A simple method of identifying π orbitals for non-planar systems and a protocol of studying π electronic structure


The characteristic of π electrons has a crucial role in determining various properties of chemical systems, such as reactivity, aromaticity and spectroscopy. There are a large number of methods could be used for investigating π electronic structure, for example, the well-known electron localization function and multicenter bond order. For completely planar systems, the π molecular orbitals can be unambiguously identified and thus studying their π electronic structure is easy. However, for non-planar systems, identification of π orbitals and then analysis of π electrons are often not trivial. In this work, based on localized molecular orbitals (LMOs), we propose a conceptually simple and easy way to automatically identify π orbitals for any kind of systems, which makes subsequent analyses of π electrons straightforward. In addition, we show that the identified π LMOs can also be used to reliably estimate π component of molecular orbitals or other kinds of orbitals. The method proposed in this work has been implemented into our wavefunction analysis code Multiwfn as a key ingredient of standard analysis protocol for π electrons. Application examples given in this article illustrated that this protocol makes analysis of π electronic structure for a wide variety of chemical systems unprecedentedly convenient and reliable.

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    For manual corresponding to Multiwfn Version 3.7, see section 4.100.22 on how to perform analyses similar to this work. The steps of realizing topology analysis of ELF-π is illustrated in section 4.5.3. The way of rendering isosurface maps by VMD program based on the data calculated by Multiwfn is introduced in section 4.A.14. The manual is freely available at http://sobereva.com/multiwfn Accessed on 30 Sep 2019

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Lu, T., Chen, Q. A simple method of identifying π orbitals for non-planar systems and a protocol of studying π electronic structure. Theor Chem Acc 139, 25 (2020). https://doi.org/10.1007/s00214-019-2541-z

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  • Orbital localization
  • Electron structure
  • Electron localization function
  • Multiwfn
  • Localized orbital locator
  • Electron density
  • π electron
  • Bond order