Construction of Pyrazine-Appended 1D and 3D Cobalt(II) Succinate Coordination Polymers: Influence of Solvent on Architectures and Applications in Gas Adsorption and NAC Detection

Abstract

An underexplored reaction of pyrazine (rigid and linear) and succinic acid (flexible) with Co­(NO3)2·6H2O afforded four new coordination polymers (CPs): [Co­(H2O)­(pyz)­(suc)] (1), [Co­(H2O)2(pyz)­(suc)] (2), [Co­(H2O)4(pyz)]­(suc) (3) and [Co2(H2O)2(pyz)­(suc)2] (4), as well as [Co­(HCO2)2(pyz)] (5) being lately reported along with well-known 6 and 7. The CPs were obtained as stable crystalline materials and characterized by conventional solid-state techniques, including X-ray crystallography. Hydrothermally produced compounds 1 and 2 were both 3D CPs. While 3 and 4 obtained under ambient/solvothermal conditions in DMSO generated 1D and 3D structures, 5 isolated from DMF under solvothermal conditions had a 3D structure. The topologies of the coordination polymers 1–7 were described by underlying nets 3D 5-c fet, 3D 4-c cds, 1D 2-c 2C1, 3D 5-c bnn, 3D 6-c rob, 1D 2-c 2C1, and 3D 6-c pcu, respectively. The plot of χM –1 versus T was essentially linear in the entire temperature range following the Curie–Weiss law with a Curie constant (C) of 2.525 and a negative Weiss constant (ϕ) of −46.24 K, suggesting weak antiferromagnetic (AF) exchange interactions. CO2 and N2 adsorption studies of 1–5 featured type III isotherms. 1 was found to show remarkably higher quenching efficiencies for nitrophenols (η = 98% for o-NP) over other NACs. The Stern–Volmer plot exhibited deviation in linearity with K sv values about 200 times greater than that for the simplest nitroaromatic compound (NB), signifying its exclusive quenching ability toward 1. The LOD for p-NP addition to 1 was found to be 0.995 ppm.

Structural, Spectroscopic Characterization and Application of a Co(II) Coordination Polymer [Co(suc)(bpm)] ⋅ 2H2O

“…We investigated the magnetic property of the powdered sample of 1 by temperature‐dependent magnetic susceptibility (χ M ) measurements under an applied magnetic field of 1000 G between 10‐300 K. From the plot of χ M vs T depicting the Zero Field Cooled‐Field Cooled (ZFC‐FC) curves, the χ M values were found to increaseon lowering the temperature with the curves showing minimum bifurcation suggestive of magnetic ordering. The effective magnetic moment was 4.017 BM calculated using μ eff =2.82(χ M T) 1/2 , which was slightly higher compared to the calculated spin‐only magnetic moment (μ so =3.873 BM) for high spin Co(II) 3d 7 system withS=3/2 due to spin‐orbit coupling(Figure 8a) [16,18,39] . Moreover, χ M T vs T presented a continuous decrease of χ M T values upon cooling to 10 K (Figure 8b).…”

“…A fitting of the Curie-Weiss law on the data gave Curie Constant (C) = 1.803 cm 3 mol À 1 K obtained from inverse of the slope and a negative Weiss constant (φ) = À 30.163 K, suggesting weak antiferromagnetic (AF) exchange interactions, evinced from declining χ M T values upon cooling with an effective magnetic moment of 3.8 BM using μ eff = (8 C) 1/2 . [1,3,18,21,22,[26][27][28][29]32,33]…”

“…Hence, it was quite an efficient approach keeping in mind these parameters to get the desired product as already reported in our previous work on synthesizing Co(II)phenylenediacrylates, succinates and nitro-isophthalates appended by N-donor ligands. [18,39,40] Structure Determination of 1 Compound1 crystallized in the monoclinic P2 1 /n space group (Table 1). The asymmetric unit is built from one independent Co(II) ion, two bpm ligands, two suc 2À ligands and two crystallization water molecules (Figure 1).…”

“…[19][20][21] These pre-requisites along with solvothermal reaction conditions foster the transmission of electronic interactions between the metals bridged by these ligands. [18,[22][23][24][25] There has been a great deal of work committed to the first-row transition metals (Fe, Co, Ni, Zn) bridged by bpm, the M⋅⋅⋅M separation is usually greater than 5.5 Å making it favourable for AF exchange interactions. [1,2,18,22,23,[26][27][28][29][30][31] With the surge in employing solid propellants for use in space and military operations, the propellants comprise the oxidizer (perchlorates or nitrates) and polymeric fuels.…”

“…Succinic acid portrays a range of conformational possibilities owing to the torsional flexibility of the carbon chain and the C−O bonds [17] . Lately, we have explored the rich structural diversity of Co(II) succinate coordination polymers appended by pyrazine wherein succinate adopted monodentate as well as bis‐monodentate coordination modes to Co(II) [18] . Bpm is known to behave as a terminal bidentate ligand bonding with a transition metal in cis ‐fashion or as a bis‐bidentate bridging ligand connecting two metal ions, depending upon the M: bpm molar ratios [19–21] .…”