氧在稀土酞菁上的电化学还原

过渡金属大环配合物(例如酞菁和卟啉)对氧的电化学还原具有很高的催化活性,因而是目前电化学最活跃的研究领域之一.关于氧在过渡金属大环配合物上电化学还原机理,一般认为与过渡金属的价态变化有关.近年来,由于稀土双酞菁具有电致变色(electrochromic)的特性,引起了人们极大的兴趣,并对它们的电化学行为进行了一系列的研究,但关于它们对氧的电化学还原作用却未见报道.我们利用循环伏安法研究了某些稀土单酞菁和双酞菁对氧的电化学还原的影响,并提出了氧的电化学还原的反应历程.     

稀土酞菁电致变色性质的研究

本文用循环伏安法对十三种稀土双酞菁(LnPc₂H)在邻二氯代苯中进行了研究,测定了全部氧化还原反应的半波电位(E_1/2)。由循环伏安曲线上的电化学参数及电子转移数测定结果来判断,四个氧化还原反应均为可逆(准可逆)的单电子转移过程。各种稀土双酞菁的四个反应半波电位变化规律是:随稀土离子的原子序数增大,其中二个氧化反应,E_1/2往负电位方向移动分别约为110和170mV,而对二个还原反应,轻稀土双酞普和重稀土双酞善的E_1/2各为一定值,由此可认为轻、重稀双酞善之间存在一定的差别。还测定了十三种稀土双酞普在CH₂Cl₂和DMF中氧化还原反应的半波电位,结果表明,溶剂供体数(Donor Number)的增大,溶剂化作用的加强,使得稀土双酞普二个氧化反应的半波电位往正电位方向移动。而对二个还原反应的半波电位无显著的影响。     

碘掺杂双酞菁镥结构和电学性能的研究

用饱和碘蒸气掺杂双酞菁镥(Pc2LuH)得到组成为(Pc2LuH.I6)的电荷转移复合物。碘掺杂后仍保持原来Pc2LuH分子的夹心结构, 但使沿酞菁环平面方向上彼此分子间靠近。碘未取代酞菁环上的氢; 因为酞菁配位基, 特别是氮原子向碘转移的电子, 形成I3^-,这样就有了氧化态的共轭分子和还原态的I3^-分别堆砌成两个有序的分子柱, 具备了一维导体的聚集态结构, 用夹心池样品得到ρ25℃=1.58×10^2Ω.cm, ΔE=0.1eV。     

酞菁锰络合物的电化学与光谱电化学研究

采用微电极电化学与薄层光谱电化学方法,研究了４－特丁基锰酞菁（ＴｂＰｃＭｎ）在非水溶剂中的电化学行为。结果表明,在二氯乙烷和四氢呋喃溶剂中,得到的氧化和还原过程分别对应于Ｍｎ（Ⅲ）／Ｐｃ－环阳离子自由基,Ｍｎ（Ⅲ）／Ｍｎ（Ⅱ）、Ｍｎ（Ⅱ）、Ｍｎ（Ⅱ）／Ｍｎ（Ⅰ）以及Ｍｎ（Ⅰ）／Ｐｅ环阴离子自由基的生成步骤。轴向配位效应考察表明,阴离子与锰金属中心的键合能力的顺序为：Ｃｌ＾１〉Ｉ＾－１〉ＣｌＯ４＾－     

溴代酞菁铁配合物的光谱电化学性质研究

本文对μ-氧-四溴酞菁铁配合物([TBPcFe]₂O)的电化学性质及光谱电化学性质进行了研究。结果表明,μ-氧-四溴酞菁铁在所研究的电压区问内经历了三个单电子氧化还原反应,其半波电势为0.06V,—0.75V及—1.33V(相对于甘汞电极),分别对应于Fe³⁺/Fe³⁼、Fe²⁺/Fe⁺及TBPc^2-/TBPc^3-电对的氧化还原反应。光谱电化学性质研究亦观察到相应酞菁配合物的特征光谱。     

