Acid-induced tunable white light emission based on triphenylamine derivatives

A series of triphenylamine (TPA) derivatives with various substituent groups were prepared and showed different absorption and fluorescence characteristics due to the substituent effect. On account of the existence of pyridine units, these TPA derivatives exhibited acid-induced tunable multicolor fluorescence emission including white light emission. In addition, acid-induced fluorescence regulation of these compounds has been also realized in the solid state, which enable them to be successfully constructed the stimuli-responsive fluorescent films and fluorescent inks for inkjet printing.     

推/拉电子取代基对PCBM结构及光谱性质影响的理论研究

应用密度泛函理论(DFT)方法计算[6,6]-苯基-C₆₁-丁酸甲酯(PCBM)及其苯环对位取代得到的4种衍生物的几何和电子结构. 采用第一激发能校正了分子的最低未占据分子轨道(LUMO)能级, 探讨了推/拉电子基团对分子前线轨道的影响. 在全优化几何构型的基础上, 采用含时密度泛函理论(TD-DFT)方法研究了电子吸收光谱特征和电荷转移态性质, 并讨论了推/拉电子基团对体系电子吸收光谱性质的影响. 通过对重组能和电子亲和势的计算, 预测了PCBM与4种衍生物的电子能力及电子迁移率大小的关系. 结果表明, 在PCBM中, 在苯环的对位引入推电子基团可以提高分子的前线轨道能级, 改变前线轨道电子云分布, 明显增强可见光范围内的吸收强度, 增加可见光范围内的电荷转移吸收, 且激发态的电荷转移随着引入基团推电子能力的增加而增强. 化合物5的激发态分子内电荷转移性质最强, 且具有较独特的光伏性质. 而在同样位置引入拉电子基团, 则降低了分子前线轨道能级对电子吸收光谱的影响.     

Special Features of the Electrochemical Oxidation of Substituted 4-Carboxy-1,4-dihydropyridines

Electrochemical oxidation potentials of 1,4-dihydropyridines substituted with 4-COOH, 4-COOR, and 4-CONRR' groups have been determined in aprotic acetonitrile by the rotating ring-disk electrode method (RRDE). The electrochemical reduction potentials of the resulting products were also determined at the ring electrode. It was established that protonated pyridines are formed in the oxidation of derivatives with and without a substituent in position 4 of the heterocycle. In the case of 4-alkoxycarbonyl substituted compounds the substituent at position 4 is generally retained. 1,4-Dihydrogenated derivatives of isonicotinic acid as a rule loose the substituent at position 4 on oxidation, and both types of product were recorded for the corresponding 4-carbamoyl derivatives. The substituent at position 9 of the heterocycle was mainly retained on electrochemical oxidation of the 3,3,6,6-tetramethyl-1,8-dioxo-1,2,3,4,5,6,7,8,9,10-decahydroacridine derivatives studi! ed.     

Evaluation of DNA Binding with Some Selected Hydrazide and Semicarbazide Derivatives

A group of hydrazide and semicarbazide derivatives containing isopropylidene, benzylidene, cyclohexylidene, and phospholidene groups was synthesized and characterized by spectroscopic techniques. These compounds were tested for DNA interaction studies monitored by UV-Vis and IR data as well as molecular docking. Investigations on interactions of these compounds with DNA revealed an intercalative mode of binding between them. It is interesting to note that semicarbazide derivatives with aliphatic substituents showed better DNA binding than the aromatic substituents.     

Spiroconjugated Intramolecular Charge‐Transfer Emission in Non‐Typical Spiroconjugated Molecules: The Effect of Molecular Structure upon the Excited‐State Configuration

