SYNTHESIS AND ELECTROCHEMICAL CHARACTERIZATION OF RUTHENIUM PORPHYRINS CONTAINING A BOUND PF3 AXIAL LIGAND

The first synthesis and electrochemistry of metalloporphyrins containi ng a bound PF, axial ligand has been achieved. The investigated compou nds are [Ru(por)(PF3)] where por is the dianion of 5,10,15,20-tetraphe nyl-, -tetra(p-bromophenyl)-, -tetra(p-methoxyphenyl)-, 2,7,12,17-tetr aethyl-3,8,13,18-tetramethyl- or 2,3,7,8,1 2,13,17,18-octaethyl-porphy rin. Each [Ru(por)(PF3)] species was investigated with respect to its spectroscopic and electrochemical properties and the resulting data co mpared with those for [Ru(por)(CO)] having the same porphyrin ring. A number of similarities exist between the carbonyl and PF3 derivatives in methylene chloride but major differences can be observed in other n on-aqueous solutions. The first reduction of each complex is reversibl e in tetrahydrofuran (thf) and leads to a porphyrin pi-anion radical r ather than a ruthenium(I) species as identified by UV/VIS spectroelect rochemistry. Each investigated complex also undergoes two reversible o xidations in dichloromethane, the first of which leads to a porphyrin pi-cation radical. The [Ru(por)(PF3)] derivatives appear to be more st able than the [Ru(por)(CO)] analogues in thf or CH2Cl2, but an electro chemically initiated conversion of [Ru(II)(por)(PF3)(PY)] into [Ru(III )(por)(py)2]+ can be readily accomplished in pyridine (py) or CH2Cl2-p yridine mixtures. This type of reaction has never been seen upon oxida tion of a ruthenium(II) porphyrin and was monitored by cyclic voltamme try and UV/VIS spectroelectrochemistry.