Authors: Cintia A. Simosono | Rafaela M. R. da Silva | Nathália R. de Campos | Marye Agnes R. Silva | A.C. Doriguetto | Leonã S. Flôres | Charlane C. Corrêa | Tatiana R. G. Simões | Ana Karoline Silva Mendanha Valdo | Felipe Terra Martins | F. García | Guilherme P. Guedes | Breno R. L. Galvão | Juliana Cancino‐Bernardi | R. D. dos Reis | Humberto O. Stumpf | Danielle Diniz Justino | Paulo F.R. Ortega | Walace D. do Pim | Miguel Julve | Maria Vanda Marinho
Source: Molecules (article, 2023-02-23)
Field: Chemistry — Inorganic Chemistry

Study of the Counter Cation Effects on the Supramolecular Structure and Electronic Properties of a Dianionic Oxamate-Based {NiII2} Helicate Herein, we describe the synthesis, crystal structure, and electronic properties of {[K<sub>2</sub>(dmso)(H<sub>2</sub>O)<sub>5</sub>][Ni<sub>2</sub>(H<sub>2</sub>mpba)<sub>3</sub>]·dmso·2H<sub>2</sub>O}<sub>n</sub> (<b>1</b>) and [Ni(H<sub>2</sub>O)<sub>6</sub>][Ni<sub>2</sub>(H<sub>2</sub>mpba)<sub>3</sub>]·3CH<sub>3</sub>OH·4H<sub>2</sub>O (<b>2</b>) [dmso = dimethyl sulfoxide; CH<sub>3</sub>OH = methanol; and H<sub>4</sub>mpba = 1,3-phenylenebis(oxamic acid)] bearing the [Ni<sub>2</sub>(H<sub>2</sub>mpba)<sub>3</sub>]<sup>2-</sup> helicate, hereafter referred to as {Ni<sup>II</sup><sub>2</sub>}. SHAPE software calculations indicate that the coordination geometry of all the Ni<sup>II</sup> atoms in 1 and 2 is a distorted octahedron (O<sub>h</sub>) whereas the coordination environments for K1 and K2 atoms in 1 are Snub disphenoid J84 (D<sub>2d</sub>) and distorted octahedron (O<sub>h</sub>), respectively. The {Ni<sup>II</sup><sub>2</sub>} helicate in <b>1</b> is connected by K<sup>+</sup> counter cations yielding a 2D coordination network with <b>sql</b> topology. In contrast to <b>1</b>, the electroneutrality of the triple-stranded [Ni<sub>2</sub>(H<sub>2</sub>mpba)<sub>3</sub>] <sup>2-</sup> dinuclear motif in <b>2</b> is achieved by a [Ni(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> complex cation, where the three neighboring {Ni<sup>II</sup><sub>2</sub>} units interact in a supramolecular fashion through four <i>R<sub>2</sub><sup>2</sup></i>(10) homosynthons yielding a 2D array. Voltammetric measurements reveal that both compounds are redox active (with the Ni<sup>II</sup>/Ni<sup>I</sup> pair being mediated by OH<sup>-</sup> ions) but with differences in formal potentials that reflect changes in the energy levels of molecular orbitals. The Ni<sup>II</sup> ions from the helicate and the counter-ion (complex cation) in <b>2</b> can be reversibly reduced, resulting in the highest faradaic current intensities. The redox reactions in <b>1</b> also occur in an alkaline medium but at higher formal potentials. The connection of the helicate with the K<sup>+</sup> counter cation has an impact on the energy levels of the molecular orbitals; this experimental behavior was further supported by X-ray absorption near-edge spectroscopy (XANES) experiments and computational calculations. Supramolecular chemistry ; Chemistry ; Octahedron ; Crystallography ; Ion ; Redox ; Coordination geometry ; Crystal structure ; Stereochemistry ; Coordination complex ; Inorganic chemistry ; Molecule ; Hydrogen bond ; Metal ; Organic chemistry Metal-Organic Frameworks: Synthesis and Applications ; Magnetism in coordination complexes ; Crystallography and molecular interactions