Substituent effects on absorption and fluorescence spectra of carbostyrils

Absorption and fluorescence spectra as well as quantum yields of a series o f differently substituted carbostyrils (quinolin-2(1H)-ones) are reported. Especially for compounds containing donor substituents in position 6, subst antial bathochromic shifts (comparable to analogous coumarins) of both abso rption as well as fluorescence transitions are obtained. High absorption in tensities and quantum yields are found for 7-donor substituted isomers. Sem iempirical molecular orbital calculations (AM1 for structures, ZINDO for el ectronic transition energies) prove to be a suitable tool for the predictio n of absorption and fluorescence properties of these compounds. Ab initio a nd density functional calculations establish the lactam form as the dominan t tautomer of the parent quinolin-2(1H)-one. (C) 1999 Elsevier Science B.V. All rights reserved.