四磺酸基酞菁锌在水和非水溶液中的电化学性质研究

在非水溶剂（二甲基亚砜（ＤＭＳＯ）及Ｎ,Ｎ－二甲基甲酰胺（ＤＭＦ））中的伏安曲线。呈现三对电流峰,表明存在三个可逆或准可逆酞菁配体的单电子转移过程,而在水溶液中则不呈现准可逆行为,且波形改变很大。此外,还比较了四磺酸基酞菁锌的水溶液在自然光和红光（６００￣７００ｎｍ）照射下的循环伏安曲线,其氧化还原峰的数目和峰电位基本不变,但在红光照射下比自然光照射下的峰电流明显增大。     

四磺酸基酞菁锌在水和非水溶剂中的电化学性质研究

在非水溶剂（二甲基亚砜（ＤＭＳＯ）及Ｎ,Ｎ＿二甲基甲酰胺（ＤＭＦ））中的伏安曲线．呈现三对电流峰,表明存在三个可逆或准可逆酞菁配体的单电子转移过程,而在水溶液中则不呈现准可逆行为,且波形改变很大．此外,还比较了四磺酸基酞菁锌的水溶液在自然光和红光（６００～７００ｎｍ）照射下的循环伏安曲线,其氧化还原峰的数目和峰电位基本不变,但在红光照射下比自然光照射下的峰电流明显增大．     

双酞菁铒的导电性

双酞菁稀土配合物具有夹心式结构,电导率较高,在有机半导体中有广阔的应用前景。作者曾测试了双酞菁稀土在酸性及碱性气氛中的电导率,发现其电阻率变化较大。用碘掺杂后电导率提高。Yamana等测得双酞菁钕在氢气和空气中的电阻率分别为1.1ΜΩ·cm和1.9ΚΩ·cm,认为双酞菁钕在空气中的低电阻率是吸附氧的缘故。但双酞菁镥在空气、     

金属酞菁敏化光还原硝基化合物的反应

本文研究了各种金属酞菁以及带有不同取代基的锌酞菁敏化光还原硝基化合物的反应。确定了光敏还原反应的主要产物是氨基和羟氨基化合物;羟氨基化合物与亚硝基化合物通过暗反应缩合生成偶氮N-氧化物。测定了它们的氧化还原电位和荧光量子产率。从敏化光还原反应的量子产率及荧光猝灭与硝基化合物浓度的依赖关系,计算出各种金属酞菁激发单重态与三重态的敏化效率。受激发金属酞菁将电子转移至硝基化合物是敏化光还原反应的起始过程。电子转移生成离子自由基对后,电荷分离与逆电子转移过程相互竞争。由于自旋选择规则的限制,激发三重态的敏化效率一般比激发单重态的敏化效率高。为了提高敏化光还原反应的效率,除选择三重态产率较高的敏化剂外,改变敏化剂的结构可提高敏化剂激发单重态的敏化效率,从而提高敏化光还原反应的量子产率.     

非水溶剂中铁酞菁的“in—situ”可见紫外光谱电化学

用循环伏安与现场可见紫外光谱电化学方法研究了氯化４－特丁基苯氧基铁酞菁［（ＴｂＰｃ）Ｆｅ（Ⅲ）Ｃｌ］电化学行为．结果表明，在四氢呋喃溶剂中其正电位区经历了两步氧化过程，对应于Ｆｅ（Ⅲ）／Ｆｅ（Ⅳ）以及Ｆｅ（Ⅳ）／阳离子自由基的生成反应，负电位区还原过程经历了Ｆｅ（Ⅲ）／Ｆｅ（Ⅱ），Ｆｅ（Ⅱ）／Ｆｅ（Ⅰ）和Ｆｅ（Ⅰ）／阴离子自由基生成的３个步骤，阐述了配位效应对氧化还原机理的影响．指出Ｆｅ（Ⅳ）不寻常价态的出现，是阴离子Ｃｌ－的轴向配位对超常价态起到稳定作用的结果．     

