The binding energies of one and two water molecules to the first transition-row metal positive ions. II

Abstract

The binding energy of H2O to transition-metal ions is determined not only by the electrostatic interaction, but by 4s4p and 3d4s hybridization and by 4s to 3d promotion on the metal. All of the M(H2O)+2 systems are linear except for Mn(H2O)+2 and Zn(H2O)+2, which we show to be bent with 7A1 and 2A1 ground states, respectively. The O–Mn–O bond angle is 94° and the O–Zn–O bond angle is 99°. These systems bend to allow 4s4p hybridization, which reduces the repulsion. For Mn+, the 3dn4s1–3dn+1 separation is too large to allow 3d4s hybridization or 4s to 3d promotion. For Zn+ the ground-state 3d104s1 occupation precludes 4s to 3d promotion or 3d4s hybridization.