ABSTRACT
The main goal of this study is to provide systematic elucidation of the parameters that influence S â T intersystem crossing (ISC). Particular attention is paid to: (i) the computation of Snâ Tm spin-orbit coupling strength based on a non-adiabatic approach, (ii) crucial factors that facilitate ISC, such as the atomic number, ligand structure, and particularly the types of electronic transition, (iii) formulating a discussion on the standpoints of the fundamental photophysical theory. Combining the theoretical and empirical approaches, we then make semi-quantitative assessment of the ISC rate for certain representative transition metal (TM) complexes, the results of which allow us to develop a set of empirical rules that harness ISC for organometallics analogous to El-Sayed's rule for the classic organic compounds. We therefore present a critical and timely theoretical approach with the results matching quantitatively the experimental data, which serves as a prototype to access the photophysics of TM complexes in a facile and precise manner beneficial to researchers in the field of optoelectronics.
ABSTRACT
A tetradentate bis(pyridylpyrazolate) chelate, L, is assembled by connecting two bidentate 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole chelates at the 6 position of the pyridyl fragment with a phenylamido appendage. This chelate was then utilized in the synthesis of three osmium(II) complexes, namely, [Os(L)(CO)2] (4), [Os(L)(PPh2Me)2] (5), and [Os(L)(PPhMe2)2] (6). Single-crystal X-ray structural analyses were executed on 4 and 5 to reveal the bonding arrangement of the L chelate. Phosphine-substituted derivatives 5 and 6 are highly emissive in both solution and the solid state, and their photophysical properties were measured and discussed on the basis of computational approaches. For application, fabrication and analysis of organic light-emitting diodes (OLEDs) were also carried out. The OLEDs using 5 and 6 as dopants exhibit saturated red emission with maximum external quantum efficiencies of 9.8% and 9.4%, respectively, which are higher than that of the device using [Ir(piq)3] as a red-emitting reference sample. Moreover, for documentation, 5 and 6 also achieve a maximum brightness of 19540 cd·m(-2) at 800 mA·cm(-2) (11.6 V) and 12900 cd·m(-2) at 500 mA·cm(-2) (10.5 V), respectively.
