Synthesis and photochromic properties of novel nonsymmetric dihetarylethenes based on benzindole and thiophene

Novel nonsymmetric dihetarylethenes 3-(5-methoxy-1,2-dimethyl-1H-benzo[g]indol-3-yl)-4-(3-thienyl)-furan-2,5-dione and 1-alkyl- and 1-aryl-3-(5-methoxy-1,2-dimethyl-1H-benzo[g]indol-3-yl-4-(3-thienyl)-1(H)-pyrrole-2,5-diones were synthesized. The substitution of the furandione moiety for pyrroledione gives rise to the radiation and photochemical channels of deactivation of the electron excitation energy of dihetarylethenes. The products of photolysis of pyrrolediones undergo recyclization in both the ground and excited states.     

Electrochemical and chemical synthesis of new luminescent schiff base complexes

Bis-chelate complexes of zinc, cadmium, lead, and mercury with o-N-tosylbenzylidene imines containing the C₇H₁₅ and C₁₈H₃₇ substituents at the C=N group nitrogen atom were prepared by the methods of electrochemical and chemical syntheses. The structure of the azomethines and their complexes was established by the methods of heteronuclear ¹H, ¹³C NMR spectroscopy (multidimensional and multinuclear COSY, HETCOR and HETCOR_LONG techniques). The complexes, as demonstrated by the X-ray analysis for the zinc chelate, have strongly distorted octahedral structure formed by the four azomethine nitrogen atoms and two oxygen atoms of the tosyl fragments. The coordination compounds show fluorescence in the blue part of the spectrum in high quantum yields for the zinc chelates.     

The structural transformations and photo-induced processes in salicylidene alkylimines

The detailed comparative investigations of the mechanism of the fluorescent properties, formation and photochromic reaction in the salicylidene alkylimine (SALK) molecules with various N-Alk substituents and in corresponding more rigid model structures without C–Ph ring (A) twist have been carried out by the experimental and quantum-chemical methods.

The crucial role of the A ring twist and the importance of the N-Alk substituent structure in the light-induced processes including the ESIPT, TICT formation, fluorescence with anomalous Stokes shift (ASS) and the formation of the metastable coloured so-called “post-TICT” structures has been shown. The mechanism of these processes is similar to that of the salicylidene aniline (SA) molecule but there are some important distinctions caused mainly by the lack of the l_N–π_Ph electrons interactions and also by the steric ones. In general the decrease of the photochromic efficiency and the increase of the ASS in comparison to the SA molecule are provoked by the SALK structures’ peculiarities.     

Synthesis, structures, and photochromic properties of 2-methylthieno[3,2-b][1]benzothiophen-3-ylfulgide

The novel heterocyclic fulgide, 3-(1-methylethylidene)-4-[1-(2-methylthieno[3,2-b]-[1]benzothiophen-3-yl)ethylidene]dihydrofuran-2,5-dione, was obtained and isolated as a Z-isomer. Its structure was confirmed by electronic absorption spectroscopy, ¹H NMR spectroscopy, and X-ray diffraction analysis. The novel thienothiophene fulgide is photochromic in both solutions and the crystalline state. Its colored cyclic form resists photodegradation and is thermally stable. When benzothiophene is annulated with the thienyl fragment, the long-wavelength absorption peak of the cyclic isomer of the novel fulgide experiences a bathochromic shift compared to the earlier described 3-thienylfulgide. The TD B3LYP/6-311G**-calculated spectroscopic characteristics of the fulgide isomers suggest the formation of their photostationary mixture under irradiation with λ = 365 nm. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2318–2324, December, 2007.     

Synthesis,structures, and photochromic properties of 3-[(<Emphasis Type="Italic">E</Emphasis>)-alk-1-enyl]-4-(1-alkyl-5-methoxy-2-methyl-1<Emphasis Type="Italic">H</Emphasis>-indol-3-yl)furan-2,5-diones

New hetarylethenes, viz., 3-[(E)-alk-1-enyl]-4-(1-alkyl-5-methoxy-2-methyl-1H-indol-3-yl)furan-2,5-diones, exhibiting photochromic properties in solution were synthesized. The molecular and crystal structure of 3-(5-methoxy-1,2-dimethyl-1H-indol-3-yl)-4-[(E)-prop-1-enyl]furan-2,5-dione was determined by X-ray diffraction. The initial and photoinduced forms of hetarylethenes are characterized by thermal stability. The open-ring isomers of furandiones exhibit fluorescence with quantum yields of up to 0.1.     

Synthesis and photochromic properties of new nonsymmetric dihetarylethenes ?? indole and thiophene derivatives

New nonsymmetric dihetarylethenes were synthesized: 3-(5-methoxy-1,2-dimethyl-1H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and photochromic 1-alkyl-(1-aryl)-3-(5-methoxy-1,2-dimethyl-1H-indol-3-yl)-4-(3-thienyl)-1(H)-pyrrole-2,5-diones. The absence of benzoannulation in the indole moiety results in the enhancement of the efficiencies of fluorescence and photocyclization of noncyclic isomers compared to the benzoindole derivatives.     

Photo- and ionochromic indoline spiropyrans based on 7,8-dihydroxy-4-methyl-2-oxo-2<Emphasis Type="Italic">H</Emphasis>-chromene-6-carbaldehyde

A number of indoline spiropyrans were synthesized from 7,8-dihydroxy-4-methyl-2-oxo-2H-chromene-6-carbaldehyde. The products were found to exhibit both photochromic and ionochromic properties. According to the UV, IR, and ¹H NMR spectral data, they exist in the spiro form. Irradiation at λ 365 nm in 2-methylbutane-propan-2-ol (4:1) at 203 K induces their isomerization into colored merocyanine structure. Addition of alkaline earth and transition metal salts to acetonitrile solutions of these compounds at room temperature changes the isomer ratio and leads to formation of merocyanine complexes characterized by different colors, so that visual detection of Zn²⁺, Mg²⁺, Hg²⁺, and Pb²⁺ ions is possible.     

Photochemistry of a 6′‐cyanosubstituted spironaphthooxazine: photo‐induced decay of an open form

Photochemistry of three 6′‐cyanosubstituted spironaphthooxazines (SNO) in ethanol matrices at 77 K was studied by means of ultraviolet (UV) and erythrocyte sedimentation rate (ESR) spectroscopy and quantum chemistry. The quantum yield of the open form photolysis is found to be 0.01–0.02, which is high enough for 77 K. For one of the SNO, the formation of a merocyanine form radical was observed. The radicals were formed by an H atom abstraction from the solvent molecule to the light‐excited merocyanine isomers. The formation of a merocyanine radical represents a new specific channel of photochemically induced degradation of spirooxazines. Copyright © 2011 John Wiley & Sons, Ltd.     

Structures of spiropyrans exhibiting photochromic properties in the solid state

Russian Chemical Bulletin - Solid-state photochromic indoline spiropyrans bearing a formyl group at the 6′ and 8′ positions of the 2H-chromene moiety of the molecules were...     

Photo- and thermochromic spirans. 35.* Synthesis and photochromic properties of spiro[indoline-2,3′-pyrano[3,2-f]quinolines] and their cationic derivatives

New photochromic spiropyranoquinolines and their cationic derivatives have been synthesized. Quaternization of the quinoline fragment leads to significant enhancement of the thermal stability of the merocyanine isomers of these cationic spiropyrans.