HeI photoelectron spectra and X-ray crystal structure of 2,2-difluoro-4-methyl-5,6-[2H-benzopyrano(3,4-e)-2-one]-1,3,2-dioxaborine

The HeI photoelectron spectra of 2,2-difluoro-4-methyl-5,6-[2H-benzopyrano(3,4-e)-2-one]-1,3,2-dioxaborine have been measured and compared with PES of 3-acetyl-4-hydroxycoumarin. The ionization bands in the spectra have been assigned on the basis of AMI semi-empirical quantum chemical calculations. X-ray analysis of the boron chelate crystals has also been undertaken. Effective pi-electron delocalization in the 1,3,2-dioxaborine ring of 2,2-difluoro-4-methyl-5,6-[2H-benzopyrano(3,4-e)-2-one]-1,3,2-dioxaborine both in gas phase and in solid state has been suggested. (c) 2005 Elsevier B.V. All rights reserved.