt, sondern diese auch charakterisiert. Die freigesetzten Substanzen bildeten spezifische Muster, anhand derer die Pilze identifiziert werden konnten. Hier wurden sowohl verschiedene Gattungen als auch einzelne Arten unterschieden. Die Messungen fanden auf verschiedenen Nährböden statt um den Einfluss dieser auf die Stoffwechselprodukte zu beobachten. Auch die sekundären Stoffwechselprodukte der Schimmelpilze, die Mykotoxine, konnten durch IMS detektiert werden. Beide in dieser Arbeit vorgestellten Forschungsthemen konnten erfolgreich abgeschlossen werden. Sowohl LIBS als auch IMS erwiesen sich für den Nachweis der jeweiligen Analyten als geeignet, und der Einsatz moderner computergestützter Auswertemethoden ermöglichte die genaue Charakterisierung der gesuchten Parameter. Beide Techniken können in Form von mobilen Geräten verwendet werden und zeichnen sich durch eine schnelle und sichere Analyse aus. In Kombination mit entsprechenden Modellen der MVA sind damit alle Voraussetzungen für Vor-Ort-Untersuchungen und damit für den Einsatz in der Landwirtschaft erfüllt. N2 - The basis of modern agriculture is sustainable cultivation and production. Two of the research subjects of this thesis are related to this topic. The aim of both is the development of an analytical method for sustainable agriculture. The first topic is an application for precision agriculture, which is the side specific cultivation of agricultural areas. The local properties of each m² of the field are determined and used for sowing, fertilizing or irrigation instead of using standardized quantities for the entire field. This practice requires detailed knowledge of the soil properties. In this work, some of these soil properties were determined by laser-induced breakdown spectroscopy (LIBS), which is a form of elementary analysis. The evaluated properties are the total amounts of several elemental nutrients as well as some secondary parameters, such as pH value, humus-content and the plant available contents of a number of nutrients. Soil samples with reference values from established analytical methods were used. Various methods of multivariate analysis (MVA) were used for developing different calibration models based on the LIBS data. These models can be used to predict soil properties from future LIBS experiments on soils. The results of the combination of LIBS and MVA were reliable predictions for the total amounts of elements, which can directly be correlated to LIBS signals in the measurements, as well as the secondary parameters, which can only be correlated with the LIBS spectra by MVA. The second topic of this thesis was the detection of pest infestations of stored grains for preventing economic losses. Ion mobility spectrometry (IMS) was used to detect mould fungus contaminations. The target substances were volatile metabolites emitted by the fungi. Reference measurements by mass spectrometry (MS) identified the substances found in the headspace of the samples, which are also detected by IMS. In addition to the detection of a contamination, an identification of the contaminant was also possible because the substances emitted by the fungi formed specific patterns. Therefore, it was possible to discriminate not only various fungus genera but also individual species. Additionally, the influence of different growth media used for fungus cultivation on the metabolites emitted was investigated. In addition to the detection of volatile metabolites, the direct detection of mycotoxins by IMS could also be demonstrated. The goals of both research topics presented in this thesis were successfully achieved. LIBS and IMS could be used to detect the respective analytes and a characterization of the target parameters was possible using computer-assisted data processing. Common features of both techniques are the availability of mobile instrumentation and a fast and reliable analytical performance. In combination with MVA-based prediction models, they fulfil the requirements for in-field analysis, which potentially makes them well suited to a wide range of applications in modern agriculture. KW - Ionenmobilitätsspektrometrie KW - Laser induzierte Breakdown Spektroskopie KW - Schimmelpilze KW - Bodenanalytik KW - ion mobility spectrometry KW - laser induced breakdown spectroscopy KW - mold fungi KW - soil analysis Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-473406 ER - TY - JOUR A1 - Erler, Alexander A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Grothusheitkamp, Daniela A1 - Kunz, T. A1 - Methner, Frank-Jürgen T1 - Detection of volatile organic compounds in the headspace above mold fungi by GC-soft X-radiation-based APCI-MS JF - Journal of mass spectrometr N2 - Mold fungi on malting barley grains cause major economic loss in malting and brewery facilities. Possible proxies for