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15 pages, 3002 KiB

Open AccessArticle

Study of the Counter Cation Effects on the Supramolecular Structure and Electronic Properties of a Dianionic Oxamate-Based {Ni^II₂} Helicate

by Cintia A. Simosono, Rafaela M. R. da Silva, Nathália R. De Campos, Marye Agnes R. Silva, Antônio C. Doriguetto, Leonã S. Flores, Charlane C. Correa, Tatiana R. G. Simões, Ana Karoline S. M. Valdo, Felipe T. Martins, Flávio Garcia, Guilherme P. Guedes, Breno R. L. Galvão, Juliana Cancino-Bernardi, Ricardo D. dos Reis, Humberto O. Stumpf, Danielle D. Justino, Paulo F. R. Ortega, Walace D. do Pim, Miguel Julve and Maria Vanda Marinho Show full author list Hide full author list

Molecules 2023, 28(5), 2086; https://doi.org/10.3390/molecules28052086 - 23 Feb 2023

Cited by 2 | Viewed by 1580

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 {Ni^II₂}. SHAPE software calculations indicate that the coordination geometry of all the Ni^II atoms in 1 and 2 is a distorted octahedron (O_h) whereas the coordination environments for K1 and K2 atoms in 1 are Snub disphenoid J84 (D_2d) and distorted octahedron (O_h), respectively. The {Ni^II₂} 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 {Ni^II₂} 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 Ni^II/Ni^I pair being mediated by OH^– ions) but with differences in formal potentials that reflect changes in the energy levels of molecular orbitals. The Ni^II 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. Full article

(This article belongs to the Special Issue Metallosupramolecular Functional Helicates)

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12 pages, 2818 KiB

Open AccessFeature PaperArticle

Investigating the Conformations of a Family of [M₂L₃]⁴⁺ Helicates Using Single Crystal X-ray Diffraction

by Matthew J. Wallis, Hyunsung Min, Leonard F. Lindoy and Feng Li

Molecules 2023, 28(3), 1404; https://doi.org/10.3390/molecules28031404 - 01 Feb 2023

Cited by 4 | Viewed by 1480

Abstract

We present five new dinuclear triple helicate compounds of types [Mn₂L₃](ClO₄)₄, [Co₂L₃](BF₄)₄, [Ni₂L₃](BF₄)₄, [Cu₂L₃](BF₄ [...] Read more.

We present five new dinuclear triple helicate compounds of types [Mn₂L₃](ClO₄)₄, [Co₂L₃](BF₄)₄, [Ni₂L₃](BF₄)₄, [Cu₂L₃](BF₄)₄, and [Zn₂L₃](BF₄)₄, where L is a previously reported semi-rigid ligand incorporating two α-diimine primary donor groups and two secondary 4-pyridyl donor groups. All complexes have been characterized in both solution and the solid state. Single crystal X-ray diffraction studies were used to probe the variation in the respective helical structures as the coordinated metal ion was altered, including the effect on the orientations of the secondary binding domains. The influence of the metal ion size, the spin state in the case of Fe(II), and the presence of Jahn-Teller distortions on the overall helical structure has been investigated. These results form a basis for the design and construction of new large metallosupramolecular architectures which manifest properties associated with the constituent helical metalloligand units. Full article

(This article belongs to the Special Issue Metallosupramolecular Functional Helicates)

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14 pages, 5511 KiB

Open AccessArticle

pH and Salt-Assisted Macroscopic Chirality Inversion of Gadolinium Coordination Polymer

by Ting Hou, Lan-Qing Wu, Yan Xu, Song-Song Bao and Li-Min Zheng

Molecules 2023, 28(1), 163; https://doi.org/10.3390/molecules28010163 - 25 Dec 2022

Cited by 5 | Viewed by 1505

Abstract

The precise adjustment of handedness of helical architectures is important to regulate their functions. Macroscopic chirality inversion has been achieved in organic supramolecular systems by pH, metal ions, solvents, chiral and non-chiral additives, temperature, and light, but rarely in coordination polymers (CPs). In particular, salt-assisted macroscopic chirality inversion has not been reported. In this work, we carried out a systematic investigation on the role of pH and salt in regulating the morphology of CPs based on Gd(NO₃)₃ and R-(1-phenylethylamino)methylphosphonic acid (R-pempH₂). Without extra NO₃⁻, the chirality inversion from the left-handed superhelix R-M to the right-handed superhelix R-P can be achieved by pH modulation from 3.2 to 3.8. The addition of NaNO₃ (2.0 eq) at pH 3.8 results in an inversion of chiral sense from R-P to R-M as a pure phase. To our knowledge, this is the first example of salt-assisted macroscopic helical inversion in artificial systems. Full article

(This article belongs to the Special Issue Metallosupramolecular Functional Helicates)

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