Platinum complexes, phosphorescent emission

Keywords Emission quantum yields High-resolution spectroscopy Iridium complexes OLED emitters Organometallic compounds Phosphorescence Photophysics Platinum complexes Radiative rates Spin-orbit coupling Triplet emitters Zero-field splitting SOC ZFS SOC and geometry SOC paths... 

The strong environment dependence of the photophysical properties of platinum complexes allows their application as sensors. A phosphorescent Pt-Pt complex, shown in Fig. 12, can undergo a photoinduced Pt-Pt distance shortening. This leads to the formation of two distinct excited states and dual emission in the steady state. This photoinduced molecular structure change has a strong dependence on the molecule s... 

For this particular complex, the only emission observed at room temperature was residual fluorescence emanating from the BODIPY fragment and at low temperature, the presence of the platinum center induces intersystem crossing and phosphorescence from the BODIPY was indeed observed at 1.6 eV. 

These approaches have been adopted more recently to incorporate phosphorescent chromophores into PF in order to make use of the fact that a large proportion (up to 75%) of all excitons formed in LEDs are triplet states, whose energy can only be harvested by using phosphorescent units. The first fluorene copolymers with phosphorescent units 34-35 were made by Holmes and coworkers who added monobrominated red- or green-emitting iridium complexes to an AA-BB Suzuki polycondensation [57]. With short fluorene chains, only emission from the iridium complexes are observed, but with longer fluorene chains some blue emission is also seen. Other groups have since incorporated different phosphorescent units such as platinum [58] or zinc salen [59] units or porphyrins [60,61 ]. 

Owing to the heavy-atom effect of osmium, the complex is only phosphorescent and this emission occurs even at r.t. Palladium and platinum porphyrins also display an IL phosphorescence under ambient conditions [3,4,126,184,189], e.g.,... 

The bis-cyclometaUated complex Pt(N -thpy>2 28 (thpyH = 2-thien-2-ylpyri-dine), reported by von Zelewsky in the mid-1980s [44], was one of the first clear-cut examples of a simple platinum(ll) complex that phosphoresces in fluid solution at room temperature (2 ,ax = 578 nm, x = 2.2 ns in a PrCN/MeCN mixture) [45]. Barigelletti et al. showed, by means of a study of the temperature dependence of emission, that the influence of cyclometallation is to displace the d-d state to about 3,700 cm above the emissive state, ensuring that thermally-activated non-radiative decay is blocked off [46]. Although not thermally stable and hence not suitable for vacuum deposition methods of OLED fabrication, this complex and the trimethylsilyl derivative 29 has been incorporated into devices by spin-casting with TPD as a host material, and an EL efficiency of 11.5% has been achieved with 29 [47,48]. 

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