Flicking the Switch on Donor–Acceptor Interactions in Hexaazatrinaphthalene Dyes: A Spectroscopic and Computational Study

Abstract

Abstract A series of donor–acceptor compounds based on triphenylamine and hexaazatrinaphthalene are investigated. Using a variety of linker units, it is possible to tune the intensity of the low‐energy transition from 8 000 m −1 cm −1 to 24 000 m −1 cm −1 and vary the wavelength between λ =430 to 490 nm. The effect of the linker may be observed in the resonance Raman spectra with linker unit modes showing strong enhancement when they are coupled to the charge‐transfer transition. This is evident in the case of the C≡C and triazolyl linker units. Charge transfer is consistent with DFT calculations, which implicate some linkers as having pseudo‐donor‐like behaviour. The emission spectra of the dyes are solvatochromic with Stokes shift versus solvent parameter gradients of 20 000 cm −1 , showing that the dipole change is still large even when the bridge becomes involved in the transition.