Photochromic liquid-crystalline copolymers containing crown ether groups

An approach was developed for the synthesis of new multifunctional photosensitive liquid-crystalline copolymers of the acryl series containing azobenzene, ionophoric, and mesogenic groups in the same macromolecule. The phase behavior of the copolymers was studied. Most of these copolymers were demonstrated to form nematic mesophases. An increase in the concentration of crown-containing groups to 26 mol.% leads to amorphization of the copolymers. The influence of complexation of the crown ether groups of the copolymers with potassium perchlorate on the mesomorphic properties of the systems was investigated. A comparative study of the photooptical properties of the copolymers in solution and thin films was performed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2332–2242, December, 2007.     

推拉型偶氮化合物的三阶非线性和光学双稳效应

本文报道从推拉型偶氮化合物中测得了非常高的三阶非线性极化率,X~(3)～6×10~(→3)esu.这对于引起光学双稳现象是至关重要的.利用波长为488nm的氩离子激光为光源,从这类材料掺杂的玻璃态聚合物薄膜的Kretschmann型态中,进一步观察到了光学双稳现象.与此同时,联系这类材料的顺反异构化反应历程,从电子吸收机制或光诱导的折射率变化机制对有关问题进行了讨论.     

测铜新试剂4—（邻苯二甲酰肼—5—三氮烯）偶氮苯

本文报道了新光度试剂４－（邻苯二甲酰肼－５－三氮烯）偶搂苯４ 合成，纯化     

Electrochemical Deposition of Azobenzene‐Containing Network Films with High‐Contrast and Stable Photoresponse

To fabricate stable photoresponsive films and devices, a cross‐linked network that firmly fixes the position of the chromophores is an ideal structure, because aggregation and/or phase separation effects of chromophores in matrix can be effectively restrained in such robust films. Herein, the in situ electrochemical deposition (ED) of azo‐based precursors containing multielectroactive carbazole units is utilized to construct highly cross‐linked photoresponsive films. 2‐(4‐(9,9‐bis(6‐(9H‐carbazol‐9‐yl)hexyl)‐9H‐fluoren‐2‐yl)phenyl)‐1‐(4‐(9,9‐bis(6‐(9H‐carbazol‐9‐yl)hexyl)‐9H‐fluoren‐7‐yl)phenyl)diazene (BFCzAzo) with high solvability in electrolyte solution, high electroactivity, and highly efficient photoresponsive ability is synthesized by Suzuki coupling reaction as a kind of ED precursor. A highly cross‐linked photoresponsive film is fabricated by ED method using BFCzAzo as ED precursor. The film can be patterned in large area by irradiation with interfering laser beam (355 nm), and the pattern possesses excellent thermal stability and insoluble ability in both organic and inorganic solvents. Excellent reversibility of the nanostructures is demonstrated by irradiation with 550 nm laser beam.

     

Stabilization of High Oxidation State Upconversion Nanoparticles by N‐Heterocyclic Carbenes

The stabilization of high oxidation state nanoparticles by N‐heterocyclic carbenes is reported. Such nanoparticles represent an important subset in the field of nanoparticles, with different and more challenging requirements for suitable ligands compared to elemental metal nanoparticles. N‐Heterocyclic carbene coated NaYF₄:Yb,Tm upconversion nanoparticles were synthesized by a ligand‐exchange reaction from a well‐defined precursor. This new photoactive material was characterized in detail and employed in the activation of photoresponsive molecules by low‐intensity near‐infrared light (λ =980 nm).     

Chiral separation of novel diazenes on a polysaccharide‐based stationary phase in the reversed‐phase mode

Chiral high‐performance liquid chromatography separation of two recently synthesized liquid crystalline materials C1 and C2 was studied in the reversed‐phase mode. Both materials have an azo‐moiety and one chiral center in their molecular structures. They were available in racemic and pure S forms. For the enantiomeric separations, a Chiralpak AY‐RH stationary phase based on amylose tris(5‐chloro‐2‐methylphenylcarbamate) coated on 5 μm silica was used. The compounds were analyzed in both of their possible forms, the more thermodynamically stable E form and the labile Z form. The conditions and time scale of the UV‐induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate S and R enantiomers of both of the studied materials not only in their E forms, but also in their Z forms. In comparison to the separation in the normal‐phase mode, which we have reported recently, the resolution in the reversed‐phase mode is significantly better. Interestingly, peak reversal was noticed for the S and R enantiomers when the separation was carried out with E versus Z forms of both compounds.     

Photocontrolled manipulation of a microscale object: a rotational or translational mechanism

In this paper the photocontrolled manipulation of solid materials on the surface of a liquid crystalline thin film is described. Three different types of films namely cholesteric liquid crystal (ChLC), compensated nematic liquid crystal (NLC) and nematic LC were used. The rotational and translational manipulation of the microscale solid object was induced by irradiation of light and mode of manipulation (either translational or rotational) was changed by changing the isomer of the azobenzene compound used to make the film. Rotational motion of the object was observed on the ChLC and compensated NLC films containing chirally pure azobenzene compound. The direction of rotational motion was controlled either by changing the optical isomer of the chiral azobenzene or by changing the irradiating light (from ultraviolet to visible). When racemic mixture of the chiral azobenzene compound was used, a translational motion of the object was observed. Even though the direction of the translational motion can be controlled by controlling irradiation position, more facile and precise manipulation of the objects was possible by spatially controlled irradiation of Ar(+) laser and diode UV laser.     

Absorption spectra of azobenzenes simulated with time‐dependent density functional theory

Using time‐dependent density functional theory and the polarizable continuum model, we have simulated the absorption spectra of an extended series of azobenzene dyes. First, we have determined a theoretical level optimal for this important class of dyes, and it turned out that a C‐PCM‐CAM‐B3LYP/6‐311+G(d,p)//C‐PCM‐B3LYP/6‐311G(d,p) approach represents an effective compromise between chemical accuracy and computational cost. In a second stage, we have compared the theoretical and experimental transition energies for 46 n → π^☆ and 141 π → π^☆ excitations. For the full set, that spans over a 302–565 nm domain, we obtained a mean absolute deviation of 13 nm (0.10 eV) and a linear correlation coefficient of 0.95, illustrating the accuracy of our approach, though some significant outliers pertained. In a last step, the impact of several modifications, that is, trans/cis isomerization, variation of the acidity of the medium and azo/hydrazo tautomerism have been modeled with two functionals. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010