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The effects of peripheral substituents and axialigands (L) on the electronic structure and properties of cobalt tetraphenylporphyrin (CoTPP) are studied using DFT methods. The results show partial population of the (super 4)E(sub g) state in CoTPPF(sub 28)(THF)(sub 2) and CoTPPF(sub 28)(Py)(sub 2) and a complete conversion to the high-spin state in CoTPPF(sub 28)(1-Melm)(sub 2).

A theoretical study of complexes of porphyrin (P), porphyrazine (Pz), phthalocyanine (Pc), porphycene (Pn), dibenzoporphycene (DBPn) and Hemiporphyrazine (HPz) with iron (Fe) is carried out using a density functional theory (DFT) method, where the changes in the shape, size of the macrocycle has an effect on the electronic structure and properties of the overall system. The difference in the core size and shape of the macrocylce has a substantial effect on the electronic structure and properties of the overall system.

A density functional theory and a time-dependent density functional theory (DFT/TDDFT) are used to study the electronic and molecular structure and the electronic spectra of lanthanide mono- and bisorphyrin complexes, wherein the lanthanide atom sites above the porphyrin plane. The analysis gives a complete data on the UV-vis and near IR-absorption spectra of the various porphyrins and also shows that their ionization potentials can be effectively used to determine their special redox properties.

Coupled-cluster calculations with extended basis sets that include noniterative connected triple excitations (CCSD(T)) have been used to study the FOOOF isomer of F2O3. Second-order Moller−Plessett perturbation theory (MP2) and density-functional theory (B3LYP functional) calculations have also been performed for comparison. Two local minima of similar energy, namely, conformers of C2and Cssymmetry have been located. Structures, harmonic vibrational frequencies, and standard enthalpies and free energies of formation have been calculated. The calculated bond lengths of F2O3are more characteristic of those in F2O and a “normal” peroxide than the unusual bond lengths in F2O2. Both conformers have equal F−O and O−O bond lengths, contrary to a recent suggestion of an unsymmetrical structure. The harmonic vibrational frequencies can aid possible identification of gaseous F2O3. The calculated ΔfH°and ΔfG° are 110 and 173 kJ mol−1, respectively. These values are based on extrapolation of CCSD(T) results with augmented triple- and quadruple-ζ basis sets and are expected to be within chemical accuracy (i.e., 1 kcal mol−1or 4 kJ mol−1). F2O3is calculated to be stable to decomposition to either FO FOO or F2 O3, but unstable to decomposition to its elements, to F2O2 1/2O2, and to F2O O2. [ABSTRACT FROM AUTHOR]

A theoretical study has been made on six isomers of H2SO2using coupled-cluster singles and doubles with noniterative triple excitations (CCSD(T)). The isomers studied are sulfoxylic acid (S(OH)2; C2and Csconformers), sulfinic acid (HS(O)OH; 2 C1conformers), dihydrogen sulfone (H2SO2; C2v), sulfhydryl hydroperoxide (HSOOH; C1), thiadioxirane (Cs), and dihydrogen persulfoxide (H2SOO; Cs). Molecular geometries, harmonic vibrational frequencies, and infrared intensities of all species were obtained using the CCSD(T) method and the 6-311G(2d,2p) basis set. All aforementioned species were found to be local minima, with the exception of thiadioxirane, which has one imaginary frequency. A prior possible infrared observation of sulfinic acid was reassessed on the basis of the present data. In agreement with previous MP2 results, the present CCSD(T) data provide support for at most 4 of the 8 observed frequencies. The CCSD(T) frequencies and intensities should be of assistance in future identification of H2SO2isomers by vibrational spectroscopy. Relative energies were calculated using the CCSD(T) method and several larger basis sets. As found previously, the lowest energy species is C2S(OH)2, followed by CsS(OH)2, HS(O)OH, H2SO2, HSOOH, thiadioxirane, and H2SOO. Expanding the basis set significantly reduces the relative energies of HS(O)OH and H2SO2. The CCSD(T) method was used with extended basis sets (up to aug-cc-pV(Qd)Z) and basis set extrapolation in two reaction schemes to calculate the %@mt;sys@%%@ital@%H%@rsf@%%@sx@%f%@be@%o%@sxx@%%@mx@%(25 °C) of C2S(OH)2. The two reaction schemes gave −285.8 and −282.7 kJ mol-1, which are quite close to a prior theoretical estimate (−290 kJ mol-1). [ABSTRACT FROM AUTHOR]