Y. Shao et al., A STUDY OF THERMODYNAMICS IN AXIAL COORDINATION REACTION OF UNSYMMETRICAL DERIVATIVES OF TETRAPHENYLPORPHYRINATOCOBALT(II), Gaodeng xuexiao huaxue xuebao, 18(10), 1997, pp. 1571-1575
-(4-Acetamidophenyl)-10,15,20-tris(4-methylphenyl) porphyrinatocobalt(
II) was synthesized. BY means of spectrophotometer technique, the equi
librium constants of the axial coordination reaction were measured bet
ween this system and a series of imidazole ligands (2-MeIm, N-MeIm, EM
Im, GMZ) which possess different steric hindrances. The results show t
hat the size and the position of the substituting group on a ligand in
fluence the stability of the axial coordinative product, and the equil
ibrium constants appear in the order K-GMZ>KN-MeIm>K2-MeIm>K-EMIm. A l
inear relationship was observed between Delta H and T Delta S in both
the symmetrical and unsymmetrical systems. The favorable enthalpy chan
ge compensates the unfavorable entropy change and the compensatory ent
halpy-entropy relationship contributes to the stability of complexes.