羧脒盐桥介导的单重态能量传递直接观察

设计构建了以羧脒盐桥联接的萘和蒽超分子组装体系,NA-(脒基-羧基)-An以及相应的模型体系.稳态和时间分辨荧光光谱研究表明,置于羧脒盐桥两端的萘和蒽基团之间发生了从萘到蒽的单重态能量传递,NA-(脒-羧)-An超分子体系中单重态能量传递效率和速率常数分别大于0.99和9.9×10⁹s^-1.推测羧脒盐桥介导了体系中的单重态能量传递过程,单重态能量传递‘通过键’以电子交换机制进行.     

2-脲基-4[1氢]-嘧啶酮四氢键萘-蒽超分子组装体系:"通过键"机制的单重态能量传递

设计合成了基于2-脉基-4[1氢]-嘧啶酮AADD四氢键萘-葱超分子组装体系UPNa·UPAn.稳态和时间分辨荧光光谱研究表明UPNa·UPAn四氢键组装体可以发生从茶到葱的高效、快速的单重态能量传递过程.体系内光诱导单重态能量传递的速度和效率远大于通过F(o)rster机制的单重态能量传递速率,表明组装体系UPNa·...     

冠醚连接的给体-受体化合物中分子内远程三重态能量传递

本文合成了用冠醚连接的二苯酮基(给体)和萘基(受体)的二元化合物,用稳态和时间分辨光谱研究了该化合物分子内远程三重态能量传递,证实当冠醚络合钠离子以后,可以发生有效的分子内远程三重态能量传递,对传递机制进行了讨论。     

基于碘代Bodipy超分子聚合物的构筑和光物理性能研究

本文以对羟基苯甲醛和3-溴丙炔为原料,经过巯基-炔基点击化学反应成功合成了含有双四重氢键的2,6-二碘代-8-[4-(2-脲基-4[1H]-嘧啶酮)苯基]-氟化硼二吡咯甲川化合物(IBodipy-BisUPy),并对其进行了详细的结构表征以及紫外、荧光、瞬态吸收、低温磷光等光物理性质测试。I-Bodipy-BisUPy可通过四重氢键非共价键作用驱动形成超分子聚合物。重原子碘的存在促进了I-Bodipy-BisUPy从单重激发态向三重激发态的系间窜越,可在低温下呈现一个近红外磷光发射峰,其三重态的寿命为56.7μs。利用微乳法将超分子聚合物制备成纳米颗粒,ESR和对1,5-二羟基萘的光敏氧化性能测试表明此超分子聚合物纳米颗粒可在水中产生单重态氧(1O2),且能够实现对底物的光敏氧化。     

SiCS分子结构及其稳定性的理论研究

采用DFT,QCISD及CCSD(T)方法对单重态、三重态SiCS的分子体系势能面进行理论计算,在QCISD/6-311G(d)水平上得到由3个过渡态连接的5个稳定构型.经动力学及热力学分析均是稳定的三重态线型分子SiCS(³1)、单重态线型分子SiCS(¹1)以及单重态的环状分子cSiCS(¹2).     

高分子三线态敏化剂分子中能量迁移的研究 Ⅰ.聚(乙烯基二苯酮-β-乙烯基萘)中的能量迁移的研究

本工作对乙烯基二苯酮-β-乙烯基萘共聚物体系分子内的能量迁移和转移进行了研究.在77K玻璃态溶液中,不论以310nm或以370nm波长激发时,共聚物都发生强的萘燐光.各共聚物三线态能量转移量子效率φ_(ET)~(T-T)大于80％,表明此高分子体系能有效地进行三线态能量迁移和转移.     

