Site-specific interaction between hydrocarbon cations and inert ligands: IR spectra of isomeric C3H3+–L dimers (L = Ne,Ar,O2,N2,CO2)
Site-specific interaction between hydrocarbon cations and inert ligands: IR spectra of isomeric C3H3+–L dimers (L = Ne,Ar,O2,N2,CO2)
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烃类阳离子和惰性配体之间的位点特异性相互作用：异构体 C3H3+–L 二聚体的红外光谱 (L = Ne,Ar,O2,N2,CO2)
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
O. Dopfer
中科院分区：
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作者：
Doris Roth;O. Dopfer
在C-H伸缩基本原理的光谱范围内记录了具有惰性配体L=Ne、Ar、O2、N2和CO2的C_3H ~（3+）-L二聚体的红外（IR）光解离光谱。在簇离子源中，通过联烯（H2 CCCH 2）的电子碰撞电离产生至少两种C3 H3+异构体，即环丙烯基（c-C3 H3+）和炔丙基（H2 CCCH+）阳离子。这两个C3 H3+离子形成弱结合的加合物与所有考虑的配体和吸引力在这些离子-配体复合物中占主导地位的诱导和静电力。一般情况下，在c-C3 H3 +-L和H2 CCCH +-L的分子间相互作用的顺序增加Ne<Ar<O2<N2<CO2，与极化率，四极矩，和质子亲合势L。对c-C3 H3 +-L的ν4振动的振转分析揭示了几个竞争的结构结合基序，包括形成H-键（L=N2，CO2，O2），C-键（L=CO2）和π-键（L=O2）。优选的结合位点和平衡结构的细节强烈地依赖于L。与此相反，观察到的H2 CCCH +-L二聚体的特征是L和炔属质子之间的所有H-键。在MP2（full）/6- 311 G（2df，2 pd）水平上对c-C3 H3 +-L和H2 CCCH +-L的从头计算提供了关于这些离子-配体络合物的分子间势能面的额外信息，并证实了对实验IR光谱的解释。在c-C3 H3 +-（CO2）n（n=1-3）中观察到的光致碎裂分支比，使分子间氢键和C键的解离能估计为D 0（H/C）=1300±300 cm−1。
Infrared (IR) photodissociation spectra of isomeric C3H3+–L dimers with the inert ligands L=Ne, Ar, O2, N2, and CO2 are recorded in the spectral range of the C–H stretch fundamentals. At least two C3H3+ isomers are generated by electron impact ionization of allene (H2CCCH2) in the cluster ion source, namely the cyclopropenyl (c-C3H3+) and propargyl (H2CCCH+) cations. Both C3H3+ ions form weakly-bound adducts with all ligands considered and the attraction in these ion–ligand complexes is dominated by induction and electrostatic forces. In general, the intermolecular interaction in both c-C3H3+–L and H2CCCH+–L increases in the order Ne<Ar<O2<N2<CO2, in line with the polarizabilities, quadrupole moments, and proton affinities of L. Rovibrational analysis of the ν4 vibrations of c-C3H3+–L involving molecular ligands reveals several competing structural binding motifs, including the formation of H-bonds (L=N2, CO2, O2), C-bonds (L=CO2), and π-bonds (L=O2). The preferred binding site and details of the equilibrium structure strongly depend on L. In contrast, the observed H2CCCH+–L dimers feature all H-bonds between L and the acetylenic proton. Ab initio calculations for c-C3H3+–L and H2CCCH+–L at the MP2(full)/6-311G(2df,2pd) level provide additional information about the intermolecular potential energy surface of these ion–ligand complexes and confirm the interpretation of the experimental IR spectra. Photofragmentation branching ratios observed for c-C3H3+–(CO2)n with n=1–3 allow the dissociation energy of the intermolecular H-bonds and C-bonds to be estimated as D0(H/C)=1300±300 cm−1.