Muraoka Azusa, Inokuchi Yoshiya, Nishi Nobuyuki, Nagata Takashi
Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
J Chem Phys. 2005 Mar 1;122(9):094303. doi: 10.1063/1.1850896.
The infrared photodissociation spectra of (CO(2))(n)(H(2)O)(m) (n=1-4, m=1, 2) are measured in the 3000-3800 cm(-1) range. The (CO(2))(n)(H(2)O)(1) spectra are characterized by a sharp band around 3570 cm(-1) except for n=1; (CO(2))(1)(H(2)O)(1) does not photodissociate in the spectral range studied. The (CO(2))(n)(H(2)O)(2) (n=1, 2) species have similar spectral features with a broadband at approximately 3340 cm(-1). A drastic change in the spectral features is observed for (CO(2))(3)(H(2)O)(2), where sharp bands appear at 3224, 3321, 3364, 3438, and 3572 cm(-1). Ab initio calculations are performed at the MP2/6-311++G(**) level to provide structural information such as optimized structures, stabilization energies, and vibrational frequencies of the (CO(2))(n)(H(2)O)(m) species. Comparison between the experimental and theoretical results reveals rather size- and composition-specific hydration manner in (CO(2))(n)(H(2)O)(m): (1) the incorporated H(2)O is bonded to either CO(2) (-) or C(2)O(4) (-) through two equivalent OH...O hydrogen bonds to form a ring structure in (CO(2))(n)(H(2)O)(1); (2) two H(2)O molecules are independently bound to the O atoms of CO(2) (-) in (CO(2))(n)(H(2)O)(2) (n=1, 2); (3) a cyclic structure composed of CO(2) (-) and two H(2)O molecules is formed in (CO(2))(3)(H(2)O)(2).
在3000 - 3800 cm⁻¹范围内测量了[(CO₂)ₙ(H₂O)ₘ]⁻（n = 1 - 4，m = 1, 2）的红外光解离光谱。[(CO₂)ₙ(H₂O)₁]⁻光谱的特征是除n = 1外，在3570 cm⁻¹附近有一个尖锐的谱带；[(CO₂)₁(H₂O)₁]⁻在研究的光谱范围内不会发生光解离。[(CO₂)ₙ(H₂O)₂]⁻（n = 1, 2）物种具有相似的光谱特征，在约3340 cm⁻¹处有一个宽带。对于[(CO₂)₃(H₂O)₂]⁻，观察到光谱特征发生了剧烈变化，在3224、3321、3364、3438和3572 cm⁻¹处出现了尖锐的谱带。在MP2/6 - 311++G(**)水平上进行了从头算计算，以提供[(CO₂)ₙ(H₂O)ₘ]⁻物种的结构信息，如优化结构、稳定化能和振动频率。实验结果与理论结果的比较揭示了[(CO₂)ₙ(H₂O)ₘ]⁻中相当特定于尺寸和组成的水合方式：(1) 在[(CO₂)ₙ(H₂O)₁]⁻中，掺入的H₂O通过两个等效的OH...O氢键与CO₂⁻或C₂O₄⁻键合，形成一个环状结构；(2) 在[(CO₂)ₙ(H₂O)₂]⁻（n = 1, 2）中，两个H₂O分子独立地与CO₂⁻的O原子结合；(3) 在[(CO₂)₃(H₂O)₂]⁻中形成了一个由CO₂⁻和两个H₂O分子组成的环状结构。