A set of terfluorenes and terfluorene‐like molecules with different pendant substitutions or side groups were designed and synthesized, their photophysical properties and the excited‐state geometries were studied. Dual fluorescence emissions were observed in compounds with rigid pendant groups bearing electron‐donating N atoms. According to our earlier studies, in this set of terfluorenes, the blue emission is from the local π–π* transition, while the long‐wavelength emission is attributed to a spiroconjugation‐like through‐space charge‐transfer process. Herein, we probe further into how the molecular structures (referring to the side groups, the type of linkage between central fluorene and the 2,2′‐azanediyldiethanol units, and—most importantly—the amount of pendant groups), as well as the excited‐state geometries, affect the charge‐transfer process of these terfluorenes or terfluorene‐like compounds. 9‐(9,9,9′′,9′′‐tetrahexyl‐9H,9′H,9′′H‐[2,2′:7′,2′′‐terfluoren]‐9′‐yl)‐1,2,3,5,6,7‐hexahydropyrido[3,2,1‐ij]quinolone (TFPJH), with only one julolidine pendant group, was particularly synthesized, which exhibits complete “perpendicular” conformation between julolidine and the central fluorene unit in the excited state, thus typical spiroconjugation could be achieved. Notably, its photophysical behaviors resemble those of TFPJ with two pendant julolidines. This study proves that spiroconjugation does happen in these terfluorene derivatives, although their structures are not in line with the typical orthogonal π fragments. The spiroconjugation charge‐transfer emission closely relates to the electron‐donating N atoms on the pendant groups, and to the rigid connection between the central fluorene and the N atoms, whereas the amount of pendant groups and the nature of the side chromophores have little effect. These findings may shed light on the understanding of the through‐space charge‐transfer properties and the emission color tuning of fluorene derivatives.     

Facile access to highly fluorescent nanofibers and microcrystals via reprecipitation of 2-phenyl-benzoxazole derivatives

2-Phenyl-benzoxazole and five derivatives bearing an alkyl or alkoxy substituent on the phenyl ring were used to prepare aqueous suspensions of particles via a solvent-exchange method. In these conditions, the methyl and methoxy derivatives spontaneously gave nanofibers, while the other compounds led to microcrystals. This shows that minor chemical changes are enough to direct the formation of a given type of particle. From a spectroscopic viewpoint, all compounds strongly emit blue light in the solid state, with spectra much broader than those registered in n-heptane and ethanol solutions. The photoluminescence quantum yields reached 38% and were slightly affected in aqueous suspension by the polarity of the environment. The molecular arrangement, deduced from X-ray analysis for the methyl and methoxy derivatives, was used to explain the fluorescence properties in the solid state. This work shows that 2-phenyl-benzoxazole derivatives are interesting candidates for applications as fluorescent nanomaterials, including in aqueous and biological media.     

具有表皮生长因子受体抑制活性的喹唑啉衍生物研究进展

综述了近十年来具有表皮生长因子受体(EGFR)抑制活性的喹唑啉衍生物的国内外研究进展,按照喹唑啉环上不同位置上的取代基类型分为四类,介绍了化合物不同位置上取代基对此类化合物生物活性的影响,并对其发展趋势和应用前景作了展望.     

N1取代基结构对菲并咪唑荧光色纯度的影响

以1,2-二苯基菲并咪唑(PPI)为模型化合物, 通过改变N1苯环上取代基结构制备了2类PPI衍生物, 并采用核磁共振谱对其化学结构进行了确认. 通过对PPI及其衍生物的单分子荧光光谱精细结构的分析, 比较了取代基位置和结构的变化对菲并咪唑类化合物荧光过程中发射主峰精细振动结构及所占比例的影响. 其中, N1链接苯环中R4位的取代基效应最显著, 当引入推电子或弱的吸电子取代基时, 菲并咪唑类衍生物的低能级发射比例降低, 荧光色纯度提高; 当引入强吸电子取代基时, 低能级发射比例增加, 光谱半峰宽加大. 本文结果为菲并咪唑基“蓝光”材料的设计提供了一定数据的支持与科学依据.     

Substituent effects on the properties related to detonation performance and sensitivity for 2,2',4,4',6,6'-hexanitroazobenzene derivatives

To look for superior and safe high energy density compounds (HEDCs), 2,2',4,4',6,6'-hexanitroazobenzene (HNAB) and its -NO(2), -NH(2), -CN, -NC, -ONO(2), -N(3), or -NF(2) derivatives were studied at the B3LYP/6-31G* level of density functional theory (DFT). The isodesmic reactions were applied to calculate the heats of formation (HOFs) for these compounds. The theoretical molecular density (ρ), detonation energy (E(d)), detonation pressure (P), and detonation velocity (D), estimated using the Kamlet-Jacobs equations, showed that the detonation properties of these compounds were excellent. The effects of substituent groups on HOF, ρ, E(d), P, and D were studied. The order of contribution of the substituent groups to P and D was -NF(2) > -ONO(2) > -NO(2) > -N(3) > -NH(2). Sensitivity was evaluated using the nitro group charges, frontier orbital energies, and bond dissociation enthalpies (BDEs). The trigger bonds in the pyrolysis process for all these HNAB derivatives may be Ring-NO(2), Ring-N═N, Ring-NF(2), or O-NO(2) varying with the attachment of different substituents. BDEs of trigger bonds except those of -ONO(2) derivatives are relatively large, which means these compounds suffice the stability request of explosives. Taking both detonation properties and sensitivities into consideration, some -NF(2) and -NO(2) derivatives may be potential candidates for HEDCs.     

