钴超分子络合物中的氢键相互作用——^(59)Co核磁共振研究及分子模拟(英文)

HYDROGEN BONDING INTERACTION IN COBALTIC SUPRAMOLECULAR COMPLEXES—STUDIED ^(59)Co NMR AND MOLECULAR MODELLING

钴超分子络合物[12]aneN_4[Co(CN)_6],[18]aneN_6[Co(CN)_6],[24]aneN_8[Co(CN)_6],[16]aneN_4[Co(CN)_6],[24]aneN_6[Co(CN)_6]以及[32]aneN_8[Co(CN)_6]中,氢键相互作用的程度与它们在水溶液中的构象密切相关,从而引起^(59)Co的化学位移向高场移动,并且其四极矩耦合作用也随构象发生了变化。实验证明,络合物中的氢键越强,化学位移越向高场移动,四极矩耦合作用也越大。另一方面,尺寸大的超分子具有较长的分子转动相关时间,也导致^(59)Co具有较短的纵向弛豫时间。简而言之,^(59)Co核磁共振不仅在小分子甚至在超分子络合物中都可以用作理想的探针研究分子的次层或弱相互作用。

The hydrogen bonding interactions in a series of cobaltic supramolecular complexes [12]aneN_4 [Co(CN)_6], [18]aneN_6 [Co(CN)_6 ], [24]aneN_8 [Co (CN)_6], [16]aneN_4 [Co(CN)_6], [24]aneN6_ [Co(CN)_6] and [32]aneN_8 [Co (CN)_6 ] were studies and found to be closely related to the molecular conformations in the aqueous solution. Such interactions caused the ^(50)Co chemical shifts to move towards upfield, and the quadrupolar interaction to change as well. It was observed in this study that stronger hydrogen bonding resulted in larger upfield shift of the ^(50)Co chemical shifts and higher quadrupolar interaction in the cobaltic supramolecular complexes. On the other hand, larger supramolecular sizes resulted in longer molecular rotational correlation time τ_c and shorter ^(59)Co longitudinal relaxation time (T_1). In summary, ^(59)Co NMR proves to be an ideal probe to investigate the second sphere or weak interaction in the cobaltic supramolecular complexes in addition to the small molecules.