Büsra Dereli

The Role of Alkoxide Initiator, Spin State, and Oxidation State in Ring-Opening Polymerization of ε-Caprolactone Catalyzed by Iron Bis(imino)pyridine Complexes

Density functional theory (DFT) is employed to characterize in detail the mechanism for the ring-opening polymerization (ROP) of ε-caprolactone catalyzed by iron alkoxide complexes bearing redox-active bis(imino)pyridine ligands. The combination of iron with the non-innocent bis(imino)pyridine ligand permits comparison of catalytic activity as a function of oxidation state (and overall spin state). The reactivities of aryl oxide versus alkoxide initiators for the ROP of ε-caprolactone are also examined. An experimental test of a computational prediction reveals an Fe(III) bis(imino)pyridine bis-neopentoxide complex to be competent for ROP of ε-caprolactone.

Density Functional Modeling of Ligand Effects on Electronic Structure and C–H Bond Activation Activity of Copper(III) Hydroxide Compounds

A series of Cu(III)-OH complexes supported by differently substituted bis(carboxamido)pyridine ligands is modeled to identify factors affecting electronic structure and hydrogen atom transfer reactivity. Activation of hydrocarbon substrates is inferred to be influenced by a combination of many factors, including overall charge state, counterion nature (when present), solvation, attractive and repulsive steric interactions, and quantum mechanical tunneling along the reaction coordinate.

Accurate Ionization Energies for Mononuclear Copper Complexes Remain a Challenge for Density Functional Theory

Copper is ubiquitous and its one-electron redox chemistry is central to many catalytic processes. Modeling such chemistry requires electronic structure methods capable of the accurate prediction of ionization energies (IEs) for compounds including copper in different oxidation states and supported by various ligands. Herein, we estimate IEs for 12 mononuclear Cu species previously reported in the literature by using 21 modern density functionals and the DLPNO-CCSD(T) wave function theory model; we consider extrapolated values of the latter to provide reference values of acceptable accuracy. Our results reveal a considerable diversity in functional performance. Although there is nearly always at least one functional that performs well for any given species, there are none that do so for every member of the test set, and certain cases are particularly pathological. Over the entire test set, the SOGGA11-X functional performs best with a mean unsigned error (MUE) of 0.22 eV. PBE0, ωB97X-D, CAM-B3LYP, M11-L, B3LYP, and M11 exhibit MUEs ranging between 0.23 and 0.34 eV. When including relativistic effects with the zero-order regular approximation, ωB97X-D, CAM-B3LYP, and PBE0 are found to provide the best accuracy.