Enantiopure sulfinyl azobenzenes as chiroptical switches

[reaction: see text] Photoswitchable enantiopure sulfinyl azo compounds have been synthesized. A remarkable perturbation of the azo system by the stereogenic sulfinyl moiety has been observed by CD in both the trans and the cis azobenzenes resulting by photoisomerization. After five irradiation cycles, the configurational integrity of these chiral switches remains unchanged.     

A multiple switching bisthienylethene and its photochromic fluorescent organogelator

A multiple switching fluorescent photochromic bisthienylethene bridged naphthalimide bearing cholesteryl groups was synthesized and its organogelator showed excellent photo-responsive and thermal reversible performance by light, thermal.     

乙烯／顺丁烯二酸酐共聚物为主链的光致变色苯氧基萘并萘醌聚合物

通过由３－溴丙－１－醇（１）与６－［４－（２－（４－羟基苯基）异丙基）苯氧基］－５,１２－萘并萘醌（２）反应制备新反应试剂６－［４－（２－（４－（３－羟基丙氧基）苯基）异丙基）苯氧基］－５,１２－萘并萘醌（３）,然后通过（３）与乙烯－顺丁烯二酸酐交替共聚物反应的方法成功合成了乙烯－顺丁烯二酸酐为主链的光致变色苯氧基萘并萘醌聚合物（４）。与化合物（２）相似,聚合物（４）具有正常的光致变色行为。同时发现,溶剂对聚合物（４）和化合物（２）的光诱导ｔｒａｎｓ→ａｎａ异构化反应速度有明显影响。在ＴＨＦ／Ｈ２ＳＯ４（Ｖ／Ｖ＝２４／１）中的速度常数约为在ＤＭＳＯ／Ｈ２ＳＯ４（Ｖ／Ｖ＝２４／１）中的速度常数的两倍     

Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

Photochromic dihetarylethenes

A series of new photochromic compounds were obtained for the first time from 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene by substituting bromine atoms or carboxy, alkoxycarbonyl, and carbamoyl groups for hydrogen atoms in positions 4 and 4′. Introduction of these substituents causes a slight bathochromic shift (by 20–30 nm) of a long-wavelength absorption band for the cyclic form and significantly increases the quantum yields of photocyclization Ф_A→B and ring opening Ф_B→A. Depending on the nature of a substituent, Ф_A→B decreases in the order COOH>COOMe>CONHAr. The quantum yields are markedly reduced when the ethylthio groups in positions 5 and 5′ are replaced by ethylsulfonyl groups (a tenfold reduction in Ф_A→B and a four- to fivefold reduction in Ф_B→A) The most considerable bathochromic shift of a long-wavelength band and the highest quantum yields of forward and reverse photoreactions were observed for 1,2-bis(4-bromo-2-ethylthio-3-thienyl) perfluorocyclopentene. 1,2- Bis (2-ethyl-5-ethylthio-4-methoxycarbonyl-3-thienyl)perfluorocyclopentene was structurally characterized by X-ray diffraction analysis.     

Photochromic polypeptides

Two photochromic polypeptides were synthesized by reaction of 1-(4-iodobutyl)-3,3- dimethylindolindolino-6′-nitrobenzospiropyran with poly-L -tyrosine; their molar contents on photochromic units were 27.3 and 44.7%. The spectra of the photo-induced merocyanines and their decoloration kinetics were compared with these of the monomeric model compound, obtained by reaction of the same N-(4-iodobutyl)-indolinospiropyran derivative with N-acetyltyrosine methyl ester. Different types of solvents have been examined, mainly dimethylformamide and pyridine, acetone and tetrahydrofuran, and methanol and ethylene glycol. The polypeptides showed a much less pronounced solvatochromism than their model; on the other hand, their absorption spectra presented two absorption maxima instead of one for the model. These differences in photochromic behavior were interpreted on the basis of the solvatation of the polymeric chain. Inverse photochromism was observed for polypeptide P₂ as well as for the model in ethylene glycol solution; this effect is due to a higher merocyanine content at the thermal equilibrium spiropyran ? merocyanine in high polar solvent.     

Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

Photochromic dihetarylethenes

1,2-Bis[2-methyl-5-(benzoxazol-2-yl)thien-3-yl]hexafluorocyclopentene was synthesized, and its photochronic properties were studied For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1011–1014, May, 1999.     

