三线态二苯基卡宾的动力学稳定效应

通过对二苯基重氮甲烷进行光照射产生了一系列于邻位和对位具有不同大小取代基的三线态二苯基卡宾.用紫外可见光谱对其进行了直接观察,并利用激光闪光光解法测定了三线态二苯基卡宾在室温脱氧苯溶液中的寿命,由此表明在邻位和对位里引入庞大的取代基对三线态二苯基卡宾具有更好的稳定效应.     

二苯基卡宾反应性的取代基效应

用激光闪光光解法对室温溶液中产生的三线态二苯基卡宾进行了直接观察,并通过对产生的三线态二苯基卡宾寿命的测定以及与氧气反应速率常数的考察,就邻位及对位的取代基效应进行了初步探讨。     

二（2,6-二甲基-4-甲氧基）苯基卡宾的产生和反应

为了考察卡宾稳定性的电子效应,合成了对位具有强推电性甲氧基的二（2, 6-二甲基-4-甲氧基）苯基重氮甲烷(1c),通过光分解而产生了二（2,6-二甲基- 4-甲氧基）苯基卡宾(2c)。分别用电子顺磁共振（EPR）光谱,紫外可见(UV/vis) 光谱及激光闪光光分解法对二（2,6-二甲基-4-甲氧基）苯基卡宾(2c)的产生和衰 减过程进行了详细的观察。由于甲氧基的强推电子作用使二苯基卡宾的稳定性大大 降低,其二次动力学衰减速度常数为130s~(-1),是对位非取代二苯基卡宾(2b) (14s~(-1))的约9倍,且室温苯溶液中的寿命为20ms,仅为2b(180ms)的1/9。且通过 产物分析对二（2,6-二甲基-4-甲氧基）苯基卡宾(2c)的反应及甲氧基的取代基效 应进行了详细探讨。     

氮自由基热力学稳定性的双取代基效应

通过利用热力学循环估测气相均裂键能 (BDE)的方法 ,考察了 48个含N H键的化合物 (GNHG′)的BDE数值 ,较系统地研究了双取代基对氮自由基热力学稳定性的影响 .结果表明 ,氮自由基上的双取代基效应的表现形式与碳自由基有所不同 .一般来说 ,由于饱和效应 ,第 2个取代基对自由基稳定性的影响会有所减弱 ;但当带有可形成三电子键的供电子基 (如 ,NH2 ,OH等 )或可形成“离域通道”的拉电子基 (如 ,Ph3 P+)时 ,双取代基会对氮自由基发生协同作用 ,即产生“协稳定效应” .     

1,3-二(2,6-二甲基苯基)-2-四氢咪唑基-苯亚甲基-二吡啶基-二氯合钌化合物的合成

设计了由1,3-二(2,6-二甲基苯基)-2-四氢咪唑基-苯亚甲基-三苯基膦-二氯合钌(7)和吡啶反应生成无膦型金属钌卡宾化合物1,3-二(2,6-二甲苯基)-2-四氢咪唑基-苯亚甲基-2-吡啶基-二氯合钌(8),8作为高效催化剂用于丙烯腈和烯丙基苯的交叉交互置换反应.新化合物7,8经核磁共振氢谱、碳谱和高分辨率质谱予以证实.     

双(1,2-二苯基环戊二烯基)二氯化锆化合物发光光谱行为及取代基效应

以干燥的正己烷为溶剂, 在N2气保护下, 研究了金属有机化合物双(1,2-二苯基环戊二烯基)二氯化锆(2)、 双(4-甲基-1,2-二苯基环戊二烯基)二氯化锆(3)和双(1,2,4\|三苯基环戊二烯基)二氯化锆(4)的发光光谱行为. 研究结果表明, 该系列化合物具有良好的发光性能, 且荧光光谱的发射波长可通过改变环戊二烯基4位上的取代基R进行调节. 发射光波长大小顺序为Ph>CH3>H.     

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.     

苯环上氯原子的不同取代位置对四苯基锌卟啉-酪氨酸光物理性质的影响

稳态紫外光谱、荧光光谱和时间分辨荧光光谱显示,苯环上氯原子的不同位置对氯苯基锌卟啉-酪氨酸的光物理性质有很大影响.紫外吸收光谱中,邻、间和对氯取代的3个化合物都具有典型的Soret带和Q带.其中Soret带位于423nm处,Q(0,0)和Q(0,1)带分别位于549和590nm处.邻位取代化合物的荧光量子产率为0.058,比间位(0.0241)、对位(0.0235)取代化合物的要高得多.邻位取代化合物的荧光寿命(3.11ns)比间位(1.12ns)和对位(1.11ns)取代化合物的长.邻位化合物的这些特性可能归因于取代基之间的空间效应;而在间位和对位化合物中,重原子效应和吸电子的诱导效应可能起主导作用.     

