柱芳烃机械互锁结构的制备及功能化

柱芳烃是一类具有柱状空腔结构的大环主体,近年来逐渐成为主客体作用构筑超分子体系的重要模块之一。柱芳烃家族包含柱[5]芳烃到柱[15]芳烃等成员,其中柱[5]芳烃为热力学稳定产物,合成产率最高;其次为柱[6]芳烃。柱[5]芳烃或柱[6]芳烃可做为主体,参与构筑[1](准)轮烷、[1](准)索烃等机械自锁结构,以及[n]轮烷(n≥2)、[2]索烃、雏菊链等机械互锁结构;体系中独立分子之间存在相对运动,如轮烷中柱芳烃在轴线上可以进行穿梭运动;丰富的衍生基团赋予柱芳烃互锁结构相应的功能,如手性翻转、荧光共振能量转移、超分子凝胶、Langmuir膜、催化反应等,甚至基于柱芳烃轮烷还可构筑更复杂的树枝状分子。本文综述了柱芳烃超分子互锁体系的研究进展,详细阐述了基于柱芳烃的互锁结构的合成方法及其功能化并讨论了其在构筑分子器件及其他超分子复杂体系方面的应用前景。     

基于氢键组装的[60]富勒烯超分子体系

具有独特的结构和良好的性能的[60]富勒烯超分子体系在有机光电器件、超分子器件和催化等方面有着广阔的应用前景. 综述了基于氢键组装的[60]富勒烯超分子体系, 并对其发展前景作了展望.     

《化学通报》网络版（Chemistry Online）2006年第11期论文摘要

[w091]“消相反应”在合成中的应用；[w092]微乳体系有机电化学合成研究进展；[w093]光致变色二芳烯分子光开关的研究进展；[w094]化学传感器法检测硝基化合物；[w095]分子印迹膜的制备及应用进展；[编者按]     

新型树枝状硫醇的自组装单层膜──图案化表面及其浸润性的调控

近年来 ,自组装膜的研究不断引起人们重视[1] .一方面 ,其兴趣可能源于纳米级器件的组装 ,如生物传感器等 [2 ] ;另一方面 ,它可作为研究摩擦学 [3]、生物膜模拟 [4 ]和微观浸润性的模型体系 [5] .树枝状分子的结构可在分子水平上精确控制 ,是很有潜力的纳米构筑基元 [6 ] .不同于常规的自组装膜构筑基元 ,树枝状分子的特殊结构使其在金属表面形成某些特殊的组装结构成为可能 .结合界面分子自组装技术和树枝状分子化学 ,国内外已有机构开展了树枝状硫醇的自组装膜的研究[7～ 9] .我们曾发现一种聚醚树枝状硫醇分子在金表面形成的自组装单层…     

对硝基杯[8]芳烃的合成及其与奥克托今的配合

以对叔丁基苯酚与多聚甲醛为原料合成了对硝基杯[8]芳烃.利用紫外光谱研究了对硝基杯[8]芳烃与奥克托今(HMX)在氯仿中的配合性能.用量子化学半经验AM1和ab initio HF/3-21G方法,分别得到主、客体及其超分子体系几何全优化结构.结果表明,主客体分子形成了1: 1的配合物,标准状况下对硝基杯[8]芳烃与HMX形成超分子体系后较单体能量之和减少60.76 kJ/mol,主客体间可形成氢键.对硝基杯[8]芳烃与HMX超分子体系的稳定常数Kw从288 K的1.138×1012降至408 K时的1.121×105.     

