@article{GlatzelBadiPaechetal.2010, author = {Glatzel, Stefan and Badi, Nezha and Paech, Michael and Laschewsky, Andr{\´e} and Lutz, Jean-Francois}, title = {Well-defined synthetic polymers with a protein-like gelation behavior in water}, issn = {1359-7345}, doi = {10.1039/C0cc00038h}, year = {2010}, abstract = {Homopolymers of N-acryloyl glycinamide were prepared by reversible addition-fragmentation chain transfer polymerization in water. The formed macromolecules exhibit strong polymer-polymer interactions in aqueous milieu and therefore form thermoreversible physical hydrogels in pure water, physiological buffer or cell medium.}, language = {en} } @article{XieJelicicWangetal.2010, author = {Xie, Zai-Lai and Jelicic, Aleksandra and Wang, Feipeng and Rabu, Pierre and Friedrich, Alwin and Beuermann, Sabine and Taubert, Andreas}, title = {Transparent, flexible, and paramagnetic ionogels based on PMMA and the iron-based ionic liquid 1-butyl-3- methylimidazolium tetrachloroferrate(III) [Bmim][FeCl4]}, issn = {0959-9428}, doi = {10.1039/C0jm01733g}, year = {2010}, abstract = {The iron-containing ionic liquid (IL) 1-butyl-3-methylimidazolium tetrachloroferrate(III) [Bmim][FeCl4] has been used as a building block in the synthesis of transparent, ion-conducting, and paramagnetic ionogels. UV/Vis spectroscopy shows that the coordination around the Fe(III) ion does slightly change upon incorporation of the IL into PMMA. The thermal stability of the PMMA increases significantly with IL incorporation. In particular, the onset weight loss observed at ca. 265 degrees C for pure PMMA is completely suppressed. The ionic conductivity shows a strong temperature dependence and increases with increasing IL weight fractions. The magnetic properties are similar to those reported for the pure IL and are not affected by the incorporation into the PMMA matrix. The resulting ionogel is thus an interesting prototype for soft, flexible, and transparent materials combining the mechanical properties of the matrix with the functionality of the metal-containing IL, such as magnetism.}, language = {en} } @article{TremblayKrauseKlamrothetal.2010, author = {Tremblay, Jean Christophe and Krause, Pascal and Klamroth, Tillmann and Saalfrank, Peter}, title = {Time-dependent response of dissipative electron systems}, issn = {1050-2947}, doi = {10.1103/Physreva.81.063420}, year = {2010}, abstract = {We present a systematic study of the influence of energy and phase relaxation on dynamic polarizability simulations in the linear response regime. The nonperturbative approach is based on explicit electron dynamics using short laser pulses of low intensities. To include environmental effects on the property calculation, we use the time- dependent configuration-interaction method in its reduced density matrix formulation. Both energy dissipation and nonlocal pure dephasing are included. The explicit treatment of time-resolved electron dynamics gives access to the phase shift between the electric field and the induced dipole moment, which can be used to define a useful uncertainty measure for the dynamic polarizability. The nonperturbative treatment is compared to perturbation theory expressions, as applied to a simple model system, the rigid H-2 molecule. It is shown that both approaches are equivalent for low field intensities, but the time-dependent treatment provides complementary information on the phase of the induced dipole moment, which allows for the definition of an uncertainty associated with the computation of the dynamic polarizability in the linear response regime.}, language = {en} } @article{AdelsbergerKulkarniJainetal.2010, author = {Adelsberger, Joseph and Kulkarni, Amit and Jain, Abhinav and Wang, Weinan and Bivigou Koumba, Achille Mayelle and Busch, Peter and Pipich, Vitaliy and Holderer, Olaf and Hellweg, Thomas and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.}, title = {Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response}, issn = {0024-9297}, doi = {10.1021/Ma902714p}, year = {2010}, abstract = {We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments.}, language = {en} } @article{BivigouKoumbaGoernitzLaschewskyetal.2010, author = {Bivigou Koumba, Achille Mayelle and Goernitz, Eckhard and Laschewsky, Andr{\´e} and M{\"u}ller-Buschbaum, Peter and Papadakis, Christine M.