Structure of Host-Guest Complexes between Dibenzo-18-Crown-6 and Water, Ammonia, Methanol, and Acetylene: Evidence of Molecular Recognition on the Complexation
Structure of Host-Guest Complexes between Dibenzo-18-Crown-6 and Water, Ammonia, Methanol, and Acetylene: Evidence of Molecular Recognition on the Complexation
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二苯并-18-冠-6 与水、氨、甲醇和乙炔之间的主客体配合物的结构：配合物分子识别的证据
DOI：
10.1039/c0cp02523b
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
and T. Ebata
中科院分区：
文献类型：
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作者：
R. Kusaka;S. Kokubu;Y. Inokuchi;T. Haino;and T. Ebata
采用激光诱导荧光（LIF）、UV-UV烧孔（UV-UV HB）和IR-UV双共振（IR-UV DR）光谱对二苯并-18-冠-6 （DB18C6，主体）与水、氨、甲醇和乙炔（客体）在超音速射流中的配合物进行了表征。首先，我们重新研究了裸DB18C6（物种m1和m2）和DB18C6 - h2o（物种a）的结构[R]。Kusaka， Y. Inokuchi， T. Ebata, Phys。化学。化学。理论物理。用红外- uv - DR光谱测量亚甲基甲烷拉伸振动区[j] .光子学报，2008,10,638。DB18C6 - h2o的亚甲基CH链的红外光谱特征与裸DB18C6构象明显不同，表明DB18C6在与水分子形成配合物时改变了构象。借助蒙特卡罗模拟进行广泛的构象搜索和密度泛函计算（M05-2X/6-31+G*），我们将m1和m2分别重新分配给具有C1和C2对称性的构象。同时，我们也证实了DB18C6 - h2o中a种的DB18C6部分为“船型”构象（C2v）。其次，结合LIF和UV-UV HB光谱，我们分别鉴定了9个、1个和2个DB18C6与氨、甲醇和乙炔配合物。从亚甲基CH拉伸区的红外光谱测量中，在db18c6 -氨配合物中发现了类似的构象变化，但在与甲醇或乙炔配合物中没有发现。通过分析OH、NH和CH拉伸振动区域的电子跃迁能、激子分裂和红外光谱来确定所有配合物的结构。在db18c6 -氨配合物中，氨分子通过形成“分叉”和“双齿”氢键（h键）被纳入船形构象的空腔中，类似于DB18C6-H2O配合物的情况。另一方面，在db18c6 -甲醇和-乙炔配合物中，甲醇分子和乙炔分子分别简单地附着在C1和C2构象上。从DB18C6构象的不同取决于客体分子的类型，可以得出DB18C6在形成配合物时将水和氨与甲醇和乙炔区分开来，这取决于客体分子是否具有形成双齿氢键的能力。
Complexes of dibenzo-18-crown-6 (DB18C6, host) with water, ammonia, methanol, and acetylene (guest) in supersonic jets have been characterized by laser induced fluorescence (LIF), UV-UV hole-burning (UV-UV HB), and IR-UV double resonance (IR-UV DR) spectroscopy. Firstly, we reinvestigated the conformation of bare DB18C6 (species m1 and m2) and the structure of DB18C6–H2O (species a) [R. Kusaka, Y. Inokuchi, T. Ebata, Phys. Chem. Chem. Phys., 2008, 10, 6238] by measuring IR-UV DR spectra in the region of the methylene CH stretching vibrations. The IR spectral feature of the methylene CH stretch of DB18C6–H2O is clearly different from those of bare DB18C6 conformers, suggesting that DB18C6 changes its conformation when forming a complex with a water molecule. With the aid of Monte Carlo simulation for extensive conformational search and density functional calculations (M05-2X/6-31+G*), we reassigned species m1 and m2 to conformers having C1 and C2 symmetry, respectively. Also, we confirmed the DB18C6 part in species a of DB18C6–H2O to be “boat” conformation (C2v). Secondly, we identified nine, one, and two species for the DB18C6 complexes with ammonia, methanol, and acetylene, respectively, by the combination of LIF and UV-UV HB spectroscopy. From the IR spectroscopic measurement in the methylene CH stretching region, a similar conformational change was identified in the DB18C6–ammonia complexes, but not in the complexes with methanol or acetylene. The structures of all the complexes were determined by analyzing the electronic transition energies, exciton splitting, and IR spectra in the region of the OH, NH, and CH stretching vibrations. In DB18C6–ammonia complexes, an ammonia molecule is incorporated into the cavity of the boat conformation by forming “bifurcated” and “bidentate” hydrogen-bond (H-bond), similar to the case of the DB18C6–H2O complex. On the other hand, in the DB18C6–methanol and –acetylene complexes, methanol and acetylene molecules are simply attached to the C1 and C2 conformations, respectively. From the difference of the DB18C6 conformations depending on the type of the guest molecules, it is concluded that DB18C6 distinguishes water and ammonia from methanol and acetylene when it forms complexes, depending on whether guest molecules have an ability to form bidentate H-bonding.