Solvent-dependent formation of 1D coordination polymers based on polynuclear copper(II)-carboxylate fragments and 4-(pyridine-3-yl)methyleneamino-1,2,4-triazole linkers

The solvent used for the synthesis and crystallization was shown to affect the composition and structure of compounds formed in the reaction of copper(II) trimethylacetate with a Schiff base, 4-(pyridin-3-yl)methyleneamino-1,2,4-triazole (L). The reaction of [Cu2(piv)4(Hpiv)2] (Hpiv – trimethylacetic acid) in MeCN was found to give the crystals of 1D coordination polymer {[Cu2(piv)4(L)]·MeCN}n (1), the structure of which contains binuclear {Cu2(piv)4} units linked by the bridging organic ligand L. A similar reaction in MeOH or EtOH gave 1D coordination polymers {[Cu6(OH)2(piv)10(L)2(ROH)2]∙4ROH}n (2: R = Me, 3: R = Et) whose structure is composed of alternating binuclear {Cu2(piv)4} and tetranuclear {Cu4(OH)2(piv)6(L)2(ROH)2} units bound by N-donor ligand L. Storage of the mother liquor obtained after the isolation of the crystals of 3 leads to the crystallization of chained polymer [Cu(piv)2L]n (4). The structures of new complexes 1–4 were determined by single crystal X-ray diffraction. According to magnetochemical measurements for 1 and 3, antiferromagnetic exchange interactions are observed in these compounds between CuII ions (S = ½) in binuclear {Cu2(piv)4} units (J = −190.5 and −215 cm−1, respectively), as well as dominate in tetranuclear {Cu4(OH)2(piv)6(L)2(EtOH)2} units of 3 (J1 = −202 cm−1, J2 = –23 cm−1, J3 = 18 cm−1).