Nitro derivatives of 1-picrylbenzotriazole

The synthesis of the isomeric 4,6-, 5,6-, and 5,7-dinitro-1-picrylbenzotriazoles has been accomplished. The nmr spectra of these compounds and the mononitro derivatives of 1-picrylbenzotriazole were determined and the substituent effects of the nitro and picryl groups on the chemical shifts of the various benzotriazole protons are discussed.     

The study of molecular motions in substituted ferrocenes by means of NMR spectroscopy

The proton magnetic resonance spectra for ferrocene derivatives have been investigated in the solid state at a frequency of 27.5 MHz and at temperatures within the range 4.2–300 K. Evidence for re-orientation in various substituent groups and cyclopentadienyl rings has been deduced on the basis of the temperature dependence of the second moment of the PMR lines. The experimentally observed decrease in the second moment has been compared with the calculated contributions of different molecular groups to the second moment thus enabling an identification of these groups. In computing the second moment, account has been taken of both intra- and intermolecular dipole-dipole interactions. It is shown that the introduction of substituents into some ferrocene rings affects the magnitude of the re-orientation energy for both the substituted and unsubstituted rings. The change of the re-orientation energy of the substituted and unsubstituted rings in substituted ferrocenes with the structure and electronic properties of the substituents is discussed.     

4-Azidotetronic Acids: A New Class of Azido Derivatives

4-Azidotetronic derivatives bearing different substituent groups on the carbon atom in position 3 were easily obtained by reaction of the corresponding 4-bromotetronic compounds with sodium azide in methanol at room temperature.     

Structure-fluorescence relationship of push-pull 2-phenylbenzothiazole derivatives designed based on the firefly light-emitter

6-Dimethylamino-2-phenylbenzothiazole (1a) mimicking the firefly oxyluciferin structure and the derivatives with an electron-withdrawing substituent on the phenyl group were prepared, and their fluorescence properties were investigated in various solvents. 1a showed solvatochromic fluorescence with good fluorescence quantum yields (Φ_f >0.8). The introduction of an electron-withdrawing group led to a red-shift of the emission maximum. In particular, the derivatives with the 2,2-dicyanoethenyl and (1,3-dihydro-1,3-dioxo-2H-inden-2-ylidene)methyl groups showed near-infrared fluorescence in chloroform. In addition, the derivative with the phenylimine moiety showed efficient solid-state fluorescence, resulted from a molecular arrangement inhibiting intermolecular interactions for quenching the fluorescence state in crystals.     

具有扭曲的分子内电荷转移的芳香酮衍生物的结构与光谱性能研究

设计合成了一系列基于芳香酮的具有分子内扭曲态电荷转移(TICT)特性的化合物,通过线性光物理性质与双光子吸收性质的表征,研究了分子结构中不同共轭基团和不同取代基位置对化合物光谱性能的影响,同时通过溶剂效应研究了化合物的分子内电荷转移性质。结合理论计算结果表明分子的共轭骨架和取代基的位置都能显著影响分子内电荷转移特征。其中芴酮系列的化合物表现出了较强的双光子吸收与聚集诱导荧光增强效应,在生物荧光成像领域有着潜在的应用价值。     

Solvatofluorochromic properties of sulfonyl fluoride derivatives of 5-aryl(heteroaryl)-2-phenyl-1,3,4-oxadiazole, promising fluorescent probes

The spectral characteristics of seven 5-aryl(heteroaryl)-2-phenyl-1,3,4-oxadiazole derivatives, containing an expressed electron-accepting grouping such as sulfonyl fluoride or sulfonyldifluoromethane in the para position of the phenyl substituent, have been investigated in solvents of various polarity. The insignificant effect of the n^* levels of the SO₂X grouping on the fluorescence properties of the compounds studied was established, as a result of which they are highly effective organic luminophors in the near ultraviolet and violet spectral ranges. The presence was shown of a significant solvatochromic effect exerted particularly clearly in derivatives with electron-donating groups in the 5-aryl substituent. As a result of this, the compounds indicated may be recommended for use as fluorescent probes in medicine and biology. Adiabatic flattening in the excited state of the sterically hindered methoxy derivative and the formation of a TICT state are considered, leading to quenching of the fluorescence of dimethylamino derivatives in media of high polarity.Kharkov State University, Kharkov 310077. Institute of Monocrystals, Academy of Sciences of the Ukraine, Kharkov 310001. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 988–994, July, 1997.     