电流滴定法对自组装膜表面酸碱性的研究

近年来 ,有序分子自组装体系在基础研究和应用领域均得到了较大的发展 .选择末端可以解离的自组装分子而制成的自组装膜 ,可以方便地通过调节底液的 p H值来控制膜体系的荷电状况 [1] ,这在利用静电作用吸附蛋白质 [2 ] 、多肽 [3] 、 DNA[4 ] 、聚电解质 [5] 、金属离子及其它物种 [6] 等方面具有重要作用 .精确测定表面解离常数 (即表面 p Ka)和控制自组装膜表面的荷电状况 ,无疑在理论研究和实践中均占有重要地位 .目前 ,一些方法如接触角滴定 [7] 、微分界面电容 [8] 、电流滴定法 [9,10 ] 以及 AFM的力曲线滴定 [11,12 ]被用于表面…     

气态[HPro（C1）]＋和[Sac]-相互作用及质子转移机制的理论研究

质子化功能离子液体在许多重要领域具有潜在的应用价值,然而人们对其相互作用模式、质子转移行为等方面的认识尚不清晰．本文利用DFT／B3LYP和MP2方法,以脯氨酸阳离子[HPro]＋、脯氨酸甲酯阳离子[HProC1]＋和糖精阴离子[Sac]=组成的质子化离子液体（PILs）为研究对象,探讨气态离子对、分子对、双聚体团簇中的结构单元及其作用模式．利用过渡态和内禀反应坐标（IRC）理论研究气态[HPro]＋[Sac]-和[HProCl]＋[Sac]-中的质子转移反应,AIM（atomsinmolecules）理论分析给出氢键相互作用本质等．计算结果表明,气态单聚体中氢转移能垒很小,体系中存在离子对和分子对的动态平衡．质子转移发生后,体系内部基本作用单元改变,作用强度下降,形成分子对的相互作用能量远远小于离子对的相互作用能量．双聚体团簇计算说明体系中没有质子转移反应发生,在[HPro]2＋[Sac]2-中相互作用的基本结构单元为离子、分子和两性离子,酯化后双聚体[HProC1]2＋[Sac]2-中全部为阴阳离子相互作用．质子转移反应、两性离子和酯化作用等的深入研究对于理解功能化PILs的性质、结构因素及其应用具有一定的实际意义．     

水溶性柱[6]芳烃与1,1'-双取代二茂铁衍生物的主-客体作用研究

基于单取代二茂铁与柱芳烃主体大环分子构筑的超分子功能体系在诸多领域中已经取得了较好的进展.对1,1'-双取代二茂铁衍生物与水溶性柱[6]芳烃的主-客体作用进行了初步的探索与研究,为以后开展基于双取代二茂铁衍生物与水溶性柱[6]芳烃的轮烷、准轮烷体系以及其他相关超分子功能体系奠定基础.     

“推-拉”型巯基偶氮苯衍生物的合成

分子电子器件的研究是近期基础研究中受到极大关注的前沿热点[1-4]。带巯基的有机分子在金电极表面形成的自组装单分子膜(SAMs)及其电活性,是分子电子学领域具有代表性和研究最多的体系之一[5-13]。由于结构的特殊性和特征的光致异构化,偶氮苯衍生物具有对光和电的双重活性[14]     

冠醚取代蒽醌超分子体系的设计与合成及分子内能量转移的研究

大环冠醚由于其自组装性能及分子识别能力而引起人们广泛的重视.近来,冠醚又成为在超分子体系中用于建构主体分子的一种重要的建造单元^[1~4].Costa^[5]等曾报道苯并冠醚与被识别的稀土离子铕(Ⅲ)与铽(Ⅲ)之间的能量传递过程,选择性激发冠醚主体观察到稀土离子的发光.由于二氮杂冠醚与稀土离子能形成更稳定的配合物^[6].我们利用了冠醚分子的分子识别能力及蒽醌分子的光敏性,设计合成了一种新的氮杂冠醚取代蒽醌分子(图1)(以下文中用代号AQ-CW表示),并以该分子作为主体分子,以稀土离子作为客体构成超分子体系,研究超分子体系内的能量转移过程.     

Mechanisms of photoinitiated cleavage of DNA by 1,8-naphthalimide derivatives.

