Analyses of the structural information of molecular fragments from the mass spectra of the solid-state products and their reaction solutions allow for the understanding of their formation and of their diverse properties. The reaction of CuCl2 and (1-methyl-1H-benzo[d]imidazole-2-yl)methanol (HL) led only to crystals containing molecular dimers of [Cu2(L)2Cl2] (Cu2). The CuII-CuII distance and Cu-OR-Cu angle in the structure are 3.044 Å and 104.8°, respectively. The magnetic susceptibility (3-400 K) is characterized by a very strong intradimer antiferromagnetic interaction of J = -465 and interdimer zj = -0.83 cm-1. But mass spectrometry of a dissolved single crystal in different source energies identifies both its fragmentation and oligomerization to [Cu] and [Cu]. DFT calculations give the relative stabilization energies of the fragments observed in ESI-MS to provide a formation process.