Theoretical study on supramolecular chemistry of alkali-metal cations with crown ether derivatized thiophenes

This paper describes systemically a theoretical research on the interaction of alkali-metal cations (Li+, Na+, K+ and Rb+) with five different crown ether derivatized thiophenes using density functional theory (DFT). The fully optimized geometries have been performed with real frequencies which indicate the minima states. The optimized structures and electronic properties, such as HOMO and LUMO energies, bandgaps of the free ligands L (L-1-L-5), the complexes L/M+ (Li+, Na+, K+ and Rb+) have been performed at B3LYP/6-31+G(d, p) and Lanl2DZ level. Natural bond orbital (NBO) and frequency analysis are discussed on the basis of the optimized geometric structures. The main driving forces of the coordination in host-guest molecules are investigated, the electron-donating O or offers lone pair electrons to the contacting LP* (1-center valence antibond lone pair) of alkali-metal cations. In addition, the transition energies are calculated by the time-dependent density functional theory (TD-DFT).