Abstract
Four bis-tetradentate N4-substituted-3,5-{bis- [bis-N-(2-pyridinemethyl)]aminomethyl}-4H-1,2,4-triazole ligands, LTz1−LTz4, differing only in the triazole N4 substituent R (where R is amino, pyrrolyl, phenyl, or 4-tertbutylphenyl, respectively) have been synthesized, characterized, and reacted with MII(BF4)2*6H2O (MII = Cu, Ni or Co) and Co(SCN)2. Experiments using all 16 possible combinations of metal salt and LTzR were carried out: 14 pure complexes were obtained, 11 of which are dinuclear, while the other three are tetranuclear. The dinuclear complexes include two copper(II) complexes, [CuII 2(LTz2)(H2O)4](BF4)4 (2), [CuII 2(LTz4)(BF4)2](BF4)2 (4); two nickel(II) complexes, [NiII 2(LTz1)(H2O)3(CH3CN)](BF4)4*0.5(CH3CN) (5) and [NiII 2(LTz4)(H2O)4](BF4)4*H2O (8); and seven cobalt(II) complexes, [CoII 2(LTz1)(μ-BF4)](BF4)3*H2O (9), [CoII 2(LTz2)(μ-BF4)](BF4)3*2H2O (10), [CoII 2(LTz3)- (H2O)2](BF4)4 (11), [CoII 2(LTz4)(μ-BF4)](BF4)3*3H2O (12), [CoII 2(LTz1)(SCN)4]*3H2O (13), [CoII 2(LTz2)(SCN)4]*2H2O (14), and [CoII 2(LTz3)(SCN)4]*H2O (15). The tetranuclear complexes are [CuII 4(LTz1)2(H2O)2(BF4)2](BF4)6 (1), [CuII 4(LTz3)2(H2O)2(μ-F)2](BF4)6*0.5H2O (3), and [NiII 4(LTz3)2(H2O)4(μ F2)](BF4)6*6.5H2O (7). Single crystal X-ray structure determinations revealed different solvent content from that found by microanalysis of the bulk sample after drying under a vacuum and confirmed that 5′, 8′, 9′, 11′, 12′, and 15′ are dinuclear while 1′ and 7′ are tetranuclear. As expected, magnetic measurements showed that weak antiferromagnetic intracomplex interactions are present in 1, 2, 4, 7, and 8, stabilizing a singlet spin ground state. All seven of the dinuclear cobalt(II) complexes, 9−15, have similar magnetic behavior and remain in the [HS−HS] state between 300 and 1.8 K.