Five Multidimensional Co(II)-Complexes (Zero-Dimensional to Three-Dimensional) Derived from an Asymmetric 5-(Pyridin-3-yl)-1H-pyrazole-3-carboxylic Acid: Syntheses, Structures, and Magnetic Properties

Abstract

On the basis of an asymmetric, conjugated, partially or wholly deprotonated 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylic acid (H 2 ppc),, and [Co(Hppc) 2 (mbbbm)] 2 (5) [mbbbm = 1,3-bis(benzimidazole-1-ylmethyl)benzene)] have been synthesized and characterized magnetically and structurally. Polymer 1, which has the Schlafi symbol (4 2 •6 2 •8 2 ) 2 (4 2 •6•8 3 ) 2 , is a three-dimensional (3D) network. Polymer 2 includes a mononuclear subunit and an infinite two-dimensional (2D) framework subunit, while polymer 3 is a 2D sheet structure. Polymer 4 is characterized by a one-dimensional double ladder-like chain structure. Complex 5 possesses a binuclear structure. Magnetization data for 1 with the Co 2 units show the antiferromagnetic coupling in the Co 2 units. No long-range magnetic ordering is observed for 1. 2, 3, and 5 display weak antiferromagnetic exchange interactions. For 4 with the similar Co 2 units, it also exhibits antiferromagnetic coupling in the Co 2 units, and the M(H) curve is consistent with the antiferromagnetic nature in the Co 2 units. Variable temperature magnetic studies reveal that 2, 3, and 5 display weak antiferromagnetic interactions. The observed magnetization values, which were ∼2.5 Nβ at high field for 2, 3, and 5, are in accordance with the value anticipated for single uncompensated S = 1/2 spin.

Annular Tautomerism of 3(5)-Disubstituted-1H-pyrazoles with Ester and Amide Groups

“…Pyrazole is a five-membered aromatic heterocycle with two adjacent nitrogen atoms, classified as azole. Pyrazole derivatives have broad application, from engineering and polymers [1,2,3,4,5,6,7,8], to biological activity [9]; thus, new synthetic strategies are constantly developed [10,11,12,13,14,15,16,17]. Among them, there are 1 H -pyrazoles with substituents at positions 3 and 5, which reveal interesting applications [18,19,20,21,22,23,24,25], and some of them are depicted in Figure 1.…”

High Proton Conduction in Two Highly Water-Stable Lanthanide Coordination Polymers from a Triazole Multicarboxylate Ligand

“…Furthermore, note that there are a great number of disordered lattice water molecules which have been deleted in 1 and 2 . After the elimination of the crystalline H 2 O units in 1 , it became microporous, with a total potential solvent-accessible volume of 32.3% calculated by PLATON; as for 2 , it was 31.1%. , We are inclined to think that these uncoordinated −COOH groups and coordinated and lattice water molecules, which form many hydrogen bonds and some H-bonded networks, can offer some effective proton transmission pathways. Compared to those of 1 [Er1–O14:2.294(2) Å, Er1–O13:2.310(2) Å, and Er1–O15:2.371(3) Å], the bond lengths of 2 between the metal cation and coordinated water molecules [Yb1–O11:2.274(4) Å, Yb1–O13:2.301(5) Å, and Yb1–O12:2.345(4) Å] are shorter (Table S1).…”

“…After the elimination of the crystalline H 2 O units in 1, it became microporous, with a total potential solvent-accessible volume of 32.3% calculated by PLATON; as for 2, it was 31.1%. 54,55 We are inclined to think that these uncoordinated −COOH groups and coordinated and lattice water molecules, which form many hydrogen bonds and some H-bonded networks, can offer some S1). As the cation radius decreases from Er(III) to Yb(III) (lanthanide contraction effect), Table 1 shows the decreases in the lengths of a, b, and c axes [for 1, the a, b, and c axes are 12.5355(5), 13.1189(5), and 13.8723(6) Å; for 2, the a, b, and c axes are 12.5015(5), 13.0846(6), and 13.8499( 7) Å] and in the unit cell volumes [1903.6(1) Å 3 for 1 and 1893.57(2) Å 3 for 2].…”

Two N,N′-bis(pyridin-4-yl)pyridine-2,6-dicarboxamide coordination compounds

“…The heterocyclic nitrogen-derivative ligands have -electrondonating ability and can form strong M-N covalent bonds with transition-metal ions. This bonding feature, when combined with the flexibility and length of molecular backbone within these ligands, can lead to the construction of porous coordination compounds (Gao et al, 2003;Hagrman et al, 1999;Li et al, 2017). A variety of heterocyclic nitrogenderivative complexes with interesting properties and topologies have been synthesized using ligands such as 4,4 0 -bipyridine (Fujita et al, 1994), an asymmetric triazole dicarboxylate ligand (Hao et al, 2018), 5-(pyridine-3-yl)pyrazole-3-carboxylic acid (Cheng et al, 2016), 2-[4-(1H-imidazole-1-ylmethyl)-1H-1,2,3-triazol-1-yl] acetic acid (Yu et al, 2016) and 2,2 0 -dihydroxy-[1,1 0 ]binaphthalenyl-3,3 0 -dicarboxylate (Zheng et al, 2004).…”