取代芳香醛缩芳香胺双席夫碱的合成及谱学性质

采用冰浴合成法合成了一系列席夫碱, 其中4种化合物为首次报道, 研究了其IR, 1H NMR波谱性质, 测定了它们在溶液中以及固态时的紫外吸收光谱和荧光光谱, 探讨了席夫碱类化合物分子结构与光谱之间的关系. 实验结果表明, 水杨醛上的邻羟基是席夫碱类化合物具有荧光性质必要条件; 极性溶剂中, 苯甲醛邻位和对位上OH的存在均可引起双席夫碱结构的变化.     

含席夫碱基团的光致变色螺吡喃化合物的光谱性能和与DNA作用研究

本文合成6种带有席夫碱基团的螺吡喃光致变色化合物,并利用电子吸收光谱、荧光光谱研究了它们的光谱性质以及与DNA的相互作用,考察了不同基团对其作用的影响,对同一化合物研究了在不同pH值、不同离子强度条件下的作用情况,初步探讨了它们与DNA的作用方式.     

取代芳基席夫碱类化合物的室温研磨合成及其紫外可见吸收光谱的研究

研究了取代芳基单席夫碱及双席夫碱的室温研磨固态缩合反应,测定了其在环己烷和甲醇中的紫外可见吸收光谱,并探讨了其电子吸收光谱与分子结构的关系,以及溶剂对电子吸收光谱的影响.     

含溴水杨醛缩对碘苯胺席夫碱的合成、表征及性能研究

以对碘苯胺和5-溴水杨醛、3,5-二溴水杨醛为原料,用液相合成和固相合成两种方法分别合成了光致变色发光化合物5-溴水杨醛缩对碘苯胺席夫碱、3,5-二溴水杨醛缩对碘苯胺席夫碱,利用核磁共振氢谱、质谱、红外光谱和元素分析对两个化合物结构进行了表征,通过紫外-可见吸收光谱、荧光光谱测定了它们的发光性能。结果表明,当用254nm紫外光照射时,两个化合物均表现出良好的光致变色性能;另外,两个化合物在OH-和H+作用下,均表现出良好的发光开关特性。该类多功能席夫碱化合物在信息存储、分子开关和pH检测领域里具有潜在的应用价值。     

二噻吩乙烯基四氮杂卟啉锌配合物的光致变色性质及红外无损读取性质研究

采用“一步法”合成了2,3,7,8,12,13,17,18-八-(2′,4′,5′-三甲基-3′-噻吩)四氮杂卟啉锌配合物,并通过谱学及元素分析对化合物进行了表征。电子吸收光谱及核磁信号的改变表明该化合物在365和730 nm波长的光照射下发生了可逆的光致开、关环反应。通过红外吸收光谱表征了该光致变色二芳基乙烯衍生物在溶液中开、关环前后结构的变化,并采用理论化学计算方法研究了该化合物开、关环异构体的红外吸收振动特性。光致变色异构化过程可以通过红外吸收光谱的变化而识别。关环异构体在1 705 cm     

首例含4,4'-联吡啶和乙酸锌的光致变色化合物

采用一种新方法得到一维配位聚合物[Zn(CH₃COO)₂(4,4'-bipy)]_n(1)。配合物1的晶体结构和荧光性质已经有详细报道,但光致变色性质还没有相关的研究工作发表。通过研究化合物1在光照前后的紫外吸收光谱和顺磁共振谱,表明化合物1具有电子转移光致变色性能。实验结果验证了我们提出的利用非光致变色单元设计电子转移光致变色材料的新方法是有效可行的。     

12-钼磷酸—聚乙烯醇的光电子转移反应

12-钼磷酸—聚乙烯醇体系具有不可逆光致变色的特性。根据X射线光电子能谱、电子自旋共振谱、紫外及可见光谱的测试结果,笔者认为:在PMo_(12)-PVA的光电子转移反应中,PMo_(12)既是氧化剂也是光敏剂。PMo_(12)分子中氧可分成O_p、O_b和O_t三种情况.其中O_t可成为光化学的活性位置,它和PVA羟基上的氧均较易被紫外光激活。激活的0_t边使周围的一个电荷向金属原子(Mo~(Ⅵ))转移,边与PVA羟基上被激活的氧作用,电子就由此羟基上的氧向O_t转移,致使体系中部分PMo_(12)与PVA发生二电子或四电子氧化还原反应,形成Mo(Ⅵ、Ⅴ)配合物而变色,同时,PVA分子的部分羟基及该羟基位的碳上脱氢形成羰基而具有酮结构。此外,从Mo(V)的ESR特征信号随时间变化而减弱,但其吸收光谱的吸光度未变,于是推断该光化学反应过程中尚有Mo(Ⅳ)生成,已由XPS谱证实。     

