Infrared spectroscopy of Cu+(H2O)(n) and Ag+(H2O)(n): coordination and solvation of noble-metal ions.
Infrared spectroscopy of Cu+(H2O)(n) and Ag+(H2O)(n): coordination and solvation of noble-metal ions.
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DOI：
10.1063/1.2730830
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发表时间：
2007-05
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通讯作者：
T. Iino;K. Ohashi;Kazuya Inoue;K. Judai;N. Nishi;H. Sekiya
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文献类型：
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作者：
T. Iino;K. Ohashi;Kazuya Inoue;K. Judai;N. Nishi;H. Sekiya
研究了M(+)(H(2O)O)(N)和M(+)(H(2O)O)(N)Ar离子(M=铜和银)的配位和溶剂化结构。这些物种是在激光蒸发团簇源中产生的，并使用三重四极质谱计在OH-Stretch区域用红外(IR)光解离谱进行探测。对实验红外光谱进行了密度泛函理论计算。在Ag(+)(H(2O)O)(1)xAr的光谱中观察到的部分分辨转动结构表明，该配合物是准线性的Ar-Ag(+)-O构型，H原子对称地偏离轴。Ar标记的M(+)(H(2O)O)(2)的光谱与这些离子的O-M(+)-O线性配位一致，这是由M(+)中的S-d杂化稳定的。在Ag(+)(H(2O)O)(3)xAr中没有H(2)O分子间的氢键，而在Cu(+)(H(2)O)(3)xAr中通过OH-拉伸跃迁的位置和强度的特征变化而检测到了氢键。第三个H(2)O以三配位的形式直接结合在Ag(+)上，同时在二配位的铜(+)的第二壳层中占据氢键位置。三配位的偏好是由于在Ag(+)中的5s-4d杂交效率低下，而在铜(+)中广泛的4s-3D杂交保留了二配位。这很可能是因为Ag(+)的S-d能隙比Cu(+)的大得多。由于在M(+)(H(2)O)(4)xAr中观察到广泛的氢键，第四个H(2)O占据了三配位的Ag(+)和二配位的Cu(+)的第二壳层。有趣的是，Ag(+)(H(2)O)(4)xAr离子不仅具有三配位形式，而且还具有二配位形式，这些形式在Ag(+)(H(2)O)(3)xAr中是不存在的，但在n=4时又恢复了。当n=5-7时，Cu(+)(H(2)O)(N)的光谱随尺寸的变化提供了第二壳层在n=6时完成的证据，其中二配位的Cu(+)(H(2)O)(2)亚基被四个H(2)O分子包围。铜(+)的气相配位数为2，生成的线性配位结构是进一步溶剂化过程的核心。
M(+)(H(2)O)(n) and M(+)(H(2)O)(n)Ar ions (M=Cu and Ag) are studied for exploring coordination and solvation structures of noble-metal ions. These species are produced in a laser-vaporization cluster source and probed with infrared (IR) photodissociation spectroscopy in the OH-stretch region using a triple quadrupole mass spectrometer. Density functional theory calculations are also carried out for analyzing the experimental IR spectra. Partially resolved rotational structure observed in the spectrum of Ag(+)(H(2)O)(1) x Ar indicates that the complex is quasilinear in an Ar-Ag(+)-O configuration with the H atoms symmetrically displaced off axis. The spectra of the Ar-tagged M(+)(H(2)O)(2) are consistent with twofold coordination with a linear O-M(+)-O arrangement for these ions, which is stabilized by the s-d hybridization in M(+). Hydrogen bonding between H(2)O molecules is absent in Ag(+)(H(2)O)(3) x Ar but detected in Cu(+)(H(2)O)(3) x Ar through characteristic changes in the position and intensity of the OH-stretch transitions. The third H(2)O attaches directly to Ag(+) in a tricoordinated form, while it occupies a hydrogen-bonding site in the second shell of the dicoordinated Cu(+). The preference of the tricoordination is attributable to the inefficient 5s-4d hybridization in Ag(+), in contrast to the extensive 4s-3d hybridization in Cu(+) which retains the dicoordination. This is most likely because the s-d energy gap of Ag(+) is much larger than that of Cu(+). The fourth H(2)O occupies the second shells of the tricoordinated Ag(+) and the dicoordinated Cu(+), as extensive hydrogen bonding is observed in M(+)(H(2)O)(4) x Ar. Interestingly, the Ag(+)(H(2)O)(4) x Ar ions adopt not only the tricoordinated form but also the dicoordinated forms, which are absent in Ag(+)(H(2)O)(3) x Ar but revived at n=4. Size dependent variations in the spectra of Cu(+)(H(2)O)(n) for n=5-7 provide evidence for the completion of the second shell at n=6, where the dicoordinated Cu(+)(H(2)O)(2) subunit is surrounded by four H(2)O molecules. The gas-phase coordination number of Cu(+) is 2 and the resulting linearly coordinated structure acts as the core of further solvation processes.