疏水作用对光化学和光物理过程的影响——Ⅸ.长链分子的簇集对β-萘甲酸烷基酯和脂肪酸9-蒽甲醇酯间能量传递的增强作用

在二甲基亚砜-水(DMS0-H_2O)混合溶剂中,长链β-萘甲酸烷基酯(A_n)、长链脂肪酸9-蒽甲醇醣(E_n)和长链饱和烷烃(C_n)相互簇集形成共簇集体,A_n通过共振机制向E_n进行单重态能量传递。在每个簇集体含近一个给体分子和一个受体分子的情况下,能量传递效率高达50％。簇集体内能量传递的速度比簇集体间的大一个数量级。A_n激基缔合物也可向E_n进行能量传递,但效率很低。由于形成激基缔合物的过程与能量传递过程相互竞争,激基缔合物的形成降低了能量传递的效率。     

疏水作用对光化学和光物理过程的影响 ⅩⅢ.△5雄甾-3β-(1-萘乙酰)-17-丹酰酯在不良溶剂中的簇集和分子间能量传递

在二甲基亚砜-水(DMSO-H₂O)混合溶剂中,随着水的体积分数(Φ)增大,△⁵雄甾-3β-(1-萘乙酰)-17-丹酰酯(1)分子中丹酰基荧光峰逐渐红移,但当Φ>0.4时,丹酰基荧光峰突然由550 nm移至500 nm。表明1发生了簇集。用280 nm光激发时,伴随丹酰基荧光的蓝移,萘基的荧光明显降低,丹酰基的荧光增强,表明簇集体内1的分子相互靠近,有利于萘基向丹酰基进行分子间的能量传递。萘基向丹酰基进行能量传递的效率在簇集体外和簇集体内分别为18%和90%。荧光寿命的测定和使用不同激发波长的实验表明簇集发生后,仍有部分分子未发生簇集。     

疏水作用对光化学和光物理过程的影响IX. 长链分子的簇集对β-萘甲酸烷基酯和脂肪酸9-蒽甲醇酯间能量传递的增强作用

在二甲基亚砜-水(DMSO-H2O)混合溶剂中, 长链β-萘甲酸烷基酯(An)、长链脂肪酸9-蒽甲醇酯(En)和长链饱和烷烃(Cn)相互簇集形成共簇集体, An通过共振机制向En进行单重态能量传递, 在每个簇集体含近一个给体分子和一个受体分子的情况下, 能量传递效率高达50%,簇集体内能量抟递的速度比簇集体同的大一个数量级, An激基缔合物也可向En进行能量传递, 但效率很低, 由于形成激基缔合物的过程与能量传递过程相互竞争, 激基缔合物的形成降低了能量传递的效率。     

疏水作用对光化学和光物理过程的影响IX. 长链分子的簇集对β-萘甲酸烷基酯和脂肪酸9-蒽甲醇酯间能量传递的增强作用

在二甲基亚砜-水(DMSO-H2O)混合溶剂中, 长链β-萘甲酸烷基酯(An)、长链脂肪酸9-蒽甲醇酯(En)和长链饱和烷烃(Cn)相互簇集形成共簇集体, An通过共振机制向En进行单重态能量传递, 在每个簇集体含近一个给体分子和一个受体分子的情况下, 能量传递效率高达50%,簇集体内能量抟递的速度比簇集体同的大一个数量级, An激基缔合物也可向En进行能量传递, 但效率很低, 由于形成激基缔合物的过程与能量传递过程相互竞争, 激基缔合物的形成降低了能量传递的效率。     

Through-bond excited energy transfer mediated by an amidinium-carboxylate salt bridge in Zn-porphyrin free-base porphyrin dyads

