How does the combination of the nitro group and fluorine atoms affect the (co)crystallization behaviour of arylenediamines?
A series of phenylenediamines containing the NO 2 group and 3 to 0 fluorine atoms and 18-crown-6 ether were used to study the dependence of the stoichiometry and supramolecular structure of co-crystals on the degree of fluorination of the aromatic co-former. 2,4-Diamino-3,5,6-trifluoro- and -3,5-dif...
Gespeichert in:
Veröffentlicht in: | CrystEngComm 2023-06, Vol.25 (22), p.3284-3298 |
---|---|
Hauptverfasser: | , , , , , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | A series of phenylenediamines containing the NO
2
group and 3 to 0 fluorine atoms and 18-crown-6 ether were used to study the dependence of the stoichiometry and supramolecular structure of co-crystals on the degree of fluorination of the aromatic co-former. 2,4-Diamino-3,5,6-trifluoro- and -3,5-difluoronitrobenzenes form co-crystals of two stoichiometries: 2 : 1 (preferably) and 1 : 1. 2,4-Diamino-5-fluoronitrobenzene and the non-fluorinated analogue yield only 1 : 1 co-crystals. DSC analysis indicates complete regeneration of the stoichiometry and structure of the co-crystals in the melting-crystallization cycle. According to X-ray diffraction data, all the 1 : 1 co-crystals are built from the 1D assemblies in which N-H O
cr
H-bond is the only structure-directing interaction. The 2 : 1 co-crystals have a 3D or 2D supramolecular structure due to additional interactions formed by the aromatic co-formers,
i.e.
N-H O
nitro
H-bond and p π electron contacts. Analysis of the structure of diaminonitrobenzene homocrystals showed that in di- and trifluorinated diaminonitrobenzenes, F atoms contribute to the formation of p π electron interactions, while in mono- and non-fluorinated co-formers, the ability of NH
2
groups to form the H-bonds both as donors and as acceptors increases. Factors controlling the crystallization behaviour were rationalized using quantum-chemical computations of the packing and co-crystallization enthalpies, the energies of N-H X (X = O
cr
, O
nitro
, N
amino
) and p π electron interactions, as well as the MEP and NCI analyses.
Fluorine substituents control the stoichiometry and supramolecular structure of co-crystals affecting the electron density distribution over the molecule and, thus, the strength of H-bonds and p π electron interactions. |
---|---|
ISSN: | 1466-8033 1466-8033 |
DOI: | 10.1039/d3ce00327b |