their detection are volatile and semivolatile metabolites. Among those substances, characteristic marker compounds have to be identified for a confident detection of mold fungi in varying surroundings. The analytical determination is usually performed through passive sampling with solid phase microextraction, gas chromatographic separation, and detection by electron ionization mass spectrometry (EI-MS), which often does not allow a confident determination due to the absence of molecular ions. An alternative is GC-APCI-MS, generally, allowing the determination of protonated molecular ions. Commercial atmospheric pressure chemical ionization (APCI) sources are based on corona discharges, which are often unspecific due to the occurrence of several side reactions and produce complex product ion spectra. To overcome this issue, an APCI source based on soft X-radiation is used here. This source facilitates a more specific ionization by proton transfer reactions only. In the first part, the APCI source is characterized with representative volatile fungus metabolites. Depending on the proton affinity of the metabolites, the limits of detection are up to 2 orders of magnitude below those of EI-MS. In the second part, the volatile metabolites of the mold fungus species Aspergillus, Alternaria, Fusarium, and Penicillium are investigated. In total, 86 compounds were found with GC-EI/APCI-MS. The metabolites identified belong to the substance classes of alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, terpenes, and sesquiterpenes. In addition to substances unspecific for the individual fungus species, characteristic patterns of metabolites, allowing their confident discrimination, were found for each of the 4 fungus species. Sixty-seven of the 86 metabolites are detected by X-ray-based APCI-MS alone. The discrimination of the fungus species based on these metabolites alone was possible. Therefore, APCI-MS in combination with collision induced dissociation alone could be used as a supervision method for the detection of mold fungi. KW - APCI KW - gas chromatography KW - mass spectrometry KW - mold fungi KW - soft X-radiation KW - volatile organic compounds Y1 - 2018 U6 - https://doi.org/10.1002/jms.4210 SN - 1076-5174 SN - 1096-9888 VL - 53 IS - 10 SP - 911 EP - 920 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Riebe, Daniel A1 - Erler, Alexander A1 - Brinkmann, Pia A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Gebbers, Robin T1 - Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture JF - Sensors N2 - The lack of soil data, which are relevant, reliable, affordable, immediately available, and sufficiently detailed, is still a significant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within fields, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, different calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural fields in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The first method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both fields. The second univariate model derived the calibration from the reference analytics of all samples from one field. The prediction is validated by LIBS data of the second field. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the first field are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the first field and independently on the second field data. The second univariate method yielded better calibration and prediction results compared to the first method, since matrix effects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method. KW - laser-induced breakdown spectroscopy KW - LIBS KW - proximal soil sensing KW - soil nutrients KW - elemental composition Y1 - 2019 U6 - https://doi.org/10.3390/s19235244 SN - 1424-8220 VL - 19 IS - 23 PB - MDPI CY - Basel ER - TY - GEN A1 - Wolff, Christian Michael A1 - Canil, Laura A1 - Rehermann, Carolin A1 - Nguyen, Ngoc Linh A1 - Zu, Fengshuo A1 - Ralaiarisoa, Maryline A1 - Caprioglio, Pietro A1 - Fiedler, Lukas A1 - Stolterfoht, Martin A1 - Kogikoski, Junior, Sergio A1 - Bald, Ilko A1 - Koch, Norbert A1 - Unger, Eva L. A1 - Dittrich, Thomas A1 - Abate, Antonio A1 - Neher, Dieter T1 - Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445−1456) T2 - ACS nano Y1 - 2020 U6 - https://doi.org/10.1021/acsnano.0c08081 SN - 1936-0851 SN - 1936-086X VL - 14 IS - 11 SP - 16156 EP - 16156 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Wolff, Christian Michael A1 - Caprioglio, Pietro A1 - Stolterfoht, Martin A1 - Neher, Dieter T1 - Nonradiative Recombination in Perovskite Solar Cells BT - the Role of Interfaces JF - Advanced materials N2 - Perovskite solar cells combine high carrier mobilities with long carrier lifetimes and high radiative efficiencies. Despite this, full devices suffer from significant nonradiative recombination losses, limiting