Cyclohexene-Embedded Dicyanomethylene Merocyanines - Consecutive Three-Component Coupling-Addition Synthesis and Chromophore Characteristics.

A concise and efficient consecutive three-component alkynylation-addition synthesis of cyclohexene-embedded dicyanomethylene merocyanines furnishes a small library of dyes in moderate to excellent yield. The dyes possess strong absorption coefficients of the longest wavelength absorption bands. According to the crystal structure, the small bond length alternations account for a highly delocalized electronic ground state. The electronic structure of the absorption bands is qualitatively rationalized by TDDFT calculations, which explain that intense HOMO-LUMO transitions along the merocyanine axis lead to cyanine similar Stokes shifts.