Structural, magnetic and photoluminescence properties of new hybrid hypophosphites: discovery of the first noncentrosymmetric and two cobalt-based members

Dalton Trans. 2022 Jun 13;51(23):9094-9102. doi: 10.1039/d2dt01212j.

Abstract

Hybrid organic-inorganic perovskites comprising hypophosphite ligands are emerging functional materials exhibiting magnetic, photoluminescence, negative thermal expansion and negative linear compressibility behaviours. This work reports five novel hypophosphite perovskites, [A]M(H2POO)3 (A = pyrrolidinium (PYR+), guanidinium (GUA+) and imidazolium (IM+); M = Cd2+ and Co2+). [GUA]Cd(H2POO)3, [IM]Cd(H2POO)3, [GUA]Co(H2POO)3 and [IM]Co(H2POO)3 belong to the centrosymmetric trigonal Rc, monoclinic P21/c, monoclinic I2/m, and orthorhombic Pbca space groups, respectively, while [PYR]Cd(H2POO)3 crystallizes in the noncentrosymmetric orthorhombic space group Aea2. The polar order of PYR+ cations was confirmed by observation of moderate second harmonic generation (SHG) activity. Magnetic studies reveal that [GUA]Co(H2POO)3 and [IM]Co(H2POO)3 are weak ferromagnets with the ordering temperatures higher compared to their manganese analogues. Upon ultraviolet excitation, the cadmium counterparts exhibit purplish-blue emissions at low temperatures, which decrease on heating. Analysis of the photoluminescence data reveals that the emission quenching decreases with decreasing distortion of the cadmium-hypophosphite framework. Discovery of the new hypophosphites exhibiting magnetic or polar order and photoluminescence properties shows that hypophosphite perovskites offer a promising platform for generating new functional materials, including those that are light emitting, ferroelectric and multiferroic.

MeSH terms

  • Cadmium*
  • Cobalt*
  • Ligands
  • Magnetic Phenomena
  • Magnets

Substances

  • Ligands
  • Cadmium
  • Cobalt