Double π–π stacking dynamics of benzene trimer cation: direct ab initio molecular dynamics (AIMD) study

Abstract

Mechanism of π–π double stacking process of benzene trimer cation has been investigated by means of direct ab initio molecular dynamics method. It was found that H-shaped form of neutral benzene trimer is drastically changed to the π–π double stacking form composed of benzene trimer cation following the ionization. Absorption spectrum of charge resonance band of (Bz) 3 + was gradually blueshifted as a function of time. Time scale of the double stacking process (the formation of trimer cation from the H-shaped form) was calculated to be 0.7–1.5 ps, which is comparable to that of dimer cation formation. After the ionization of benzene trimer, (Bz)(Bz)c(Bz′), the hole is distributed around three benzene molecules with a branching ratio of (Bz)+0.3(Bz)c+0.4(Bz′)+0.3, and the structure of (Bz)c+ was rapidly deformed due to the Jahn–Teller effect. Next, the molecular rotation of central benzene (Bz)c+ occurred gradually. Immediately, both benzene molecules in the wing positions were also rotated synchronicity. Finally, the π–π double stacking form composed of benzene trimer cation was formed. The formation mechanism of benzene trimer cation was discussed on the basis of theoretical results.