The structure, energy and stability of components formed in the preparation of fac-[99mTc(CO)3(H2O)3]+
Abstract
The geometry and total molecular energy of ten species in the system [Tc(CO)i(H2O)6−i]+ (i = 0–6) are calculated by using ab initio MO method at the MP2/CEP-121G level. Their formation free energies are estimated in the sequence [Tc(H2O)6]+ > trans-[Tc(CO)2(H2O)4]+ > [Tc(CO)(H2O)5]+ > trans-[Tc(CO)4(H2O)2]+ > mer-[Tc(CO)3(H2O)3]+ > cis-[Tc(CO)2(H2O)4]+ > cis-[Tc(CO)4(H2O)2]+ > [Tc(CO)5(H2O)]+ > fac-[Tc(CO)3(H2O)3]+ > [Tc(CO)6]+. The computation results of relative composition for various CO-to-H2O concentration ratios indicate that fac-[Tc(CO)3(H2O)3]+ is the dominant species when the pressure of CO is 0.1 MPa as experimentally observed, and preparation of some of the other species is also possible in controlled conditions.