Synthesis, Structures and Recognition Properties of Two Cadmium(II) Phosphonates for Highly Selective Sensing of Cr₂O₇²⁻ and CrO₄²⁻ Anions

Abstract

Two cadmium (II) phosphonates, [Cd(MPBP)(2, 2′−bipy)(H2O)]⋅H2O (1) and [Cd(H2BPDP)(2,2′−bipy)2(H2O)]⋅H2O (2) [H2MPBP=4,4−Bis(monoethylphosphonomethyl)biphenyl, H4BPDP=biphenyl−4,4′−diylbis(methylene)diphosphonic acid, 2,2′−bipy=2,2′−bipyridine], had been successfully synthesized under hydrothermal conditions with different reaction temperatures by using H2MPBP as the phosphonate ligand and 2,2′−bipyridine as the second organic ligand. The compound 1 exhibited a 3D supramolecular structure, in which {CdN2O4} polyhedra and {CPO3} tetrahedra were interconnected by MPBP anions to form a 1D double chain via corner–sharing. Neighboring chains were linked into a 2D supramolecular sheet in the ac–plane by hydrogen bonding interactions, which were further assembled through π−π stacking interactions to form a 3D supramolecular structure. Compound 2 was assembled through π−π stacking and hydrogen bonding interactions to form a 1D supramolecular structure. Furthermore, both compounds exhibited remarkable luminescent properties, and could be applied as the high selective and sensitive luminescent sensors in the sensing of Cr2O72− and CrO42− anions through the luminescence quenching effect with a low–detection limit of 3.5 × 10−7 M and 4.6 × 10−7 M (for 1) and 6.1 × 10−7 M and 4.3 × 10−7 M (for 2), respectively. Additionally, the probable mechanisms for the quenching behaviour for the two compounds had also been investigated in detail.

Synthesis and Recognition Properties of Cd(II) Framework for Highly Selective Sensing of Fe3+, Cr2O72− and CrO42− ions

“…In summary, the lowest detection limits of Fe 3+ , Cr 2 O 7 2− and CrO 4 2− ions in this study are 2.03×10 −7 M, 1.32×10 −7 M and 2.77×10 −7 M, respectively. We compared these results with previous reports in the literature, as shown in Table S3, the detection limits of Fe 3+ , Cr 2 O 7 2− and CrO 4 2− ions in the given literatures are 2.49–87.9 μM, [56–60] 0.35–92.1 μM [57–60] and 0.28–78.9 mΜ, [56,61,62] respectively. This indicates that the ultra‐low detection limits of Fe 3+ and Cr 2 O 7 2− ions in this study are bright spots that break through previous studies, and the detection limit of CrO 4 2− ion is also better than that of the given references.…”

“…The authors have cited additional references within the Supporting Information. [56,[60][61][62][69][70][71][72] The supporting information includes specific experimental operation, C, H, and N elemental analysis (EA) and infrared spectrum analysis, solid-state emission spectrum of 1. SEM images of complex 1 with treated and the original sample.…”