Metal Phosphonates Based on Bis(benzimidazol-2-ylmethyl)imino Methylenephosphonate: From Discrete Dimer to Two-Dimensional Network Containing Metallomacrocycles

Hydrothermal reactions of bis(benzimidazol-2-ylmethyl)imino(methylenephosphonic acid) {[(C7H5N2)CH2]2NCH2PO3H2,
bbimpH2} with metal salts result in four new compounds, namely, Mn2{[(C7H5N2)CH2]2NCH2PO3}2(H2O)2·2H2O (1),
Cd2{[(C7H5N2)CH2]2NCH2PO3}2·2H2O (2), Fe2{[(C7H5N2)CH2]2NCH2PO3}2·H2O (3), and CuI2{[(C7H5N2)CH2]2NCH2P(OH)O2}2 (4). Compounds 1 and 2 have dinuclear structures in which two {MN3O3} octahedra are linked through
edge sharing. In compound 3, a chain structure is observed where the {FeN3O2} trigonal bipyramids are linked by
{CPO3} tetrahedra through corner-sharing. The structure of compound 4 is unique. The monovalent Cu(I) ions are
connected by the imidazole nitrogen atoms from the bbimp2- ligands forming a 16-member metallomacrocycle.
These metallomacrocycles are further connected by the phosphonate oxygen atoms, leading to a two-dimensional
net containing 16- and 32-member rings. Magnetic studies of 1 and 3 reveal that weak ferromagnetic interactions
are mediated between magnetic centers in compound 1, while antiferromagnetic interactions were observed in
compound 3.