Noncovalent Z···Z (Z=O, S, Se, and Te) Interactions: How Do They Operate to Control Fine Structures of 1,8-Dichalcogene-Substituted Naphthalenes?

Abstract Homonuclear Z···Z (Z=O, S, Se, and Te) interactions are investigated employing naphthalene 1,8-positions in 1,8-(MeZ)2C10H6 (1a–1d: Z=O (a), S (b), Se (c), and Te (d)), 1-MeZ-8-PhZC10H6 (2a–2c), and 1,8-(PhZ)2C10H6 (3a–3d). Three types of structures are detected for 1a–3d: BB for 1a, CC for 1b, 1c, 2c, and 3d, and AB for 2a, 2b, and 3a–3c, in our definition, by X-ray crystallographic analysis, although some have already been reported. Quantum chemical calculations are performed on 1a–1d and 3c, together with model c, Me(H)Se···Se(H)Me, to elucidate how the fine structures are controlled by the interactions. AB are stabilized by the np(Z)···σ*(Z–C) 3c–4e interactions for Z=S, Se, and Te. While CC are substantially stabilized by the n(Z)···σ*(Z–C) interactions, they are well summarized as the disappearance of the nodal plane in π*(Z···Z). Factors to control the fine structures are clarified and visualized using the HOMO or HOMO−1 of model c. The energy profile of model c helps us to imagine the whole picture of the noncovalent Se···Se interactions.