Spontaneous gelation of a novel histamine H4 receptor antagonist in aqueous solution.

Purpose: Low molecular weight hydrogelators typically require a stimulus such as heat, antisolvent, or pH adjustment to produce a gel. This study examines gelation of a novel histamine H4 receptor antagonist that forms hydrogels spontaneously at room temperature.

Methods: To elucidate the mechanism and structural moieties responsible for this unusual gelation, hydrogels were characterized by rheology, optical microscopy, and XRD.

Dipole tuning of charge transport in molecular junctions.

Molecules with different magnitude and direction of dipole moments are sandwiched between mercury (Hg) and p(+)-Si to form Hg-molecules-(p(+)) Si junctions. The importance of the dipole moment of molecules in controlling the symmetry of current-voltage curves is shown by carrying out charge transport measurements at these molecular junctions. Junction parameters are obtained by considering charge transport across the junction as a combination of tunneling and Schottky emission.

Controlling molecular crystal polymorphism with self-assembled monolayer templates.

The control of crystal polymorphism is a long-standing issue in solid-state chemistry, which has many practical implications for a variety of commercial applications. At least four different crystalline forms of 1,3-bis(m-nitrophenyl) urea (MNPU), a classic molecular crystal system, are known to crystallize from solution in various concomitant combinations. Herein we demonstrate that the introduction of gold-thiol self-assembled monolayers (SAMs) of substituted 4'-X-mercaptobiphenyls (X = H, I, and Br) into the crystallization solution can serve as an effective means to selectively template the nucleation and growth of alpha-, beta-, and gamma-MNPU phases, respectively.

Selective growth of a less stable polymorph of 2-iodo-4-nitroaniline on a self-assembled monolayer template.

Orthorhombic and triclinic crystals of 2-iodo-4-nitroaniline (INA) grow concomitantly from supersaturated ethanol solutions, but the less stable orthorhombic phase can be selectively grown on 3'-X-4-mercaptobiphenyl (X = NO(2), I) self-assembled monolayer templates.