水杨酰苯胺衍生物分子内电荷/质子转移荧光

将苯甲酰苯胺(BA)类电荷转移(CT)反应基团耦合到具有激发态分子内质子转移(ESIPT)反应通道的水杨酸(SA)分子中,设计合成了苯胺对/间位取代的水杨酰苯胺及其羟基甲基化衍生物邻甲氧基苯甲酰苯胺,考察了环己烷、乙醚、乙腈和甲醇中两类水杨酰苯胺衍生物吸收光谱和荧光光谱的溶剂效应和取代基效应.结果表明,水杨酰苯胺的荧光为SA-型质子转移(PT)荧光,对取代基的依赖性较小;当电子给体苯胺基的给电子能力提高时,如N-甲基水杨酰苯胺分子,其荧光为BA-型CT荧光.而羟基甲基化后的衍生物邻甲氧基苯甲酰苯胺则表现出与BA类似的荧光光谱特性,具有明显的取代基效应.认为水杨酰苯胺衍生物的激发态存在着相互竞争的BA-型CT和SA-型PT通道,二者可经苯胺基上取代基的电子效应调控.     

电化学方法用于分子内电荷转移特性的研究

设计合成一系列具有不同取代基的苯甲酰萘（苯）胺衍生和，测定它们在非极性溶剂环己烷中的荧光发射光谱，发现系列合成产物具有双重荧光，其长滤发射具有电荷转移特性，其长波发射态能量与不同取代基的苯甲酰萘（苯）胺衍生物的失（得）电子能力，即给（受）体的氧化还原电位之间符合Weller方程。     

ESIPT和TICT荧光发射的电子结构特征及发射能计算

采用含时密度泛函理论(TDDFT)与单激发组态相互作用(CIS)相结合的计算方案对八种结构相似的水杨酰苯胺衍生物及其类似物第一激发单重态(S1)进行考察, 证实它们的荧光发射分属分子内质子转移(ESIPT)和分子扭转-电荷转移(TICT)两种不同机制且结论与已知实验事实相符. ESIPT发光的化合物在电子跃迁前后无明显的电荷转移发生, 发射能计算的适用泛函是OLYP和BLYP等无Hartree-Fock(HF)交换成分的纯泛函; TICT发光的化合物在电子跃迁前后发生明显的电荷转移, 其适用泛函为含约37% HF交换成分的混合型泛函(例如mPW1B95和MPW1K). 按上述原则来选择适用泛函, 即可在TDDFT/6-31G(d)//CIS/3-21G(d)理论水平上正确预测水杨酰苯胺衍生物和类似物的发射能, 平均精度可达0.2 eV. 兼具质子转移与电荷转移双反应通道的化合物, 两者的竞争遵从能量最小原理, 结果使荧光发射仅选择其中一个通道进行. 泛函的选择只与实际发生的反应有关, 与并未实际发生的反应通道无关. 附加的八个算例进一步表明, 此成功的计算方案可望推广应用于其它类型的ESIPT和TICT荧光有机物.     

一类新型分子内电荷转移荧光体——苯甲酰苯胺衍生物

评述了苯甲酰苯胺及其衍生物的发光行为和电荷转移/质子转移光物理模型的研究进展,并展望了该类新型分子内电荷转移荧光体在化学及生物分子识别与传感中的潜在应用前景.     

聚丙烯酸[2,5-双(对甲氧基苯甲酰氧基)苄酯]及聚甲基丙烯酸[2,5-双(对甲氧基苯甲酰氧基)苄酯]的合成

周其凤等曾报道聚丙烯酸［２,５－双（对甲氧基苯甲酰氧基）节酯］［１］和聚甲基丙烯酸［２,５－双（对甲氧基苯甲酰氧基）苄酯］［２］的合成．但后来的研究发现,在合成单体的条件下出现的一种未见报道的异常反应［３］使产物成分复杂化,因此当时报道的聚合物可能不是聚丙烯酸［２,５－双－（对甲氧基苯甲酰氧基）苄酯］或聚甲基丙烯酸［２,５－双（对甲氧基苯甲酰氧基）苄酯］,而可能是共聚物．针对这一问题,我们重新设计了合成路线以避免发生上述副反应,成功地合成了丙烯酸或ａ－甲基丙烯酸［２,５－双－（对甲氧基苯甲酰氧基…     