their V-OC to values well below the Shockley-Queisser limit. Here, recent advances in understanding nonradiative recombination in perovskite solar cells from picoseconds to steady state are presented, with an emphasis on the interfaces between the perovskite absorber and the charge transport layers. Quantification of the quasi-Fermi level splitting in perovskite films with and without attached transport layers allows to identify the origin of nonradiative recombination, and to explain the V-OC of operational devices. These measurements prove that in state-of-the-art solar cells, nonradiative recombination at the interfaces between the perovskite and the transport layers is more important than processes in the bulk or at grain boundaries. Optical pump-probe techniques give complementary access to the interfacial recombination pathways and provide quantitative information on transfer rates and recombination velocities. Promising optimization strategies are also highlighted, in particular in view of the role of energy level alignment and the importance of surface passivation. Recent record perovskite solar cells with low nonradiative losses are presented where interfacial recombination is effectively overcome-paving the way to the thermodynamic efficiency limit. KW - interfacial recombination KW - open-circuit voltage KW - perovskite solar cells KW - photoluminescence Y1 - 2019 U6 - https://doi.org/10.1002/adma.201902762 SN - 0935-9648 SN - 1521-4095 VL - 31 IS - 52 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Saliba, Michael A1 - Correa-Baena, Juan-Pablo A1 - Wolff, Christian Michael A1 - Stolterfoht, Martin A1 - Phung, Thi Thuy Nga A1 - Albrecht, Steve A1 - Neher, Dieter A1 - Abate, Antonio T1 - How to Make over 20% Efficient Perovskite Solar Cells in Regular (n-i-p) and Inverted (p-i-n) Architectures JF - Chemistry of materials : a publication of the American Chemical Society N2 - Perovskite solar cells (PSCs) are currently one of the most promising photovoltaic technologies for highly efficient and cost-effective solar energy production. In only a few years, an unprecedented progression of preparation procedures and material compositions delivered lab-scale devices that have now reached record power conversion efficiencies (PCEs) higher than 20%, competing with most established solar cell materials such as silicon, CIGS, and CdTe. However, despite a large number of researchers currently involved in this topic, only a few groups in the world can reproduce >20% efficiencies on a regular n-i-p architecture. In this work, we present detailed protocols for preparing PSCs in regular (n-i-p) and inverted (p-i-n) architectures with >= 20% PCE. We aim to provide a comprehensive, reproducible description of our device fabrication , protocols. We encourage the practice of reporting detailed and transparent protocols that can be more easily reproduced by other laboratories. A better reporting standard may, in turn, accelerate the development of perovskite solar cells and related research fields. Y1 - 2018 U6 - https://doi.org/10.1021/acs.chemmater.8b00136 SN - 0897-4756 SN - 1520-5002 VL - 30 IS - 13 SP - 4193 EP - 4201 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Cyclazines-structure and aromaticity or antiaromaticity on the magnetic criterion JF - European journal of organic chemistry N2 - Structure and spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of all ten cycl[2.2.2]azine to cycl[4.4.4]azine, hetero-analogues and the corresponding hydrocarbons have been calculated at the B3LYP/6-311G(d,p) theory level using the GIAO perturbation method and employing the nucleus independent chemical shift (NICS) concept. The TSNMRS values (actually, the ring current effect as measurable in H-1 NMR spectroscopy) are visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction, and employed to readily qualify and quantify the degree of (anti)aromaticity. Results are confirmed by NMR [delta(H-1)/ppm, delta(N-15)/ppm] and geometry (planar, twisted, bow-shaped) data. The cyclazines N[2.2.2](-) up to N[2.4.4](-) are planar or at most slightly bowl-shaped and, due to coherent peripheral ring currents (except in N[2.3.3](-), N[2.3.4], N[3.3.4](+) and N[2.4.4](+)), develop aromaticity or anti-aromaticity of the whole molecules dependent on the number of peripheral conjugated pi electrons. The cyclazines N[2.3.3](-), N[2.3.4], N[3.3.4](+) and N[2.4.4](+) develop two ring currents of different direction within the same molecule, in which the dominating ring current proves to be paratropic (in N[3.3.4](+) diatropic) including the nodal N p(z) lone pair into the conjugation. The residual cyclazines N[3.4.4], N[4.4.4](-) and N[4.4.4](+) are heavily twisted and, therefore, are not developing peripheral or diverse ring currents. The TSNMRS information about cyclazines and the parent tricyclic annulene analogues is congruent subject to structure and number of peripheral or internal conjugated pi electrons, the corresponding (anti)aromaticity is in unequivocal accordance with Huckel's rule. KW - Aromaticity KW - Cyclazines KW - NMR spectroscopy KW - Peripheral ring current Y1 - 2022 U6 - https://doi.org/10.1002/ejoc.202101362 SN - 1434-193X SN - 1099-0690 VL - 2022 IS - 8 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Chipanina, Nina N. A1 - Oznobikhina, Larisa P. