Two-dimensional potential energy surfaces of charged and neutral MXO (X: C, N and M: Au, Ag, Cu) and neutral M2XO complexes were calculated. Our results are based on the CCSD(T)/AVTZ level of theory with effective core potentials for the transition metals. The calculations show that the PES of MXO+ have two minima, one at the linear X-down, the other at linear O-down structure, while the neutral complexes have only one minimum, X-down, but in a triangular shape with an angle depending on the metal atom. The negative charged complexes have a dispersive minimum when the metal anion nearly perpendicular to the geometrical center of the XO molecule and distance greater than 3.5 Å.
Additionally we have calculated the interaction energy of M2XO complexes with different orientations and found that the linear X-down complexes are the most stable orientation. Also the binding of the CO molecule to the diatomic M2 is stronger than to the M atom. On the contrary, the binding of the NO molecule to the diatomic M2 is weaker than the M atom. The strength of the binding energies are ranked based on the type of the metal, for all type of charge and type of X atoms, as Au > Cu > Ag. About the isoelectric pairs: MCO, MNO+ and MCO-, MNO, there is no correlation between the number of electrons and the shape of the PES.
The counterpoise-corrected interaction energy increases as the charge of the complex increases. The positive charged complexes have blue shift in X-O stretching frequency while the neutral and negative charged complexes have red shift.
With these highly accurate PESs, it is possible to fit force fields for the system under investigation and to perform an anharmonic vibrational analysis.
