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101.
Sysoiev D Fedoseev A Kim Y Exner TE Boneberg J Huhn T Leiderer P Scheer E Groth U Steiner UE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(24):6663-6672
In an attempt to design molecular optoelectronic switches functioning in molecular junctions between two metal tips, we synthesized a set of photochromic compounds by extending the π-system of 1,2-bis-(2-methyl-5-formylfuran-3-yl)perfluorocyclopentene through suitable coupling reactions involving the formyl functions, thereby also introducing terminal groups with a binding capacity to gold. Avoiding the presence of gold-binding sulphur atoms in the photoreactive centre, as they are present in the frequently used analogous thienyl compounds, the newly synthesized compounds should be more suitable for the purpose indicated. The kinetics of reversible photoswitching of the new compounds by UV and visible light was quantitatively investigated in solution. The role of conformational flexibility of the π-system for the width of the UV/Vis spectra was clarified by using quantum chemical calculations with time-dependent (TD)-DFT. As a preliminary test of the potential of the new compounds to serve as optoelectronic molecular switches, monolayer formation and photochemical switching on gold surfaces was observed by using surface plasmon resonance. 相似文献
102.
Andreu I Neshchadin D Rico E Griesser M Samadi A Morera IM Gescheidt G Miranda MA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(36):10089-10096
A thorough mechanistic study has been performed on the reaction between benzophenone (BZP) and a series of 1,4-dienes, including 1,4-cyclohexadiene (CHD), 1,4-dihydro-2-methylbenzoic acid (MBA), 1,4-dihydro-1,2-dimethylbenzoic acid (DMBA) and linoleic acid (LA). A combination of steady-state photolysis, laser flash photolysis (LFP), and photochemically induced dynamic nuclear polarization (photo-CIDNP) have been used. Irradiation of BZP and CHD led to a cross-coupled sensitizer-diene product, together with 6, 7, and 8. With MBA and DMBA as hydrogen donors, photoproducts arising from cross-coupling of sensitizer and diene radicals were found; compound 7 was also obtained, but 6 and o-toluic acid were only isolated in the irradiation of BZP with MBA. Triplet lifetimes were determined in the absence and in the presence of several diene concentrations. All three model compounds showed similar reactivity (k(q) ≈10(8) M(-1) s(-1)) towards triplet excited BZP. Partly reversible hydrogen abstraction of the allylic hydrogen atoms of CHD, MBA, and DMBA was also detected by photo-CIDNP on different timescales. Polarizations of the diamagnetic products were in full agreement with the results derived from LFP. Finally, LA also underwent partly reversible hydrogen abstraction during photoreaction with BZP. Subsequent hydrogen transfer between primary radicals led to conjugated derivatives of LA. The unpaired electron spin population in linoleyl radical (LA(.)) was predominantly found on H(1-5) protons. To date, LA-related radicals were only reported upon hydrogen transfer from highly substituted model compounds by steady-state EPR spectroscopy. Herein, we have experimentally established the formation of LA(.) and shown that it converts into two dominating conjugated isomers on the millisecond timescale. Such processes are at the basis of alterations of membrane structures caused by oxidative stress. 相似文献
103.
Dr. Léo Leroyer Dr. Christine Lepetit Dr. Arnaud Rives Dr. Valérie Maraval Dr. Nathalie Saffon‐Merceron Dr. Dmytro Kandaskalov David Kieffer Prof. Remi Chauvin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(11):3226-3240
When targeting the quadrupolar p‐dianisyltetraphenyl‐carbo‐benzene by reductive treatment of a hexaoxy‐[6]pericyclyne precursor 3 with SnCl2/HCl, a strict control of the conditions allowed for the isolation of three C18‐macrocyclic products: the targeted aromatic carbo‐benzene 1 , a sub‐reduced non‐aromatic carbo‐cyclohexadiene 4 A , and an over‐reduced aromatic dihydro‐carbo‐benzene 5 A . Each of them was fully characterized by its absorption and NMR spectra, which were interpreted by comparison with calculated spectra from static structures optimized at the DFT level. According to the nucleus‐independent chemical shift (NICS) value (NICS≈?13 ppm), the macrocyclic aromaticity of 5 A is indicated to be equivalent to that of 1 . This is confirmed by the strong NMR spectroscopic deshielding of the ortho‐CH protons of the aryl substituents, but also by the strong shielding of the internal proton of the endocyclic trans‐CH?CH double bond that results from the hydrogenation of one of the C?C bonds of 3 . Both the aromatics 1 and 5 A exhibit a high crystallinity, revealed by SEM and TEM images, which allowed for a structural determination by using an X‐ray microsource. A good agreement with calculated molecular structures was found, and columnar assemblies of the C18 macrocycles were evidenced in the crystal packing. The non‐aromatic carbo‐cyclohexadiene 4 A is shown to be an intermediate in the formation of 1 from 3 . It exhibits a remarkable dichromism in solution, which is related to the occurrence of two intense bands in the visible region of its UV/Vis spectrum. These properties could be attributed to the dibutatrienylacetylene (DBA) unit that occurs in the three chromophores, but which is not involved in a macrocyclic π‐delocalization in 4 A only. A versatile redox behavior of the carbo‐chromophores is evidenced by cyclic voltammetry and was analyzed by calculation of the ionization potential, electron affinity, and frontier molecular orbitals. 相似文献
104.