首例含4, 4'-联吡啶和乙酸锌的光致变色化合物

采用一种新方法得到一维配位聚合物[Zn(CH₃COO)₂(4,4'-bipy)]_n(1)。配合物1的晶体结构和荧光性质已经有详细报道,但光致变色性质还没有相关的研究工作发表。通过研究化合物1在光照前后的紫外吸收光谱和顺磁共振谱,表明化合物1具有电子转移光致变色性能。实验结果验证了我们提出的利用非光致变色单元设计电子转移光致变色材料的新方法是有效可行的。     

水杨醛缩芳胺类席夫碱的光致变色性质

21世纪信息将主要以光为介质进行传输和处理,因此,需要开发出一系列的化合物或材料以用于高密度信息存储、电或光驱动的显示器件、光学运算以及其它非线性光学器件.水杨醛与芳胺衍生物缩合得到的水杨醛缩芳胺类席夫碱的生物活性和光学特性与其组成、结构、取向和分子间相互作用密切相关[1-2],具有光致变色或热致变色性质,受到人们的重视[3-5].因此,本文合成3种非两亲性的水杨醛席夫碱N-(对苯甲酸)-2-羟基苯甲亚胺(简称S1)、N-(对苯甲酸)-2-羟基-5-硝基苯甲亚胺(简称S2)和N-(对苯甲酸)-2-羟基-5-氯苯甲亚胺(简称S3),用紫外-可见光谱分别对其在不同溶剂中进行了光谱性质的研究,结果表明3种水杨醛缩芳胺席夫碱在不同溶剂中均具有光致变色性,其固态具有热致变色性,对光的宏观响应速度较快,为可能实用化提供了参考.     

对醇的消去反应规律的商榷

许多资料这样总结醇的消去反应规律:只有和醇羟基所在碳原子相邻的碳上有氢时,醇才能发生消去反应。笔者认为这种说法欠妥,值得商榷。1反应机理醇在酸的作用下,脱水成烯是经过E1反应机制而完成的,如下图所示:醇羟基接受质子,然后以水的形式离去,原羟基所在碳因而带1个正电荷成为碳正离子,碳正离子的邻碳失1个质子,1对电子转移过来中和碳正离子的正电荷从而形成碳碳双键。如果醇羟基接受质子失水后形成的碳正离子的邻碳上无氢而发生重排后形成的碳正离子的邻碳上有氢,则发生重排形成新的碳正离子,接着邻位碳失去质子而成烯。例如:此反应可表…     

Isomerization dynamics of the 2-phenylazo-1,3-dimethylimidazolium cation photoexcited to the S2 (π, π*) state as studied by transient absorption spectroscopy in the time domain of 10(-13) to 10(3) seconds

Photoinduced isomerization of a novel photochromic cation, [2PA-Mmim](+) (2-phenylazo-1,3-dimethylimidazolium cation), was studied by optical spectroscopic methods. The UV-Vis absorption spectra of the [2PA-Mmim](+) cation show two prominent bands starting around 410 and 520 nm, corresponding to the S(0)-S(2) (π, π*) and S(0)-S(1) (n, π*) transitions, respectively. The photoisomerization mechanism is studied by femtosecond time-resolved transient absorption experiments performed after S(0)-S(2) (π, π*) excitation in several solvents with different viscosity, including ionic liquids. The transient absorption signals at two representative wavelengths were fitted by bi-exponential functions, which yield four decay components. The photoisomerization mechanism is discussed in light of the relaxation schemes available for azobenzene. Only one of the components depends on the solvent viscosity and it changes from 1.2 ps (dichloromethane, 0.4 cP) to 5.6 ps ([Bmim][BF(4)], 93 cP). This component is assigned to a molecule at the S(1) state, which is responsible for the "rotational" isomerization. The weak dependence on the solvent viscosity of this component is explained in terms of local change in the viscosity as a result of local heating due to excess energy released at S(2)-S(1) internal conversion. The other three components of ～0.4, 1.0 and 10 ps are attributed to relaxation processes of the molecule at S(2), S(1) and S(0) states, respectively. The quantum yields for the forward E-Z photoisomerization are ～0.15 after S(2) excitation. The backward Z-E isomerization is slow with a lifetime of 1 hour and an activation energy of 91 kJ mol(-1) through an "inversion" mechanism.     

