Modulating fluorescence of 8-quinolinolato compounds by functional groups: A theoretical study

Sugimoto, Manabu; Anzai, Masaharu; Sakanoue, Kei; Sakaki, Shigeyoshi

doi:10.1063/1.1408278

Cited by 28 publications

(19 citation statements)

References 12 publications

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“…Experimental results revealed that the emission wavelength of Gaq 3 is longer than that of Alq 3 despite their similar molecular structure, and that emission occurs on the same ligand with different electron cloud structures. Although a previous study indicated that the emission properties of the ligand dominate the fluorescence of the complexes [22], this study showed that the central metal ion does influence the emission properties of these materials. Quantum chemistry calculations were used to examine the geometric and electronic structure of the lowest excited states of the two molecules to interpret the effect of charge transfer from the metal to the ligand on the luminescence characteristics of organic semiconductors chelated to metal ions.…”

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confidence: 73%

The effect of metal electron cloud on the luminescence characteristics of organic ligands: An experimental and theoretical investigation

et al. 2011

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The luminescence processes of metal complexes are complicated by intramolecular charge (energy) transfer from the metal to the ligand or from the ligand to the metal. The charge transfer strongly influences the excited state of the ligand and its luminescence characteristics. The luminescence characteristics of tris(8-hydroxyquinoline) aluminum (Alq 3 ) and tris(8-hydroxyquinoline) gallium (Gaq 3 ) are investigated to reveal the effect of the metal ion on the ligand. Emission from the complexes shows a significant red shift as the size of the metal ion increases from Al to Ga because of more efficient charge transfer from the metal to the ligand. Theoretical calculations on the structure and transition characteristics of the excited states of Alq 3 and Gaq 3 were performed. The calculated emission wavelength agrees with the experimental value and the effect of the metal electron cloud on the emission wavelength is clarified. Organic semiconductor materials attract significant attention because of their huge potential as the active layer in optical electronics applications, such as organic light emitting diodes (OLEDs), organic thin film transistors and organic solar cells [1][2][3][4]. The realization of high performance organic optoelectronic devices strongly depends on the development of novel materials. Some basic and key issues that strongly affect the performance of organic electronic devices, such as charge carriers and transfer, exciton dissociation, molecular arrangement on different substrates and evaporation conditions, have been studied intensively [5][6][7]. However, the dynamic process of the conversion between electricity and light in a single molecule is still not clearly understood.*Corresponding authors (email: fjzhang@bjtu.edu.cn, xjliu@bjtu.edu.cn)Since Tang and VanSlyke [8] first reported that the metal complex tris(8-hydroxyquinoline) aluminum (Alq 3 ) exhibited efficient green light emission more than twenty years ago, Alq 3 has become one of the most popular materials in OLEDs. Following the success of Alq 3 , a series of metal complexes with the same ligand, including 8-hydroxyquinolatolithium [9], tris(8-hydroxyquinoline) gallium (Gaq 3 ) [10], and bis(8-hydroxyquinoline) zinc [11], have been synthesized and used as the active layer in organic electronics. Metal complexes can be classified as one of the following two kinds: (i) complexes that exhibit relatively intense luminescence in the solid state and in solution at room temperature because of metal-to-ligand charge transfer (MLCT) transitions, with the ligand as the luminescent center [12], or (ii) complexes whose luminescence arises from ligand-

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confidence: 73%

The effect of metal electron cloud on the luminescence characteristics of organic ligands: An experimental and theoretical investigation

et al. 2011

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“…1 H, 13 C ATP (APT = attached proton test), and 19 F NMR spectra were recorded by using a Varian Unity 400 spectrometer with a working frequency of 400.0 MHz. Chemical shifts were referenced to the residual resonance signal of the deuterated solvent.…”

Section: Methodsmentioning

confidence: 99%

“…It is noteworthy that compounds 1 e and 1 f do not follow the trend in the aryl-A C H T U N G T R E N N U N G ethynyl series; this can be explained by considering that partial localization of the LUMO density on the nitro and pyridinium oxide moieties and alteration of the nature of the excited state take place. [13] Furthermore, the fluorescence quantum yields and lifetimes exhibited excellent Hammett correlations with the constants s p . [29,30] This shows that the electronic effects are projected through the conjugated spacers to the quinolinolate emitter, thus providing an effective tool not only for systematic tuning of the photophysical properties, but also Electrochemical studies-estimation of HOMO/LUMO levels: Solution electrochemistry methods are known to provide insight into electron-transfer reactions in the condensed phase.…”

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confidence: 89%

“…It appears logical that substitution with suitable functional groups at the phenoxide ring would result in changes in the HOMO levels, and that the LUMO levels would be tuned by substituents on the pyridine ring. [12][13] However, the natural question as to whether substitution in a HOMO node or LUMO node would induce changes in both the HOMO and LUMO levels remained unanswered.…”

Section: Introductionmentioning

confidence: 99%

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Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5‐Substituted Tris(8‐quinolinolate) Aluminum(III) Complexes

Montes

Pohl

Shinar

et al. 2006

Chemistry A European J

170

100

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The unique electron-transport and emissive properties of tris(8-quinolinolate) aluminum(III) (Alq(3)) have resulted in extensive use of this material for small molecular organic light-emitting diode (OLED) fabrication. So far, efforts to prepare stable and easy-to-process red/green/blue (RGB)-emitting Alq(3) derivatives have met with only a limited success. In this paper, we describe how the electronic nature of various substituents, projected via an arylethynyl or aryl spacer to the position of the highest HOMO density (C5), may be used for effective emission tuning to obtain blue-, green-, and red-emitting materials. The synthetic strategy consists of four different pathways for the attachment of electron-donating and electron-withdrawing aryl or arylethynyl substituents to the 5-position of the quinolinolate ring. Successful tuning of the emission color covering the whole visible spectrum (lambda=450-800 nm) was achieved. In addition, the photophysical properties of the luminophores were found to correlate with the Hammett constant of the respective substituents, providing a powerful strategy with which to predict the optical properties of new materials. We also demonstrate that the electronic nature of the substituent affects the emission properties of the resulting complex through effective modification of the HOMO levels of the quinolinolate ligand.

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“…In addition, -CN and -NO 2 have a large influence on the lowest unoccupied molecular orbital (LUMO) through p orbital interactions and result in the red shift of absorption wavelengths with respect to the electron-donating group [18][19][20]. In this paper, we use a serious of electronwithdrawing groups (-CF 3 , -CN, -NO 2 ) in the side chain of the OXD-X as meta-substitution, and settle F on the central phenyl ring as ortho-substitution.…”

mentioning

confidence: 99%

The modulation of electronic and optical properties of OXD-X through introduction of the electron-withdrawing groups: A DFT study

Liu¹,

Pan²,

Zheng³

et al. 2010

Journal of Molecular Graphics and Modelling

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Modulating fluorescence of 8-quinolinolato compounds by functional groups: A theoretical study

Cited by 28 publications

References 12 publications

The effect of metal electron cloud on the luminescence characteristics of organic ligands: An experimental and theoretical investigation

The effect of metal electron cloud on the luminescence characteristics of organic ligands: An experimental and theoretical investigation

Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5‐Substituted Tris(8‐quinolinolate) Aluminum(III) Complexes

The modulation of electronic and optical properties of OXD-X through introduction of the electron-withdrawing groups: A DFT study

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