Spectral study of specific interactions between zwitterionic compounds and protic solvents.

The zwitterionic compounds, like ylids, can interact both by universal and specific forces with the protic solvents. Ylids have a visible electronic absorption band with intramolecular charge transfer (ICT), very sensitive to the solvent nature and considered as an indicator of their stability. Two zwitterionic compounds: pyridinium dicarbethoxy methylid and iso-quinolinium dicarbethoxy methylid were studied from solvatochromic point of view and the contribution of solute-solvent specific interactions to the total spectral shift of the visible ICT band was established.

Solvent scales used to study the intermolecular interactions in binary solutions of two p-aryl-pyridazinium methylids.

The visible electronic absorption band with intramolecular charge transfer of two pyridazinium ylids having common carbanion and different heterocycles is recorded in solutions and its position is correlated to parameters of some empirical scales of solvents. The nature of the intermolecular interactions in pyridazinium ylid solutions is discussed and the supply of each type of interaction is established based on solvatochromic study.