钴(Ⅲ)的联吡啶类混配配合物的合成,表征及其与DNA键合的光谱研究

合成了两种新的钴多吡啶类混配配合物。通过元素分析 ,红外 ,紫外 ,核磁方法对其进行表征 ,应用吸收及发射光谱 ,DNA熔点技术 ,循环伏安法 ,研究了其与小牛胸腺DNA的作用。结果显示 ,混配配合物与DNA作用时 ,使紫外吸收明显减色 ,荧光显著增强 ,DNA熔点升高。循环伏安法研究表明 ,配合物仅有还原峰 ,与DNA作用后 ,还原峰电流明显下降。这些结果证明配合物与DNA存在插入结合 ,[Fe(CN) 6 ]4 - 猝灭实验也支持这一结论。峰电位有位移 ,说明配合物与DNA分子中带负电荷的磷酸基团可能存在静电结合 ,进而计算得到配合物与DNA的键合常数分别为 1 8× 10 4 ,4 37× 10 4 。     

Estimation of Ground-State and Singlet Excited-State Dipole Moments of Substituted Schiff Bases Containing Oxazolidin-2-one Moiety through Solvatochromic Methods

Absorption and fluorescence studies on novel Schiff bases (E)-4-(4-(4-nitro benzylideneamino)benzyl)oxazolidin-2-one (NBOA) and (E)-4-(4-(4-chlorobenzylidene amino)benzyl)oxazolidin-2-one (CBOA) were recorded in a series of twelve solvents upon increasing polarity at room temperature. Large Stokes shift indicates bathochromic fluorescence band for both the molecules. The photoluminescence properties of Schiff bases containing electron withdrawing and donating substituents were analyzed. Intramolecular charge transfer behavior can be studied based on the influence of different substituents in Schiff bases. Changes in position and intensity of absorption and fluorescence spectra are responsible for the stabilization of singlet excited-states of Schiff base molecules with different substituents, in polar solvents. This is attributed to the Intramolecular charge transfer (ICT) mechanism. In case of electron donating (?Cl) substituent, ICT contributes largely to positive solvatochromism when compared to electron withdrawing (?NO₂) substituent. Ground-state and singlet excited-state dipole moments of NBOA and CBOA were calculated experimentally using solvent polarity function approaches given by Lippert–Mataga, Bakhshiev, Kawskii-Chamma-Viallet and Reichardt. Due to considerable π- electron density redistribution, singlet excited-state dipole moment was found to be greater than ground-state dipole moment. Ground-state dipole moment value which was determined by quantum chemical method was used to estimate excited-state dipole moment using solvatochromic correlations. Kamlet-Abboud-Taft and Catalan multiple linear regression approaches were used to study non-specific solute-solvent interaction and hydrogen bonding interactions in detail. Optimized geometry and HOMO-LUMO energies of NBOA and CBOA have been determined by DFT and TD-DFT/PCM (B3LYP/6-311G (d, p)). Mulliken charges and molecular electrostatic potential have also been evaluated from DFT calculations.     

取代基对2-(2-羟基苯基)苯并噻唑分子内氢键及质子转移的影响:密度泛函理论研究

运用密度泛函(DFT)和含时密度泛函(TD DFT)理论方法研究了在2-(2-羟基苯基)苯并噻唑(HBT)苯环羟基的邻位或对位分别引入羟基和醛基后的衍生物分子内质子转移过程,考察了取代基的电子效应及取代位置对分子内氢键和质子转移反应的影响,模拟计算了各分子的IR振动光谱和电子光谱.研究发现,HBT及其衍生物分子可以形成分子内氢键,且激发态时氢键增强.基态时以醇式构型稳定存在,激发态时酮式结构为优势构象.分子的最大吸收峰和发射峰主要源于电子从前线分子轨道HOMO到LUMO之间的跃迁.基态分子内质子转移需要越过较高的能垒因而难以发生,而激发态时只需越过较低能垒就很容易发生激发态分子内质子转移.取代基的电子效应和取代位置对HBT分子氢键强度、互变异构体的相对稳定性、电子光谱及质子转移反应的能垒均有一定影响.     

