The Origin Of Conformational Solvatochromism In Phenylmethylidene-Bis (Pyrrolo[2,3-B]Quinoxaline) Derivative

Phenylmethylidene-bis(pyrrolo[2,3-b]quinoxaline) derivative (1) was synthesized by the reaction between the 3-thiobenzoylpyrrolo[2,3-b]quinoxaline (SPQ) and a secondary amine or NaOH in DMF solution. The obtained compound was characterized by single crystal X-ray diffraction, which indicated the presence of pair of P and M helical enantiomers in the crystal structure. Molecules of 1 showed positive solvatochromism, with about 40 nm bathochromic shift. The theoretical calculations showed that the solvatochromism of the investigated compound depends on the conformational changes induced by the formation of the hydrogen bond with a strong acceptor. These conformational changes described by the angle between chromophore planes correlate with the solvent polarity.