Using water-soluble 1,8-naphthalimide derivatives, the mechanisms of photosensitized DNA damage have been elucidated. Specifically, a comparison of rate constants for the photoinduced relaxation of supercoiled to circular DNA, as a function of dissolved halide, oxygen and naphthalimide concentration, has been carried out. The singlet excited states of the naphthalimide derivatives were quenched by chloride, bromide and iodide. In all cases the quenching products were naphthalimide triplet states, produced by induced intersystem crossing within the collision complex. Similarly, the halides were found to quench the triplet excited state of the 1,8-naphthalimide derivatives by an electron transfer mechanism. Bimolecular rate constants were < 10(5) M-1 s-1 for quenching by bromide and chloride. As expected from thermodynamic considerations quenching by iodide was 6.7 x 10(9) and 8.8 x 10(9) M-1 s-1 for the two 1,8-naphthalimide derivatives employed. At sufficiently high ground-state concentration self-quenching of the naphthalimide triplet excited state also occurs. The photosensitized conversion of supercoiled to circular DNA is fastest when self-quenching reactions are favored. The results suggest that, in the case of 1,8-naphthalimide derivatives, radicals derived from quenching of the triplet state by ground-state chromophores are more effective in cleaving DNA than reactive oxygen species or radicals derived from halogen atoms.     

New excited state intramolecular proton transfer (ESIPT) dyes based on naphthalimide and observation of long-lived triplet excited states

A new excited state intramolecular proton transfer chromophore of naphthalimide (NI) conjugated 2-(2-hydroxyphenyl) benzothiazole () was prepared which shows red shifted absorption and long-lived triplet excited states.     

Triplet state quenching by ruthenocene

Ruthenocene quenches triplet states of organic molecules with energies greater than 24000 cm^?1 in benzene solution at a diffusion controlled rate , (6 ± 1) × 10⁹ dm³ mol^?1 s^?1. For triplets with energies less than this the efficiency of quenching is dependent on the energy of the triplet state being quenched but drops off less acutely than expected for endothermic energy transfer following the Arrhenius equation. This is in agreement with the lowest triplet state of ruthenocene being geometrically distorted as expected from the previously observed large Stokes shift between absorption to and emission from its lowest triplet state. Similarities to ferrocene quenching of triplet states are discussed. Quenching of the triplet state of benzil by ruthenocene does not fall on the smooth curve which exists between the quenching rate constants k_q and the energy of the triplet state being quenched. Queching of triplet benzil by ruthenocene is therefore attributed to favourable charge-transfer interactions, also in this case the behaviour is analogous to quenching of triplet methylene-blue by ferrocene where at least a proportion of electron transfer following quenching has been previously established.     

Efficient Intersystem Crossing in the Tröger's Base Derived From 4-Amino-1,8-naphthalimide and Application as a Potent Photodynamic Therapy Reagent

Intersystem crossing (ISC) was observed for naphthalimide (NI)-derived Tröger's base, and the ISC was confirmed to occur by a spin-orbital charge-transfer (SOCT) mechanism. Conventional electron donor/acceptor dyads showing SOCT-ISC have semirigid linkers. In contrast, the linker between the two chromophores in Tröger's base is rigid and torsion is completely inhibited, which is beneficial for efficient SOCT-ISC. Femtosecond transient absorption (TA) spectra demonstrated charge-separation and charge-recombination-induced ISC processes. Nanosecond TA spectroscopy confirmed the ISC, and the triplet state is long-lived (46 μs, room temperature). The ISC quantum yield is dependent on solvent polarity (8–41 %). The triplet state was studied by pulsed-laser-excited time-resolved EPR spectroscopy, and both the NI-localized triplet state and triplet charge-transfer state were observed, which is in good agreement with the spin-density analysis. The Tröger's base was confirmed to be a potent photodynamic therapy reagent with HeLa cells (EC₅₀=5.0 nm ).     

