In conclusion, we studied potential energy curves, dissociation energies, excitation energies, harmonic vibrational frequencies, and chemical bonding patterns of several low-lying electronic states HfCO. We found seven bound electronic states of HfCO with respect to the Hf( 3 F)+CO(X 1 Σ + ) dissociation. Among these, all but the X 3 Ʃ -and b 5 Δ are multi-reference in nature. We adopted larger augmented quadruple-and quintuple-ζ basis sets to obtain highly accurate CCSD(T) results for the two single-reference electronic states. Our analysis on MCX (M = Hf, Zr, Ti and X = O, S, Se, Te, Po) demonstrated a linear relationship between the dissociation energies of these complexes and the dipole moments of the CX species, where De increases moving from lighter MCO to heavier MCPo.