Supramolecular control of unidirectional rotary motion in a sterically overcrowded photoswitchable receptor

The control of molecular motion by external stimuli has attracted major interest in recent years. In order to achieve unidirectional rotational motion, intrinsically chiral light-driven molecular motors have been shown to be particularly versatile. We recently introduced a system in which unidirectional rotation is achieved in an achiral photoswitchable receptor upon binding of a chiral guest molecule. In order to gain detailed insight into the rotary steps, we present here a modified design in which the steric crowding is increased such that interconversion between the helical isomers of the (Z)-form of the receptor becomes very slow. DFT calculations support the increase in interconversion barrier. Furthermore, two diastereomeric complexes of the chiral guest bound to the (Z)-receptor are distinguished in the 1H NMR spectrum and the ratio between them slowly changes over time as a result of thermal helix inversion. On the other hand, no enrichment in one of the diastereomeric complexes is observed in the photochemical step. Our studies therefore unequivocally confirm that net rotation, induced by the chiral guest, takes place. This study affords an improved understanding of these dynamic supramolecular systems and expands the possibilities to control chirality transfer and motion at the molecular level, spurring developments of supramolecular recognition and information transfer at the nanoscale.Supramolecular & Biomaterials Chemistr

Controlled Diffusion of Photoswitchable Receptors by Binding Anti-electrostatic Hydrogen-Bonded Phosphate Oligomers

Dihydrogen phosphate anions are found to spontaneously associate into anti-electrostatic oligomers via hydrogen bonding interactions at millimolar concentrations in DMSO. Diffusion NMR measurements supported formation of these oligomers, which can be bound by photoswitchable anion receptors to form large bridged assemblies of approximately three times the volume of the unbound receptor. Photoisomerization of the oligomer-bound receptor causes a decrease in diffusion coefficient of up to 16%, corresponding to a 70% increase in effective volume. This new approach to external control of diffusion opens prospects in controlling molecular transport using light

Designing dynamic functional molecular systems

The design and construction of dynamic functional molecular systems, which mimic some of the properties of living systems, pose a huge contemporary challenge. Recent developments in supramo-lecular self-assembly, molecular switches, motors and machines, and chemical reaction networks, offer an excellent basis for integrating dynamic properties in molecular systems. In this perspective, we discuss different approaches towards dynamic functional molecular systems covering areas such as translated motion, dissipative self-assembly, self-regulation and biohybrid systems. The selected examples illustrate the level of control and complexity that can be achieved at present in this rapidly growing and exciting field of research. (C) 2017 Published by Elsevier Ltd.</p

Scopolamine Administration Modulates Muscarinic, Nicotinic and NMDA Receptor Systems

Studies on the effect of scopolamine on memory are abundant but so far only regulation of the muscarinic receptor (M1) has been reported. We hypothesized that levels of other cholinergic brain receptors as the nicotinic receptors and the N-methyl-D-aspartate (NMDA) receptor, known to be involved in memory formation, would be modified by scopolamine administration

Controlled Diffusion of Photoswitchable Receptors by Binding Antielectrostatic Phosphate Oligomers

Dihydrogen phosphate anions are found to spontaneously associate into anti-electrostatic oligomers via hydrogen bonding interactions at millimolar concentrations in DMSO. Diffusion NMR measurements supported formation of these oligomers, which can be bound by photoswitchable anion receptors to form large bridged assemblies of approximately three times the volume of the unbound receptor. Photoisomerization of the oligomer-bound receptor causes a decrease in diffusion coefficient of up to 16%, corresponding to a 70% increase in effective volume. This new approach to external control of diffusion opens prospects in controlling molecular transport

Photoswitchable bis(amidopyrroles): modulating anion transport activity independent of binding affinity

Supramolecular & Biomaterials Chemistr

Dynamic control of function by light-driven molecular motors

The field of dynamic functional molecular systems has progressed enormously over the past few decades. By coupling the mechanical properties of molecular switches and motors to chemical and biological processes, exceptional control of function has been attained. Overcrowded alkene-based light-driven molecular motors are very attractive in this respect owing to their unique multistate photochemically and thermally induced switching processes and their helical chirality inversion in each switching step. However, extending our control over properties from the molecular scale to larger length scales is still a fundamental challenge. In this Perspective, we discuss recent developments that address this challenge, ranging from the application of these motors in catalysis and synthetic materials to the control of biological properties. We may now be positioned at the dawn of a new era in which artificial molecular motors are able to perform programmed tasks and dynamic functions akin to the biological machines that are found in daily life