Infrared, Electronic Absorption and Emission Spectra of Tris (4-methyl-1-(1- methyl-1H-benzo [d] imidazol-2-yl)-4H-benzo [d]imidazo[1,5-a]imidazol-3-yl) methyl: Roles of Molecular Electronic States and Axial Substitution.

In order to comparing and explaining the experimental infrared, electronic absorption and emission spectra of tris (4-methyl-1-(1-methyl-1H-benzo [d] imidazol-2-yl) -4H-benzo [d] imidazo[1,5-a]imidazol-3-yl) methyl (L6), density functional theory calculations were performed to systematically study the spectral properties of several species with different electronic states (L6 , L6 and HL6 ), as well as the axial substituted derivative with methoxy group (L6-OCH ). The main peaks in the vibrational, electronic absorption and emission spectra were assigned in detail. Roles of molecular electronic states and axial substitution on the spectral properties are revealed. The calculated spectra are compared with experimental results to distinguish the nature of L6 in crystal and solvent. This work combing experiment and theoretical calculations would be good example for clarifying molecular electronic states and, thus, promising the practice application of such kind of novel molecules.