Photochemical Reactions of Organometallic Compounds

在我们发展的激光烧蚀-分子束方法中，脉冲激光在真空中聚焦在金属衬底表面。激光烧蚀被用于制备化学反应物种，在这种情况下是金属离子。在附近注入一束有机或无机分子，即苯、氨或甲醇，在稀有气体中播种。离子-分子反应生成M(C6H6)n^+、M(CH&lt；&Gt；OH)n^+和M(NH3)n^+等簇状络合离子。对于某些金属，可以观察到氢或碳氢小分子等中性小分子的消除，得到M(C_6H_6)(C_XH_Y)X*6，Y*4和M(NH)_m(NH_3)_n，m=1，2。这种方法虽然非常简单，但对于研究金属离子与有机和无机分子，特别是与分子簇的反应是一种通用的诊断方法。安。例如，Ar中的苯分子束(类型。用C_6H_6 60Torr/Ar 200Torr)，用电子轰击探测，(C_6H_6)_n高达n=5。在激光烧蚀金属衬底的情况下，与M_+离子反应生成了M(C_6H_6)_n^+(n=2-4)簇状络合离子。Y^+发生了氢的消除，即。Y(C_6H_4)^+的形成。对于Nb^+和Ta^+，发生氢或小分子烃的消除，生成Nb(C&lt；12&gt；H&lt；10&gt；)^+，Nb(C&lt；12&gt；H_8)^+，Nb(C&lt；10&gt；H_8)^+，Nb(C&lt；10&gt；10&gt；H_6)~+、Nb(C_8H_8)~+和Nb(C_8H_6)_+。为了研究金属有机化合物在激光光化学气相沉积中的反应机理，研究了三甲基铝和三甲基镓在气相和固体衬底上的光解离反应。反应中间体Al、Al(CH_3)_n、Ga和Ga(CH_3)_n(n=1-2)已被激光诱导荧光或多光子电离飞行时间质谱仪探测。

In the laser ablation-molecular beam method developed by us, pulsed laser beam is focused on the surface of a metal substrate in vacuum. Laser ablation is utilized for the preparation of chemically reactive species, metal ions in this case. A molecular beam of organic or inorganic molecules, viz., benzene, ammonia or methanol, seeded in rare gas, is injected nearby. Ion-molecule reaction yields a variety of clustered complex ions such as M(C_6H_6)_n^+, M(CH_<>OH)_n^+, and M(NH_3)_n^+. For some metals, elimination of small neutrals like hydrogen or small hydrocarbon molecules is observed to give M(C_6H_6)(C_XH_Y) X*6, Y*4 and M(NH)_m(NH_3)_n, m=1, 2. Such a method, albeit very simple, is a versatile diagnosis for the study of reactions of metal ions with organic and inorganic molecules, especially with molecular clusters.Taking the reactions of benzene clusters with metal ions as. an. example, a molecular beam of benzene in Ar(typ. C_6H_6 60 Torr/Ar 200 Torr)was used ; (C_6H_6)_n up to n=5 was found when probed by electron impact. With laser ablation of a metal substrate, reactions with M_+ ions gave clustered complex ions of the type M(C_6H_6)_n^+ (n=2-4)for most of metal ions used. Elimination of hydrogen occurred for Y^+, viz. the formation of Y(C_6H_4)^+. For Nb^+ and Ta^+, elimination of hydrogen or small hydrocarbon occurred to give fragment complex ions as Nb(C_<12>H_<10>)^+, Nb(C_<12>H_8)^+, Nb(C_<10>H_8)^+, Nb(C_<10>H_6)^+, Nb(C_8H_8)^+ and Nb(C_8H_6)_+.In order to study reaction mechanisms in laser photo-CVD of organometallic compounds, photodissociation reactions of trimethylaluminum and trimethylgallium have been investigated both in the gas phase and on a solid substrate. Reaction intermediates such as Al, Al(CH_3)_n, Ga and Ga(CH_3)_n (n=1-2)have been probed either by laser-induced fluorescence or by multiphoton ionization followed by time-of-flight mass spectrometry.