title: A luminescent Pt(II) complex with a terpyridine-like ligand involving a six-membered chelate ring.
abstract: The ligand 2-(8'-quinolinyl)-1,10-phenanthroline (1) was prepared in 79% yield by the Friedlander condensation of 8-amino-7-quinolinecarbaldehyde and 8-acetylquinoline. The complex [Pt(1)Cl]+ was prepared and compared with the isomeric 2-(2'-quinolinyl)-1,10-phenanthroline (2) complex. An X-ray analysis indicated that the six-membered chelate ring in the tridentate complex resulted in a relief of angle strain as well as some non-planarity in the bound ligand 1. The control system for photophysical studies is [Pt3Cl]+ where denotes 2-(2'-pyridyl)-1,10-phenanthroline. Relative to the complex of 3, in dichloromethane solution [Pt(1)Cl]+ exhibits noticeably higher energy charge-transfer absorption but slightly lower energy emission. The gap between the onset of absorption and emission is larger because the emission from [Pt(1)Cl]+ originates from a triplet excited state with substantial intra-ligand character. At room temperature in deoxygenated dichloromethane, [Pt(1)Cl]+ has an excited-state lifetime of 310 ns vs. 230 ns for [Pt(1)Cl]+. Within the series, [Pt(1)Cl]+ also exhibits the largest activation barrier for thermally induced quenching at 2730 cm(-1) in fluid dichloromethane solution. However, the barrier is only about 50% larger than that found for [Pt(1)Cl]+. There is reduced ring strain in [Pt(1)Cl]+, but inter-ligand steric interactions weaken the ligand field.
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana, 47907-2084, USA.
authors.forename: Yi-Zhen
authors.initials: YZ
authors.lastname: Hu
authors.forename: Michael H
authors.initials: MH
authors.lastname: Wilson
authors.forename: Ruifa
authors.initials: R
authors.lastname: Zong
authors.forename: Celine
authors.initials: C
authors.lastname: Bonnefous
authors.forename: David R
authors.initials: DR
authors.lastname: McMillin
authors.forename: Randolph P
authors.initials: RP
authors.lastname: Thummel
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D008024:Ligands; D049449:Luminescence; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D008024:Ligands; D009944:Organoplatinum Compounds; D011725:Pyridines