Synthesis and spectral properties of a new ruthenium (II) tris-bipyridine with four ester groups and substituted phenol

A new ruthenium(II) complex (1) with four ester groups have been designed and synthesized, in which a phenol substituted by {[(2-hydroxy-3-(morpholin-4- ylmethyl)-5-tert-butylbenzyl)(pyridyl-2-methyl)amino]methyl} groups was covalently linked to ruthenium (II) tris-bipyridine. The structure of complex 1 was characterized by electrospray ionization mass spectrometer (ESI-MS) and 1D-NMR, 2D-NMR (gCOSY, HSQC and HMBC) spectra. The electrochemical and spectral properties were also studied. Introduction of the four carboxyl acid groups and the donor ligand tuned the spectra and the redox properties of compound 1. The MLCT transition was turned from 451 to 474 nm and the complex had long lifetime of the ³MLCT state emission. Moreover, the oxidation potential of Ru³⁺/Ru²⁺ of compound 1 was ∼360 mV higher than that of [Ru(bpy)₃]²⁺ which would enhance the driving-force of electron transfer. These results showed that the compound 1 had proper redox potentials and was suitable for being used as photosensitizer of solar cell.