Mono-molecular isomerization processes of aluminium tris (8

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Find more information on the Altmetric Attention Score and how the score is calculated. Cite this: J. Article Views Altmetric. Citations PDF KB. Note: In lieu of an abstract, this is the article's first page. Cited By. This article is cited by 21 publications. Ulrich Biedermann, Israel Agranat. Competition between Bailar and Ray-Dutt paths in conformational interconversion of tris-chelated complexes: a DFT study.

Theoretical Chemistry Accounts, Monomolecular isomerization processes of aluminum tris 8-hydroxyquinolinate Alq3 : a DFT study of gas-phase reaction paths. Chemical Physics Letters, European Journal of Inorganic Chemistry3To browse Academia.

Skip to main content. Log In Sign Up. Monomolecular isomerization processes of aluminum tris 8-hydroxyquinolinate Alq3 : a DFT study of gas-phase reaction paths Chemical Physics Letters, Francesco Lelj.

Monomolecular isomerization processes of aluminum tris 8-hydroxyquinolinate Alq3 : a DFT study of gas-phase reaction paths. Amati, F. Sauro 85, Potenza, Italy Received 5 April ; in final form 17 July Abstract Density Functional Theory has been applied to investigate isomerization processes of aluminum tris 8-hydrox- yquinolinate Alq3.

Both mer—fac isomerization and mer-Alq3 chirality inversion have been reported. This represents an attempt to describe phenomena which could take place during Alq3 amorphous-films deposition or during solid-state changes of phase. Furthermore, it represents the opportunity to apply modern theoretical methodologies to shed light on the general problem of isomerizations in tris—chelate complexes which were widely studied experimentally and by approximate theoretical methods in the seventies and in part of the eighties.

All rights reserved. Introduction solid amorphous phases in spite of its lower sta- bility in gas phase [2]. In this sense, the presence of Aluminum tris 8-hydroxyquinolinate Alq3both isomers has been considered an important Fig. In these devices, Alq3 is present as an volved during vacuum deposition, and could be amorphous thin film normally produced by vac- relevant for good-quality thin-films achievement.

The nature of these films is not Further investigations about Alq3 crystalline completely clear. A point to be clarified is the phases have led to the description of two crystals eventual presence of the different Alq3 octahedral called a-phase and b-phase which surely contain stereoisomers shown in Fig.

According to the- mer-Alq3and a third crystal, called c-phase which oretical investigations, the larger dipole moment of has been associated to the same isomer, also if fac- fac-Alq3 might allow the presence of this isomer in Alq3 cannot be completely excluded [3]. On the other hand, the rate of the K—D racemization processes could assume importance in determining the entity of the local fluctuations of the K and D enantiomers populations.

The possibility to fabricate Alq3 crystals con- taining fac-Alq3 has been recently reported [4]. Besides, a fraction containing mer-Alq3 a-phase as Fig. Aluminum tris 8-hydroxyquinolinate Alq3.

Al- fluctuations of the K- and D-mer-Alq3 populations though the presence of the fac-Alq3 isomer has not in gaseous Alq3 during deposition.

Accordingly, been completely proved, several experimental ob- thermal interconversion between mer- and fac- servations are consistent with its presence. Also Fig. The four octahedral isomers of Alq3. In fact, the mer- complexes. This point received great emphases in Alq3 larger stability has been evinced from NMR the past [12—14], but to date it has not been cor- studies in solution [6], which only described mer- roborated by computational researches based on Alq3and from theoretical investigations in gas actual ab-initio techniques.

Thus, it is expected that gas-phase Alq3 samples are principally composed by mer- Alq3 just like solid samples obtained at low tem- 2. Computational details peratures.These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

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Cite this: J. Article Views Altmetric. Citations PDF 1 MB. Note: In lieu of an abstract, this is the article's first page. Cited By. This article is cited by 76 publications. Frederico T. Lins, Alfredo M.

mono-molecular isomerization processes of aluminium tris (8

Inorganic Chemistry57 17 Kraft and William W. Organometallics33 1 Moore and Kenneth N. Inorganic Chemistry47 19 Rzepa and, Marion E. Inorganic Chemistry46 19 Inorganic Chemistry46 7 Davis, Timothy K.These microbelts were found to aggregate to form flower-like structures on the surface. Scanning electron microscope images and energy dispersive X-ray spectra showed that this reaction is induced at the APA surface by the reaction between the HQ and amorphous Al 2 O 3 species.

Since the pioneering report in by Tang and Van Slyke [ 1 ] on efficient green electroluminescence using tris 8-hydroxyquinoline aluminum Alq 3Alq 3 has been adopted as an important electron transport layer as well as a vital light-emitting material for organic light-emitting diodes.

mono-molecular isomerization processes of aluminium tris (8

The preparation and characterization of Alq 3 have been widely studied [ 2 — 20 ]. Because of the bidentate ligand, Alq 3 complexes form two isomers, as shown in Figure 1 : meridional and facial. Interestingly, the two isomers exhibit different types of photoluminescence PL : specifically, green [ 23 ] in the case of the meridional isomer and blue [ 4 — 7 ] for the facial isomer.

Moreover, Alq 3 crystals with a wide range of morphologies have been prepared, including nanoparticles produced by vapor condensation [ 14 ], nanowires produced using either a single-step heat treatment [ 15 ] or an adsorbent-assisted physical vapor deposition PVD process [ 16 ], pine needle-like crystals produced by PVD [ 3 ], and nanorods produced by solution synthesis with a surfactant [ 17 ].

