Evolution of the hydrogen-bonding motif in the melamine–cyanuric acid co-crystal: a topological study

Abstract

The melamine (M)/cyanuric acid (CA) supramolecular system is perhaps one of the most exploited in the field of self-assembly because of the high complementarity of the components. However, it is necessary to investigate further the factors involved in the assembly process. In this study, we analyzed a set of 13 M n /CA m clusters (with n , m = 1, 2, 3), taken from crystallographic data, to characterize the nature of the hydrogen bonds involved in the self-assembly of these components as well as to provide greater understanding of the phenomenon. The calculations were performed at the B3LYP/6-311++G(d,p) and ω-B97XD (single point) levels of theory, and the interactions were analyzed within the framework of the quantum theory of atoms in molecules and by means of molecular electrostatic potential maps. Our results show that the stablest structure is the rosette-type motif and the aggregation mechanism is governed by a combination of cooperative and anticooperative effects. Our topological results explain the polymorphism in the self-assembly of coadsorbed monolayers of M and CA. Graphical abstract The aggregation steps of the melamine-cyanuric co-crystal is driven by a hydrogen-bonded network which is governed by a complex combination of cooperative and anticooperative effects.

X-ray Fiber Diffraction and Computational Analyses of Stacked Hexads in Supramolecular Polymers: Insight into Self-Assembly in Water by Prospective Prebiotic Nucleobases

“…In particular, the two unmodified faces of these molecules enable the formation of assemblies named “rosette”, “linear tape”, and “crinkled tape” (Figure ). ,,− The two tape assemblies remain unbounded in one dimension and therefore are potentially of infinite length, making them attractive for extended assemblies. ,, The hexad rosette structure, on the other hand, being restricted to six monomers in a specific planar arrangement, is attractive for the rational design of supramolecular assemblies. − ,− After decades of research on these pairing systems, the only reported crystal structure for stacked hexameric rosettes containing one of these triamino species paired with a triketo species is of two stacked MA–BA hexads with bulky substituents attached to each heterocycle. It is likely that the bulky substituents prevent extended stacking of hexads and cause the observed deformation of the hexad planar geometry …”

“…1,2,4−16 The two tape assemblies remain unbounded in one dimension and therefore are potentially of infinite length, making them attractive for extended assemblies. 6,9,16 The hexad rosette structure, on the other hand, being restricted to six monomers in a specific planar arrangement, 17 is attractive for the rational design of supramolecular assemblies. 14−16,18−21 After decades of research on these pairing systems, the only reported crystal structure for stacked hexameric rosettes containing one of these triamino species paired with a triketo species is of two stacked MA−BA hexads with bulky substituents attached to each heterocycle.…”

Insights into the Early Stages of Melamine Cyanurate Nucleation from Aqueous Solution

“…The M-CA system is a classical example of molecular self-assembly governed by strong hydrogen bonding and soft π–π interactions (aromatic stacking). The results of the density functional theory (DFT) studies ,− confirm that high stability of the macroscale M-CA crystals is a result of the large number of intermolecular hydrogen bonds formed between M and CA (Figure ), among which N–H···N bonds are almost two times stronger than N–H···O . The most energetically favorable structures are rosette-like patterns, linear tapes, and their combinations .…”

“…The results of the density functional theory (DFT) studies 2,15−18 confirm that high stability of the macroscale M-CA crystals is a result of the large number of intermolecular hydrogen bonds formed between M and CA (Figure 1), among which N−H•••N bonds are almost two times stronger than N−H•••O. 15 The most energetically favorable structures are rosette-like patterns, linear tapes, and their combinations. 19 In general, it is believed that precursors of M-CA nucleismall soluble molecular complexes resemble the same motifs of structural organization.…”

Impact of confinement in multimolecular inclusion compounds of melamine and cyanuric acid

“…Nevertheless, when H is negative the hydrogen bonds are stronger than those with positive values. 34,47,48 The ellipticity , that measures the extent of the electron density within a plane containing the line path. In addition, it is a direct measure of the stability of a given bond, because it takes infinite large values preceding the coalescence of a ring critical point and a BCP.…”