On the Attosecond charge migration in Cl…..N, Cl…..O, Br…..N and Br…..O Halogen-bonded clusters: Effect of donor, acceptor, vibration, rotation, and electron correlation

Abstract

The electron-electron relaxation and correlation-driven charge migration process, which features pure electronic aspect of ultrafast charge migration phenomenon, occurs on a very short timescale in ionized molecules and molecular clusters, prior to the onset of nuclear motion. In this article, we have presented nature of ultrafast pure electronic charge migration dynamics through Cl…..N, Cl…..O, Br…..N, and Br…..O halogen bonds, explored using density functional theory. We have explored the role of donor, acceptor, electron correlation, vibration and rotation in charge migration dynamics through these halogen bonds. For this work, we have selected ClF, Cl2, ClOH, ClCN, BrF, BrCl, BrOH, and BrCN molecules paired with either NH3 or H2O. We have found that the timescale for pure electron-electron relaxation and correlation-driven charge migration through the Cl…..N, Br…..N, Cl…..O, and Br…..O halogen bonds falls in the range of 300–600 attosecond. The primary driving force behind the attosecond charge migration through the Cl…..N, Br…..N, Cl…..O, and Br…..O halogen bonds is the energy difference (ΔE) between two stationary cationic orbitals (LUMO- β and HOMO- β), which together represents the initial hole density immediately following vertical ionization. We have also predicted that the strength of electron correlation has significant effect on the charge migration timescale in Cl…..N, Br…..N, Cl…..O, and Br…..O halogen bonded clusters. Vibration and rotation are also found to exhibit profound effect on attosecond charge migration dynamics through halogen bonds. The attosecond charge migration dynamics through Cl…..N, Cl…..O, Br…..N, and Br…..O halogen bonds depends on strength of electron correlation, donor and acceptor, the energy difference (ΔE) between two stationary cationic orbitals (LUMO-β and HOMO-β) involved in electronic superposition, vibration and rotation.