ILCT

IL excitation of Pt(l-naphthylamine)2Cl2 involves a shift of electron density from the Pt-N bond into the aromatic ring of the naphthyl moiety. Such an IL transition can thus be also viewed as an ILCT excitation [73]. Since the naphthylamine ligand looses its coordinating ability in the excited state the complex undergoes a photosubstitution of this ligand. 

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SC (3ct values indicates that the ILCT transitions coincide with the dipole moment axes in complexes such as (52) and (53).81... 

Although the metal electronic configuration exerts a profound influence on f3 in (128)-(130), the situation is rather different if the ligands bear strong electron donor/acceptor substituents. For example, in (131) and (132) the (3 responses are dominated by two ILCT excitations with the... 

Fig. 16 Schematic of the trends in excited-state energies in [Pt(4 -R-tpy)Cl]+ complexes, showing the mixing of the ILCT state for the amino-substituted complex. AE represents the barrier to deactivation via a3 d-d state. Reproduced from data in [65] with permission from Elsevier...

A key observation that supports the notion of ILCT character is the decreased susceptibility of these complexes to exciplex quenching. This normally occurs by attack of Lewis bases at the vacant coordination sites of the metal, and is promoted for MLCT excited states by the increased electrophilic-ity of the metal in the transient, formally oxidized + 3 state, in effect by the hole generated on the metal [85]. Contribution of ILCT character serves to delocalize the hole away from the metal and onto the ligand. 

Figure 2. A plot of aromatic reduction potential versus the energy of the ILCT transition for the (dppe)Pt S2C2(2-Het)(H) complexes ( ). The approximate energy of the d to d transition for the (dppe)Pt S2C2(2-Het)(H) complexes ( ).

Figure 3. Representative emission of a dual-emitting heterocyclic-substituted platinum 1,2-enedithiolate. The emission spectra of [(dppelPtjSiCitCHiCHi-iV -pyridiniumlJllBPfr,], in dimethyl sulfoxide (DMSO) at 298 K (no instrument correction applied) Solid line, emission spectrum under N2 (emission from both the ILCT and 3ILCT ) Dashed line, emission spectrum under air (emissions from the iLCT ).

There are heterocyclic-substituted platinum 1,2-enedithiolates that have ILCT emissions that are either enabled by protonation of the ground state or quenched by protonation of the excited states. Which process is operative is dependent on the heterocycle appended to the 1,2-enedithiolate, and hence the electron affinity of the accepting orbital in the ILCT transition (see Fig. 2). 

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