C-F…M
+ interaction was clearly shown by using fluorinated macrocyclic cage compounds. The interaction was proved by complexation studies, spectroscopic measurements (
1H,
19F,
13C NMR), and X-ray crystallographic analyses. By the complexation, specific spectroscopic changes were observed. Especially, Cs
+ and Tl
+ complexes showed F…M
+ spin couplings. In the crystal structure, short F…M
+ contacts were observed, and C-F bond distances are elongated by the complexation. The C-F unit acts as an efficient donor in the complexes, which was proved by estimating bond valences (C-F…M
+, O.-M
+, and N.-M
+) of the cations by Brown's equation. The nature of the C-F…M
+ interaction was proved to be a cation-dipole interaction, and coordination bond is weak in this case.
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