The First Noncovalent-Bonded Supramolecular Frameworks of (Benzylthio)Acetic Acid with Proline Compounds, Isonicotinamide and Tryptamine.

The co-crystallization of (benzylthio)acetic acid (HBTA) with L-proline (L-PRO), D-proline (D-PRO), DL-proline (DL-PRO), isonicotinamide (INA) and tryptamine (TPA) led to the formation of five novel crystalline compounds: L-PRO ± ·HBTA ( 1 ), D-PRO ± ·HBTA ( 2 ), DL-PRO ± ·HBTA ( 3 ), INA·HBTA ( 4 ) and TPA + ·BTA - ( 5 ). The prepared supramolecular assemblies were characterized by single crystal X-ray diffraction, an elemental analysis, FT-IR spectroscopy and a thermal analysis based on thermogravimetry (TG) combined with differential scanning calorimetry (DSC). Additionally, their melting points through TG/DSC measurements were established. All fabricated adducts demonstrated the same stoichiometry, displayed as 1:1. The integration of HBTA with selected N-containing co-formers yielded different forms of multi-component crystalline phases: zwitterionic co-crystals ( 1 - 3 ), true co-crystal ( 4 ) or true salt ( 5 ). In the asymmetric units of 1 - 4 , the acidic ingredient is protonated, whereas the corresponding N-containing entities take either the zwitterionic form ( 1 - 3 ) or remain in the original neutral figure ( 4 ). The molecular structure of complex 5 is occupied by the real ionic forms of both components, namely the (benzylthio)acetate anion (BTA - ) and the tryptaminium cation (TPA + ). In crystals 1 - 5 , the respective molecular residues are permanently bound to each other via strong H-bonds provided by the following pairs of donor···acceptor: O carboxylic ···O carboxylate and N pyrrolidinium ···O carboxylate in 1 - 3 , O carboxylic ···N pyridine and N amine ···O carboxylic in 4 as well as N indole ···O carboxylate and N aminium ···O carboxylate in 5 . The crystal structures of conglomerates 1 - 5 are also stabilized by numerous weaker intermolecular contacts, including C-H···O ( 1 - 3 , 5 ), C-H···S ( 1 , 2 , 5 ), C-H···N ( 5 ), C-H···C ( 5 ), C-H···π ( 1 - 5 ) as well as π···π ( 4 ) interactions. The different courses of registered FT-IR spectral traces and thermal profiles for materials 1 - 5 in relation to their counterparts, gained for the pure molecular ingredients, also clearly confirm the formation of new crystalline phases.