Unexpected photoinduced phenomena in chiral–photochromic cholesteric copolymers with a triplet sensitizer.

For the first time the possibility of energy transfer from a triplet photosensitizer to chiral–photochromic fragments in photoactive cholesteric systems was demonstrated. For this purpose we prepared mixtures containing chiral–photochromic cholesteric copolymers with a triplet sensitizer—acrydine orange (AO). Chiral–photochromic groups in copolymers contain a C=C bond capable for undergoing E–Z isomerization during UV irradiation. All polymer mixtures form a chiral nematic phase displaying selective light reflection with _max~650–1,000 nm depending on the structure and concentration of the chiral groups. Irradiation of mixtures by visible light (>450 nm) leads to a shift of the selective light reflection peak to a long-wavelength spectral region. This effect is associated with a decrease of anisometry of chiral–photochromic fragments in copolymers during their E–Z isomerization. It is important to emphasize, that chiral–photochromic side groups of copolymers do not absorb visible light themselves; therefore, the previously mentioned changes can be explained by the energy transfer from photoexcited AO molecules in the triplet state to isomerizable fragments. The study of the kinetics of this process revealed a rather unexpected phenomenon: after the first 60–80-min irradiation, the helix pitch of the supramolecular structure of the mixtures increases, but after successive irradiation the helix pitch decreases. The possible explanations of this phenomenon were suggested. It was demonstrated that these mixtures may be used for irreversible recording of optical information.     

Liquid-crystalline carbosilane dendrimers of different molecular architecture with photochromic mesogenic and aliphatic terminal groups

Second-generation (G-2) liquid-crystalline carbosilane block and statistical dendrimers with aliphatic (decyl) and photochromic (azobenzene-containing) mesogenic terminal groups and a G-2 homo-dendrimer containing the same mesogenic terminal groups were synthesized for the first time. The influence of dendritic architecture on the phase behavior of the dendrimers and on photoinduced Z-E-isomerization of the azobenzene fragments in mesogenic terminal groups in dendrimer solutions are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2325–2331, December, 2007.     

Photochromic LC copolymers containing azobenzene and crown‐ether groups

An approach for the creation of a novel family of multifunctional crown‐ether‐containing comb‐shaped copolyacrylates consisting of chromophoric (azobenzene), ionophoric (crown‐ether), and mesogenic groups in the same macromolecule was developed. Phase behavior of the copolymers was studied, and correlation between their molecular structure and thermal properties was established. The increase of crown‐ether‐containing groups' concentration up to 26 mol % leads to disruption of nematic order and formation of amorphous phase. Influence of copolymers complexation with potassium perchlorate on mesomorphic properties of such systems was investigated. It was shown that complexation leads to decrease in mesophase thermostability due to the significant reducing of the side group anisometry by perchlorate counter ion. The comparative investigations of photooptical properties and photoorientation processes of copolymers and their complexes were also performed. An essential difference in kinetics of photooptical behavior was revealed; the bulky crown‐ether substituents decrease rotational mobility and prevent photoorientation process of azobenzene fragments diminishing photoinduced orientation and order parameter. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6532–6541, 2008     

Photochromism of single crystals of arylhydrazide derivatives

Photochromic transformations in single crystals of hydrazides due to trans—cis-isomerization were found. The presence of the hydroxyl group in the ortho-position of the benzylidene fragment completely precludes photoinduced isomerization in the crystalline state.     

3-甲基-1,4-二苯氧基-9,10-蒽醌的合成及其光致变色性

合成了3-甲基-1,4-二苯氧基-9,10-蒽醌,其结构经1^H NMR,13^C NMR,IR和MS表征,并通过紫外光谱探讨了其光致变色性,讨论了取代基对蒽醌类化合物光致变色性的影响。     

超分子凝胶中的光化学反应

超分子凝胶中的光化学反应是比较特殊的一类反应,通常是将具有光响应活性的基团或分子引入到超分子凝胶的自组装体系中,因此,能够将超分子凝胶独特的性质与光化学反应的优势有效地结合起来,构筑新型的光功能材料,这使得此类超分子凝胶在光信息存储、光开关及光转换器件等前沿领域具有广阔的应用前景.本文主要总结近年来国内外包括作者课题组对超分子凝胶中光化学反应方面的研究进展,以及其在多重响应凝胶、手性光学开关以及手性合成方面的应用.     

