Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
J Phys Chem A. 2011 May 5;115(17):4148-56. doi: 10.1021/jp1107526. Epub 2011 Apr 12.
Infrared predissociation (IRPD) spectra of Li(+)(C(6)H(6))(1-4)(H(2)O)(1-2)Ar(0-1) and Na(+)(C(6)H(6))(2-4)(H(2)O)(1-2)Ar(1) are presented along with ab initio calculations. The results indicate that the global minimum energy structure for Li(+)(C(6)H(6))(2)(H(2)O)(2) has each water forming a π-hydrogen bond with the same benzene molecule. This bonding motif is preserved in Li(+)(C(6)H(6))(3-4)(H(2)O)(2)Ar(0-1) with the additional benzene ligands binding to the available free OH groups. Argon tagging allows high-energy Li(+)(C(6)H(6))(2-4)(H(2)O)(2)Ar isomers containing water-water hydrogen bonds to be trapped and detected. The monohydrated, Li(+) containing clusters contain benzene-water interactions with varying strength as indicated by shifts in OH stretching frequencies. The IRPD spectra of M(+)(C(6)H(6))(1-4)(H(2)O)(1-2)Ar are very different for lithium-bearing versus sodium-bearing cluster ions emphasizing the important role of ion size in determining the most favorable balance of competing noncovalent interactions.
给出了 Li(+)(C(6)H(6))(1-4)(H(2)O)(1-2)Ar(0-1) 和 Na(+)(C(6)H(6))(2-4)(H(2)O)(1-2)Ar(1) 的红外预解离 (IRPD) 光谱及其从头算计算结果。结果表明，Li(+)(C(6)H(6))(2)(H(2)O)(2) 的全局最低能量结构为每个水分子与同一苯分子形成π氢键。这种键合模式在 Li(+)(C(6)H(6))(3-4)(H(2)O)(2)Ar(0-1) 中得以保留，额外的苯配体与可用的游离 OH 基团结合。氩标记允许捕获和检测含有水分子氢键的高能 Li(+)(C(6)H(6))(2-4)(H(2)O)(2)Ar 异构体。含有水的单水合 Li(+) 包含苯-水相互作用，其强度不同，这表明 OH 伸缩频率的变化。含 M(+)(C(6)H(6))(1-4)(H(2)O)(1-2)Ar 的簇离子的 IRPD 光谱对于含锂和含钠的簇离子非常不同，这强调了离子大小在确定最有利的非共价相互作用平衡方面的重要作用。
