雙光子吸收/發光材料,磷光發光材料及自組裝超分子發光材料的合成及性質探討
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2005
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一、雙光子吸收/發光材料
本實驗研究計畫是針對雙光子吸收材料在三維光訊息存儲、光動力學癌症醫療診斷、雙光子螢光顯微技術、雙光子上轉換激射以及雷射限幅等高科技領域中具有誘人的應用前景所引發的研究興趣,合成含共軛鏈的雙光子吸收/發光材料(two-photon absorption chromophore),並進行光學性質測量及其物性探討。
本計畫主要的合成工作可分為下列幾部分進行,包括:改變各種不同的電子授體(electron donor, abbreviated as D),共軛橋鏈(π-electron conjugated bridge, abbreviated as π),電子受體(electron acceptor, abbreviated as A)及架構(unsymmetric and symmetric systems),作為雙光子吸收/發光材料的研究對象,如:
並利用它們分子內電荷轉移能力的差異,進行單/雙光子吸收截面積(single/two-photon absorption cross section, SPA/TPA),單光子螢光輻射(single-photon excited fluorescence, SPEF),雙光子螢光輻射(two-photon excited fluorescence, TPEF)光譜測量及電化學測量,以探討電荷轉移能量及結構之相關研究。其中,[2,5-bis-[5-(4-diphenylaminophenylethynyl)thiophen-2-yl]-[1,3,4]oxadiazole]的單晶結構,顯示此化合物具有極佳的平面性。在此研究中顯示,適當調整電子授體和電子受體的強度,可使雙光子吸收值,σ,輕易超過1000 GM(1 GM = 10-50 cm4s/photon molecule)。最出色者是以arylamine為電子授體,以pyridazine為電子受體,無論在量子產率及雙光子吸收值都有優異的表現(σ value = 1442 GM and σ/MW = 1.97 GM/g)。
二、Ir錯化物之磷光材料
我們合成一系列的phenylimidazoles (CN) 化合物,這些化合物可以與三氯化銥以cyclometalation的方式配位,形成具有強磷光性質的三CN取代(tris)/雙CN取代(bis)銥金屬化合物。我們針對這些化合物進行光物理及電化學性質的探討。
在光物理方面,配位基CN的吸收光譜範圍從240~350 nm,發射光譜大部分仍在紫外光範圍。當配位基與銥金屬形成錯化物後,其吸收光譜中350~500 nm的範圍歸屬為S0 →1MLCT和S0 →3MLCT的躍遷;這幾種躍遷是因為銥金屬具有強的spin-orbit coupling的特性讓彼此能階相互混合,才可使得原本自旋禁制的三重態躍遷吸收較強。同時也因為銥金屬強spin-orbit coupling的特性使得這些錯化物於室溫或77 K時,在無氧溶液中多有不錯的量子產率(0.01-0.33),有pyrene者除外,這可能來自於pyrene的堆疊所致;且三CN取代者(tris)較雙CN取代者(bis)量子產率為高。其放射出藍綠到綠色的磷光,波長範圍為507~524 nm,且三CN取代者(tris)較雙CN取代者(bis)有稍微紅位移的象,但雙CN取代者有較明顯vibronic feature的圖譜。電化學方面,銥錯化物也可以測得銥(III)氧化成銥(IV)之氧化還原電位,所表現出的特性為,三CN取代者(tris)較雙CN取代者(bis)易氧化。我們也發現到以上這些光物理和電化學性質都與配位基上之N-1位置取代基有很大的關係。
三、自組裝超分子錯化物
超分子化合物(supramolecules)是由一些分子單元以非共價鍵(如氫鍵,配位鍵,靜電力,π-π堆疊力等)自組裝(self-assembly)所產生具有較大分子量,且有特定幾何形狀之化合物。由於與生化方面之分子辨識,反應催化,以及主、客化學之密切關聯,引起了眾多化學家對超分子化學的研究興趣。近年來,超分子在材料化學方面的應用也頗受重視,特別是含有過渡金屬者。因為d軌域上存在的電子可能導致化合物具光、電或磁之性質,成為有用之光、電或磁材料。
本實驗研究的目標,在於以螢光性共軛有機化合物連接Re(CO)3(THF)2Br過渡金屬,藉自組裝(self-assembly)的方式合成超分子化合物(supramolecules)並探討其物性。
Abstract Part A. Two-Photon Absorption Chromophores Series of dipolar and quadrupolar type two-photon absorption (TPA) compounds have been synthesized and TPA cross sections (σ) were measured by Ti:sapphire femtosecond laser excitation fluorescence (λ = 800 nm). Among them, the compound [2,5-bis-[5-(4-diphenylaminophenylethynyl)thiophen-2-yl]-[1,3,4]oxadiazole], has been structurally characterized by X-ray crystallography. The data indicate that the structure of this compound possesses excellent coplanarity. The compounds have arylamines as the donor, and [1,3,4]oxadiazolyl, cyanovinyl or pyridazin-3,6-diyl moiety as the acceptor. Variation of arylamines and pendant alkyl groups was found to have significant influence on σ values. By an appropriate combination of the donor and the acceptor, the σ values of > 103 GM (10-50 cm4s/photon molecule) can be achieved. One quadrupolar molecule possessing arylamine donor and pyridazine acceptor has both high σ value (1442 GM) and σ/MW (1.97 GM/g). Part B. Luminescent Iridium(III) Complexes New phenylimidazoles (CN) have been synthesized. These compounds readily undergo cyclometalation with iridium trichloride, to form bis- or facial tris-cyclometalated iridium