Excited energy-transfer processes were investigated for a supramolecular Zn-porphyrin free-base porphyrin dyad, ZnPA-2 x FbPC-2, in which beta-octaalkylated meso-diarylporphyrins are connected through an amidinium-carboxylate salt bridge. The rate of energy transfer in the dyad (1.3 x 10(9) s(-1)) is substantially slower than that in the previously reported dyad, ZnPA-1FbPC-1 (4.0 x 10(9) s(-1)), in which meso-tetraarylporphyrins are connected through the same amidinium-carboxylate salt bridge. The F?rster-type mechanism can explain only minor parts of these rates (3.3 x 10(8) and 5.1 x 10(8) s(-1), respectively). Thus, Dexter-type through-bond energy transfer may be invoked. Indeed, bridge-mediated electronic processes would be favored in ZnPA-1 x FbPC-1 over ZnPA-2 x FbPC-2 on the basis of steric and electronic factors. Sterically, the phenyl groups in ZnPA-2 and FbPC-2 are more closely perpendicular to the porphyrin planes than those in ZnPA-1 and FbPC-1. Electronically, the energy and symmetry of the occupied frontier orbitals should favor ZnPA-1 x FbPC-1 over ZnPA-2 x FbPC-2 in terms of electronic interactions through the bridge. Therefore, the observed trend (ZnPA-1 x FbPC-1>ZnPA-2 x FbPC-2), consistent with these considerations, lends further support to the through-bond mechanism. Thus, the amidinium-carboxylate salt bridge is effective in mediating through-bond energy transfer even though the bond is noncovalent.     

Remote Sensitized Photoisomerization via Through‐Bond Triplet–Triplet Energy Transfer Mediated by a Salt Bridge in a Supramolecular Dyad

A supramolecular dyad, BP‐(amidinium‐carboxylate)‐NBD is constructed, in which benzophenone (BP) and norbornadiene (NBD) are connected via an amidinium‐carboxylate salt bridge. The photophysical and photochemical properties of the assembled BP‐(amidinium‐carboxylate)‐NBD dyad are examined. The phosphorescence of the BP chromophore is efficiently quenched by the NBD group in BP‐(amidinium‐carboxylate)‐NBD via the salt bridge. Time‐resolved spectroscopy measurements indicate that the lifetime of the BP triplet state in BP‐(amidinium‐carboxylate)‐NBD is shortened due to the quenching by the NBD group. Selective excitation of the BP chromophore results in isomerization of the NBD group to quadricyclane (QC). All of these observations suggest that the triplet–triplet energy transfer occurs efficiently in the BP‐(amidinium‐carboxylate)‐NBD salt bridge system. The triplet–triplet energy transfer process proceeds with efficiencies of approximately 0.87, 0.98 and the rate constants 1.8×10³ s^?1, and 1.3×10⁷ s^?1 at 77 K and room temperature, respectively. The mechanism for the triplet–triplet energy transfer is proposed to proceed via a “through‐bond” electron exchange process, and the non‐covalent bonds amidinium‐carboxylate salt bridge can mediate the triplet–triplet energy transfer process effectively for photochemical conversion.     

Intramolecular energy transfer between chromophores separated by a rigid steroid bridge: II. Energy transfer as a probe to determine the ratio of two epimers

The singlet-singlet intramolecular energy transfer between naphthalene moiety and dansy! group held apart by a rigid steroid bridge was investigated for two molecules: β-(1-naphthyl) acetoxy-17α-dansyl-Δ⁵androstene (3a) and 3β-(1-naphthyl)acetoxy-17 β-dansyl-Δ⁵androstene (3b). The rates of energy transfer for 3a and 3b in cyclohexane are 6.9 × 10⁶ and 1.1 × 10⁸ s^?1 respectively. The difference in energy transfer rate between 3a and 3b is attributed to the different donor-acceptor separation and orientation. The ratio of the two epimers in the synthesized product mixture was obtained from the fluorescence decay measurements.     