基于紫外吸收光谱的酚类衍生物含量检测研究

研究了水溶液条件下苯酚及其酚类衍生物的紫外吸收光谱。2位、3位和4位引入取代基可使酚类化合物的最大吸收波长λ_max发生红移,摩尔消光系数ε_max明显提高。不同取代位置对λ_max和ε_max的影响程度不同。与2位和3位相比,4位取代能使最大吸收波长λ_max发生较大红移,摩尔消光系数ε_max增加较大,这是因为4位取代基能与苯环形成更多共轭结构的缘故。对硝基酚的λ_max和ε_max的特性研究表明—NO₂是酚类化合物较好的助色基。由此,建立了快速测定酚类化合物含量的紫外分光光度法,并选择测定了ε_max>10 000的四种酚类化合物在土壤中的吸附率。结果显示,酚类化合物在质地粘重的土壤中吸附率较大;高浓度的无机盐溶液能够提高酚类化合物在土壤中的吸附率。     

A DFT/TD-DFT study of effect of different substituent on ESIPT fluorescence features of 2-(2'-hydroxyphenyl)-4-chloro- methylthiazole derivatives

Based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer (ESIPT) process and photophysical properties of 2-(2'-hydroxyphenyl)-4-chloromethylthiazole (HCT) are studied. The electron-donating group (CH₃, OH) and electron-withdrawing group (CF₃, CHO) are introduced to analyze the changes of intramolecular H-bond, the frontier molecular orbitals, the absorption/fluorescence spectra, and the energy barrier of ESIPT process. The calculation results indicate that electron-donating group strengthens the intramolecular H-bond in the S₁ state, and leads to an easier ESIPT process. The electron-withdrawing group weakens the corresponding H-bond and makes ESIPT process a little harder. Different substituents also affect the photophysical properties of HCT. The electron-withdrawing group (CF₃, CHO) has a little effect on electronic spectra. The electron-donating group (CH₃, OH) red-shifts both the absorption and fluorescence emission peaks of HCT, respectively, which causes the Stokes shift to increase.     

Theoretical insight into the substituent effects on linear and nonlinear optical properties of azobenzene‐based chromophores

The linear and nonlinear optical properties of 4 kinds of experimental synthesized azobenzene‐based chromophores were investigated by different density functional theories (DFTs) upon the electronic structures. The structure‐property relationship was studied on each single molecule either in the gas phase or in diethylether and tetrahydrofuran (THF) solutions. The substituent effect on optical properties was revealed by checking the positions of substituent groups, and the influence of dynamic perturbation to the optical nonlinearity was investigated by simulating the experimental excitation. The results revealed that the substituent in the meta‐position of the azobenzene group affects the optical properties more significantly than that in the ortho‐position, which is in agreement with the experimental finding. The modulation of molecular hyperpolarizability of bridge‐substituted azobenzene derived by dynamic perturbation is not recommended because of the reduced dynamic hyperpolarizability relative to the static one. The different functions of the DFT method hardly affect the calculated results, while solvent effects of diethylether and THF solutions are significant on the optical properties, especially for optical nonlinearity. The information derived from the single chromophore may be helpful in the design and preparation of high‐performance nonlinear optical materials in further.     

1,5‐electrocyclization versus 1,5‐proton shift in imidazolium allylides and 2‐phospha‐allylides: a DFT investigation

The competitive 1,5‐electrocyclization versus intramolecular 1,5‐proton shift in imidazolium allylides and imidazolium 2‐phosphaallylides has been investigated theoretically at the DFT (B3LYP/6‐311 + +G**//B3LYP/6‐31G**) level. 1,5‐Electrocyclization follows pericyclic mechanism and its activation barrier is lower than that for the pseudopericyclic mechanism by ～5–6 kcal mol^?1. The activation barriers for 1,5‐electrocyclization of imidazolium 2‐phosphaallylides are found to be smaller than those for their nonphosphorus analogues by ～3–5 kcal mol^?1. There appears to be a good correlation between the activation barrier for intramolecular 1,5‐proton shift and the density of the negative charge at C8, except for the ylides having fluorine substituent at this position ( 7b and 8b ). The presence of fluorine atom reduces the density of the negative charge at C8 (in 7b it becomes positively charged) and thus raises the activation barrier. The ylides 7f and 8f having CF₃ group at C8, in preference to the 1,5‐proton shift, follow an alternative route leading to different carbenes which is accompanied by the loss of HF. The carbenes Pr _{7 , 8b – e} resulting from intramolecular 1,5‐proton shift have a strong tendency to undergo intramolecular S_N2 type reaction, the activation barrier being 7–28 kcal mol^?1. Copyright © 2011 John Wiley & Sons, Ltd.     

