The standard molar enthalpies of formation of 5,10,15,20-tetraphenylporphine and 5,10,15,20-tetrakis(4-methoxyphenyl)porphine by oxygen bomb combustion calorimetry

The standard massic energies of combustion Delta(u)u(0) at T = 298.15 K wer e determined from combustion calorimetry experiments for solid 5,10,15,20-t etraphenylporphine (TPP, Chemical Abstracts registry number 917-23-7) and 5 ,10,15,20-tetrakis (4-methoxyphenyl) porphine (TMPP, Chemical Abstracts reg istry number 221 12-7 8-3), leading to the following results: [GRAPHICS] where Delta(c)U(m)(0), Delta(c)H(m)(0), and Delta(f)H(m)(0) denote the stan dard molar energy of combustion, standard molar enthalpy of combustion, and standard molar enthalpy of formation, respectively. The values of the deri ved standard molar enthalpies of formation differ significantly from the on ly known literature results, especially for TMPP. It is concluded that the final results are strongly dependent on the purity of the samples. (C) 1999 Academic Press.