Structural diversity, magnetic properties, and luminescence sensing of five 3D coordination polymers derived from designed 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid

Abstract

Based on the designed π-conjugated aromatic pentacarboxylate of 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid (H₅DDB) and bis(imidazole) ancillary linkers (bib = 1,4-bis(imidazol-1-yl)benzene, m-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, p-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene), five 3D coordination polymers, namely, {Co₂(HDDB)(bib)_1.5(H₂O)₂]·H₂O}_n (1), {[Mn_2.5(H₂DDB)(HDDB)(bib)_0.5(μ₂-H₂O)(H₂O)_1.5]·(Hbib)·0.5(H₂bib)·0.5H₂O}_n (2), {[Cd₂(HDDB)(bib)_1.5(H₂O)]·2.5H₂O}_n (3), {[Cd₂(HDDB)(m-bimb)]·H₂O}_n (4), and {[Cd₂(DDB)(p-bimb)]·2.5H₂O·0.5(p-H₂bimb)}_n (5), have been obtained and characterized. Complex 1 is a 3D 3-fold interpenetrating (3,4)-c {8³}₂{8⁵·9}-vtx net. Based on the binuclear {Mn₂(COO)₂} SBUs, as well as the trinuclear {Mn₃(COO)₄(μ₂-H₂O)₂} SBUs, complex 2 shows a 3D 3,4,6-c 3,4,6T10 net with a point symbol of {3·7²}₂{3²·7³·8}{3²·7⁶·8⁶·10}. Complex 3 displays an unprecedented 3D (3,4,4)-c net with a point symbol of {6·8²}₂{6⁴·8²}₂{8·10⁴·12} based on the binuclear {Cd₂(COO)₄} SBUs. Complex 4 shows an interesting 3D (3,10)-c {4¹⁰·6³²·8³}{4³}₂ net based on the quadrilateral tetranuclear {Cd₄(COO)₈} SBUs. Complex 5 exhibits a linear tetranuclear {Cd₄(COO)₄} SBU-based 3D (4,10)-c deh1 net with a point symbol of {3·4⁵}₂{3⁴·4¹²·5¹⁰·6¹⁴·7³·8²}. A variable temperature magnetic susceptibility investigation indicated that antiferromagnetic interactions exist between the neighbouring metal ions in 1 and 2. Fluorescence measurements showed that 3–5 are promising luminescence sensors for the detection of Cr(VI) anions (CrO₄²⁻ and Cr₂O₇²⁻ anions) in aqueous solution.