title: Luminescence in phosphine-stabilized copper chalcogenide cluster molecules--a comparative study.
abstract: The electronic properties of a series of eight copper chalcogenide clusters including [Cu12S6(dpppt)4] (dpppt = Ph2P(CH2)5PPh2), [Cu12Se6(dppo)4] (dppo = Ph2P(CH2)8PPh2), [Cu12S6(dppf)4] (dppf = Ph2PCpFeCpPPh2), [Cu12S6(PPh2Et)8], [Cu12S6(PEt3)8], [Cu24S12(PEt2Ph)12], [Cu20S10(PPh3)8], and [Cu20S10(P(t)Bu3)8] were investigated by absorption and photoluminescence (PL) spectroscopy as well as time-dependent density functional theory calculations. Major features of the experimental electronic absorption spectra are generally well-reproduced by the spectra simulated from the calculated singlet transitions. Visualization of the nonrelaxed difference densities indicates that for all compounds transitions at higher energies (above ∼2.5 eV, i.e., below ∼495 nm) predominantly involve excitations of electrons from orbitals of the cluster core to ligand orbitals. Conversely, the natures of the lower-energy transitions are found to be highly sensitive to the specifics of the ligand surface. Bright red PL (centered at ∼650-700 nm) in the solid state at ambient temperature is found for complexes with all 'Cu12S6' (E = S, Se) cores as well as the dimeric 'Cu24S12', although in [Cu12S6(dppf)4], the PL appears to be efficiently quenched by the ferrocenyl groups. Of the two isomeric 'Cu20S10' complexes the prolate cluster [Cu20S10(PPh3)8] shows a broad emission that is centered at ∼820 nm, whereas the oblate cluster [Cu20S10(P(t)Bu3)8] displays a relatively weak orange emission at ∼575 nm. The emission of all complexes decays on the time scale of a few microseconds at ambient temperature. A very high photostability is quantitatively estimated for the representative complex [Cu12S6(dpppt)4] under anaerobic conditions.
authors.affiliation: Lehn Institute of Functional Materials, Sun Yat-Sen University , Guangzhou 510275, China.|Karlsruhe Nano Micro Facility (KNMF) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Eichhöfer
authors.forename: Gernot
authors.initials: G
authors.lastname: Buth
authors.forename: Sergei
authors.initials: S
authors.lastname: Lebedkin
authors.forename: Michael
authors.initials: M
authors.lastname: Kühn
authors.forename: Florian
authors.initials: F
authors.lastname: Weigend