Spectroscopic and Electrochemical Behavior of Cyclometalated Pd(II) Complexes

✍ Scribed by Mauro Maestri; Diana Sandrini; Vincenzo Balzani; Alex von Zelewsky; Philippe Jolliet

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: German
• Weight: 356 KB
• Volume: 71
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19880710117

✦ Synopsis

The absorption and emission spectra, emission lifetimes, luminescence quantum yields, and electrochemical behavior of the complexes Pd(Phpy),, Pd(Thpy),, and Pd(bhq), (Phpy-, Thpy-, and bhq-are the deprotonated forms of 2-phenylpyridine, 2-(2-thienylfpyridine, and benzo[h]quinoline, respectively) have been studied, and the results obtained have been compared with those available for Pt(I1) and Pt(1V) complexes containing the same ligands. The intense ligand-centered absorption bands below 340 nm are strongly perturbed by metalation, and the absorption features in the 340-450-nm region are likely to include contributions from formally metal-to-ligand charge-transfer transitions. The structured luminescence spectra observed at 77 K (lifetimes are 0.48,0.28, and 2.6 ms for Pd(Phpy),, Pd(Thpy),, and Pd(bhq),, respectively) have been assigned to transitions having mainly ligand-centered character, with an increasing metal-to-ligand charge-transfer contribution in going from Pd(bhq), to Pd(Phpy), and to Pd(Thpy)*. The complexes Pd(phpy), and Pd(thpy), show two reversible one-electron reduction waves, whereas reduction of Pd(bhq), is irreversible, as is the oxidation of the three complexes.