title: Structural, photophysical, and electrophosphorescent properties of platinum(II) complexes supported by tetradentate N2O2 chelates.
abstract: We present an examination of the structural and photophysical characteristics of [Pt(N(2)O(2))] complexes bearing bis(phenoxy)diimine auxiliaries (diimine=4,7-Ph(2)phen (1) and 4,4'-tBu(2)bpy (2)) that are tetradentate relatives of the quinolinolato (q) ligand. These neutral derivatives display high thermal stability (>400 degrees C in N(2)). While the crystal lattice in 1 consists of (head-to-tail)-interacting dimers, molecules of 2 are arranged into infinitely stacked planar sheets with possible pi-pi interactions but no close Pt.Pt contacts. Complexes 1 and 2 exhibit moderately intense low-energy UV/Vis absorptions around lambda=400-500 nm that undergo negative solvatochromic shifts. Both derivatives are highly luminescent in solution at 298 K with emission lifetimes in the micros range, and mixed (3)[l-->pi*(diimine)] (l=lone pair/phenoxide) and (3)[Pt(d)-->pi*(diimine)] charge-transfer states are tentatively assigned. The excited-state properties of 2 are also investigated by time-resolved absorption spectroscopy and by quenching experiments with pyridinium acceptors to estimate the excited-state redox potential. These emitters have been employed as electrophosphorescent dopants in multilayer OLEDs. Differences between the brightness, color, and overall performance of devices incorporating 1 and 2 are attributed to the influence of the diimine substituents.
authors.affiliation: Department of Chemistry, HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
authors.forename: Yong-Yue
authors.initials: YY
authors.lastname: Lin
authors.forename: Siu-Chung
authors.initials: SC
authors.lastname: Chan
authors.forename: Michael C W
authors.initials: MC
authors.lastname: Chan
authors.forename: Yuan-Jun
authors.initials: YJ
authors.lastname: Hou
authors.forename: Nianyong
authors.initials: N
authors.lastname: Zhu
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang