Solvatochromic and application in dye-sensitized solar cells of sandwich-like Cd(II) complexes: supramolecular architectures based on N(1),N(3)-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine.

A novel polydentate Schiff base ligand N(1),N(3)-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine (L) and its two dinuclear sandwich-like complexes {[CdL(NO3)(H2O)]·NO3}2 (1) and {[CdL(CH3CN)(H2O)]·(ClO4)2·(CH3CN)2}2 (2) were synthesized. Both C-H∙∙∙O, C-H∙∙∙N and π-π non-covalent interactions had essential roles in constructing the resulting three-dimensional supramolecular networks. L emits a more intense blue-green fluorescence emission around 493 nm than in dilute solution, exhibiting stacking-induced emission properties. Complexes 1 and 2 exhibited the dual properties of exceptional solvatochromism and fluorescence quenching towards CH3OH molecules. As these compounds could overcome the absent absorption of ruthenium complex N719 in the low wavelength region of the visible spectrum, offset the competitive visible light absorption of I3(-) and reduce the charge recombination of injected electrons, the Schiff base ligand l and complexes 1 and 2 were used as co-sensitizers in combination with N719 to investigate their effect on enhancing the performance of dye-sensitized solar cells. A short circuit current density of 14.37 mA cm(-2), an open-circuit voltage of 0.71 V and a fill factor of 0.61 corresponding to an overall conversion efficiency of 6.17% under AM 1.5 G solar irradiation were achieved when 1 was used as a co-sensitizer, which are much higher than the results obtained for dye-sensitized solar cells sensitized by N719 alone (5.06%).