Abstract
The intrinsic dynamic and static nature m(c) center-n(e) electron interactions of the σ-type σ(m(c) c-n(e) e) were elucidated for the Se-Se interactions in dicationic oligomers of Se(CH(2) CH(2) CH(2) )(2) Se (1 (Se, Se)) [n(2+) (Se, Se): n=1-8], especially for m(c) ≥6, where n(2+) (Se, Se: n=1-8) are abbreviated by n(2+) (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(ii) ) were employed for QTAIM-DFA. Each Se-*-Se in 1(2+) and 2(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(2+) 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(2+) -8(2+) are r-CS/t-HB(wc) (typical-HB with covalency) but some are pure-CS/t-HB(nc) (t-HB with no covalency). The linear Se(2n) (2+) interactions in 2(2+) -8(2+) seem close to those without any limitations, since the nature of Se-*-Se inside and outside of (CH(2) CH(2) CH(2) )(2) are very similar with each other. The linear Se(2n) (2+) interactions in 3(2+) -8(2+) are shown to be analyzed as σ(m(c) c-n(e) e: 6≤m(c) ≤16), not by the accumulated σ(3c-4e).