Negative Solvatochromism of Ferrocenyl Methine Dyes

A novel solvatochromic ferrocenyl methine dyes has beensynthesized by condensation of ferrocen-3-caboxaldehyde with activemethylene compounds under Knoevengel conditions and characterizedby UV-vis in a range of solvents. Compound 1a has a red shift in π-π*and a blue shift increases with solvent polarity in the MLCT (M -A)while 1b-1d variation of red as well as blue shifts from both states. Nod-d transition is observed in these compounds. These shifts areinterpreted by different dipole moments in the ground and excitedstate as well as solvent interaction between solute/solvent and Hbondingwith the acceptor.