Isomeric Bisdicyanomethylene-Substituted 1,3- and 1,2-Pyrilo-4-squaraines: Synthesis, Molecular, and Crystal Structure

Isomeric biscyanomethylene-substituted 1,3- and 1,2-pyrilo-4-squaraines have been synthesized. The formation of a dye, derivative of 1,2-squarate, from the derivative of 1,3-squarate has been demonstrated for the first time. Electronic absorption spectra of the synthesized dyes have been studied. The molecular and crystal structure has been investigated by X-ray diffraction analysis. Both isomeric dyes exist in the cis -conformation.