Synthesis of 2-(3-cyano-5-hydroxy-5-methyl-4-vinylene-1H-pyrrol-2(5H)-ylidene)malononitriles – novel functionalized analogs of tricyanofuran-containing (TCF) push–pull chromophores

Synthesis of (Tricyanofuran-3-ylmethylene)hydrazinyl thiazole-containing chromophore, study of its photophysical properties, solvatochromism and TD-DFT computations

The chromophore 2-2-(3-cyano-5,5-dimethyl-4-((2-(thiazol-2-yl)hydrazono)methyl)-furan-2(5H)-ylidene)malononitrile (TzHTCF) was prepared by diazo-coupling of diazotized 2-aminothiazole with 3-cyano-2-(dicyanomethylene)-4,5,5-trimethylfuran (TCF). The TzHTCF absorption solvatochromism, in different polarity solvents, offered ΔE_max = +4.74 where the positive sign implied red shift occurrence and the TzHTCF lowest excited state was more polar than its ground one. While, the TzHTCF fluorescence spectrum afforded λ_em , in 416-670 nm range, and was more dependent on the solvent polarity than the absorption λ_max , despite both exhibited red shift by 24 and 254 nm, respectively. To discover the Stokes' shift ( ∆ ν ¯ ) behaviour of TzHTCF derivative, Lippert-Mataga and linear solvation-energy relationship (LSER) formulations have been utilized where the LSER displayed better results than the Lippert-Mataga (R² = 0. 9931). Furthermore, the LSER showed that the absorption and fluorescence solvatochromic behaviours were dependent on the solvent's hydrogen-bond donor (α) and acceptor (β), along with the solvent's polarizability (π*). Moreover, DFT calculations showed that TzHTCF has a planar configuration and its simulated absorption and emission spectra in DMSO revealed that λ_max was primarily originated from HOMO→LUMO and HOMO-1→LUMO transitions, respectively.

First thermal studies on visible-light-switchable negative T-type photochromes of a nitrile-rich series

Representatives of visible-light-switchable nitrile-rich negative T-type photochromes (NRP) were synthesized. The temperature effect on the thermal relaxation of the photoinduced form of NRP was studied for the first time. It was found that regardless the temperature the reverse thermal reaction in ethanol and 1,4-dioxane proceeded according to a first-order kinetic equation, while an unusual pseudo-zero order of the dark reaction was observed in acetonitrile. Using the obtained experimental data, the activation energy as well as the activation parameters, such as entropy and enthalpy of activation, were calculated for the first time for thermal relaxation of NRP photochromes. It was also shown that an initial form of NRP photochromes bearing a tricyanofuran acceptor was more temperature resistant than the initial form of photochromes with a tricyanopyrrole acceptor.

The temperature effect on the thermal stability of both the initial and photoinduced forms of nitrile-rich T-type photochromes was studied for the first time.

Synthesis of high molar extinction coefficient push–pull tricyanofuran-based disperse dyes: Biological activity and dyeing performance

Novel push–pull tricyanofuran-based disperse dyes demonstrated high extinction coefficient, good antimicrobial performance and high colorfastness on polyester fibers.

Tuning the photochromic properties of chromophores containing a nitrile-rich acceptor: a novel branch in the investigation of negative photochromes

High photoswitching contrast and variation of the thermal stability of the photoinduced form for a novel group of reverse photochromes are described for the first time.

First representatives of functionalized D–π–A chromophores containing a tunable hydroxytricyanopyrrole (HTCP) acceptor and N,N-disubstituted aminophenyl donor

D–π–A chromophores based on a hydroxytricyanopyrrole (HTCP) acceptor and N,N-disubstituted aminophenyl donor are described for the first time. Their absorption properties were thoroughly studied.