Coordination Polymers with Intramolecular Fluorine-Involved Contacts in Two-Dimensional Sheet Windows

Six two-dimensional polymeric complexes of [Hg- (L2-F](2)](n),0 1, [Hg(L-2,L-5-F](n), 2, [Hg(L3-F)(2)](n), 3, [Hg(L-2,L-3,L-4-F)(2)](n), 4., [Hg(L-3,L-4,L-5-F)(2)](n), 5, and [Hg(L-2,L-3,L-4,L-5-F](2)](n), 6 and a discrete complex of [Hg(L-2,L-6-F)(2)], 7, in which Ln-F ligands are N-(fluorinatedpheny1)-2pyrazinecarboxamides carrying fluorine atoms on the different positions of phenyl ring, have been synthesized and characterized. The crystal structures from X-ray diffraction reveal that all polymeric complexes have similar two-dimensional (2D) sheet windows. From a topological perspective, each metal atom can be viewed as 4-connected nodes and 0 ligands can be considered as linkers in the formation of these 2D windows. Because of the flexibility of the ligand, fluorinated-phenyl rings as hanging groups in the windows are pointed toward the adjacent groups to generate different fluorine-involved intramolecular interactions. One of the common features in the crystal structures of these complexes is the presence of a strong tendency to form intramolecular F center dot center dot center dot pi interactions in 2D windows of the crystal structure of all polymeric complexes, except complex 3. These interactions are cooperating with weak C-H center dot center dot center dot F and C-H center dot center dot center dot O hydrogen bonds. Also, in the crystal structure of complexes 5 and 6, carrying three and four fluorine atoms on phenyl rings, type II F-F synthons between adjacent rings have been observed in cooperation with F center dot center dot center dot pi interactions. Hirshfeld surface analysis also confirms that the F center dot center dot center dot F/pi contacts are predominant.