1,8-萘酰亚胺类衍生物的结构及紫外-可见吸收光谱

用密度泛函方法(DFT)优化了一系列1,8-萘酰亚胺衍生物, 用含时密度泛函(TDDFT)和导体极化连续模型(CPCM)计算了它们在气相、环己烷和二氯甲烷溶剂条件下的紫外可见吸收光谱. 计算结果表明, 优化的几何结构和X射线晶体结构数据吻合较好. 萘环4和5位胺基上取代基团(氢基、甲基、苯基和萘基)的变化使得它与萘酰亚胺部分的连接键长(N—C)变长、电荷转移增强、带隙降低. 溶剂化显色效应和前线轨道电子云一致表明此类物质的最大吸收峰对应π-π*跃迁. 异构体A中的分子内电荷转移增大和带隙的降低是它的紫外吸收光谱最大吸收峰比异构体B的发生红移的主要原因.     

含嘧啶与芴结构单元共聚物的合成及性能

通过Suzuki偶联反应将2,7-双(4,4,5,5-四甲基-1,3,2-二氧杂硼烷-2-基)-9,9-二辛基芴与2-氨基-4,6-二碘嘧啶共聚,得到了一种新型共聚物聚(2-胺基嘧啶-9,9-二辛基芴)。采用红外光谱、核磁共振氢谱、紫外-可见吸收光谱、荧光光谱、循环伏安、热重分析等测试方法对共聚物进行了性能分析。结果表明:该共聚物有一定的热稳定性,在氯仿溶液中的激发峰位于390 nm,462nm和496 nm处出现了2个发射峰并在最大吸收波长下发射黄绿色荧光。共聚物的氯仿溶液存在酸致变色现象,加入CF_3COOH后,共聚物在390 nm处的吸收峰强度不断降低,并且在433 nm左右出现了一个新的吸收峰,溶液由淡黄色转变为绿色,UV-Vis吸收峰发生红移。     

亚甲基蓝溶液中分子二聚现象的压致增强研究

通过原位高压紫外-可见吸收光谱研究了2种溶剂(水溶液和体积比为4∶1的甲醇-乙醇混合溶液)中亚甲基蓝(MB)分子聚集平衡状态的变化.采用金刚石对顶砧原位高压实验装置,在不同压力下测量亚甲基蓝溶液的吸收光谱,最高实验压力分别达到0.8 GPa(水溶液)和8.7 GPa(甲醇-乙醇溶液).结果表明,随着压力的上升,亚甲基蓝溶液中单体分子和二聚体的吸收峰强度比不断下降,说明高压可以促进二聚体的形成,使亚甲基蓝溶液中分子的单体-二聚体动态平衡过程向二聚体方向移动.卸压后,亚甲基蓝溶液吸收光谱的强度降低,但吸收峰的强度比及峰位恢复到加压前的状态,表明高压下分子聚集平衡状态的变化是可逆的.     

β-榄香烯及其银离子配合物的紫外及圆二色光谱研究

测定β-榄香烯及其银离子配合物的紫外吸收光谱及圆二色性,研究络合前后光谱特征峰的变化,并用分子轨道理论对β-榄香烯银离子的配位键的形成作出解释.结果表明:β-榄香烯与银离子能形成π配合物,形成配位化合物后,其紫外吸收光谱特征吸收峰红移(213 nm→252 nm)及圆二色性发生变化.从紫外光谱来看,β-榄香烯与硝酸银形成π配合物.     

