Two Highly Stable Luminescent Lead Phosphonates Based on Mixed Ligands: Highly Selective and Sensitive Sensing for Thymine Molecule and VO₃^– Anion

Abstract

Two luminescent lead phosphonates with two-dimensional (2D) layer and three-dimensional (3D) framework structure, namely, Pb 3 [(L 1 ) 2 (Hssc)(H 2 O) 2 ] ( 1 ) and [Pb 2 (L 2 ) 0.5 (bts)(H 2 O) 2 ]·H 2 O ( 2 ) (H 2 L 1 = O(CH 2 CH 2 ) 2 NCH 2 PO 3 H 2 , H 4 L 2 = H 2 PO 3 CH 2 NH(C 2 H 4 ) 2 NHCH 2 PO 3 H 2 , H 3 ssc = 5-sulfosalicylic acid, NaH 2 bts = 5-sulfoisophthalic acid sodium) have been prepared via hydrothermal techniques. The two compounds not only show excellent thermal stability but also remain intact in aqueous solution within an extensive pH range. Moreover, the atomic absorption spectroscopy analysis experiment indicates that there does not exist the leaching of Pb 2+ ions from the lead phosphonates, which show they are nontoxic in aqueous solution. In compound 1 , the Pb(1)O 4 , Pb(2)O 7 , Pb(3)O 4 , and CPO 3 polyhedra are interlinked into a one-dimensional chain, which is further connected to adjacent chain by sharing the Hssc 2– to form a 2D layer. Interestingly, compound 1 as a highly selective and sensitive luminescent material can be used to detect the thymine molecule with a very low detection limit of 8.26 × 10 –7 M. In compound 2 , the Pb(1)O 6 and Pb(2)O 5 polyhedra are interlinked into a dimer via edge sharing, which is further connected to adjacent dimer to form a tetramer via corner sharing, and such a tetramer is then interlinked into a 2D layer through bts 3– ligands; the adjacent 2D layers are finally constructed to a 3D structure by sharing the L 2 4– ligand. Compound 2 can be applied as an excellent luminescent sensor for sensing of VO 3 – anion. Furthermore, the probable fluorescent quenching mechanisms of the two compounds have also been studied.

Recent Advances on the Applications of Luminescent Pb2+-Containing Metal–Organic Frameworks in White-Light Emission and Sensing

“…(piperazine-1,4-diylbis (methylene))bis (phosphonic acid)) as the bridging ligands, under hydrothermal conditions. The compounds were demonstrated to be highly selective fluorescent probes for sensing thymine and VO 3 − , respectively, via fluorescent quenching (Supplementary Figure S4) (Cai et al, 2018). Multi-responsive and multifunctional MOFs were also obtained on introduction of N-heterocycles onto the aromatic linkage moieties.…”