Two Types of Pyridine Ligands in Mononuclear and Dinuclear Copper(II) Carboxylates

Copper(II) acetate [Cu(OOCCH3)2(L1)2] (L1 = 2,6-diaminopyridine) (1), [Cu(OOCCH3)2(L2)2] (L2 = 2-amino-6-methylpyridine) (2) and benzoate compounds [Cu2(OOCC6H5)4(L1)2]·2CH3CN (3), [Cu2(OOCC6H5)4(L1)2] (4), [Cu2(OOCC6H5)4(L2)2] (5), [Cu(OOCC6H5)2(L2)2] (6), were synthesized and characterized. X-ray structure analysis revealed monomeric structure in 1 and 6. In 1, cis arrangement of the ligands was found, and trans in 6, in an elongated octahedral CuO4N2 chromophore. The basal plane in 1 and 6 is formed by one co-ordinated oxygen atom from both carboxylates (Cu–O 1.9560(12)–2.007(3) Å) and pyridine nitrogen atom from two pyridine ligands (Cu–N 2.013(3)–2.282(14) Å), forming a CuO2N2 plane, while the second carboxylate oxygen atoms are more distant (Cu–O 2.488(3)–2.7648(16) Å). The dinuclear paddle- wheel central core was found in 5 (Cu–O 1.942(6)–1.992(6) Å), with pyridine nitrogen atoms in the axial positions (Cu–N 2.283(7), 2.284(7) Å). All compounds were characterized by magnetic measurements, electronic and vibrational spectroscopy and tested for fungal growth retardation activity