Persistent Room Temperature Phosphorescence from Triarylboranes: A Combined Experimental and Theoretical Study

Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate k_isc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions.     

First study of rhodium(I) complexes with chiral sulfur-containing terpenoids as catalytic systems for ketone hydrosilylation

Abstract

Using a “chiral pool” approach, a number of chiral thiolate and sulfide ligands based on natural terpenes and terpenoids have been synthesized in a few simple steps. Two new Rh-thiolate complexes with the formula [Rh(CO)₂(μ-SR)]₂ were obtained. The influence of these complexes and catalytic systems formed by combining the synthesized ligands with [Rh(CO)₂(μ-Cl)]₂ and [Rh(cod)(μ-Cl)]₂, on the reaction rate, chemoselectivity, stereoselectivity and formation of tetraphenyldisiloxane in Rh-catalyzed asymmetric hydrosilylation of acetophenone as a model reaction have been studied. Mechanistic aspects of formation of silyl enol ether as a side product in the presence of S-containing ligands are presented.     

The study of structure and dynamics of molecules: NMR spectra transformed by superfine coupling

In the present paper, the peculiarities of NMR phenomenon in paramagnetic systems are reported. Specifics of detection of high‐resolution NMR spectra transformed by superfine interaction are discussed. Concrete examples illustrate the modern possibilities of NMR application for the study of structure and dynamics of the molecular (multielectron) systems. Copyright © 2015 John Wiley & Sons, Ltd.