由己二酸根桥联的新颖双U形四核铜配合物: [Cu4(phen)4(NO3)2(H2O)2(adip)4/4(Hadip)4/2](NO3)2•2H2O

邻菲罗啉、己二酸和硝酸铜在水溶液中反应得到一种新颖的四核铜配合物[Cu4(phen)4(NO3)2(H2O)2- (adip)4/4(Hadip)4/2](NO3)2•2H2O (其中H2adip＝己二酸), 并经元素分析, IR, UV, TG和X射线单晶衍射分析表征. 该配合物晶体属三斜晶系, 空间群, a＝1.0146(2) nm, b＝1.0261(2) nm, c＝1.8285(4) nm, α＝91.66(3)°, β＝92.19(3)°, γ＝112.76(3)°, V＝1.7520(6) nm3, Z＝1, Dc＝1.639 g/cm3, C66H66Cu4N12O28, Mr＝1729.47, F(000)＝886, μ＝1.294 mm－1, R1和wR2分别为0.0447和0.1141. 己二酸根通过4个羧基O将两个U形双核亚单元联接成具有一个对称中心的双U形四核结构, 其中每个U型亚单元包含晶体学上不对称的2个Cu(II)原子. 每个Cu(II)离子均处于畸变的四方锥配位环境, 除与己二酸氢根(Hadip)、己二酸根(adip)和邻菲罗啉(Phen)的N, O配位形成锥底平面外, 其中的1个Cu(II)与水配位, 而另一个Cu(II)则与硝酸根配位. 配合物晶体结构中存在着广泛的氢键和p×××p作用.     

纳米CdS与明胶蛋白质的相互作用

利用荧光光谱和紫外-可见吸收光谱研究了pH＝12.0及不同温度下, CdS纳米晶与明胶结合反应的光谱行为, 实验发现在明胶溶液中CdS的生成对明胶的内源荧光有较强的猝灭作用. 用Lineweave-Burk方程处理实验数据, 发现CdS与明胶发生反应生成了配合物, 结合红外和紫外-可见吸收光谱结果, 属于静态荧光猝灭; 计算了不同温度下反应的结合常数K (285 K: 1.07×104 L•mol－1; 292 K: 9.69×103 L•mol－1; 299 K: 8.06×103 L•mol－1)及对应温度下结合反应的热力学参数(ΔrHm＝－14.18 kJ•mol－1; ΔrGm＝－21.98/－22.28/－22.36 kJ•mol－1; ΔrSm＝27.36/27.74/27.36 J•K－1•mol－1), 证明二者主要靠静电作用力结合. 根据Förster的偶极-偶极非辐射能量转移原理计算出结合位置距离色氨酸残基4.09 nm, 发生分子内的非辐射能量转移. 为探讨纳米颗粒与此类生物大分子之间相互作用的化学机制提供了重要的信息.     

Molecular-wire behavior of OLED materials: exciton dynamics in multichromophoric Alq3-oligofluorene-Pt(II)porphyrin triads

Donor-bridge-acceptor triads consisting of the Alq3 complex, oligofluorene bridge, and PtII tetraphenylporphyrin (PtTPP) were synthesized. The triads were designed to study the energy level/distance-dependence in energy transfer both in a solution and in solid state. The materials show effective singlet transfer from the Alq3-fluorene fluorophore to the porphyrin, while the triplet energy transfer, owing to the shorter delocalization of triplet excitons, appears to take place via a triplet energy cascade. Using femtosecond transient spectroscopy, the rate of the singlet-singlet energy transfer was determined. The exponential dependence of the donor-acceptor distance and the respective energy transfer rates of 7.1 x 1010 to 1.0 x 109 s-1 with the attenuation factor a of 0.21 +/- 0.02 A-1 suggest that the energy transfer proceeds via a mixed incohererent wire/superexchange mechanism. In the OLEDs fabricated using the Alq3-oligofluorene-PtTPP triads with better triplet level alignment, the order of a magnitude increase in efficacy appears to be due to facile triplet energy transfer. The devices, where the triplet-triplet energy transfer is of paramount importance, showed high color purity emission (CIE X,Y: 0.706, 0.277), which is almost identical to the emission from thin films. Most importantly, we believe that the design principles demonstrated above are general and may be used to prepare OLED materials with enhanced quantum efficacy at lowered operational potentials, being crucial for improved lifespan of OLEDs.     

