Mixed‐Ligand Oxidovanadium(IV/V) Complexes Chelated by α‐Hydroxycarboxylate and 2‐(1H‐Imidazol‐2‐yl)pyridine: Localized Structures and Gas Adsorption

• Published in: European journal of inorganic chemistry Vol. 2022; no. 2
• Main Authors: Xie, Zhen‐Lang, Yuan, Chang, Jin, Wan‐Tin, Zhou, Zhao‐Hui
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 18.01.2022
• Subjects: Adsorption; Bonding strength; Chelation; Citric acid; Coordination compounds; Gas adsorption; Glycolic acid; Hydrogen bonds; Inorganic chemistry; Ligand effects; Localization; Malate; Malic acid; Microchannels; Pyridines; Structure elucidation; Vanadium; Vanadium oxides; Water chemistry
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202100877

Monomeric oxidovanadium(IV) citrate and malate, [VO(H2cit)(Him‐py)] ⋅ H2O (1) and [VO(R,S‐Hmal)(Him‐py)] (2), and an additive of mixed‐valence oxidovanadium(IV/V) (1H‐imidazol‐2‐yl)pyridine [V2O2(μ2‐O)(glyc)(Him‐py)2(im‐py)] ⋅ [VO2(Him‐py)(im‐py)] ⋅ 9.5H2O (3) [Him‐py=2‐(1H‐imidazol‐2‐yl)pyridine, H4cit=citric acid, R,S‐H3mal=R,S‐malic acid, H2glyc=glycolic acid] have been isolated from the reactions of vanadyl sulfate with α‐hydroxycarboxylate (citrate, malate, and glycolate) and 2‐(1H‐imidazol‐2‐yl)pyridine in acidic solutions, respectively. The citrate or malate chelates to vanadium atom tridentately through α‐hydroxy, α‐carboxy and β‐carboxy groups that different with bidentate glycolate, while the other β‐carboxy acidic group of citrate in 1 remains uncoordinated and participates in strong hydrogen bonds with water molecules. Further substitution of 2‐(1H‐imidazol‐2‐yl)pyridine for citrate in 1 results in the formation of [VO2(Him‐py)(im‐py)]3 ⋅ 4.5H2O (4) in basic solution. With comparable chelation, 1 shares a similar V−Oα‐hydroxy distance [2.214(2) Å] with that observed in FeV‐cofactor [2.156av Å],[1] where a protonated model is suggested for the local chelated environment of FeV‐cofactor in citrate‐substituted V‐nitrogenase variant. Interestingly, 2D porous structure of additive 3 features two types of irregular microchannels with diameters of 16.6 and 6.4 Å, respectively, which can adsorb CO2 and O2 for 9.28 and 29.68 mg/g at 29.89 bar, respectively, while little or no adsorption for H2, N2, and CH4. Monomeric oxidovanadium(IV) citrate and malate, and an interesting additive of mixed‐valence oxidovanadium(IV/V) (1H‐imidazol‐2‐yl)pyridine have been obtained. A protonated model for the local chelated environment of citrate‐substituted FeV‐cofactor is suggested. Intriguingly, 2D porous structure of mixed‐valence oxidovanadium(IV/V) glycolate features two types of irregular microchannels, showing selective adsorptions for O2 and CO2 without H2, N2, and CH4.