THE SYNTHESIS, STRUCTURE AND PHOTOPHYSICAL PROPERTIES OF PHOSPHORESCENT CYCLOMETALATED N^N^C-COORDINATED PLATINUM COMPLEXES

Abstract

Phosphorescent materials based on cyclometalated platinum complexes have attracted a great deal of attention because of their potential in chemical, biological and optoelectronic applications, specifically as emitters in organic light-emitting diode devices. In addition, development of phosphorescent materials emitting in the deep red and/or near infrared region have become a popular area of focus because of their capabilities as chemosensors, in solar cells and bioimaging dyes. Several classes of phosphorescent cyclometalated platinum complexes based on tridentate and tetradentate ligands have already been developed by our lab. In this study, two series of cyclometalated N^N^C Pt(II) complexes 1a-6a and 1b-6b, were designed to emit throughout a wide range of the visible spectrum and were successfully synthesized bearing either a phenyl acetylide or phenyl ancillary ligand. The photophysical properties of complexes can be tuned as desired through methodical modifications of the cyclometalating or ancillary ligand with varying electron accepting or donating moieties. Photophysical studies were conducted on the synthesized complexes and found emission wavelengths ranging from 496-643 nm, quantum yield ([Phi]p) values between 43.0% and [less than] 0.1% and lifetimes ([tau]) as long as 13.1 [micro]s at 298 K. TD-DFT calculations of ground state HOMO and LUMO orbitals, as well as X-ray crystallographic analysis of select complexes were conducted and analyzed. The data comparison of the obtained results between the phenyl acetylide and phenyl coordinated complexes assists in identifying any structure-photophysical property relationships present, which will be discussed in detail.