The electrochemistry of Pt(azb)(ttcn)+ and Pt(phpy)(ttcn)+ (azb=azobenzene, phpy=2-phenyl pyridine) has been investigated with cyclic voltammetry, spectroelectrochemistry and bulk electrolysis. These studies are consistent with a two-electron oxidation of the platinum center in most of the instances. The dependence of the redox potential on KX supporting electrolyte (KX=KCl, KBr and KI) suggests the involvement of the halide ion in the redox chemistry or in the formation of the oxidized complex. The cyclic voltammograms recorded after the electrochemical oxidation confirm that the metal complex does not undergo a significant decomposition during the time scale of the oxidation processes.
This Pt(chelate)(ttcn)n+; metal complex architecture also has been extended to synthesize platinum dimer complexes with Schiff-base bridging ligands. Three novel platinum ttcn monomer complexes, Pt(PTPI)(ttcn)2+ (1), Pt(PTPA)(ttcn)2+ (2) and Pt(PPA)(ttcn)2+ (3) and three dimer complexes, [Pt2(µ-bpcd)(ttcn)2]4+ (4), [Pt2(µ-bpbd)(ttcn)2]4+ (5) and [Pt2(µ-PBP)(ttcn)2]4+ (6) have been synthesized and fully characterized. In contrast to the reported synthetic route followed to synthesize 1-5, the dimer 6 was synthesized starting with Pt(ttcn)Cl2 and reacting the dechlorinated complex with half equivalent of the PBP ligand to avoid the hydrolysis of one imine bond. Moreover, it was observed that there is a wide variation in reversibility of electrochemistry of complexes 1-6, depending on the nature of the substituents attached to the pyridine carboxaldiimine/2-picolinamine nitrogen in oppose to the nearly reversible electrochemistry reported with similar aryl imine complexes. Among the dimer complexes 4-6, only 6 with a delocalized bridging ligand, showed an electrochemical communication between the two metal centers in cyclic voltammetry.
The findings from this work are expected to provide guidelines for designing two-electron reagents and to investigate their electron transfer rate constants and redox potentials. This knowledge is potentially valuable in rational design of catalysts. The studies reported here on dimer complexes with platinum ttcn moiety are especially interesting as they provide fundamental knowledge about covalently coupling two platinum centers to form dimers capable of releasing four-electrons at a given potential.