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu. T1 - Synthesis and Conformational Analysis of 3-Methyl-3-silatetrahydropyran by GED, FTIR, NMR, and Theoretical Calculations: Comparative Analysis of 1-Hetero-3-methyl-3-silacyclohexanes JF - The journal of organic chemistry N2 - 3-Methyl-3-silatetrahydropyran 1 was synthesized and its molecular structure and conformational behavior was studied by gas-phase electron diffraction (GED), FTIR, low temperature H-1 and C-13 NMR spectroscopy, and by theoretical calculations (DFT, MP2). Two conformers; 1-ax and 1-eq; were located on the potential energy Surface. In the gas phase; a slight predominance of the axial conformer was determined, with the ratio 1-ax:1-eq = 54(9):46(9) (from GED) or 53:47 or 61;39 (from IR). In solution, LT NMR spectroscopy at 103 K gives the ratio 1-ax:1-eq = 35:65 (-Delta G(103)degrees = 0.13 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the corresponding solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of 3-methyl-3-silatettahydropyran in the gas phase and in solution. Comparative analysis of the effect of heteroatom in 1-hetero-3-methyl-3-silacyclohexanes on the structure, stereoelectronic interactions, and relative energies of the conformers is done. Y1 - 2015 U6 - https://doi.org/10.1021/acs.joc.5b02355 SN - 0022-3263 VL - 80 IS - 24 SP - 12492 EP - 12500 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Balci, K. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Collier, W. B. A1 - Stricker, M. C. A1 - Stover, D. D. A1 - Ritzhaupt, G. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - The effects of conformation and zwitterionic tautomerism on the structural and vibrational spectral data of anserine JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - In this study, the stable conformers of neutral anserine were searched by molecular dynamics simulations and energy minimization calculations using the MM2 force field. Thermochemical calculations at B3LYP/6-31G(d) level of theory followed these preliminary calculations. The results confirmed that neutral anserine has quite a flexible structure and many stable gauche and trans conformers at room temperature. Nevertheless, two are considerably more favourable in energy than the others and expected to dominate the gas-phase and matrix IR spectra of the molecule. The corresponding structural and vibrational spectral data for these two conformers of neutral anserine, whose relative stabilities were also examined by high-accuracy energy calculations carried out using G3MP2B3 method, and for the most stable conformer of anserine in zwitterion form were calculated at B3LYP/6-311++G(d,p) level of theory. The calculated harmonic force constants were refined using the Scaled Quantum Mechanical Force Field (SQM-FF) method and then used to produce the refined wavenumbers, potential energy distributions (PEDs) and IR and Raman intensities. These refined data together with the scaled harmonic wavenumbers obtained using another method, Dual Scale factors (DS), enabled us to correctly analyse the observed IR and Raman spectra of anserine and revealed the effects of conformation and zwitterionic tautomerism on its structural and vibrational spectral data. (C) 2016 Elsevier B.V. All rights reserved. KW - Anserine KW - Matrix IR spectrum KW - Tautomerism KW - SQM-FF KW - Dual scale factors Y1 - 2016 U6 - https://doi.org/10.1016/j.vibspec.2016.08.003 SN - 0924-2031 SN - 1873-3697 VL - 86 SP - 277 EP - 289 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wentrup, Curt A1 - Koch, Rainer A1 - Kleinpeter, Erich T1 - Twisted C=C Double Bonds with Very Low Rotational Barriers in Dioxanediones and Isoxazolones Determined by Low-Temperature Dynamic NMR Spectroscopy and Computational Chemistry JF - European journal of organic chemistry KW - NMR spectroscopy KW - Twisted double bonds KW - Push-pull effect KW - Density functional calculations Y1 - 2016 U6 - https://doi.org/10.1002/ejoc.201600931 SN - 1434-193X SN - 1099-0690 SP - 4985 EP - 4990 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The 13 C chemical shift and the anisotropy effect of the carbene electron-deficient centre BT - simple means to characterize the electron distribution of carbenes JF - Magnetic resonance in chemistry N2 - Both the C-13 chemical