胆甾醇修饰羟基喹啉锌的聚集诱导荧光蓝移

用稳态光谱以及皮秒瞬态荧光光谱研究了新型有机电致发光分子胆甾醇修饰羟基喹啉锌(Zn(ChQ)2)的聚集诱导荧光蓝移性质. 在Zn(ChQ)2的极性溶剂溶液中, 分子激发后会发生从胆甾醇基团向喹啉环的光致电子转移, 转移后形成了“扭转的分子内电荷转移态”作为新的荧光发射态. 而在薄膜态中, 分子由于聚集产生空间位阻, 不能形成新的荧光发射态, 相对于极性溶剂中, 产生聚集荧光增强效应, 荧光发射峰会蓝移, 发射强度会增强. 在薄膜态中, 全波长上的超快荧光衰减说明存在分子间光致能量转移过程.     

铜离子配位调控的TICT荧光化合物的双重荧光发射

设计合成了2个分子内扭转电荷转移(TICT)荧光体(1和2),铜离子的配位作用可开关其双重荧光发射。2在乙腈/水溶液(1∶1,V/V)中的双重荧光发射随着铜离子的加入以类似电子转移机制"开-关"形式猝灭,而1在铜离子与其计量比为1之内的乙腈/水溶液(1∶1,V/V)中,其双重荧光发射随着铜离子的加入逐渐猝灭;在计量比之后其长波长的TICT荧光发射随着铜离子的加入逐渐增强。即1的TICT荧光发射以"开-关-开"的机制被铜离子诱导。同时还获得了铜离子与1形成的配合物的晶体结构以及配合物的荧光性质。1H NMR波谱滴定实验表明荧光体的电荷转移程度是影响TICT发射的主要因素,1是一个新的且其TICT发射可以被铜离子调制为"开-关-开"的TICT荧光体。     

铜离子配位调控的TICT荧光化合物的双重荧光发射（英文）

设计合成了2个分子内扭转电荷转移(TICT)荧光体(1和2),铜离子的配位作用可开关其双重荧光发射。2在乙腈/水溶液(1∶1,V/V)中的双重荧光发射随着铜离子的加入以类似电子转移机制"开-关"形式猝灭,而1在铜离子与其计量比为1之内的乙腈/水溶液(1∶1,V/V)中,其双重荧光发射随着铜离子的加入逐渐猝灭;在计量比之后其长波长的TICT荧光发射随着铜离子的加入逐渐增强。即1的TICT荧光发射以"开-关-开"的机制被铜离子诱导。同时还获得了铜离子与1形成的配合物的晶体结构以及配合物的荧光性质。1H NMR波谱滴定实验表明荧光体的电荷转移程度是影响TICT发射的主要因素,1是一个新的且其TICT发射可以被铜离子调制为"开-关-开"的TICT荧光体。     

不同位置取代的三氰基乙烯基蒽的光谱行为的研究

本文设计合成了两个典型的共轭的电子给体与电子受体(D-A)化合物:2-三氰基乙烯基蒽(2-TCVA)与9-三氰基乙烯基蒽(9-TCVA),通过极性效应,温度效应对它们基态与激发态的光谱行为进行了表征。研究表明:这两个化合物均表现出显著的电荷转移(CT)吸收峰,分子受光激发后,9-TCVA只能在非极性溶剂中产生分子内电荷转移(ICT)态荧光,而2-TCVA在极性与非极性溶剂中都能从ICT态发光。另外,温度效应显示冻结态下,2-TCVA只发射ICT态荧光,而9-TCVA既发射类蒽(anthracene-like)荧光又发射ICT态荧光,造成这一现象的主要原因可能是2-TCVA与9-TCVA分子平面性上的差异而引起分子内电荷转移相互作用不同所致。文中还利用了Bilot-Kawski公式估算了化合物2-TCVA在激发态与基态时偶极矩的差值为18.8D。     

三苯胺衍生物光物理性质的研究

研究了4-醛基-三苯胺(kTA)和4,4′-二醛基-三苯胺(BTA)的光谱性质。由于这两种化合物的共轭体系中既有电子给体(胺基)又有电子受体(醛基),它们在激发态发生分子内扭曲的电荷转移(TICT)。通过对FTA和BTA的荧光发射的溶剂效应、温度效应、粘度效应以及低温77K荧光的研究,发现FTA和BTA在极性溶剂中的荧光发射谱带中包含了光诱导电荷转移(ICT)和TICT(A带)2个组分,而在非极性溶剂中只有ICT带(B带),并讨论环境对TICT态的影响。另外,荧光猝灭方法也证实了这一点。     

