Dynamical processes between triplet sublevels of metal-organic Pt(II) compounds

Strasser, Johann; Donges, Dirk; Humbs, Werner; Kulikova, M. V.; Балашев, К. П.; Yersin, Hartmut

doi:10.1016/s0022-2313(97)00260-3

Cited by 14 publications

(22 citation statements)

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“…Moreover, one finds a pronounced diversity with respect to emission wavelengths, decay times, and quantum yields. [9][10][11][12][13][14][15][16][17][18] An enormous variability is also found regarding sizes and patterns of zero-field splittings (ZFSs) of the triplets into the three substates, 18,19 excitation dynamics within the triplet substate system according to different spin-lattice relaxation (SLR) processes, [19][20][21] vibronic coupling properties, 18 spatial extensions of excited-state wave functions, 18,22 etc. These features may systematically be tuned by the variation of the ligands coordinating the Pt(II) central metal ion.…”

Section: Introductionmentioning

confidence: 99%

Organometallic Pt(II) Compounds. A Complementary Study of a Triplet Emitter Based on Optical High-Resolution and Optically Detected Magnetic Resonance Spectroscopy

Yersin

Donges²,

Humbs³

et al. 2002

Inorg. Chem.

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The emitting triplet state of cyclometalated Pt(thpy)(CO)(Cl) monomers ((thpy)(-) = 2-(2'-thienylpyridinate), frequently also abbreviated as (2-thpy)(-)) is investigated at T = 1.2 K (typically) by use of the complementary methods of high-resolution optical spectroscopy and of optically detected magnetic resonance (ODMR) spectroscopy. Such a complimentary investigation is carried out for the first time for a Pt(II) compound. In solution, oligomer or short linear chain formation is also observed. However, the monomers can be investigated selectively, when they are dissolved in a relatively inert n-octane matrix (Shpol'skii matrix). This allows us to determine the energies of the T(1) triplet substates I, II, and III relative to the electronic ground state S(0)(0), the zero-field splittings (ZFSs) of T(1), and emission decay time constants (I/II <--> 0, 18012.5 cm(-1); III <--> 0, 18016.3 cm(-1); DeltaE(I,II) = 0.05437 cm(-1) (1.631 GHz), DeltaE(I,III) = 3.8 cm(-1) (114 GHz); tau(I) = 120 micros, tau(II) = 45 micros, tau(III) = 35 micros; spin-lattice relaxation time for the processes III --->I/II, tau(SLR) = 3.0 micros). The vibrational satellite structure observed in the emission of the T(1) state to the singlet ground state S(0) is also discussed. Moreover, it is possible to estimate the intersystem crossing time from the excited singlet state S(1) at 22952 cm(-1) to the triplet state T(1) to approximately 5 ps. The T(1) state is assigned as a thpy-ligand-centered (3)pipi* state with small metal-to-ligand charge-transfer (MLCT) admixtures. A comparison of Pt(thpy)(CO)(Cl) to a series of other organometallic Pt(II) compounds, such as heteroleptic Pt(ppy)(CO)(Cl) ((ppy)(-) = phenylpyridinate), Pt(dppy)(CO) ((dppy)(2-) = diphenylpyridinate), and Pt(i-biq)(CN)(2) (i-biq = 2,2'-bisisoquinoline) and homoleptic Pt(thpy)(2) and Pt(ppy)(2), is carried out. (The structures are shown in Figure 7.) Trends of photophysical properties are discussed. In particular, by chelation of two equal ligands the pattern of ZFS is strongly altered, resulting in a significant increase of the MLCT participation in the lowest triplet state of these organometallic compounds. This new observation represents an interesting further step concerning chemical tunability of photophysical properties.

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Section: Introductionmentioning

confidence: 99%

Organometallic Pt(II) Compounds. A Complementary Study of a Triplet Emitter Based on Optical High-Resolution and Optically Detected Magnetic Resonance Spectroscopy

Yersin

Donges²,

Humbs³

et al. 2002

Inorg. Chem.

