Counter Anion Effects on the Formation and Structural Transformations of Mo(vi)-Hydrazone Coordination Assemblies: Salts, Solvates, Co-Crystals, and Neutral Complexes

• Published in: Crystals (Basel) Vol. 12; no. 4; p. 443
• Main Authors: Mandarić, Mirna, Prugovečki, Biserka, Kekez, Ivana, Musija, Danijela, Parlov Vuković, Jelena, Cindrić, Marina, Vrdoljak, Višnja
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.04.2022
• Subjects: Acids; Anions; Cations; co-crystals; complex salts; Coordination compounds; coordination polymer; Crystallization; Crystals; hydrazone; Hydrazones; Ligands; Low temperature; Methanol; molybdenum; Molybdenum oxides; NMR spectroscopy; solvates; Synthesis; Toxicity; Vanillin
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst12040443

Complex salts [1H]X and [1H](XA)0.5·2MeOH, and co-crystals [1H]X·0.5VA (X = chloride or bromide, XA = chloranilate or bromanilate, VA = o-vanillin azine), comprising [MoO2(HL)(MeOH)]+ ([1H]+) cation (H2L = 3-methoxysalicylaldehyde isonicotinoyl hydrazone), were prepared either by solution-based synthesis or by mechanochemical synthesis. Whereas [1H]X salts were extremely sensitive to humidity, their stability could be reinforced by the azine incorporation into the complex network. Solvent-mediated transformations of [1H]X led to methanol co-ligand replacement and afforded complexes [MoO2(HL)X] (2Cl·MeOH, 2Cl, and 2Br·0.5MeCN). However, solvates [1H](XA)0.5·2MeOH, under the same conditions, gave stable complexes [1H](XA)0.5 in which methanol remained coordinated. The differences in the assembly’s behavior were attributed to the packing arrangements, the relative orientation of cations and anions, and interactions between them. Polymorph [MoO2(L)(MeOH)] (1), not attainable by other routes, was the only product when compounds [MoO2(HL)X] were treated with a weak base at low temperatures. Tetranuclear [MoO2(L)]4 and polynuclear [MoO2(L)]n (2) supramolecular isomers, concomitantly crystallized when the reaction was conducted solvothermally. All of the complexes were characterized using X-ray diffraction methods (SCXRD and PXRD), spectroscopic methods (ATR-IR and solution-state and solid-state MAS NMR), and elemental and thermal analyses. The cytotoxicity of the different types of compounds against THP-1 and HepG2 cells was also evaluated.