Synthesis, crystal structures and reversible solid-state crystal-to-crystal transformation of three isostructural lead(ii) halide coordination polymers with different luminescence properties in bulk and nanoscale

Abstract

Novel three dimensional (3D) isostructural lead(II) halide coordination polymers [Pb(INO)X]_n (X = Cl (1), Br (2), I (3); INO = isonicotinic acid N-oxide) have been synthesized via a branched-tube method. The compounds have been characterized by IR spectroscopy and powder X-ray diffraction (PXRD) analysis and their crystalline structures have been determined by single-crystal X-ray diffraction. Isostructural compounds 1–3 crystallize in the orthorhombic crystal system with the Pbcn space group. Two N-oxide groups of INO anions connect to a pair of adjacent Pb(II) ions to create a one-dimensional (1D) infinite zigzag chain and carboxylate groups connect the lead(II) ions resulting in [Pb₂O₂] units. Nanoplates of compounds 1–3 have also been synthesized under ultrasonic irradiation and characterized by IR spectroscopy, SEM and PXRD. Moreover, compounds 1–3 exhibited reversible solid-state crystal-to-crystal transformation under mechanochemical reactions. The thermal stability of these crystalline materials has been presented. The fluorescence features of these compounds have also been studied in solution for bulk and nanostructures at ambient temperature.