Structurally diverse copper(II) phosphonates: Synthesis, structure, and magnetism

A dinuclear copper phosphonate [Cu2(AIPA)2(H2O)4] (1) (H2AIPA = (2-aminopropan-2-yl)phosphonic acid) was prepared, and its reaction with 4,4 '-bipyridine (4,4 '-bpy) and ethylenediamine (en) yielded a linear-chain polymeric complex having the composition {Cu2(AIPA)2(H2O)2(4,4 '-bpy)}n (2), and an ionic complex [Cu (en)2(H2O)2][Cu(AIPA)2] (3), respectively. The complexes were thoroughly characterized, and their structures were determined by single-crystal X-ray diffraction. Complex 2 was formed by the substitution of the two coordinated water molecules in complex 1 with two 4,4 '-bpy nitrogen atoms with the preservation of the cyclic dinuclear moiety and forming 1D-polymeric chains in which the {Cu2(AIPA)2} moieties are connected via the rigid 4,4 '-bpy bridges. In contrast, the utilization of the chelating en ligands led to splitting the dinuclear core of 1 into the mononuclear [Cu(en)2(H2O)2]2+ cation and the [Cu(AIPA)2]2- anion forming the ionic complex (3). The temperature dependent (2.5-300 K) magnetic susceptibility at 0.1 T and field dependent magnetization measurement (in the range of 0-9 T at 2, 5, and 10 K) data are also presented and discussed, reflecting structural diversity of the complexes 1, 2, and 3, and showing the following best-fit parameters: J = -5.68(3) cm-1, gx = 1.900(1), gy = 2.098(5), gz = 2.399(1), zJ = -0.012(7) cm-1 (for 1), J1-2 = J3-4 = -0.24(4) cm-1 with giso = 2.319 (4), and J2-3 = 0.2(1) cm-1 with giso = 2.319(4), and with zJ = -0.021(2) cm-1 (for 2 modelled as a polymeric alternating chain consisting of bridged dimeric units) and J = 0.185(9) cm-1, gx = 2.12(2), gy = 2.13(3), gz = 2.13(3), and zJ = -0.01(1) cm-1 (for 3).