title: Racemic cobalt phosphonates incorporating flexible bis(imidazole) co-ligands.
abstract: By incorporating flexible bis(imidazol-1-ylmethyl)benzene (bix) co-ligands, four new racemic cobalt phosphonates with formulae Co3(3-ppap)2(1,4-bix)2(H2O)4·4H2O (1), Co3(3-ppap)2(1,3-bix)2(H2O)4·5H2O (2), Co3(3-ppap)2(1,2-bix)2(H2O)4·4H2O (3) and Co3(ppa)2(1,2-bix)2·4H2O (4) are isolated, where 3-ppapH3 represents 3-phenyl-3-((phosphonomethyl)amino)propanoic acid and ppaH3 is 2-phenyl-2-(phosphonomethylamino)acetic acid. Compounds 1-3 crystallize in the monoclinic space group P21/c and show two-dimensional structures in which the Co3(3-ppap)2 chains are bridged by 1,4-bix, 1,3-bix and 1,2-bix ligands in trans-modes, respectively. Within the chain, a racemic dimer of Co2(3-ppap)2(2-) is found, where the Co atoms are doubly bridged by O-P-O units from the (S)- and (R)-3-ppap(3-) ligands. The dimers are connected by another crystallographically independent Co atom through O-P-O linkages to form an infinite racemic chain. The packing modes of the layers in 1-3 are quite different, however, which are ABAB in the cases of 1 and 3 while ABCDABCD in the case of 2, attributed to the positional isomerism of the bix co-ligands. Compound 4 displays a chain structure in which the 1,2-bix bridges the Co atoms in cis-mode within the chain. Magnetic properties are investigated for all compounds.
authors.affiliation: State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China. baososo@nju.edu.cn lmzheng@nju.edu.cn.
authors.forename: Jian-Shen
authors.initials: JS
authors.lastname: Feng
authors.forename: Zhong-Sheng
authors.initials: ZS
authors.lastname: Cai
authors.forename: Min
authors.initials: M
authors.lastname: Ren
authors.forename: Song-Song
authors.initials: SS
authors.lastname: Bao
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Zheng
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000737:chemistry*; D008024:Ligands; D008280:Magnetics; D059346:Magnets / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D063065:Organophosphonates / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D008024:Ligands; D009942:Organometallic Compounds; D063065:Organophosphonates; D003035:Cobalt; C029899:imidazole