Structural diversity and magnetic properties of six metal–organic polymers based on semirigid tricarboxylate ligand of 3,5-bi(4-carboxyphenoxy)benzoic acid

Abstract

Solvothermal reactions of the semirigid 3,5-bi(4-carboxyphenoxy)benzoic acid (H₃BCP) and transitional metal cations with the help of three ancillary bridging imidazole linkers afforded six coordination polymers, namely, [Co(HBCP)(1,4-bib)_0.5]_n (1), {[Mn_1.5(BCP)(1,4-bib)_0.5(μ₂-H₂O)(H₂O)₂]·(1,4-bib)_0.5}_n (2), {[Mn_0.5(1,4-bib)(H₂O)]·(H₂BCP)}_n (3), {[Fe(BCP)_0.5(HCOO)_0.5(4,4′-bibp)_0.5]·2H₂O}_n (4), [Ni_2.5(HBCP)(BCP)(4,4′-bibp)₂(μ₂-H₂O)(H₂O)₂]_n (5), and [Ni(HBCP)(1,4-bidb)_1.5(H₂O)₂]_n (6), (1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene, 1,4-bidb = 1,4-bis(1-imidazol-yl)-2,5-dimethyl benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl). Their structures and properties were determined by single-crystal and powder X-ray diffraction analyses, IR spectra, elemental analyses, thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS). Complex 1 displays unusual 2D + 2D→2D parallel entangled networks consisting of (3,4)-connected 3,4L83 sheets. Complex 2 exhibits an interesting 2-fold interpenetrated framework with a trinodal (4,4,6)-connected (3·4·5·6²·7)₂(3·6·7⁴)₂(3²·4²·5²·6²·7⁶·9) topology. The host network of complex 3 is a 2D 4-connected (4⁴·6²)-sql sheet. Complex 4 affords unprecedented 3D (4,6,6)-coordinated framework with point symbol of (4⁵·6)(4⁸·6⁷)(4⁹·6³·8³)₂, in which the 1D helix water chains occupy the void channels. Complex 5 can be regarded as a novel self-penetrating (4,4,4,5)-coordinated framework with point symbol of (4·5⁴·6)₂(4·6⁵·7·8³)₂(5·6·7·8³)₂(5²·8³·9²), which contains two interpenetrated (3,4,4,5)-coordinated (4·5⁴·6)₂(4·6⁵·7·8³)₂(5·6·7)₂(5²·8³·9²) subnets linked by μ₂-H₂O. Complex 6 shows a 1D ladder chain, which are further assembled into a 3D supramolecular structure via O–H⋯O and π⋯π interactions. Moreover, magnetic studies indicate that both complex 2 and 4 show antiferromagnetic properties.