Tuning of the colour and chemical stability of model boranils: a strong effect of structural modifications

Abstract

A series of diarylborinic complexes with salicydeneaniline ligands bearing various functional groups at the 6-position have been synthesized in high yields by applying a straightforward one-pot multicomponent protocol. UV-Vis measurements revealed the influence of electronic character of substituents on the observed maximum of emission (λ_em). This has been confirmed by a relatively strong linear correlation (R² = 0.92) of λ_em with Hammett σ_p⁺ constants. Such a correlation was investigated using a QTAIM analysis of the charge density distribution. Absorption and emission bands for the obtained systems span between 390–437 nm and between 506–590 nm, respectively, with quantum yields reaching 17%. Time-dependent UV-Vis absorption measurements revealed that diphenylborinic salicydeneaniline complexes undergo slow degradation in solution under ambient conditions. In contrast, the use of a naphthalene-based chromophore or the introduction of fluorinated phenyl groups at the boron atom resulted in stable systems.