Physical and Structural Characterization of Imidazolium-Based Organic–Inorganic Hybrid: (C₃N₂H₅)₂[CoCl₄]

Abstract

(C3N2H5)2[CoCl4] (ICC) was characterized in a wide temperature range by the single-crystal X-ray diffraction method. Differential scanning calorimetry revealed two structural phase transitions: continuous at 245.5 K (from phase I to II) and a discontinuous one at 234/237 K (cooling/heating) (II → III). ICC adopts monoclinic space groups C2/c and P21/c in phase (I) and (III), respectively. The intermediate phase (II) appears to be incommensurately modulated. Dynamic properties of polycrystalline ICC were studied by means of dielectric spectroscopy and proton magnetic resonance ((1)H NMR). The presence of a low frequency dielectric relaxation process in phase III reflects libration motion of the imidazolium cations. The temperature dependence of the (1)H spin-lattice relaxation time indicated two motional processes with similar activation energies that are by about an order of magnitude smaller than the activation energy obtained from dielectric studies. There are no abrupt changes in the (1)H relaxation time at the phase transitions indicating that the dynamics of the imidazolium rings gradually varies with temperature; that is, it does not change suddenly at the phase transition. Negative values of the Weiss constant and the intermolecular exchange parameter were obtained, confirming the presence of a weak antiferromagnetic interaction between the nearest cobalt centers. Moreover, the magnitude of zero field splitting was determined. The AC susceptibility measurements show that a slow magnetic relaxation is induced by small external magnetic field.

Spin Hamiltonian Parameters for Co2+Ions in PbMoO4Crystal - Interplay between the Fictitious Spin S'=1/2 and the Effective Spin S̃ =3/2

“…The obtained g z values smaller than the free-electron g e = 2.0023 seem somewhat controversial in view of recent findings indicating the opposite relation for Co 2+ (S = 3/2) ions at tetrahedral sites, e.g. g z = 2.240 [28] and g z = 2.362 [29]. On the other hand, the measured g i values for Co 2+ (S = 1/2) ions indicate highly asymmetric g-tensor and several cases of g z < 2.0023 have been reported, e.g.…”

Crystal structures of an imidazo[1,5-a]pyridinium-based ligand and its (C13H12N3)2[CdI4] hybrid salt

“…The exploration of hybrid compounds based on other polyhedra and connectivity through control of their chemical composition and structural dimensionality may bring applications in new areas of science and technology. Hybrid tetrahalometallates are a promising variety that can demonstrate properties of multiferroics (-K 2 SeO 4 analogues) and ionic liquids, show luminescence and a series of solid-phase transitions (García-Saiz et al, 2014;Piecha-Bisiorek et al, 2016;Jiang et al, 2017).…”

“…The exploration of hybrid compounds based on other polyhedra and connectivity through control of their chemical composition and structural dimensionality may bring applications in new areas of science and technology. Hybrid tetrahalometallates are a promising variety that can demonstrate properties of multiferroics (-K 2 SeO 4 analogues) and ionic liquids, show luminescence and a series of solid-phase transitions (García-Saiz et al, 2014;Piecha-Bisiorek et al, 2016;Jiang et al, 2017).The serendipitous discovery of the formation of 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, L + , in the oxidative condensation-cyclization of 2-pyridinecarbaldehyde (2-PCA) and CH 3 NH 2 ÁHCl in methanol and the following preparation of the fluorescent [L] 2 [ZnCl 4 ] hybrid salt in the presence of Zn 2+ ions prompted our research on organic- ISSN 2056-9890 inorganic halometalates with substituted imidazo[1,5-a]pyridinium cations (Buvaylo et al, 2015;Vassilyeva et al, 2019). The use of methylamine hydrochloride instead of its conventional aqueous solution appeared to promote the cyclocondensation with the formation of L + instead of the expected neutral Schiff base.…”

Ionic Liquid–Liquid Chromatography: A New General Purpose Separation Methodology

“…In the chloride ionic liquid phase, the metals are presumed to exist as the tetrahedral [MCl 4 ] 2-complexes (see Fig. 25) [187][188][189]. The three metals distribute themselves between both phases, with the nickel(II) and cobalt(II) salts both preferring to dissolve mostly in the aqueous phase, and the copper(II) salt preferring the ionic liquid phase.…”