Spectrophotometric determination of thermal transition of polymeric systems using photochromic probes

Mercury-dithizone complex both free and bonded to a polymeric system has been synthesized and used to measure the thermal transition of polystyrene, poly(vinyl acetate), and some other polymers. The thermal relaxation rate of the activated complex in dark has been found to be dependent on the free volume of a polymer matrix. The rate goes through a maximum above T_g of a polymer. A very sensitive method, based on thermal recovery of activated photochromic probe chromophore has been devised to measure the thermal transition of both single and multicomponent polymer matrices. © 1995 John Wiley & Sons, Inc.     

氯化钠晶体的光致变色特性

系统研究了γ射线辐照和电子束轰击着色的氯化钠晶体的光致变色特性及其形成机理，在４４８Ｋ，着色晶体经几个激光脉冲照射就能有效地产生Ｆ→Ｃ转换，产生的胶体心尺度随着色剂量增加而增大，在着色氯化钠晶体中观测到吸收带位于６２５ｎｍ的新胶体心。在５２３Ｋ，可有效地产生Ｃ→Ｆ转换，实现了Ｆ和Ｃ心的可逆转换，在Ｆ带激光照射下，Ｆ→Ｃ转换主要通过Ｆ和Ｆ心光致电离后产生的可动缺陷来实现的，并从机理上提出简明的物理解     

Investigation of cation complexation behavior of azacrown ether substituted benzochromene

The study of the complex formation of 3,3‐diphenyl‐3H‐benzo[f]chromenes containing aza‐18‐crown‐6‐ether, diaza‐18‐crown‐6‐ether or morpholine units with alkali, alkaline earth, heavy and transition metal cations in acetonitrile is reported. The spectroscopic and kinetic behavior of the photomerocyanine isomers of these chromenes is strongly affected by complexation with a metal cation. In order to interpret some of experimental data, an ab initio theoretical analysis of photochromic‐crown ether and its cation complexes was conducted. The different site of coordination of mono‐ and divalent cations to determine the minimum‐energy structure of benzochromene complexes in gas phase as well as in acetonitrile as solvent was explored. The coordination of both carbonyl oxygen and crown‐ether macrocyle with divalent cations in carbonyl‐capped structure is found to be the most stable isomer in gas as well as in condensed media. The crown‐containing benzochromenes were studied in liquid‐liquid extraction experiments toward there capacity to transfer metallic salts from water into an organic phase.The high selectivity to extraction of Ag⁺ was found. Copyright © 2007 John Wiley & Sons, Ltd.     

Structural and charge‐transfer properties of indolylfulgides

The structural and electronic properties of a photochromic molecule dictate their potential photochemical activity. To gain insight into these influences, the ground‐state structure and excited state properties of six indolylgulgides were calculated using several time dependent‐density functional theory (DFT) (TD‐DFT)//DFT methods, second‐order M?ller–Plesset (MP2), and CIS(D). These methods simulated the charge‐transfer properties and the conformation of the ground‐state structure for each molecule. Generally, TD‐DFT accurately simulated the expected charge‐transfer state. The degree of spatial overlap of the occupied and virtual molecular orbitals involved in the S₁ transition of indolylfulgides quantitatively assessed their charge‐transfer character and was qualitatively useful in assessing their photochromic activity. The M06, M06‐2X, and M11 structures were quite similar to those calculated by MP2. Structural differences, similarities, and functional trends are compared and discussed. © 2013 Wiley Periodicals, Inc.