1-萘甲酰苯胺和2-萘甲酰苯胺的分子内电荷转移研究

A series of 1-naphthanilides (1) and 2-naphthanilides (2) with varied substituents at the para- or meta-position of anilino phenyl ring were prepared and their absorption and fluorescence spectra in a nonpolar solvent cyclohexane were investigated. An abnormal long wavelength emission assigned to the charge transfer (CT) state was found for all of the prepared naphthanilides in cyclohexane. A linear free energy correlation between the CT emission energies and the Hammett constants of the substituent was found within series 1 and 2. The value of the linear slope with 1 (0.42 eV) was higher than that with 2 (0.32 eV) being close to that of the substituted benzanilides 3 (0.31 eV) The higher slope value suggested higher charge separation extent in the CT state of 1 than that of 2. It was found that the corresponding linear slope of anilino-substituted benzanilides remained unchanged when para-, meta-, ortho-, or ortho, ortho-methyls were introduced into the anilino moiety, which ruled out the possible contribution of the difference in the steric effect and the electron accepting ability of the naphthoyl acceptor in 1 and 2. Compared with the early reported N-substituted-benzoyl-aminonaphthalene derivatives 4 and 5, it was considered that 1-naphthoyl enhanced the charge transfer in 1 and the proximity of its ^1La and ^1Lb states was suggested to be responsible. It was shown that 1- and/or 2-substituted naphthalene cores acting as either electron acceptor (naphthoyl) or electron donor (aminonaphthalene) were different in not only electron accepting (donating) ability but also shaping the charge transfer pathway.     

Intramolecular charge transfer with N-benzoylaminonaphthalenes. 1-Aminonaphthalene versus 2-aminonaphthalene as electron donors

N-(substituted-benzoyl)-1-aminonaphthalenes and N-(substituted-benzoyl)-2-aminonaphthalenes (1-NBAs and 2-NBAs) with varied substituents at the para- or meta-position of benzoyl phenyl ring were prepared to probe the difference between 1-aminonaphthalene (1-AN) and 2-aminonaphthalene (2-AN) as electron donors, using benzanilide-like charge transfer as a probe reaction. An abnormal long-wavelength emission was found for all of the prepared aminonaphthalene derivatives in cyclohexane and was assigned to the CT state by the observation of a substantial red shift with increasing solvent polarity or with increasing electron-withdrawing ability of the substituent. The CT emission energies were found to follow a linear relationship with the Hammett constant of the substituent and the value of the linear slope for 1-NBAs (-0.45 eV) was higher than that of 2-NBAs (-0.35 eV), the latter being close to that of the aniline derivatives (BAs, -0.345 eV). This pointed to a higher extent of charge separation in the CT state of 1-NBAs in which a full charge separation was established by the reduction potential dependence of the CT emission energy with a linear slope of -1.00. The possible contribution of the difference in the steric effect and the electron donating ability of the donors in 1-NBAs and 2-NBAs was ruled out by the observation that the corresponding linear slopes of benzoyl-substituted BAs remained unchanged when para-, meta-, ortho-, or ortho,ortho-methyls were introduced into the aniline moiety. It was therefore concluded that 1-AN enhanced the charge transfer in 1-NBAs and the proximity of its 1La and 1Lb states was suggested to be responsible. Results showed that the charge transfers in 1-NBAs and 2-NBAs were not the same and 1-AN and 2-AN as electron donors were different not only in electron donating ability but in shaping the charge transfer pathway as well.     

