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

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 Ksv 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.