Fluorine-containing donor-acceptor complexes:crystallographic study of the interactions between electronegative atoms(N,O,S)and halogen atoms(1,Br)

摘要

On the basis of our result,which concern sp~3N…Br-R_f[R_f=per(poly)fluoroalkyl],sp~3O…I-R_f,sp~2O…I-R_f,sp~3N…I-R_f,sp~2N…I-R_r and interactions of sp~2I-R_f with different substituents,a brief profile of the interactions between electronegative atoms(N,O,S)and halogen atoms(I,Br)of fluorine-containing alkylates is determined.The first example of an aliphatic fluorine-containing donor-acceptor supramolecule that is based on the N…Br-R_f interaction is reported in this paper.Our X-ray structure shows that 1,2-dibromotetrafluoroethane and 1,4-dimethylpiperazine alternately form endless chains depending on the N…Br-R_f interactions.The distance between Br and N is 2.864(3)A,which is considerably longer than the average covalent bond between N and Br,but it is also definitively shorter than the sum of the corresponding van der Waals radii of N and Br.Frm two other crystals,we successfully obtained precise data on the sp~3O…X-R_f and sp~2O…X-R_f interactions.Furthermore,an investigation of the substituent group effect is presented.We also report a valuable method to recrystallize and collect X-ray data of co-crystals that are easily disordered.