Extension of the AMBER force-field for the study of large nitroxides in condensed phases: an ab initio parameterization.
The popular AMBER force-field has been extended to provide an accurate description of large and flexible nitroxide free-radicals in condensed phases. New atom types have been included, and relevant parameters have been fitted based on geometries, vibrational frequencies and potential energy surfaces computed at the DFT level for several different classes of nitroxides, both in vacuo and in different solvents. The resulting computational tool is capable of providing reliable structures, vibrational frequencies, relative energies and spectroscopic observables for large and flexible nitroxide systems, including those typically used as spin labels. The modified force field has been employed in the context of an integrated approach, based on classical molecular dynamics and discrete-continuum solvent models, for the investigation of environmental and short-time dynamic effects on the hyperfine and gyromagnetic tensors of PROXYL, TEMPO and INDCO spin probes. The computed magnetic parameters are in very good agreement with the available experimental values, and the procedure allows for an unbiased evaluation of the role of different effects in tuning the overall EPR observables.
Stendardo
Emiliano
E
Dipartimento di Chimica Paolo Corradini, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italia.
Pedone
Alfonso
A
Cimino
Paola
P
Cristina Menziani
Maria
M
Crescenzi
Orlando
O
Barone
Vincenzo
V
D004578:Electron Spin Resonance Spectroscopy; D006841:Hydrocarbons, Aromatic / Q000737:chemistry; D008958:Models, Molecular; D009589:Nitrogen Oxides / Q000737:chemistry*; D012997:Solvents; D013113:Spin Labels
D006841:Hydrocarbons, Aromatic; D009589:Nitrogen Oxides; D012997:Solvents; D013113:Spin Labels; C039900:nitroxyl