Journals

Reversible Binding of Dioxygen to Ruthenium(II) Porphyrins

Solutions of porphyrin (H2L) complexes, RuL(MeCN)2, in MeCONMe2, DMF, or pyrrole, bind 1.0 mol of O2 per Ru reversibly at 20 oC and 1 atm pressure. The MeCN complexes are prepared by photolysis of the corresponding RuL(CO)(EtOH), complexes in MeCN. In PhMe solution, the O2 reaction leads only to a slow irreversible oxidation to Ru(III). Related complexes with more strongly coordinated axial ligands, such as pyridine and N-methylimidazole, also give only oxidation products. Electrolysis of the bisacetonitrile complex brings about a reversible 1-electron oxidation to give a Ru(III) cation.

Interaction of the Hemin 2 and 4 Substituents with Apo Horseradish Peroxidase

2-Formyl-4-vinyl-deuterohemin- and 2-vinyl-4-formyl-deuterohemin-substituted horseradish peroxidase were prepared from apoperoxidase and the respective hemins. The 2 hemins bind at different rates to the apoprotein and the resultant substituted peroxidases possess different visible spectra and activities. Thus, the hemin 2 and 4 substituents interact with apoperoxidase and are not exposed to the solvent.

Exciton and Electron Interaction in Covalently-linked Dimeric Porphyrins

The interactions between dimeric porphyrins I (n = O-8), covalently linked at their peripheries, were measured from their electronic absorption spectra and 13C NMR spectra. For I (n less than 2), interactions between the 2 rings are observed; for I (n greater than 2), the interactions decrease.

Phthalocyanine Complexes of Ruthenium(II)

Heating a mixture of RuCl3H2O and o-cyanobenzamide in naphthalene to 290 oC for 1 h, followed by cooling, addition of EtOH to the residue, filtering the suspension, and drying gave a solid residue which was Soxhlet-extracted with glacial HOAc, dried, and reextracted with pyridine or its derivatives to give RuPcL2 (I; H2Pc = phthalocyanine, L = pyridine, 4-methylpyridine, 4-tert-butylpyridine). CO was bubbled through a refluxing solution of RuPcL2 in diglyme to give RuPcL(CO) (II). Refluxing of Ru3(CO)12 and PcH2 in PhCN gave a dark blue solid, probably RuPc(CO), which upon Soxhlet extraction with pyridines gave II also.

Porphyrins. 38. Redox Potentials, Charge Transfer Transitions, and Emission of Copper, Silver, and Gold Complexes

While CuII porphyrins are known to luminescence, AgII complexes do not. AgIII octethylporphyrin has no emission while AuIII tetraphenylporphyrin has a moderabely intense phosphorescence with a nonexponential decay fit with 2 decay times of 63 and 184 μs. In contrast to CuII porphyrins, the Ag complexes have a metal redox potential, II to III, between that of ring oxidation and ring reduction suggesting that luminescence is quenched by low-energy charge transfer transitions AgII → ring or ring → AgIII. Near-IR (700-1100 nm) absorption spectra confirm the presence of weak absorption bands in AgII and AgIII complexes that are not observed in complexes of CuII and AuIII. The near-IR absorption of CuII(TPP) and the quenching of its unusually broad emission by pyridine suggest that a charge transfer state is close to the emitting level. Iterative extended Huckel calculations explain these facts by the energy of orbital b1g(dx2-y2), which rises along the series Cu < Ag < Au.

Copper Coproporphyrin Excretion in Familial Coproporphyria

Analysis of stool specimens from a patient with familial coproporphyria by high-performance liquid chromatography revealed that 112 μg/g of dry feces (14% of the total porphyrin present) was Cu coproporphyrin. Examination of stool specimens from other patients with this disease confirmed the presence of significant amtounts of both Cu coproporphyrin and coproporphyrin. Further investigation showed that the Cu coproporphyrin was probably formed by a nonenzymic incorporation of Cu in either the bile or feces.

Iron Porphyrin Phenoxides: Models for Some Hemoglobin Mutants

Variously substituted phenoxides (L) react with [Fe(PPIXDBE)]2O (PPIXDBE is protoporphyrin IX di-tert-Bu ester dianion) to produce 5-coordinate high-spin complexes Fe(PPIXDBE)L which display spectroscopic properties similar to those of the Met form of the α mutant chain of Hb M Boston. The addition of pyridine or 1-methylimidazole (L') to Fe(PPIXDBE)L at 77 oK produced low-spin 6-coordinate complexes Fe(PPIXDBE)LL' which were studied spectroscopically. With the strongly basic 2,6-dimethoxyphenoxide (L), the above reaction was studied at 298 oK, where for L' = 1-methylimidazole the binding constant was approximately 100 M-1 in CH2Cl2. The Fe(PPIXDBE)LL' complexes were made in an attempt to mimic the Fe(III) in the αchain of Met Hb M Iwate; however, the latter is high spin. With excess p-nitrophenoxide in CH2Cl2, Fe(PPIXDBE)(OC6H4-4-NO2) forms Fe(PPIXDBE)(OC6H4 -4-NO2)2-, which exhibits a high-spin EPR spectrum at 77 oK. Addition of phenoxides or F- to Fe(II)

99mTc-Glutathione: Role of Reducing Agent on Renal Retention

The biodistribution of 99mTc-labeled glutathione in mice was dependent on the presence of Sn2+. The radioactivity ratio of the kidney to the liver increased from 1.17 to >6.0 as the Sn2+ ion concentration in the glutathione injection solution increased from 0 to 1.11 mM. The activity in the kidneys increased for the 1st 2 h and then decreased for 4 h. In the absence of the Sn2+, the radioactivity in the liver, kidney, and blood decreased 30 min after administration. Apparently, the reducing agent Sn2+ increases the retention of glutathione in the kidney.

Pyrrole

A review, in Italian, with 82 references describing the properties, synthesis and biochemistry of pyrroles.