The Spectroscopic Behavior of Two New 5-(5-R-6-Hydroxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium Merocyanines in Various Solvents

Autor: Marta J. Sawicka, Jacek A. Soroka, Elwira K. Wróblewska, Monika Gąsiorowska
Rok vydání: 2011
Předmět:
Zdroj: Journal of Solution Chemistry. 41:25-35
ISSN: 1572-8927
0095-9782
DOI: 10.1007/s10953-011-9778-z
Popis: Solvatochromic studies on two new merocyanines, prepared from 5-(5-bromo-6-hydroxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate and 5-(5-nitro-6-hydroxynaphthyl-2)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate, were performed in 21 solvents using UV–vis spectroscopy. The VBHB model (J.A. Soroka and K.B. Soroka in J. Phys. Org. Chem. 4:592–604, 1991) was applied to describe their solvatochromic properties. The results indicate that both dyes exhibit variable solvatochromism, i.e. it is positive in nonpolar solvents and negative in polar aprotic and protic solvents. The solvatochromic shifts of both merocyanines are approximately 8000 cm−1(for toluene to water). The studies revealed that these two merocyanines exist in solutions as nonpolar (quinoid, i.e. vinylogous amide, V) or polar (zwitterionic, i.e. betaine, B) forms in their ground state, respectively. The dye with a nitro substituent can also form a hydrogen-bonded betaine (HB). This dye is found to be the first compound in the whole group of 7H-indolo[1,2-a]quinolinium merocyanines that does not comply with the VBHB model assumptions.
Databáze: OpenAIRE
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