Spectroscopic characterization of intramolecular charge transfer of sodium 4-(N,N-dimethylamino)naphthalene-1-sulfonate

In this paper, a new dual fluorescent N,N-dimethylaminonaphthalene derivative, sodium 4-(N,N-dimethylamino)naphthalene-1-sulfonate (SDMDNS), was reported. It was found that SDMDNS emits dual fluorescence only in highly polar solvent water but not in organic solvents such as methanol, dioxane and acetonitrile. Only a single broad band emission at ca. 420 nm was observed in the short wavelength region in organic solvents. The dual fluorescence of SDMDNS in water was found at 423 and 520 nm, respectively. Introduction of organic solvent as ethanol into aqueous solution of SDMDNS leads to blue shift of the long-wavelength emission, and this was evidently supported by introduction of cyclodextrin or surfactant in the aqueous solution. It indicates that a highly polar solvent was required to bring out dual fluorescence; furthermore, the short wavelength fluorescence is emitted from locally excited (LE) state and the long wavelength fluorescence is emitted from charge transfer (CT) state. The pH dependence of the dual fluorescence of SDMDNS demonstrates that the neutral form of the molecular has a higher ratio of CT band intensity to LE band. Temperature effect on the excited state of SDMDNS was also examined and gave stabilization enthalpy (-DeltaH ) of the CT reaction 8.7 kJ mol(-1).     

Photoinduced intramolecular charge transfer of sodium 4-(N,N-dimethylamino) benzenesulfonate

A new dual fluorescent N,N-dimethylaniline derivative, sodium 4-(N,N-dimethylamino)-benzenesulfonate (SDMAS), is reported. In SDMAS, the electron acceptor is linked to the phenyl ring via a sulfur atom at the para-position of the electron donor. It was found that SDMAS emits dual fluorescence only in highly polar solvent water but not in organic solvents such as formamide, methanol and acetonitrile. In organic solvents only a single-band emission at ca.360 nm was observed in the short wavelength region. The dual fluorescence of SDMAS in water was found at 365 and 475 nm, respectively. Introduction of organic solvent such as ethanol, acetonitrile, and 1,4-dioxane into aqueous solution of SDMAS leads to blue-shift and quenching of the long-wavelength emission. Measurements of steady-state and picosecond time-resolved fluorescence indicate that the long wavelength fluorescence is emitted from a charge transfer (CT) state that is populated from the locally excited (LE) state, with the latter giving off the     

A sensitive fluorescent chemosensor for anions based on a styryl-boradiazaindacene framework

Long wavelength emitting, extended conjugation boradiazaindacenes are novel dyes with considerable ICT character. By appending a dipicolylaminylethylamine group, the parent compound was transformed into a fluorescent dye with a strong chelating ability for Zn(II) ions. The zinc complex which has bright orange fluorescence, reversibly signals anions with very large changes in both the absorption and the emission spectra. The remarkable change in the emission intensity is explained in relation to the electron donating capacity of the substituent on the styryl functionality.     

A unique NH-spacer for N-benzamidothiourea based anion sensors. Substituent effect on anion sensing of the ICT dual fluorescent N-(p-dimethylaminobenzamido)-N'-arylthioureas

A series of N-(p-dimethylaminobenzamido)-N'-(substituted-phenyl)thioureas (substituent = p-CH3, H, p-Cl, p-Br, m-Br, m-NO2, and p-NO2) were designed as anion sensors in order to better understand the -NH-spacer via a substituent effect investigation. In these molecules the dual fluorescent intramolecular charge transfer (ICT) fluorophore p-dimethylaminobenzamide as the signal reporter was linked to the anion-binding site, the thiourea moiety, via an N-N single bond. Correlation of the NMR signals of the aromatic and -NH protons with substituents in these molecules indicated that the N-N single bond stopped the ground-state electronic communication between the signal reporter and the anion-binding site. Dual fluorescence was observed in highly polar solvents such as acetonitrile with the former five derivatives. The fact that the CT emission wavelength and the CT to LE emission intensity ratio of the sensors were independent of the substituent existing in the anion-binding moiety suggested that the substituent electronic effect could not be communicated to the CT fluorophore in the excited-state either. Yet in acetonitrile both the CT dual fluorescence and the absorption of the sensors were found to be highly sensitive toward anions. A conformation change around the N-N bond in the sensor molecules was suggested to occur upon anion binding that established the electronic communication between the signal reporter and the anion-binding site. The anion binding constants of the N-(p-dimethylaminobenzamido)thiourea sensors were found higher than those of the corresponding traditional N-phenylthiourea counterparts and the substituent effect on the anion binding constant was much higher than that in the latter. "-NH-" was shown to be a unique spacer that affords N-benzamidothiourea allosteric anion sensors.     

