水溶性苝醌衍生物(13-SO~2Na-DDHA)与胶体半导体(CdS)澡光 诱导电子传递过? 痰亩ρа芯?

根据非均相体系电子传递动力μ＜0(μ=E~s*/s+-E~CB)的原理,构建出相匹配的水溶性苝醌衍生物光敏剂(13-SO~2Na-DDHA)与胶体半导体(CdS)的复合体体系,? 獯忝鸱椒ǎ獬鏊侵浜捅砉劢岷铣Ｊ?K~app)为1480(mol/L)^-1。继而? τ孟孕?spincounteraction)的ESR技术,首次定量地研究了它们之间的光诱? 嫉绱莨痰亩ρВ范耸?3-SO~3Na-DDNA光敏化作用的CdS胶体半导体表? 婀饣乖ρХ匠毯退俾食Ｊ峁⑾郑诒咎逑抵蠺EMPO接受光电子的反应? 妒?,而不同于均相体系中的反应级数别虽在相同可见光照射条件下(13-SO~2Na-DDHA)复合体的光还原速率比单独CdS高约82倍,表明该水溶性光敏剂对CdS胶体半导体具有显著的敏化效果,在太阳能应用中可被用作CdS胶体半导体有效的敏化剂。     

水溶性苝醌衍生物(13-SO3Na-DDHA)与胶体半导体(CdS)间光诱导电子传递过程的动力学研究

根据非均相体系电子传递动力μ＜0(μ=Es*/s+-ECB)的原理,构建出相匹配的水溶性苝醌衍生物光敏剂(13-SO3Na-DDHA)与胶体半导体(CdS)的复合体体系,通过荧光淬灭方法,测出它们之间的表观结合常数(Kapp)为1480(mol/L)-1.继而应用消自旋(spin counteraction)的ESR技术,首次定量地研究了它们之间的光诱导电子传递过程的动力学,确定了受13-SO3Na-DDHA光敏化作用的CdS胶体半导体表面光还原动力学方程和速率常数,结果发现,在本体系中TEMPO接受光电子的反应级数为0,而不同于均相体系中的反应级数;特别是在相同可见光照射条件下,CdS-(13-SO3NA-DDHA)复合体的光还原速率比单独CdS高约82倍.表明该水溶性光敏剂对CdS胶体半导体具有显著的敏化效果,在太阳能应用中可被用作CdS胶体半导体有效的敏化剂.     

硫化镉光催化氧化二苯甲醇的反应及二次电子转移在反应中的作用

本文报道紫精化合物及亚硫酸盐在硫化镉光催化氧化二苯甲醇及其它芳香醇反应中的作用。认为紫精化合物通过二次电子转移作为反应中负氧离子(O2^-)的中继体, 亚硫酸盐通过与硫化镉的价带发生电子转移作用减少光生电子-空穴对的复合, 提高半导体的光催化效率, 同时对硫化镉的腐蚀有抑制作用, 认为提高半导体光催化效率的途径在于有效地促使光生电荷分离。     

Photoinduced electron transfer between adamantanamine-(OCH2CH2)n-phenothiazine and mono-6-p-nitrobenzoyl-β-cyclodextrin

A series of adamantanamine-(OCH₂CH₂)_n-phenothiazine (n = 0, 1, 2, 3) electron donors was synthesized. Photoinduced electron transfer was observed in the supramolecular complex of the phenothiazine derivatives with p-nitrobenzoyl-β-cyclodextrin (NBCD) through binding of the adamantyl group by the NBCD cavity, which is stabilized clearly via hydrophobic interactions in aqueous solution. Detailed Stern–Volmer constants were measured and they were partitioned into dynamic Stern–Volmer quenching constants and static binding constants. The results revealed an efficient electron transfer process inside the supramolecular systems compared to that controlled by diffusion. This observation also indicates that the chain length will influence the electron transfer efficiency of a supramolecular donor–acceptor system.     

四氰基乙烯-四甲基乙烯体系光诱导电子转移双势阱的从头算研 究

以两态模型为基础,用从头算方法,在DZP[所有原子带极化函数的Dunning(9s,5p)/(3s,2p)]基组水平上对四氰基乙烯与四甲基乙烯间的电子转移进行理论计算。通过孤立给体和受体的几何构型优化,计算了给体的电离能和受体的电子亲和能。计算表明,在光诱导电荷分离之后的返回电子转移处于高放热的Marcus反转区。通过碰撞配合物的结构优化和电荷分离处理,在线性反应坐标近似下得到四甲基乙烯-四氰基乙烯配合物电荷分离反应的双势阱,进而获得反应热,键重组能,以及跃迁能。     

Magnetic field effect on photoinduced electron transfer between [Cu(phen)2]2+ and DNA

The magnetic field effect (MFE) on the photoinduced electron transfer (PET) reaction between the [Cu(phen)2]2+ complex and DNA has been studied in homogeneous buffer medium and in reverse micelles. The copper complex on photoexcitation can oxidize DNA in a deoxygenated environment. A prominent MFE is found even in a homogeneous aqueous medium for the triplet born radicals. The process of partial intercalation of [Cu(phen)2]2+ complex within DNA is responsible for such a rare observation. In reverse micelles, the MFE is not very much prominent because of the large separation distance between the component radicals of the geminate radical ion pairs generated through PET.     

