Exciton Chirality. (A) Origins of and (B) Applications from Strongly Fluorescent Dipyrrinone Chromophores

Summary. (A) The origin of exciton interaction and examples of its application to organic stereochemistry are presented. (B) N,N-Carbonyl-bridged dipyrrinones constitute a new class of highly fluorescent chromophores suitable for investigations of stereochemistry and absolute configuration. N,N-Carbonylxanthobilirubic acid esters are strongly fluorescent, with a fluorescence quantum yield (_F) 0.8, but produce only weak exciton CD from the trans-1,2-cyclohexanediol template. The ester of an analog with benzoic acid replacing propionic, N,N-carbonyl-8-(4-carboxyphenyl)-3-ethyl-2,7,9-trimethyl-(10H)-dipyrrin-1-one, exhibits strong fluorescence (_F=0.68, _em=493nm, _ex=422nm in CHCl₃) and UV-Vis absorption (21000 at 424nm) in organic solvents. Its diester with (1S,2S)-cyclohexanediol is fluorescent and exhibits exciton circular dichroism (=+15dm³·mol^–1·cm^–1, =432nm; =–4dm³·mol^–1cm^–1, =380nm) that correlates with the Exciton Chirality Rule.     

New Applications of the CD Exciton Chirality Method. Stereochemical Assignment of Organic Compounds Containing Carboxylic Acid Groups

CD exciton chirality methods are described for the stereochemical assignment of organic compounds containing carboxylic acid groups. Using the chromophoric combination 2-naphthoate or 2-anthroate and 9-anthrylmethyl group the absolute stereochemistry of - and -hydroxy carboxylic acids can be deduced from a single CD measurement. Furthermore, as demonstrated with cyclic and acylic dicarboxylic acids, the direct esterification of sterically hindered carboxyl groups with 2-naphthol also allows the stereochemical assignment via CD spectroscopy.     

New Applications of the CD Exciton Chirality Method. Stereochemical Assignment of Organic Compounds Containing Carboxylic Acid Groups

Summary. CD exciton chirality methods are described for the stereochemical assignment of organic compounds containing carboxylic acid groups. Using the chromophoric combination 2-naphthoate or 2-anthroate and 9-anthrylmethyl group the absolute stereochemistry of - and -hydroxy carboxylic acids can be deduced from a single CD measurement. Furthermore, as demonstrated with cyclic and acylic dicarboxylic acids, the direct esterification of sterically hindered carboxyl groups with 2-naphthol also allows the stereochemical assignment via CD spectroscopy.     

一种新型手性分子电性矩边矢量(Vmedc)的设计及其应用

根据分子中不同类型原子间电相互作用的不同, 文中提出了一种手性分子电矩边矢量(Vmedc), 进一步拓展分子电矩边性矢量(Vmed)使用范围. 为检测该手性描述矢量的结构表达特性和模型预测能力, 分别对32个培哚普利拉类血管紧张素转化酶(ACE)抑制剂的对映结构体和7对苯基哌啶类σ-受体抑制剂进行考察. 32个ACE抑制剂多元逐步回归系数R＝0.913 (R2＝0.834, SD＝0.768, F＝33.875), 留一法交互检验为Rcv＝0.877 (Rcv2＝0.769, SDcv＝0.906, Fcv＝22.473), 具有较强预测能力; 继而用BP神经网络, 对60组随机样本(23∶9)进行留分法分析取得较好结果, 训练集平均为: RTraining＝0.931 (RTraining2＝0.967), 预测集为: Rcv＝0.918 (Rcv2＝0.842); 而对14个σ-受体抑制剂多元回归(R＝0.955, Rcv2＝0.849)获得与文献一致结果. 再用Fisher线性判别方法和BP神经网络对ACE抑制剂进行判别分析, 其活性分类88.89%正确(仅9号错误), 非活性分类100.0%正确, 总分类正确率为96.87%. 两个数据集测试证明该方法与其它文献方法相当, 这为定量构效关系(QSAR)研究提供一种新选择, 扩充了Vmed描述矢量应用范围.     