The effect of solvents on the electronic absorption spectra of mesoionic 1,8,4 thiadiazolium-2-thiolate derivatives

The electronic absorption spectra of 4,5-diphenyl-, 4-pheriyl-5-(4-fluorophenyl)-, 4-phenyl-5-(4-chlorophenyI)-, and 4-phenyl-.5-methyl-1,3,4-lhiadiazolium-2-thiolates have been measured in twenty-one pure solvents, aqueous ethanol and acetone solutions and cyclohexane-chloroform mixtures. They were found to exhibit three characteristic absorption bands; the first in the range 330-440 nm, the second at 260-280 run and the third near 200 ran. The first band was assigned to n → π* transition whereas the other two bands were assigned to π →π* transition. The n → π* transition band was found to be very sensitive, and the polarity of solvents, and some correlations between well-known solvent polarity parameters and the transition energies of these compounds have been presented.     

Photophysical Properties of Pyrazinopsoralen,A New Monofunctional Psoralen*

Abstract— Pyrazinopsoralen (PzPs), a new monofunctional psoralen, has a UV absorption spectrum similar to other psoralens except that it absorbs more strongly in the long-UVA than 8-methoxypsoralen. The solvent effects on the UV absorption and fluorescence emission spectra indicate that the lowest excited singlet state is the π,π* state like other psoralen derivatives. It shows a much lower fluorescence quantum yield (0.0008 in ethanol at room temperature) than the other psoralens as expected by the increased proximity effect (vibronic perturbation) due to close ¹(n,π*) to ¹(π,π*) states. The fluorescence lifetime was 1.05 ns in methylcyclohexane with a single exponential decay, while more than two components were observed in other solvents with the short-lived component being the major (>95%). The triplet state of PzPs could not be detected by phosphorescence, laser flash excitation (T-T absorption) and singlet oxygen formation probably due to very low φ_isc, or short lifetime of the triplet state (τ_T) caused by the fast T₁→ S₀ intersystem crossing.     

Remarkable reactivities of the xanthone ketyl radical in the excited state compared with that in the ground state

The properties and reactivities of the xanthone (Xn) ketyl radical (XnH*) in the doublet excited state (XnH*(D1)) were examined by using two-color two-laser flash photolysis. The absorption and fluorescence of XnH*(D1) were observed for the first time. Several factors governing the deactivation processes of XnH*(D1) such as interaction and reaction with solvent molecules were discussed. The remarkable change of reactivity of XnH*(D1) compared with that in the ground state (XnH*(D0)) was indicated from the experimental results. The rapid halogen abstraction of XnH*(D1) from some halogen donors such as carbon tetrachloride (CCl4) was found to occur. The halogen abstraction occurred more efficiently in the polar solvents than in the nonpolar solvents. It is suggested that the polar solvents promote the spin distribution of XnH*(D1) of the phenyl ring favorable to the halogen abstraction.     

Absorption Spectra and Photoreactivity of Para-aminobenzophenone by Time-dependent Density Functional Theory

The absorption spectral properties of para-aminobenzophenone (p-ABP) were investigated in gas phase and in solution by time-dependent density functional theory. Calculations suggest that the singlet states vary greatly with the solvent polarities. In various polar solvents, including acetonitrile, methanol, ethanol, dimethyl sulfoxide, and dimethyl formamide, the excited S1 states with charge transfer character result from π→π* transitions. However, in nonpolar solvents, cyclohexane, and benzene, the S1 states are the result of n→π* transitions related to local excitation in the carbonyl group. The excited T1 states were calculated to have ππ* character in various solvents. From the variation of the calculated excited states, the band due to π→π* transition undergoes a redshift with an increase in solvent polarity, while the band due to n→π* transition undergoes a blueshift with an increase in solvent polarity. In addition, the triplet yields and the photoreactivities of p-ABP in various solvents are discussed.     

