SYNTHESIS, STRUCTURAL CHARACTERIZATION, AND METALATION OF N-O-TOLYL-5,10,15,20-TETRAPHENYLPORPHINE - DEFORMATION EFFECT DUE TO A BULKY N-SUBSTITUENT GROUP

The tetraphenylporphyrin with a bulky N-substituent group, N-o-tolyl-5,10,15,20-tetraphenylporphine (H(o-TolTPP)) has been synthesized and characterized by H-1 NMR spectroscopy, secondary ion mass spectrometry, UV-visible spectrophotometry, and an X-ray crystal structure analysis. The free base porphyrin (H(o-TolTPP).1/2C6H6.1/2NC4H11) crystallizes in the triclinic space group P1BAR with Z = 2 and lattice parameters a = 9.054(1) angstrom, b = 15.369(4) angstrom, c = 16.963(3) angstrom, alpha = 70.30(1)-degrees, beta = 75.64(1)-degrees, gamma = 89.42(2)-degrees, V = 2145(15) angstrom3. The final R value is 0.092. The assignment and characterization of the H-1 NMR signals have been confirmed on the basis of its crystal structure. The N-substituted pyrrole ring is tilted from the N1-N2-N4 reference porphyrin plane by 57.3(2)-degrees and three other pyrrole rings by -19.3(2)-degrees, 1.6(10), and -16.4(2)-degrees, respectively. The porphyrin ring system for H(o-TolTPP) is highly distorted from planarity in comparison with that for the N-methylated porphyrin. The kinetics for metalation of H(o-TolTPP) with zinc(II) ion revealed that the distortion of the porphine core is favorable to the complexation rate. The second-order rate constant at 25-degrees-C and activation parameters are as follows: k = 35 +/- 1 mol-1 kg s-1, DELTAH double dagger = 39 +/- 2 kJ mol-1, and DELTAS double dagger = -88 +/- 6 J K-1 mol-1. The kinetic properties are discussed in terms of steric effects.