Absorption spectra, electrochemical behavior, luminescence spectra, and excited-state lifetimes of mixed-ligand ortho-metalated rhodium(III) complexes

Maestri, Matteo; Sandrini, D.; Balzani, Vincenzo; Maeder, U.; Zelewsky, Alex von

doi:10.1021/ic00255a025

Cited by 96 publications

(52 citation statements)

References 4 publications

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“…19,20 Conversely, the luminescence lifetime τ ) 89 ( 5 µs of the title complex is at least 3 orders of magnitude shorter than the lifetime τ > 0.1 s of ppy -. 20 In [Ir(bpy)(ppy) 2 ] + the nominally ppy -centered ligand excitations have radiative lifetimes of 4.5 µs. 3c The significantly longer lifetime in the title complex is the result of a much larger energy gap to the relevant MLCT states, resulting in a smaller admixture of MLCT character.…”

Section: Mixing Of Lc and Mlct Charactermentioning

confidence: 90%

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)₄(ppy)] (ppy = 2-Phenylpyridine)

et al. 1997

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The cyclometalated complex [Re(CO) 4 (ppy)], where ppy -) 2-phenylpyridine, was synthesized. Its crystal and molecular structure was determined by X-ray diffraction. The lowest energy electronic excitations were studied by high-resolution optical spectroscopy at cryogenic temperature. The first excited state in [Re(CO) 4 (ppy)] is nominally a triplet ligand-centered state, with 1.8% metal-to-ligand charge transfer character mixed in through spin-orbit coupling. This induces a shortened lifetime (89 µs at 10 K) and the occurrence of metal-ligand vibrations in both absorption and luminescence spectra. The transition moment of the first electronic excitation lies in the molecular plane with a tilt toward the pyridine part of the ppy -ligand. This is derived from the polarized absorption measurements and confirmed by an extended Hückel calculation. Splittings in the IR absorption bands are resulting from the presence of two crystallographically equivalent complexes in the unit cell which are tilted with respect to each other.

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Section: Mixing Of Lc and Mlct Charactermentioning

confidence: 90%

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)₄(ppy)] (ppy = 2-Phenylpyridine)

et al. 1997

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“…The electronic origin is at 520.7 nm (19,204 cm -1 ). As discussed elsewhere [54], the vibrational structure is characteristic of an emissive pp* state localized on a thpyligand. Furthermore, it was determined that, at 4.2 K, the emitting level lifetime is 204 ms [72].…”

Section: [Rh (Thpy) 2 (Bpy)] +mentioning

confidence: 73%

“…It has long been recognized that the emissive state of Rh(III)-(aza)-aromatic compounds is primarily of ligand-localized 3 pp* nature [51][52][53][54]. This assignment for the Rh 3+ (4d 6 ) chelate emission is mainly based on the resemblance of the emission spectra of the free and coordinated ligand molecules.…”

Section: Odmrmentioning

confidence: 99%

Excited State Spectroscopy and Excited State Dynamics of Rh(III) and Pd(II) Chelates as Studied by Optically Detected Magnetic Resonance Techniques

Glasbeek

2000

Transition Metal and Rare Earth Compounds

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In this paper we review optically detected magnetic resonance (ODMR) investigations of a series of Rh 3+ (4d 6 ) and Pd 2+ (4d 8 ) complexes in the lowest excited electron spin triplet state. Starting with a brief survey of the technique of optical detection of magnetic resonance, zerofield and low-magnetic field ODMR results are reviewed for the tris-diimine chelates [Rh(phen) n (bpy) 3-n ] 3+ , where phen = 1,10-phenanthroline, bpy = 2,2¢-bipyridine, and n = 0, 2, or 3, and for the mixed cyclometalated chelates [Rh(thpy) x (phpy) 2-x (bpy)] + , with thpy = 2,2¢thienylpyridinate, phpy -= 2-phenylpyridinate, and x = 1, or 2. The ODMR data reveal fine structure splittings in the phosphorescent excited state of the complexes comparable in magnitude to those known for the nonchelated ligand molecules in the excited triplet state. Anisotropy studies of the ODMR spectra for the single crystals in low magnetic fields show that the lowest electronic excitation in the complexes is a triplet state indeed and that this state is localized on a single ligand molecule per metal ion site. From microwave recovery experiments, performed under conditions that the spin-lattice relaxation can be neglected (T≤ 2 K), detailed information concerning the triplet sublevel lifetimes is obtained. The lifetimes are on the millisecond timescale, i.e., three orders of magnitude shorter than for the nonchelated ligand molecules. The lifetime shortening as well as the observed spin-selective radiative decay of the triplet sublevels of the ligand molecule are discussed in detail on the basis of enhanced spin-orbit couplings caused by the central (heavy) metal ion. Optically detected spin coherence experiments (transient nutation and spin echo decay) are also discussed. The results show that the homogeneous line broadening of the ODMR transitions of the metal complexes in the emissive triplet state is approximately 100 kHz. The homogeneous broadening is attributed to the effects of flip-flop motions of ligand proton spins that randomly modulate the triplet electron spin levels on account of dipolar electron spin -nuclear spin couplings. Finally, recent ODMR and PMDR (phosphorescence microwave double resonance) experiments performed for the Pd 2+ -chelates, Pd(thpy) 2 and Pd(qol) 2 (with qol -= 8-hydroxyquinolinate) in Shpol'skii matrices are discussed. The lowest excited electronic state in these molecules is also emissive and ODMR spectra at zero-and low magnetic fields have been observed. For Pd(thpy) 2 only one zero-field ODMR transition could be measured, but it is argued that this transition originates in an excited triplet state. The results of the microwave recovery experiments could be related to time-resolved emission experiments in high magnetic fields. Spin selectivity in the vibronic line emission is demonstrated by means of PMDR.

