Abstract

Several adducts of (n⁵-Me₅C₅)₂Yb(II) (1) and (n⁵-Me₅C₅)₂ YbCl(III) (2) have been found to exhibit photoluminescence (PL) at 295K. The mono-THF adducts of 1 and 2 have served as the parent complexes for this study;^1,2,3 they are orange-red (λ_max ~ 445, 505 and 790 nm)⁴ and purple (λ_max ~ 520 nm), respectively. Electronic spectra of the adducts are sensitive to the Lewis base coordinated to the Yb(II) or Yb(III) center. Excitation into any of the visible absorption bands of 1 at 295K in toluene yields a broad (FWHM ~100 nm) PL band with uncorrected λ_max ~935 nm. Solutions of 1 in THF, compositionally dominated by the bis-THF adduct, exhibit a band of similar character, but possessing, in addition, a shoulder at ~900 nm. Solid-state PL spectra of the mono- and bis-THF adducts of 1 display band maxima at ~960 and 910 nm, suggesting that the shoulder observed in THF solution is due to the bis-THF adduct. The THF data suggest that excited-state adduct dissociation competes favorably with other decay routes of the bis-THF adduct. Other adducts studied by dissolving 1·THF in the corresponding solvent include Et₂0, for which PL at 875 nm is found, and CH₃CN and pyridine, for which no PL between ~700-1000 nm is observed. In THF, 2 exhibits the sharp PL bands characteristic of f-f transitions between ~950-1000 nm; spectra are compared to those previously observed for adducts of (n⁵-C₅H₅)₃ Yb(III).⁵

© 1984 Optical Society of America