激基缔合物和激基复合物的形成及溶剂效应的研究

测试了ω-对联苯基多亚甲基羧酸4-[5′-对联苯基-1,3,4-(口恶)二唑基-2′-]苄酯及其模型化合物2-对甲苯基-5-联苯基-1,3,4-,(口恶)二唑在不同极性溶剂中的荧光发射光谱。它们既能形成分子间的激基缔合物又能形成分子内的激基复合物和三分子激基复合物。实验结果表明,溶剂极性的增加,有利于分子内激基复合物和三分子激基复合物的形成。     

外围萘修饰PAMAM树枝形聚合物的合成及其质子化过程研究

合成了外围修饰有萘基团的0～3代聚酰胺-胺树枝形聚合物GnN (n＝0～3), 化合物通过了IR, 1H NMR, 13C NMR和MALDI TOF的表征. 稳态光物理研究表明, 甲醇溶液中GnN外围萘基团与骨架胺之间发生电子转移过程, 形成最大发射峰在450 nm的激基复合物, 萘的荧光被明显猝灭; 当GnN骨架被质子化, 分子内光致电子转移过程和萘与骨架胺基间激基复合物的形成被抑制, 萘单体荧光发射大大增强; 由于质子化后树枝形聚合物骨架趋于伸展构象, 外围萘基团间相互作用增强, 部分形成最大发射峰在400 nm的激基缔合物.     

双-β-萘甲基二胺及其衍生物的荧光光谱及分子内激发态复合物的形成

我们合成了N,N'-二甲基-二-β-萘甲基乙二胺(Ⅰ),N,N'-二甲基-二-β-萘甲基丙二胺(Ⅱ),N,N'-二-β-萘甲基哌嗪(Ⅲ)三个化合物,并测定了它们的荧光光谱。结果表明,它们既能形成分子内激基缔合物(excimer),又能形成分子内激基复合物(exciplex),与溶剂极性有关。在极性较大的溶剂如乙腈和甲醇中,由于激基复合物几乎完全解离因而不发射荧光,这时观察到的荧光峰蓝移而且强度增加,可以认为,这是激基缔合物存在的证明。这三个化合物的分子内激基缔合物形成的难易程度按Ⅱ>Ⅰ>Ⅲ的次序依次递降。     

多足化合物的分子内激基缔合物形成及pH对其荧光的影响

研究了含萘脲基多足化合物溶液的稳态和瞬态光物理行为.由于分子内不同足间脲基的相互作用干扰了萘基的π-π叠合,使分子内萘基的激基缔合物生成受到影响.实验表明:由于三足化合物存在着给电子叔胺基团,因此当萘基被激发时、可因分子内的光诱导电子转移而导致荧光猝灭.正因如此,在三足化合物归一化后的稳态光谱中激基缔合物的发光强度很弱.用皮秒级单光子记数技术测得该化合物的瞬态荧光为三指数衰变过程.其中最长寿命的物种,即属于生成激基缔合物后再分解为萘激发态的部分仅占总量的4%,与稳态的结果相一致.工作表明对这类可用作荧光化学敏感器的三足化合物,如利用其激基缔合物的强度变化为其识别外来物种的敏感部位并不适合.相反,如引入的外来物种能影响化合物的分子内光诱导电子转移,进而影响萘基的发光强度,则是一较好的判别外来物种是否已进入主体的标志.     

有机化合物的光物理研究——Ⅸ.三苯胺在不同极性溶剂中的时间分辨瞬态光谱

本文研究了三苯胺(TPA)在不同溶剂中的时间分辨瞬态吸收光谱,测定了三苯胺在不同溶剂中的荧光寿命。讨论了瞬态吸收峰的归属。在正已烷和乙醇中,观察到了三苯胺的三重态瞬态吸收峰(λ_(max)=430nm)和三重态激基缔合物的瞬态吸收峰(λ_(max)=625nm)。在乙腈中,除观察TPA三重态和三重态激基缔合物的瞬态吸收外,还观测到TPA~+的瞬态吸收峰。根据实验结果,提出了TPA在不同极性溶剂中的光物理瞬态过程及其与溶剂相互作用的反应机理。     

一种新型的分子内激基缔合物——双-β-萘基烷烃及其衍生物分子内激基缔合物的研究

本文报道几种双-β-萘甲酸多次甲基二醇酯及双-β-萘基烷烃次甲基链上被极性基团取代的衍生物的合成及其荧光谱。结果表明,它们都能形成分子内激基缔合物,对于双-β-萘甲酸多次甲基二醇酯来说,其分子内激基缔合物的荧光强度与链长有关,以三次甲基链为最大。对于双-β-萘基烷烃取代衍生物来说,由于吸电子基团的引入使两个萘环的电子云密度不等,它们所形成的分子内激基缔合物的荧光峰都比未取代的1,3-双-β-萘基丙烷有所蓝移。在极性溶剂乙腈中其分子内激基缔合物的荧光峰的位置虽然不变,但I_E/I₂值则有所降低,表现出既不完全与激基缔合物相同,又不完全与激基复合物相同的性质。     