细菌视紫红质多重突变体结构变化及其中间态的寿命

采用基因定点突变的方法, 构建了细菌视紫红质(Bacteriorhodopsin, BR)的3种突变体蛋白, 即单突变体BRE194Q、三突变体BRI119T/T121S/A126T和四突变体BRI119T/T121S/A126T/E194Q. 测定了突变体和野生型BR在水溶液和聚乙烯醇(PVA)膜中的紫外-可见吸收光谱和拉曼光谱, 采用显微视频录像技术记录了PVA膜中野生型和3个突变体样品的M态寿命. 与野生型BR相比较, 在水溶液中, 单突变体的可见吸收光谱的最大吸收峰发生了轻微红移, 三突变体和四突变体的最大吸收峰则分别发生了11.0和12.0 nm的明显蓝移. 在PVA膜中, 3个突变体BR的可见吸收光谱的最大吸收峰均发生蓝移, 四突变体BR的最大吸收峰为557 nm, 蓝移达15.0 nm. 四突变体BR在水溶液中的共振拉曼光谱不仅表现有与M态特征相关的1567和1573 cm-1谱带, 还有L态特征带1334 cm-1及N态特征带1200, 1328, 1530和1549 cm-1. 在PVA膜中的样品与在水溶液中的比较, 四突变体共振拉曼光谱的1334和1549 cm-1带消失, 同时1187 cm-1带的强度下降. 显微视频录像技术记录的PVA膜中样品的M态寿命表明, 野生型BR的M态寿命最短, 单突变体的M态寿命小于1.0 s, 三突变体的寿命为3.0 s, 四突变体的寿命为2.0 s.     

9-戊基咔唑-3,6-双-(炔苯基-4-甲酸乙酯)的合成与双光子特性研究

采用钯催化的碳碳偶合反应合成了9-戊基咔唑-3,6-双-(炔苯基-4-甲酸乙酯)(I).进一步研究了化合物I在四氢呋喃和40%四氢呋喃水溶液中的光物理性质,结果显示,化合物I在40%四氢呋喃水溶液中的紫外吸收峰位置与其四氢呋喃溶液相比没有发生明显移动,它在40%四氢呋喃水溶液中的单光子荧光发射峰出现在453 nm,较其在四氢呋喃溶液的发射有42 nm红移,其荧光量子效率为0.44.用波长为660 nm飞秒激光激发时,化合物I在40%四氢呋喃水溶液中的双光子荧光发射最大峰红移至489 nm,其双光子吸收截面值为251GM,比其在四氢呋喃溶液中的截面(151 GM)增强了60%.     

模仿绿色荧光蛋白的荧光聚合物的合成和光学性质研究

受绿色荧光蛋白(GFP)荧光增强原理启发,采用开环聚合制备了两亲性聚乙二醇-生色团-聚己内酯(PEG-c-PCL)嵌段聚合物.通过核磁共振氢谱和碳谱(1H-,13C-NMR)、傅立叶变换红外光谱(FTIR)、凝胶渗透色谱(GPC)和紫外可见吸收光谱(UV-Vis)等证明其结构和性质.生色团和聚合物有相似的紫外吸收光谱,且最大吸收峰都在371 nm.荧光发射光谱表明,生色团的发射峰在427 nm,但聚合物的荧光发射峰出现了6 nm的红移,这是高分子化引起的结果.透射电镜(TEM)和动态光散射(DLS)证明了该两亲性嵌段聚合物能够组装成为纳米粒子.当聚合物组装成纳米粒子后,荧光强度增大了55倍,并且荧光发射峰出现了14 nm的红移,这些现象可归结于荧光生色团自由旋转的限制和组装导致的相互作用增强.     

一类近红外电致发光芴基共聚物的合成和性能研究

基于9,9-二辛基芴与窄带隙单体5,7-二(2-噻吩基)噻[3,4-b]并[1,4]二嗪(DTP),通过Suzuki偶合反应,合成了一系列无规窄带隙的芴基共聚物(PFO-DTP),并对它们的紫外-可见吸收光谱、光致发光和电致发光性能进行了初步研究.共聚物在380 nm和632 nm处有两个明显的吸收峰,其中632 nm处的吸收随着共聚物中窄带隙单体(DTP)含量的增加而加强,最大电致发光峰随着共聚物中窄带隙单体(DTP)含量的增加,从752nm红移到了781 nm.同时与其同分异构体4,7-二(2-噻吩基)苯并噻二唑(DBT)与芴的共聚物PFO-DBT相比,该类聚合物的吸收红移,与近地太阳光谱更为匹配.     

