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SCF ab initio study of the “through‐water” versus “direct” binding of the Na + and Mg 2+ cations to the phosphate anion
Author(s) -
Pullman Bernard,
Pullman Alberte,
Berthod Helene
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560140711
Subject(s) - supermolecule , chemistry , ion , ab initio , tetrahydrate , inorganic chemistry , ab initio quantum chemistry methods , molecule , computational chemistry , crystallography , hydrate , adduct , crystal structure , organic chemistry
SO ab initio computations in the supermolecule approach have been carried out on the interaction of the PO 4 H 2 − anion with the hexahydrate, pentahydrate, and tetrahydrate of Na + and Mg 2+ . The interaction with the hexahydrates corresponds to a “through‐water” association; the interactions with the lesser hydrates represent “direct” binding of the partially dehydrated cation with the anion. At these levels of hydration, the two types of interaction appear competitive with some advantage for the through‐water binding. Examples from x‐ray crystallographic studies of biological ligands substantiate the possible multiplicity of the binding processes. A small charge transfer for Na + and a much larger one for Mg 2+ exists in the hydrates, from the water molecules toward the cations. The net excess of charge on the cations is only slightly perturbed in the adducts with PO 4 H 2 − .