Synthesis and spectroscopic studies of 4-Formyl-4′-N,N-dimethylamino-1,1′-biphenyl: The unusual red edge effect and efficient laser generation

Abstract

The synthesis and photophysics of 4-formyl-4′-N,N-dimethylamino-1,1′-biphenyl are reported. The emission spectrum in various solvent polarities demonstrates solvatochromism, indicating that the fluorescence originates from an electronically excited species with a strong charge transfer character. The change in Δ$\tilde v$ [$\tilde v$ _max(absorption) −$\tilde v$ _max(emission)] varies from ∼1500 cm⁻¹ inn-heptane to as much as ∼7500 cm⁻¹ in acetonitrile. In protic solvents, the unusual excitation energy-dependent steady-state emission (red edge effect), resulting from solvent dielectric relaxation, was observed in media with a low viscosity. The large Stokes-shifted and high-yield fluorescence led to the observation of the efficient lasing action. The frequency tunability of the laser output is strongly solvent dependent, generating a new charge transfer laser dye in the blue-green region.