Greenish-yellow-, yellow- and orange-light-emitting iridium(III) polypyridyl complexes with poly(eta-caprolactone)-bipyridine macroligands

A set of novel greenish-yellow-, yellow-, and orange-light-emitting polymeric iridium(III) complexes were synthesized with the bridge-splitting method. The respective dimeric precursor complexes, [Ir(ppy)2--Cl]2 (ppy = 2-phenylpyridine) and [Ir(ppyCHO)2--Cl]2 [ppyCHO = 4-(2-pyridyl)benzaldehyde], were coordinated to 2,2-bipyridine carrying poly(-caprolactone) tails. The resulting emissive polymers were characterized with one-dimensional (1H) and two-dimensional (1H1H correlation spectroscopy) nuclear magnetic resonance and infrared spectroscopy, gel permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and the successful coordination of the iridium(III) centers to the 2,2-bipyridine macroligand was revealed. The thermal behavior was studied with differential scanning calorimetry and correlated with atomic force microscopy. Furthermore, the quantitative coordination was verified by both the photophysical and electrochemical properties of the mononuclear iridium(III) compounds. The photoluminescence spectra showed strong emissions at 535 and 570 nm. The color shifts depended on the substituents of the cyclometallating ligands. Cyclic voltammetry gave oxidation potentials of 1.23 V and 1.46 V. Upon the excitation of the films at 365 nm, yellow light was observed, and this could allow potential applications in light-emitting devices. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2765-2776, 2005