Structures, properties and topologies of two layered compounds based on 2-carboxethyl(phenyl)phosphinic acid

Abstract

Hydrothermal syntheses of 2-carboxyethyl(phenyl)phosphinic acid (H₂CEPPA) with Bi(NO₃)₃ and Cd(NO₃)₂ produce two layered complexes [Bi₂(μ₃-O)(CEPPA)₂]_n (1) and [Cd(HCEPPA)₂]_n (2). Compound 1 is comprised of [Bi₄(μ₃-O)₂(POO)₄(COO)₄] SBUs which grow into a double wave-like 2D layer with–CH₂CH₂–spacers. Compound 2 crystallizes in the orthorhombic noncentrosymmetric space group Pca2₁, exhibiting a double lattice-like layer. Through edge-to-face d∙∙∙π stacking, a 3D supramolecular framework is formed based on 2D lattices. Topological analyses indicate that 1 and 2 have sql (or Shubnikov tetragonal plane net) and kgd (or Shubnikov (3.6.3.6) plane net) topological networks respectively. 1 and 2 are isolated as single crystal pure phases, which is confirmed by powder XRD. TGA shows high thermal stabilities with decomposition temperatures of 1 and 2 being 373 and 303°C respectively. The fluorescent spectra exhibit fluorescence quenching in 1 and sharp emission at 292 nm in 2, which is assigned to intraligand emission.