香豆素席夫碱的Zn~(2+)识别研究

本文采用5-氯水杨醛与3-氨基-7-羟基香豆素反应,合成了一种新型的香豆素席夫碱化合物3-[(5-氯-2-羟基-苯亚甲基)-氨基]-7-羟基香豆素(CHB),并采用核磁共振谱、红外光谱和元素分析对合成产物进行了表征。在CHB的DMF溶液中加入Zn~(2+)后,溶液颜色由无色迅速变为橙黄色,紫外-可见吸收光谱最大吸收峰从380nm红移至480nm,而且该分子探针在580nm处的荧光强度显著增强,可通过肉眼观察到其在365nm紫外灯下发出的荧光,而其它离子加入后荧光变化微弱或没有变化,表明该分子探针对Zn~(2+)的选择性较高。吸收光谱的变化表明CHB与Zn~(2+)形成了新的配合物,采用Benesi-Hilderbrand方程计算出两者之间以1∶1配位。     

聚合位点对齐聚乙烯基噻吩光谱的影响

利用密度泛函理论PBE0方法,在6-31G基组水平上,对12种采用不同聚合位点的乙烯基噻吩二聚体分子进行了全优化,得到分子的紫外-可见吸收光谱.探讨了聚合位点对齐聚乙烯基噻吩吸收光谱、电子亲和势、电离能和重组能的影响,并研究了聚合度对乙烯基噻吩齐聚物吸收光谱的影响.计算结果表明:采用邻位聚合的乙烯基噻吩二聚体的能隙最小,电离能EIP最小,电子亲和势EEA最高,最大吸收波长较大,吸收强度大,λmax=377.33nm,f=1.0242.随着聚合度的增加,齐聚乙烯基噻吩的吸收光谱发生红移,吸收峰变宽,吸光度增大.十六聚体的最大吸收范围为500~1200nm,最大吸收波长为801.28nm时吸收值为7.003×105L·mol~(-1)·cm~(-1).     

Specific surface chemical interactions between hydrous ferric oxide and iron-reducing bacteria determined using pK(a) spectra

A modified regularized least squares pK(a) spectrum approach is applied to determine disassociation constants and proton binding site concentrations on bacteria, hydrous ferric oxide (HFO), and bacteria/HFO composite surfaces. This involves fitting experimental acid-base titration data to a continuous binding site model for a chemically heterogeneous surface with a variety of reactive groups yielding a pK(a) spectrum. The modified parameter fitting method optimizes simultaneously for both smoothness of the pK(a) spectrum and goodness of fit, whereas other methods optimize for goodness of fit given a fixed smoothness factor. Uncertainty estimates in pK(a) spectra were made by taking the mean and standard deviation of the spectra from replicate titration data. Titration of Shewanella putrefaciens strain CN32, a facultative iron-reducing bacterial species, demonstrate five types of binding sites consistent with known cell surface groups on bacteria, with mean pK(a) values of 3.62, 4.97, 6.92, 8.22, and 9.97. Composite surfaces formed by precipitation of HFO onto bacteria surfaces were also titrated. These surfaces no longer yielded low pK(a) sites in pK(a) spectra, indicating that ferric iron interacts with the bacteria via carboxylic (low pK(a)) sites during precipitation. In addition, mechanically mixed HFO bacterial samples also showed removal of carboxylic binding sites, suggesting that solid phase HFO interacts directly with carboxylic sites on bacterial cells. Moreover, the pK(a) spectra for HFO bacterial composites were not dependent on how the composite was formed; the mechanically mixed or surface-precipitated samples exhibited very similar binding site distributions. The determined pK(a) spectra imply that the overall binding mechanism for bacteria interactions with HFO involve carboxylic groups on the bacteria binding to the most basic sites on the HFO surface in approximately 1:1 stoichiometry.     

