Dimeric cation-cation aggregates stabilized by 2Ch-2N chalcogen bonds: Crystallographic and theoretical evidences

2Ch-2N chalcogen bonds (ChBs) between a pair of homocations were characterized via crystal structure database analysis and quantum chemical computations. We first collected several crystal structures consisting of such interactions from the Cambridge Structural Database (CSD). Then, based on the CSD survey results, a series of model homodimers of organic chalcogenated cations were selected to theoretically study inter-cation 2Ch-2N ChBs for the first time. The dicationic complexes under investigation are unfavorable but metastable in gas phase. Immersion of these systems in solvents leads to a remarkable increase in dimer stability and produces stable ChB complexes. 2Ch-2N interactions in gas phase generally exhibit a positive electrostatic component, while the orbital and dispersion terms play a stabilizing role. When immersed in the solvent medium, the electrostatic interaction becomes more favorable, and the solvent energy contributes significantly to the stability of the complexes, resulting in attractive cation-cation ChBs.