Versatility of Amide-Functionalized Co(II) and Ni(II) Coordination Polymers: From Thermochromic-Triggered Structural Transformations to Supercapacitors and Electrocatalysts for Water Splitting

Abstract

The new 2D coordination polymers (CPs) [M(L) 2 (H 2 O) 2 ] n [M = Co II (1) and Ni II (2); L = 4-(pyridin-3-ylcarbamoyl)benzoate] were synthesized from pyridyl amide-functionalized benzoic acid (HL). They were characterized by elemental, Fourier transform infrared, thermogravimetric, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (XRD) structural analyses. Single-crystal XRD analysis revealed the presence of a 2D polymeric architecture, and topological analyses disclose a 2,4-connected binodal net. A thermochromic effect leads to the production of two new CPs, 1′ and 2′, by heating at ca. 220 °C, accompanied by a color change from orange to purple in the case of 1 and from blue to green in the case of 2. The transformation of 1 to 1′ takes place through an intermediate (1a) with a different twist of the L − ligand, leading to the formation of a 1D polymeric architecture, as proven by single-crystal XRD analysis. The addition of water or keeping 1′ or 2′ in air for several days leads to regeneration of 1 or 2, respectively. The thermochromic-triggered structural transformations of 1 and 2 were further substantiated by PXRD and UV−vis ground-state diffuse-reflectance absorption studies. The supercapacitance ability of the CPs 1 and 2 and a Ni−Co composite (made from mixing the CPs 1 and 2) was investigated by electroanalytical techniques, such as cyclic voltammetry and electrochemical impedance spectroscopy. The CP 2 exhibits the highest specific capacity of 273.8 C g −1 at an applied current density of 1.5 A g −1 . These newly developed CPs further act as electrocatalysts for the water-splitting reaction.

Metal–Organic Frameworks Constructed from Iron‐Series Elements for Supercapacitors

“…[107] Even sometimes, Co and Ni metals reacting with similar building blocks could afford the isostructural architectures. [108] Therefore, we put it together to discuss the current trends of Co-and Ni-based MOFs as SCs electrodes in this review (Table 1). [93] Copyright 2014, Elsevier.…”

“…When these new-emerging MOFs have been documented as SCs electrodes, some have also been reported to achieve good electrochemical results. [108,[127][128][129][130][131]…”

Coexistence of Naked-Eye Mechanochromism, Vapochromism, and Thermochromism in a Soft Crystalline Layered Nickel(II) Coordination Polymer

“…25−27 Heat frequently induces the loss of lattice and coordinated solvent molecules, resulting in a structural transformation accompanying with the change in coordination environment. 24,29 Until now, there are many reports on mechanochromic behavior in coordination compounds. The reported mechanochromism generally occurs with a change in luminescent signal because most of them are constructed from 5d elements, such as Pt(II) and Au(I) ions, as well as some 3d 10 elements, such as Cu(I) and Zn(II) ions.…”

“…Ni­(II) ion is one of the 3d transition metals that have a variety of coordination numbers and geometries, each with its own visible color. ,− Consequently, it is suitable to use a Ni­(II) center for fabrication of a new multistimuli responsive chromic CP. Vapochromism of some Ni­(II) complexes has been reported. ,, For instance, Baho and colleagues showed that the addition of CH 3 CN vapor can cause a change in coordination modes of nitrate ligands, leading to a shift in d–d bands of a Ni­(II) complex and a change in its color .…”

“…Vapochromism of some Ni­(II) complexes has been reported. ,, For instance, Baho and colleagues showed that the addition of CH 3 CN vapor can cause a change in coordination modes of nitrate ligands, leading to a shift in d–d bands of a Ni­(II) complex and a change in its color . In case of thermochromism, it has been extensively observed in many Ni­(II) systems. − Heat frequently induces the loss of lattice and coordinated solvent molecules, resulting in a structural transformation accompanying with the change in coordination environment. , Until now, there are many reports on mechanochromic behavior in coordination compounds. The reported mechanochromism generally occurs with a change in luminescent signal because most of them are constructed from 5d elements, such as Pt­(II) and Au­(I) ions, as well as some 3d 10 elements, such as Cu­(I) and Zn­(II) ions. ,,− The mechanical force can alter metallophilic interactions between metal centers, resulting in the luminescent color change.…”