Functionalized ruthenium dialkynyl complexes with high second-order nonlinear optical properties and good potential as dye sensitizers for solar cells

Various dipolar π-delocalized Ru(II) dialkynyl complexes were prepared and characterized. Their second-order nonlinear optical (NLO) properties were investigated by the electric-field-induced second harmonic generation (EFISH) technique working in CH2Cl2 solution with an incident wavelength of 1907 nm, whereas the dipole moments were determined by density functional theory (DFT) calculations. All the investigated complexes are characterized by a negative value of μβ1.907 EFISH, in agreement with a negative value of Δμeg (difference of the dipole moment in the excited and ground state) upon excitation. Their second-order NLO response can be easily modulated by the nature of the alkynyl substituents. Besides, the most promising "push-pull" ruthenium diacetylide complex, adequately functionalized for anchoring to TiO2, was tested as photosensitizer in dye-sensitized solar cells (DSSCs).