shift and the calculated anisotropy effect (spatial magnetic properties) of the electron-deficient centre of stable, crystalline, and structurally characterized carbenes have been employed to unequivocally characterize potential resonance contributors to the present mesomerism (carbene, ylide, betaine, and zwitter ion) and to determine quantitatively the electron deficiency of the corresponding carbene carbon atom. Prior to that, both structures and C-13 chemical shifts were calculated and compared with the experimental delta(C-13)/ppm values and geometry parameters (as a quality criterion for obtained structures). KW - C-13 chemical shift KW - carbenes KW - zwitterions KW - carbene electron deficiency KW - nucleus-independent chemical shifts (NICS) KW - through space NMR shieldings KW - (TSNMRS) Y1 - 2019 U6 - https://doi.org/10.1002/mrc.4979 SN - 0749-1581 SN - 1097-458X VL - 58 IS - 3 SP - 280 EP - 292 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Kolocouris, Antonios A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Stylianakis, Ioannis T1 - 2-Substituted and 2,2-disubstituted adamantane derivatives as models for studying substituent chemical shifts and C-H-ax center dot center dot center dot Y-ax cyclohexane contacts-results from experimental and theoretical NMR spectroscopic chemical shifts and DFT structures JF - Tetrahedron N2 - The complete H-1 and C-13 NMR chemical shifts assignment for various 2-substituted and 2,2-disubstituted adamantane derivatives 1-38 in CDCl3 solution was realized on the basis of NMR experiments combined with chemical structure information and DFT-GIAO (B3LYP/6-31+G(d,p)-GIAO) calculations of chemical shifts in solution. Substituent-induced C-13 NMR chemical shifts (SCS) are discussed. C-H-ax center dot center dot center dot Y-ax contacts are a textbook prototype of steric hindrance in organic chemistry. The nature of these contacts will be further investigated in this work on basis of new adamantane derivatives, which are substituted at C-2 to provide models for 1,4-C-H-ax center dot center dot center dot Y-ax and 1,5-C-H-ax center dot center dot center dot Y-ax contacts. The B3LYP/6-31+G(d,p) calculations predicted the presence of NBO hyperconjugative attractive interactions between C-H-ax and Y-ax groups along C-H-ax center dot center dot center dot Y-ax contacts. The H-1 NMR signal separation, Delta delta(gamma-CH2), reflects the strength of the H-bonded C-H-ax center dot center dot center dot Y-ax contact. (C) 2015 Elsevier Ltd. All rights reserved. KW - 2-Substituted adamantane derivatives KW - 2,2-Disubstituted adamantane derivatives KW - H-1 NMR KW - C-13 NMR KW - B3LYP/6-31+G(d,p) calculations KW - GIAO calculations KW - Substituent chemical shifts Y1 - 2015 U6 - https://doi.org/10.1016/j.tet.2015.01.044 SN - 0040-4020 VL - 71 IS - 16 SP - 2463 EP - 2481 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich ED - Webb, GA T1 - Quantification and visualization of the anisotropy effect in NMR spectroscopy by through-space NMR shieldings JF - Annual reports on NMR spectroscopy JF - Annual Reports on NMR Spectroscopy N2 - The anisotropy effect of functional groups (respectively the ring-current effect of aryl moieties) in H-1 NMR spectra has been computed as spatial NICS (through-space NMR chemical shieldings) and visualized by iso-chemical-shielding surfaces of various size and low(high) field direction. Hereby, the anisotropy/ring-current effect, which proves to be the molecular response property of spatial NICS, can be quantified and can be readily employed for assignment purposes in proton NMR spectroscopy-characteristic examples of stereochemistry and position assignments (the latter in supramolecular structures) will be given. In addition, anisotropy/ring-current effects in H-1 NMR spectra can be quantitatively separated from the second dominant structural effect in proton NMR spectra, the steric compression effect, pointing into the reverse direction, and the ring-current effect, by far the strongest anisotropy effect, can be impressively employed to visualize and quantify (anti) aromaticity and to clear up standing physical-organic phenomena as are pseudo-, spherical, captodative, homo-and chelatoaromaticity, to characterize the pi-electronic structure of, for example, fulvenes, fulvalenes, annulenes or fullerenes and to differentiate aromatic and quinonoid structures. KW - Through-space NMR shielding (TSNMRS) KW - Anisotropy effect KW - Stereochemistry KW - Ring-current effect KW - Aromatic or quinonoid KW - Aromaticity KW - Chelatoaromaticity KW - Binding pocket position KW - Supramolecular compounds KW - Diastereomers assignment Y1 - 2014 SN - 978-0-12-800184-4 U6 - https://doi.org/10.1016/B978-0-12-800184-4.00003-5 SN - 0066-4103 VL - 82 SP - 115 EP - 166 PB - Elsevier CY - San Diego ER -