Structure-Photoluminescence Quenching Relationships of Iridium(III)-Tris(phenylpyridine) Complexes (Eur. J. Inorg. Chem. 7/2012)

The cover picture shows two “gladiator” compounds illustrating the Structure‐Photoluminescence Quenching Relationship (SPQR) observed in hemicaged Ir(III)–tris(2‐phenylpyridine) complexes bearing a capping unit (“gshield”), either on the pyridine or on the phenyl side. The presence of a capping unit on the pyridine side induces a dramatic 40 % decrease in oxygen quenching of the luminescence with respect to the uncapped complex, as a consequence of the shielding of the LUMO; conversely, shielding of the phenyl rings, where the HOMO is partially localized, does not induce any change in the degree of oxygen quenching. The Roman Empire initialism SPQR and the “hemicaged” laurel further symbolize this study, with the emperor's thumps up and down indicating the winning and losing gladiator, respectively. Details of the synthesis and the structural, photophysical, theoretical, and electrochemical characterization are discussed in the article by L. De Cola, A. H. Velders et al. on p. 1025 ff.