Premium
Molecular Dynamics Simulations of MRI‐Relevant Gd III Chelates: Direct Access to Outer‐Sphere Relaxivity
Author(s) -
Borel Alain,
Helm Lothar,
Merbach André E.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010202)7:3<600::aid-chem600>3.0.co;2-h
Subject(s) - molecular dynamics , coordination sphere , relaxation (psychology) , chemistry , molecule , outer sphere electron transfer , aqueous solution , hydrogen bond , electron paramagnetic resonance , crystallography , chemical physics , computational chemistry , nuclear magnetic resonance , ion , physics , organic chemistry , psychology , social psychology
The structure and dynamics of the surrounding water were studied through molecular dynamics (MD) simulations for several Gd III polyaminocarboxylate and polyaminophosphonate complexes in aqueous solution. The radial distribution functions (rdf) show that a few water molecules are bonded to the ligand through hydrogen bonds to hydrophilic groups such as carboxylates and phosphonates. Residence times are of the order of 20–25 ps for the polyaminocarboxylate and 56 ps for the polyaminophosphonate chelates. No preferred orientation or bonding of water molecules is observed in the hydrophobic region of the anisotropic macrocyclic complexes. Our rdf allow calculation of the outer‐sphere contribution to the nuclear magnetic resonance dispersion (NMRD) profiles using Freed's finite differences method, including electronic relaxation. The results show that the commonly used analytical force‐free model is only an empirical relationship. When experimental outer‐sphere NMRD profiles are available ([Gd(teta)] − and [Gd(dotp)] 5− (teta= N , N ′, N ″, N ′′′‐tetracarboxymethyl‐1,4,8,11‐tetraazacyclotetradecane; dotp= N , N ′, N ″, N ′′′‐tetraphosphonatomethyl‐1,4,7,10‐tetraazacyclododecane) the calculated curves are in good agreement. In the case of [Gd(teta)] − , the comparison with the experimental NMRD profile has led us to predict a very fast electronic relaxation, which has been confirmed by the EPR spectrum.