Analysis of solvent-accessible voids and proton-coupled electron transfer of 2,6-bis(1H-imidazol-2-yl)pyridine and its hydrochloride

Author(s)

Guerra, Renan B. ; Huamani, Luis S. C. ; Tenorio, Juan C. ; Guimaraes, Willian M. ; Bonacin, Juliano A. ; Barboza Formiga, Andre Luiz

• Document type: Journal article
• Source: ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY; v. 75, p. 20-pg., 2019-10-01.

Abstract

The crystal structures of the solid form of solvated 2,6-bis(1H-imidazol-2-yl)pyridine (H(2)dimpy) trihydrate, C11H9N5 center dot 3H(2)O center dot[+solvent], I, and its hydrate hydrochloride salt 2-[6-(1H-imidazol-2-yl)pyridin-2-yl]-1H-imidazol-3-ium chloride trihydrate, C11H10N5+center dot Cl-center dot 3H(2)O, II, are reported and analysed in detail, along with potentiometric and spectrophotometric titrations for evaluation of the acid-base equilibria and proton-coupled electron-transfer reactions. Compound I crystallizes in the high-symmetry trigonal space group P3(2)21 with an atypical formation of solvent-accessible voids, as a consequence of the 3(2) screw axis in the crystallographic c-axis direction, which are probably occupied by uncharacterized disordered solvent molecules. Additionally, the trihydrated chloride salt crystallizes in the conventional monoclinic space group P2(1)/c without the formation of solvent-accessible voids. The acid-base equilibria of H(2)dimpy were studied by potentiometric and spectrophotometric titrations, and the results suggest the formation of H(3)dimpy(+) (pK(a1) = 5.40) and H(4)dimpy(2+) (pK(a2) = 3.98), with the electrochemical behaviour of these species showing two consecutive irreversible proton-coupled electron-transfer reactions. Density functional theory (DFT) calculations corroborate the interpretation of the experimental results and support the assignment of the electrochemical behaviour. (AU)

• FAPESP's process: 14/50906-9 - INCT 2014: in Functional Complex Materials
• Grantee: Fernando Galembeck
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/23960-0 - Study of the mechanism of water oxidation by catalysts operating at pH7 and its incorporation in electrodes printed in 3D
• Grantee: Juliano Alves Bonacin
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/22127-2 - Development of novel materials strategic for integrated analytical devices
• Grantee: Lauro Tatsuo Kubota
• Support Opportunities: Research Projects - Thematic Grants