表面活性剂存在下铽-镥(钆、钇)-乙酰水杨酸共发荧光体系的研究

本文研究了镥等三种稀土离子与铽-乙酰水杨酸配合物产生的共发荧光效应。在最佳条件下,Lu³⁺、Gd³⁺、Y³⁺的存在可使铽-乙酰水杨酸配合物的荧光分别增强108,58和73倍。讨论了共发光体系的形成条件和荧光特性。利用Tb-Lu-乙酰水杨酸体系和Tb-Lu-乙酰水杨酸-乙二胺四乙酸-十六烷基三甲基溴化铵体系分析了合成稀土样品和包头稀土标准氧化物中的铽,结果满意,加标回收率为90.5～105.6%,并对共发光的机理和表面活性剂的作用进行了初步探讨。     

Novel non-aqueous Fe(III)/Fe(II) redox couple for the catalytic oxidation of hydrogen sulfide to sulfur by air

A series of Fe(III) salts and organic solvents have been screened to develop novel non-aqueous catalysts for the conversion of H2S to sulfur. FeCl3/95% N-methylpyrrolidinone/5% H2O was found to be a most efficient non-aqueous system. The process chemistry, the proposed mechanism of catalytic oxidation of H2S, and the electrochemistry are discussed.     

氧化镥中杂质对铈掺杂硅酸镥多晶粉体光谱性质影响

氧化镥中杂质元素对其分离制备工艺、生产成本及镥基硅酸盐闪烁晶体的性能有很大影响,但杂质元素对晶体的性质影响研究较为有限,有待进一步完善。 本文采用高温固相法制备了Lu₂O₃分离过程中关键杂质元素Yb³⁺和Ca²⁺共掺杂Lu₂SiO₅∶Ce多晶粉体,研究了Yb³⁺或Ca²⁺含量对多晶粉体光谱性质的影响,结果表明:Yb³⁺或Ca²⁺共掺并未改变发射光谱的形状和位置,随着杂质元素摩尔分数的增加,光谱强度和荧光寿命逐渐降低。     

Synthesis and Crystal Structure of［Lu（NO_3）_3（H_2O）_2（CH_3CN）］（Benzo－15－C－5）·CH_3CN

ＳｙｎｔｈｅｓｉｓａｎｄＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆ［Ｌｕ（ＮＯ_３）_３（Ｈ_２Ｏ）_２（ＣＨ_３ＣＮ）］（Ｂｅｎｚｏ－１５－Ｃ－５）·ＣＨ_３ＣＮＷａｎｇＲｕｉ－Ｙａｏ；ＪｉｎＺｈｏｎｇ－Ｓｈｅｎｇ；ＮｉＪｉａ－Ｚｕａｎ（Ｌａｂｏｒａｔｏｒｙｏ...     

Tris(oxalato)phosphorus acid and its lithium salt

The conversion of three equivalents of anhydrous oxalic acid with phosphorus pentachloride yields tris(oxalato)phosphorus acid 1, which crystallizes from diethyl ether solutions as protonated diethyl ether complex [(Et2O)2H](+)[P(C2O3)3)]-. The superacidic compound can be used as catalyst for Friedel-Crafts-type reactions. Upon neutralization with lithium hydride, the lithium salt Li[P(C2O3)3] 2 is obtained, which is highly soluble in aprotic solvents and which exhibits a wide voltage window. Thus, the lithium compound is a promising candidate as electrolyte for high performance non-aqueous batteries.     

八乙基金属卟啉的轴向配位反应研究及稳定常数测定

测定了八乙基金属卟啉 (OEP) M中当M=Zn, Cu, FeCl 或 MnCl时在CH2Cl2, N,N-二甲基甲酰胺(DMF), 二甲亚砜(DMSO), 吡啶(Py)等4种不同非水溶剂中的紫外-可见光谱, 探讨了溶剂的性质对八乙基金属卟啉光谱的影响. 结果表明八乙基锌、铁、锰卟啉在CH2Cl2中能够与配位溶剂如DMF, DMSO或pyridine 等发生轴向配位反应生成五配位或六配位的金属卟啉配合物. 用微量光谱滴定法测定了Zn、 Fe、 Mn等金属卟啉和配位溶剂发生轴向配位反应的稳定常数(logK). 讨论了中心金属离子的电负性以及配位溶剂的给电子能力对稳定常数的影响.     

