Various Cd(ii) coordination polymers induced by carboxylates: multi-functional detection of Fe3+, anions, aspartic acids and bovine serum albumin

Abstract

By adjusting carboxylates, six Cd(II) coordination polymers based on a naphthalene–methylene mixed-bridged-amide ligand, [Cd(L)(DNBA)₂] (1), [Cd₂(L)₂(BDC)₂(H₂O)₂]·2H₂O (2), [Cd(L)(1,4-CHDA)] (3), [Cd(L)(HIPA)(H₂O)]·H₂O (4), [Cd(L)(MIP)]·H₂O (5), and [Cd(L)(PMA)_0.5(H₂O)]·H₂O (6) [L = N,N′-bis(4-methylenepyridin-4-yl)-1,4-naphthalene dicarboxamide, HDNBA = 3,5-dinitrobenzoic acid, H₂BDC = 1,4-benzenedicarboxylic acid, 1,4-H₂CHDA = 1,4-cyclohexanedicarboxylic acid, H₂HIPA = 5-hydroxyisophthalic acid, H₂MIP = 5-methylisophthalic acid and H₄PMA = pyromellitic acid] have been synthesized under hydrothermal conditions. 1 shows a 4-c sql coplanar structure. 2 exhibits a 2-fold vertical interpenetrating structure based on wave-like 4-c sql layers. 3 shows a (3,5)-c pnh network containing a unique μ₃-L. 4 features a 4-c sql wave-like network. 5 and 6 exhibit 3D structures with 6-c pcu and 4-c mog topologies. The number of carboxyl groups and functional group positions of the carboxylates have an important influence on the structures of the title complexes. The fluorescent responses of 1–6 towards Fe³⁺, anions, aspartic acid and bovine serum albumin were investigated. Among them, 4 shows sensitivity and selectivity (K_SV = 1.16 × 10⁴ L mol⁻¹ for Fe³⁺, 1.03 × 10⁴ L mol⁻¹ for CrO₄²⁻, 1.08 × 10⁴ L mol⁻¹ for Cr₂O₇²⁻, 1.17 × 10⁴ L mol⁻¹ for MnO₄⁻ and 1.05 × 10⁴ L mol⁻¹ for aspartic acid).