A new molecular mechanics force field for the design of oxotechnetium(V) and oxorhenium(V) radiopharmaceuticals

Force field parameters for the modeling of oxotechnetium(V) and oxorhenium(V) complexes with amine, amide, imine, carboxylate and thiolate donors have been derived and optimized based on 131 published solid state structures. An automated procedure, based on a simplex algorithm, was used to optimize the 35 sets of metal-dependent structural parameters for each metal ion. These were introduced into the established MOMEC97 force field. The application of the new force field in the prediction of a novel radiopharmaceutical’s structure was successful, the predicted structures of the two isomers compared well with the corresponding crystal structures obtained subsequently (RMS around the metal core: 0.153 and 0.035 Å, respectively).