NCI calculations for understanding a physical phase transition in (C6H14N2)[Mn(H2O)6](SeO4)2

• Published in: Solid state sciences Vol. 74; pp. 44 - 55
• Main Authors: Naïli, Houcine, François, Michel, Norquist, Alexander J., Rekik, Walid
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01.12.2017
• Subjects: Hybrid materials; NCI calculations; Phase transition; Supramolecular; Thermal decomposition; NCI calculations; Supramolecular; Thermal decomposition; Hybrid materials; Phase transition
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2017.10.006

An organically templated manganese selenate, (C6H14N2)[Mn(H2O)6](SeO4)2, has been synthesized by slow evaporation and crystallographically characterized. The title compound crystallizes at room temperature in the monoclinic centrosymmetric space group P21/n, with the following unit cell parameters: a = 7.2373(4) Å; b = 12.5600(7) Å; c = 10.1945(7) Å; β = 91.155(4)°, V = 926.50(10) Å3and Z = 2. Its crystal structure is built of manganese(II) cations coordinated by six water molecules in octahedral geometry, disordered dabcodiium cations and selenate anions, resulting in an extensive hydrogen-bonding network. Differential scanning calorimetry (DSC) measurement indicated that the precursor undergoes a reversible phase transition at about 216 and 218 K during the cooling and heating processes respectively. Below this temperature the title compound is noncentrosymmetric with space group P21 and lattice parameters a = 7.2033(8) Å; b = 12.4981(13) Å; c = 10.0888(11) Å; β = 91.281(2)°, V = 908.04(17) Å3 and Z = 2. The disorder-order transformation of the C atoms of (C6H14N2)2+ cation may drive the structural phase transition. The low temperature phase obtained by breaking symmetry presents a fully ordered structure. The noncovalent interaction (NCI) method was used not only to locate, quantify, and visualize intermolecular interactions in the high and low temperature phases but also to confirm the phase transition detected by DSC measurement. The thermal decomposition of this new compound proceeds through four stages giving rise to the manganese oxide as final product at 850 °C. Pure single crystals of (C6H14N2)[Mn(H2O)6](SeO4)2 with a disordered organic part were successfully grown at room temperature. This new hybrid material undergoes a reversible phase transition at about 217 K detected by DSC and confirmed by DRX and NCI calculations. The low temperature phase presents a fully ordered structure. [Display omitted]