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The use of tris(4-aminophenyl)amine (TAPA) as central to the synthesis of both polyimines and polyimides and covalent organic frameworks and inorganic cages, among others, has grown in the last few years. The resulting materials exhibit high performance in their area of application. In this contribution, the crystal structures of two TAPA derivatives, triethyl (nitrilotris(benzene-4,1-diyl))tricarbamate (1) and triethyl 2,2′,2″-((nitrilotris(benzene-4,1-diyl))tris(azanediyl))tris(2-oxoacetate) (2), are described. The molecular and supramolecular structures of both compounds were compared between them and with analogous compounds. The analyses of their vibrational and 13C-CPMAS NMR spectroscopies, as well as their thermal stability, were included and corelated with the crystal structure. Hirshfeld surface analysis on the crystal structures of both TAPA derivatives revealed the stabilization of the crystal network via the amide N—H∙∙∙O interactions of dispersive nature in the carbamate, whereas dispersive carbonyl–carbonyl interactions also played a competitive role in the supramolecular arrangement of the oxamate. Interaction energy DFT calculations performed at the B3LYP/6-31G(d,p) level allowed us to estimate the energy contributions and nature of several interactions in terms of the stability of both crystal lattices. [ABSTRACT FROM AUTHOR]

Oxalamic acid derivatives are model molecules used in crystal engineering and molecular recognition both in solution and in the solid state. Despite their growing importance, hardly any information on polymorphism, stability and interrelations of their solid forms can be found in the literature. In this work, the molecular and supramolecular structures of three cocrystal solvates of formula H2pOx·2S (S = DMSO, DMF, ⅓(MeOH·2W); W = H2O) and the dimethylammonium salt of N,N′-(1,4-phenylene)dioxalamic acid (H2pOx) are described. The nature and energetics of non-covalent interactions were explored through computational methods including the evaluation of the Hirshfeld surface, two-dimensional fingerprint plots, energy-framework diagrams and crystal lattice energies. The X-ray structural parameters were correlated with experimental solid state IR, 13C-CPMAS, thermal analysis and SEM to elucidate the unknown molecular and supramolecular structures of two hydromorphs and three desolvated polymorphs of H2pOx. The role of the crystallized solvents was demonstrated to fix the conformation of H2pOx through hydrogen bonding and n/π → π* interactions, favoring the sp–ap conformation to fit the shape of the solvent. The interconversion pathways between the ten solid phases of H2pOx were stablished, relying on the crystal size and temperature to yield a specific solvent-free polymorph. [ABSTRACT FROM AUTHOR]