complexes, (C^N)2Ir(acac) and Ir(C^N)3 (C^N is the cyclometalated CN). All of these complexes are phosphorescent both at room temperature and 77 K, and the solution quantum yields range from 0.01 to 0.33. All of the complexes Ir(C^N)3 have higher solution quantum yields than (C^N)2Ir(acac), while the latter have more prominent vibronic feature than the former. Complexes containing a pyrenyl moiety have much lower solution quantum yields than their congeners due to the aggregation of the pyrenyl moiety. Part C. Self-Assembly Supermolecules Highly emissive conjugated compounds containing pyridine (or pyrimidine) and cyano ligands have been synthesized by palladium-catalyzed cross-coupling reaction. These ligands readily react with Re(CO)3(THF)2Br to form cyclic supramolecules by self-assembly processes. At room temperature these supramolecules are emissive, and the emission is ligand-localized, as evidenced from the Stokes’ shift and the lifetime data.
Abstract Part A. Two-Photon Absorption Chromophores Series of dipolar and quadrupolar type two-photon absorption (TPA) compounds have been synthesized and TPA cross sections (σ) were measured by Ti:sapphire femtosecond laser excitation fluorescence (λ = 800 nm). Among them, the compound [2,5-bis-[5-(4-diphenylaminophenylethynyl)thiophen-2-yl]-[1,3,4]oxadiazole], has been structurally characterized by X-ray crystallography. The data indicate that the structure of this compound possesses excellent coplanarity. The compounds have arylamines as the donor, and [1,3,4]oxadiazolyl, cyanovinyl or pyridazin-3,6-diyl moiety as the acceptor. Variation of arylamines and pendant alkyl groups was found to have significant influence on σ values. By an appropriate combination of the donor and the acceptor, the σ values of > 103 GM (10-50 cm4s/photon molecule) can be achieved. One quadrupolar molecule possessing arylamine donor and pyridazine acceptor has both high σ value (1442 GM) and σ/MW (1.97 GM/g). Part B. Luminescent Iridium(III) Complexes New phenylimidazoles (CN) have been synthesized. These compounds readily undergo cyclometalation with iridium trichloride, to form bis- or facial tris-cyclometalated iridium complexes, (C^N)2Ir(acac) and Ir(C^N)3 (C^N is the cyclometalated CN). All of these complexes are phosphorescent both at room temperature and 77 K, and the solution quantum yields range from 0.01 to 0.33. All of the complexes Ir(C^N)3 have higher solution quantum yields than (C^N)2Ir(acac), while the latter have more prominent vibronic feature than the former. Complexes containing a pyrenyl moiety have much lower solution quantum yields than their congeners due to the aggregation of the pyrenyl moiety. Part C. Self-Assembly Supermolecules Highly emissive conjugated compounds containing pyridine (or pyrimidine) and cyano ligands have been synthesized by palladium-catalyzed cross-coupling reaction. These ligands readily react with Re(CO)3(THF)2Br to form cyclic supramolecules by self-assembly processes. At room temperature these supramolecules are emissive, and the emission is ligand-localized, as evidenced from the Stokes’ shift and the lifetime data.
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Keywords
發光材料, two-photon absorption chromophore