Thermally Tunable Dual Emission of the d8–d8 Dimer [Pt2(μ-P2O5(BF2)2)4]4–

0457999 - ÚFCH JH 2017 RIV US eng J - Článek v odborném periodiku
Hofbeck, T. - Lam, Y. - Ch. - Kalbáč, Martin - Záliš, Stanislav - Vlček, Antonín - Yersin, H.
Thermally Tunable Dual Emission of the d8–d8 Dimer [Pt2(μ-P2O5(BF2)2)4]4–.
Inorganic Chemistry. Roč. 55, č. 5 (2016), s. 2441-2449. ISSN 0020-1669. E-ISSN 1520-510X
Grant CEP: GA MŠMT LH13015; GA MŠMT LD14129; GA MŠMT LL1301
Grant ostatní: COST(XE) cm1202
Institucionální podpora: RVO:61388955
Klíčová slova: High-resolution fluorescence * phosphorescence spectra * [Pt2(μ-P2O5(BF2)2)4]4− (Pt(pop-BF2))
Kód oboru RIV: CF - Fyzikální chemie a teoretická chemie
Impakt faktor: 4.857, rok: 2016

High-resolution fluorescence, phosphorescence, as well as related excitation spectra, and, in particular, the emission decay behavior of solid [Bu4N]4[Pt2(μ-P2O5(BF2)2)4], abbreviated Pt(pop-BF2), have been investigated over a wide temperature range, 1.3–310 K. We focus on the lowest excited states that result from dσ*pσ (5dz2–6pz) excitations, i.e., the singlet state S1 (of 1A2u symmetry in D4h) and the lowest triplet T1, which splits into spin–orbit substates A1u(3A2u) and Eu(3A2u). After optical excitation, an unusually slow intersystem crossing (ISC) is observed. As a consequence, the compound shows efficient dual emission, consisting of blue fluorescence and green phosphorescence with an overall emission quantum yield of ∼100% over the investigated temperature range. Our investigation sheds light on this extraordinary dual emission behavior, which is unique for a heavy-atom transition metal compound. Direct ISC processes in Pt(pop-BF2) are largely forbidden due to spin-, symmetry-, and Franck–Condon overlap-restrictions and, therefore, the ISC time is as long as 29 ns for T < 100 K. With temperature increase, two different thermally activated pathways, albeit still relatively slow, are promoted by spin-vibronic and vibronic mechanisms, respectively. Thus, distinct temperature dependence of the ISC processes results and, as a consequence, also of the fluorescence/phosphorescence intensity ratio. The phosphorescence lifetime also is temperature-dependent, reflecting the relative population of the triplet T1 substates Eu and A1u. The highly resolved phosphorescence shows a ∼220 cm–1 red shift below 10 K, attributable to zero-field splitting of 40 cm–1 plus a promoting vibration of 180 cm–1.

Trvalý link: http://hdl.handle.net/11104/0258318