Investigation of acid-base behaviors of some imidazo[4,5-f]quinoline derivatives using semi-empirical methods

In this study, ∆H and ∆S values of A group (7-Methyl-1(3)H-imidazo[4,5-f]quinoline, 2-Phenyl-7-methyl-1(3)H-imidazo[4,5-f]quinoline,2-(4?Methylphenyl)-7-methyl-1(3)H-imidazo[4,5-f]quinoline, 2-(4?Methoxyphenyl)-7-methyl-1(3)H-imidazo[4,5-f]quinoline, 2-(2?-Pyridyl)-7-methyl-1(3)H-imidazo[4,5-f]quinoline, 2-(3?-Pyridyl)-7-methyl1(3)H-imidazo[4,5-f]quinoline, 2-(4?-Pyridyl)-7-methyl1(3)H-imidazo[4,5-f]quinoline)and B group (9H-pyrido[4,5-b]indole, 2-amino-9H-pyrido[2,3]indole, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline, 2-amino-3,4,7,8-tetramethyl-3H-imidazo[4,5-f]quinoxaline) were calculated in aqueous phase using semi-empirical quantum chemical calculation methods (AM1, PM3, MNDO,MINDO/3 ) and the obtained result were used to calculate acidity constants.COSMO solvation method was employed in the case of aqueous solutioncalculations. Acidity constant for first, second, third ( for pyridly substituents )protonation and deprotonation of A group compounds and B group compoundsprotonation were calculated theoritically. R2 values were determined by usingcalculated acidity constants and experimental values. Theoritical calculationsshowed that, the best correlation were observed between the experimental acidityconstants and calculated acidity constants by PM3 method.Keywords: İmidazoquinoline, Quinoxaline, Acidity, Acidity Constands,Semi-Empirical Methods