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Intersystem Crossing in Diplatinum Complexes

Lam, Yan Choi and Gray, Harry B. and Winkler, Jay R. (2016) Intersystem Crossing in Diplatinum Complexes. Journal of Physical Chemistry A, 120 (39). pp. 7671-7676. ISSN 1089-5639. doi:10.1021/acs.jpca.6b07891.

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Intersystem crossing (ISC) in solid [(C_4H_9)_4N]4[Pt_2(μ-P_2O_5(BF_2)_2)_4], abbreviated Pt(pop-BF2), is remarkably slow for a third-row transition metal complex, ranging from τ_(ISC) ≈ 0.9 ns at 310 K to τ_(ISC) ≈ 29 ns below 100 K. A classical model based on Boltzmann population of one temperature-independent and two thermally activated pathways was previously employed to account for the ISC rate behavior. An alternative we prefer is to treat Pt(pop-BF_2) ISC quantum mechanically, using expressions for multiphonon radiationless transitions. Here we show that a two-channel model with physically plausible parameters can account for the observed ISC temperature dependence. In channel 1, ^1A_(2u) intersystem crosses directly into ^3A_(2u) using a high energy B–F or P–O vibration as accepting mode, resulting in a temperature-independent ISC rate. In channel 2, ISC occurs via a deactivating state of triplet character (which then rapidly decays to ^3A_(2u)), using Pt–Pt stretching (160 cm^(–1)) as a distorting mode to provide the energy needed. Fitting indicates that the deactivating state, ^3X, is moderately displaced (S = 0.5–3) and blue-shifted (ΔE = 1420–2550 cm^(–1)) from ^1A_(2u). Our model accounts for the experimental observation that ISC in both temperature independent and thermally activated channels is faster for Pt(pop) than for Pt(pop-BF_2): in the temperature independent channel because O–H modes in the former more effectively accept than B–F modes in the latter, and in the thermally activated pathway because the energy gap to ^3X is larger in the latter complex.

Item Type:Article
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URLURL TypeDescription Information
Lam, Yan Choi0000-0001-7809-4471
Gray, Harry B.0000-0002-7937-7876
Winkler, Jay R.0000-0002-4453-9716
Additional Information:© 2016 American Chemical Society. Received: August 4, 2016. Revised: September 13, 2016. Publication Date (Web): September 26, 2016. We have enjoyed several stimulating discussions with Tony Vlček and Hartmut Yersin about the nature of excited-state decay pathways in diplatinum complexes. We thank them for their contributions to the field. Our work was supported by NSF CCI Solar Fuels (Grant CHE-1305124). The authors declare no competing financial interest.
Group:CCI Solar Fuels
Funding AgencyGrant Number
Issue or Number:39
Record Number:CaltechAUTHORS:20161003-160458042
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Official Citation:Intersystem Crossing in Diplatinum Complexes Yan Choi Lam, Harry B. Gray, and Jay R. Winkler The Journal of Physical Chemistry A 2016 120 (39), 7671-7676 DOI: 10.1021/acs.jpca.6b07891
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70775
Deposited By: George Porter
Deposited On:04 Oct 2016 14:36
Last Modified:11 Nov 2021 04:34

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