The electronic structure and magnetic property of metal‐oxo, porphyrin manganese‐oxo, and μ‐oxo‐bridged manganese porphyrin dimer

Abstract

ABSTRACT:Hybrid density functional theory (HDFT) and post Hartree-Fock CCSD(T) methods are applied to elucidate the binding energies and the optimized MOO distances of transition metal oxides: MO (M ϭ Cr, Mn, Fe, Co, Ni, Cu). The HDFT method can reproduce the CCSD(T) results, in agreement with the experimental ones. The nature of the manganese-oxygen bonds in the Mn(VI)OO, Mn(IV)OO porphyrin (PP), and Mn(V)OO PP systems are examined in relation to possible mechanisms of oxygen evolution from H 2 O 2 and H 2 O in native and non-native manganese complexes. It is found that the radical character of the high-valent (PP)Mn(V)OO bond is remarkable, showing the strong potential to generate molecular oxygen because of its high reactivity. The electronic structure and magnetic property of -oxo-bridged manganese porphyrin dimer (PPMn(III)OMn(III)PP) are investigated for further discussion of structure and reactivity of PPMn(X)O (X ϭ II-IV). The potential curve for release of molecular oxygen from PPMn(II)O 2 is also examined to show weak affinity of O 2 in the Mn complex where the oxidation number (X) of Mn is low. Implications of the computational results are also discussed in relation to oxygen evolution reactions.

The Electronic Structure of [Mn(V)═O]: What is the Connection between Oxyl Radical Character, Physical Oxidation State, and Reactivity?

“…The CASSCF calculation is in reasonably good agreement with the B3LYP results and a diradical character of 36% is calculated. The largest diradical character calculated with any method or complex is 54% for 2 with B3LYP, which is in reasonable agreement with DFT results previously reported by Yamaguchi on Mn V O oxo complexes, where the formal diradical character was found to be under ∼50%, − based on y corr values. Typically, the y corr parameters are significantly smaller than y .…”

Enhancement of the Third-Order Nonlinear Optical Properties in Open-Shell Singlet Transition-Metal Dinuclear Systems: Effects of the Group, of the Period, and of the Charge of the Metal Atom

“…Although multireference methods such as complete-active-space SCF (CASSCF), CAS with second-order perturbation (CASPT2), and multireference second-order Møller–Plesset perturbation (MRMP2) are often used for calculating geometries, energies, properties, and occupation numbers of such systems, , they are hard to be applied to the γ calculations of the present open-shell systems because of the very slow convergence of γ as a function of the size of the active space as well as of the very demanding computational resources for extending the active space. An alternative way to approximately treat static correlation effects in open-shell molecular systems is the use of the broken symmetry-based strong correlated methods, e.g., the spin-unrestricted-based CC methods, which can include high-order electron correlation effects without suffering from significant spin contaminations. , Therefore, we employed the UCCSD and UCCSD(T) methods for the calculation of γ. In addition, the relativistic effects are taken into account using the ECPs of the SDD and SDD(f) basis sets, which have been shown to reproduce well the Dirac–Hartree–Fock second hyperpolarizability results obtained with an all-electron basis set .…”

Generation and dissociation of oxygen‐ and chloride‐bridged iron(III) and manganese(III) tetraphenylporphyrin dimer ions in the gas phase

“…Other aspects of oxygen‐bridged ironporphyrins also have been investigated, including magnetic properties,18–20 formation mechanisms,10, 15 thermodynamic and kinetic properties,12 and electrochemical properties 21–23. Also, there has been some interest in the structural and magnetic properties of related O24 and OH − 25 bridged manganeseporphyrin dimers since (OH) 2 ‐and O 2 ‐bridged manganeseporphyrin dimers have been suggested to be formed in the evolution of oxygen from water during photosynthesis 26…”