1. Cation and anion binding studies using DFT calculations, ESI-MS and NMR
Farooq A. Khan, Department of Chemistry, University of West Georgia
The compound 1 was synthesized by Dr. Megumi Fujita and co-workers with support from ACS-PRF. The binding properties of 1 were investigated in collaboration with Dr. Fujita theoretically (DFT) and experimentally. In ESI-MS studies, alkali metal ions were found to bind with 1 with intensities Li+ ~ Na+ > K+. In separate anion binding studies with halide ions, the intensities of adducts were Cl- > Br- > I-.
The association constants Ka (M-1) of the formation of 1•X- adducts from 1 and Bu4NX (X = F, Cl, Br, I) based on NMR titrations of in CD3CN are shown below.
1•Li+
1•Cl-
Negative-ion ESI mass spectrum
of 1:5 mole ratio of 1:Cl- in methanol.
Halide F-
Cl-
Br- I- Ka -
1042±21
157±9
12±1
DFT calculations were carried out to study cation and anion binding. The ditopic nature of binding is supported by both NMR studies and DFT calculations.
The outcome of these studies were accepted for publication in Tetrahedron Letters.
1•Cl-•Li+
DFT-optimized structures: Color scheme: Gray = C,
white = H, blue = N, scarlet = Br, green = Cl and
pink = Li. Some H atoms are omitted for clarity.
Positive-ion ESI mass spectrum of
1:5 mole ratio of 1:NaPF6 in methanol.