时间分辨荧光光谱研究聚2-乙烯基萘与对苯二甲酸二甲酯形成的三分子激基复合物

本文研究了在稀溶液中,聚2-乙烯基萘分子内不同生色团之间相互作用后先形成分子内激基缔合物,然后与受体分子相互作用后再生成三分子激基复合物的机理。测定了聚2-乙烯基萘分子内激基缔合物的荧光寿命的r_2=18.83ns;形成三分子激基复合物的速度常数k_7=4.18×10~9(mol/L)~(-1)S~(-1),受扩散速度反应控制。首次提出了激基缔合物或激基复合物可能是形成三分子激基复合物的中间体,并提出了由激基缔合物再形成三分子激基复合物的光物理过程的理论模型。     

N,N′-双-β-萘甲基哌嗪分子内激发态复合物形成的混合溶剂效应

本文测定了N,N′-双-β-萘甲基哌嗪(DMNP)在苯与乙腈混合溶剂中的荧光光谱。在乙腈含量<5(mol·dm^-3)时,乙腈猝灭DMNP苯溶液的荧光符合Stern-Volmer方程,表明极性溶剂分子乙腈与DMNP分子内激基复合物存在着相互作用。随着乙腈含量的增加,DMNP分子内激基复合物(exci-plex)荧光的猝灭与红移以及分子内激基缔合物(excimer)的逐步形成则仅与体系的极性有关。文中还讨论了DMNP激发态复合物形成的机理。     

疏水作用对光化学和光物理过程的影响 Ⅶ.芘基烷基酮的荧光光谱及其在不良溶剂中的簇集

溶剂的极性对芘基烷基酮的单体荧光和激基缔合物荧光有很大影响,在非极性溶剂中单体荧光很弱,随着溶剂极性增大,单体荧光增强,单体荧光和激基缔合物荧光明显红移。利用芘基烷基酮荧光的这些性质研究了长链分子在二甲基亚砜-水(DMSO-H₂O)中的簇集现象。在浓度非常低的情况下,长链芘基烷基酮发射激基缔合物荧光,单体荧光也明显蓝移,表明芘基烷基酮形成了簇集体。长链饱和烷烃和芘基烷基酮发生共簇集,簇集体内的极性比环己烷的极性稍大。     

纳米二氧化硅为核的树枝状分子中荧光素激基缔合物和基态复合物的形成

在以二氧化硅为核的聚酰胺(PAMAM)树枝状聚合物的外端, 通过表面化学修饰引入了具有发射荧光能力的荧光素分子. 通过稳态荧光方法研究其固体和在水和丙酮的悬浮液中的光物理行为. 试验结果表明, 固体样品中, 在零代树枝状分子(G0F)中, 荧光发射主要是激基缔合物的发射, 在第一(G1F)和第二代(G2F)中只有基态复合物的发射. 在不同的悬浮液中不同的光物理行为表明, 树枝状分子中树枝链间的氢键作用的大小决定荧光素基团间是形成激基缔合物还是形成基态复合物. 这为设计和开发新型“壳-核”型纳米二氧化硅荧光传感器提供了有用的实验依据.     

Intramolecular excimer formation and photoinduced electron-transfer process in bis-1,8-naphthalimide dyads depending on the linker length

The photophysical properties of bis-1,8-naphthalimide (NI-L-NI) dyads with different linkers ( L = -C 3H 6-, -C 4H 8-, -C 6H 12-, -C 8H 16-, and -C 9H 18-) as well as the reference NI derivative (NI-C 7H 15) were investigated in CH 3CN and H 2O/CH 3CN (v/v = 1:9). The normal fluorescence peak of (1)NI*-L-NI was observed at 379 nm together with a broad emission at longer wavelength both in aprotic CH 3CN and in H 2O/CH 3CN, which is assigned to an excimer, (1)(NI-L-NI)*. The excimer emission maximum was blue-shifted with increasing length of the linker. The photoinduced electron-transfer process of NI-L-NI was also investigated in both solvents by using nanosecond-laser flash photolysis. The T 1-T n absorption band for (3)NI*-L-NI was observed around 470 nm in both solvents. In H 2O/CH 3CN, NI-L-NI is solvated with H 2O in the ground state to exist as solvated NI-L-NI. In the excited triplet state, the NI radical anion (NI (*-)) was generated via the intramolecular quenching of (3)NI*-L-NI by another NI moiety. The solvated NI (*-)-L-NI may undergo the proton abstraction process to give NI(H) (*)-L-NI, which can be confirmed by the transient absorption band at 410 nm. This band was not observed in pure aprotic CH 3CN.     

