Abstract
The molecular recognition process and the ability to form multicomponent supramolecular systems have been investigated for the amide of triphenylacetic acid and l-tyrosine (N-triphenylacetyl-l-tyrosine, TrCOTyr). The presence of several supramolecular synthons within the same amide molecule allows the formation of various multicomponent crystals, where TrCOTyr serves as a chiral host. Isostructural crystals of solvates with methanol and ethanol and a series of binary crystalline molecular complexes with selected organic diamines (1,5-naphthyridine, quinoxaline, 4,4′-bipyridyl, and DABCO) were obtained. The structures of the crystals were planned based on non-covalent interactions (O–H···N or N–H+···O− hydrogen bonds) present in a basic structural motif, which is a heterotrimeric building block consisting of two molecules of the host and one molecule of the guest. The complex of TrCOTyr with DABCO is an exception. The anionic dimers built off the TrCOTyr molecules form a supramolecular gutter, with trityl groups located on the edge and filled by DABCO cationic dimers. Whereas most of the racemic mixtures crystallize as racemic crystals or as conglomerates, the additional tests carried out for racemic N-triphenylacetyl-tyrosine (rac-TrCOTyr) showed that the compound crystallizes as a solid solution of enantiomers.
Highlights
Molecular recognition and formation of host-guest complexes are fundamentals of supramolecular chemistry [1,2,3,4]
The molecules of TrCOTyr used all available oxygen atoms for the intermolecular interaction, while the NH group is covered by the trityl group, which makes it inaccessible for intermolecular interaction in the crystal lattice
After three days in a microtube, colorless crystals apprMopornioatceryfsotraXls-orafysoalnvaltyesirsaac-pTprCeaOreTdy.r·MeOH and rac-TrCOTyr·MeOH were obtained according to the saMmoenporcorcyesdtaulrse. of solvates rac-TrCOTyr·MeOH and rac-TrCOTyr·MeOH were obtained accoCrdoicnrgystotatlhseofsa(TmreCOprToycre)d2·uNreP.HD were obtained by dissolving N-triphenylacetyl-l-tyrosine and 1,5-napChotcirysdtyanlseoifn(T2:r1CmOToylarr)2r·NatPioHiDn awcerteonoeb.taTinhedsoblyudtiiosnsowlvainsgalNlo-wtriepdhetonyelvaacpetoyrla-Lte-tsylroowsilnyeaanndd c1r,y5s-tnaalps hsutiirtyadbylenfeorinan2a:1lymsioslaaprpreaatiroedininactheetovnees.sTelhaeftseorluthtiroene dwaayss.allowed to evaporate slowly and crystCaolscsryusitaablsleofof rTarnCaOlyTsyisr·aQpXpewarerdeinobthtaeinvesdsebl yaftdeirstshorleveindgayNs.-triphenylacetyl-l-tyrosine and quinoxCaolicnreysinta2ls:1 omf oTlarrCrOatTioyri·nQaXcewtoenree
Summary
Molecular recognition and formation of host-guest complexes are fundamentals of supramolecular chemistry [1,2,3,4]. The formation of pre-defined solid-state architectures from smaller, molecular building blocks containing the supramolecular synthons in the molecular structure is the main goal of crystal engineering [5]. The supramolecular synthons were defined by Desiraju as “structural units within supermolecules that can be formed and/or assembled by known or conceivable synthetic operations involving intermolecular interactions” [6]. The proper identification of supramolecular synthons within a given molecular system, their capabilities, and limitations is an important step to understand how the molecules interact and which type(s) of aggregates they may form. The common supramolecular synthons are the carboxylic group and secondary amide functionalities, the latter is responsible e.g., for secondary structure of the proteins [7,8]
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