Understanding the gelation properties of the fluorophenyl glycosides of arabinoside gelators: experimental and theoretical studies

In supramolecular gelation, fluorinated gelators are important due to the unique properties displayed by these compounds that arise out of the presence of fluorine atoms. Generally, incorporation of fluorine leads to higher mechanical strength of the gels compared to their non-fluorinated counterparts and this property is enhanced with increasing the number of fluorine atoms. Herein, we show that the incorporation of fluorine into the phenyl ring of phenyl arabinoside allows the molecule to act as a gelator, unlike the non-fluorinated compound. We also show that the mechanical strength and stiffness of the gels is not only dependent on the positions of the fluorine atoms but also guided by their number. Detailed experimental studies, supported by computational studies, allowed us to rationalize the observed supramolecular interactions and propose reasons based on the conformational preferences of these compounds that allow additional hydrogen bonds and π-π interactions which guide the self-assembly, in addition to the primary H-bonding interactions. This, in turn, affects the mechanical behavior of these gels.

Synthesis, Experimental and Theoretical Study of Azidochromones

A series of 2-(haloalkyl)-3-azidomethyl and 6-azido chromones has been synthetized, characterized and studied by theoretical (DFT calculations) and spectroscopic methods (UV-Vis, NMR). The crystal structure of 3-azidomethyl-2-difluoromethyl chromone, determined by X-ray diffraction methods, shows a planar framework due to extended π-bond delocalization. Its molecular packing is stabilized by F···H, N···H and O···H hydrogen bonds, π···π stacking and C–O···π intermolecular interactions. Moreover, AIM, NCI and Hirshfeld analysis evidenced that azido moiety has a significant role in the stabilization of crystal packing through weak intermolecular interactions, where analysis of electronic density suggested closed-shell (CS) interatomic interactions.

A new ZnII metallocryptand with unprecedented diflexure helix induced by V-shaped diimidazole building blocks

Taking advantage of V-shaped ligands, a Zn^II metallocryptand, namely {[Zn₂(didp)₂(m-bdc)₂]}_n, (1) [didp = 2,8-di(1H-imidazol-1-yl)-dibenzothiophene and m-H₂bdc = isophthalic acid], has been hydrothermally synthesized. Single-crystal X-ray diffraction analysis reveals a 26-membered butterfly-type metallomacrocycle [Zn₂(didp)₂]. One m-bdc^2- ligand bridges [Zn₂(didp)₂] units to form a laterally non-symmetric [Zn₂(didp)₂(m-bdc)] metallocryptand with an exo-exo conformation. Another crystallographically independent m-bdc^2- functions as a secondary synthon to bridge discrete metallocryptands into a 1D zigzag chain architecture. Undoubtedly, the choice of two matched ligands in this work is crucial for metallocryptand construction and structure expansion. Interestingly, a rare helical chain with two flexures in one single L and/or R strand is observed. Another important feature is the C-O...π interactions, by which the dimensionality extension of (1) can be induced. Fluorescence measurements and density functional theory (DFT) calculations illustrate that the emission of (1) can probably be attributed to ligand-to-ligand charge transfer (LLCT).

Hydrogen bonding interactions in fluorinated 1,2,3-triazole derivatives

Comprehensive theoretical, structural and spectroscopic investigations on new substituted 1,2,3-triazoles in the solid state.

One-pot synthesis, quantum chemical calculations and X-ray diffraction studies of thiazolyl-coumarin hybrid compounds

Two closely related hybrid species containing both, thiazolyl and coumarin groups, were synthesized by using two different one-pot procedures from a common precursor. The reaction of α-bromoacetylcoumarin with thioacetamide in methanol furnished 3‑(2‑methylthiazol‑4‑yl)‑2H‑chromen‑2‑one (2), whereas refluxing α‑bromoacetylcoumarin with potassium thiocyanate in ethanol afforded 3‑(2‑ethoxythiazol‑4‑yl)‑2H‑chromen‑2‑one (3). Both derivatives were fully characterized by spectroscopic methods, elemental analysis and X-ray diffraction studies. Intramolecular C4H⋯N and C5'H⋯OC hydrogen bonds between the heterocycles determine the conformational behavior. The co-planarity of the coumarin and thiazolyl rings favors the occurrence of two remote orbital interactions involving the oxygen and nitrogen lone pairs and the corresponding σ*CH electron acceptor, as demonstrated by Natural Bond Orbital population analysis. The 2-substitution of the thiazol‑4‑yl group has little effect on the molecular structures but causes significant differences in the crystal packing of the two compounds.