Jonghyuk Lee

Fiber-optic infrared reflectance spectroelectrochemical studies of osmium and ruthenium nitrosyl porphyrins containing alkoxide and thiolate ligands

We have examined the redox behavior of the osmium and ruthenium compounds (OEP)M(NO)(OEt) and (OEP)M(NO)(SEt) (OEP = octaethylporphyrinato dianion; M = Os, Ru) by cyclic voltammetry and infrared spectroelectrochemistry. The compound (OEP)Os(NO)(OEt) undergoes a single reversible oxidation process in dichloromethane. In contrast, the thiolate compound (OEP)Os(NO)(SEt) undergoes a net irreversible oxidation resulting in formal loss of the SEt ligand. Extended Hückel calculations on crystal structures of these two compounds provide insight into the nature of their HOMOs. In the case of the alkoxide compound, the HOMO is largely metal centered, with 70% of the charge located in the metals orbital and approximately 25% on the porphyrin ring. However, the HOMO of the thiolate compound consists of a pi bonding interaction between the metal dxz orbital and the px orbital on the sulfur, and a pi antibonding interaction between the metal d orbital and a pi* orbital on NO. The redox behavior of the Ru analogues have been determined, and are compared with those of the Os compounds.

Synthesis, characterization and molecular structures of six-coordinate manganese nitrosyl porphyrinsElectronic supplementary information (ESI) available: Molecular structure of (TTP)Mn(NO)(1-MeIm). See http://www.rsc.org/suppdata/dt/b3/b308143p/

Manganese(II) porphyrins are isoelectronic with iron(III) porphyrins, and previously reported work suggests that manganese nitrosyl porphyrins are good structural models for their kinetically unstable and biologically relevant ferric-NO analogues. We have prepared a new set of six-coordinate manganese nitrosyl porphyrins of the general form (por)Mn(NO)(L)(por = TTP, T(p-OCH3)PP; L = piperidine, methanol, 1-methylimidazole) in moderate to high yields. The (por)Mn(NO)(pip) complexes were prepared from the reductive nitrosylation of the (por)MnCl compounds with NO in the presence of piperidine. The IR spectra of the (por)Mn(NO)(pip) compounds as KBr pellets show new strong bands at 1746 cm(-1)(for TTP) and 1748 cm(-1)(for (T(p-OCH3)PP) due to the NO ligands. Attempted crystallization of one of these compounds (por = TTP) from dichloromethane-methanol resulted in the generation of the methanol complex (TTP)Mn(NO)(CH3OH). Reaction of the (por)Mn(NO)(pip) compounds with excess 1-methylimidazole gave the (por)Mn(NO)(1-MeIm) derivatives in good yields. The IR spectra of these compounds show nu(NO) bands that are approximately 12 cm(-1) lower than those of the (por)Mn(NO)(pip) precursors, indicative of greater Mn-->NO pi-backdonation in the 1-MeIm derivatives. X-Ray crystal structures of three of these compounds, namely (TTP)Mn(NO)(CH3OH), (TTP)Mn(NO)(1-MeIm) and (T(p-OCH3)PP)Mn(NO)(1-MeIm) were obtained, and reveal that the NO ligands in these complexes are linear.

Nitrones are suitable ligands for heme models: X-ray crystal structure of the first metalloporphyrin nitrone complex

The metalloporphyrin nitrone complexes [M(oep)-(CO)(DMPO)] (M = Ru, Os; oep = octaethylporphyrinato dianion; DMPO = 5,5-dimethyl-1-pyrroline N-oxide) have been prepared: the crystal structure of the Ru complex reveals a sole eta 1-O binding mode of the nitrone ligand to the metal center.

μ-Oxo-bis­[(protoporphyrin IX di­methyl ester)­iron(III)]

In the title compound, [Fe2(C36H36N4O4)2O], the Fe—O—Fe bond angle is 170.5 (2)° and the two porphyrin rings are twisted by 27.2 (4)° with respect to each other.

Metallodithiolato ligands as bridges in multiply bonded dimolybdenum complexes

For the first time, a NiN2S2 metallothiolate ligand is used as a bidentate bridging ligand for a multiply bonded dimetal unit.

Synthesis and molecular structures of nitrosoarene metalloporphyrin complexes of ruthenium

Several new ruthenium porphyrins containing nitrosoarene ligands have been synthesized and characterized by IR and (1)H NMR spectroscopy, and by single-crystal X-ray crystallography. Bis-nitrosoarene complexes of the form (por)Ru(ArNO)(2)(Ar = aryl group; por = TPP, TTP; TPP = tetraphenylporphyrinato dianion, TTP = tetratolylporphyrinato dianion) were prepared in good yields from the reaction of the nitrosoarenes with (por)Ru(CO). The IR spectra of the complexes (as KBr pellets) display new bands in the 1346-1350 cm(-1) region due to nu(NO). Reactions of the (por)Ru(ArNO)(2) complexes with excess pyridine and 1-methylimidazole produce the mono-nitrosoarene complexes (por)Ru(ArNO)(py) and (por)Ru(ArNO)(1-MeIm), respectively. The IR spectra of these mono-nitrosoarene complexes reveal a lowering of nu(NO) by 14-44 cm(-1), a feature consistent with the replacement of one of the pi-acid ArNO ligands with the more basic pyridine and 1-MeIm ligands. The solid-state molecular structures of two members of each of the three classes of compounds, namely (por)Ru(ArNO)(2), (por)Ru(ArNO)(py) and (por)Ru(ArNO)(1-MeIm) were determined by single-crystal X-ray diffraction, and reveal the N-binding mode of the ArNO ligands.