Pt^II Phosphors with Click-Derived 1,2,3-Triazole-Containing Tridentate Chelates

A series of Pt^II complexes featuring 1,2,3-triazole-derived N^∧N^∧N-, N^∧C^∧N- and C^∧N^∧C-coordinating ligands were studied both experimentally and computationally aiming at the design of new Pt^II phosphors. By virtue of click chemistry, the new complexes were readily functionalized, e.g., with bulky groups in order to suppress aggregation of the complexes. For a N^∧C^∧N-type cyclometalated Pt^II complex, the high energy of the π* orbitals of the 1,2,3-triazole units gave rise to deep-blue phosphorescence; the poor luminescence quantum yield was attributed to an inadequate energy separation between the emissive state and the d–d states. However, when the 1,2,3-triazole donor moiety acted as a spectator/ancillary ligand only, an intense green emission could be achieved (Φ_PL = 0.57, τ = 4.6 μs)