Solubility and Polymorphism of a HOF Monomer N1,N3,N5-Tris(pyridin-4-yl)benzene-1,3,5-tricarboxamide in 12 Neat Solvents at Temperatures from 283.15 to 323.15 K

Abstract

A gravimetric method is adopted to measure the solid–liquid equilibrium of N1,N3,N5-tris(pyridin-4-yl)benzene-1,3,5-tricarboxamide (TPBTC), a hydrogen-bonded organic framework (HOF) monomer in different solvents (methanol, dichloromethane, isopropanol, n-hexane, acetone, ethanol, 2-butanone, n-butanol, acetonitrile, water, ethyl acetate, and n-propanol). The experiment is carried out at atmospheric pressure, and the experimental temperatures range from 283.15 to 323.15 K. The powder X-ray diffraction analysis was performed on the equilibrium solid-phase characterization of TPBTC in different solvents, and the solid form of solute in equilibrium with different solvents was a mixture of three kinds of crystalline forms and an amorphous form. In the 12 monosolvents, the solubility increased with absolute temperature, and the following order was obtained: 2-butanone > isopropanol > n-propanol > n-butanol > ethyl acetate > acetonitrile > methanol > ethanol > dichloromethane > n-hexane > acetone > water. In the studied temperature range, the maximum and minimum values were recorded for 2-butanone (0.6753 × 10–3 mol/mol at 323.15 K) and water (0.004650 × 10–3 mol/mol at 283.15 K), respectively. The solubility behavior and solvent effects in various solvents were first investigated by the hydrogen bond acceptor tendencies as the main factor then interpreted by solvent polarity, cohesive energy density, and steric effect for some exceptions. In addition, the solid–liquid equilibrium data of TPBTC were correlated with the Yaws model and the Apelblat model. Furthermore, the two thermodynamic models were evaluated using the Akaike Information Criterion and Akaike weights. It can be observed that the Yaws model was more appropriate than the Apelblat model.