Photophysics of representative ketocyanine dyes: dependence on molecular structure

Spectral properties of a new fluorescent ketocyanine dye have been discussed. The energy of maximum absorption/fluorescence of the dye exhibits bathochromic shift with increasing polarity of the medium. Both dipolarity-polarisability and hydrogen bond donation interaction contribute to solvation of the dye. Study of fluorescence parameters points to existence of different emitting states of the dye for aprotic and protic solvents. While the emitting state is the (1)(π, π*) state for aprotic solvents, fluorescence supposedly take place from a different emitting state involving H-bond formation in the excited state in protic solvents. Fluorescence parameters of the dye have been compared with those for a structurally similar symmetric ketocyanine dye. The faster decay of the dye relative to its symmetric counterpart has been explained as due to an increase of nonradiative decay.     

Electronic properties and ultraviolet absorption and fluorescence spectra of 2-pyridinamine

The u.v. absorption and fluorescence spectra of 2-pyridinamine, its methyl derivatives and its carboxylate salts were measured in various solvents (isooctane, methylcyclohexane and isopentane mixed solvent, ethanol and isooctane mixed solvent, acetic acid and isooctane mixed solvent, and pH adjusted solvent) at room temperature and 77 K. These spectral data were interpretated by the molecular orbital method. From these results it was found that the formation of 2(1H)-pyridinimine with the accompanying 2-pyridinium amine occurs only in the π,π* excited singlet state in the acetic acid and isooctane mixed solvent. On the other hand, the fluorescence spectrum of 2-pyridinamine in the pH ⪢ 11 controlled solution was assigned to the monoanion species, that is, the 2-pyridylamide ion which was formed in the first π,π* excited singlet state.     

Synthesis and Spectral Properties of Novel Water-soluble Indocyanine Dyes as Fluorescent Dyes for Proteins Detection

Two novel water‐soluble indocyanine dyes were synthesized. Their chemical structures were confirmed by ¹H NMR, IR, MS and UV‐vis techniques. The absorptions of the prepared dyes in different solvents were measured. Two dyes exhibited negative solvatochromism, with a blue shift of the absorption and an emission maximum in (bovine serum albumin) protonic solvent relative to non protonic solvent. The fluorescence properties of the dyes in both free state and BSA were investigated. Significant enhancement of the fluorescence intensity for the Dye2 was observed in the presence of BSA. Dye2 could be proposed as fluorescent dyes for BSA detection in aqueous solution.     

Electronic properties and ultraviolet absorption and fluorescence spectra of 2,6-pyridinediamine

The u.v. absorption and fluorescence spectra of 2,6-pyridinediamine and its carboxylate salts were measured in various solvents [isooctane (2,2,4-trimethylpentane), methylcyclohexane and isopentane mixed solvent, ethanol and isooctane mixed solvent, and pH adjusted solvent] at room temperature and 77 K. These spectral data were interpreted by the molecular orbital method. From these results it was found that the formation of 6-amino-2(1H)-pyridinimine through the 2,6-pyridinediamine hydrogen bonded complex with ethanol occurs only in the π,π* excited singlet state in the ethanol and isooctane mixed solvent. On the other hand, the fluorescence spectrum of 2,6-pyridinediamine in the pH > 13 controlled solution was assigned to the monoanion species, that is, the 6-amino-2-pyridylamide ion which was formed in the first π,π* excited singlet state.     

菁染料溶剂效应的光谱研究

本文研究了16种菁染料在18种溶剂中的吸收光谱与激光荧光发射光谱的溶剂效应。发现吸收峰的位移⊿σ_A以及吸收峰与荧光发射峰的能量差(σ_A-ν_F)不仅与溶剂的折射率有关, 而且与其介电常数有关。因而用新函数f(n, e)=((n~2-1)/(2n~2+1))+α((e-1)/(e+2))与F(n, e)=((e-1)/(2e+1))-((n~2-1)/(2n~2+1))代替Bayliss函数f(n)=((n~2-1)/(2n~2+1))可改善结果的线性。还观察到溶剂伋性对染料分子荧光峰位置与强度以及对~1(n, π)及~1(π, π°)能级顺序的影响, 并进行了讨论。