Study on the solution and solid-state fluorescence of novel BF2 complexes with (Z)-2-[phenanthridin-6(5H)-ylidene]-1-phenylethanone and its derivatives as ligands

Abstract

A family of novel BF₂ complexes with (Z)-2-[phenanthridin-6(5H)-ylidene]-1-phenylethanone and its derivatives as ligands were prepared and characterized. The structure–property relationship indicates that photophysical properties of these complexes, which are intensely emissive both in solution and solid state, except for one (C₄) with a N,N-dimethylamino group on the phenyl ring, are closely related to the electronic effect of the substituent at the phenanthridinyl or phenyl ring. X-ray crystallography explains the reason for the thoroughly quenched solid-state emission of C₄ in view of the molecular packing mode. Powder XRD measurements indicate that the piezofluoro-chromism of the complex (C₆) with a tetraphenylethene (TPE) group at the phenanthridinyl ring could be attributed to its morphology-dependent emission. Density functional theory calculations reveal the nature of the solvatochromic effect on complexes C₄ and C₆.