Photoinduced Triplet–Triplet Energy Transfer in a 2‐Ureido‐4(1H)‐Pyrimidinone‐Bridged,Quadruply Hydrogen‐Bonded Ferrocene–Fullerene Assembly

2‐Ureido‐4(1H)‐pyrimidinone‐bridged ferrocene–fullerene assembly I is designed and synthesized for elaborating the photoinduced electron‐transfer processes in self‐complementary quadruply hydrogen‐bonded modules. Unexpectedly, steady‐state and time‐resolved spectroscopy reveal an inefficient electron‐transfer process from the ferrocene to the singlet or triplet excited state of the fullerene, although the electron‐transfer reactions are thermodynamically feasible. Instead, an effective intra‐assembly triplet–triplet energy‐transfer process is found to be operative in assembly I with a rate constant of 9.2×10⁵ s^?1 and an efficiency of 73 % in CH₂Cl₂ at room temperature.     

A GSH-responsive PET-based fluorescent probe for cancer cells imaging

An efficient PET-based probe, in which the ferrocene quencher and the naphthalimide fluorophore are linked by a disulfide bond, has been developed. This probe can be activated by GSH with fluorescence a turn-on response for blocking the PET process. In addition, it was successfully applied for distinguishing cancer cells from normal cells     

Long‐Lived Charge‐Transfer State Induced by Spin‐Orbit Charge Transfer Intersystem Crossing (SOCT‐ISC) in a Compact Spiro Electron Donor/Acceptor Dyad

We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer (³CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the ³NI* state. Then the slow secondary CS (125 ns) gives the long‐lived ³CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as ¹NI*→¹CT→³NI*→³CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory.     

Trans→cis photoisomerization of the quaternary iodides of 4-cyano- and 4-nitro-4′-azastilbene in ethanol solution: Singlet versus triplet mechanism

Quantum yield measurements have been made for the trans→cis photoisomerizations of the quaternary iodides of 4-cyano- and 4-nitro-4′-azastilbene (CP and NP, respectively) in ethanol solution at room temperature in the presence and absence of ferrocene and azulene. A triplet mechanism is suggested for the photoisomerization of NP and a singlet mechanism for that of CP. These mechanisms are supported by laser flash-photolysis studies of the trans triplet state of CP and NP as a function of temperature and quencher concentration.     

Photoinduced electron transfer competitive with energy transfer of the excited triplet state of [60]fullerene to ferrocene derivatives revealed by combination of transient absorption and thermal lens measurements

The quenching processes of the exited triplet state of fullerene (3C60) by ferrocene (Fc) derivatives have been observed by the transient absorption spectroscopy and thermal lens methods. Although 3C60 was efficiently quenched by Fc in the rate close to the diffusion controlled limit, the quantum yields (phi(et)) for the generation of the radical anion of C60 (C60*-) via 3C60 were quite low even in polar solvents; nevertheless, the free-energy changes (deltaG(et)) of electron transfer from Fc to 3C60 are sufficiently negative. In benzonitrile (BN), the phi(et) value for unsubstitued Fc was less than 0.1. The thermal lens method indicates that energy transfer from 3C60 to Fc takes place efficiently, suggesting that the excited triplet energy level of Fc was lower than that of 3C60. Therefore, energy transfer from 3C60 to ferrocene decreases the electron-transfer process from ferrocene to 3C60. To increase the participation of electron transfer, introduction of electron-donor substituents to Fc (phi(et) = 0.46 for decamethylferrocene in BN) and an increase in solvent polarity (phi(et) = 0.58 in BN:DMF (1:2) for decamethylferrocene) were effective.     

Broken symmetry in the electronic structure of the ferrocene molecule

Attempts to calculate the metal–ring distance in the ferrocene molecule using a well-tried minimal basis reveal serious deficiencies in the minimal-basis SCF model of the electronic structure of organometallics. It is found that the lowest state of the molecule in this approximation is a triplet and that there is a whole manifold of “states” in the ground-state region that have broken spatial symmetry and high-spin multiplicity.