SYNTHESIS AND PROPERTIES OF CYCLIC RUTHENIUM(II) PORPHYRIN TETRAMERS

Tetrameric ruthenium(II) porphyrin complexes, [Ru(4-PyP3P)(CO)](4), 1, [Ru(4-PyT3P)(CO)](4), 2, and [Ru(4-PyT3P)(Py)](4), 3, (4-PyP3P = 5-(4 -pyridyl)-10,15,20-triphenylporphyrinato dianion, 4-PyT3P = 5-(4-pyrid yl)-10,15,20-tritolylporphyrinato dianion). were self-assembled and we re characterized by H-1 NMR, IR, and FABMS spectroscopic methods and e lemental analyses. The spectroscopic results certified that the ruthen ium porphyrin complexes have cyclic tetrameric structures. UV-vis spec tra of the tetramers showed broad Soret bands as compared with the res pective monomer analogues of Ru(TPP)(CO)(Py) and Ru(TPP)(Py)(2). The t etramers 1-3 underwent reactions with a large amount of pyridine to gi ve corresponding monomer complex. Sharpening and increasing intensity in the Soret bands, accompanied by the progress of the monomerization, indicated the presence of the excitonic interactions between cofacial ly arranged ruthenium porphyrin subunits in these tetrameric molecules . Electrochemical analyses revealed that the first ring-oxidation proc esses in 1 and 2, and the oxidation process of Ru(II) to Ru(III) in 3 proceed stepwise.