The excellent contrast ratio, visibility, and advantages in producing thin and light displays let organic light emitting diodes change the paradigm of the display industry. To improve future display technologies, higher electroluminescence efficiency is needed. Herein, the detailed study of the non-radiative decay mechanism employing density functional theory calculations is carried out and a simple, general strategy for the design of the ancillary ligand is formulated. It is shown that steric bulk properly directed towards the phenylisoquinoline ligands can significantly reduce the non-radiative decay rate.

Nickel-catalyzed [3 + 2] cycloaddition reactions of unsymmetrical alkynes and organic azides afford substituted 1,2,3-triazoles with high levels of chemo- and regioselectivity.

A pyridinium zwitterion substrate is employed with two different types of transition metal catalysts to develop a regiodivergent cycloaddition. The pyridinium zwitterion is a highly reactive dipolar substrate that can undergo a dipolar cycloaddition with various reactants. It has multiple reaction sites, and the chemoselectivity is determined by the electronic demand of the catalyst−substrate complex. The reaction with nucleophilic Pd reagents affords fused N-heterocyclic compounds via regioselective [4 + 2] cycloaddition. The origin of the site selectivity and the mechanism of this reaction are investigated in this combined experimental and computational study. We found that the pyridinium zwitterion plays a completely different role in the palladium(0)-catalyzed [4 + 2] cycloaddition reaction and in the rhodium(II)-catalyzed [5 + 3] cycloaddition, which was examined experimentally in a previous study. The frontier molecular orbitals of the pyridinium substrate and activated catalyst complex reveal that the pyridinium zwitterion can act as both a nucleophile and an electrophile depending on the reaction partner in a manner much more defined than that of conventional substrates, leading to the observed regiodivergent chemical reactivity.