Hydrogen-bonded urea-anion host lattices. Part 2. Crystal structures of inclusion compounds of urea with tetraalkylammonium bicarbonates

Multi-Component Crystals Containing Urea: Mechanochemical Synthesis and Characterization by 35Cl Solid-State NMR Spectroscopy and DFT Calculations

Mechanochemical synthesis provides new pathways for the rational design of multi-component crystals (MCCs) involving anionic or cationic components, which offer molecular-level architectures unavailable to MCCs comprised of strictly neutral components....

Conformational and Tautomeric Control by Supramolecular Approach in Ureido-N-iso-propyl,N'-4-(3-pyridin-2-one)pyrimidine

Ureido-N-iso-propyl,N’-4-(3-pyridin-2-one)pyrimidine (1) and its 2-methoxy pyridine derivative (1Me) has been designed and prepared. The conformational equilibrium in urea moiety and tautomerism in the pyrimidine part have been investigated by variable temperature and ¹H NMR titrations as well as DFT quantum chemical calculations. The studied compounds readily associate by triple hydrogen bonding with 2-aminonaphthyridine (A) and/or 2,6-bis(acetylamino)pyridine (B). In 1, the proton is forced to 1,3-tautomeric shift upon stimuli and keeps it position, even when one of the partners in the complex was replaced by another molecule. The observed tautomerism controlled by conformational state (kinetic trapping effect) opens new possibilities in molecular sensing that are based on the fact that reverse reaction is not preferred.

An Intermediate for the Clean Synthesis of Ionic Liquids: Isolation and Crystal Structure of 1,3-Dimethylimidazolium Hydrogen Carbonate Monohydrate

1,3-Dimethylimidazolium-2-carboxylate and carbonic acid have been used to prepare a 1,3-dimethylimidazolium hydrogen carbonate salt by means of a Krapcho reaction. The ability to form hydrogen carbonate azolium salts allows for them to be used as precursors for fast, efficient, environmentally benign, and halide-free syntheses of many ionic liquids by a simple, acid-base reaction of virtually any acid (inorganic, organic, and organic noncarboxylic) with a pK(a) less than that of HCO(3) (-). Additionally, the kinetics of this reaction can be accelerated by employing catalytic amounts of DMSO (a traditional Krapcho solvent used in decarboxylation reactions) to catalyze the decarboxylation. The crystal structure of 1,3-dimethylimidazolium hydrogen carbonate monohydrate is the first example of an imidazolium-based hydrogen carbonate salt. There is a strong 2D hydrogen-bonded network with facially pi-stacked imidazolium cations located in the cavities created by this framework.