Refine
Year of publication
Document Type
- Article (301)
- Monograph/Edited Volume (3)
- Other (3)
- Conference Proceeding (1)
- Part of Periodical (1)
- Postprint (1)
- Review (1)
Keywords
- Conformational analysis (14)
- NMR spectroscopy (9)
- conformational analysis (9)
- NICS (8)
- Theoretical calculations (8)
- Through-space NMR shieldings (TSNMRS) (8)
- Anisotropy effect (7)
- Ring current effect (7)
- Aromaticity (6)
- NMR (6)
- DFT calculations (5)
- Dynamic NMR (5)
- Quantum chemical calculations (5)
- quantum chemical calculations (5)
- ICSS (4)
- TSNMRS (4)
- Conformational equilibrium (3)
- GIAO (3)
- Gas phase electron diffraction (3)
- NBO analysis (3)
- dynamic NMR (3)
- (Anti)aromaticity (2)
- Anisotropic effect (2)
- Barrier to ring inversion (2)
- Chelatoaromaticity (2)
- DFT (2)
- Density functional calculations (2)
- Dynamic NMR spectroscopy (2)
- H-1 NMR (2)
- Iso-chemical-shielding surfaces (ICSS) (2)
- NHCs (2)
- Push-pull character (2)
- Push-pull effect (2)
- Stereochemistry (2)
- Steric effect (2)
- Taft equation (2)
- anisotropic effects (2)
- aromaticity (2)
- low-temperature NMR spectroscopy (2)
- modified Mannich reaction (2)
- shieldings (TSNMRS) (2)
- (1)H NMR (1)
- (13)C NMR (1)
- (TSNMRS) (1)
- 1,1-dimethyl-1,2,3,4-tetrahydrosiline (1)
- 1,2,4-Dithiazole (1)
- 1,2-Dithiole (1)
- 1,2-diboretane-3-ylidene (1)
- 1,3-Azasilinanes (1)
- 1,3-Dimethyl-3-phenyl-1,3-azasilinane (1)
- 1,3-Oxasilinanes (1)
- 1,4,2-Oxazasilinanes (1)
- 1-(Dimethylamino)-1-phenyl-1-silacyclohexane (1)
- 1-Methylthio-1-phenyl-1-silacyclohexane (1)
- 2 (1)
- 2,2-Disubstituted adamantane derivatives (1)
- 2-Alkylidene-4-oxothiazolidine (1)
- 2-Substituted adamantane derivatives (1)
- 3,4-Dihydroisoquinoline (1)
- 3,4-dihydro-2H-pyran (1)
- 3,4-dihydro-2H-thiopyran (1)
- 3-Fluoro-3-methyl-3-silatetrahydropyran (1)
- 3-Silatetrahydropyrans (1)
- 3-silathianes (1)
- 3c,2e-bonding (1)
- 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline (1)
- 4-Oxothiazolidine (1)
- 4-Substituted cyclohexanones (1)
- 4-methylene-cyclohexyl pivalate (1)
- 4-silapiperidines (1)
- 4-silathianes (1)
- 6-disilamorpholines (1)
- 9-Arylfluorenes (1)
- A-values of COOAr on cyclohexane (1)
- ALTONA equation (1)
- ATR-FTIR (1)
- Ab initio MO computations (1)
- Additivity of conformational energies (1)
- Aminonaphthol (1)
- Aminonaphthols (1)
- Annelation effect (1)
- Anserine (1)
- Anti-aromaticity (1)
- Anticancer (1)
- Antileishmanial (1)
- Antiplasmodial (1)
- Aromatic or quinonoid (1)
- Assignment of stereochemistry (1)
- Asteraceae (1)
- B,N heterocycles (1)
- B3LYP/6-31+G(d,p) calculations (1)
- B3LYP/6-311++G** (1)
- Barrier to rotation about C-N bond (1)
- Benzazepine (1)
- Benzenoid structure (1)
- Benzenoid structures (1)
- Benzoic acid esters (1)
- Benzyne-allene or cumulene-like structure (1)
- Betaines (1)
- Binding pocket position (1)
- C-13 (1)
- C-13 NMR (1)
- C-13 NMR spectroscopy (1)
- C-13 chemical shift (1)
- C-13 chemical shift difference Delta delta(C C) (1)
- CAACs (1)
- CH center dot center dot center dot O hydrogen bonds (1)
- Carbamoyl tetrazoles (1)
- Carbene or zwitterions (1)
- Carbenes (1)
- Carbohydrates (1)
- Carvotacetones (1)
- Chiral dopants (1)
- Condensed thiazolidines (1)
- Conformation analysis (1)
- Conformational equilibria (1)
- Copper Metal Complexes (1)
- Cyanine/merocyanine-like structures (1)
- Cyclazines (1)
- Cyclobutylcarbene (1)
- Cyclohexyl esters (1)
- DFT and MP2 calculations (1)
- DFT and MP2 simulation (1)
- DFT calculation (1)
- DFT structural study (1)
- DFT theoretical calculations (1)
- Dative vs. coordinative NHC -> BR3 bond (1)
- Dehydro[n]annulenes (1)
- Diastereomers assignment (1)
- Diastereoselectivity (1)
- Dual Scale Factors (1)
- Dual scale factors (1)
- Dynamic H-1-NMR (1)
- Electrostatic effects (1)
- F-19 (1)
- GIAO calculations (1)
- Gas-phase electron diffraction (1)
- Glycol podands (1)
- H-1 (1)
- H-1 NMR spectroscopy (1)
- H-1-NMR (1)
- Hammett-Brown plots (1)
- Hemiporphyrazines (1)
- Heterocycles (1)
- IR and Raman spectra (1)
- Iso-chemical shielding surfaces (ICSS) (1)
- Isothiocyanic acid (1)