Zhang H Lu Y Zhang Z Fu H Li Y Volkmer D Denysenko D Wang E 《Chemical communications (Cambridge, England)》2012,48(58):7295-7297
A 12-connected metal-organic framework based on an unprecedented cyclic Cu(12) cluster with a large internal cavity has been prepared, and its cation exchange property was determined. 相似文献
105.
Nikolaienko TY Bulavin LA Hovorun DM 《Physical chemistry chemical physics : PCCP》2012,14(20):7441-7447
Physical properties of over 8000 intramolecular hydrogen bonds (iHBs), including 2901 ones of the types OH···O, OH···N, NH···O and OH···C, in 4244 conformers of the DNA-related molecules (four canonical 2'-deoxyribonucleotides, 1,2-dideoxyribose-5-phosphate, and 2-deoxy-D-ribose in its furanose, pyranose and linear forms) have been investigated using quantum theory of atoms in molecules (QTAIM) and vibrational analysis. It has been found that for all iHBs with positive red-shift of the proton donating group stretching frequency the shift value correlates with ρ(cp)-the electron charge density at the (3,-1)-type bond critical point. Combining QTAIM and spectroscopic data new relationships for estimation of OH···O, OH···N, NH···O and OH···C iHB enthalpy of formation (kcal mol(-1)) with RMS error below 0.8 kcal mol(-1) have been established: E(OH···O) = -3.09 + 239·ρ(cp), E(OH···N) = 1.72 + 142·ρ(cp), E(NH···O) = -2.03 + 225·ρ(cp), E(OH···C) = -0.29 + 288·ρ(cp), where ρ(cp) is in e a(0)(-3) (a(0)- the Bohr radius). It has been shown that XHY iHBs with red-shift values over 40 cm(-1) are characterized by the following minimal values of the XHY angle, ρ(cp) and nubla(2)ρ(cp): 112°, 0.005 e a(0)(-3) and 0.016 e a(0)(-5), respectively. New relationships have been used to reveal the strongest iHBs in canonical 2'-deoxy- and ribonucleosides and the O(5')H···N(3) H-bond in ribonucleoside guanosine was found to have the maximum energy (8.1 kcal mol(-1)). 相似文献
106.
Leroyer L Lepetit C Rives A Maraval V Saffon-Merceron N Kandaskalov D Kieffer D Chauvin R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(11):3226-3240
When targeting the quadrupolar p-dianisyltetraphenyl-carbo-benzene by reductive treatment of a hexaoxy-[6]pericyclyne precursor 3 with SnCl(2)/HCl, a strict control of the conditions allowed for the isolation of three C(18)-macrocyclic products: the targeted aromatic carbo-benzene 1, a sub-reduced non-aromatic carbo-cyclohexadiene 4A, and an over-reduced aromatic dihydro-carbo-benzene 5A. Each of them was fully characterized by its absorption and NMR spectra, which were interpreted by comparison with calculated spectra from static structures optimized at the DFT level. According to the nucleus-independent chemical shift (NICS) value (NICS≈-13 ppm), the macrocyclic aromaticity of 5A is indicated to be equivalent to that of 1. This is confirmed by the strong NMR spectroscopic deshielding of the ortho-CH protons of the aryl substituents, but also by the strong shielding of the internal proton of the endocyclic trans-CH=CH double bond that results from the hydrogenation of one of the C≡C bonds of 3. Both the aromatics 1 and 5A exhibit a high crystallinity, revealed by SEM and TEM images, which allowed for a structural determination by using an X-ray microsource. A good agreement with calculated molecular structures was found, and columnar assemblies of the C(18) macrocycles were evidenced in the crystal packing. The non-aromatic carbo-cyclohexadiene 4A is shown to be an intermediate in the formation of 1 from 3. It exhibits a remarkable dichromism in solution, which is related to the occurrence of two intense bands in the visible region of its UV/Vis spectrum. These properties could be attributed to the dibutatrienylacetylene (DBA) unit that occurs in the three chromophores, but which is not involved in a macrocyclic π-delocalization in 4A only. A versatile redox behavior of the carbo-chromophores is evidenced by cyclic voltammetry and was analyzed by calculation of the ionization potential, electron affinity, and frontier molecular orbitals. 相似文献
107.
