Adaptation toward Restricted Conformational Dynamics: From the Series of Neutral Molecular Rotors
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- 作者：Palanisamy Rajakannu ; Bhaskaran Shankar ; Anju Yadav ; Ramasamy Shanmugam ; Deepak Gupta ; Firasat Hussain ; Che-Hao Chang ; Malaichamy Sathiyendiran ; Kuang-Lieh Lu
- 刊名：Organometallics
- 出版年：2011
- 出版时间：June 13, 2011
- 年：2011
- 卷：30
- 期：11
- 页码：3168-3176
- 全文大小：1019K
- 年卷期：v.30,no.11(June 13, 2011)
- ISSN：1520-6041
文摘
A semirigid ligand, 1,4-bis(2-nonylbenzimidazol-1-ylmethyl)benzene (Nbenzbix), containing a long alkyl chain substituted stator and a rotating unit was designed and synthesized. Three dinuclear metallacycles [(Re(CO)3)(渭-L)(渭-Nbenzbix)(Re(CO)3)] (1, H2-L = H2-dhnq = 6,11-dihydroxy-5,12-naphthacenedione; 2, H2-L = H2-dhaq = 1,4-dihydroxy-9,10-anthraquinone; and 3, H2-L = H2-CA = 2,5-dichloro-3,6-dihydroxy-p-benzoquinone) were synthesized from Re2(CO)10, Nbenzbix, and H2-L units. Compounds 1鈥?b>3 and the ligand Nbenzbix were characterized by elemental analysis, FT-IR, and 1H NMR spectroscopy. Compound 1 was further characterized by a single-crystal X-ray diffraction analysis. The dynamic properties of 1鈥?b>3 in solution were studied using variable-temperature 1H NMR spectroscopy, and the findings indicate that the p-phenylene unit in the metallacycle rotates in solution. To prevent the stator units from undergoing conformational changes due to the syn/anti arrangement of the benzimidazolyl units, a long-chain alkyl group was introduced at the 2-position of the benzimidazolyl unit. Molecular modeling calculations indicate that the energy barrier for the p-phenylene rotating unit in the metallacycle would be very low. Hence, these neutral metallacycles can be regarded as surface-mounted altitudinal rotors in which the bischelating unit is related to the surface, the nonylbenzimidazolyl units are related to the stators, and the p-phenylene is related to the rotating unit.