Guest control of a hydrogen bond-catalysed molecular rotor.

Herein, the control of a molecular rotor using hydrogen bonding guests is demonstrated. With a properly positioned phenol substituent, the N-arylimide rotors can form an intramolecular hydrogen bond that catalyses the rotational isomerization process. The addition of the guests disrupts the hydrogen bond and raises the rotational barrier, slowing the rotation by two orders of magnitude.

Guest-accelerated molecular rotor.

A molecular rotor was designed in which the rate of rotation is accelerated by guest complexation. The binding of an acetate guest to the urea groups lowers the barrier of the adjacent C(aryl)-N(imide) bond by 2 to 4 kcal/mol. This behavior is in contrast to most molecular rotors in which guest complexation slows rotation.

Molecular playdough: conformationally programmable molecular receptors based on restricted rotation.

A new method for rapidly tailoring molecular properties is presented in which the three-dimensional shape of a malleable framework is controlled by heating with a template molecule.

A small molecule diacid with long-term chiral memory.

A small, axially chiral diacid was designed with chiral memory based on restricted rotation. Heating a racemic sample with a chiral alkaloid led to an enantiomeric excess of up to 40% ee. The guest-induced chirality was preserved on cooling to rt, which was maintained even in the absence of guest (t(1/2) = 14y).

Origins of selectivity in a colorimetric charge-transfer sensor for diols.

Bispyridyl hydrogen bonding receptor 1 forms colored charge transfer (CT) complexes with complementary phenols and naphthols. Despite its low association constants of approximately 10(1) M(-1), receptor 1 was highly selective forming CT complexes of varying color and intensity with different diol guests. The selectivity of 1 was correlated with the ability of its CT band to simultaneously yield information about the association constant and the electronic structure of the phenols and naphthols.