Study of the Counter Cation Effects on the Supramolecular Structure and Electronic Properties of a Dianionic Oxamate-Based {NiII2} Helicate

Abstract

Herein, we describe the synthesis, crystal structure, and electronic properties of {[K2(dmso)(H2O)5][Ni2(H2mpba)3]·dmso·2H2O}n (1) and [Ni(H2O)6][Ni2(H2mpba)3]·3CH3OH·4H2O (2) [dmso = dimethyl sulfoxide; CH3OH = methanol; and H4mpba = 1,3-phenylenebis(oxamic acid)] bearing the [Ni2(H2mpba)3]2− helicate, hereafter referred to as {NiII2}. SHAPE software calculations indicate that the coordination geometry of all the NiII atoms in 1 and 2 is a distorted octahedron (Oh) whereas the coordination environments for K1 and K2 atoms in 1 are Snub disphenoid J84 (D2d) and distorted octahedron (Oh), respectively. The {NiII2} helicate in 1 is connected by K+ counter cations yielding a 2D coordination network with sql topology. In contrast to 1, the electroneutrality of the triple-stranded [Ni2(H2mpba)3] 2− dinuclear motif in 2 is achieved by a [Ni(H2O)6]2+ complex cation, where the three neighboring {NiII2} units interact in a supramolecular fashion through four R22(10) homosynthons yielding a 2D array. Voltammetric measurements reveal that both compounds are redox active (with the NiII/NiI pair being mediated by OH– ions) but with differences in formal potentials that reflect changes in the energy levels of molecular orbitals. The NiII ions from the helicate and the counter-ion (complex cation) in 2 can be reversibly reduced, resulting in the highest faradaic current intensities. The redox reactions in 1 also occur in an alkaline medium but at higher formal potentials. The connection of the helicate with the K+ 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.

Intensity and lifetime ratiometric luminescent thermometer based on a Tb(iii) coordination polymer

“…During the synthesis of 1 , several experiments were conducted. This is because it is widely recognized that factors such as temperature, molar ratio of reagents, geometric characteristics, and coordination sites of the organic ligands 27–30 can have a significant impact on crystal growth. Moreover, the choice of synthetic strategies, such as stirring, 9,31 diffusion, 32 solvothermal (particularly when mixed organic solvents are employed), 8 and hydrothermal (used when water is the only solvent), 22,33 can also influence the process.…”

Nitro group and K+-based secondary building units for the self-assembly of 3D coordination polymers built on dinuclear dianionic helicate connectors

“…Dinuclear anionic triply stranded helicates are rare species. In fact, to the best of our knowledge, there are only a few examples: polymeric Ti 4+ or V 4+ helicates 37,38 based on catecholate-imine ligands, 2D coordination polymers of Ni 2+ , 39,40 containing pyridine-carboxamide or polyoxamate-type ligands, and two coordination polymers based on Fe 3+ and catecholamide or salicylic acid–carboxamide ligand. 41,42 In some of these compounds, the helicates act as metalloligands to alkali metal cations, Fig.…”

Crystal structure, magnetic properties and theoretical study of a bithiazolebis(oxamate)-containing [NiII3] helicate

“…12–14 In so doing, a plethora of tailor-made oligonuclear SCCs like mesocates, grids and cages with interesting magnetic properties were achieved using di- or polytopic oxamates as ligands. 15–26 High-nuclearity SCCs, from penta- up to nonanuclear species, were obtained through the metalloligand approach by using oxamato-based di- and trinuclear SCCs as ligands toward coordinatively unsaturated mononuclear metal complexes with different capping ligands. 27,28 In the lack of capping ligands, coordination polymers of varying dimensionalities ( n D, n = 1–3) and topologies have been alternatively obtained 29–31 and, occasionally, hexa-, deca- and dodecanuclear wheels.…”