Introduction
λ2,λ4-benzobis(thiadiazole) (BBTD) derivatives have unique electronic structures consisting of heterocycles containing hypervalent sulfur atoms. These heterocylic molecules have high electron affinities and are expected to have unique photophysical properties. No spectroscopic data are available in the gaseous phase of diphenylbenzobis(thiadiazole) (DPBBTD),
although the wavelengths of spectral maxima in the absorption and dispersed fluorescence spectra in methylene chloride were reported as 558 and 642 nm.
The phenyl groups in the excited DPBBTD molecule probably have torsional motions. From a molecular structural point of view, the torsional potential energy surfaces in the electronic ground (S0) and first excited singlet (S1) states of DPBBTD are expected to be similar to those of biphenyl because the intramolecular interference between the H atom in the phenyl group and the N atom in the BBTD skeleton is rather insignificant.
Laser induced fluorescence (LIF) spectra and fluorescence decay curves were observed for DPBBTD in supersonic free jets.
