The elaborately designed π-electron-rich fluorescent ligand 1,4-bis(1-carboxymethylene-4-imidazolyl)benzene (H 2 L), possessing bifunctional groups including the carboxylate groups (building units) and 4-imidazoyl groups (N-donor potential active sites) has been employed to construct fluorescent coordination polymers. A luminescent sensor, namely [Cd(L)(phen) 2 ]•5H 2 O (1), was obtained, which has a one-dimensional structure. The fluorescent material shows a blue emission maximum at 457 nm with a luminescence lifetime of 488 ns and a quantum yield (QY) of 4.56%. Significantly, 1 serves as a promising multiresponsive luminescent sensor to detect trace nitroaromatic compounds (NACs) with the limits of detection (LOD) of 7.21 × 10 −8 , 1.85 × 10 −5 , and 1.15 × 10 −5 mol/L for 2nitrophenol (2-NP), 3-nitrophenol (3-NP), and 4-nitrophenol (4-NP), respectively. Furthermore, CP 1 exhibits fluorescent turn-off and turn-on sensing behavior for Fe 3+ and Al 3+ metal ions with trace amounts of 1.05 × 10 −7 and 1.13 × 10 −7 mol/L, respectively. Experimental methods and theoretical calculations were employed to elucidate the sensing mechanism in detail.
In order to elucidate the electronic structure of the hydrogen-bridge bond in B 2 H 6 molecule, the formation process of B 2 H 6 had been created by a hypothetical reaction of ''B 2 H 4 2-? 2H ? '', and the symmetry principles for reaction are applied in the process of creating new molecular orbitals through linear combination of the old orbitals. The orbital components of the hydrogen-bridge bond in B 2 H 6 are obtained, and the electronic structure of the hydrogen-bridge bond is explained qualitatively. In addition, the idea that explains the structure of a molecule by creating a hypothetical reaction is proposed, which might make more application in other cases.
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