Optically Active Macrocyclic cis‐3 Bis‐Adducts of C60: Regio‐ and Stereoselective Synthesis,Exciton Chirality Coupling,and Determination of the Absolute Configuration,and First Observation of Exciton Coupling between Fullerene Chromophores in a Chiral Environment

A series of optically active cis‐3 bis‐adducts, such as (R,R,^fC)‐ 16 (Scheme 6), was obtained regio‐ and diastereoselectively by Bingel macrocyclization of C₆₀ with bis‐malonates, which contain optically active tethers derived from 1,2‐diols. The absolute configuration of the inherently chiral addition pattern in cis‐3 bis‐adducts had previously been determined by comparison of calculated and experimental circular dichroism (CD) spectra. Full confirmation of these earlier assignments was now obtained by an independent method based on semiempirical AM1 (`Austin Model 1') and OM2 (`Orthogonalization Method 2') calculations combined with ¹H‐NMR spectroscopy. It was found computationally that bis‐malonates [CHR(OCOCH₂COOEt)]₂, which contain (R,R)‐ or (S,S)‐butane‐2,3‐diol derivatives as optically active tethers, preferentially form out‐out cis‐3 bis‐adducts of C₆₀ as a single diastereoisomer in which the alkyl groups R adopt a gauche conformation, while the two glycolic H‐atoms are in an antiperiplanar (ap) and the ester linkages to the fullerene in a gauche relationship (Figs. 2 and 5). In contrast, in the less favorable diastereoisomer, which should not form, the alkyl groups R adopt an ap and the H‐atoms a gauche conformation, while the ester bridges to the fullerene remain, for geometric reasons, locked in a gauche conformation. According to the OM2 calculations, the geometry of the fully staggered tether in the free bis‐malonates closely resembles the conformation of the tether fragment in the bis‐adducts formed. These computational predictions were confirmed experimentally by the measurement of the coupling constant between the vicinal glycolic H‐atoms in the ¹H‐NMR spectrum. For (R,R,^fC)‐ 16 , ³J(H,H) was determined as 7.9 Hz, in agreement with the ap conformation, and, in combination with the calculations, this allowed assignment of the ^fC‐configuration to the inherently chiral addition pattern. This conformational analysis was further supported by the regio‐ and diastereoselective synthesis of cis‐3 bis‐adducts from bis‐malonates, including tethers derived from cyclic glycol units with a fixed gauche conformation of the alkyl residues R at the glycolic C‐atoms. Thus, a bis‐malonate of (R,R)‐cyclohexane‐1,2‐diol provided exclusively cis‐3 bis‐adduct (R,R,^fC)‐ 20 in 32% yield (Scheme 7). Incorporation of a tether derived from methyl 4,6‐O,O‐benzylidene‐α‐D ‐glucopyranoside into the bis‐malonate and Bingel macrocyclization diastereoselectively produced the cis‐3 stereoisomer (α,D ,^fA)‐ 22 (Scheme 8) as the only macrocyclic bis‐adduct. If the geometry of the alkyl groups R at the glycolic C‐atoms of the tether component deviates from a gauche relationship, as in the case of tethers derived from exo cis‐ and trans‐norbornane‐2,3‐diol or from trans‐cyclopentane‐1,2‐diol, hardly any macrocyclic product is formed (Schemes 5 and 9). The absolute configurations of the various optically active cis‐3 bis‐adducts were also assigned by comparison of their CD spectra, which are dominated by the chiroptical contributions of the inherently chiral fullerene chromophore (Figs. 1, 3, and 4). A strong chiral exciton coupling was observed for optically active macrocyclic cis‐3 bis‐adducts of C₆₀ with two appended 4‐(dimethylamino)benzoate ((S,S,^fC)‐ 26 ; Fig. 6) or meso‐tetraphenylporphyrin ((R,R,^fC)‐ 28 ; Fig. 7) chromophores. Chiral exciton coupling between two fullerene chromophores was observed for the first time in the CD spectrum of the threitol‐bridged bis‐fullerene (R,R)‐ 35 (Fig. 9).     

Chromophores from hexeneuronic acids (HexA): synthesis of model compounds and primary degradation intermediates

Hexeneuronic acid (HexA) is formed under pulping conditions from 4-O-methyl-glucuronic acid residues in xylans by methanol elimination. It is usually removed by an acidic washing treatment (A-stage) within the pulp bleaching sequence. Hexeneuronic acid has long been recognized as a source of color generation in pulps, but the chemical structure of the actual chromophoric compounds remained elusive. We report the synthesis of isotopically (¹³C) labeled HexA model units carrying a label at any of the six carbon atoms. Confirming pertinent literature accounts, it is shown that HexA forms three primary degradation intermediates, 2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, and formic acid, under mildly acidic conditions, and their formation mechanism is discussed. 2-Furancarboxylic acid is demonstrated to be deformylation product of 5-formyl-2-furancarboxylic acid. The three primary intermediates are colorless and do not represent chromophores themselves. Their mixture, upon thermal or acidic treatment, gives rise to the same chromophores that are also directly formed from HexA.     

