Solvatochromic photoluminescence investigation of functional Schiff-bases: A systematic study of substituent effects

Rational design of an isatin-based colorimetric and solvatochromic receptor for carbonate ions and its application in molecular-scale logic gates & memory units

A simple and highly sensitive isatin-based colorimetric sensor ISAT 3(a-d) was synthesized through a single-step reaction. The as-prepared receptor ISAT 3b with carbonate ions (CO32- ions) shows a significant red shift in the UV-visible absorption spectra and a visible color change from pale yellow to pink. Also, the receptor ISAT 3b shows unique solvatochromic behavior with CO32- ions in different aprotic solvents and solvent compositions. Moreover, the receptor's pink coloration (absorption maxima at 544 nm) with CO32- ions could be reversible by adding HSO4- ions (attain initial pale-yellow color, absorption maxima at 425 nm), which can be repeatable. The observed color changes with spectral shift and reversibility of the receptor with CO32- ions and HSO4- ions provide "ON-OFF" switching for applying molecular logic gates. Receptors exhibited properties, such as reversibility and repeatability, benefit the design of a molecular-scale sequential memory unit with a display of "Writing-Reading-Erasing-Reading". The real sample analysis was also carried out to prove the practical applicability of receptor (ISAT 3b) for detecting CO32- ions.

Substituent effects on the photophysical properties of tris(salicylideneanilines)

The role of electron acceptor/donor group substitution on the photophysical properties of tris(salicylideneanilines) (TSANs) was investigated. These compounds were synthesised and characterised through spectroscopic techniques including steady state absorption and emission spectroscopies. Their photochemical reaction mechanisms and properties were explored with the aid of ab initio methods of quantum chemistry. The obtained results allow us to verify the dependence of multiple emission bands on the substitution of electron donating and accepting groups to the tris(salicylideneaniline) core. The results also stress the differences in phosphorescence behaviour of TSANs for which this type of emission has not been reported so far.

Photophysical transformations induced by chemical substitution to salicylaldimines

The role of electron-acceptor strength and microenvironment polarity on the photophysical properties of salicylaldimines.

White-light generation from all-solution-processed OLEDs using a benzothiazole–salophen derivative reactive to the ESIPT process

ESIPT for white-light generation from all-solution-processed OLEDs.

Kinetic analysis of tautomer forms of aromatic-urea compounds with acetate ions: solvent effect of excited state intermolecular proton transfer

In this paper, we report the solvent effect of excited state intermolecular proton transfer (ESIPT) reactions of urea compounds in the presence of tetrabutylammonium acetate (TBAAc). We prepared anthracene-urea compounds (9An and 2An), a pyrene-urea compound (Py) and an anthracene-diurea compound (9,10An), which have alkylsulfonyl groups to improve their solubility in various organic solvents. We investigated the solvent effects of the ESIPT reaction using absorption, fluorescence, and 1H NMR spectroscopy along with fluorescence decay measurements in dimethyl sulfoxide (DMSO), acetonitrile (MeCN), tetrahydrofuran (THF) and toluene. The tautomer fluorescence of 9An showed remarkable solvent dependence on the spectral red-shift compared with 2An, Py and 9,10An. As a result of the detailed spectroscopic investigations with regard to the solvent including kinetic analysis of the ESIPT for 9AnAcO-, we revealed that the energy gap between the normal and tautomer forms in the excited state depended on the hydrogen bond acceptor basicity (β), which is one of the Kamlet-Taft solvent parameters. Finally, we discovered that the tautomer structures of aromatic-urea compounds were stabilized by hydrogen bond interactions.