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

Two new ZnII /CdII 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 (H2 bpdc) have been synthesized under solvothermal conditions: {[Zn(bbimc)(bpdc)]·DMF·2.5H2 O} (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 {44 ·62 }. 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 Cr2 O7 2- , CrO4 2- and antibiotics (TC: Tetracycline; CTC: Chlortetracycline) in H2 O by exhibiting fluorescence quenching with significant quenching constants (Ksv  = 1.369 × 104 M-1 (Cr2 O7 2- ), 2.003 × 104 M-1 (CrO4 2- ), 5.343 × 104 M-1 (TC), 8.706 × 104 M-1 (CTC) for CP 1 and 4.452 × 104 M-1 (Cr2 O7 2- ), 2.119 × 104 M-1 (CrO4 2- ), 4.175 × 104 M-1 (TC), 1.257 × 105 M-1 (CTC) for CP 2). The detection limit are 0.67 μM (Cr2 O7 2- ), 0.48 μM (Cr2 O7 2- ), 0.23 μM (TC), 0.14 μM (CTC) for CP 1 and 0.28 μM (Cr2 O7 2- ), 0.54 μM (CrO4 2- ), 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.