| The synthesis, structure, and photophysical properties of a series of novel, highly luminescent tridentate platinum complexes with general coordination geometry of (C.;N*N)-PtL are reported, where "C.;N" denotes a coordination ofC and N to the platinum to form a five-membered metallacycle and "N*N" denotes a coordination of two N atoms to the platinum to form a six-membered metallacycle; L is a mono anionic ligand such as halides or acetylides. Compared to the known (C.;N.;N)-PtL type of complexes that were reported to emit with low quantumyields, the structural modification leads to dramatic improvements in phosphorescence efficiency. For example, new complexes (C.;N*N)-PtL with L = hexylacetylideand phenylacetylide emitted intensely with quantum yields of 47% and 56%, respectively, latter of which is among the highest quantum yields reported so far for cyclometalated platinum (II) complexes.;Selectivity in C–H bond activation by platinum and the exact mechanism of cycloplatination are issues that still remain unclear. A series of ligands which include sp2/sp3, primary/secondary sp 3 C–H bonds, and aromatic/vinylic sp2 C–H bonds with a carbon linker between the bipyridine and the carbon groups have been prepared. All ligands have been attempted for cycloplatination in glacial acetic acid and acetonitrile. All ligands produced the same sp2 C–H bond activated complex in both solvents, which suggests that the linker atom does play a role on selectivity. |
