Ruthenium(II/IV) complexes with potentially tridentate Schiff base chelates containing the uracil moiety

Herein we report the synthesis and characterization of trans-[(RuCl2)-Cl-II(PPh3)(3)] with potentially tridentate Schiff bases derived from 5,6-diamino-1,3-dimethyl uracil (H(2)ddd) and two 2-substituted aromatic aldehydes. In the diamagnetic ruthenium(II) complexes, trans-[RuCl(PPh3)(2)(Htdp)] (1) {H(2)tdp=5-((thiophen-3-yl)methyleneamino)-6-amino-1,3-dimethyluracil} and trans-[RuCl(PPh3)(2)(Hsdp)] (2) {H(2)sdp=5-(2-(methylthio)benzylideneamino)-6-amino-1,3-dimethyluracil}, the Schiff base ligands (i.e. Htdp and Hsdp) act as mono-anionic tridentate chelators. Upon reacting 5-(2-hydroxybenzylideneamino)-6-amino-1,3-dimethyluracil (H(3)hdp) with the metal precursor, the paramagnetic complex, trans-[(RuCl2)-Cl-IV(ddd)(PPh3)(2)] (3), was isolated, in which the bidentate dianionic ddd co-ligand was formed by hydrolysis. The metal complexes were fully characterized via multinuclear NMR-, IR-, and UV-Vis spectroscopy, single crystal XRD analysis and conductivity measurements. The redox properties were probed via cyclic voltammetry with all complexes exhibiting comparable electrochemical behavior with half-wave potentials (E-1/2) at 0.70V (for 1), 0.725V (for 2), and 0.68V (for 3) versus Ag|AgCl, respectively. The presence of the paramagnetic metal center for 3 was confirmed by ESR spectroscopy.