溶剂极性对1，5-二羟基蒽醌分子双质子转移过程的影响

具有激发态分子内双质子转移特性的分子在荧光传感器、激光材料、生物分子探针等领域具有广泛的应用. 羟基蒽醌作为蒽醌类化合物是自然界中广泛存在且具有质子转移特性的次级代谢物,其衍生物已被广泛研究并成功应用于染料、免疫增强和抗癌药物. 近年来,1,5-二羟基蒽醌(1,5-DHAQ)作为一种具有两个分子内氢键的羟基蒽醌衍生物受到了广泛的关注. 本文采用飞秒瞬态吸收光谱结合含时密度泛函理论方法研究了溶剂极性对1,5-DHAQ分子激发态分子内双质子转移过程的影响. 1,5-DHAQ分子在甲苯、四氢呋喃和乙腈溶剂中的稳态荧光光谱表明,溶剂极性的改变对1,5-DHAQ的荧光峰位置产生了影响. 瞬态吸收光谱表明,溶剂极性的增大加快了质子转移的速率. 超快动力学拟合结果表明,溶剂极性的增大有助于加快1,5-DHAQ分子中的激发态分子内双质子转移过程. 此外,通过理论计算得到的势能曲线分析表明质子转移的能垒随着溶剂极性的增加而逐渐减小,从而促进1,5-DHAQ分子激发态分子内双质子转移过程的发生,这进一步验证和解释了实验结果. 本工作有助于开发和合成更稳定、高效的羟基蒽醌衍生物.     

基于密度泛函理论下多肽光谱性质研究

多肽类物质在生物医药等领域是一种重要的生物大分子,而紫外-可见吸收光谱和荧光光谱是研究生物分子精细结构的重要手段。采用密度泛函理论（DFT/RI）计算了生长激素释放肽（GHRP-6）和催产素（Oxytocin）两种多肽的结构模型和分子前线轨道;在含时密度泛函理论（TDDFT）的基础上,引入了TDA等近似,建立了多肽类物质的紫外-可见吸收光谱和荧光光谱的理论模型。结果表明,实验测得到GHRP-6的紫外-可见吸收光谱最大吸收波长为279 nm,计算得到的最大吸收波长为282 nm,误差为3 nm,误差百分比约为1%;Oxytocin紫外-可见吸收光谱的实验值为275 nm,计算值为269 nm,误差百分比约为2%。GHRP-6荧光光谱计算值为368 nm,实验值为360 nm,误差百分比约为2%;Oxytocin荧光光谱计算值为305 nm,实验值为312 nm,误差百分比约为2%。GHRP-6产生荧光的发射波长与色氨酸产生的荧光波长范围相近,说明GHRP-6产生荧光的主要贡献为色氨酸残基上的π→π*轨道跃迁,Oxytocin荧光峰位置与酪氨酸产生的荧光波长范围相近,Oxytocin产生荧光的主要贡献为酪氨酸残基上的π→π*轨道跃迁。根据该模型计算得到的光谱与实验结果吻合度较高,表明该模型能够准确计算多肽类物质紫外-可见吸收光谱和荧光光谱,为实验提供可靠的理论依据。     