- Low temperature NMR spectroscopy (1)
- Low-temperature C-13 and Si-29 NMR (1)
- Low-temperature NMR (1)
- Low-temperature d-NMR (1)
- M062X/6-311G** calculations (1)
- MP2 (1)
- MP2 and CCSD(T) calculations (1)
- Matrix IR spectrum (1)
- Mesomeric equilibrium of carbene/zwitterion (1)
- Mesomerism (1)
- Modified Mannich reaction (1)
- Molecular dynamics (1)
- Multiple NHC(CAAC)-Boron bonds (1)
- N-acetyl glucosamine derivatives (1)
- N-unsubstituted (primary)S-thiocarbamates (1)
- N-unsubstituted(primary)O-thiocarbamates (1)
- NBO and STERIC analyses (1)
- NBO/NCS analysis (1)
- Naphthoxazines (1)
- Naphthoxazinoquinazolines (1)
- Naphthoxazinoquinazolinones (1)
- Occupation quotient pi*/pi (1)
- Peripheral ring current (1)
- Polar effect (1)
- Polar substituent constant (1)
- Porphyrins (1)
- Push-pull alkynes (1)
- Push-pull allenes (1)
- Quantum Chemical Calculations (1)
- Quasi-aromaticity (1)
- Quinazolines (1)
- Quinonoid structure (1)
- Quotient method (1)
- RA-intramolecular hydrogen bond (1)
- Rearrangement to trithiaazapentalene (1)
- Residual dipolar couplings (1)
- Ring-current effect (1)
- SQM FF (1)
- SQM-FF (1)
- Salicylic acid (1)
- Silacyclohexanes (1)
- Silaheterocyclohexanes (1)
- Silica sulfuric acid (1)
- Simulation of H-1 NMR spectra (1)
- Solid acid (1)
- Solvent effects (1)
- Solvent-free (1)
- Spatial NICS (1)
- Sphaeranthus bullatus (1)
- Steric effects (1)
- Steric hindrance (1)
- Steric substituent constant (1)
- Substituent chemical shifts (1)
- Substituent effects (1)
- Sulfoxide (1)
- Supramolecular compounds (1)
- Tautomerism (1)
- Tetraoxo[8]circulenes (1)
- Thienopyridine (1)
- Through -space NMR (1)
- Through-space NMR (1)
- Through-space NMR shielding (TSNMRS) (1)
- Trithiapentalene (1)
- Trough-space NMR shieldings (TSNMRS) (1)
- Twisted double bonds (1)
- Vinylogous N-acyliminium ion (1)
- X-ray analysis (1)
- X-ray structures (1)
- Y-aromaticity (1)
- Ylide (1)
- [4+2] cycloaddition (1)
- ab initio calculations (1)
- barrier to ring inversion (1)
- barrier to rotation about C-N bond (1)
- benzenoid structures (1)
- carbamoyl tetrazoles (1)
- carbene electron deficiency (1)
- carbenes (1)
- cis,cis-Tricyclo[5.3.0.0(2,6)]dec-3-enes (1)
- computational chemistry (1)
- conformational equilibrium (1)
- cyclic imines (1)
- cycloaddition (1)
- density functional calculations (1)
- dielectric spectroscopy (1)
- dynamic (1)
- dynamic NMR spectroscopy (1)
- endo-Mode cyclization (1)
- ephedrine/pseudoephedrine (1)
- exo-methylene conformational effect at cyclohexane (1)
- low temperature NMR spectroscopy (1)
- molecular structure (1)
- nucleus-independent chemical shift (1)
- nucleus-independent chemical shifts (NICS) (1)
- onformational analysis (1)
- ortho-quinone methide (o-QMs) (1)
- para-Nitro-pyridine N-oxides (1)
- pi interactions (1)
- pi-Electron delocalization (1)
- pi-Stacking (1)
- quantum mechanical calculations (1)
- quinoid structures (1)
- restricted N-S rotation (1)
- silacyclohexanes (1)
- silapiperidines (1)
- siloxanes (1)
- spectroscopy (1)
- sulfimides (1)
- sulfur heterocycles (1)
- through space NMR shieldings (1)
- zwitterions (1)
Through the reactions of 1- or 2-naphthol and 4,5-dihydro-3H-benz[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine, new aminonaphthol derivatives were prepared. The syntheses were extended by using N-containing naphthol analogues such as 5-hydroxyisoquinoline and 6-hydroxyquinoline. The ring closures of the novel bifunctional compounds were also achieved, resulting in new naphth[2,1-e][1,3]oxazines, naphth[1,2-e][1,3]oxazines, isoquinolino[5,6-e][1,3]oxazines and quinolino[5,6-e][1,3]oxazines. H-1 NMR spectra of the target heterocycles 16, 20 and 21 were sufficiently resolved to indentify the present stereochemistry; therefore, beside computed structures, spatial experimental (dipolar coupling-NOE) and computed (ring current effect of the naphthyl moiety-TSNMRS) NMR studies were employed. The studied heterocycles exist exclusively as S(14b),R(N), R(14b),S(N), and S(16b)S(N) isomers, respectively. The flexible moieties of the studied compounds prefer. (C) 2016 Elsevier Ltd. All rights reserved.
