Metal-Organic Frameworks of Cobalt(II) with 4,7-Di(1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole and Aromatic Dicarboxylic Acids: Synthesis, Crystal Structures, and Magnetic Properties

Abstract

The reactions of cobalt(II) nitrate with 4,7-di(1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole (Tr₂btd) and aromatic dicarboxylic acids (terephthalic (H₂bdc), 2,6-naphthalenedicarboxylic (2,6-H₂ndc), and 2,5‑furandicarboxylic (2,5-H₂fdc) acids) afford metal-organic frameworks [Co(Tr₂btd)(bdc)]_n (I) and {[Co₂(Tr₂btd)(DMF)(2,6-ndc)₂]·DMF}_n (II) with the layered structures and chain metal-organic framework [Co(Tr₂btd)₂(H₂O)(2,5-fdc)]_n (III). Compounds I and III are paramagnetic in a temperature range of 1.77–300 K without exchange interactions between the Co²⁺ cations, and compound II exhibits the antiferromagnetic interaction between the Co²⁺ cations in the binuclear building blocks with the exchange interaction constant J ≈ −100 K. Single crystals of the phase of compound IIIa with the identical composition but different structure are found when taking samples for X-ray diffraction (XRD) analysis. The molecular structures of metal-organic frameworks I, II, III, and IIIa are determined by XRD (CIF files CCDC nos. 2343141 (I), 2343297 (II), 2343296 (III), and 2343140 (IIIa)).