~3E态CH_3N自由基的稳定性(英文)

观察到了CH_3N自由基~3E←~3A_2体系317-272nm 的荧光激发谱,特别讨论了振动激发的态的稳定性.报导了v_3~′=6态的色散荧光和荧光时间谱,该态在240 Pa 下的寿命大约是80ns.实验表明~3E 态CH_3N 自由基是稳定的,势能面至少距振动基态4800 cm~(-1)内是束缚的,异构化或预离解作用并不重要.     

卤化氢共振增强多光子电离光谱

测定了卤化氢(HCl, HBr 和HI) (2+1)共振增强多光子电离(REMPI)光谱, 采用模拟计算法分析推导出转动常数、谱带源以及Ω态振动谱带的同位素位移值. 得到的HCl数据同Green等人用常规分析法所推导的结果极为吻合. 得出8条振动谱带,其中包括V(¹∑⁺)态, E(¹∑⁺)的v'=4态以及HBr的5个新谱带, 此外还推导出HI的E态v'=1的4个振动谱带光谱参数. 观测了V和E态之间因同类相互作用而产生的不规则能级间距、转动参数和同位素位移. 讨论了HCl和HBr的E态和V态振动谱带中的转动谱线序列O和S对Q的强度比变化,提出了双光子激发机理.     

Li＋在基于N,N-二甲基甲酰胺混合溶剂中的溶剂化

利用红外和拉曼光谱技术研究了Li^＋在不同浓度、不同溶剂组成的LiBF₄/N,N-二甲基甲酰胺-乙腈、LiBF₄/N,N-二甲基甲酰胺-四氢呋喃电解质溶液中的优先溶剂化现象. 红外和拉曼光谱的分析表明, Li^＋主要与DMF分子相互作用, 导致该分子的C＝O伸缩振动谱带、N—C＝O形变谱带、CH₃摇摆谱带等发生了分裂. Li^＋与其它溶剂分子的相互作用较弱, 谱带的分裂现象并不明显. Li^＋溶剂化数的计算显示, Li^＋第一溶剂化层内DMF分子的数目一般大于2, 这说明 Li^＋在混合溶剂体系内优先与DMF分子相互作用. 量子化学计算支持了这一结论.     

掺钕三硼酸铋晶体(Nd:BiB3O6)的光谱性质

采用顶部籽晶法, 生长了掺钕的新型非线性光学晶体Nd:BiB₃O₆ , 测量了该晶体的折射率, 并拟合了晶体的折射率色散参数. 同时还测量了晶体的室温吸收谱, 并与0.2 mol/L的 NdCl₃溶液的室温吸收谱进行了分析比较. 根据Judd-Ofelt理论, 拟合出晶体场唯象强度参数: Ω ₂ = 0.1776 ´ 10^-20 , Ω ₄ = 0.1282 ´ 10^-20, Ω ₆ = 0.1357 ´ 10^-20cm². 计算了各能级的辐射跃迁几率A_J,J', 荧光辐射寿命τ , 荧光分支比β_J', 振子强度f_J,J'等. 根据这些光学参量, 讨论了该晶体的部分性能和应用前景.     

2,4,4'-三羟基脱氧安息香-3'-磺酸钴的合成、晶体结构表征及性质研究

合成了未见文献报道的水溶性很好的2,4,4'-三羟基脱氧安息香-3'-磺酸钴, 采用IR, UV, ¹H NMR和元素分析对其进行了表征, 并利用X射线单晶衍射仪测定了该化合物的晶体结构. 使用荧光光谱法检测了化合物对羟基自由基的清除作用, 紫外光谱法检测其对超氧自由基的清除作用. 实验结果表明, 2,4,4'-三羟基脱氧安息香-3'-磺酸钴[C₂₈H₄₆CoO₂₆S₂]属于单斜晶系, 空间群C2/c, a＝3.3937(3) nm, b＝0.85180(7) nm, c＝1.37455(11) nm, α＝90°, β＝97.8200(10)°, γ＝90°, Z＝4, V＝3.9365(5) nm³, D_c＝1.555 g/cm³, F(000)＝1924, R₁＝0.0329, wR₂＝0.0852, 具有较好的清除羟基自由基和超氧自由基的作用.     

