Investigation of solutions of iron(II) complexes with tris(pyrazol-1-yl)methane, possessing the spin-crossover phenomenon

• Published in: Inorganic chemistry communications 2022-12, Vol.146, p.110112, Article 110112
• Main Authors: Shakirova, Olga, Kokovkin, Vasily, Korotaev, Evgeny, Mironov, Igor, Lavrenova, Ludmila
• Format: Article
• Language: English
• Subjects: Conductometry; Iron(II) complex; Solution in DMFA; Static magnetic susceptibility; Tris(pyrazol-1-yl)methane; UV and visible spectrometry
• ISSN: 1387-7003; 1879-0259
• DOI: 10.1016/j.inoche.2022.110112

[Display omitted] •The solutions of iron(II) complex with Spin-crossover were studied by methods of static magnetic susceptibility, UV and visible spectrometry and conductometry.•Solutions of the [Fe(HC(pz)3)2]ns2 in DMFA are characterized by a high degree of dissociation by the type of 1,1-charging electrolyte.•The values of the electrolyte dissociation constant is calculated as pK = 2.3.•The activation energy of the charge transfer process is equal Ea = 5815 J/mol.•Change in the spin state of the central atom of the complex in solution does not lead to changes in the nature of electrical conductivity and does not change Ea. Using methods of static magnetic susceptibility, UV and visible spectrometry and conductometry, dimethylformamide solution of iron(II) complex with tris(pyrazol-1-yl)methane (HC(pz)3) having the composition [Fe(HC(pz)3)2]ns2 (ns = 2-naphthalene sulfonate) has been studied. In solution, as in the solid state, this compound exhibits a spin crossover of 1A1 ↔ 5T2, while in solution it is shifted to a region of lower temperatures and is sharper. It is shown that at a given concentration of 2.5 × 10−4 mol/L at 298 K, the molar electrical conductivity for the [Fe(HC(pz)3)2]ns2 complex in dimethylformamide is Λ298k = 100 ± 2 Ohm−1cm2 mol−1. Solutions of the [Fe(HC(pz)3)2]ns2 complex in a polar aprotic solvent with high dielectric permittivity are characterized by a high degree of dissociation by the type of 1,1-charging electrolyte. The dependences of the logarithm of the electrical conductivity of the studied solutions as a function of the logarithm of concentration and of 1/T are linear. The values of the electrolyte dissociation constant, pK = 2.3, and the activation energy of the charge transfer process, Ea = 5815 J/mol, are calculated. It is shown that a change in the spin state of the central atom of the complex in solution does not lead to changes in the nature of electrical conductivity and does not change Ea.