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.