HCF(X~1A’)+SO2反应的动力学研究

用激光光解-激光诱导荧光方法研究了室温下(T＝293 K) HCF(X^~1A^’)自由基与SO₂分子的反应动力学. 实验中HCF(X^~1A^’)自由基是由213 nm激光光解HCFBr₂产生的, 用激光诱导荧光(LIF)检测HCF(X^~1A^’)自由基的相对浓度随着反应时间的变化, 得到此反应的二级反应速率常数为: k＝(1.81±0.15)×10^－12 cm³•molecule^－1•s^－1, 体系总压为1862 Pa. 高精度理论计算表明, HCF(X^~1A^’)和SO₂分子反应的机理是典型的加成-消除反应. 我们运用RRKM-TST理论计算了此二级反应速率常数的温度效应和压力效应, 计算结果和室温下测定的二级反应速率常数符合得较好.     

(AlN) n团簇的结构与稳定性

用飞行时间质谱法观察到AlN⁺,Al₂N₂⁺等团簇的存在.结合密度泛函理论的B3LYP/6-31G^* 方法,对(AlN)_n(n = 1~15)团簇的几何构型、电子结构和振动频率等性质进行了优化计算,讨论了化学键的特征和热力学稳定性,解释了实验质谱.结果表明:在(AlN)_n团簇的基态结构中,不存在Al?/FONT>Al和N?/FONT>N键, Al?/FONT>N键是惟一键型; (AlN) _n结构稳定性的幻数为: 原子数为4, 8, 12, 16, 20, …等4的倍数.     

烯丙基6~8eV之间电子振动光谱的共振增强多光子电离研究

在分子束中用高温热解3-碘代丙烯的方法产生烯丙基,并结合飞行时间质谱和2+1共振增强多光子电离技术,从实验上观测到了烯丙基从基态到6~8eV之间的6个电子态3d_xz, 3d_xy,ns(n=4,6,7,8)的电子振动光谱.在ns的Rydberg态电子振动光谱中可以观测到v₇(∠CCC弯曲振动)约为430cm^-1的振动级数.由Rydberg公式拟合得到烯丙基的绝热电离能为(65641±20)cm^-1((8.138±0.002)eV).     

含有识别基团的两亲性给-受体型分子的聚集行为

利用紫外-可见光谱、表面光电压谱及荧光发射谱对两种以具有识别功能的巴比妥酸基团作为受体的两亲性给-受体型分子,5-(-4-十二烷氧基苯乙烯基)-(1H,3H)-2,4,6-嘧啶三酮(PB₁₂)和5-(-4-N,N-二-十二胺基苯乙烯基)-(1H,3H)-2,4,6-嘧啶三酮(AB₁₂) 的聚集行为进行了研究.结果表明,在分子间氢键、π-π及van der Waals等弱相互作用的协同调控下,随着浓度的增加,PB₁₂形成J-聚集体,而AB₁₂形成柱状囊泡形H-聚集体.当溶液浓度大于10^-4 mol/L时,PB₁₂在峰值波长500 nm附近出现来源于J-聚集体的扭曲分子内电荷转移带(TICT) 的发射,AB₁₂在峰值波长600 nm附近出现来源于H-聚集体的激基缔合物的荧光.     

HPO2异构体结构和相对稳定性

在MP2/6-311++G(d,p)和QCISD(t)/6-311++G(3df,2p)(单点)水平下计算得到了包括8个异构体和12个过渡态的HPO₂体系势能面. 在势能面上, 异构体cis-HOPO(E1)的能量是最低的, 其次是trans-HOPO(E2)和HPO(O)(C_2V, E3), 能量分别比cis-HOPO高10.99和48.36 kJ/mol. 根据体系的势能面, 只有异构体E1和E3具有较高的动力学稳定性, 在实验中应该可以观测到. PH和O₂直接反应生成的cis-HPOO(E5)和trans- HPOO(E6)经过几步势垒较低的异构化过程就可以异构化为具有较高动力学稳定性的产物E1; 而OH和PO反应可直接生成E1. 计算结果较好地解释了相关实验.     