水体中溶解有机物的荧光光谱特性分析

以355 nm激光为激发光源,在实验室中利用激光诱导荧光(LIF)方法对不同水体中溶解有机物(DOM)的荧光光谱进行了测量,并以最小二乘法-高斯拟合对水体荧光光谱进行了拟合,解卷积得出了水喇曼散射谱及DOM的荧光光谱.在改变激发光脉冲强度的条件下,以一定浓度腐殖酸溶液为测量样品分析了DOM的荧光饱和特性.结果表明,随着激发光功率密度的增加,水喇曼散射强度线性增加,而DOM的荧光强度随着激发光功率密度的增加先是线性增加,此时归一化荧光强度为一恒定值.当激发光功率密度大于55 mW/cm2时, 荧光强度增加缓慢,归一化荧光强度则逐渐降低.研究发现,在有机物浓度较高时,出现了激发态分子间的单重态-单重态猝灭,并且在低浓度情况下,随着有机物浓度的增加,出现了有机物荧光峰值强度位置的红移并伴有波形的展宽.     

SiO2纳米颗粒对R6G-乙醇溶液荧光光谱影响

在3×10－4M和1×10－4M浓度的R6G-乙醇溶液中分别掺杂了8个不同浓度的SiO2纳米颗粒（107～1012 个/mL）.研究了SiO2纳米颗粒（100 nm）对若丹明6G（R6G）荧光光谱的影响,结果表明:n1～n4(1012～1010个/mL)浓度掺杂的SiO2纳米颗粒在549 nm处的有很好的荧光增强作用,对570 nm处的荧光峰有明显的粹灭作用|n5～n8(109~107个/mL)浓度掺杂的SiO2纳米颗粒在549 nm处没有明显的荧光增强作用,但对570 nm处的荧光峰有增强作用,荧光增强因子可达10%~20%.荧光增强与粹灭的原因在于纳米颗粒对荧光的散射作用和R6G无荧光H-型二聚体或荧光J-型二聚体的形成.     

双酰胺配体铕和铽混合固态配合物的光谱研究

在氯仿和乙酸乙酯溶液中合成了以1,6-二[(2’-苄胺甲酰基)苯甲氧基]己烷(L)为配体的硝酸铕和硝酸铽配合物,以及不同摩尔比的铕和铽的共沉淀配合物,又按不同的摩尔比将单一的硝酸铕和硝酸铽配合物通过研磨混合,得到混合固态的铕铽配合物。通过元素分析、红外光谱、紫外光谱、XPS 光电子能谱对配合物进行了表征,结果表明：单一稀土硝酸盐与配体形成的是2∶3型的配合物;所有的配合物都具有相似的配位结构;与单一稀土配合物相比,相同摩尔比的混合配合物的紫外吸收有所降低;混合配合物中发生了一定的化学键合作用,电子结合能有变化。通过荧光光谱对这些配合物的荧光性质进行了详细的研究, 表明与单一的铕和铽配合物相比,两种混合固态配合物无论是荧光发射峰位还是荧光强度均发生了明显变化,铽对铕的荧光强度有很强的敏化作用,铕对铽的荧光强度有猝灭作用。在紫外灯的照射下,共沉淀配合物的荧光颜色随着摩尔比的变化呈现有规律的变化。     

Effects of high pressure on the Raman and fluorescence emission spectra of two novel 1,3,4-oxadiazole derivatives

The effects of pressure on the fluorescence emission and Raman spectra of 1,4-bis[（4-methyloxyphenyl）-1,3,4-oxadiazolyl]- 2,5-bisheptyloxyphenylene （OXD-2） and on the fluorescence emission spectra of 1,4-bis[（4-methylphenyl）- 1,3,4-oxadiazolyl]phenylene （OXD-1） are investigated using a diamond anvil cell. With the increase of pressure, the intensity of the fluorescence emission increases and reaches maxima at 13GPa for OXD-1 and at 9.6GPa for OXD-2. The effect of pressure on the peak position of the emission shows a similar trend, red shift with the increase of pressure. But at higher pressures, the intensity of emission drops down dramatically. The Raman spectra of OXD-2 indicate that there appears a structural change at ca 3GPa.     