Control of Chemical Reactions by Using Molecules that Buffer Non-aqueous Solutions

Control of chemical reactions is necessary to obtain designer chemical transformation products and for preventing decomposition and isomerization reactions of compounds of interest. For the control of chemical events in aqueous solutions, the use of aqueous buffers is a common practice. However, no molecules that buffer non-aqueous solutions were commonly used. Herein, we demonstrate that 1,3-cyclohexanedione derivatives have buffering functions in non-aqueous solutions. It was also shown that these molecules can be utilized to alter and control chemical reactions. 1,3-Cyclohexanedione derivatives inhibited both acid- and base-catalyzed isomerizations and decompositions in organic solvents. The reaction products obtained in the presence of the buffering molecule 2-methyl-1,3-cyclohexanedione differed from those obtained in the absence of the buffering molecule. The use of buffering molecules that work in organic solvents provides a strategy to control chemical reactions and expands the range of compounds that can be synthesized.     

Lutetium complexes with tetraphenylethylene dianion. Synthesis and structure

The reactions of dipotassium and disodium salts of the tetraphenylethylene dianion with LuCl₃(THF)₃ or CpLuCl₂(THF)₃ yielded the homoleptic ate-complexes [Na(THF)₅][Lu(Ph₂CCPh₂)₂] (1) and [K(THF)₅][Lu(Ph₂CCPh₂)₂] (2) or the heteroleptic complex CpLu(Ph₂CCPh₂)(THF)₂ (4), respectively. Recrystallization of complex 1 from a diglyme—THF mixture afforded [Na(diglyme)₂][Lu(Ph₂CCPh₂)₂](THF)_0,5 (3). Recrystallization of complex 4 from 1,2-dimethoxyethane gave [CpLu(Ph₂CCPh₂)(DME)](DME) (5). The structures of complexes 3 and 5 were established by X-ray diffraction analysis. In both complexes, the unusual η⁶-coordination of the (Ph₂CCPh₂)²⁻ dianion to lutetium is observed. The Lu-C distances vary from 2.441(2) to 2.643(2) Å (3) and from 2.470(3) to 2.763(3) Å (5). In complexes 3 and 5, a redistribution of the C-C bond lengths was observed in the Ph groups coordinated to lutetium. Studies by ¹H, ¹³C, and 2D NMR spectroscopy demonstrated that the η⁶-coordination of the tetraphenylethylene dianion in homoleptic ate-complexes 1 and 2 is retained in a THF solution, whereas the coordination of this dianion in heteroleptic complex 4 changes from η⁶ to η⁴.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2060–2068, October, 2004.     

H2 evolution and molecular electrocatalysts: determination of overpotentials and effect of homoconjugation

In an effort to standardize the determination of overpotential values for H(2)-evolving catalysts in non-aqueous solvents and allow a reliable comparison of catalysts prepared and assayed by different groups, we propose to adopt the half-wave potential as reference potential. We provide a simple method for measuring it from usual stationary cyclic voltammograms, and we derive the formulas to which the measured potential should be compared, taking into account the effect of homoconjugation. We also revisit tabulated values of the standard reduction potential of protons in nonaqueous solvents, E(H+/H(2))°.     

Initial growth of lutetium(III) bis-phthalocyanine on Ag(111) surface

The adsorption of lutetium(III) bis-phthalocyanine (LuPc(2)) on Ag(111) was investigated using scanning tunneling microscopy and spectroscopy (STM/STS). A comprehensive study was carried out toward understanding the driving mechanism responsible for the formation of the first and second monolayers (MLs). In both MLs, the adsorbed molecules are found to exhibit different in-plane orientations arranged according to a "chess-board" like pattern. Highly resolved STM images allowed an exact determination of the corresponding angle mismatch, which differs for the first and second MLs. The tunneling transport through individual molecules reveals a negative differential resistance (NDR) effect detectable within the current-voltage curves. The corresponding density of states (DOS) representation is consistent with a resonant tunneling mechanism sustained by the valence band (VB) states close to the Fermi energy (E(F)) recorded via highly resolved ultraviolet photoemission spectroscopy (UPS).