某些萃取剂与C6—C9芳烃相互作用的1H NMR研究

以四氯化碳作为惰性参考溶剂, 研究了N-甲基-2-吡咯烷酮(NMP)、环丁砜、N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMA)和γ-丁内酯(γ-BL)等五种萃取剂在几种芳烃溶剂中的~1H NMR谱。观察到萃取剂分子的化学位移在芳烃溶剂中均大幅度移向高场, 且NMP、γ-BL的共振谱线在芳烃中发生分裂或重叠。在不同的芳烃溶剂中, 以在苯乙烯中NMP、DMF、DMA、环丁砜共振谱线的移动幅度为最大。各萃取剂谱线位移的幅度随着苯环上甲基数目的增多而递减。结合溶液热力学的结果, 推断出NMP等萃取剂和芳烃分子之间存在着弱化学作用。     

氧心羧桥异三核过渡金属簇合物[Fe2MO(CH3COO)6Py3].Py(1,M=Mn;2,M=Co;3,M=Ni)和[Fe2MO(CCl3COO)6(THF)3](4,M=Mn;5,M=Co;6,M=Ni)电子光谱的研究

The UV/VIS spectra for pyridine solution of complexes [Fe_2MO(CH_3COO)_6Py_2]·Py and THF solution of complexes Fe_2MO(CCl_3COO)_6(THF)_3 were studied. The d-d transitions were assigned and the ligand field parameters(B,D_q,β) were calculated for the related metal ions according to ligand field theory (Tanabe-Sugano diagram) in terms of O_h symmetry and reasonably good fits were obtained for the calculated and observed frequencies. The calculated results show that (1) the larger the ionic potential for M~(2+) ion, the larger the values of B, D_q for Fe~(3+) ion (2) the ligand field parameters of metal ions vary in parallel with the electronagativity of R in RCOO~-.     

酸性介质中1,2-丙二醇在铂电极上吸附和氧化过程的原位FTIR反射光谱研究

应用电化学循环伏安和原位FTIR反射光谱研究1,2-丙二醇在Pt电极上吸附和氧化过程。结果指出1,2-丙二醇的电氧化可按双途径进行。其一经1,2-丙二醇在Pt上解离吸附产物氧化至CO_2。但在较低电位下这些解离吸附产物(红外检测为CO_(ad)、[﹥C=CH_2]_(ad)等)累积吸附于电极上, 毒化Pt表面抑制其它反应。当电位大于0.3 V后它们一经生成即氧化脱附, 从而使1,2-丙二醇得以在未毒化Pt表面经反应中间体氧化至CO_2。在实验条件下,原位FTIR反射光谱检测到的反应中间体可能有HOC-CHOHCH_3(或CH_2OHCOCH_3)和HOOC-COCH_3(或HOOC-CHOHCH_3)等物种。     

组合型Pt3Sn/Al2O3催化剂用于芳香硝基化合物一锅法合成N-烷基芳胺

采用吸附法制备了组合型Pt₃Sn/Al₂O₃双金属催化剂, 将该催化剂用于芳香硝基化合物原位液相加氢一锅法合成N-烷基芳胺. 研究表明, 在503 K, 空速为7.5 h^-1, 水体积分数为5%时, 1%(质量分数)Pt₃Sn/Al₂O₃催化剂具有较高的催化性能, 硝基苯的转化率为100%, N-乙基苯胺和N,N-二乙基苯胺的总选择性为98.2%. 同时,该催化剂对原位液相加氢烷基化反应具有一定普适性, 本文研究的14 种芳香硝基化合物与低级脂肪醇反应,均具有较高的N-烷基化产率.     

C60微电极伏安法研究

The microdisk electrode voltammetric behaviors of C_(60) are reported in this communication. This was accomplished by use of a mixed solvent system as Acetonotrile:Xylene=1:4 and a supporting electrolyte as 0.1 mol·L~(-1) Bu_4NPF_6. Au, Pt and Hg (Pt) were used as working electrode. In this new conditions, the successive six step reduction of C60 were obtained at below 15 ℃. It was found that the former five steps are all the single electron reversible reduction, but behaviors of the sixth steps are like EC' processes. Several electrochemical data were determined.     

