Force field parametrization for gadolinium complexes-based on ab initio potential energy surface calculations

Citation
A. Villa et al., Force field parametrization for gadolinium complexes-based on ab initio potential energy surface calculations, J PHYS CH A, 104(15), 2000, pp. 3421-3429
Citations number
28
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHYSICAL CHEMISTRY A
ISSN journal
1089-5639 → ACNP
Volume
104
Issue
15
Year of publication
2000
Pages
3421 - 3429
Database
ISI
SICI code
1089-5639(20000420)104:15<3421:FFPFGC>2.0.ZU;2-X
Abstract
The recent design of new magnetic resonance imaging (MR) contrast agents is oriented toward the synthesis of gadolinium(III) complexes with ligands pr esenting formally neutral (amidic or alcoholic) or anionic (phosphinic) oxy gen donor atoms. This paper presents the molecular mechanics (MM) parametri zation of Gd interactions with amidic, alcoholic and phosphinic oxygen dono r atoms, with the aim of supporting experimental effort. The parametrizatio n is performed on the basis of a previously developed procedure applied to the parametrization of Gd interactions with polyamino carboxylate (PAC) lig ands. Within the framework of valence force fields, the parameters for Gd-l igand interactions are determined by fitting the empirical potential to the ab initio potential energy surface (PES) of [Gd . 3 . OH2](3+), [Gd . 5b . OH2](3+), and [Gd . 8a](1-). Ab initio calculations were performed at the restricted Hartree-Fock (RHF) level by using an effective core potential (E CP) that includes 4f electrons in the core, an optimized valence basis set for the metal, and the 3-21G basis set for the ligand. Sampling of the PES is performed by moving the ion into the frozen coordination cage of the ab initio optimized geometries, The energy and first derivatives, with respect to the Cartesian coordinates of the metal and donor atoms, were calculated for each generated structure. Two sets of parameters, with the electrostat ic contribution turned on or off in the force fields, were determined. To t est the quality of the derived parameters and their transferability to othe r Gd complexes, MM calculations were performed on several gadolinium comple xes. The results show that both sets of parameters provide reliable molecul ar geometries, but it is necessary to include the electrostatic contributio n in the force fields to correctly reproduce the conformational energies.