All-trans to 13-cis retinal isomerization in light-adapted bacteriorhodopsin at acidic pH

The flash photolysis kinetic spectra of the intermediate M(412) of bacteriorhodopsin were monitored during the process of acid titration. In the light-adapted state, the maximum peak amplitude of M(412) absorbance of bacteriorhodopsin decreased (pK(a)=3.40+/-0.05) as the pH decreased from 7.3 to 1.9. In the dark-adapted state, the maximum peak amplitude of M(412) absorbance of bacteriorhodopsin increased as the pH decreased from 6.9 to 4.1, and then decreased (pK(a)=2.85+/-0.05) as the pH dropped to 2.1. These different trends in the change in the maximum peak amplitude suggested that not only the transition of purple membrane to blue membrane had taken place in both light and dark-adapted states, but also the fraction of all-trans-bR had changed during the acid titration. The pH-dependent absorption changes at 640 nm of bacteriorhodopsin in both light- and dark-adapted states were also observed. The pK(a)-values of the purple-to-blue transition were 3.80+/-0.05 in light-adapted state and 3.40+/-0.05 in dark-adapted state, respectively. According to Balashov's method, the fraction of all-trans-bR was assayed as the pH decreased. All these results indicated that the purple-to-blue transition of light-adapted bacteriorhodopsin was accompanied by an all-trans to 13-cis retinal isomerization at acidic pH.     

可见吸收光谱线型参数分析法测定十二烷基硫酸钠临界胶束浓度

于浓度相同的结晶紫（CV）溶液中，加入不同浓度的十二烷基硫酸钠（SDS）组成一系列含有相同浓度CV和不同浓度SDS的混合溶液。在可见光区内对每一混合溶液测定其吸收值时，可见随SDS浓度的逐步递增，在CV-单聚体吸收峰的吸收值逐渐减少；而在CV-二聚体吸收峰的吸收值逐渐增加，且随CV-二聚体浓度增加而出现的CV-二聚体与CV-单聚体的吸收光谱线相互严重重叠，光谱形状也发生渐变。运用分光光度计所配备的Origin 7．5软件中储存的高斯多峰拟合法，可自动进行重叠光谱的解析和各光谱参数（包括y0，A1，A2，ω1，ω2，xc1及xc2）的拟合计算。文中还证示，每一参数与SDS浓度之间有明显的相关性，在两者之间所作的曲线上可找到明显的转折点，与转折点相对应的、在横坐标上的SDS浓度值即为SDS的临界胶束浓度（CMC）值。文中首次报道了用吸收光谱的半峰宽对SDS浓度作图所得曲线上的转折点求得SDS的CMC值。     

柑桔溃疡菌的共振散射光谱

研究了柑桔溃疡菌的共振散射光谱,在330、425、465和695 nm产生四个共振散射峰.当激发波长为330 nm （9.09×1014 Hz）时,溃疡菌溶液在330 nm（9.09×1014 Hz）、660 nm（1/2×9.09×1014 Hz）和990 nm（1/3×9.09×1014 Hz）分别产生一共振散射峰和1/2、1/3两个分频散射峰;当激发波长为465 nm（6.45×1014 Hz）时,在456 nm(6.45×1014 Hz)和930 nm(1/2×6.45×1014 Hz)分别产生一个共振散射峰和一个1/2分频射峰; 当激发波长为930 nm(3.23×1014 Hz)时,在930 nm (3.23×1014 Hz)、620 nm(3/2×3.23×1014 Hz)、465 nm(2×3.23×1014 Hz) 和310 nm (3×3.23×1014 Hz)分别产生一个共振散射峰,一个3/2分频共振散射峰,一个2倍频共振散射峰和一个3倍频共振散射峰.柑桔溃疡菌是一种非线性散射光学介质.分频散射和倍频散射峰与共振散射峰具有相似的散射行为.     

