Construction of bifunctional CdII luminescent coordination complexes and efficient detection of Cr2O72− and 2,4,6-trinitrophenol

Abstract

Three new CdII coordination polymers (CPs) based on a new flexible large π-electron-rich bis(pyridinyl-imidazole) ligand 9,10-bis((2-(pyridin-2-yl)-1H-imidazole-1-yl)methyl)anthracene (bpima) have been synthesized under solvothermal conditions using a mixed-ligand strategy: {[Cd(bpima)0.5(nda)(H2O)]·DMF} (CP 1), {[Cd(bpima)0.5(oba)]·DMF·2H2O} (CP 2), {[Cd(bpima)0.5(ipa)(H2O)]·DMF·2H2O} (CP 3), (H2nda = naphthalene-1,4-dicarboxylic acid; H2oba = 4,4′-oxydibenzoic acid and H2ipa = 5-(tert-butyl)isophthalic acid). CP 1 and CP 2 both feature 2D layer structures with hcb and sql topology, respectively. CP 3 shows 1D ladder-like double-chain structure. In additional, luminescent properties of CP 1 and CP 3 have been systematically investigated and demonstrated multi-responsive luminescent sensitivities. Two compounds can be used for detection of Cr2O72− and 2,4,6-trinitrophenol (TNP) with high sensitivity (High quenching efficiency Ksv: for Cr2O72−: 5.07 × 104 M−1 for CP 1 and 7.38 × 104 M−1 for CP 2; for TNP: 4.87 × 104 M−1 for CP 1 and 5.13 × 104 M−1 for CP 2. low detection limit values: for Cr2O72−: 0.56 μM for CP 1 and 0.38 μM for CP 2; for TNP: 0.63 μM for CP 1 and 0.52 μM for CP 2) and as well as good recyclability. In addition, the sensing mechanism for Cr2O72− and TNP is also discussed by experimental studies and theory calculations, which was attributed to the co-existence of competitive absorption (CA), fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) progress for TNP and CA progress for Cr2O72−, respectively. Moreover, simple fluorescent filter paper based on CP 1 has been developed to achieve detection of Cr2O72− and TNP via the unaided eye, which has great potential for practical applications.