The coordination structure of M4L4H-8 macromolecules (M = Ni(II), Cu(ll), Pd(ID) containing small peptidic ligands (L = XaaHis or Xaa-His-Yaa) has been predicted prima* on the basis of spectroscopic and potentiometric data in the literature. In this work, the neutral tetranuclear nickel(11) complex 1 formed with four double-deprotonated ligands (L = a-methyl-alanyl-histamine) was prepared, and its crystal structure was determined (C36H56N16Ni4O4 center dot 4.5CH(3)OH center dot 1.5H(2)O: a = 11.2645(4) angstrom, b = 23.5003(8) angstrom, c = 20.9007(7) angstrom, beta = 102.321(1)degrees, monoclinic, F2(1/c), Z= 4). In complex 1, the metal ions have a square planar geometry with 4N donor set consisting of the N-terminal amino nitrogen, the deprotonated amide nitrogen, the imidazole N-3 atom, and the deprotonated imidazole N atom of the adjacent ligand. The latter nitrogen atom provides the connection of the four NiLH_2 units forming a C1 symmetrical saddle-like shape. The complexation of L with Ni(II) ion has been studied by a potentiometric method combined with UV visible spectrophotometric titration. At pH 8.0, the predominant species is M4L4H-8 with Peoligomenzation = 5.73. The tetranuclear structure of complex 1 was also studied in solution by 1H and 130 NMR spectroscopy suggesting a structure of symmetry Sq. DFT calculations on optimized structure in symmetry C1 and Sq have been performed to explain the observed differences in solution and in solid state. The nuclearity was also confirmed in solution by ESI-HRMS analysis.