Linear Multiselenium Interactions in Dicationic Oligomers of 1,5-(Diselena)canes: Behavior of Se σ(m c-n e) (6≤m ≤16) Elucidated with QTAIM Dual Functional Analysis.

The intrinsic dynamic and static nature m center-n electron interactions of the σ-type σ(m c-n e) were elucidated for the Se-Se interactions in dicationic oligomers of Se(CH CH CH ) Se (1 (Se, Se)) [n (Se, Se): n=1-8], especially for m ≥6, where n (Se, Se: n=1-8) are abbreviated by n (n=1-8), respectively. QTAIM dual functional analysis (QTAIM-DFA) was applied to the interactions. Perturbed structures generated using coordinates derived from the compliance constants (C ) were employed for QTAIM-DFA. Each Se--Se in 1 and 2 has the nature of CT-TBP (trigonal bipyramidal adduct formation through CT) and Cov-w (weak covalent), respectively, which supply the starting points of the investigations. The asterisk emphasizes the existence of a bond critical point on the interaction. All Se--Se in 3 are classified by the regular closed shell (r-CS) interactions and characterized as CT-MC (molecular complex formation through CT), which are denoted as r-CS/CT-MC, except for the central interaction, of which nature is r-CS/CT-TBP. Most interactions in 4 -8 are r-CS/t-HB (typical-HB with covalency) but some are pure-CS/t-HB (t-HB with no covalency). The linear Se interactions in 2 -8 seem close to those without any limitations, since the nature of Se-*-Se inside and outside of (CH CH CH ) are very similar with each other. The linear Se interactions in 3 -8 are shown to be analyzed as σ(m c-n e: 6≤m ≤16), not by the accumulated σ(3c-4e).