MS31-P10 Supramolecular synthons: structural features in various crystalline environmentThe key concepts of crystalline engineering are intermolecular interactions and the supramolecular synthons which are formed by such interactions. The so-called “Synthon approach” greatly helps to simplify the understanding and description of crystal structures.
In this work, the structural features of a number of known and new supramolecular synthons in a different crystalline environment are studied. By the structural features we mean the geometric parameters of strong "synthon-forming" non-covalent interactions, the conformation of the synthon and the possibility of its additional stabilization through secondary intermolecular interactions, which may turn out to be different in different crystalline forms. Thus, the influence of the crystal environment on the structure and stability of the synthons that are classic for supramolecular chemistry: carboxyl, amide, thioamide, sulfonamide, and some others, in different polymorphic forms and in “racemate-conglomerate” pairs has been studied. To obtain data on the behavior of synthons in different environments, key series of compounds has been studied for polymorphism and for a tendency to spontaneous resolution of enantiomers.
An extremely rare type of polymorphism "conglomerate 1-conglomerate 2" has been discovered . In both polymorphs, the main formative motif is a homochiral chain (helix) based on the same supramolecular α-hydroxyamide open-chain synthon that takes different symmetry depending on the crystal system.
For the classical carboxylic acid synthon, the ability to form a stable interaction of the "Lp...synton" type is found, which can cause a significant amplification of synthon-forming hydrogen bonds.
For the known thioamide synthon, the effect of a "chiral-dependent conformational memory" is found - a pairs of thiourea molecules "memorize" their mutual arrangement both in the hetero- and homochiral H-bound dimers and reproduce it in the structure of metal complexes corresponding to them by stereochemistry.
The possibility of transferring an amide open-chain supramolecular synthon, which is symmetrical relatively to the glide plane in the crystals of isonyazide dervatives, from the racemic medium into the homochiral one has been discovered . It was achieved by inclusion of a second independent molecule into a cell.
A new tetrameric cyclic sulfinamide synthon has been found, the formation of which is accompanied by the formation of an H-bound tetramer with a sofisticated stereochemical construction.
A new cyclic centrosymmetric β-hydroxysulfoxide synthon, capable of self-assembly in both the racemic and homochiral medium, has two stable conformations realized in the room temperature and low-temperature phases .
This work was financially supported by the Russian Science Foundation (grant No 17-13-01209).References:
 Lodochnikova, O.A., Zaripova, A.R., Fayzullin, R.R. et al (2018). CrystEngComm, DOI: 10.1039/C8CE00369.
 Lodochnikova, O.A., Dobrynin, A.B., Andreeva, O.V. et al (2014). CrystEngComm, 16, 6234-6243.
 Lodochnikova, O.A., Startseva, V.A., Nikitina, L.E. et al (2014). CrystEngComm, 16, 4314-4321.
Keywords: supramolecular synthon, polymorphism, intermolecular interactions