Song Le Xin, Wang Hai Ming, Guo Xue Qing, Bai Lei
Department of Chemistry, University of Science and Technology of China, Hefei, 230026 Anhui, China.
J Org Chem. 2008 Nov 7;73(21):8305-16. doi: 10.1021/jo801436h. Epub 2008 Oct 8.
Four fanlike organic compounds, 1-ethoxybenzene (EOB), 1-butoxybenzene (BOB), 1-dodecyloxybenzene (DOB), and 1-(dodecyloxy)-2-methoxybenzene (DOMB), were chosen as guests, and beta-cyclodextrin (beta-CD) and its two derivatives, mono(2-O-2-methyl)-beta-CD and mono(2-O-2-hydroxy-propyl)-beta-CD, were chosen as hosts. Energy changes involved in host-guest inclusion processes were clearly obtained by applying semiempirical PM3 calculations. According to this, probable structures of the host-guest inclusion complexes were proposed. The inclusion systems in aqueous solution were investigated by UV-vis spectroscopy and nuclear magnetic resonance ((1)H NMR) titration, and the formation constants (K) of the inclusion complexes were determined using the Benesi-Hildebrand equation. Moreover, two solid inclusion complexes of beta-CD with EOB and DOB were prepared and characterized by Fourier transform infrared spectra, X-ray powder diffraction, (1)H NMR, electrospray ionization mass spectrometry, and thermogravimetric analyses. Results showed that the host-guest stoichiometries in the inclusion complexes were all 1:1 both in solid state and in aqueous solution. As for the same host, the values of K increased in the order EOB < BOB < DOB, in strong association with the fan handle in the fanlike molecules; that is to say, the K values increased with increasing carbon chain length of substituent on benzene ring. In addition, the K values of DOMB complexes were larger than those of DOB complexes for the same CD, indicating that the introduction of an extra o-methoxyl group on DOB further stabilized the CD inclusion complexes. The decomposition activation energies of EOB-beta-CD and DOB-beta-CD were very similar but significantly larger than that of free beta-CD.
选择了四种扇形有机化合物，1-乙氧基苯（EOB）、1-丁氧基苯（BOB）、1-十二烷氧基苯（DOB）和1-（十二烷氧基）-2-甲氧基苯（DOMB）作为客体，选择了β-环糊精（β-CD）及其两种衍生物，单（2-O-2-甲基）-β-CD和单（2-O-2-羟丙基）-β-CD作为主体。通过应用半经验PM3计算清楚地获得了主客体包合过程中涉及的能量变化。据此，提出了主客体包合物的可能结构。通过紫外可见光谱和核磁共振（¹H NMR）滴定研究了水溶液中的包合体系，并使用贝内西-希尔德布兰德方程确定了包合物的形成常数（K）。此外，制备了β-CD与EOB和DOB的两种固体包合物，并通过傅里叶变换红外光谱、X射线粉末衍射、¹H NMR、电喷雾电离质谱和热重分析进行了表征。结果表明，包合物中的主客体化学计量比在固态和水溶液中均为1:1。对于同一主体，K值按EOB < BOB < DOB的顺序增加，与扇形分子中的扇柄密切相关；也就是说，K值随着苯环上取代基碳链长度的增加而增加。此外，对于相同的环糊精，DOMB配合物的K值大于DOB配合物的K值，这表明在DOB上引入额外的邻甲氧基进一步稳定了环糊精包合物。EOB-β-CD和DOB-β-CD的分解活化能非常相似，但明显大于游离β-CD的分解活化能。
