Synthesis, structure and magnetic properties of a cobalt(II) mesoxalate 1D coordination polymer

Abstract

Mesoxalate ligand (H2mesox)2−, the conjugate base of the mesoxalic acid (2,2’‐dihydroxyl‐malonic acid) reacts with cobalt (II) ions to form the 1‐D coordination polymer {[Co(H2mesox)(H2O)2] ⋅ H2O}n. This compound displays a structure based on homochiral polymeric chains which stack together in an AABB fashion through hydrogen bonding by both coordination and crystallisation water molecules. Although the magnetic properties for such a Co(II) compound are difficult to interpret in the whole temperature range, at low temperatures the Co(II) behaves as an S=1/2 effective spin and equation derived by Fisher from the Ising model was applied to analyse the data in the 4–40 K range. The magnetic interactions in this compound are compared with the magnetic interactions displayed by similar compounds reported in the literature.

Improvement of the Proton Conduction of Copper(II)-Mesoxalate Metal–Organic Frameworks by Strategic Selection of the Counterions

“…The reaction of basic copper(II) carbonate with an aqueous solution of mesoxalic acid ( Scheme 1 a) at 30 °C yields acidic solutions (pH ∼ 2.0) containing the [Cu 3 (Hmesox) 3 ] 3– trinuclear species ( Scheme 1 b) in which the mesoxalic acid (H 4 mesox) has lost three of its four protons. 44 − 51 These trinuclear copper(II) units further react with copper(II) and chloride ions (arising from copper(II) chloride tetrahydrate) to form anionic two-dimensional networks with general formula [Cu 9 (Hmesox) 6 Cl(H 2 O) 6 ] n n– .…”

“…L C is completely deprotonated C 3 O 6 4– (mesox 4– ), which is the second time that it has been reported in the literature 55 for this ligand and the first time we have observed it within more than 20 compounds with mesoxalate that we have synthesized and results in a shorter C–O distance in this mesoxalate ( Figure 6 , Scheme 1 , Table S2 ). 44 − 48 , 50 , 51 , 53 , 54 …”

“…L C is completely deprotonated C 3 O 6 4− (mesox 4− ), which is the second time that it has been reported in the literature 55 for this ligand and the first time we have observed it within more than 20 compounds with mesoxalate that we have synthesized and results in a shorter C−O distance in this mesoxalate (Figure 6, Scheme 1, Table S2). [44][45][46][47][48]50,51,53,54 The L C mesoxalate ligand also acts as tridentate with respect to Cu4 and bidentate with respect to Cu5 and Cu5 vii with a μ 3 -(κO:κO′; κO″:κO″; κO″:κO‴; κO‴′:κO‴″) binding mode (Scheme 2 and Figure 6a,b). This bridging mode has been found in mesoxalate compounds in which the trinuclear copper(II) entities connect to lanthanoid(III) atoms, but has not been yet observed for transition metal(II) ions connecting to the trinuclear copper(II)-mesoxalate unit.…”

“…Our research group has previously reported that the mesoxalate ligand is a good candidate for obtaining functional materials. − We have found that it can build one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) anionic paramagnetic networks, which can host water molecules and protonated organic bases in the pores, resulting in magnetic and proton-conducting materials. − …”