Hydrogen-bonded host-guest systems are stable in ionic liquids.

We show that H-bonded host-guest systems associate in ionic liquids (ILs), pure salts with melting point below room temperature, in which dipole-dipole electrostatic interactions should be negligible in comparison with dipole-charge interactions. Binding constants (K) obtained from titrations of four H-bonded host-guest systems in two organic solvents and two ionic liquids yield smaller yet comparable K values in ionic liquids than in organic solvents. We also detect the association event using force spectroscopy, which confirms that the binding is not solely due to (de)solvation processes.

Measuring the Stability of Supramolecular Complexes in the Proximity of Single-Walled Carbon Nanotubes.

The decoration of SWNTs with supramolecular motifs is a common strategy for their subsequent noncovalent functionalization. However, due to the lack of a standard methodology, there are no quantitative measurements showing the extent to which the supramolecular equilibria are affected by one of the host-guest couple being anchored to the SWNT. Here, we use a method we initially developed to quantify association of small organic molecules to the walls of SWNTs to compare association constants of two host-guest systems, a Hamilton receptor-cyanuric acid derivative and a crown ether-ammonium couple, in solution and when the host is covalently attached to the SWNTs.

Measuring the Stability of Supramolecular Complexes in the Proximity of Single-Walled Carbon Nanotubes.

10.1002/open.202000018.

Dynamics of individual molecular shuttles under mechanical force.

Molecular shuttles are the basis of some of the most advanced synthetic molecular machines. In these devices a macrocycle threaded onto a linear component shuttles between different portions of the thread in response to external stimuli. Here, we use optical tweezers to measure the mechanics and dynamics of individual molecular shuttles in aqueous conditions.

Mechanical measurement of hydrogen bonded host-guest systems under non-equilibrium, near-physiological conditions.

Decades after the birth of supramolecular chemistry, there are many techniques to measure noncovalent interactions, such as hydrogen bonding, under equilibrium conditions. As ensembles of molecules rapidly lose coherence, we cannot extrapolate bulk data to single-molecule events under non-equilibrium conditions, more relevant to the dynamics of biological systems. We present a new method that exploits the high force resolution of optical tweezers to measure at the single molecule level the mechanical strength of a hydrogen bonded host-guest pair out of equilibrium and under near-physiological conditions.

Divergent reactivity of homologue ortho-allenylbenzaldehydes controlled by the tether length: chromone versus chromene formation.

The divergent behavior of two homologue allenals, namely, 2-(buta-2,3-dienyloxy)- and 2-(propa-1,2-dienyloxy)benzaldehydes, as cyclization substrates is described. 2-(Buta-2,3-dienyloxy)benzaldehydes suffers a formal allenic carbocyclization reaction to afford chromenes, whereas 2-(propa-1,2-dienyloxy)benzaldehydes react to yield chromones. The formation of chromenes is strictly a formal hydroarylation process divided into two parts, namely, allenic Claisen-type rearrangement and oxycyclization.

Spinal block complications in obstetrics and gynecology patients.

Objective: To determine spinal complications during and after surgery in obstetrics and gynecological patients.

Methods: We conducted a descriptive study in Al-Wahda and Aden Teaching Hospitals in Aden, Yemen from March 2004 to March 2005. One hundred and fifty obstetrics and gynecological patients were enrolled.