A series of d10 metal coordination polymers based on a flexible bis(2-methylbenzimidazole) ligand and different carboxylates: synthesis, structures, photoluminescence and catalytic properties

Abstract

To explore the influence of different aromatic polycarboxylates on the self-assembly and properties of d¹⁰ metal coordination frameworks, six coordination compounds containing a flexible bis(2-methylbenzimidazole) (pbmb) ligand, formulated as [Ag₂(pbmb)(2,6-napdc)]_n (1), {[Zn(pbmb)(tbta)]·H₂O}_n (2), {[Cd(pbmb)(tbta)]·H₂O}_n (3), [Zn₂(pbmb)(btec)(H₂O)]_n (4), {[Zn₂(OH)(pbmb)(bpdc)_1.5]·H₂O}_n (5), and [Cd(pbmb)(3-npa)(H₂O)]_n (6), have been synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as single-crystal X-ray diffraction analysis (2,6-H₂napdc = 2,6-naphthalenedicarboxylic acid, H₂tbta = tetrabromoterephthalic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid, H₂bpdc = biphenyl-4,4′-dicarboxylic acid and H₂3-npa = 3-nitrophthalic acid). Complex 1 possesses an 8-connected 3D coordination framework with sqc3 topology based on rare tetranuclear Ag(I)-cluster secondary building units (SBUs). 2 and 3 possess 2D (4,4) grid structures. 4 shows a novel (3,4,5)-connected 2D network with the Schläfli symbol of {3·4·5}{3·4²·5²·6}{3·4³·5³·6·7²}. 5 features a uninodal (4,4)-connected net containing binuclear {Zn₂(OH)} SBUs and a 2-fold interpenetrating (3,6)-connected supramolecular framework with {4²·6}{4⁴·6¹⁰·8}-3,6T24 topology that is formed via hydrogen bond interactions. Complex 6 is a 1D double-chain structure, which is finally extended to a 3D (4,5,5)-connected supramolecular network via hydrogen bonding interactions. Complexes 1–6 indicate high thermal stabilities and different photoluminescence behavior in the solid state. Moreover, all of these polymer materials manifest excellent photocatalytic activities for the degradation of methyl orange in the photo-Fenton-like process after 120 min (1: 99%, 2: 66%, 3: 91%, 4: 83%, 5: 91% and 6: 93%, respectively).