Self assembly of asymmetric tetranuclear Cu(II) [2 x 2] grid-like complexes and of a dinuclear Ni(II) complex from pyridyl-phenol Schiff base ligands

Self assembly of N-salicylidene 2-aminopyridine (L1H) with Cu(NO3)(2)center dot 3H(2)O affords [Cu-4(L1)(4)(NO3)(3)(CH3OH)][Cu(L1)(NO3)(2)[(2-aminopyridinium)(NO3)center dot 5CH(3)OH (1) which is composed of an asymmetric [2 x 2] grid-like cationic complex that co-crystallizes with a Cu(II) mononuclear anion. This remarkable tetranuclear unit presents three penta-coordinated and one hexa-coordinated Cu(II) sites. This quadruple helicate structure reveals strong anti-ferromagnetic coupling (J = -340(2) cm(-1)) between Cu(II) ions through a double alkoxo bridge. Reacting L1H with Cu(NO3)(2)center dot 3H(2)O in slightly different conditions affords however a more symmetric tetranuclear grid-like complex: [Cu-4(L1)(4)(NO3)(2)(OH)(2)](2-aminopyridinium)(OH)center dot CH3OH) (2). A dinuclear Ni(II) complex. [Ni-2(L2)(2)(L2H)(2)(NCS)(2)(CH3OH)(2)]center dot 2CH(3)OH (3), obtained with another related donor Iigand (L2H = N-salicylidene 3-aminomethylpyridine) was also prepared. (C) 2010 Elsevier Ltd. All rights reserved.