Color-tuning mechanism in firefly luminescence: theoretical studies on fluorescence of oxyluciferin in aqueous solution using time dependent density functional theory

The first singlet excited state geometries of various isomers and tautomers of firefly oxyluciferin (OxyLH2), as well as their fluorescence spectra in aqueous solution, were studied using time dependent density functional theory (TDDFT). With changing pH in aqueous solution, three fluorescence peaks, blue (450 nm), yellow-green(560 nm), and red (620 nm) correspond to neutral keto and enolic forms, the monoanionic enolic form,and the monocationic keto form respectively. A counterion, Na+, was predicted to cause a blue shift in the fluorescence of anionic OxyLH2. The contributions of a charge transfer (CT) state upon electronic excitation of the planar and twisted structures were predicted. CT was large for the twisted structures but small for the planar ones. The differences between pK and pK* of various oxyluciferin species were predicted using a Forster cycle. A new possible light emitter, namely, the monocation keto form (keto+1), was considered.     

Cl2O photochemistry: ultraviolet/vis absorption spectrum temperature dependence and O(3P) quantum yield at 193 and 248 nm

The photochemistry of Cl(2)O (dichlorine monoxide) was studied using measurements of its UV/vis absorption spectrum temperature dependence and the O((3)P) atom quantum yield, Φ(Cl(2)O)(O)(λ), in its photolysis at 193 and 248 nm. The Cl(2)O UV/vis absorption spectrum was measured over the temperature range 201-296 K between 200 and 500 nm using diode array spectroscopy. Cl(2)O absorption cross sections, σ(Cl(2)O)(λ,T), at temperatures <296 K were determined relative to its well established room temperature values. A wavelength and temperature dependent parameterization of the Cl(2)O spectrum using the sum of six Gaussian functions, which empirically represent transitions from the ground (1)A(1) electronic state to excited states, is presented. The Gaussian functions are found to correlate well with published theoretically calculated vertical excitation energies. O((3)P) quantum yields in the photolysis of Cl(2)O at 193 and 248 nm were measured using pulsed laser photolysis combined with atomic resonance fluorescence detection of O((3)P) atoms. O((3)P) quantum yields were measured to be 0.85 ± 0.15 for 193 nm photolysis at 296 K and 0.20 ± 0.03 at 248 nm, which was also found to be independent of temperature (220-352 K) and pressure (17 and 28 Torr, N(2)). The quoted uncertainties are at the 2σ (95% confidence) level and include estimated systematic errors. ClO radical temporal profiles obtained following the photolysis of Cl(2)O at 248 nm, as reported previously in Feierabend et al. [J. Phys. Chem. A 114, 12052, (2010)], were interpreted to establish a <5% upper-limit for the O + Cl(2) photodissociation channel, which indicates that O((3)P) is primarily formed in the three-body, O + 2Cl, photodissociation channel at 248 nm. The analysis also indirectly provided a Cl atom quantum yield of 1.2 ± 0.1 at 248 nm. The results from this work are compared with previous studies where possible.     

Comparison of three spectrophotometric methods for the determination of gamma-oryzanol in rice bran oil

A comparison of the results obtained by applying three spectrophotometric methods (at fixed wavelength, second-derivative and multicomponent analysis) to the determination of gamma-oryzanol in rice bran oil is reported.At fixed wavelength the results are more accurate when using isopropyl alcohol, rather than n-heptane, to dilute the oil samples, because the absorption bands of gamma-oryzanol are red-shifted and the absorbance, measured at lambda(max)=327 nm, is less affected by the interference of the oil "matrix" (lambda(max)=314 nm in n-heptane).However, to obtain accurate results also in oils with a low content of gamma-oryzanol, it is necessary to perform the analysis using second-derivative ((2)D330.365) or multicomponent (lambda=310-360 nm) methods. The first one fully removes the interference of oil matrix whilst the second, which needs a specific computational program to process the spectrophotometric data, furnishes evidence the presence of some unexpected interference in the analysis and/or standards which are not representative of the analysed samples, from the square root of the sum of the squared differences at each point between the linear combination of the standards and the unknown spectra (RMS error).Finally, some aspects of the chemical, spectroscopic (UV, IR) and thermoanalytical (TG, DSC) behaviour of gamma-oryzanol and the values of the parameters which enable "computation" of its UV spectra are reported.     

