The Influence of Molecular Conformation on the Electronic Relaxation Processes. Complex Formation in the Ground State and Triple Fluorescences of 6-Acetoxyspiro[aceanthyrylene- 2(1H),9′(10′H)-anthracene]-10′-one

Abstract

Abstract The absorption spectra of 6-acetoxyspiro[aceanthyrylene-2(1H),9′(10′H)-anthracene]-10′-one(2) in cyclohexane, dichloromethane, and chloroform have been observed. The absorption spectra have been also observed as a function of concentration of chlorinated methanes in mixtures with cyclohexane. It was revealed that 2 forms a ground state complex with chlorinated methanes. The equilibrium constants for the ground-state complex formation with dichloromethane and chloroform were determined to be 0.14 and 0.17 mol−1 dm3, respectively. The fluorescence and fluorescence excitation spectra of 2 have been obtained as a function of excitation wavelengths and emission wavelengths in cyclohexane and chlorinated methanes. The spiro compound emits structured fluorescence(FM) in cyclohexane. On the other hand, three types of fluorescence bands (FM, FC, and FE) were observed in chlorinated methanes. The FC and FE bands are both structureless and their peak wavenumbers are 20800 and 18700 cm−1. The quenching of fluorescence quantum yield and lifetime were treated by Stern–Volmer kinetics considering the complex formation in both the ground and the excited states of the system. Based on the experimental findings, the origins of FM, FC, and FE bands are explained by the complex formation between 2 and chlorinated methanes in the ground state and exciplex formation in the excited state.