Study of Conformational and Supramolecular Structural Stability of Propylene‐Bridged 2‐Pyridone Dimers

Abstract

In quest of the role of noncovalent interaction for the preference of inter and intramolecular stacking phenomenon, we synthesized O/O (1), N/O (2) and N/N (3) isomeric dimers of 3-cyano-4,6-dimethyl-2-pyridone linked through propylene chain. The direct evidence of noncovalent interactions and conformation of all the three isomers were obtained by single crystal X-ray diffraction analysis and conformational stability was evaluated through density functional theory. Isomers 1 and 2 were crystallized in stable conformation while isomer 3 was crystallized in constraint geometry which was further confirmed by differential scanning calorimetry analysis. The supramolecular structure in isomer 1 showed the helical geometry, isomer 2 showed the parallel stacking and pleated structure, while isomer 3 showed only pleated structure.

The development of a robust folded scaffold as a fluorescent material using butylidine-linked pyridazinone-based systems via aromatic π⋯π stacking interactions

“…18 In order to tune the properties of these dimers, it is essential to understand the nature and relative strength of the intramolecular interactions. 6,8 Two aromatic units present folded and unfolded conformations in solution, and the position of the folded-unfolded conformational equilibrium is a measure of the intramolecular ring-ring stacking interaction, as reported earlier. 19 Nevertheless, considerable examples of fluorescent pyridazinone and triazinone single crystals have been reported so far.…”

“…[4][5][6][7] But not every propylene-linked molecule is folded; accordingly, we have reported many unfolded compounds to date, indicating that the spacer does not play much of a role in the folding; instead, it is the nature of the molecule to become folded. [8][9][10] In pyridazinone and triazinone, folding may occur due to extended conjugation present in the system, from the main pyridazinone and triazinone moiety to the phenyl rings attached to it.…”

“…There have been a number of studies concerning the intramolecular stacking and conformational analysis of symmetrical or asymmetrical dimers with aromatic and heteroaromatic systems linked through different spacers. [4][5][6][7][8] In our previous work, we used the propylene/Leonard linker to study the intramolecular arene interaction in flexible two-parent compounds (I) and (II) (Chart S1, ESI †) by X-ray crystallography in the solid state and established that the pyridazinone and 1,2,4-triazinone cores can adopt a folded conformation stabilized by intramolecular p-p interactions linked via polymethylene spacers. 4 Lin Li and co-workers presented a squaraine core and four peripheries with electron donor-p-acceptor (D-p-A) characteristics, which promote the crystal framework stabilized by p-p interactions and H bonds.…”