41751-82-0Relevant articles and documents
Separation of contributions to the third-order signal: Ultrafast frequency-selected vibrational echo experiments on a metalloporphyrin-CO
Xu, Qing-Hua,Thompson, David E.,Merchant,Fayer
, p. 139 - 146 (2002)
One-dimensional and frequency-selected vibrational echo experiments on the CO stretching mode of a metalloporphyrin carbonyl compound (model heme) in poly-methylmethacrylate (PMMA) and in 2-methylteterahydrofuran (2-MTHF) are compared. Spectrally resolving the vibrational echo signal and observing the decay at selected wavelengths, permits the independent detection of the 0-1 and 1-2 vibrational level dephasing dynamics, eliminating cross terms and anharmonic beats. In the high temperature 2-MTHF liquid, 0-1 and 1-2 dephasing dynamics are identical within experimental error. The decays are non-exponential, demonstrating that the CO stretching mode absorption spectrum is not a completely homogeneous, motionally narrowed line.
Synthetic and mechanistic aspects of a new method for ruthenium-metalation of porphyrins and Schiff-bases
Reboucas, Julio S.,Cheu, Elizabeth L. S.,Ware, Caroline J.,James, Brian R.,Skov, Kirsten A.
, p. 7894 - 7907 (2009/02/08)
A new method is presented for metalation of a wide range of free-base, neutral, cationic, and anionic porphyrins in refluxing dimethylformamide (DMF) using an easily prepared [Ru(DMF)6](OTf)3 complex, and comparisons are made with the more familiar metalation procedure using Ru 3(CO)12. Both procedures generate RuII(porp) (CO)L complexes (L = solvent); use of the RuIII-triflate precursor gives yields comparable to, or greater than, those obtained with the carbonyl, and generates no Ru-chlorin impurities. Mechanistic studies on the meso-tetraphenylporphyrin system reveal that the DMF furnishes the CO, which in the presence of essential water reduces the metal, and metalation likely occurs via a RuII-CO species. Corresponding metalation of tetradentate Schiff-bases gives trans-[RuIII(Schiff- base)(DMF)2]OTf complexes in yields of ～50%, a limitation being the accompanying hydrolysis of the Schiff-base through the presence of trace water.
Axial-Ligand Control of the Photophysical Behavior of Ruthenium(II) Tetraphenyl- and Octaethylporphyrin. Contrasting Properties of Metalloporphyrin (?,?*) and (d,?*) Excited States
Levine, Leanna M. A.,Holten, Dewey
, p. 714 - 720 (2007/10/02)
The photophysical behavior of the ruthenium(II) porphyrins depends dramatically on the axial ligands coordinated to the central metal ion.We have measured the picosecond and slower time scale transient absorption spectra and kinetics, emission data, and ground-state absorption spectra for two classes of complexes: RuP(CO)(L) and RuP(L)2.Results are compared for complexes in which the porphyrin macrocycle (P) is tetraphenylporphyrin (TPP) or octaethylporphyrin (OEP) and the axial ligand L is piperidine (pip), pyridine (py), dimethyl sulfoxide (Me2SO), or ethanol (EtOH).We assign the lowest excited state of all the RuP(CO)(L) complexes, including those with L absent, as the lowest excited triplet state 3(?,?*), of the porphyrin ring 3(?,?*) appears to form in high yield from the ring excited singlet, 1(?,?*), in a metal-to-ring (d,?*) charge-transfer (CT) state.We attribute this general switch of the lowest excited state from 3(?,?*) in RuP(CO)(L) to (d,?* in RuP(L)2 to the loss of ?-backbonding between the filled Ru(d?) orbitals and the empty CO(?*) orbitals.The loss of axial ?-backbonding is expected to destabilize the d? orbitals, making them closer in energy to the empty eg(?*) orbitals of the porphyrin ring.This lowers the energy of (d,?*) relative to 3(?,?*) in RuP(L)2 compared to RuP(CO)(L).Although 3(?,?*) appears to be the lowest excited state in all the RuP(CO)(L) complexes investigated, we propose that the deactivation of this state nonetheless proceeds, in part, via a shorter lived (d,?*) state at higher energy.We speculate that the faster decay of (d,?*) compared to 3(?,?*) may be due to a better Franck-Condon factor for radiationless decay to the ground state.The recay route of 3(?.?*) via a thermally accessible (d,?*) in the RuP(CO)(L) complexes also may be the pathway for photodissociation of CO from these molecules, which in the presence of L results in the formation of RuP(L)2.The photodissociation quantum yield is measured to be ca. 1E-4 for two of the complexes.