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“…Of particular significance is the amount of splitting of the triplet into sublevels under zero magnetic field (zero-field splitting, zfs), which in general increases with increasing d character. Also other properties exhibit correspondingly systematic changes, like emission decay times, relaxation properties between the triplet sublevels, radiative rates of the transitions to the ground states, distinctnesses of Franck−Condon progressions, blue shifts of the transition energy upon deuteration, etc. − Interestingly, also the spatial extension of the lowest excited states is controlled by the amount of metal or MLCT character in these states, since this property determines crucially the electronic ligand−ligand coupling in these compounds. Thus, in complexes with small metal character in the corresponding states, such as [Rh(bpy) 3 ] 3+ 26 and [Pt(bpy) 2 ] 2+ with zfs values of the order of 0.1 cm -1 , the lowest excited states are ligand centered (LC) and localized on one ligand 26,27,29,31 (left-hand side of Figure ), while for those compounds with distinct MLCT character, the metal induces a strong ligand−ligand coupling.…”

Section: Introductionmentioning

confidence: 99%

Spatial Extensions of Excited States of Metal Complexes. Tunability by Chemical Variation

and

Humbs

1999

Inorg. Chem.

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The ligand−ligand coupling in excited states of homoleptic metal−organic and related compounds of the platinum metal group depends strongly on the metal d or MLCT character in these states. In particular, in triplet states, which mostly represent the lowest excited states, the metal participation is displayed in the amount of zero-field splitting (zfs). Detailed investigations in recent years have demonstrated that complexes with very small metal participation and thus small zfs, like [Rh(bpy)3]3+ and [Pt(bpy)2]2+, exhibit spatially localized or ligand-centered triplets. Compounds with large metal character as in 3MLCT states have large zfs, and the states are delocalized over the metal and the different ligands, as found for [Ru(bpy)3]2+ and [Os(bpy)3]2+. By chemical variation, it is possible to obtain a compound characterized by an intermediate position between the two extreme situations. Such a compound is Pt(2-thpy)2 with 2-thpy- = 2-(2-thienylpyridinate). It is one of the main subjects of this investigation to study whether in Pt(2-thpy)2 the lowest excited triplet is spatially extended over both ligands. This is done by comparing highly resolved emission (and excitation) spectra of perprotonated Pt(2-thpy-h 6)2, partially deuterated Pt(2-thpy-h 6)(2-thpy-d 6), and perdeuterated Pt(2-thpy-d 6)2. These spectra display clear fingerprints with respect to spatial extensions of the excited states. The required high resolution is obtained when the compounds are dissolved in an n-octane matrix (Shpol'skii matrix) and are measured at low temperature (T = 1.3 and 4.2 K). The deuterated compounds are studied for the first time. Interestingly, it is found that all three triplet sublevels of Pt(2-thpy)2 are spatially extended over both ligands. This result is of high importance, since it tells us that already a moderate metal d or MLCT character in the lowest triplet state of homoleptic compounds of the platinum metal group leads, at least in a rigid matrix, to spatially delocalized excited states.

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“…1 and Refs. [9][10][11][12][13][14]) due to the low density of phonon states corresponding to such zfs patterns.…”

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confidence: 99%

“…Recently, the processes of spin-lattice relaxation and the decay behavior of excited states have been studied experimentally for such systems in Shpol'skii matrices. [8][9][10][11][12][13][14] Of special importance are compounds with a Pt(II) central ion. Pt(II) systems exhibit many different types of low-lying excited triplets that include metal-centered (MC) dd * states [15,16], metal-to-ligand-charge-transfer (MLCT) states [17][18][19], intra-ligand-charge-transfer (ILCT) states [10,13,20], ligand-ligand ′ -charge-transfer (LL ′ CT) states [6,7], and ligand-centered (LC) states with some MLCT and/or MC contribution [21][22][23].…”

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confidence: 99%

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Spin-lattice relaxation in metal-organic platinum(II) complexes

Homeier¹,

Strasser²,

Yersin³

2000

Chemical Physics Letters

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The dynamics of spin-lattice relaxation (slr) of metal-organic Pt(II) compounds is studied. Often, such systems are characterized by pronounced zero-field splittings (zfs) of the lowest-lying triplets. Previous expressions for the Orbach slr process do not allow to treat such splitting patterns properly. We discuss the behavior of a modified Orbach expression for a model system and present results of a fit of the temperature dependence of the spin-lattice relaxation rate of Pt(2-thpy) 2 based on the modified expression.

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Dynamical processes between triplet sublevels of metal-organic Pt(II) compounds

Cited by 14 publications

References 4 publications

Organometallic Pt(II) Compounds. A Complementary Study of a Triplet Emitter Based on Optical High-Resolution and Optically Detected Magnetic Resonance Spectroscopy

Organometallic Pt(II) Compounds. A Complementary Study of a Triplet Emitter Based on Optical High-Resolution and Optically Detected Magnetic Resonance Spectroscopy

Spatial Extensions of Excited States of Metal Complexes. Tunability by Chemical Variation

Spin-lattice relaxation in metal-organic platinum(II) complexes

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