Crystal structure of poly-[aqua-(μ₇-benzene-1,3,5-tricarboxylato)-(μ₃-1,2,4-triazol-1-ido)dicobalt(II)], C₁₁H₇Co₂N₃O₇

Source of material

A mixture of CoCl₂⋅2H₂O (0.1 mmol, 0.024 g), 1,2,4 triazole (Htrz) (13.9 mg, 0.2 mmol), and benzene-1,3,5-tricarboxylic acid (H₃btc) (21.0 mg, 0.1 mmol) was dissolved in 5 mL DMF and 2 mL EtOH. The mixture was then transferred into a 20 mL vial and heated to 80 °C, and hold for 60 h. Then the reactant mixture was cooled at a rate of 10 °C/min to lead to the formation of crystals in 36% yield based on Co(II) ion.

Experimental details

The H atoms bonded to C were positioned geometrically and refined using a riding model, with C—H = 0.93 Å with U_iso(H) = 1.2 times U_eq(C).

Discussion

There is a general interest in 1,2,4-triazoles [1].

Structural analysis suggests that there are three crystallographically independent Co(II) ions, one deprotonated trz⁻ ligand and one deprotonated btc³⁻ ligand in the asymmetric unit. Co1 (occupancy 1/2) is six-coordinated by four carboxylic O atoms from four different btc³⁻ ligands and two N atoms from two different trz⁻ ligands, forming a octahedral coordination; Co2 is five-connected with four carboxylic O atoms from four different btc³⁻ ligands and one N atom from one trz⁻ ligand; Co3 (occupancy 1/2) is six-coordinated again by two carboxylic O atoms from two different btc³⁻ ligands and two N atom from two different trz⁻ ligands, and the remaining sites are finished by two water molecules. The Co—O bond distances fall in the range of 2.052(2)–2.293(2) Å and the Co—N distances are in the range of 2.047(3)–2.068(3) Å. Cationic cobalt(II), anionic ligands and the neutral water ligands form a three-dimensional coordination polymer. The compactly packing of the whole framework results in its little solvent accessible void. From a topological point of view, each Co ion could be judged as a separate node, the trz ligand could be considered as a 3-connected node, the btc³⁻ ligand could be viewed as a 7-connected node, so the whole framework can be viewed as a 5-nodal (3,4,5,6,7)-connected net with Point symbol of {4.6²}2{4⁶.6¹4.8}2{4⁶.6⁴}2{4⁸.6⁷}{6⁵.8}.