The X-ray molecular structure and, magnetic, and spectroscopic properties, as well as the analysis of the structural behavior in solution of a novel nickel (II) complex [Ni 2 (HBPClNOL) 2 (OAc)](ClO 4 ) 1 are reported. Complex 1 was prepared by the reaction between the ligand H 2 BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl) [(3-chloro)(2-hydroxy)]propylamine), [Ni(H 2 O) 6 ](ClO 4 ) 2 and sodium acetate. Magnetic measurements indicate the presence of a weak antiferromagnetic coupling between the Ni(II) ions in 1, resulting in J = À4.23 cm À1 . Mass spectrometric characterization of the complex 1 was also performed via ESI-MS and ESI-MS/MS experiments and reveals that there are at least three different cations in solution, one mononuclear [Ni(H 2 BPClNOL)(OAc)] + and two dinuclear [Ni 2 (HBPClNOL) 2 (OAc)] + and [Ni 2 (HBPClNOL) 2 (ClO 4 )] + cations, as well as likely a fourth one [Ni(HBPClNOL)] + . Potentiometric titration experiments confirm that under acid conditions, the dinuclear unit is broken. However, under neutral/basic pH values the dinuclear unit is stable and shows the presence of two water molecules coordinated to the nickel ions, resulting in the cation [Ni 2 (HBPCl-NOL) 2 (H 2 O) 2 ] 2+ . This cation shows two protonation/deprotonation equilibriums with pK a values of 9.68 and at 10.29, which are related to the aquo/hydroxo equilibrium associated with the water molecules coordinated to the metal ions.