Spectroscopic and electrochemical investigation of coordination complexes of octakis(benzylthio)tetraazaporphyrincobalt(II)

Synthesis of new bichromophoric di- and pentanuclear complexes 2–7 by datively binding (bpy)2RuII, (phen)2RuII and Cp (PPh3)RuII units to the periphery of [Co(OBTTAP)], 1, and their spectroscopic properties are described. IR, 1H NMR, UV–Vis, and mass spectral data were used for their characterization. Relative intensities and positions of the Soret and Q-bands absorptions in the di- and pentanuclear complexes were observed shifted vis-à-vis that in the precursor complex [Co(OBTTAP)], 1. These complexes particularly, those possessing [Co(OBTTAP)] and (bpy)2RuII/(phen)2RuII units, exhibited efficient inter-component electronic excitation energy transfer in their fluorescence excitation–emission spectra, that are suggestive of a high degree of inter-component electronic interaction in them. Also, the electrode activity of the complexes improved upon binding of the peripheral units and they exhibited multiple one-electron reversible oxidation waves in the cyclic voltammograms. These effects have been explained in terms of dπ(S)–dπ(Ru) interactions.