Synthesis of phenanthroline derivatives by Sonogashira reaction and the use of their ruthenium complexes as optical sensors

The phenanthroline derivatives, which have alkynyl groups, were synthesized by palladium-catalyzed, Sonogashira cross-coupling reaction to provide the following coupled products: 4,7-bis(4-phenylethynyl-phenyl)-[1,10]phenanthroline (6a) and 4,7-bis{4-(4-hydroxy-buty-1-ynyl)-phenyl)-[1,10]phenanthroline (6b) at 87 and 89% yield, respectively. Their ruthenium complexes, tris{4,7-bis(4-phenylethynyl-phenyl)-[1,10]phenanthroline} ruthenium(II) bis(hexafluorophosphate) (7a) and tris[4,7-bis{4-(4-hydroxy-buty-1-ynyl)-phenyl)-[1, 10]phenanthroline}ruthenium(II)bis(hexafluoro-phosphate) (7b), were synthesized under mild conditions. The former showed relative fluorescence intensity changes between fully oxygenated and fully deoxygenated atmospheres, while the latter showed a linear fluorescence intensity response between pH 6 and 13.