60166-10-1Relevant articles and documents
Laser photolysis studies on photodissociation of axial ligands from isocyanide complexes of cobalt(III) and rhodium(III) porphyrins in toluene solutions. A comparison with the photochemistry of carbonylrhodium(III) porphyrin
Hoshino, Mikio,Nagamori, Takahiro,Seki, Hiroshi,Tase, Takahiro,Chihara, Teiji,Lillis, Jerome P.,Wakatsuki, Yasuhiro
, p. 3672 - 3677 (1999)
Chlorocobalt(III) and iodorhodium(III) tetraphenylporphyrins, (Cl)CoIIITPP and (I)RhIIITPP, react with 2,6-dimethylphenyl isocyanide (R-NC) in toluene solutions to give the isocyanide complexes, (Cl)(R-NC)-CoIIITPP and (I)(R-NC)RhIIITPP, respectively. The 355-nm laser photolysis studies have shown that these complexes photodissociate the axial ligand, R-NC. The quantum yield, φ, for the photodissociation of R-NC from (Cl)(R-NC)CoIIITPP is determined as 0.091 in both degassed and oxygen-saturated toluene. On the other hand, (I)(R-NC)RhIIITPP gives φ = 0.19 in degassed toluene and φ = 0.07 in oxygen-saturated toluene. The dissociation of R-NC from (I)(R-NC)RhIIITPP was confirmed to occur from both the excited singlet and triplet states by transient spectroscopic measurements. The small quantum yield obtained with the oxygen-saturated solution is explained by the quenching of the triplet state, 3(π,π*) of (I)(R-NC)RhIIITPP. The triplet state decays with a rate constant 9.5 × 104 s-1 in degassed toluene and is effectively quenched by oxygen with a bimolecular rate constant 6.7 × 108 M-1 s-1. In comparison with (I)(R-NC)RhIIITPP, the lifetime of the 3(π,π*) state of (Cl)(R-NC)CoIIITPP is too short to be detected by the present laser photolysis system, probably because of the very fast radiationless process, 3(π,π*) → 3(π,dz2) → 3(dπ,dz2). The dissociation of R-NC from (Cl)(R-NC)CoIIITPP is assumed to occur from the 3(dπ,dz2) state. The long lifetime of the 3(π,π*) state of (I)(R-NC)RhIIITPP is interpreted on the assumption that the 3(dπ,dz2) is located higher in energy than the 3(π,π*) state. The dissociation of R-NC from (I)(R-NC)RhIIITPP at the triplet state is suggested to occur from the thermally populated 3(dπ,dz2) state. The laser photolysis studies of carbonyl-rhodium(III) tetraphenylporphyrin are also described to elucidate the ligand dissociation mechanism of rhodium(III) porphyrins.
A flexible bis-Co(III) porphyrin cage as a bimetallic catalyst for the conversion of CO2 and epoxides into cyclic carbonates
Schoepff, Laetitia,Monnereau, Laure,Durot, Stéphanie,Jenni, Sébastien,Gourlaouen, Christophe,Heitz, Valérie
, p. 5826 - 5833 (2020/09/22)
A molecular cage consisting of two free-base porphyrins connected by four flexible linkers was metalated with Co(III) to afford in good yield a bimetallic catalyst. The catalytic activity of the bis-Co(III) porphyrin molecular cage (CoCl)2-1 was studied for the formation of cyclic carbonates from CO2 and propylene oxide (PO) or styrene oxide (SO) with pyridine as cocatalyst. Various reaction parameters such as the molar ratio of the catalyst and the co-catalyst, the time of reaction, the temperature and CO2 pressure were investigated. The molecular cage was shown to be a catalyst of high selectivity for the studied reactions and much more efficient to convert the epoxides to the corresponding cyclic carbonates than the monomeric Co(III)Cl meso-tetraphenylporphyrin (CoCl-TPP) model. When quantitative conversion of PO into propylene carbonate (PC) was reached (0.1 mol% catalyst, 1.2 mol% pyridine, 120 °C, 30 bar of CO2) only 23 % of PC was obtained with CoCl-TPP (0.2 mol%). This enhanced catalytic activity is attributed to the synergistic effect of the two metal sites incorporated in the framework of the molecular cage.
Design of oxophilic metalloporphyrins: An experimental and DFT study of methanol binding
Olsson, Sandra,Dahlstrand, Christian,Gogoll, Adolf
supporting information, p. 11572 - 11585 (2018/08/28)
By systematic measurements we have evaluated a series of tetraphenyl metalloporphyrins and halogenated tetraphenyl metalloporphyrin derivatives for binding to ligands with oxygen containing functional groups, using methanol, acetic acid and acetone as examples. Experimental binding constants identified three metalloporphyrins with good binding to all three ligands: MgTPFPP, MgTPPBr8 and ZnTPPBr8 as well as a range of porphyrins binding to select ligands. Based on these results the optimal porphyrins can be selected for the desired binding interactions. We also show how to use DFT calculations to evaluate the potential binding between a metalloporphyrin and a ligand, which is deduced from free energies of binding ΔG, charge transfer ΔQ, and change of metal spin state. Computations on unsubstituted porphyrins in lieu of tetraphenyl porphyrin systems yield reliable predictions of binding interactions with good correlation to the corresponding experimental data. The calculations have also yielded interesting insights into the effect of halogenation in the β-position on the binding to ligands with oxygen containing functional groups.
