Abstract
The product obtained from the reaction of pyridine-2,3-di-carb-oxy-lic acid and hydrated copper(II) chloride in hot aqueous NaOH solution was determined by low temperature X-ray diffraction to be [Cu3(C6H4NO3)4(OH)2(H2O)2] n or [Cu3(μ-OH)2(μ-nicNO)4(H2O)2] n (nicNO is pyridine-3-carboxyl-ate N-oxide), a structure obtained from room temperature data and reported previously. The present determination is improved in quality and treatment of the H atoms. A Hirshfeld surface analysis of the inter-molecular inter-actions is presented.
Highlights
> 3(I) in NICTCU and 0.0538 for 3349 with I > 2(I) in NICTCU01
During the course of this work, we found two prior reports of this structure [NICTCU (Knuutilla, 1981) and NICTCU01 (Kang et al, 2020)], both obtained with room-temperature data
One deficiency of the NICTCU structure is the free refinement of hydrogen-atom parameters, a risky procedure with room-temperature data when heavy atoms are present, which led to C—H distances for the aromatic rings varying from 0.97 (2) to 0.84 (3) Aand O—H distances of 0.77 (3) to 0.41 (4) A, the last three being unrealistic
Summary
N-oxidation of the pyridine ring can significantly increase its electron-donating ability because the charge-polarized pyridine-N-oxide moiety can donate three pairs of electrons while a neutral nitrogen atom in pyridine only gives one pair of electrons. Metal complexes of pyridine-N-oxide ligands have been found to be useful in the selective adsorption and separation of gases (CO2 over CH4) and as anti-HIV and luminescent agents (Noro et al, 2015; Xiong et al, 2014; Balzarini et al, 2005; Lis et al, 2002) These features have motivated our interest in the chemistry of carboxylic acid derivatives of pyridine-N-oxide for investigating the influence of the N-oxide moiety on the coordination mode(s) in the crystal lattice (Mirzaei et al, 2020; Hosseini-Hashemi et al, 2018, 2019; Bazargan et al, 2016, 2020; Mirzaei, EshtiaghHosseini, Bazargan et al, 2015; Shahbazi et al, 2017; Mirzaei, Eshtiagh-Hosseini, & Bazargan, 2015). Symmetry codes: (i) Àx + 1, Ày + 1, Àz + 1; (ii) x + 1, y + 1, z
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