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Electronic Spectroscopy of Chloro(terpyridine)platinum(II)

Bailey, James A. and Hill, Michael G. and Marsh, Richard E. and Miskowski, Vincent M. and Schaefer, William P. and Gray, Harry B. (1995) Electronic Spectroscopy of Chloro(terpyridine)platinum(II). Inorganic Chemistry, 34 (18). pp. 4591-4599. ISSN 0020-1669. doi:10.1021/ic00122a015.

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The electronic spectrum of [Pt(tpy)Cl]^+ (tpy = 2,2':6',2"-terpyridine) is influenced dramatically by intermolecular stacking interactions in solution and in the solid state. The crystal structure of [Pt(tpy)Cl]ClO_4 (monoclinic, P2_1/c (No. 14); a = 7.085(2), b = 17.064(5), c = 26.905(8) Å; β = 90.0(1) °; Z = 8) consists of discrete Pt_2 units (Pt-Pt = 3.269(1) Å) arranged along an infinite tpy-π stack (spacing ~ 3.35 Å). Variable-temperature and concentration studies of the absorption and emission spectra of [Pt(tpy)Cl]^+ suggest that similar metal-metal and ligand-ligand interactions persist in the solution phase. The high concentration, low-temperature emission spectrum (5:5:1 ethanol:methanol:DMF) reveals a 740-nm band indicative of M-M oligomerization, a 650-nm band attributable to tpy π-π interactions, and a 470-nm band characteristic of mononuclear [Pt(tpy)Cl]^+ π-π* emission. Concentration-dependent absorption spectra were fit to a "two-dimer" model, yielding equilibrium constants for the formation of Pt-Pt-, and tpy-tpy-bound dimers of 1.3(1) x 10^3 and 1.0(1) x 10^3 M^(-1), respectively, in 0.1 M aqueous NaCl. The low temperature solid-state luminescence of [Pt(tpy)Cl]^+ is assigned to a ^3(MMLCT) (MMLCT = metal-metal-to-ligand charge transfer) transition. The energy of this band is highly dependent on the counterion (PF_6^-, ClO_4^- , C1^-, CF_3SO_3^-), in line with the different colors of these various salts. In contrast, the room-temperature solid-state emission spectra are more difficult to interpret. While the red perchlorate salt exhibits a relatively narrow emission band at 725 nm (red-shifted from the 77-K maximum at 695 nm), consistent with a 3(MMLCT) transition, the orange (Cl^-, ClO_4^-, CF_3SO_3^-) and yellow (PF6^-) salts have extremely broad room-temperature emission bands that all appear at nearly the same energy (λ_(max) ~ 640 nm). We assign this luminescence to an eximeric intraligand transition resulting from π- π interactions and propose that the temperature dependent emissions from the orange and yellow solid materials originate from multiple electronic states.

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Gray, Harry B.0000-0002-7937-7876
Additional Information:© 1995 American Chemical Society. We thank C.-M. Che, N. S. Lewis, and G. R. Rossman for experimental assistance and helpful discussions. This work was supported by the National Science Foundation and the Office of Naval Research.
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Office of Naval Research (ONR)UNSPECIFIED
Issue or Number:18
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Official Citation:Electronic Spectroscopy of Chloro(terpyridine)platinum(II) James A. Bailey, Michael G. Hill, Richard E. Marsh, Vincent M. Miskowski, William P. Schaefer, and Harry B. Gray Inorganic Chemistry 1995 34 (18), 4591-4599 DOI: 10.1021/ic00122a015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73655
Deposited By: Tony Diaz
Deposited On:26 Jan 2017 20:08
Last Modified:11 Nov 2021 05:19

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