A systematic study of the photophysical processes in polydentate triphenylene-functionalized Eu3+, Tb3+, Nd3+, Yb3+, and Er3+ complexes

m-Terphenyl-based lanthanide complexes functionalized with a triphenylene a ntenna chromophore ((Ln)1) exhibit sensitized visible and near-infrared emi ssion upon photoexcitation of the triphenylene antenna at 310 nm, Luminesce nce lifetime measurements of the (Eu)1 and (Tb)1 complexes in methanol-h(1) and methanol-d(1) revealed that one methanol molecule is coordinated to th e lanthanide ion, indicating that all eight donor atoms provided by the lig and are involved in the encapsulation of the lanthanide ion. The luminescen ce lifetimes of the near-IR-emitting complexes (Er)1, (Nd)1, and (Yb)1 in D MSO-h(6) and DMSO-d(6) are in the microsecond range, and are dominated by n onradiative deactivation of the luminescent state. The processes preceding the lanthanide luminescence in the sensitization process have been studied in detail. The complexed lanthanide ion reduces the antenna fluorescence an d increases the intersystem crossing rate via an external heavy atom effect . The subsequent energy-transfer process was found to take place via the an tenna triplet state in all complexes. Luminescence quantum yield measuremen ts and transient absorption spectroscopy indicated that in solution two con formational isomers of the complexes exist: one in which no energy transfer takes place, and one in which the energy transfer does take place, resulti ng in the lanthanide luminescence. The intramolecular energy-transfer rate is higher in the (Eu)1 and (Tb)1 complexes than in the near-infrared-emitti ng complexes. In methanol the energy-transfer rate is 3.8 x 10(7) s(-1) for (Eu)1 and (Tb)1. In DMSO-d(6) the intramolecular energy-transfer rate is h igher in the (Nd)1 complex (1.3 x 10(7) s(-1)) than in the (Er)1 (3.8 x 10( 6) s(-1)) and (Yb)1 (4.9 x 10(6) s(-1)) complexes.