Resonance Raman spectra of tetrapyrrole complexes of oxomolybdenum(V)

Abstract

The resonance Raman spectra of MoO(MEC) and MoO(OEP)(OMe) have been measured in the solid state. Due to low symmetry of the tetrapyrrole core, the former exhibits about 2 times more bands than the latter in the 1650-400-cm"1 region. Excitation profile studies on MoO(MEC) show that some tetrapyrrole core vibrations give maxima at the a(O-O) band and that two bands at 950 cm"1 (Mo=0 stretching) and 320 cm"1 are enhanced more than the core vibrations as the exciting frequency approaches the strong band at 455 nm. These results suggest that the 455-nm band is largely due to a ligand-metal charge-transfer transition and that the 320-cm"1 band is assignable to the Mo-N stretching vibration enhanced via such charge transfer. The spectral change caused by laser irradiation of MoO(OEP)(OMe) in the solid state has been attributed to polymerization through the formation of the methoxy bridge between two metal atoms.

Near-IR FT-Raman Spectroscopy of Methyl-B12 and Other Cobalamins and of Imidazole and Imidazolate Methylcobinamide Derivatives in Aqueous Solution

“…In studies of compounds with structures similar to those of cobalamins, , bands in this region have been attributed to corrin skeletal modes. A direct comparison of a MoO corrin and a MoO porphyrin also led to the assignment of bands in this region to CC modes. An infrared band very similar in frequency at 1568 cm -1 has also been assigned as a corrin ring mode .…”

Solvent-Dependent Resonance Raman Spectra of High-Valent Oxomolybdenum(V) Tris[3,5-bis(trifluoromethyl)phenyl]corrolate

“…46 However, in contrast to extensively studied biological, geological, and synthetic metalloporphyrin systems, [47][48][49][50][51] including highvalent metalloporphyrin oxides, [52][53][54][55][56][57] only sparse RR spectra have been reported for metallocorroles. [58][59][60][61] In particular, there appears to be only one such work on tetrapyrrole complexes of oxomolybdenum(V) published in 1979, in which Nakamoto and co-workers measured the RR spectra of Mo V O(MEC) (MEC ) 2,3,17,18-tetramethyl-7,8,12,13tetraethylcorrole) and Mo V O(OEP)(OMe) (OEP ) octaethylporphyrin) in the solid state. 58 Both Mo V O(MEC) and Mo V O(OEP)(OMe) showed relatively strong RR bands at 950 and 910 cm -1 , respectively, in the 457.9-nm excitation spectra that have been assigned to the Mo V -O stretching mode, ν(Mo V O).…”

“…[58][59][60][61] In particular, there appears to be only one such work on tetrapyrrole complexes of oxomolybdenum(V) published in 1979, in which Nakamoto and co-workers measured the RR spectra of Mo V O(MEC) (MEC ) 2,3,17,18-tetramethyl-7,8,12,13tetraethylcorrole) and Mo V O(OEP)(OMe) (OEP ) octaethylporphyrin) in the solid state. 58 Both Mo V O(MEC) and Mo V O(OEP)(OMe) showed relatively strong RR bands at 950 and 910 cm -1 , respectively, in the 457.9-nm excitation spectra that have been assigned to the Mo V -O stretching mode, ν(Mo V O). However, no confirmation of such a band assignment had been obtained via the 18 O-isotope-edited vibrational spectra.…”

Metalloporphyrin receptors for bases

“…The attack of HO 2 -that is generated in the course of establishment of equilib ria (44) and (48) on the coordination site of the radi cal cation manganese(III) complex facilitates the slow transformation according to Eq. (47). Due to a low con centration of manganese porphyrin in the form of (Cl)O=Mn IV (TPP +• ), no gas evolution was observed in the experiment, and O 2 that was formed apparently re mained in solution.…”