A new series of unsubstituted and substituted pyridinium salts bearing a 4-oxothiazolidinyl moiety has been prepared by an efficient rearrangement of 2-(1-bromoalkylidene)thiazolidin-4-ones. The process in based on three steps, namely carbon-bromine cleavage, bromine transfer, and substitution, each induced by pyridine or its derivatives, acting as base and reactant.
Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine
(2012)
On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from s and p bonds by the natural chemical shieldingnatural bond orbital (NCSNBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity.
Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
Structures of a series of push-pull 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives were optimized at the B3LYP/6-31G(d) level of theory in the gas phase and discussed with respect to configurational and conformational stability. Employing the GIAO method, C-13 NMR chemical shifts of the C-2, C-2', C-4 and C-5 atoms were calculated at the same level of theory in the gas phase and with inclusion of solvent, and compared with experimental data. Push-pull effect of all compounds was quantified by means of the quotient pi*/pi, length of the partial double bond, C-13 NMR chemical shift difference (Delta delta(C=C)) and H-1 NMR chemical shifts of olefinic protons. The effect of bromine on donating and accepting ability of other substituents of the push- pull C=C double bond is discussed, too.
The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy)ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople-style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major contribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibrations to conformation, substitution and dimerization were discussed.
The theoretically possible stable conformers of free mn-15S2O3 maleonitrile-dithiacrown ether molecule were searched by means of a conformational study which consists of molecular dynamics and energy minimization calculations performed with MM2 force field and successive geometry optimization + frequency calculations performed first at B3LYP/3- 21G and then at B3LYP/6-31G(d) levels of theory. The obtained calculation results have clearly indicated that the free molecule in electronic ground state is very flexible and accordingly has many possible stable conformers of different conformational properties at room temperature; among them, the one having a macrocyclic ring structure in which all of the ether units oriented toward the center of the ring was determined the energetically most preferable conformer. In addition, the equilibrium geometrical parameters, vibrational normal modes and associated IR spectral data of the determined most stable three conformers of the molecule were calculated at B3LYP/6-31+G(d) and B3LYP/6-31++G(d,p) levels of theory. A successful assignment of the fundamental bands observed in the recorded experimental solid phase and solution phase IR spectra of the molecule was achieved in the light of the theoretical data obtained from these DFT calculations. To fit the calculated harmonic wavenumbers to the experimental ones, two different scaling procedures, referred to as "Scaled Quantum Mechanical Force Field (SQM FF) methodology" and "Scaling wavenumbers with empirical dual scale factors", were proceeded independently.
A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data.
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.
BAIER, D.; SOYEZ, K.: Dekontamination von Altholz ; BAIER, D. et al.: Untersuchungen zur Kompostierbarkeit von paraffinbeschichteten Verpackungsmaterialien ; KAISER, J.; SOYEZ, K.: Zum Wasser- und Wärmehaushalt des Intensivrotteprozesses der mechanisch-biologischen Abfallbehandlung ; KAMM, B. et al.: Green Biorefinery - European Network for the Implementation of Biorefineries (NIB) ; KAMM, B. et al.: Grüne Bioraffinerie Brandenburg ; KOLLER, M.; HERMANN, T.: Entscheidungshilfen für die ökologische Optimierung der Entsorgung häuslicher Restabfälle ; SCHMEER, E.: Solarthermie 2000 ; SCHMEER, E.: Forschungs- und Demonstrationsanlage zur Photovoltaik ; SOYEZ, K. et al.: Verbundvorhaben "Mechanisch-biologische Restabfallbehandlung" ; STARKE, I. et al.: Carbohydrates as raw material from a Green BioRefinery