A fluoran-based fluorescent probe via a strategy of blocking the intramolecular photoinduced electron transfer (PET) process

A novel fluoran-based fluorescent probe 2 has been designed and synthesized by using a strategy of blocking the intramolecular photoinduced electron transfer (PET) process. The probe keeps a ring-closed spirolactone structure in aqueous buffer solution. However, the oxidation of the probe by ClO^? perturbs a new equilibrium of the structural interconversion between the nonfluorescent spirolactone and the fluorescent ring-opened zwitterion, which generates a highly selective fluorescent probe for ClO^?. Meanwhile, the probe is cell membrane permeable and can be utilized as fluorescent probe for imaging ClO^? in living cells.     

Generation of ketyl radical anions by photoinduced electron transfer (PET) between ketones and amines. Synthetic applications

Photoreduction of ketones in the presence of amines led to ketyl radicals through photoinduced electron transfer (PET). Tertiary amines, such as triethylamine (Et₃N) have frequently been used in these reactions. Different reactions can occur from ketyl radicals such as photoreduction, coupling reactions, additions on activated double bonds, cyclizations, bond cleavage of strained rings, tandem reactions such as cyclization-ring opening or ring opening-cyclization.     

Syntheses and remarkable photophysical properties of 5-(2-pyridyl) pyrazolate boron complexes; photoinduced electron transfer

A new series of pyridyl pyrazolate boron complexes 2a-e have been synthesized, in which 2a-c exhibit remarkable dual fluorescence properties due to the photoinduced electron transfer reaction.     

Wavelength-dependent photochemistry in Cr(CNPh)6: a study of photosubstitution and photoinduced electron transfer using time-resolved spectroscopy

The wavelength dependence of photosubstitution, photoinduced electron transfer, and the time-resolved spectra of Cr(CNPh)6, a compound having low-lying MLCT states, were investigated. Photosubstitution quantum yields increase with increasing excitation energy while photoinduced electron transfer quantum yields decrease with increasing excitation energy. At the lowest excitation energy used (532 nm, or 18,800 cm(-1)), the quantum yields for both electron transfer and photosubstitution reach the same maximum value, 0.29. Picosecond time-resolved absorption spectra at 355 and 532 nm excitation wavelengths show two features: a bleach signal centered at 400 nm and an excited state absorption (ESA) in the 600 nm region. The ESA signal is much weaker for 532 nm excitations than for 355 nm excitations. Following a 355 nm flash, the bleach and ESA decay exponentially with the same lifetime of 23 micros. This implies a simple ligand dissociation followed by recombination. Bleach recovery kinetics after a 532 nm flash are more complicated: two or three exponential components are required to fit the data. Cr(CNPh)6 exhibits two photochemical mechanisms: at high excitation energy, a simple charge neutral dissociation occurs; at low energy, it is proposed that a phenylisocyanide radical anion dissociates, forming a radical pair that is responsible for the observed substitution and electron transfer reactivity, and the complicated nanosecond kinetics. The primary processes for both reactions occur in less than 20 ps.     

Electroanalytical,kinetic, and mechanistic investigations of coordination-inspired electron transfer between Fe(II)/Cu(II)

Herein, we report that the thermodynamic barrier for solution-phase electron transfer (ET) between Cu(II) and Fe(II) in aqueous acidic media can be overcome through the addition of 2,9-dimethyl-1,10-phenanthroline (Neocuproine [NC]) to the reaction mixture. A detailed discussion of the kinetic and mechanistic aspects of this coordination-inspired ET is presented. We attribute the observed change in the thermodynamic feasibility to the change in the reduction potential of Cu(II)–Cu(I) couple on its ligation with NC. The reaction was found to be slow, following first-order kinetics with respect to each Cu(II) and Fe(II). In the presence of excess NC, the reaction was observed to proceed with a pseudo-second-order rate constant of 3.37?±?0.05?dm³?mol^?1?s^?1 at 298?K, with an activation barrier of ca. 26.22?kJ?mol^?1. The slow reaction is attributed to the significant reorganization energy associated with large-scale changes in the coordination sphere of the oxidant. A two-step mechanism that explains the experimental observations is proposed for the investigated reaction.