Hybrid Chlorides with Methylhydrazinium Cation: [CH₃NH₂NH₂]CdCl₃ and Jahn-Teller Distorted [CH₃NH₂NH₂]CuCl₃

Abstract

The synthesis, structural, phonon, optical, and magnetic properties of two hybrid organic-inorganic chlorides with monoprotonated methylhydrazinium cations (CH3NH2NH2+, MHy+), [CH3NH2NH2]CdCl3 (MHyCdCl3), and [CH3NH2NH2]CuCl3 (MHyCuCl3), are reported. In contrast to previously reported MHyMIICl3 (MII = Mn2+, Ni2+, and Co2+) analogues, neither compound undergoes phase transitions. The MHyCuCl3 has a crystal structure familiar to previous crystals composed of edge-shared 1D chains of the [CuCl5N] octahedra. MHyCuCl3 crystallizes in monoclinic P21/c symmetry with MHy+ cations directly linked to the Cu2+ ions. The MHyCdCl3 analogue crystallizes in lower triclinic symmetry with zig-zag chains of the edge-shared [CdCl6] octahedra. The absence of phase transitions is investigated and discussed. It is connected with slightly stronger hydrogen bonding between cations and the copper–chloride chains in MHyCuCl3 due to the strong Jahn–Teller effect causing the octahedra to elongate, resulting in a better fit of cations in the accessible space between chains. The absence of structural transformation in MHyCdCl3 is due to intermolecular hydrogen bonding between two neighboring MHy+ cations, which has never been reported for MHy+-based hybrid halides. Optical investigations revealed that the bandgaps in Cu2+ and Cd2+ analogues are 2.62 and 5.57 eV, respectively. Magnetic tests indicated that MHyCuCl3 has smeared antiferromagnetic ordering at 4.8 K.

Keywords

• methylhydrazinium
• organic-inorganic hybrid
• chloride
• phonon
• crystal structure
• Jahn–Teller effect