Three coordination polymers based on 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether: Synthesis, structure and selective fluorescent sensing properties

Three CPs [Zn2(PDA)2(BMIOPE)2·3H2O]n (1), [Co(Br-BDC)(BMIOPE)]n (2) and [Co(MIP)(BMIOPE)]n (3) were synthesized by solvothermal method based on dual-ligand strategy (H2PDA, Br-H2BDC, BMIOPE and H2MIP are 1,3-phenylenediacetic acid, 5-bromo-isophthalic acid, 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether and 5-methylisophthalic acid, respectively). Complexes 1 and 3 exhibit twofold parallel interwoven sql nets. Complex 2 is 2D layer structure. The luminescence property investigations showed that complexes 1-3 could act as multi-responsive fluorescent sensors to detect UO22+, Cr2O72- and CrO42- and nitrofurantoin (NFT) through fluorescence turn-off process, presenting excellent sensitivity and selectivity. Finally, the possible fluorescent quenching mechanisms of complexes 1-3 toward the above pollutants are also further investigated by employing spectroscopic methods and quantum chemical calculations. The fluorescence lifetime measurements manifest the mechanism of fluorescence quenching is static quenching process.

Spectrophotometric Determination of Trace Amount of Total FeII/FeIII and Live Cell Imaging of a Carboxylato Zn(II) Coordination Polymer

The coordination polymer, (Zn(II)-CP, 1), {[Zn(2,6-NDC)(4-Cltpy)](H₂O)₄} (1) (2,6-H₂NDC = 2,6-naphthalene dicarboxylic acid and 4-Cltpy = 4'-chloro-[2,2';6',2″]terpyridine) is structurally characterized by single crystal X-ray diffraction measurement and other physicochemical studies (PXRD, FTIR, thermal analysis, microanalytical data). 4-Cltpy acts as end-capping ligand, and NDC^2- is a carboxylato bridging motif to constitute ZnN₃O₂ distorted trigonal bipyramid core that propagates to construct 1D chain. The coordination polymer, 1, detects total iron (Fe³⁺ and Fe²⁺) in aqueous solution by visual color change, colorless to pink. Absorption spectrophotometric technique in aqueous medium measures the limit of detection (LOD) 0.11 μM (Fe²⁺) and 0.15 μM (Fe³⁺), and binding constants (K_d) are 6.7 × 10⁴ M^-1 (Fe³⁺) and 3.33 × 10⁴ M^-1 (Fe²⁺). Biocompatibility of 1 is examined in live cells, and intracellular Fe²⁺ and Fe³⁺ are detected in MDA-MB 231 cells. Zn(II) substitution is assumed upon addition of Fe^III/Fe^II solution to the suspension of the coordination polymer, 1, in water-acetonitrile (41:1) (LZn^II + Fe^III/II → LFe^III + Zn^II, where L is defined as coordinated ligands), which is accompanied by changing from colorless to pink at room temperature. The color of the mixture may be assumed to the charge transfer transition from carboxylate-O to Cltpy via Fe(II/III) bridging center (carboxylate-O-Fe-CltPy). The product isolated from the reaction is finally characterized as Fe(III)@1-CP. It is presumed that product Fe(II)@1-CP may undergo fast aerial oxidation to transform Fe(III)@1-CP. The Fe^III exchanged framework (Fe(III)@1-CP) has been characterized by PXRD, IR, TGA and energy dispersive X-ray analysis (EDX)-SEM. The MTT assay calculates the cell viability (%), and the tolerance limit is 100 μM to total Fe²⁺ and Fe³⁺.

Sensing and photocatalytic properties of a new 3D Co(ii) coordination polymer based on 1,1′-di(p-carboxybenzyl)-2,2′-biimidazole

One novel 3D interpenetrated Co(ii) CP acts as multi-functional chemosensors in detection of Fe3+, Cr2O72−, CrO42− and nitrofurantoin and is an effective and stable photocatalyst and displays excellent photo-catalytic properties.