Robustness of thioamide dimer synthon, carbon bonding and thioamide–thioamide stacking in ferrocene-based thiosemicarbazones

Abstract

The role of thioureas in crystal engineering as robust supramolecular synthons is now recognized, but their analogs, namely thiosemicarbazones/N-iminothioureas, have not received the attention they deserve.

Robustness of a thioamide {⋯H–N–CS}2 synthon: synthesis and the effect of substituents on the formation of layered to cage-like supramolecular networks in coumarin–thiosemicarbazone hybrids

“…These two features make this class of compounds more attractive than thioureas in crystal engineering. Very recently, we have highlighted these features using ferrocene-based thiosemicarbazones 53 and herein as a continuation of the previous work and our continuous research interests in the study of non-covalent interactions, [54][55][56][57] we report the synthesis of new structurally related coumarin-thiosemicarbazone hybrid molecules 3a-3c and using these molecules as a platform, demonstrate the robustness of the thioamide dimer {Á Á ÁH-N-CQS} 2 synthon of thiosemicarbazones. The purpose of introducing a freely rotatable coumarin moiety into these structures is to create a flexible environment for different possible non-covalent interactions.…”

Synthesis and fluorine-mediated interactions in methanol-encapsulated solid state self-assembly of an isatin-thiazoline hybrid

“…Keeping this in view, we very recently reported the synthesis and solid state self-assembly of 5-fluoroisatin-based hybrid molecule 1, where no intermolecular interactions were observed for fluoro substituent in the presence of N-H···O, C-H···O, C-H···N, C-H···π, π···π, C-H···Cl interactions [32]. This observation and our continuous interest in supramolecular self-assemblies [33][34][35][36][37][38][39] increased our curiosity and prompted us to introduce 4-fluoro group as a substitute to 3-methoxy on the central N-aryl ring of the rigid core of isatin-thiazoline hybrid 1 to explore the existence of fluorine-mediated interactions in isatin-based compounds. Pleasingly, the approach remained successful and herein, we report the synthesis and methanol-encapsulated layered assembly of isatin-thiazoline hybrid 2 …”

Intramolecular Noncovalent Carbon Bonding Interaction Stabilizes thecisConformation in Acylhydrazones

“…Importantly, the examination of existing protein structures reveals that with exception of proline all other natural amino acids mostly happen as the trans isomer ( >99.9 %) . However, the amide and thioamide moieties in semicarbazones and thiosemicarbazones, respectively mostly show cis conformation, due to the presence of intramolecular hydrogen bond (Scheme ). In view of this, it can be expected that replacement of NH‐moiety of semicarbazones with a CH 2 group would render trans ‐conformation of the amide moiety in acylhydrazones.…”

“…Since the lone pair (LP) of the sp 2 hybridized N atom is located along the vector of the C(sp 3 )–N bond (see Scheme ) and is thus suitable to interact with the antibonding C−N bond orbital (BD*), it can be anticipated that the presence of an intramolecular N⋅⋅⋅C noncovalent tetrel (carbon) bonding interaction should have its role in the appearance of preferred cis conformation, somewhat similar to the role of intramolecular hydrogen bonding in semicarbazones and thiosemicarbazones . However, to confirm whether the true N⋅⋅⋅C carbon bonding interaction in fact exists or not, we carried out a series of theoretical calculations.…”