Abstract
The ground-state geometries of 2-cyano-5-(4-(phenyl(4-vinylphenyl)amino)phenyl) penta-2,4-dienoic acid (TC4) derivatives have been optimized by using density functional theory (DFT) at B3LYP/6-31G** level of theory. The effect of bridge has been investigated on the electronic and charge transfer properties. The distortion between triphenylamine unit and acceptor moieties revealed there would be recombination barrier. The excitation energies have been computed by time dependent DFT at PCM-CAM-B3LYP/6-31G** and PCM-LC-BLYP/6-31G** level of theories. The absorption spectrum of TC4 computed at PCM-CAM-B3LYP/6-31G** level of theory is in good agreement with the experimental evidence while PCM-LC-BLYP/6-31G** level of theory underestimate it. The electron injection, electronic coupling constant and light harvesting efficiency (LHE) improved by elongating the bridge. The superior electron injection, electronic coupling constant, LHE, LUMO lying above the conduction band of TiO2 and HOMO below the redox couple compared to parent molecule revealed that new designed materials would be efficient photosensitizers.
In new designed derivatives of triphenylamine (TPA) light harvesting efficiency (LHE), electron injection (∆Ginject) and electronic coupling constants (|VRP|) have been enhanced by elongating the bridge. The CAM-B3LYP functional is more appropriate and reliable to investigate the ∆Ginject, LHE, and |VRP| for TPA based sensitizers than LC-BLYP.