75888-63-0Relevant academic research and scientific papers
Synthesis and Electrochemical Characterization of Ruthenium Porhyrins containing a Bound PF3 Axial Ligand
Kadish, Karl M.,Hu, Yu,Tagliatesta, Pietro,Boschi, Tristano
, p. 1167 - 1172 (1993)
The first synthesis and electrochemistry of metalloporphyrins containing a bound PF3 axial ligand has been achieved.The investigated compounds are where por is the dianion of 5,10,15,20-tetraphenyl-, -tetra(p-bromophenyl)-, -tetra(p-methoxyphenyl)-, 2,7,12,17-tetraethyl-3,8,13,18-tetramethyl- or 2,3,7,8,12,13,17,18-octaethyl-porphyrin.Each species was investigated with respect to its spectroscopic and electrochemical properties and the resulting data compared with those for 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 non-aqueous solutions.The first reduction of each complex is reversible in tetrahydrofuran (thf) and leads to a porphyrin ?-anion radical rather than a ruthenium(I) species as identified by UV/VIS spectroelectrochemistry.Each investigated complex also undergoes two reversible oxidations in dichloromethane, the first of which leads to a porphyrin ?-cation radical.The derivatives appear to be more stable than the analogues in thf or CH2Cl2, but an electrochemically initiated conversion of II(por)(PF3)(py)> into III(Por)(py)2>(1+) can be readily accomplished in pyridine (py) or CH2Cl2-pyridine mixtures.This type of reaction has never been seen upon oxidation of a ruthenium(II) porphyrin and was monitored by cyclic voltammetry and UV/VIS spectroelectrochemistry.
Redox Properties of Metalloporphyrin Excited States, Lifetimes, and Related Properties of a Series of Para-Substituted Tetraphenylporphine Carbonyl Complexes of Ruthenium(II)
Rillema, D. P.,Nagle, J. K.,Barringer, L. F.,Meyer, T. J.
, p. 56 - 63 (2007/10/02)
Excited-state and redox properties of Ru(p-XTPP)(CO), X = MeO, Me, H, F, Cl, H, and Br, have been defined.Emission bands were centered at 730 +/- 3 nm and excited-state lifetimes were in the range of 30 +/- 10 μs.Two one-electron oxidations in CH2Cl2 ranged from 0.74 to 0.86 V for the first step and from 1.18 to 1.27 V for the second one.A one-electron reduction process in (CH3)2SO ranged from -1.35 to -1,24 V.Excited-state lifetimes and redox potentials exhibit a weak dependence on the Hammet ?p function.In general, redox potentials increase as the electron-withdraving power of the substituents increases, whereas excited-state lifetimes decrease.The first oxidation step (0.74-0.86 V) and the reduction step are, respectively, assigned to ?-electron removal or acceptance by porphyrin ring.The second oxidation is assigned to removal of an electrone from the ruthenium(II) center.The excited state is shown to be T(?-?*) state of porphyrin ring and to exhibit photoredox behavior involving both oxidative and reductive quenching.Redox product separation occured in flash photolysis quenching experiments and back-reactions took place at near-diffusion-controlled rates.The redox potential of the Ru(TPP)(CO)+/* couple was estimated from emission and redox data to be -0.57 +/- 0.03 V; it was determined from oxidative quenching studies to be -0.56 +/- 0.10 V.Comparison to the excited-state properties of Ru(bpy)32+ is made, and the utility of porphyrin complexes as potential solar energy storage catalysts is examined.
