Study on catalytic properties by soft-landing of gas-phase clusters of metal-oxide and -sulfide

由3-1000个原子组成的气相团簇受到了广泛的关注，因为它们可以被视为光电子和磁学开发新催化和新功能材料的最小单元。特别是金属氧化物长期以来在催化化学中得到广泛应用，金属氧化物团簇的性质对制备选择性和活性催化剂具有重要意义。基于这一观点，可以得到以下三个结果。(1)通过将金属原子与有机配体分离，可以在气相中成功合成有机金属团簇配合物。首次合成了一种将金属原子夹在自由基有机配体中间的一维聚二茂铁。这一结果为评价配合物的电子自旋态和功能提供了基本的见解。(2)利用阴离子光电子能谱法观察氧化钇簇的电子结构。进一步测定了过渡金属氧化物簇的电子结构和对NH_3的吸附活性。(3)成功建立了金属有机簇的尺寸选择簇软着陆方法。采用激光烧蚀法与苯蒸气反应制备有机金属团簇离子，选择合适的尺寸并沉积在低温Ar基体中。在沉积能量为20 eV的条件下，沉积1 h后，测量了V_1（苯）_2在Ar基体中的红外光谱。结果表明，在气相反应中制备的V_1（苯）_2呈夹层结构，离子软着陆在Ar基体上，并通过金属衬底的电荷转移而中和，没有碎裂。这些结果表明，软着陆方法可以为气相团簇沉积制备新材料开辟一条新途径。

Gas-phase clusters consisting of 3-1000 atoms have attracted much attention, because they can be regarded as a minimum unit for optoelectronics and magnetism to develop new catalysis and new functional materials. Especially, metal oxide have been utilized widely in catalytic chemistry for so long time that the properties of metal oxide clusters would be of improtance to generate selective and active catalyst. Based upon this viewpoint, the following three results can be obtained.(1) Organometallic cluster complexes coud be successfully synthesized in the gas phase by isolating metal atoms with organic ligands. One dimensional poly-ferrocene was synthesized for the first time, where a couple of metal atoms were sandwiched by radical organic ligands. This result gives fundamental insight to evaluate the electron spin state of the complexes as well as the functionality.(2) The electronic structure of yttrium oxide clusters was observed by photoelectron spectroscopy of their anions. For transition metal oxide clusters, furthermore, electronic structure and adsorption reactivity of NH_3 were measured.(3) The methodology of soft-landing of size-selected cluster was successfully established for organometallic clusters. The organometallic cluster ions, produced by laser ablation with reaction toward benzene vapor, were size-selected and deposited into a low-temperature Ar matrix. Infrared spectrum of V_1 (benzene)_2 in the Ar matrix was measured after 1-hour deposition with the deposition energy of 20 eV.The spectrum was in agreement with both the reported spectrum, showing that V_1 (benzene)_2, prepared in the gas phase reaction, takes a sandwich structure and that the ions were soft-landed onto the Ar matrix and were neutralized by charge transfer from a metal substrate without fragmentation.These results indicate that the soft-landing method can open up a new approach for fabricating new materials with the deposition of the gas-phase clusters.