四(4,4',4'',4'''-N,N-二氨基)四苯乙烯光致发光与分子的构象效应

利用还原偶联方法合成出新化合物四(4,4',4',4''-N,N-二氨基)四苯乙烯（ TDETE）。通过测定该化合物在溶液、掺杂聚合物中及晶体粉末的稳态-瞬态荧光光 谱、荧光量子产率和辐射衰变速率常数等。讨论了分子的构象效应等因素对TDETE 光致发光行为的影响。在一定浓度下TDETE溶液存在着三个发光带,分别为全扭曲 构象分子（位于345nm附近的发光I带）、半扭曲构象分子（位于430nm附近的发光 II带）和激基缔合物（530发光III带）的辐射衰变所致。在聚合物（PMMA）中,一 方面由于分子单键的自由旋转扭曲受到遏制,表现为II带的辐射衰变速率常数(kf 值)增大、同时非辐射衰变速率常数knf值减小;另一方面,TDETE分子之间相互作 用得到加强而有利一缔合物形成,结果,使发光II带和III带合二为一出现强而宽 的发射峰,荧光量子产率从溶液中的0.055提高到0.855。此外,在PMM介制裁中观 测到TDETE分子聚集体在626nm处的发光带（IV）,数粉末态中聚集体IV带的强度骤 增,峰值波长红移至650nm。     

Synthesis, evaluation, and computational studies of naphthalimide-based long-wavelength fluorescent boronic Acid reporters

Boronic acids that change fluorescence properties upon sugar binding are very useful for the synthesis of carbohydrate sensors. Along this line, boronic acids that fluoresce beyond 500 nm are especially useful. A series of boronic acid fluorescent reporter compounds based on the 4-amino-1,8-naphthalimide structure have been synthesized (1a-d) and evaluated under near physiological conditions. These compounds showed good water solubility and significant changes in fluorescence properties after binding with sugars, with the emission wavelength being at around 570 nm. Analogues in this series with different substitutions showed similar properties. We have also examined the mechanism of the observed fluorescence changes for these compounds.     

Structural organization of a {ruthenium[tris(bipyridyl)]} complex by strong π–π stacking of a tethered 1,8-naphthalimide synthon: Impact on electrochemical and spectral properties

The new ligand N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide has been prepared by the reaction of 1,8-naphthalimide, 5-(bromomethyl)-2,2′-bipyridine and potassium carbonate in refluxing acetone. Reaction of this ligand and bis(bipyridyl)ruthenium(II) dichloride in refluxing ethanol followed by anion exchange with ammonium hexafluorophosphate produces {ruthenium[bis(bipyridyl)][N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide]}(PF₆)₂ (1). In both the solid state (X-ray analysis) and in solution (shown by PGSE-NMR analysis), the 1,8-naphthalimide synthon organizes the cationic metal units into dimers with a strong, directionally oriented (head to tail) π–π stacking interaction. UV–VIS, fluorescence spectroscopy and electrochemical studies indicate that even with the strong interactions of the 1,8-naphthalimide groups, it does not have a significant influence on the properties of the [Ru(bipy)₃]²⁺ core.     

ESIPT-regulated Mechanoresponsive Luminescence Process byIntroducing Intramolecular Hydrogen Bond in NaphthalimideDerivatives#br#

Herein, two compounds, 4-2′-hydroxybenzylidenehydrazinyl-N-butyl-1,8-naphthalimide(BN-1) and 4-benzylidenehydra-zinyl-N-butyl-1,8-naphthalimide(BN-2), were synthesized to explore the hydrogen bonding effect on mechanoresponsive luminescent(MRL). The results showed that compound BN-1 exhibited strong emission in solution and solid-state compared with compound BN-2. After grinding, the emission intensity of compound BN-1 sharply decreased by as much as 15 times with an obvious red-shift from 552 nm to 577 nm. The control compound BN-2, by contrast, did not change so much before and after grinding. Single crystal analysis suggests that BN-1 molecule formed strong intramolecular interaction via ―N=N···H―O hydrogen bond with a distance of 0.2632 nm. An excited-state intramolecular proton transfer(ESIPT) based fluorophore featured this intramolecular hydrogen bond. The intramolecular hydrogen bond as well as other intermolecular interactions can rigidify the molecular conformation of compound BN-1 in solid-state, and thus suppress the nonradiative pathways, resulting in strong emission. These intra- and intermolecular interactions were destroyed by mechanical stimuli, accompanied by molecular conformation change that decreases the luminescence and blocks the ESIPT process. The MRL process was also demonstrated by scanning electron microscopy and powder X-ray diffraction. The molecular stacking mode changed from crystalline to a disordered amorphous state after grinding.     