4,5-Bis(arylethynyl)-1,2,3-triazoles—A New Class of Fluorescent Labels: Synthesis and Applications

Cu-catalyzed 1,3-dipolar cycloaddition of ethyl 2-azidoacetate to iodobuta-1,3-diynes and subsequent Sonogashira cross-coupling were used to synthesize a large series of new triazole-based push–pull chromophores: 4,5-bis(arylethynyl)-1H-1,2,3-triazoles. The study of their optical properties revealed that all molecules have fluorescence properties, the Stokes shift values of which exceed 150 nm. The fluorescent properties of triazoles are easily adjustable depending on the nature of the substituents attached to aryl rings of the arylethynyl moieties at the C4 and C5 atoms of the triazole core. The possibility of 4,5-bis(arylethynyl)-1,2,3-triazoles’ application for labeling was demonstrated using proteins and the HEK293 cell line. The results of an MTT test on two distinct cell lines, HEK293 and HeLa, revealed the low cytotoxicity of 4,5-bis(arylethynyl)triazoles, which makes them promising fluorescent tags for labeling and tracking biomolecules.     

The Circular Dichroism of 5,6-Dimethylidene-2-bicyclo[2.2.n]alky Esters. Chiral Exciton Coupling between Benzoate and Exocyclic s-cis-Butadiene Chromophores

The optically pure aryl-substituted 5,6-dimethylidene-2-bicyclo[2.2.1]heptyl benzoates 12–21 were prepared; their UV absorption and CD spectra are reported. The (?)-(1S,2S)-esters 17–21 with carbonyl groups in endo-position exhibit typical excitonsplit Cotton effects whereas the corresponding (?)-(1S,2R)-esters 12 - 16 with carbonyl groups in exo-position do not present such effects. The chiral exciton coupling between the exocyclic diene and a remote p-substituted benzoate chromophore can be used for unambiguous assignment of the absolute configuration of 5,6-dimethylidene-2-endo-bicyclo[2.2.1]heptyl derivatives. The method is applied to establish the absolute configuration of 5,6-dimethylidene-2-exo and -2-endo-bicyclo[2.2.2.]octyl p-bromobenzoates (?)- 24 and (?)- 25 .     

罗丹明类荧光染料的合成及应用

本文综述了近年罗丹明类荧光染料的研究进展,详细介绍了它们的结构特征、设计思路、合成方法、目前效果及在生物分析检测领域的应用,并对其未来的发展进行了展望。     

三维荧光光谱技术分析应用进展

本文对三维荧光技术的发展及其分析应用作了回顾,评述与展望,引用文献７５篇。     

蛋白质分子荧光探针研究及其应用新进展

人体中多达10万种以上的蛋白质结构,功能千差万别,形成了生命的多样性和复杂性。在分子水平上分析和识别蛋白质对生命科学研究具有重要的理论和实践意义。本文综述了各种蛋白质分子荧光探针在蛋白质分析方面的应用,并展望了此类荧光探针的发展趋势和应用前景。引用文献60篇。     

罗丹明类荧光染料的合成及应用

本文综述了近年罗丹明类荧光染料的研究进展,详细介绍了它们的结构特征、设计思路、合成方法、目前效果及在生物分析检测领域的应用,并对其未来的发展进行了展望。     

Synthesis,Structure, Photoluminescence,and Electroluminescence of Siloles that Contain Planar Fluorescent Chromophores

Herein, a new series of siloles that were 2,5‐substituted with planar fluorescent chromophores (PFCs), including fluorene, fluoranthene, naphthalene, pyrene, and anthracene, were synthesized and characterized. These compounds showed weak emission in the solution state, owing to active intramolecular rotation (IMR), but the synergistic effect from electronic coupling between the PFC and the silole ring compensated for the emission quenching by the IMR process to some extent, thereby affording higher emission efficiencies than those of 2,3,4,5‐tetraphenylsiloles in solution. These new siloles showed enhanced emission efficiencies in the aggregated state. The electroluminescence (EL) color and efficiency of new siloles were sensitive towards the PFC. Siloles containing naphthalene moieties showed green EL emission, whilst those containing anthracene moieties showed orange EL emission. The siloles containing pyrene moieties exhibited yellow EL emission at 546 nm, with a peak luminance of 49000 cd cm^?2 and a high current efficiency of 9.1 cd A^?1.     

Structure and Electronic Properties of Extended Chromophores for Applications in Second-Order Nonlinear Optics

A structural and theoretical analysis of new 2-[(4-phenylazo)phenyl] benzoxazole chromophores of potential interest in the field of second-order nonlinear optics is presented. Computations predict comparatively high hyperpolarizabilities for most of the compounds in their equilibrium nuclear configuration, with a significant dependence upon some conformational degrees of freedom and independence upon some others. This behavior is rationalized in the frame of the two-level model and sheds light on the conjugation pattern of these new chromophores.