Meso-Tetraphenylporphyrin solvents

Solubility of meso-Tetraphenylporphyrin in Two Supercritical Fluid Solvents... 

Solubilities of meso-tetraphenylporphyrin (normal melting temperature 444°C) in pentane and in toluene have been measured at elevated temperatures and pressures. Three-phase, solid-liquid-gas equilibrium temperatures and pressures were also measured for these two binary mixtures at conditions near the critical point of the supercritical-fluid solvent. The solubility of the porphyrin in supercritical toluene is three orders of magnitude greater than that in supercritical pentane or in conventional liquid solvents at ambient temperatures and pressures. An analysis of the phase diagram for toluene-porphyrin mixtures shows that supercritical toluene is the preferred solvent for this porphyrin because (1) high solubilities are obtained at moderate pressures, and (2) the porphyrin can be easily recovered from solution by small reductions in pressure. 

Rate constants and activation parameters for the axial ligation of zinc(II) meso -tetraphenylporphyrin by pyridine, 2-methylpyridine, and imidazole in aprotic solvents are close to, but significantly different from, the diffusion-controlled values, and it appears that desolvation (either of the base or the metalloporphyrin) is an important step in these reactions. 

In 1978, a new approach by the team of D. Dolphin (244) at the University of British Columbia has been taken in devising molecular models that mimic the reversible binding of molecular oxygen by heme. They have successfully incorporated ruthenium(II) into meso-tetraphenylporphyrin and octaethyl-porphyrin systems. They found that these porphyrin systems complexed with two molecules of the solvent but only one molecule of oxygen per ruthenium atom is absorbed reversibly at 25 °C and at 1 atm in DMF. The group also has made monocarbonyl and dinitrogen (one N2 molecule) species reversibly in polar aprotic solvents. Therefore, these new systems parallel that of corresponding Fe(II) systems, but at more convenient temperatures. 

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