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Published June 12, 2000 | public
Journal Article

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

Created:
August 19, 2023
Modified:
October 26, 2023