Structures and cationic complexes of 18[(2,6)pyridino-6-corand-6] (‘sexipyridine’)

Abstract

The conformers of the title compound and its (gas phase) complexes with alkali metal cations and some molecular cations have been structurally optimized at HF/3-21G and HF/6-31G* levels of theory, with extended basis set single-point DFT calculations to include some of the effects of electron correlation. The only stable conformer found for the free macrocycle has D₃ symmetry, and stable complexes of the same symmetry are demonstrated for Na⁺ and K⁺. Stable complexes of lower (C₃) symmetry are also found for the possible template cations H₃O⁺ and NH₄⁺. Binding energies for the alkali metal cations ions are significantly larger than those found in comparable computational studies on structurally-related macrocycles. Finally, the complex with another potential template cation, C(NH₂)₃⁺, is also explored.