A ratiometric fluorescent probe for the detection of hypochlorous acid in living cells and zebra fish with along wavelength emission

A ratiometric fluorescence probe, NClO, for the rapid and selective detection of HClO had been designed and synthesized based on a 1,8-naphthalimide derivative. Probe NClO displayed a red emission(λ_(max)= 615 nm). In the presence of HClO, the solution of probe NClO gave off a strong green fluorescence(λ_(em), _(max)= 520 nm) with a rapid response(within seconds). This probe had been applied to image HClO in living cells and zebra fish.     

A novel fluorescent molecule based on 1,8-naphthalimide: synthesis,spectral properties,and application in cell imaging

A novel naphthalimide molecule, 4-(2-methoxyethoxy)-N-butyl-1,8-naphthalimide (MEBN), has been synthesized and characterized. The UV–visible absorption and fluorescence emission spectral properties in n-hexane, toluene, CHCl₃, and CH₃OH were studied. Its optical properties depend on solvent polarity. The application of MEBN in cell imaging was investigated.     

Photophysics and biological applications of the environment-sensitive fluorophore 6-N,N-dimethylamino-2,3-naphthalimide

We have synthesized a new environment-sensitive fluorophore, 6-N,N-dimethylamino-2,3-naphthalimide (6DMN). This chromophore exhibits valuable fluorescent properties as a biological probe with emission in the 500-600 nm range and a marked response to changes in the environment polarity. The 6DMN fluorescence is red-shifted in polar protic environments, with the maximum emission intensity shifting more than 100 nm from 491 nm in toluene to 592 nm in water. Additionally, the fluorescence quantum yield decreases more than 100-fold from chloroform (Phi = 0.225) to water (Phi = 0.002). The scope and applications of the 6DMN probe are expanded with the synthesis of an Fmoc-protected amino acid derivative (5), which contains the fluorophore. This unnatural amino acid has been introduced into several peptides, demonstrating that it can be manipulated under standard solid-phase peptide synthesis conditions. Peptides incorporating the new residue can be implemented for monitoring protein-protein interactions as exemplified in studies with Src homology 2 (SH2) phosphotyrosine binding domains. The designed peptides exhibit a significant increase in the quantum yield of the long wavelength fluorescence emission band (596 nm) upon binding to selected SH2 domains (e.g., Crk SH2, Abl SH2, and PI3K SH2). The peptides can be used as ratiometric sensors, since the short wavelength band (460 nm) was found almost invariable throughout the titrations.     

Photoisomerization and [2 + 2] photocycloaddition in bichromophoric styrylbenzoquinoline dyads with <Emphasis Type="Italic">o</Emphasis>-xylylene bridge group

Photochemical properties of bis(styrylbenzoquinoline) dyads in which two styrylbenzoquinoline (SBQ) moieties are bridged by an o-xylylene group linked to their styryl groups via oxy- and carboxy-functional groups have been studied. Two competitive reactions, photoisomerization of the SBQ moieties and stereoselective [2 + 2] photocycloaddition (PCA) to give tetrasubstituted cyclobutane, occur under irradiation. It is assumed that PCA occurs with participation of an intramolecular excimer, in which the photochemical process of dimerization to cyclobutane dominates over the photophysical process of fluorescence, because the emission band of the excimer is not observed in an explicit form in the fluorescence spectra of dyads.     

Intramolecular exciplex and intermolecular excimer formation of 1,8-naphthalimide-linker-phenothiazine dyads

Steady-state fluorescence spectra were measured for 1,8-naphthahlimide-linker-phenothiazine dyads (NI-L-PTZ, where L = octamethylenyl ((CH2)8) and 3,6,9-trioxaundecyl ((CH2CH2O)3C2H4)), NI-C8-PTZ and NI-O-PTZ, as well as the NI derivatives substituted on the nitrogen atom with various linker groups without PTZ as the reference NI molecule in n-hexane. Normal fluorescence peaks were observed at 367-369 nm in all NI molecules together with a broader emission around 470 nm, which is assigned to the excimer emission between the NI in the singlet excited state (1NI*) and the NI moiety of another NI molecule (1[NI/NI]*). In addition, a broad peak around 600 nm was observed only for NI-L-PTZ, which is assigned to an intramolecular exciplex emission between donor (PTZ) and acceptor (NI) moieties in the excited singlet state, 1[NI-L-NI]*. The formation of an intramolecular exciplex corresponds to the existence of a conformer with a weak face-to-face interaction between the NI and PTZ moieties in the excited state because of the long and flexible linkers. The excited-state dynamics of the NI molecules in n-hexane were established by means of time-resolved fluorescence spectroscopy.