Ferromagnetic coupling in two tetranuclear Ni(II) complexes with cubane–like Ni4(μ3–O)4 core: Structure, spectroscopic and luminescence properties

Abstract

Two new tetranuclear [Ni4(L1)4(MeOH)4] (1) and [Ni4(L2)4(EtOH)(MeOH)(H2O)2]·H2O (2) complexes have been synthesized by solvothermal method. We here report the spectroscopic, structural, photoluminescence and magnetic properties of both complexes. Complex 1 and 2 exhibit a cubane-like Ni4O4 structure. All Ni(II) center has a slightly distorted octahedral geometry. The optical properties of 1 and 2 have been analyzed by photoluminescence spectra obtained in the visible region. Variable-temperature (2–300 K) magnetic studies have been analyzed by using the Heisenberg Hamiltonian model with 2J exchange pathways. The best–fit parameters in analysis of the magnetic data are found as J1 = −2.38 cm−1, J2 = +5.43 cm−1, g = 2.2, Nα = 0.08 for 1, J1 = −2.34 cm−1, J2 = +4.90 cm−1, g = 2.2 and Nα = 0.11 for 2. These results are shown dominant ferromagnetic interactions between Ni(II) centers. Finally, the strong luminescence emission of both complexes makes them potentially useful photoactive material in developing optical and electronic materials.