在离子液体体系中苯环上氯取代基电子效应差异性研究

在1-丁基-3-甲基咪唑四氟硼酸盐([Bmim]BF4)离子液体中,研究不同取代基的苯氧负离子与溴代异丙烷亲核取代反应及不同取代基的苯甲醛与脲、乙酰乙酸乙酯亲核加成反应活性,通过测定反应转化率获得离子液体体系中不同取代基的电子效应.研究发现氯取代基表现出推电子性质,进而提出在离子液体体系中带苯环结构的反应物可与含杂芳环离子液体形成多层大π配合物结构,大π配合物影响了极性基团的正常溶剂化效应形成,产生独特的离子层溶剂效应.     

取代基结构对聚[(3-烷基)噻吩-2,5]-取代苯甲烯衍生物三阶非线性光学性能的影响

采用3-烷基噻吩与对硝基苯甲醛和对二甲氨基苯甲醛的聚合反应得到了5种聚(3-烷基)噻吩取代苯甲烯衍生物:聚(3-丁基)噻吩对硝基苯甲烯(PBTNBQ)、聚(3-己基)噻吩对硝基苯甲烯(PHTNBQ)、聚(3-丁基)噻吩对二甲氨基苯甲烯(PBTDMABQ)、聚(3-己基)噻吩对二甲氨基苯甲烯(PHTDMABQ)和聚(3-辛基)噻吩对二甲氨基苯甲烯(POTDMABQ).计算其光学禁带宽度分别为PBTNBQ(1.82eV),PHTNBQ(1.85eV),PBTDMABQ(1.71eV),PHTDMABQ(1.78eV)和POTDMABQ(1.67eV).利用简并四波混频技术测量了5种聚合物薄膜的三阶非线性极化率,分别为1.74×10^-8,1.82×10^-8,5.62×10^-9,8.64×10^-9和1.22×10^-8esu,均具有较大的三阶非线性光学性能.针对取代基结构对聚(3-烷基)噻吩取代苯甲烯衍生物的三阶非线性光学性能的影响从分子内极化程度和主链电子的离域程度两个方面进行了讨论.     

Triplet diphenylcarbenes protected by (trimethylsilyl)ethynyl groups

(2,4,6-Tribromophenyl)(4-tert-butyl-2,6-dimethylphenyl)diazomethane (1a) was shown to be stable enough to survive Sonogashira coupling reaction conditions at an elevated temperature and gave not only a para-monosubstituted product, (4-trimethylsilylethynyl-2,6-dibromophenyl)(4-tert-butyl-2,6-dimethylphenyl)diazomethane (1b), but also a disubstituted one, [2,4-bis(trimethylsilylethynyl)-6-bromophenyl](4-tert-butyl-2,6-dimethylphenyl)diazomethane (1c), and a trisubstituted product, [2,4,6-tris(trimethylsilylethynyl)phenyl](4-tert-butyl-2,6-dimethylphenyl)diazomethane (1d). Triplet diphenylcarbenes (DPCs) generated by photolysis of those ethynylated diphenyldiazomethanes were characterized by ESR and UV-vis spectroscopies at low temperature and laser flash photolysis techniques in solution at room temperature. Although ESR data indicated that ethynyl groups at the ortho positions are likely to stabilize triplet DPCs both sterically and electronically more effectively than o-bromine groups, kinetic studies suggested that the stability of triplet DPCs is not increased by o-ethynyl groups, as opposed to o-bromine groups. It is likely that triplet DPCs decay by interacting with the o-ethynyl groups.     

New hypocholesterolemic abietamide derivatives. II. Synthesis and hypocholesterolemic activity of N-phenyl-delta 8-dihydroabietamides

A series of N-phenyl-delta 8-dihydroabietamide analogs were prepared and tested for hypocholesterolemic activity. The effects of substituents of the phenyl moiety on the activities were quantitatively analyzed by using various substituent parameters. The activities were enhanced by the electron-donating effect of ortho and para substitutents and the bulkiness of ortho substituents. A combination of 2,6-dimethylaniline with resin acids other than delta 8-dihydroabietic acid produced lower activities than N-(2,6-dimethylphenyl)-delta 8-dihydroabietamide, abietane-type carboxamides being somewhat stronger than pimarane-type carboxamides. The conversion of the carboxamide group to other groups resulted in more or less of a decrease in activity, giving evidence that the carboxamide group is important to hypocholesterolemic activity.     

Triplet diphenylcarbenes protected by trifluoromethyl and bromine groups. A triplet carbene surviving a day in solution at room temperature

Two types of diphenyldiazomethanes having two trifluoromethyl and two bromine groups at the ortho positions, either in unsymmetrical or in symmetrical fashion, that is, (2,6-dibromo-4-phenylphenyl)[4-phenyl-2,6-bis(trifluoromethyl)phenyl]diazomethane (U-1-N2) and bis(2-bromo-4-phenyl-6-trifluoromethylphenyl)diazomethane (S-1-N2), are prepared. Triplet diphenylcarbenes (U-(3)1 or S-(3)1) are generated from those precursors and are characterized by ESR, UV/vis spectroscopy at low temperature, as well as time-resolved UV/vis spectroscopy at room temperature. Those carbenes are shown to be at least 2 orders of magnitude less reactive than the most stable triplet diphenylcarbene thus far known, that is, bis(2,6-dibromo-4-phenylphenyl)carbene. It has been also shown that S-(3)1 is significantly more stable than U-(3)1 even though both have the same two kinds of substituents. It is suspected that the perpendicular alignment of the two most bulky groups is a more effective way to shield the carbenic center than the planar one. By this way, triplet substituted diphenylcarbene surviving nearly a day in solution at room temperature is realized for the first time.     

