O–Li⋯O and C–Li⋯C lithium bonds in small closed shell and open shell systems as analogues of hydrogen bonds

Hydrogen bonded complexes and their lithium bonded analogues are investigated using DFT CAM-B3LYP quantum chemistry methods. The accuracy of DFT is verified by CCSD(T) calculations. Structures, binding energies, and Hirshfeld charge and spin densities for several charged closed shell and neutral open shell oxygen-containing complexes with O–H⋯O and O–Li⋯O bonds are compared. We also studied H-bonded and Li-bonded C–H⋯C and C–Li⋯C complexes in which the hydrogen and lithium bond donor and bond acceptor act through carbon-containing groups. Attention is paid to the bonding character in the model (H 3 C) 2 –CH–Li–CH–(CH 3 ) 2 (diisopropyllithium) doublet. Its binding energy with respect to the isopropyllithium and the isopropyl radical is −45 kJ/mol. The potential energy curve for the transfer of the lithium atom between the two carbon atoms shows double minima with a barrier of 11 kJ/mol. The Hirshfeld charge and spin density analysis shows that the charge transfer from the isopropyl radical to the isopropyllithium molecule occurs, and in combination with electrostatic interaction and (about 25 %) dispersion contribution are responsible for the formation of the Li-bonded (H 3 C) 2 –CH–Li–CH–(CH 3 ) 2 complex.