}, title = {Thermoresponsive amphiphilic symmetrical triblock copolymers with a hydrophilic middle block made of poly(N- isopropylacrylamide) : synthesis, self-organization, and hydrogel formation}, issn = {0303-402X}, doi = {10.1007/s00396-009-2179-9}, year = {2010}, abstract = {Several series of symmetrical triblock copolymers were synthesized by the reversible addition fragmentation chain transfer method. They consist of a long block of poly(N-isopropylacrylamide) as hydrophilic, thermoresponsive middle block, which is end-capped by two small strongly hydrophobic blocks made from five different vinyl polymers. The association of the amphiphilic polymers was studied in dilute and concentrated aqueous solution. The polymer micelles found at low concentrations form hydrogels at high concentrations, typically above 30-35 wt.\%. Hydrogel formation and the thermosensitive rheological behavior were studied exemplarily for copolymers with hydrophobic blocks of polystyrene, poly(2-ethylhexyl acrylate), and poly(n-octadecyl acrylate). All systems exhibited a cloud point around 30 A degrees C. Heating beyond the cloud point initially favors hydrogel formation but continued heating results in macroscopic phase separation. The rheological behavior suggests that the copolymers associate into flower-like micelles, with only a small share of polymers that bridge the micelles and act as physical cross-linkers, even at high concentrations.}, language = {en} } @article{SchwarzSieversBodenthinetal.2010, author = {Schwarz, Guntram and Sievers, Torsten K. and Bodenthin, Yves and Hasslauer, Ires and Geue, Thomas and Koetz, Joachim and Kurth, Dirk G.}, title = {The structure of metallo-supramolecular polyelectrolytes in solution and on surfaces}, issn = {0959-9428}, doi = {10.1039/B926783b}, year = {2010}, abstract = {Metal ion induced self-assembly of the rigid ligand 1,4-bis(2,2':6',2 ''-terpyridine- 4'-yl) benzene (1) with Fe(II), Co(II), Ni(II) and Zn(II) acetate in aqueous solution results in extended, rigid- rod like metallosupramolecular coordination polyelectrolytes (MEPE-1). Under the current experimental conditions the molar masses range from 1000 g mol(-1) up to 500 000 g mol(-1). The molar mass depends on concentration, stoichiometry, metal-ion and time. In addition, we present viscosity measurements, small angle neutron scattering and AFM data. We introduce a protocol to precisely control the stoichiometry during self-assembly using conductometry. The protocol can be used with different terpyridine ligands and the above-mentioned metal ions and is of paramount importance to obtain meaningful and reproducible results. As a control experiment we studied the mononuclear 4'- (phenyl)2,2':6',2 ''-terpyridine (3) complex with Ni(II) and Zn(II) and the flexible ligand 1,3- bis[4'-oxa(2,2': 6',2 ''-terpyridinyl)] propane (2) with Ni(II) acetate (Ni-MEPE-2). This ligand does not form extended macroassemblies but likely ring-like structures with 3 to 4 repeat units. Through spin- coating of Ni-MEPE-1 on a solid surface we can image the MEPEs in real space by AFM. SANS measurements of Fe-MEPE-1 verify the extended rigid-rod type structure of the MEPEs in aqueous solution.}, language = {en} } @article{SchmidtWernerKellingetal.2010, author = {Schmidt, Bernd and Werner, Frank and Kelling, Alexandra and Schilde, Uwe}, title = {The reaction of 3,4-dihydro-2H-pyran with oxalyl chloride : formation and crystal structure analysis of an unexpected bicyclic product}, issn = {0022-152X}, year = {2010}, abstract = {3,4-Dihydro-2-H-pyran and oxalyl chloride react, depending on the conditions, to keto esters, a pyran-3- carboxylic acid or derivatives thereof, or to an hitherto unknown bicyclic acetal containing a vinyl chloride moiety. The structure of the latter product has been unambiguously elucidated by single-crystal X-ray structure analysis. A mechanism for its formation is proposed.