Thiophene, a key building block for the construction
of conjugated
materials, has been scarcely studied in halogen bonding (XB)-driven
self-assemblies. In the present study, two thiophene derivatives modified
at position 3 were (co-)crystallized using complementary XB donor/acceptor
functional groups. Single-crystal X-ray diffraction analysis confirmed
the presence of halogen and chalcogen bonding acting, in most cases,
concomitantly. While the majority of the structures are governed by
the conventional N···I motif, additional S···N
and S···S contacts encouraged the cohesion of the supramolecular
architectures. Density functional theory calculations shed the light
on interaction energy, their respective contributions of the motifs
to these non-covalent bonds, and the overall stability of these assemblies.
To gain further insight into the formation and evidence of XB interactions,
solution and mechanochemical syntheses of polymorphic adducts were
performed, followed by 13C solid-state NMR analysis. Further, 1H and 19F{1H} solution-state NMR spectroscopy
studies were carried out to highlight these interactions in the solution
phase. The strength and directionality of halogen bonding thus reaffirm
its role as a structure-directing agent for designing functional materials.
The evidence of N···S chalcogen bonds in thiophene
derivatives also broadens up the horizon of supramolecular chemistry
in S-heterocycles, while necessitating further investigation for rational
application in materials science.
We report the first case of mechanochemical deracemization by using liquid‐assisted abrasive grinding. The target molecule is a precursor of Paclobutrazol, an important fungicide and plant growth inhibitor. Using mechanochemical deracemization, we are even able to transform a 10 % ee scalemic mixture of this latter in an enantioenriched product of 97 % ee in a couple of hours. This is substantially shorter compared to solution‐based deracemization methodologies. The present paper thus introduces an efficient and greener process to enantiopure material.
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