Multiresponsive luminescent sensors for antibiotics and Cr with two luminescent Zn/Cd coordination complexes.

Two new Zn/Cd luminescent coordination polymers (CPs) based on the V-shaped bis(imidazole) ligand 3,6-bis (1H-benzo[d]imidazol-1-yl)-9-methyl-9H-carbazole (bbimc) with [1,1'-biphenyl]-4,4'-dicarboxylic acid ligand (Hbpdc) have been synthesized under solvothermal conditions: {[Zn(bbimc)(bpdc)]·DMF·2.5HO} (CP 1), {[Cd(bbimc)(bpdc)]·2DMF} (CP 2). CP 1 and CP 2 both display a uninodal 4-c unimodal sql topology 2D framework with vertex symbols of {4·6}. In addition, the two identical 2D nets of CP 2 were interpenetrated each other to form a 2D + 2D → 3D and generate a 2-fold interpenetrating architecture. Moreover, sensing investigations of CP 1 and CP 2 revealed that both of compounds can be used as a highly sensitive and selective multi-responsive luminescent sensor for sensing CrO, CrO and antibiotics (TC: Tetracycline; CTC: Chlortetracycline) in HO by exhibiting fluorescence quenching with significant quenching constants (K = 1.369 × 10 M (CrO), 2.003 × 10 M (CrO), 5.343 × 10 M (TC), 8.706 × 10 M (CTC) for CP 1 and 4.452 × 10 M (CrO), 2.119 × 10 M (CrO), 4.175 × 10 M (TC), 1.257 × 10 M (CTC) for CP 2). The detection limit are 0.67 μM (CrO), 0.48 μM (CrO), 0.23 μM (TC), 0.14 μM (CTC) for CP 1 and 0.28 μM (CrO), 0.54 μM (CrO), 0.31 μM (TC), 0.098 μM (CTC) for CP 2, respectively. In addition, the probable fluorescence quenching mechanism was studied through experiment and theoretical calculation and the co-existance of competitive absorption (CA) and photoinduced electron transfer (PET) progress contributed to such sensing processes.