Recognition of Multiple Methyl Groups on Aromatic Rings by a Polyaromatic Cavity

The methyl group is a small substituent, usually showing relatively weak or no interactions with other functional groups and metal ions. Herein, we present the recognition of the number of methyl groups on synthetic and natural aromatic compounds (i.e., benzene and xanthine derivatives, respectively) by the 1 nm‐sized polyaromatic cavity of a coordination capsule in water. Detailed competitive encapsulation experiments as well as X‐ray crystallographic analysis revealed that multiple guest–host CH₃–polyaromatic interactions in the confined nanospace are key driving forces for the high selectivity.     

取代基对依布硒啉电子结构及光谱性质影响的理论研究

采用密度泛函理论B3LYP方法在6-311++G**水平对依布硒啉及其6个衍生物进行结构优化,并分析了取代基对分子几何构型、电荷分布、前线轨道能级分布的影响.在相同计算水平上采用含时密度泛函理论方法进行了电子光谱研究,讨论了取代基对电子光谱的影响.计算结果表明,标题化合物分子为非平面结构,苯并异硒唑酮环与苯环之间存在一...     

可聚合1,8-萘酰亚胺衍生物掺杂聚硅氧烷复合材料的合成及荧光特性

合成了3种可聚合的1,8-萘酰亚胺衍生物, 并研究了其在二甲基亚砜(DMSO)溶液中的光物理性质. 这些化合物表现出的光物理性质与其电子环境有关. 通过溶胶-凝胶法制备了可聚合1,8-萘酰亚胺衍生物与硅氧烷的共聚物. 尽管3种萘酰亚胺衍生物C-4位的取代基不同, 但在3-氨丙基三乙氧基硅烷(APTES)固凝胶中摩尔分数为0.06%时荧光强度均最大. 利用 ²⁹Si MAS NMR对合成材料进行了表征, 结果表明, 硅氧烷的缩聚程度影响材料的荧光强度, 说明材料中荧光单元的分子运动对材料的荧光性能有重要影响.     

Substitutent effects in the periphery of 2,9-bisaryl-tetraazaperopyrene dyes

A series of 2,9-bisaryl-1,3,8,10-tetraazaperopyrene (TAPP) derivatives has been synthesized by reacting 4,9-diamino-3,10-perylenequinone diimine with a large excess of the corresponding benzoyl chloride in refluxing nitrobenzene. Among all derivatives only ortho-substituted phenyl congeners were sufficiently soluble for studying solutions of defined concentration in organic solvents. The molecular structures of the crystallized compounds, determined by X-ray diffraction of four derivatives, are determined by the planar tetraazaperopyrene core and the interplanar angle of the phenyl rings, which depends on the size of the ortho substituent (40-70°). The intermolecular packing pattern of all compounds is characterized by parallel stacks of molecules with the substituted phenyl rings rotated out of the peropyrene plane to reduce the steric repulsion. Crystals of a TAPP derivative suitable for X-ray diffraction were grown from trifluoroacetic acid (TFA) for the first time, establishing a 2-fold protonated species. The ground-state geometries of the TAPP derivatives were calculated by DFT [B3PW91/6-31g(d,p)] and the lowest unoccupied molecular orbital (LUMO) energies of derivatives possessing electron-withdrawing groups were decreased, as were the computed electron affinities. The results of the modeling study were confirmed experimentally by cyclic voltammetry to evaluate the substituent effects on the highest occupied molecular orbital (HOMO) and the LUMO of the peropyrene core. The UV-vis absorption spectra of all compounds recorded in trifluoroacetic acid are almost superimposable and display a characteristic visible absorption band between 460 and 490 nm (log ε = 4.64-5.01) with a strong vibrational progression of 1173-1475 cm(-1). Their fluorescence spectra are characterized by bands between 490 and 530 nm that are the mirror images of the absorption spectra (Stokes shifts of 10-50 nm). The luminescence quantum yields range from <0.01 to 0.30, thereby indicating a quenching effect for some substitution patterns.