All of these Alq 3 crystals demonstrate interesting morphology-dependent properties. When Alq 3 nanowires were fabricated by heating mixtures of silica gel and Alq 3they exhibited a blue shift in the absorption spectra with decreasing nanowire diameter, and the photoluminescence vibrational fine structure intensified with increasing excitation energy [ 16 ].

In recent years, anodic porous alumina APA has attracted significant attention in various nanotechnology areas, including light-emitting devices [ 21 ]. As a result, there have been many studies of APA composites with highly fluorescent Alq 3 [ 22 — 26 ].

This study characterizes the crystalline and optoelectronic properties of these unique structures. An Al plate Then, the APA sample was prepared by either one- or two-step anodization. One-step anodization was carried out in 0.

Then, the anodized plate was immersed in a mixed solution of 6. The APA samples were placed in a beaker with distilled water containing HQ under various conditions i.

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Observations of the appearance of the surfaces after drying were noted. After APA was placed in a beaker with distilled water and HQ at various concentrations, times, and temperatures and then dried, visual observations of the surfaces of the APA were made. The upper APA surface was deep yellow due to Alq 3which will be proved laterbut the underside of the plate, where the APA was touching the beaker, was a paler yellow.

The microbelts appear to self-assemble into flower-like structures. Figure 3 shows the XRD patterns for the microbelts in Figure 2. Our XRD results agree with these previous studies at relatively short reaction times. To spectroscopically confirm the phase of Alq 3PL spectra were measured for the microbelts formed on APA surfaces prepared under both anodizing conditions Figure 4.

A rough surface with splinters and cracks is observed on the as-prepared surface a. Although no crystals can be observed on the surface, green fluorescence was observed when the surface was irradiated with ultraviolet light. The former and latter peaks are assigned to the isolated Alq 3 species in nanovoids, while the aggregated Alq 3 species are assigned to the nanopores in the APA. We observed many more particles than microbelts. Thus, it would appear that the nanoparticles aggregate into microbelts.

This temperature dependence gives us some valuable insight.

mono-molecular isomerization processes of aluminium tris (8

The results of the present study indicate that the microbelts are produced by the reaction between the HQ and amorphous Al 2 O 3 species of the APA without a boehmite layer. We considered the growth steps of the Alq 3 crystals formed from the HQ species, based on the sizes of the crystals observed in time-dependence studies Figures 7 a — 7 c : nanoparticles, belt-like structures, and flower-like structures.

These steps appear to be similar to those of the sonochemical fabrication of Alq 3 nanoflowers reported by Mao et al. We propose that the mechanism for evolution of the flower-like crystal morphologies observed in our study can be explained by Ostwald ripening Figure 9 ; 1 the nanoparticles of Alq 3 are formed on the APA surface as a result of the reaction of the HQ, 2 then the precipitated particles grow to form microbelts due to the aggregation of the nanoparticles, and 3 the individual microbelts assemble into flower-like structures.Widely abbreviated Alq 3it is a coordination complex wherein aluminium is bonded in a bidentate manner to the conjugate base of three 8-hydroxyquinoline ligands.

Both the meridional and facial isomers are known as well as several polymorphs different crystalline forms. The compound is prepared by the reaction of 8-hydroxyquinoline with aluminium III sources [4]. Alq 3 is a common component of organic light-emitting diodes OLEDs.

Variations in the substituents on the quinoline rings affect its luminescence properties. From Wikipedia, the free encyclopedia.

CAS Number. Interactive image. Chemical formula. Solubility in water. Chemical Communications.

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Chemistry: A European Journal. Categories : Quinolinols Coordination compounds Aluminium compounds. Namespaces Article Talk.

Views Read Edit View history. Help Community portal Recent changes Upload file. Download as PDF Printable version. Other names 8-Hydroxyquinoline aluminium salt, Alq 3aluminium 8-hydroxyquinolinate, aluminium oxinate. Thermal ellipsoid model of mer -Alq 3 [2].

Tris(8-hydroxyquinolinato)aluminium

Thermal ellipsoid model of fac -Alq 3 [3].Metal-Ligand Interactions pp Cite as. This work has allowed the assignment of the experimental absorption bands of meridianal Alq 3 up to about nm and the theoretical prediction of facial Alq 3 absorption spectrum. The comparison between the absorption and emission characteristics of the two isomers has suggested the spectroscopic properties to be used to distinguish the facial isomer from the meridianal isomer.

Indications have been obtained about the excited state kinetics of the more studied meridianal Alq 3. The evaluation of the reaction surface of the isolated Alq 3 allowed the determination of its monomolecolar isomerization paths and their energetics.

Thus, it has been possible to associate the known high rate of the Alq 3 isomerizations to the dissociative processes which involve the Al-N bond. Furthermore, new suggestions about the Alq 3 chemistry have been introduced. This represents a first glance at the understanding of undesirable processes as atmospheric-induced decomposition and other degradation paths which limit the Alq 3 technological applications.

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Condren, S. Sheats, J. Curioni, A. Schmidbaur, H. B 46Google Scholar.These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily.

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Lec 19: Sn and Bi BASED REAGENTS IN ORGANIC SYNTHESIS

Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated. Cite this: J. Article Views Altmetric. Citations PDF 2 MB. Note: In lieu of an abstract, this is the article's first page.

Cited By. This article is cited by 64 publications. Bradley M. Kraft and William W. Organometallics33 1 Rzepa and, Marion E. Inorganic Chemistry46 19 Davis, Timothy K. Firman, Benjamin P. Hay, and, Kenneth N. Journal of the American Chemical Society29 Inorganic Chemistry40 16 Journal of the American Chemical Society30 Rigby, Donald W.

Hughes, Michael A. Brook, Alex D.


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