Coordination polymers from alkaline-earth nodes and pyrazine carboxylate linkers

Abstract

A new series of alkaline-earth-metal based coordination polymers were synthesized by using a pyrazine-2,5-dicarboxylic acid (2,5-H2pzdc) ligand under hydrothermal conditions. These compounds show a variety of structural topologies, reflecting the variable coordination geometries of the alkaline-earth ions as well as the key role of the metal precursor salts. Ca, Sr, and Ba give porous three-dimensional compounds, namely [Ca(2,5-pzdc)(H2O)2]·H2O (1), [Sr(2,5-pzdc)(H2O)4]·H2O (3), [Ba(2,5-pzdc)(H2O)4]·2H2O (4) and [Ba(2,5pzdc)(H2O)2] (5), that feature one-dimensional hydrophilic channels which are filled with water molecules. The Sr compound retains its structure when the lattice water molecules are removed, while the other compounds undergo a structural rearrangement. The hydrophilicity of the Sr compound combined with its high stability even in the absence of guest molecules are the key characteristics that determine its good water adsorption and proton conductivity properties.

Impressive Proton Conductivities of Two Highly Stable Metal–Organic Frameworks Constructed by Substituted Imidazoledicarboxylates

“…As illustrated in Table , the optimized conductivity of MOF 1 (1.24 × 10 –4 S·cm –1 under 98% RH and 100 °C) is only lower than the value of one N-heterocyclic carboxylate-based MOF, [Cd-5TIA] (5-TIA = 5-triazoleisophthalic acid), but close to that of three MOFs ,, and much higher than that of most reported Cd II -MOFs. − For 2 , the optimized conductivity of 0.92 × 10 –3 S·cm –1 at 98% RH and 100 °C is the largest value among the described Sr-MOFs. ,− …”

“…The reason may be that, with an increase of the humidity, the number of water molecules adsorbed by the frameworks also increases, leading to an increase in the proton carriers. In addition, these extra absorbed water molecules could constitute more useful hydrogen-bonding networks with O and N atoms of the organic ligands, which can benefit the transport of protons in the MOFs. − …”

Efficient modulation of a barium metal–organic framework using amino acids

“…Following on from the current authors' expertise and prior work on crystal engineering and overcoming synthesis challenges of main group metal compounds (Soleimannejad et al, 2014;Moghzi & Soleimannejad, 2018;Moghzi et al, 2020), we chose barium, a non-radioactive heavy member of the s-block, for this study. Barium(II) ions have a radius of 149 pm and are therefore very large Group 2 metal ions which, through their high affinity to oxygen atoms, exhibit a similar coordination behavior to that of the lanthanide ions (Foo et al, 2011(Foo et al, , 2013Asgharnejad et al, 2019;Tang et al, 2018;Liu et al, 2015;Sarazin & Carpentier, 2016).…”

Sonochemical synthesis of two nanoscale Co(II) coordination compounds: Facile fabrication of Co3O4 nanoparticles with various morphologies

“…Compound 1 and 2 are two different products resulting from the same metal ion and PT system but differing initial molar ratios. The acid used in the preparation of these compounds is 2,3-pyrazinedicarboxylic acid which has been employed widely due to its multiple coordination modes and the steric hindrance between the carboxylate groups which helps to increase the dimensionality of the assembled covalent networks with interesting properties [14,15].…”