}, language = {en} } @article{StrehmelRexhausenStrauchetal.2010, author = {Strehmel, Veronika and Rexhausen, Hans and Strauch, Peter and Strehmer, Bernd}, title = {Temperature dependence of interactions between stable piperidine-1-yloxyl derivatives and a semicrystalline ionic liquid}, issn = {1439-4235}, doi = {10.1002/cphc.200900977}, year = {2010}, abstract = {The stable 2,2,6,6-tetramethylpiperidine-1-yloxyl and its derivatives with hydrogen-bond-forming (-OH, -OSO3H), anionic (-OSO3- bearing K+ or [K(18-crown-6)](+) as counter ion), or cationic (-N+-(CH3)(3) bearing I-, BF4-, PF6- or N- (SO2CF3)(2) as counter ion) substituents are investigated in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide over a wide temperature range. The temperature dependence of the viscosity of the ionic liquid is well described by the Vogel-Fulcher-Tammann equation. Interestingly, the temperature dependence of the rotational correlation time of the spin probes substituted with either a hydrogen-bond-forming group or an ionic substituent can be described using the Stokes-Einstein equation. In contrast, the temperature dependence of the rotational correlation time of the spin probe without an additional substituent at the 4-position to the nitroxyl group does not follow this trend. The activation energy for the mobility of the unsubstituted spin probe, determined from an Arrhenius plot of the spin-probe mobility in the ionic liquid above the melting temperature, is comparable with the activation energy for the viscous flow of the ionic liquid, but is higher for spin probes bearing an additional substituent at the 4-position. Quantum chemical calculations of the spin probes using the 6-31G+d method give information about the rotational volume of the spin probes and the spin density at the nitrogen atom of the radical structure as a function of the substituent at the spin probes in the presence and absence of a counter ion. The results of these calculations help in understanding the effect of the additional substituent on the experimentally determined isotropic hyperfine coupling constant.}, language = {en} } @article{SchwarzeMicklerDoscheetal.2010, author = {Schwarze, Thomas and Mickler, Wulfhard and Dosche, Carsten and Flehr, Roman and Klamroth, Tillmann and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Saalfrank, Peter and Holdt, Hans-J{\"u}rgen}, title = {Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination}, issn = {0947-6539}, doi = {10.1002/chem.200902281}, year = {2010}, abstract = {Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorophore probes 1-13 consist of a fluorophore group, in alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed, dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second. fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (E-Ox) through electron-withdrawing or -donating groups on the anthracene moiety regulates file thermodynamic driving force for oxidative PET (Delta G(PET)) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (Phi(f)), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.}, language = {en} } @article{SchwarzeMicklerDoscheetal.2010, author = {Schwarze, Thomas and Mickler, Wulfhard and Dosche, Carsten and Flehr, Roman and Klamroth, Tillmann and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Saalfrank, Peter and Holdt, Hans-J{\"u}rgen}, title = {Systematic investigation of photoinduced electron transfer controlled by internal charge transfer and its consequences for selective PdCl2 coordination}, issn = {0947-6539}, year = {2010}, abstract = {Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1-13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed a dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH2-bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (EOx) through electron-withdrawing or -donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (GPET) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (f), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.}, language = {en} } @article{SkrabaniavonBerlepschBoettcheretal.2010, author = {Skrabania, Katja and von Berlepsch, Hans and B{\"o}ttcher, Christoph and Laschewsky, Andr{\´e}}, title = {Synthesis of ternary, hydrophilic-lipophilic-fluorophilic block copolymers by consecutive RAFT polymerizations and their self-assembly into multicompartment micelles}, issn = {0024-9297}, doi = {10.1021/Ma901913f}, year = {2010}, abstract = {Linear amphiphilic diblock and ternary triblock copolymers were synthesized by the RAFT method in three Successive Steps, using oligo(ethylene oxide) monomethyl ether acrylate, butyl or 2-ethylhexyl acrylate, and 1H, 1H, 2H, 2H-perfluorodecyl acrylate. The diblock and the triblock copolymers, which consist of a hydrophilic, a lipophilic, and a fluorophilic block, self-assemble in water into spherical micellar aggregates. Imaging by cryogenic transmission electron microscopy (cryo-TEM) revealed that the cores of the micellar aggregates made from these "triphilic" copolymers undergo local phase separation to form various ultrastructures, which depend sensitivity on the given block sequence. While the sequence hydrophilic-lipophilic-fluorophilic resulted in multicompartment cores with core-shell-corona morphology, the sequence lipophilic-hydrophilic-fluorophilic provided new "patched double micelle" and larger "soccer ball" structures.