| Abstract
| - The UV and emission spectra of a novel amphiphilic Pt complex containing 2,6-bis(1-octadecylbenzimidazol-2-yl)pyridine (L18), [Pt(L18)Cl](PF6), have been examined in order to obtain information about the molecular arrangement of the square-planar Pt complex both in solution and in cast and Langmuir−Blodgett (LB) films. The metal−metal dσ* to ligand π* charge transfer (MMLCT) emission at 650 nm acts as a luminescent probe for the Pt−Pt interaction. A cast film showed the MMLCT emission; however, the MMLCT band intensity was greatly suppressed in LB mono- and multilayer films. Instead, the emission at 600 nm arising from the ligand−ligand π−π interacted excited state became dominant.
- A novel amphiphilic Pt complex containing 2,6-bis(1-octadecylbenzimidazol-2-yl)pyridine (L18), [Pt(L18)Cl](PF6), has been synthesized. The complex exhibits concentration-dependent absorption and emission spectra insolution. With increasing the concentration of the Pt complex, we observed a new absorption band centered at550 nm derived from a metal−metal dσ* to ligand π* charge transfer (MMLCT) transition and the correspondingbroad emission centered at 650 nm. The Pt complex is surface-active, and the surface pressure−area isothermreveals three phase transitions. The three phases correspond to one liquid-expanding phase and two solid-condensedphases, respectively, with different intermolecular overlap in the “flat-on” orientation at the air−water interface.Without additives such as fatty acids, the complex forms a stable and reproducible Langmuir−Blodgett (LB)multilayer film above a surface pressure of 15 mN m-1. Strong emission from the LB films, even monolayer,was observed. Comparing the relative emission intensity of the MMLCT band for transferred LB monolayer filmwith that for cast films, we concluded that Pt−Pt interactions are suppressed in the LB film. Instead, the emissionat 600 nm arising from the ligand−ligand π−π interacted excited state became dominant. The results wouldprovide the insight into the control of molecular ordering for planar Pt complexes from the viewpoint ofcharacteristic excited states.
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