含时变分S 矩阵解得一般形式

推导出含时S散射矩阵变分表达式经基函数展开并优化后的解的一般形式。     

一维数值计算验证S散射矩阵变分表达式

一维谐振子被用来验证我们提出的S散射矩阵的含时变分表达式[北京大学学报(自然科学版), 1991, 27, 460]。结果表明, 这一S矩阵的变分表达式对于量子散射计算有很好的应用前景。     

内嵌复合物X@C60中相互作用的变化规律与键本质

系统地研究了内嵌复合物Ｘ＠Ｃ６０（Ｘ＝第ＩＡ簇或第ＶＩＩＡ族元素）形成过程的能量变化,以及其中笼环境下Ｘ与Ｃ６０间相互作用的变化特征与键本质。结果表明：（１）Ｃ６０笼环境力场具有球对称性;（２）各种分解与总相互作用与内嵌原子的原子序数或原子半径呈现出规则的递变规律;（３）除Ｉ外,其余元素原子与Ｃ６０间的作用对各自复合物的稳定性都有正效应的较大贡献;（４）Ｘ在Ｃ６０笼环境中居心或偏心的稳定位置是各种     

NH0-1+2-3离解能等的高级ab initio计算与评价

A recent experimental determination[1] of the dissociation energies (D0) for H2N-H, H2N+-H and H2N-H+, the ionization energies for NH3 and NH2 resulted in large deviations when compared with those of the earlier values and the QCISD(T)/6-311+G(3df,2p) ab initio calculations. We have performed some higher level ab initio calculations on these data by utilizing the Gaussian 92/DFT and Gaussian 94 pakages of programs and have assessed the available experimental values. Our calculations were carried out at the QCISD (TQ)/aug-cc-pVDZ, G2(QCI), QCISD(T)/6-311 ++G(3df,3pd) and QCISD(T)/aug-cc-pVTZ levels of theory. Geometries were optimized at both of the MP2(full)/6-31G(d) and the MP2(full)/6-31(d,p) levels, and were compared with those of the experiments if available. The MP2(full)/6-31G(d,p) tight-optimized geometries for the neutrals are closer to those of the experiments than those of the MP2 (full)/6-31G(d), and are in excellent agreement with the experimental results as shown in Table 1. In this case, we assumed that the optimized geometries for the cations would be better if p polarization functions are added to the hydrogen atoms. We firstly noted that the symmetry of the NH3+ cation was D3h, other than Cs. as reported in ref.[1]. All of the zero-point energies and the final geometries are calculated at the MP2(full)/6-31G(d,p) level of theory. We have also repeated the QCISD(T )/6-311 + G(3df,2p) calculations of ref. [1], because we could not identify their level of goemetry optimization. It is found that the total energy, -55.244 19 Hartrees, for NH2+(1A1 ) in ref.[1] might be in error. Our result is -55.336 29 Hartrees at the same level of theory. At our highest level [QCISD(T)/aug-cc-pVTZ] of calculations as shown in Table 3, the D0 (temperature at zero Kelvin) values of H2N-H, H2N+-H(3B1for NH2+ ) and H2N- H+ are 4.51, 5.49 and 8.00 eV, respectively. These data reported in re f.[1] were 4.97, 5.59 and 8.41 eV, respectively. Our result on D0(H2N-H) supports the work of ref.[2,3,5,6]. The ionization energies (IE) for NH3 and NH2 (3B1 for NH2+) at our highest level are 10.11 and 11.09 eV while in ref.[1] were 10.16 and 10.78 eV, respectively. For the latter, our result supports the experiment of ref.[3]. Our predicted D0 for HN2+-H and IE for NH2 (1A1 for each NH2+) are 6.80 and 12.39 eV, respectively. These values differ greatly from the predicted values (9.29 and 14.88 eV) of ref.[1] where the total energy of NH2+(1A1) might be in error. The D0 value for HN-H has not been found in ref.[1]. Our result supports the work of ref.[3]. We have also derived all of these values at the temperature of 298K and under the pressure of 101kPa at several levels of thoery as shown in Table 3. On examining the experiment of ref.[1] in detail, it is easy to find that all of the larger deviations might be from a too high value of the appearance potential of proton AP(H+). Indeed, ref.[1] has mentioned that the determintion of AP(H+), due to kinetic shift, would lead to a hihger value for the dissociation energy as has been pointed out by Berkowitz and Ruscic. In this work, we concluded that, besides some mistakes in the theoretical calculations of ref.[1], the dissociation energies for H2N-H and H2N-H+,the IE for NH2 (3B1 for NH2+) might also be unreliable and need to be re-examined.
     

取代基对α-氨基乙腈热解反应影响的研究

用MINDO/3方法洋细研究了取代基对α-氨基乙腈热消除反应的影响. 研究表明, 对于孤立分子的气相反应, 给电子基使活化势垒降低, 吸电子基使活化势垒上升; 而对OH~-催化下的反应, 给电子基和吸电子基均使活化势垒上升.