Can Transition Metals and Group II Mono- and Dications Discriminate between Homo- and Heterochiral XYYX’ Dimers (X,X’=H,Me; Y=O,S,Se)?†

We present a density functional theory and ab initio (MP2) study of stereoisomer discrimination between the homochiral and heterochiral dimers of the form M(XYYX’)2, where M is a cationic metal (Li+, Ca2+, Zn2+, Cu+, Cu2+) complexing chalcogen-chalcogen bridges (H2O2, H2S2, H2Se2, and their corresponding methyl and dimethyl derivatives). The heterochiral complexes examined were in general found to be more stable than the homochiral complexes, with the exception of several selenium-containing complexes. The large majority of the relative energy differences amounted to 1 kJ/mol or less, with the largest energy gap being 3.42 kJ/mol in the case of Ca2+(HSeSe(CH3))2 at B3LYP/aug-cc-pVTZ. Racemization mechanisms of these complexes and the description of their bonding using the Atoms in Molecules theory of Bader are also presented.