Lowest Electronic Excited States of Platinum(II) Diimine Complexes
Abstract
Absorption and emission spectra of Pt(diimine)L_2 complexes (diimine = 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (dmbpy); L = pyrazolate (pz-), 3,5-dimethylpyrazolate (dmpz-), or 3,4,5-trimethylpyrazolate (tmpz-)) have been measured. Solvent-sensitive absorption bands (370−440 nm) are attributed to spin-allowed metal-to-ligand charge-transfer (^1MLCT) transitions. As solids and in 77 K glassy solution, Pt(bpy)(pz)_2 and Pt(dmbpy)(pz)_2 exhibit highly structured emission systems (λ_(max)≈ 494 nm) similar to those of the diprotonated forms of these complexes. The highly structured bands (spacings 1000−1400 cm^(-1)) indicate that the transition originates in a diimine-centered ^3(π→π*) (^3LL) excited state. The intense solid-state and 77 K glassy solution emissions from ^3MLCT[d(Pt)→π*(bpy)] excited states of complexes with dmpz- and tmpz- ligands occur at longer wavelengths (λ_(max) = 500−610 nm), with much broader vibronic structure. These findings are consistent with increasing electron donation of the pyrazolate ligands, leading to a distinct crossover from a lowest ^3LL to a ^3MLCT excited state.
Additional Information
© 2000 American Chemical Society. Received November 29, 1999. Publication Date (Web): May 19, 2000. We thank J. A. Bailey, A. J. DiBilio, and J. R. Winkler for many helpful discussions and expert technical assistance. This work was supported by NSF.Additional details
- Eprint ID
- 79923
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- CaltechAUTHORS:20170808-095512740
- NSF
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2017-08-09Created from EPrint's datestamp field
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2021-11-15Created from EPrint's last_modified field