Terarylenes as Photoactivatable Hydride Donors.

Terarylene frameworks containing benzothiazole as a photoprecursor of hydride donors are presented. We here report on two new scaffolds along with their photoreactivity in solution. Through use of selected external oxidants, the photogeneration of hydride donors is monitored using UV-visible, NMR, and TEM methods. As a proof-of-concept, photogeneration of hydride in the presence of Ag+ gave rise to the formation of Ag nanoparticles.

Inversion of Optical Activity in the Synthesis of Mercury Sulfide Nanoparticles: Role of Ligand Coordination.

Optical activity in inorganic colloidal materials was controlled through interactions of chiral molecules with the nanoparticle (NP) surface. An inversion of optical activity in the synthesis of mercury sulfide (HgS) NPs was demonstrated with an intrinsically chiral crystalline system in the presence of an identical chiral capping ligand. A continuous decrease in the positive first Cotton effect and an eventual reversal of CD profile were observed upon heating the aqueous solution of HgS NPs capped with N-acetyl-l-cysteine (Ac-l-Cys) at 80 °C. Ac-l-Cys afforded two bidentate coordination configurations with an almost mirror image of each other using the thiolate and either of carboxylate or acetyl-carbonyl groups on the HgS core. Experiment and calculation suggest that a shift in the distribution of the NP formation with energy in response to the combinations of ligand coordination structure and chiral crystalline surface is responsible for the inversion of optical activity.

The effect of surface ligands on the optical activity of mercury sulfide nanoparticles.

Mercury sulfide (HgS) nanoparticles (NPs) were prepared in the presence of water-soluble thiols as capping ligands in aqueous solutions. Chiral thiol ligands successfully afforded the formation of the chiral cinnabar phase (α-HgS), leading to optically active NPs, while two achiral thiols preserved ß-HgS NPs with an achiral crystalline system. The profiles of UV-vis absorption and circular dichroism (CD) spectra of chiral NPs were dependent on the chemical structures of the chiral ligands. Cysteine-based derivatives gave HgS NPs demonstrating almost mirror image CD profiles even though they possess identical stereochemistry. The water soluble chiral ligands on the NPs were replaced with an achiral ligand, 1-dodecanethiol, by the spontaneous phase transfer method. The ligand-exchanged NPs with the achiral thiol preserved the optical activity with a feature of the CD profile similar to that of the original NPs in water, demonstrating the chiral memory effect in the NP-core. The dissymmetry factor in optical absorption decreased by almost half, which could be attributed to the amorphous phase formed by the chemical etching with an excess amount of dodecanethiol. The optical activity showed a higher thermal stability compared to that of NPs before the ligand-exchange.