The π···π Stacking Interactions between Homogeneous Dimers of C6FxI(6–x) (x = 0, 1, 2, 3, 4, and 5): A Comparative Study with the Halogen Bond

2012-12-27T00:00:00Z (GMT) by Weizhou Wang Yu Zhang Yi-Bo Wang
The π···π stacking interactions between homogeneous dimers of C6FxI(6–x) (x = 0, 1, 2, 3, 4, and 5) have been investigated in detail using the state-of-the-art quantum chemistry methods. Computations clearly show that the π···π stacking interaction between the homogeneous dimer of C6FxI(6–x) is of the dispersion type interaction. At the same time, it is interesting to find that, for the π···π stacking interactions between homogeneous dimers of C6FxI(6–x), the M05-2X/def2-TZVPP computations give almost the same results as the CCSD­(T)/SDD** computations. In the crystal growth and design, the formation of the π···π stacking interactions between homogeneous dimers of C6FxI(6–x) is always accompanied by the formation of the halogen bonds. Hence, competition and cooperation of the π···π stacking interaction and the halogen bond have also been studied theoretically by using C6FxI(6–x) and pyridine as coformers. At the M05-2X/def2-TZVPP theory level, it is found that the π···π stacking interactions in C6F5I···C6F5I and C6F4I2···C6F4I2 are weaker than the corresponding halogen bonds in C6F5I···NC5H5 and C6F4I2···NC5H5, and the π···π stacking interactions in C6FI5···C6FI5 and C6I6···C6I6 are stronger than the corresponding halogen bonds in C6FI5···NC5H5 and C6I6···NC5H5, while the strengths of the π···π stacking interactions in C6F3I3···C6F3I3 and C6F2I4···C6F2I4 are similar to the corresponding halogen bonds in C6F3I3···NC5H5 and C6F2I4···NC5H5. However, when the π···π stacking interaction and the halogen bond coexist, we find that the formation of the halogen bond will lead to the π···π stacking interaction much stronger, and vice versa.