Synthesis and Photophysical Properties of 3,8‐Disubstituted 1,10‐Phenanthrolines and Their Ruthenium(II) Complexes

Abstract

Abstract The palladium‐catalysed cross‐coupling reaction between 3,8‐dibromo‐1,10‐phenanthroline with phenylacetylene or 3,5‐bis(trifluoromethyl)phenylboronic acid gives good yields of the 3,8‐disubstituted products. These 1,10‐phenanthroline derivatives are used for the formation of novel ruthenium complexes of the type [(tbbpy) 2 Ru(phenR 2 )] 2+ [where tbbpy = 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine, phen = 1,10‐phenanthroline, R represents the substituents at the 3,8 positions with bromine, phenylacetylene or 3,5‐bis(trifluoromethyl)phenyl]. All compounds are completely characterised by NMR and UV/Vis spectroscopy, MS, electrochemical measurements and Raman and resonance Raman spectroscopy. The photophysical properties indicate a strong influence of the substitution of the phenanthroline ligand on the absorption, emission and Raman properties. With resonance Raman spectroscopy the localisation of the singlet metal‐to‐ligand charge‐transfer ( 1 MLCT) excited state is determined. Thesolid‐state structures of 3,8‐dibromo‐1,10‐phenanthroline (phenBr 2 ) and the corresponding ruthenium complex [(tbbpy) 2 Ru(phenBr 2 )] 2+ and a structural motif of [(tbbpy) 2 Ru{phen‐3,8‐bis[3,5‐bis(trifluoromethyl)phenyl]}] 2+ are also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)