Structural Insight into Guest Binding Sites in a Porous Homochiral Metal鈥揙rganic Material
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- 作者：Shi-Yuan Zhang ; Lukasz Wojtas ; Michael J. Zaworotko
- 刊名：Journal of the American Chemical Society
- 出版年：2015
- 出版时间：September 23, 2015
- 年：2015
- 卷：137
- 期：37
- 页码：12045-12049
- 全文大小：503K
- ISSN：1520-5126
文摘
An enantiomeric pair of chiral metal鈥搊rganic materials (CMOMs) based upon mandelate (man) and 4,4鈥?bipyridine (bpy) ligands, [Co2(S-man)2(bpy)3](NO3)2路guest (1S路guest) and [Co2(R-man)2(bpy)3](NO3)2路guest (1R路guest), have been prepared. The cationic frameworks exhibit one-dimensional chiral channels with dimensions of 8.0 脜 脳 8.0 脜. The pore chemistry is such that chiral surfaces lined with nitrate anions and phenyl groups create multiple binding sites for guest and/or solvent molecules. The performance of 1S and 1R with respect to resolution of racemic mixtures of 1-phenyl-1-propanol (PP) was studied by varying time, temperature, and the use of additives. Selectivity toward PP was determined by chiral HPLC with ee values of up to 60%. The binding sites and host鈥揼uest interactions were investigated through single-crystal X-ray structural analyses of guest-exchanged 1S and 1R. Crystallographically observed structural changes (e.g., the absolute configurations of the three PP binding sites switch from R, R, and S to R, R, and R/S) correlate with experimentally observed ee values of 33% and 60% for variants of 1S that contain PP and different solvent molecules, 1S路PPex and 1S路PPex鈥?/b>, respectively. The fact that manipulation of guest solvent molecules, which in effect serve as cofactors, can modify chiral sites and increase enantioselectivity is likely to aid in the design of more effective CMOMs and processes for chiral separations.