Excited State Intramolecular Proton Transfer in Ethynyl‐Extended Regioisomers of 2‐(2′‐Hydroxyphenyl)benzothiazole: Effects of the Position and Electronic Nature of Substituent Groups

Although the organic dyes based on excited state intramolecular proton transfer (ESIPT) mechanism have attracted significant attention, the structure‐property relationship of ESIPT dyes needs to be further exploited. In this paper, three series of ethynyl‐extended regioisomers of 2‐(2′‐hydroxyphenyl)benzothiazole (HBT), at the 3′‐, 4′‐ and 6‐positions, respectively, have been synthesized. Changes in the absorption and emission spectra were correlated with the position and electronic nature of the substituent groups. Although 4′‐ and 6‐substituted HBT derivatives exhibited absorption bands at longer wavelengths, the keto‐emission of 3′‐substituted HBT derivatives was found at a substantially longer wavelength. The gradual red‐shifted fluorescence emission was found for 3′‐substituted HBT derivatives where the electron‐donating nature of substituent group increased, which was opposite to what was observed for 4′‐ and 6‐substituted HBT derivatives. The results derived from the theoretical calculations were in conformity with the experimental observations. Our study could potentially provide experimental and theoretical basis for designing novel ESIPT dyes that possess unique fluorescent properties.     

Synthesis and Properties of 2‐Phenylbenzoxazole‐Based Luminophores for in situ Photopolymerized Liquid‐Crystal Films

We report the synthesis of a series of blue‐emitting 2‐phenylbenzoxazoles (PBOs) substituted at either the 5‐ or 6‐position of the benzoxazole ring and the para‐position of the phenyl substituent. The thermal and optical properties of the materials can be rationalized in terms of the position of the substituent at the benzoxazole moiety and the electron‐withdrawing or electron‐donating character of the substituents. From the results, we conclude that the combination of an electron‐donating substituent at the benzoxazole fragment and an electron‐withdrawing one at the phenyl fragment has a more marked effect on the electronic properties of the aromatic PBO core than other possibilities. This particular combination gives luminophores that are suitable for optical applications on the basis of their high emission efficiency and photostability. In view of that, oriented films were prepared by in situ polymerization of a mixture of a liquid crystalline direactive matrix containing 5% (w/w) of the luminophore. The films exhibit linearly polarized emission.     

2-(2-巯苯基)苯并噁唑分子内质子转移取代基电子效应的密度泛函理论研究

在B3LYP/6-31G(d,p)和TDB3LYP/6-31++G(d,p)//CIS/6-31G(d,p)水平上研究了2-(2-巯苯基)苯并噁唑及其衍生物基态和激发态分子内质子转移现象,并探讨取代基电子效应对分子内质子转移的影响,研究结果表明,在基态时,硫醇式异构体为优势构象,供电子取代基使基态分子内正向质子转移能垒(烯醇式→酮式)升高;而吸电子取代基则可降低能垒,有利于基态分子内质子转移并有助于硫酮式异构体的稳定.在激发态时,硫酮式结构为优势构象,所研究的2-(2-巯苯基)苯并噁唑化合物及衍生物均可以发生无能垒或低能垒(≤1.5kJ/mol)的激发态分子内质子转移.巯苯基部分是激发态失活的主要活性部分,供电子基团有利于激发态的质子转移,吸电子基团使激发态跃迁困难,不利于激发态的质子转移.     

A novel fluorophore with dual fluorescence: local excited state and photoinduced electron-transfer-promoted charge-transfer state.

Absorption and emission spectra of 9-N,N-dimethylaniline decahydroacridinedione (DMAADD) have been studied in different solvents. The fluorescence spectra of DMAADD are found to exhibit dual emission in aprotic solvents and single emission in protic solvents. The effect of solvent polarity and viscosity on the absorption and emission spectra has also been studied. The fluorescence excitation spectra of DMAADD monitored at both the emission bands are different. The presence of two different conformation of the same molecule in the ground state has lead to two close lying excited states, local excited (LE) and charge transfer (CT), and thereby results in the dual fluorescence of the dye. A CTstate involving the N,N-dimethylaniline group and the decahy droacridinedione chromophore as donor and acceptor, respectively, has been identified as the source of the long wavelength anomalous fluorescence. The experimental studies were supported by ab initio time dependent-density functional theory (TDDFT) calculations performed at the B3LYP/6-31G* level. The molecule possesses photoinduced electron transfer (PET) quenching in the LE state, which is confirmed by the fluorescence lifetime and fluorescent intensity enhancement in the presence of transition metal ions.