Nonlinear optical molecular switches as selective cation sensors

This work demonstrates that the recognition of cations by molecular switches can give rise to large contrasts of the second-order nonlinear optical (NLO) properties, which can therefore be used as a powerful and multi-usage detection tool. The proof of concept is given by evidencing, by means of ab initio calculations, the ability of spiropyran/merocyanine systems to selectively detect alkali, alkaline earth, and transition-metal cations.     

Amide-based molecular knots as platforms for fluorescent switches

A series of amide-based molecular knots equipped selectively with fluorescent dansyl and/or pyrenesulfonyl moieties were synthesized from the readily available tris(allyloxy)knotane. UV/Vis absorption spectra, emission spectra, and the emission lifetimes of the fluorescent knotanes were investigated in chloroform at 298 K. The absorption spectra of the knotanes correspond to those of mixtures of their UV-active constituents. The fluorescence quantum yields and lifetimes of the dansyl and pyrenesulfonyl moieties are partly quenched by the knotane platform. In the KN(Da)(2)(Py) species, the fluorescent excited state of the dansyl units (lambda(max)=510 nm) lies at lower energy than the fluorescent excited state of the pyrenesulfonyl unit (lambda(max)=385 nm), the emission of which is accordingly quenched with sensitization of the dansyl fluorescence. In the KN(Ao)(2)(Da), KN(Ao)(Da)(2), and KN(Da)(3) species, the addition of acids causes the protonation of their dansyl units with a consequent decrease in the intensity of the dansyl band at 510 nm and appearance of the emission band of the protonated dansyl unit (lambda(max)=340 nm). Each dansyl unit of KN(Ao)(Da)(2) and KN(Da)(3) undergoes the independent protonation. In these incompletely protonated knotanes the fluorescence of the protonated dansyl units is partly quenched by nonprotonated ones. These processes can be quantitatively reversed upon addition of a base. In KN(Da)(2)(Py), an increase of the fluorescence of its pyrenesulfonyl group is observed when the dansyl groups are protonated. The results obtained show that the readily available and easily functionalizable amide-knotanes can be used as an interesting scaffold to obtain fluorescent switches.     

Photochromic Dihetarylethenes: XVII. New Synthesis of Photochromic N-Alkyldithienylmaleimides

A new convenient procedure for the synthesis of photochromic N-alkyldithienylmaleimides was developed on the basis of the reaction of 3,4-bis(2,5-dimethyl-3-thienyl)furan-2,5-dione with primary amines. Photochromic properties of the products were examined.     

Photochromic coumarin spiropyrans

New photochromic spiropyrans (SPP) derived from 4-methyl-7-hydroxy-8-formylcoumarin have been synthesized. The effect of the heterene fragment on the spectral and photochromic properties of the SPP was examined. The photoproduct of the benzodithiolane SPP had the absorption with longest wavelength. Indoline SPP were found to have the most efficient photocoloring. Fluorescence of the cyclic form was found for the SPP.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 601–604, May, 1992     

Photochromic crown ethers

An amphiphilic crown-containing styryl dye (1) was synthesized, and the effects of irradiation, temperature, and alkali and alkali-earth metal ions on the conductivity and optical spectra of its solutions in dioctyl phthalate were studied. Compound1 in thetrans-form almost completely exists as ion pairs (IP). Irradiation at a long-wavelength absorption maximum (λ_max) results in a reversible increase in the conductivity and, hence, a degree of dissociation of IP (α); these parameters decrease when complexes with metal ions are formed. The relaxation times for the photoinduced conductivity coincide with a decrease in the extinction within experimental error in the 20–60°C temperature range. The photoinduced increase in α is caused bytrans—cis-isomerization and an increase in steric hindrances for the interaction of the ClO₄ ⁻ anion with the N⁺ atom of benzothiazolium in thecis-form of1. The activation energies for the darkcis—trans-relaxation, absolute α values, and thermodynamic parameters of dissociation of IP in thetrans-form, as well as the α values in a photostationary mixture ofcis—trans-isomers, were estimated. The decrease in α after binding with metal ions is likely caused by the redistribution of the positive charge to benzothiazolium through the conjugated system of1. Correlations between the decrease in conductivity (decrease in α) and the hypsochromic shift Δλ_max after the formation of complexes between1 and metal ions were observed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1301, July, 1997.