罗丹明6G在醇溶液中的荧光频移特性分析

罗丹明6G在甲醇、乙醇、乙二醇溶液中均发出较强的荧光。当醇溶液浓度为33.3%时,基本不存在频移现象。当醇溶液浓度为99.7%时,荧光峰发生蓝移或红移,分析认为该频移是由罗丹明6G和醇类物质分子相互作用(如氢键、静电吸引)导致激发态能量升高、荧光峰蓝移,与醇类物质分子中羟基OH的孤对电子跃迁导致荧光能量降低、荧光峰红移,这两种因素相互竞争的结果,且在高浓度醇溶液中,羟基OH数量越多,红移越明显。     

退火处理对YMnO3薄膜的结构和荧光性能的影响

室温下,采用脉冲激光沉积方法在Si(100)衬底上制备了YMnO3薄膜,并对其进行了不同温度的退火处理。采用X射线衍射和荧光光谱分析方法对薄膜的结构和荧光特性进行了研究。结果表明:通过退火处理,可以得到正交相和六方相共存的多晶态YMnO3薄膜,并且随着退火温度的升高,两相的比例发生变化,由正交相为主转变为六方相为主。YMnO3薄膜样品的荧光发射峰集中在波长430～620nm范围内,可能是由Mn3 离子从5T2到5E之间的能级跃迁所引起的。其荧光强度随着退火温度的升高逐渐增强,但峰位基本保持不变,说明薄膜结构的改变对Mn3 离子的能级跃迁几率有明显的影响,对能级位置的影响不大;而且荧光光谱还显示在同一薄膜中各个荧光峰的相对强度随着退火温度的变化不大。     

Investigation on the conformational changes of bovine serum albumin in a wide pH range from 2 to 12

The conformation of bovine serum albumin largely depends on its microenvironment pH and affects its physical functions and applications. In this study, we investigated the effects of pH (wide range 2–12) on the conformation of bovine serum albumin based on spectroscopic signals by various spectroscopic means including fluorescence, synchronous fluorescence, resonance light scattering, UV-visible absorption, and circular dichroism. The changes in spectroscopic signals, such as peak position and intensity, showed that the structure of bovine serum albumin varied significantly with pH. The conformation of bovine serum albumin was compact at pH 6–7, as indicated by the largest peak position values and peak intensities in the fluorescence, synchronous fluorescence, and RLS spectra. The structure of bovine serum albumin became loose in the acidic or alkaline environment, as indicated by the decreased peak position values and peak intensities. The microenvironment of the amino acid residues of bovine serum albumin also varied with pH, as indicated by the changing peak position values. At pH 7, the hydrophobicity of the tyrosine and tryptophan residues was the weakest, as indicated by the minimum synchronous fluorescence signals. In addition, the secondary structure of bovine serum albumin, especially α-helix, varied with pH. The content of α-helix reached the maximum value of 68% at pH 6–8, whereas it decreased in the acidic or alkaline environment. The study provides valuable details for studying the physiological function and applications of serum albumins.     

酮类甲醛荧光探针的合成及其光学性质

设计合成了两种化合物4-氨基4-（4-甲氧基苯基）-3-丁烯-2-酮（1b）和4-氨基-4-（1,3-亚甲二氧基苯基-5-基）-3-丁烯-2-酮（2b）,测试了其在不同甲醛含量下的紫外吸收光谱及单光子荧光光谱。当含有100 μmol/L和5 μmol/L的甲醛时,化合物1b和2b的紫外吸收峰强度分别达到其最大值。在单光子荧光方面,化合物1b的荧光发射峰位置在384 nm,与紫外吸收峰相比红移50 nm。化合物2b的荧光发射峰呈现出双峰形状,其发射峰位置分别在384 nm及411 nm左右。当加入15 μmol/L的甲醛时,化合物2b的411 nm处的荧光发射峰明显增强,两峰的重叠程度降低,可作为检测甲醛的特征变化。以上数据表明,化合物1b和2b不仅能够对微量甲醛产生响应,也可作为一种理想平台为更进一步拓宽化合物1b和2b在监测生物体系中甲醛荧光生物成像上的应用奠定理论基础。     

Spectral Properties of Y-Shaped Donor-Acceptor Push-Pull Imidazole-based Fluorophores: Comparison between Solution and Polymer Matrices

