Crystal structure of formamidinium–lead–chloride–dimethyl sulfoxide and phase relationship of related crystalline systems

Abstract

Single crystals of formamidinium (FA)–lead–chloride–dimethyl sulfoxide (DMSO) solvate, [CH(NH₂)₂]Pb(C₂H₆OS)Cl₃, were synthesized from a DMSO ((CH₃)₂SO) solution in which FA–chloride (CH(NH₂)₂Cl) and lead(II) chloride (PbCl₂) were dissolved. Single-crystal X-ray diffraction studies revealed that [CH(NH₂)₂]Pb(C₂H₆OS)Cl₃ exhibited a monoclinic (P2₁/c) symmetry in the temperature range of 113–293 K. Interestingly, the oxygen atom of DMSO was involved in the distorted [PbOCl₅] octahedra, which form a [Pb₂O₂Cl₉] dimer unit by edge-sharing. These dimer units form a pseudo-2D zigzag layer elongated parallel to the (100) plane via corner sharing. The FA⁺ cation was structurally ordered and aligned between the pseudo-2D zigzag layers at the voids surrounded by the [Pb₂O₂Cl₉] dimer units. The formation enthalpy of the DMSO solvate calculated using the density functional theory method explains the phase stability of the FAPbCl₃–DMSO solvate.