Shin Joong-Won, Bernstein Elliot R
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA.
J Chem Phys. 2009 Jun 7;130(21):214306. doi: 10.1063/1.3148378.
Infrared plus vacuum ultraviolet (IR/VUV) nonresonant photoionization spectroscopy and VUV/IR photodissociation spectroscopy are employed to study fragmentation pathways and structures of neutral and ionic 2-propanol ((CH(3))(2)CHOH) (IPA) and their relevant clusters of size up to the pentamer. Only the gauche monomer is generated in the supersonic expansion; its VUV induced fragmentation pathways involve C(alpha)-C(beta) bond dissociation. The clusters consist of both gauche and trans conformers and their VUV induced fragmentation pathways are size dependent. The IR spectra of neutral clusters (IPA)(n) suggest that the dimer has a chainlike structure, whereas larger clusters have cyclic structures. VUV ionization of the neutral gauche 2-propanol generates two parent cation isomers whose C(alpha)-C(beta) bond dissociations are facilitated by excitation of the OH vibrations. The IR spectra of ionic molecular complex clusters (IPA)(n-1)CH(3)CHOH(+) and protonated clusters (IPA)(n-1)H(+), generated by VUV ionization of neutral clusters, show that both cluster types adopt open structures with at least one free OH group. Qualitative structural assignments are generated for the neutral species based on MP2/aug-cc-pVDZ, MP2/6-31G, and B3LYP/6-31+G(d) calculations.
采用红外加真空紫外（IR/VUV）非共振光电离光谱和VUV/IR光解离光谱研究中性和离子态2-丙醇（(CH(3))(2)CHOH，IPA）及其相关的五聚体以内的簇合物的碎裂途径和结构。在超声速膨胀中仅产生gauche单体；其VUV诱导的碎裂途径涉及C(α)-C(β)键解离。簇合物由gauche和反式构象体组成，且其VUV诱导的碎裂途径与尺寸有关。中性簇合物(IPA)(n)的红外光谱表明，二聚体具有链状结构，而较大的簇合物具有环状结构。中性gauche 2-丙醇的VUV电离产生两种母体阳离子异构体，其C(α)-C(β)键解离因OH振动的激发而加速。由中性簇合物的VUV电离产生的离子分子络合物簇合物(IPA)(n-1)CH(3)CHOH(+)和质子化簇合物(IPA)(n-1)H(+)的红外光谱表明，这两种簇合物类型均采用具有至少一个游离OH基团的开放结构。基于MP2/aug-cc-pVDZ、MP2/6-31G和B3LYP/6-31+G(d)计算对中性物种进行了定性结构归属。