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“…This is because the emission energy of the metal complex is limited by the 3 LC energy of the ppy ligand itself (ppyH; E T = 430 nm, 2.88 eV) [113] . One approach that was pursued to blue shift the emission relative to Ir(ppy) 3 involved decreasing the size of the C ∧ N π -system, by replacing the phenyl ring with a vinyl group.…”

Section: Near -Uv Luminescent Cyclometallated Complexesmentioning

confidence: 99%

Cyclometallated Organoiridium Complexes as Emitters in Electrophosphorescent Devices

Djurovich

Thompson

2007

Highly Efficient OLEDs With Phosphorescent Materials

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A brief overview is presented on cyclometallated iridium complexes that are used as phosphorescent dopants in organic light -emitting devices (OLEDs). Comparisons between devices made using either Pt(octaethylporphyrin) or Ir(phenylpyridyl) 3 as dopants are used to illustrate some parameters needed for optimal performance of electrophosphorescent OLEDs. The molecular properties responsible for the high luminescent effi ciency of the Ir complexes are then described. Interactions between the triplet ligand state and the singlet and triplet metal -to -land charge transfer states are responsible for photophysical characteristics of the complexes. Examples are given of various ligand combinations used to control the phosphorescent energy and effi ciency. This knowledge enables one to systematically tune the emission colors of these complexes from the near -UV to the near -infrared spectral regions. Organic Light -Emitting DevicesThe future holds tremendous opportunity for the low cost and high performance offered by organic LEDs. The term organic light -emitting device (OLED) refers to any light -emitting diode that is composed of either molecular or polymeric materials. Full -color displays that use OLEDs may eventually replace liquid -crystal displays (LCDs) in a range of mobile applications, ranging from cellular phones to laptop computers. The low power dissipation and high brightness of OLEDs make them ideal for such portable applications. OLED displays can be deposited on fl exible plastic or metal foils, eliminating the fragile and heavy glass substrates used in LCDs and other fl at panel displays. Moreover, OLED displays emit light without the pronounced directionality inherent in LCD viewing, all with effi ciencies signifi cantly higher than typical LCD panels. It is possible that portable and lightweight roll -up OLED displays will someday cover our walls. Another important application for OLEDs is in illumination. The high effi ciencies and excellent color qualities for white OLEDs make them promising candidates for replacing conventional fl uorescent and incandescent light sources.

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Absorption spectra, electrochemical behavior, luminescence spectra, and excited-state lifetimes of mixed-ligand ortho-metalated rhodium(III) complexes

Cited by 96 publications

References 4 publications

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)₄(ppy)] (ppy = 2-Phenylpyridine)

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)₄(ppy)] (ppy = 2-Phenylpyridine)

Excited State Spectroscopy and Excited State Dynamics of Rh(III) and Pd(II) Chelates as Studied by Optically Detected Magnetic Resonance Techniques

Cyclometallated Organoiridium Complexes as Emitters in Electrophosphorescent Devices

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Absorption spectra, electrochemical behavior, luminescence spectra, and excited-state lifetimes of mixed-ligand ortho-metalated rhodium(III) complexes

Cited by 96 publications

References 4 publications

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)4(ppy)] (ppy = 2-Phenylpyridine)

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)4(ppy)] (ppy = 2-Phenylpyridine)

Excited State Spectroscopy and Excited State Dynamics of Rh(III) and Pd(II) Chelates as Studied by Optically Detected Magnetic Resonance Techniques

Cyclometallated Organoiridium Complexes as Emitters in Electrophosphorescent Devices

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Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)₄(ppy)] (ppy = 2-Phenylpyridine)

Synthesis, Crystal Structure, High-Resolution Optical Spectroscopy, and Extended Hückel Calculations on Cyclometalated [Re(CO)₄(ppy)] (ppy = 2-Phenylpyridine)