Ab initio calculations on first-row transition metal porphyrins. Part 1. Geometrical details, charge distributions and the effects of additional charge

From activation of dioxygen to formation of high-valent oxo species: Ab initio DFT studies

“…The calculated Mn-Cl bond length is smaller than experimentally measured, which varies between 2.363 and 2.385Å [28,29], and smaller than determined by Zwaans et al (2.553Å) by using HF approach [30]. The discrepancy between the obtained values should be attributed to the fact that LDA often underestimates bond lengths.…”

Reaction Specificity of a Titanium(IV)-Porphyrin Complex to Hydrogen Peroxide in View of an Ab Initio Study

“…Consequently, a complex composed of titanium(IV) and a porphyrin derivative, oxo [5,10,15,20-tetra(4-pyridyl)-porphyrinato]titanium(IV) complex, TiO(tpyp) shown in Fig. 1, was found to be most suitable.…”

“…Its absorbance was found to be proportional to the added hydrogen peroxide concentration with an apparent molar absorptivity for hydrogen peroxide of 1.1 × 10 5 M −1 cm −1 . This new peak was assigned to the monoperoxo [5,10,15,20-tetra(4-pyridyl)porphyrinato]-titanium(IV) complex. 4 The Ti-TPyP reagent can detect even a pico-mole level of hydrogen peroxide with no significant interferences from amino acids, proteins, and inorganic ions, 2,3,5 and organic hydroperoxides, 6 concurrently present in samples.…”

“…Therefore, we tried to clarify the reaction specificity of the TiO(tpyp) complex to hydrogen peroxide from the viewpoint of the reaction mechanisms and molecular orbitals based on ab initio calculations. [5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) complex, TiO(tpyp), was previously developed as a highly sensitive and specific reagent for determining hydrogen peroxide. In the present work, the reaction specificity of the TiO(tpyp) complex to hydrogen peroxide was clarified based on ab initio calculations.…”

“…All of the geometrical optimizations were carried out by using the RHF/STO-3G basis set, 8,9 which can be applied to large molecules in order to decrease the calculation time and cost. [10][11][12][13] All internal coordinates were optimized by means of the Berny algorithm, and convergence was tested against criteria for the maximum force component, root-mean-square force, maximum displacement component, and root-mean-square displacement.…”