Synthesis, characterization and DFT study of methoxybenzylidene containing chromophores for DSSC materials

Novel tricyanovinyl derived from hydrazones have been prepared by the reaction of tetracyanoethylene and phenylethylidene hydrazone, and these dyes showed absorption in the region of 539–650 nm. The dyes showed pronounced solvatochromic effects as the polarity of the solvents changed. The torsion in E isomer is smaller than Z and azo isomers of MBD1 and MBD2. The HOMOs are delocalized on whole of the molecule while LUMOs are distributed on the tricarbonitrile. The LUMO energies are above the conduction band of TiO2 and HOMOs of the dyes are below the redox couple of MBD1 and MBD2. The HOMO energies, LUMO energies and HOMO-LUMO energy gap of MBD1 and MBD2 are almost same. The absorption spectra of both the dyes in different solvents are approximately same except in cyclohexane.

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► DFT calculation revealed that the most stable isomers are E.
► The HOMO is localized on intact molecule while LUMO is distributed on the tricarbonitrile.
► The solvent polarity leads toward red or blue shift in the absorption spectra.
► LUMO energies are above the conduction band of TiO2 while HOMOs of the dyes are below the redox couple.