pH dependent facile synthesis of di- and trinuclear oxime based Cu(II) complexes: antiferromagnetic coupling in the dinuclear cores and spin frustration in the triangular core.

An oxime based tridentate Schiff base ligand 3-[3-(dimethylamino)propylimino]butan-2-one oxime (HL) produced two dinuclear compounds [Cu2L2(H2O)](ClO4)2 () and [Cu2L2(H2O)](BF4)2 (), and a hexanuclear compound [{Cu3(HL)3(O3ClO)(μ3-O)}2(μ-H)](ClO4)7 () when it was reacted with Cu(ClO4)2·6H2O or Cu(BF4)2·6H2O at different pH values. All three compounds have been structurally and magnetically characterized. Compounds and are dinuclear species in which the two square planar copper(ii) ions are joined solely by the double oximato bridges. On the other hand, the hexanuclear compound consists of two triangular Cu3O cores held together by a proton separated by an OO distance of 2.498(10) Å. The three square pyramidal copper(ii) ions at the corners of an isosceles triangle form a triangular core through central oxido (μ3-O) and peripheral oximato bridges. Each triangular Cu3O core is capped by an unusual triply coordinated (μ3-perchlorato-O,O',O'') perchlorate anion. Variable-temperature (2-300 K) magnetic susceptibility measurements show that compounds exhibit a strong antiferromagnetic interaction with J values -562.6, -633.1 and -636.0 cm(-1) respectively. The X-band EPR data at low temperature clearly indicate the presence of a spin frustration phenomenon in complex .

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