Direct observation of the intramolecular triplet-triplet energy transfer in poly(aryl ether) dendrimers

A series of benzophenone (BP) and naphthalene (NA) labeled poly(aryl ether) dendrimers (BP-Gn-NA), generations 1-4, were synthesized, and their photophysical properties were examined. Flash photolysis demonstrates that the triplet energy in BP-Gn-NA can be transferred from the peripheral BP chromophores to the core NA group with the efficiencies of ca. 0.97, 0.96, 0.88, and 0.54 and with the rate constants of 1.4x10(8), 1.2x10(8), 9.5x10(7), and 1.3x10(7) s-1 at room temperature for generations 1-4, respectively. The transient absorption spectra of BP-Gn-NA show clearly the formation of the triplet NA absorption along with the decay of the triplet BP one with an isosbestic point at 475 nm, which gives direct evidence of the triplet energy transfer from the periphery BP chromphores to the core NA group. The phosphorescence of the NA group attached to the focal point was observed when the periphery BP chromophores were selectively irradiated in BP-G1-NA at 77 K. The triplet energy transfer occurs at 77 K with the efficiencies of 1.0, 0.16, 0.17, and 0.21 for generations 1-4, respectively. The intramolecular triplet energy transfer is proposed to proceed mainly via a through space mechanism.     

Benzophenone and zinc(II) phthalocyanine dichromophores-labeled poly (aryl ether) dendrimer: synthesis,characterization and photoinduced energy transfer

A series of benzophenone chromospheres and zinc(II) phthalocyanine dichromophores labeled poly (aryl benzyl ether) dendrimer (G_n-DZnPc(BP)_8n, n = 1?2) were synthesized. Their structures were characterized by elemental analysis, ¹H NMR, IR, UV–vis and matrix-assisted laser desorption/ionization time-of-flight spectrometry (MALDI-TOF MS). Their photophysical properties were examined by steady-state and time-resolved fluorescence methods. Both the poly (aryl benzyl ether) dendrimer and BP terminal chromophores had a significant effect on photophysical properties of the zinc(II) phthalocyanine core. Time-resolved spectroscopic measurements indicated that the lifetime of benzophenone (donor) chromophore was longer than that of the zinc(II) phthalocyanine (acceptor). The fluorescence of the peripheral benzophenone chromophores was quenched by the phthalocyanine group attached to the focal point. All of these observations suggest that an intramolecular singlet energy transfer occurs in G_n-DZnPc(BP)_8n molecules. The light-harvesting abilities of these molecules increased with generations due to an increase in the number of benzophenone chromophores. The energy transfer efficiencies were ca. 0.49 and 0.68 for generations 1 and 2, respectively, and the rate constants of the singlet-singlet energy transfer were ca. 10⁸ s^?1. The rate constants changed inconspicuously with increase of dendron generations. The intramolecular singlet-singlet energy transfer is proposed to proceed mainly via a Förster-type interaction mechanism involving the dendrimer backbone as a scaffold to hold the peripheral benzophenone chromophores and the phthalocyanine core together. This dendrimer was an effective new energy transmission complex with high efficiency and could be used as a potential light-harvesting system.     

PHOTOCHEMISTRY OF POLYFUNCTIONAL MOLECULES. DEVELOPMENT OF ANTENNA CHROMOPHORES FOR SELF-SENSITIZED PHOTOREDUCTION OF KETONES*

–Model systems are reported which test the efficacy of potential aryl antenna groups designed to harvest photons and subsequently transfer electronic energy to a target ketone through singlet-singlet energy transfer. The model series consists of 4-aryl substituted cyclohexanones where the aryl groups are benzyloxy ( 5a ), benzoyl ( 5b ), and dimethylphenylsiloxy ( 5c ). In each case, photolysis of isopropyl alcohol solutions of the substrate with 254 nm light results in photoreduction of the ketone to the corresponding alcohols, 6a-6c . The most efficacious sensitizing antennae are the benzyloxy and dimethylphenylsiloxy chromophores, with quantum efficiencies for reduction equal to 0.57 and 0.48, respectively. Photophysical and photochemical studies on 5a confirm that energy transfer to the ketone is intramolecular with the rate constant for energy transfer estimated at 2.4 × 10⁰ s^-1.