Luminescent Langmuir−Blodgett Films of Platinum(II) Complex [Pt(L18)Cl](PF₆) (L18 = 2,6-Bis(1-octadecylbenzimidazol-2-yl)pyridine)

Abstract

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 in solution. With increasing the concentration of the Pt complex, we observed a new absorption band centered at 550 nm derived from a metal-metal d sigma* to ligand pi* charge transfer (MMLCT) transition and the corresponding broad emission centered at 650 nm. The Pt complex is surface-active, and the surface pressure-area isotherm reveals three phase transitions. The three phases correspond to one liquid-expanding phase and two solid-condensed phases, 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 film with that for cast films, we concluded that Pt-Pt interactions are suppressed in the LB film. Instead, the emission at 600 nm arising from the ligand-ligand pi-pi interacted excited state became dominant. The results would provide the insight into the control of molecular ordering for planar Pt complexes from the viewpoint of characteristic excited states.

Aggregation induced colour change for phosphorescent iridium(iii) complex-based anionic surfactants

“…One of the fundamental features of these class of compounds is their tendency to adsorb at interfaces (for instance air/water) and, upon certain conditions, spontaneously self-assemble into welldefined aggregates, such as micelles and vesicles. Some papers already reported on the great redox 4 and photophysical 5, 6 properties of transition metal complexes displaying self-organizing abilities through noncovalent intermolecular interactions. 2 The design of these novel materials is actually triggered by the powerful possibility of merging the peculiar physico-chemical properties carried by transition metal complexes, with the self-assembling ability of surfactant molecules.…”

A Platinium(II)‐Based Molecular Light Switch for Proteins

“…A broad, featureless absorption band at 420 nm has been assigned to a 1 MLCT [Pt(5d)-π*(bzimpy)] transition similar to [Pt(L18)Cl] + [L18 = 2,6-bis(1-octadecylbenzimidazol-2-yl)pyridine]. [10] Complex 1 exhibits a very broad and weak 3 MLCT emission centered at 625 nm in aqueous solution at room temperature upon excitation at 370 nm. The excited state lifetime of complex 1 is 0.19 µs in Tris buffer solution (pH 7.0) at 298 K. The excited state lifetime of complex 1 is less than that of other platinum() complexes such as PtPren and PtPrtmen, whose lifetimes are 4.2 and 3.6 µs, respectively.…”

Iridium and Rhodium Complexes within a Macroreticular Acidic Resin: A Heterogeneous Photocatalyst for Visible‐light Driven H2 Production without an Electron Mediator

“…This behavior originates from the poorly resolved vibronic structure and is analogous to that of Pt II polypyridyl complexes. [18] The tendency is different for Ir-Rh-resin 1, where phosphorescence emission of the powdered sample is blue-shifted relative to that of the free complex in acetonitrile at room temperature, with a maximum near 550 nm ( Figure 5). Furthermore, the shift toward shorter wavelength was small (~3 nm) upon switching from room temperature to 77 K (data not shown).…”