Christoph Riplinger

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α-Ketoglutarate (αKG)-dependent nonheme iron enzymes utilize a high-spin (HS) ferrous center to couple the activation of oxygen to the decarboxylation of the cosubstrate αKG to yield succinate and CO(2), and to generate a high-valent ferryl species that then acts as an oxidant to functionalize the target C-H bond. Herein a detailed analysis of the(More)
[Re(bpy)(CO)3](-) is a well-established homogeneous electrocatalyst for the reduction of CO2 to CO. Recently, substitution of the more abundant transition metal Mn for Re yielded a similarly active electrocatalyst, [Mn(bpy)(CO)3](-). Compared to the Re catalyst, this Mn catalyst operates at a lower applied reduction potential but requires the presence of a(More)
A detailed QM/MM study on the reaction mechanism of Cytochrome P450 NO reductase is reported. Two reaction pathways connecting the two well-characterized intermediates as well as two putative intermediates that represent the unknown third intermediate are explored, with emphasis on the unusual direct reduction of the enzymatic active site by the cofactor(More)
The binding of NO to reduced myoglobin in solution results in the formation of two paramagnetic nitrosyl myoglobin (MbNO) complexes: one with a rhombic g-factor and the other with an axial one, referred to as the R- and A-forms. In spite of past extensive studies of MbNO by crystallography, spectroscopy and quantum chemical calculations it is still not(More)
Adsorbed protons that develop hydride character have been proposed to play a role in the mechanism of CO2 reduction catalyzed by pyridine on GaP photoelectrodes. Investigating their stability represents an important step towards vetting this mechanism. In this contribution, the relative stability of the adsorbed protons is determined using cluster models(More)
Inelastic neutron scattering and high-field electron paramagnetic resonance data are presented for [Mn(bpia)(OAc)(OCH(3))](PF(6)), where bpia is bis(picolyl)(N-methylimidazole-2-yl)amine. Modeling of the data to the conventional fourth-order spin-Hamiltonian yielded the following parameters: D = 3.526(3) cm(-1), E = 0.588(6) cm(-1), B(0)(4) = -0.00084(7)(More)
Cytochrome P450 NO reductase is an unusual member of the cytochrome P450 superfamily. It catalyzes the reduction of nitric oxide to nitrous oxide. The reaction intermediates were studied in detail by a combination of experimental and computational methods. They have been characterized experimentally by UV/Vis, EPR, Mössbauer, and MCD spectroscopy. In(More)
We present a formulation of the explicitly correlated second-order Møller-Plesset (MP2-F12) energy in which all nontrivial post-mean-field steps are formulated with linear computational complexity in system size. The two key ideas are the use of pair-natural orbitals for compact representation of wave function amplitudes and the use of domain approximation(More)
In this work, the extension of the previously developed domain based local pair-natural orbital (DLPNO) based singles- and doubles coupled cluster (DLPNO-CCSD) method to perturbatively include connected triple excitations is reported. The development is based on the concept of triples-natural orbitals that span the joint space of the three pair natural(More)
The local coupled cluster method DLPNO-CCSD(T) allows calculations on systems containing hundreds of atoms to be performed while typically reproducing canonical CCSD(T) energies with chemical accuracy. In this work, we present a scheme for decomposing the DLPNO-CCSD(T) interaction energy between two molecules into physical meaningful contributions,(More)