Baranov MS Lukyanov KA Borissova AO Shamir J Kosenkov D Slipchenko LV Tolbert LM Yampolsky IV Solntsev KM 《Journal of the American Chemical Society》2012,134(13):6025-6032
Members of the green fluorescent protein (GFP) family form chromophores by modifications of three internal amino acid residues. Previously, many key characteristics of chromophores were studied using model compounds. However, no studies of intermolecular excited-state proton transfer (ESPT) with GFP-like synthetic chromophores have been performed because they either are nonfluorescent or lack an ionizable OH group. In this paper we report the synthesis and photochemical study of two highly fluorescent GFP chromophore analogues: p-HOBDI-BF2 and p-HOPyDI:Zn. Among known fluorescent compounds, p-HOBDI-BF(2) is the closest analogue of the native GFP chromophore. These irrreversibly (p-HOBDI-BF(2)) and reversibly (p-HOPyDI:Zn) locked compounds are the first examples of fully planar GFP chromophores, in which photoisomerization-induced deactivation is suppressed and protolytic photodissociation is observed. The photophysical behavior of p-HOBDI-BF2 and p-HOPyDI:Zn (excited state pK(a)'s, solvatochromism, kinetics, and thermodynamics of proton transfer) reveals their high photoacidity, which makes them good models of intermolecular ESPT in fluorescent proteins. Moreover, p-HOPyDI:Zn is a first example of "super" photoacidity in metal-organic complexes. 相似文献
108.
Brian T. Gregg Kathryn C. Golden John F. Quinn Hong-Jun Wang Wei Zhang Ruifang Wang Francis Wekesa Dmytro O. Tymoshenko 《Tetrahedron letters》2009,50(27):3978-4013
A series of α,α-disubstituted amines have been prepared in a simple and efficient one-pot procedure by the addition of Grignard reagents to a series of aliphatic, aromatic, and heteroaromatic nitriles. Key to this reported procedure is the unprecedented addition of the Grignard reagent to the nitrile under heating by microwave irradiation which both significantly improves reaction yields and reduces reaction times. In general, the Grignard addition reaction is complete within 5-10 min at 100 °C followed by rapid reduction with sodium borohydride to give the target amines. 相似文献
109.
Mykhailo D. Bilokin Dmytro A. Yushchenko Andrey S. Klymchenko Yves Mely 《Tetrahedron letters》2009,50(33):4714-1349
New derivatives of 3-hydroxyquinolone (3HQ) with a fused benzene ring (3-hydroxybenzo[g]quinolones) have been synthesized. They display a remarkable red shift of their absorption spectrum in comparison with other 3HQ analogs allowing their excitation by common He/Cd and Ar-ion lasers. As a result of their irreversible excited-state intramolecular proton transfer (ESIPT) reaction, they display a dual fluorescence in a series of solvents of varying polarities, starting from toluene to methanol. The dual emission of these dyes correlates well with solvent H-bond basicity, which is connected with the effect of this solvent property on the kinetics of the ESIPT reaction. In addition to their red-shifted absorption and fluorescence, these new derivatives show a larger separation of their two emission bands and a more appropriate range of their intensity ratio than the previously synthesized 3HQs. These properties allow an improved ratiometric evaluation of the local H-bond basicity of unknown environments, which will favor future applications of the new dyes in polymer and biological sciences. 相似文献
110.
Pressure dependence of the specific volume, V(P), of the recently discovered high-pressure compound Hf3N4 having cubic Th3P4-type structure (c- Hf3N4) has been measured at room temperature up to 43.9 GPa in a diamond anvil cell using energy-dispersive X-ray powder diffraction combined with synchrotron radiation. A least-square fit of the Birch-Murnaghan equation of state to the experimental V(P)-data yielded for c- Hf3N4 the bulk modulus of and its first pressure derivative of . For fixed at 4 the bulk modulus of c- Hf3N4 was determined to be . The obtained B0-value is only insignificantly below that estimated in preliminary measurements. Existing theoretical predictions for B0 scatter around the present experimental data. The observation of a high bulk modulus of c- Hf3N4 supports the suggestion that this compound could have high hardness. 相似文献