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](2)NCH2PO3H2, bbimpH(2)} with metal salts result in four new compounds, namely, Mn-2 {[(C7H5N2) CH2](2)NCH2PO3}(2)(H2O)(2)center dot 2H(2)O ( 1), Cd-2 {[(C7H5N2) CH2](2)NCH2PO3}(2)center dot 2H(2)O (2), Fe-2 {[(C7H5N2) CH2](2)NCH2PO3}(2)center dot H2O ( 3), and Cu-2(I) {[(C7H5N2) CH2](2)NCH2P( OH) O-2}(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 bbimp(2-) 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.