title: Positional isomeric tunable two Co(II) 6-connected 3-D frameworks with pentanuclear to binuclear units: structures, ion-exchange and magnetic properties.
abstract: Two new Co(II) based metal-organic frameworks, namely {[Co5(μ3-OH)2(m-pda)3(bix)4]·2ClO4}n (1) and {[Co2(p-pda)2(bix)2(H2O)]·H2O}n (2), were prepared by hydrothermal reactions of Co(II) salt with two isomeric dicarboxyl tectons 1,3-phenylenediacetic acid (m-pda) and 1,4-phenylenediacetic acid (p-pda), along with 1,3-bis(imidazol-L-ylmethyl)benzene (bix). Both complexes 1 and 2 have been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). 1 shows a 6-connected 3-D pcu cationic framework with pentanuclear [Co5(μ3-OH)2(COO)6(bix)2](2+) units, while 2 exhibits a 6-connected 3-D msw net based on [Co2(μ2-H2O)(COO)2](2+) clusters. The results indicate that the different dispositions of the carboxylic groups of dicarboxylates have an important effect on the overall coordination frameworks. Perchlorate anions in 1 can be partly exchanged by thiocyanate and azide anions, however they are unavailable to nitrate anions. Magnetic susceptibility measurements indicate that both 1 and 2 show weak antiferromagnetic interactions between the adjacent Co(II) ions.
authors.affiliation: College of Materials and Chemical Engineering, Collaborative Innovation Center for Microgrid of New Energy of Hubei Province, China Three Gorges University, Yichang 443002, P. R. China. lidongsheng1@126.com.
authors.forename: Min-Le
authors.initials: ML
authors.lastname: Han
authors.forename: Ya-Ping
authors.initials: YP
authors.lastname: Duan
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Li
authors.forename: Hai-Bin
authors.initials: HB
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhao
authors.forename: Yao-Yu
authors.initials: YY
authors.lastname: Wang