Exploring thiophene-2-acetate and thiophene-3-acetate binding modes towards the molecular and supramolecular structures and photoluminescence properties of Pb(ii) polymers

Abstract

To evaluate the impact of the flexible positional isomeric ligands thiophene-2-acetate (2tpacCOO) and thiophene-3-acetate (3tpacCOO) on the construction and self-assembly process of Pb(II) polymers, two novel compounds, [Pb(2tpacCOO)₂(H₂O)]_n (1) and [Pb(3tpacCOO)₂]_n (2), were prepared via a nonhydrothermal method with respect to green chemistry rules. The obtained polymers were fully characterized by elemental analysis, TG/DTG and PXRD, FT-IR, solid-state photoluminescence, DFT calculations and single-crystal X-ray diffraction. Each Pb(II) centre of 1 is 7-coordinated as a {PbO₇} chromophore while the Pb(II) centre of 2 is 6-coordinated as a {PbO₆} structure. The coordination polyhedron of 1 is best described as a distorted monocapped pentagonal pyramid, and 2 has a distorted trigonal prismatic shape. The crystallographic analysis and DFT calculations indicated the stereoactivity of the lone electron pair, which contributed to the hemidirected geometry of the Pb(II) environment. Due to the versatile binding modes of the ligands, complex 1 forms 1D stair-like chains with an SP 1-periodic net (4,4)(2,0) topology, and the underlying net of 2 is determined to have a 1D 2,4C4 topology. It is worth noting that the crystal structures of the obtained polymers are stabilized mainly by many hydrogen bonds as well as Pb⋯S and Pb⋯π tetrel interactions. Moreover, the PL data demonstrate the different influences of the isomers of linkers on photoluminescence properties. Polymer 1 might be a good candidate for obtaining solid-state photoluminescent materials.