Co-crystallization of a versatile building block 4-amino- 3,5-bis(4-pyridyl)-1,2,4-triazole with R-isophthalic acids (R = –H, –NH2, –SO3H, and –COOH): polymorphism and substituent effect on structural diversity

Abstract

Co-crystallization of a versatile building module 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole (4-bpt) with isophthalic acid (H₂ip) and its 5-substituted derivatives R–H₂ip (R = –NH₂, –SO₃H, and –CO₂H) affords a series of supramolecular solids 1–5. All compounds have been characterized by IR, microanalysis, and powder X-ray diffraction, and their thermal stability has been investigated by TG-DTA technique. Single crystal X-ray diffraction reveals that compounds 1 and 2 with the formula [(H₂ip)·(4-bpt)] exhibit polymorphism, which can be isolated via a similar synthetic procedure without or with the metal ion as structure-directing reagent, and display distinct hydrogen-bonding assemblies of 3-D and double-layer networks, respectively. Multifarious 3-D supramolecular architectures are observed for compounds [(NH₂–H₂ip)·(4-bpt)] (3), [(SO₃–H₂ip)⁻·(H-4-bpt)⁺]·2H₂O (4), and [(CO₂H–H₂ip)·(4-bpt)]·2H₂O (5), in which the substituent groups of isophthalic acid are involved in different hydrogen-bonding interactions. The results clearly display the substituent effect on the structural assembly of organic co-crystals, which will be significant in the rational design and construction of such crystalline materials with specific hydrogen-bonding networks.