The spectral properties of a novel type of Y-shaped fluorophores consisting of an imidazole ring end-capped with two electron-donating N,N-dimethylaminophenyl groups at positions C4 and C5 and one electron-withdrawing cyano group on the imidazole moiety at position C2 were examined. The π-linker separating the 4,5-bis[4-(N,N-dimethylamino)phenyl]-1H-imidazole donor moiety and the cyano group comprises 1,4-phenylene (1), (E)-phenylethenyl (2), (E)-phenylbuta-1,3-dienyl (3), biphenyl (4), (E)-phenylethenylphenyl (5) and phenylethynylphenyl (6) conjugated paths. The absorption and fluorescence spectra were obtained in toluene, dichloromethane, acetonitrile and methanol and in polymer matrices such as polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(vinylchloride) (PVC). The most intense absorption bands of fluorophores 1-6 were observed within the range of 283 to 330?nm. Less intense but longer-wavelength absorption bands designated as charge-transfer bands were observed at approximately 380-430?nm depending on the medium. The fluorophores exhibited strong fluorescence in the visible region with a Stokes shift of approximately 4300-5800?cm(-1) in non-polar toluene and polystyrene, whereas very low intensity of fluorescence was observed with a Stokes shift in the 6500-7800?cm(-1) region in polar methanol and acetonitrile. The large Stokes shift indicates a large difference in the spatial arrangement of the chromophore in the absorbing and emitting states. A relatively intense fluorescence (quantum yields of 0.12-0.69) was observed only for derivative 1 in all media except methanol. The fluorophores doped in matrices yielded more intense fluorescence compared with the fluorescence in liquid media. The use of solid polymer matrices lowers the probability of forming non-emissive excited states. The fluorescence lifetimes were short (1-4?ns) for all of the fluorophores in solvents and in polymer matrices.     

Fluorescent Properties of Pentamethine Cyanine Dyes with Cyclopentene and Cyclohexene Group in Presence of Biological Molecules

A series of pentamethine cyanine dyes with cyclohexene or cyclopentene group in polymethyne chain, assumed as DNA groove-binders, were studied as fluorescent probes for nucleic acids as well as for native and denatured proteins. It was revealed that the presence of methyl or dimethyl substituent in 5 position of the cyclohexene group hinders the formation of dye–DNA fluorescent complex, while the methyl substituent in 2 position leads to the increasing of the dye–DNA complex fluorescence intensity. The dyes SL-251, SL-1041, and SL-1046 containing methyl group in the 2 position of the cyclic group, are reported as bright DNA-sensitive dyes. The study of the dyes DNA-binding specificity demonstrated significant AT-preference that points to the groove-binding interaction mode. At the same time, the dyes SL-251, SL-377, and SL-957 with the 2-methyl substituted cyclohexene group were shown to be sensitive fluorescent dyes both for nonspecific (in SDS presence) proteins detection and for native BSA.     

Photophysical Studies on the Interaction of Formamide and Alkyl Substituted Amides with Photoinduced Electron Transfer (PET) Based Acridinedione Dyes in Water

Interaction of photoinduced electron transfer (PET) based acridinedione dye (ADR 1) with amides like formamide, acetamide and dimethylformamide (DMF) were investigated by fluorescence spectral techniques. A fluorescence enhancement accompanied with a blue shift in the emission maximum was observed on the addition of amides to ADR 1 dye, which possess C₆H₄(p-OCH₃) in the 9th position of the basic acridinedione ring. The extent of fluorescence enhancement and the blue shift in the emission maximum of ADR 1 dye is of the order of DMF > acetamide > formamide. DMF, which is more hydrophobic and less polar, results in a higher extent of fluorescence enhancement and a larger shift in the emission maximum towards the blue region. On the addition of amides, the ADR 1 dye prefers to orient towards a more hydrophobic phase surrounded by more number of amide molecules. The fluorescence enhancement of ADR 1 dye is attributed to the suppression of PET process occurring through space. The influence of the hydrophobic nature and the polarity of the amides on the excited state properties of acridinedione dyes are elucidated by steady-state and time resolved fluorescence measurements.