}, language = {en} } @article{SengeShakerPinteaetal.2010, author = {Senge, Mathias O. and Shaker, Yasser M. and Pintea, Monica and Ryppa, Claudia and Hatscher, Sabine S. and Ryan, Aoife and Sergeeva, Yulia}, title = {Synthesis of meso-substituted ABCD-Type porphyrins by functionalization reactions}, issn = {1434-193X}, doi = {10.1002/ejoc.200901113}, year = {2010}, abstract = {Considerable progress has been made in recent years in the search for synthetic methods leading to functionalized porphyrins, especially for modification of either the beta- or meso positions. For the latter, total synthesis based on condensation methods or partial synthesis through functionalization of preformed porphyrin have emerged as possible methods. The increasing number of possible technical and medicinal applications for unsymmetrically meso-substituted porphyrins requires straightforward methods for the preparation of the so-called ABCD-porphyrins, i.e., porphyrins with up to four different meso substituents. Here, we describe new strategies for the synthesis of ABCD-type porphyrins based on porphyrin reactions with organolithium reagents and the use of Pd-catalyzed coupling reactions. With the whole repertoire of contemporary functionalization methods, a comprehensive analysis and comparison of the various strategies for A-, AB-, A(2)B-, ABC-, A(2)BC- and ABCD-type porphyrins is given. In addition, we report on the synthesis of new functionalized derivatives for some of these porphyrin classes. In practical terms and taking an applied-science- oriented approach, the synthesis of unsymmetrically meso-substituted porphyrins is best accomplished by a combination of well-developed condensation methods with subsequent functionalization. by organolithium compounds or transition-metal- catalyzed coupling protocols. The methods described are suitable for the preparation of porphyrins for many divergent applications ranging over amphiphilic porphyrins for photodynamic therapy, push-pull systems for optical applications and chiral systems useful in catalysis to donor-acceptor systems suitable for electron-transfer studies.}, language = {en} } @article{CywinskiIdzikCranfieldetal.2010, author = {Cywinski, Piotr J. and Idzik, Krzysztof R. and Cranfield, Charles G. and Beckert, Rainer and Mohr, Gerhard J.}, title = {Synthesis and sensing properties of a new carbazole fluorosensor for detection of abacavir}, issn = {1061-0278}, doi = {10.1080/10610278.2010.506541}, year = {2010}, abstract = {An abacavir-targeted fluorosensor based on the carbazole moiety has been synthesised and characterised. Recognition of abacavir is by base pairing between a uracil moiety present in the fluorosensor and the guanine moiety of abacavir. The fluorosensor exhibits five-fold quenching in the presence of 50M abacavir. Its sensitivity to abacavir is superior to that of other reverse transcriptase inhibitors: zidovudine, lamivudine and didanosine. Due to its high sensitivity, this fluorosensor has the potential to be used in multi-analyte array-based detection platforms as well as in microfluidics systems.}, language = {en} } @article{WangKaunePerlichetal.2010, author = {Wang, Weijia and Kaune, Gunar and Perlich, Jan and Paradakis, Christine M. and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Schlage, K. and R{\"o}hlsberger, Ralf and Roth, Stephan V. and Cubitt, Robert and M{\"u}ller-Buschbaum, Peter}, title = {Swelling and switching kinetics of gold coated end-capped poly(N-isopropylacrylamide) thin films}, issn = {0024-9297}, doi = {10.1021/Ma902637a}, year = {2010}, abstract = {Thin thermoresponsive hydrogel films of poly(N-isopropylacrylamide) end-capped with n-butyltrithiocarbonate(nbc- PNIPAM) oil si I icon supports with a gold layer on top, causing an asymmetric confinement, are investigated. For two different gold layer thicknesses (nominally 0.4 and 5 rim), the swelling and switching kinetics are probed with in situ neutron reflectivity. With a temperature jump from 23 to 40 degrees C the film is switched from a swollen into a collapsed state. For the thin gold layer this switching is faster as compared to the thick gold layer. The switching is a two-step process of water release and a subsequent structural relaxation. fit swelling and deswelling cycles, aging of the films is probed. After five cycles, the film exhibits enhanced water storage capacity. