S.L. Efimova, Yu.V. Malyukin
Experimental investigation of absorption and luminescence
spectra of 2-pyrazoline and 1,8-naphthoylene-1',2'-benzimidazole (NBI)
derivatives having strong electron-donor and electron-acceptor substitutes
in the conjugation chain was carried out in aprotonic solutions of
various polarity. For some luminophors in a high-polar solvent, the
anomalous two-band luminescence is found. The relative intensity of
observed bands has been found to be defined by the solvent polarity,
as well as by substitutes acceptor and donor strength. Two-band
luminescence
of 2-pyrazoline derivatives is caused by suppression of electron interactions
in a biphluorophoric molecule induced by a polar solvent as well as
an acceptor substitutes, while for NBI derivatives observed luminescence
features are associated with TICT-state formation.