White OLEDs based on novel emissive materials such as Zn(HPB)2 and Zn(HPB)q

Jang, Yoon-Ki; Kim, Dong-Eun; Kim, Won-Sam; Kim, Byungsang; Kwon, Oh-Kwan; Lee, Burm−Jong; Kwon, Young−Soo

doi:10.1016/j.tsf.2006.10.098

Cited by 17 publications

(4 citation statements)

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“…Neutral zinc complexes containing two ligands are generally recognized as potentially important candidates for the preparation of excellent electroluminescent materials. ,,,, The challenge associated with obtaining suitable single crystals for bidentate zinc complexes was recently discussed , and has necessitated attempts through high-vacuum sublimation of the powder complexes, hydrothermal methods of complex preparation, solvent diffusion or evaporation, and so forth. However, it may not pose such a difficulty to obtain the zinc complex crystals.…”

Section: Resultsmentioning

confidence: 99%

“…Luminescent metal complexes have advantages such as the combination of emitting and electron transferring roles, higher environmental stability, and a better extent of diversity that is achievable through tuning of electronic properties by virtue of structural and metal-center variability . Due to the advantages of vacuum-film-forming or thermal deposition properties, zinc complexes chelated by N−O ligands have attracted attention and have proved to be suitable metal−organic precursors of both academic and industrial relevance. − Through different coordination modes, complexes with the same ligands and metal centers can form monomeric or multinuclear structures by virtue of the oxygen acting as a terminal or bridging donor atom, respectively. , The 2-(imidazol-2-yl)phenol ligand framework is considered a model for the study of Tyr z -His 190 cofactor in photosystem II, and its luminescent properties are widely utilized in research studies of biological interest. − …”

Section: Introductionmentioning

confidence: 99%

“…ESIPT is reported to be extremely rapid in phenols bearing ortho-substituent fragments . Therefore, phototautomerization in both a solid and solutions of related ligands are normally assigned to relaxation from the respective excited state keto tautomers rather than from the primary excited enol states. ,− , Though Zn(II) chelate complexes and others have been extensively explored in search of optimal performance for electroluminescent applications, − systematic investigations of the optical properties of the ligands and zinc complexes are relatively scarce. , Therefore, it would be helpful to design new promising fluorophores through a comparative study of optical properties of N /\ O ligated zinc complexes and the corresponding ligands with an understanding of substituent effects and the influence of condensed media intermolecular interactions. Herein, we present the syntheses, characterization, and photoluminescent properties of 2-(1H-imidazol-2-yl)phenols and their neutral Zn(II) complexes.…”

Section: Introductionmentioning

confidence: 99%

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Syntheses, Structures, and Fluorescent Properties of 2-(1H-Imidazol-2-yl)phenols and Their Neutral Zn(II) Complexes

Eseola

Gao

et al. 2009

Inorg. Chem.

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A series of 2-(imidazole-2-yl)phenol ligands L1-L6 with the general composition 4-R(4)-5-R(3)-6-R(2)-2-(4,5-R(1),R(1)-1H-imidazole-2-yl)phenol (L1: R(1) = C(2)H(5), R(2) = R(3) = R(4) = H; L2: R(1) = C(6)H(5), R(2) = R(3) = R(4) = H; L3: R(1) = C(6)H(5), R(3) = OCH(3), R(2) = R(4) = H; L4: R(1) = C(6)H(5), R(4) = OCH(3), R(2) = R(3) = H; L5: R(1) = C(6)H(5), R(3) = H, R(2) = R(4) = CH(3); L6: R(1) = C(6)H(5), R(3) = H, R(2) = R(4) = t-Bu) and L7 (2,4-di-tert-butyl-6-(1H-phenanthro[9,10-d]imidazol-2-yl)phenol) and their neutral Zn(II) complexes (Z1-Z7) were synthesized and characterized by spectroscopic and elemental analyses. Molecular structures of L1, L5, Z1, and Z2 were confirmed by single-crystal X-ray diffraction. L1 crystallized in the monoclinic Cc space group, while L5, Z1, and Z2 all crystallized in the triclinic P1 space group. One-dimensional arrays based on continuous pi-pi stacking interactions and hydrogen bonding were observed for L1 and Z1, while L5 existed as discrete dimeric stack units. Z2 formed hydrogen-bonded 1D network structures but was completely devoid of pi-pi stacking interactions. Emission processes were found to be more dependent on the substituents on phenol as well as condensed media. In contrast to general conclusions on closely related systems in the literature, significant photorelaxation from the excited enol state was observed in the cases of L1 in methanol and L4 in both THF and methanol. Therefore, there exists a certain unusual hindering factor to keto-enol phototautomerism in the ligand-solvent systems. The sensing property of zinc(II) complexes was explored regarding the effects of substituents in their ligands. It was observed that coordination to the zinc(II) ion led to emission quenching for L1 and L2 while causing an enhancement of fluorescent intensity for L3, L4, L5, and L6. A linear relationship was observed between the emission intensity and the concentration of the zinc ion at the 10(-8) M level. Compared to other zinc compounds in this work, fluorescence enhancement in Z3 and Z4 showed that the methoxyl substituent is favorable for fluorescent enhancement.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Syntheses, Structures, and Fluorescent Properties of 2-(1H-Imidazol-2-yl)phenols and Their Neutral Zn(II) Complexes

Eseola

Gao

et al. 2009

Inorg. Chem.

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“…In this regard, benefiting from the volatility of most Zn( ii )-complexes, a vacuum-deposition procedure for their WOLEDs was employed. One approach is through the mixing of Zn( ii )-complex-based primary colours in a single emitting layer, where the high-energy-state Zn( ii )-complex as the host 16 and/or sensitizer 17 and the low-energy-state complex as the guest 18 can be adopted to produce electrically-driven white light with the desired energy transfer between multiple small-molecule chromophores. Another alternative relies on a multilayer structure consisting of two or more separate emitting layers for WOLEDs, where the superposition of a Zn( ii )-complex within different primary colours, 19 and/or an additional colour-compensation layer by exciplex formation, 20 is also capable of white-light modulation.…”

Section: Introductionmentioning

confidence: 99%