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that these gold coated nbc-PNIPAM films do not age with respect to the inner structure but slightly roughen at the gold surface. As revealed by atomic force microscopy, the morphology of the gold layer is changed by the water uptake and release.}, language = {en} } @article{SchweizerSchusterJungingeretal.2010, author = {Schweizer, S. and Schuster, T. and Junginger, Matthias and Siekmeyer, Gerd and Taubert, Andreas}, title = {Surface modification of ickel/Titanium Alloy and Titanium Surfaces via a Polyelectrolyte Multilayer/Calcium Phosphate Hybrid Coating}, issn = {1438-7492}, doi = {10.1002/mame.200900347}, year = {2010}, abstract = {The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20 degrees for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material).}, language = {en} } @article{KleinpeterBoelkeKoch2010, author = {Kleinpeter, Erich and Boelke, Ute and Koch, Andreas}, title = {Subtle Trade-off Existing between (Anti)Aromaticity, Push-Pull Interaction, Keto-Enol Tautomerism, and Steric Hindrance When Defining the Electronic Properties of Conjugated Structures}, issn = {1089-5639}, year = {2010}, language = {en} } @article{FokouMeier2010, author = {Fokou, Patrice A. and Meier, Michael A. R.}, title = {Studying and suppressing olefin isomerization side reactions during ADMET polymerizations}, issn = {1022-1336}, doi = {10.1002/marc.200900678}, year = {2010}, abstract = {Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC-MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well-defined polymers via ADMET with very little isomerization, which was not possible before.}, language = {en} } @article{BaranacStojanovicKlaumuenzerMarkovicetal.2010, author = {Baranac-Stojanovic, Marija and Klaumuenzer, Ute and Markovic, Rade and Kleinpeter, Erich}, title = {Structure, configuration, conformation and quantification of the push pull-effect of 2-alkylidene-4- thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives}, issn = {0040-4020}, doi = {10.1016/j.tet.2010.09.040}, year = {2010}, abstract = {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.}, language = {en} } @article{SchwarzBodenthinGeueetal.2010, author = {Schwarz, Guntram and Bodenthin, Yves and Geue, Thomas and Koetz, Joachim and Kurth, Dirk G.}, title = {Structure and properties of dynamic rigid rod-like metallo-supramolecular polyelectrolytes in solution}, issn = {0024-9297}, doi = {10.1021/Ma902057f}, year = {2010}, abstract = {Metal-ion-induced self-assembly in aqueous solution of the rigid ligand 1,4-bis(2,2':6',2 ''-terpyridine-4'-yl)benzene (1) with Fe(OAc)(2) and Ni(OAc)(2) is investigated with viscosimetry, SANS, and AFM. Ligand 1 forms extended, rigid-rod like metallo-supramolecular coordination polyeectrolytes (MEPEs) with a molar mass of up to 200 000 g mol(-1) under the Current experimental conditions. The molar mass depends oil concentration, stoichiometry, and time. By spin-coating MEPEs oil a solid surface, we call image the MEPEs in real space by AFM. Both AFM and SANS confirm the extended rigid-rod-type structure of the MEPEs. As a control experiment, we also studied the flexible ligand 1,3-bis[4'-oxa(2,2':6',2 ''-terpyridinyl)]propane (2). Ligand 2 does not form extended macro-assemblies but likely ringlike structures with three 10 four repeat units. Finally, we present it protocol to control the stoichiometry during self-assembly using conductometry, which is of paramount importance to obtain meaningful and reproducible results.}, language = {en} } @article{TiseanuParvulescuParvulescuetal.2010, author = {Tiseanu, Carmen and Parvulescu, Vasile and Parvulescu, Victoria and Cotoi, Elena and Gessner, Andre and Kumke, Michael Uwe and Simon, Simion and Vasiliu, Florin}, title = {Structural and photoluminescence characterization of mesoporous silicon-phosphates}, issn = {1010-6030}, doi = {10.1016/j.jphotochem.2010.07.015}, year = {2010}, abstract = {Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady- state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium- exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime.}, language = {en} }