Fluorescence properties of 1-(silylethynyl)naphthalenes and 1,4-bis (silylethynyl)naphthalenes in solutions, thin films and solid states

摘要

1-(Silylethynyl)naphthalenes (la-e) and 1,4-bis(silylethynyl)naphthalenes (2a-c) were prepared, and their fluorescence properties were evaluated in solutions, thin films and solid states. In dilute solutions, monomer emission is observed from substances in both groups and the relative fluorescence quantum yields of la-e increase as the steric bulk of the substituents on silicon increase. The observed concentration dependence of fluorescence intensities indicates that the self-quenching has a more pronounced effect on emission in shorter wavelength regions than that in longer wavelength regions. Analysis of Stern-Volmer type plots shows that formation of both an excimer and a termolecular excited complex is involved in fluorescence quenching of 1 in solution, whereas only an excimer is involved in quenching of 2. Fluorescence in thin films and solid states dispersion in KBr is dependent on number of silylethynyl groups present in the naphthalene derivatives. For example, excimer emission occurs from 1 while monomer emission occurs mainly from 2. X-ray crystallographic analysis of the crystal packing structure shows that 2b would have difficulty with forming an excimer because of steric hindrance, but that 2a can partially form an excimer owing to the slipped head-to-tail parallel orientation of naphthalene rings on neighboring molecules. The results of this effort demonstrate that the emission properties of 1- and 1,4-bis(silylethynyl)naphthalenes are influenced by the number of silylethynyl groups, the steric bulk of substituents on silicon atoms, and the compound's present state. (C) 2017 Elsevier B.V. All rights reserved.