Simultaneous Determination of Caffeine and Meclizine Dihydrochloride in Sugar-Coated Tablets

Abstract

In this study, simultaneous determination of caffeine and meclizine dihydrochloride in their binary mixture was conducted by two spectrophotometric methods. In the first method, derivative spectrophotometry, the quantification of caffeine and meclizine dihydrochloride was performed by reading the dA/dλ values at 286.2 nm and 243.4 nm respectively in the first derivative spectra of their mixture in methanol. The relative standard deviation of the method was 0.54% for caffeine and 0.67% for meclizine dihydrochloride. In the second, selective precipitation + derivative spectrophotometry, determination of meclizine dihydrochloride was carried out by precipitation with potassium ferricyanide at pH 2 selectively, then measuring the absorbance of its solution in methanol at 420.8 nm, and determination of caffeine was succeeded by reading the dA/dλ values at 260.6 nm in the first derivative spectra of the remaining solution after precipitation. Relative standard deviation of the method was found to be 0.56% for caffeine and 1.85% for meclizine dihydrochloride. These two methods were applied successfully to a sugar-coated tablet containing these drugs.     

Synthesis, structure, and solution properties of [(mim-TASN)FeCl2]+ and its μ-oxo derivative

A series of iron(III) complexes based on the tetradentate ligand 4-((1-methyl-1H-imidazol-2-yl)methyl)-1-thia-4,7-diazacyclononane (L) has been synthesized, and their solution properties investigated. Addition of FeCl(3) to methanol solutions of L yields [LFeCl(2)]FeCl(4) as a dark red solid. X-ray crystallographic analysis reveals a pseudo-octahedral environment around iron(III) with the three nitrogen donors of L coordinated facially. Ion exchange reactions with NaPF(6) in methanol facilitate chloride exchange resulting in a different diastereomer for the [LFeCl(2)](+) cation. X-ray analysis of [LFeCl(2)]PF(6) finds meridional coordination of the three nitrogen donors of L. Electrochemical studies of [LFeCl(2)](+) in acetonitrile display a single Fe(III)/(II) reduction potential at -280 mV versus ferrocenium/ferrocene. In methanol, a broad cathodic wave is observed because of partial exchange of one chloride for methoxide with half-potentials of -170 mV and -440 mV for [LFeCl(2)](+/0) and [LFeCl(OCH(3))](+/0), respectively. The equilibrium constants for chloride exchange are 7 × 10(-4) M(-1) for Fe(III) and 2 × 10(-8) M(-1) for Fe(II). In aqueous solutions chloride exchange yields three accessible complexes as a function of pH. Strongly acidic conditions yield the aqua complex [LFeCl(OH(2))](2+) with a measured pK(a) of 3.8 ± 0.1. Under mildly acidic conditions, the μ-OH complex [(LFeCl)(2)(OH)](3+) with a pK(a) of 6.1 ± 0.3 is obtained. The μ-oxo complex [(LFeCl)(2)(O)](2+) is favored under basic conditions. The diiron Fe(III)/Fe(III) complexes [(LFeCl)(2)(OH)](3+) and [(LFeCl)(2)(O)](2+) can be reduced by one electron to the mixed valence Fe(III)/Fe(II) derivatives at -170 mV and -390 mV, respectively. From pH dependent voltammetric studies, the pK(a) of the mixed valent μ-OH complex [(LFeCl)(2)(OH)](2+) is calculated at 10.3.     

Time-Resolved Photoluminescence Spectra of Porous Si

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