Structure, magnetic properties and nuclease activity of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) complexes

New complexes of formulae [Cu(HL 2)(H 2O)(NO 3)](NO 3) ( 1), [{Cu(L 1)(tfa)} 2] ( 2), [{Cu(L 1)} 2(pz)](ClO 4) 2 ( 3) and {[{Cu(L 1)} 2(dca)](ClO 4)} n ( 4), where HL 1 = pyridine-2-carbaldehyde thiosemicarbazone, HL 2 = pyridine-2-carbaldehyde 4 N-methylthiosemicarbazone, Htfa = trifluoroacetic acid (CF 3COOH), pz = pyrazine (C 4H 4N 2) and dca = dicyanamide [N(CN) 2] −, have been synthesized and characterized. The crystal structures of these compounds are built up of monomers ( 1), dinuclear entities with the metal centers bridged through the non-thiosemicarbazone coligand ( 2 and 3) and 1D chains of dimers ( 4). In all the cases, square–pyramidal copper(II) ions are present, except for the square–planar ones in 3. Magnetic measurements show antiferromagnetic couplings in 2, 3 and 4. The susceptibility data were fitted by the Bleaney–Bowers’ equation for copper(II) dimers derived from H = –2 JS 1 S 2 being the obtained J/k values −4.8, −4.3 and −5.1 K for compounds 2– 4, respectively. The magnetic susceptibility of the already known [{Cu(HL 1)(tfa)} 2](tfa) 2 compound has been also measured for the first time. The J/k value is –0.3 K, lower than that in 2. The nuclease activity of 3 and 4 has been analyzed.