Molecular Mechanics Investigation of Gadolinium(III) Complexes

Parameters for the commercially available modeling package SYBYL have been developed for Gd³⁺ complexes allowing these to be studied with molecular mechanics. With these parameters and a technique termed the "coordination scan", the coordination numbers of Gd(III) based complexes can be predicted, and thus the hydration number q determined. Knowledge of q has allowed the prediction of molar relaxivities based on correlations to literature values. In addition, the calculated value δE_coord was found to successfully predict the thermodynamic stability constants for polyamino carboxylate ligands with Gd³⁺. Gadolinium complexes are commonly utilized as MRI contrast agents, and thus the techniques utilized in this work should aid in the development of new contrast agents.