DFT studies of biarylcarbenes and the carbene-biradical continuum

We use electronic structure modeling, mainly density functional methods, to characterize a variety of long-lived bisaryl triplet carbenes. The bisaryl systems have a triplet ground state, favored by a substantial delocalization of the spin into the aromatic rings. One can imagine two extreme cases of the bonding in these species, representable as valence isomers. In the first case, spin delocalization is minor and incidental; the spin is predominantly located on the central carbene carbon. In the second case, spins are separated by large distances and are found primarily on the aromatic rings; the rings are linked by an allenic bridge. The bisphenyl carbenes tend toward the first limit. They can be kinetically stabilized by ortho substituents which shield the reactive center and para substituents which protect that site which has substantial spin density. The bond angle at carbene is opened from about 142 degrees (the B3LYP/6-31G value for the parent bis(phenyl)carbene) to 160 degrees or more by these substituents. Bisanthryl carbenes illustrate the second extreme, favoring a D(2)(d)() structure and possessing a low-lying open shell singlet state. A hypothetical phenyl-9-anthrylcarbine lies between the carbine and diradical extemes. The same principle which guides the design of stabilized diphenylcarbene carbenes and substitution of reactive sites by bulky protective groups serves to stabilize the bis-9-anthrylcarbene biradical.     

取代基物化参数及其在药物定量构效关系中的应用

把取代基电性、立体及疏水性物化参数组合建立一种新取代基描述方法, 对环尿素类和N,N-二甲基-2-溴苯乙胺类衍生物进行结构表征. 对训练样本集通过逐步回归筛选变量, 所建多元线性回归方程R2分别为0.853和0.960, 留一法交互检验Rcv2分别为0.723和0.901；用预测集样本作外部预测, 所得Qext2分别为0.7617和0.7653. 结果显示：环尿素类化合物结构中苯环邻位立体、间位疏水、对位疏水及立体因素对该类药物抗HIV活性产生阻抑作用； N,N-二甲基-2-溴苯乙胺类苯环上取代基立体因素及对位给电子效应有利于提高肾上腺素能阻断活性.     

Preparation of bis(diazo) compounds incorporated into butadiyne and thiophene units, and generation and characterization of bis(carbene) from these compounds

[9-[10-(4-t-Butyl-2,6-dimethyl)phenyl]anthryl](4-bromo-2,6-dimethylphenyl)diazomethane (1-N(2)) was found to be stable enough to survive under Sonogashira and Suzuki coupling reaction conditions, and bis(diazo) compounds incorporated into the 1,4-positions of butadiyne (3-2N(2)) and the 2,5-position of thiophene (4-2N(2)) were prepared. Irradiation of those bis(diazo) compounds generated bis(carbenes), which were characterized by ESR and UV-vis spectroscopic techniques in a matrix at low temperature, as well as time-resolved UV-vis spectroscopy in solution at room temperature. These studies revealed that both of the bis(carbenes), 3 and 4, have a singlet quinoidal diradical ground state with a very small singlet-triplet energy gap of less than 1 kcal/mol. A remarkable increase in the lifetime of bis(carbenes) as opposed to that of monocarbene (1) was noted and was interpreted to indicate that bis(carbenes) are thermodynamically stabilized as a result of delocalization of unpaired electrons throughout a pi-net framework. Despite the stability, both bis(carbenes) are readily trapped by molecular oxygen to afford bis(ketones) as main products.     

A comparison of linear optical properties and redox properties in chalcogenopyrylium dyes bearing ortho-substituted aryl substituents and tert-butyl substituents

A series of thiapyrylium pentamethine dyes (4 and 12-15) bearing 2,2'-di-tert-butyl-6,6'-diphenyl, 2,2'-di-tert-butyl-6,6'-bis(2,6-dimethylphenyl), 2,2'-di-tert-butyl-6,6'-bis(2-methylphenyl), 2,2',6,6'-tetrakis(2,6-dimethylphenyl), and 2,2',6,6'-tetrakis(2-methylphenyl) substituents, respectively, were prepared and their linear optical properties and electrochemical redox properties were measured and compared to thiapyrylium pentamethine dyes 3 and 5. The tert-butyl and 2,6-dimethylphenyl substituents give nearly identical chromophores with respect to values of lambda(max), molar extinction coefficients (epsilon), bandwidths at half-height (nu(1/2)), and lack of absorption in the visible spectrum. The 2-methylphenyl substituent imparts linear optical properties that are intermediate between those of the tert-butyl and phenyl substituents. The 2,6-dimethylphenyl and 2-methylphenyl substituents impart greater oxidative stability based on anodic shifts in oxidation potential.