Visualisation of Aromaticity and Antiaromaticity

Dylan has finished his MChem project entitled “Visualisation of Aromaticity and Antiaromaticity via the Computation of the Chemical Shielding on Multi-Dimensional Grids.” You can find his report here. The purpose of his project was to develop a convenient method for computing shielding tensors on a grid around a molecule. The developed code is available via github.

Below, an analysis of biphenylene is shown in the singlet (a) and triplet (b) state. For the singlet this representation highlights the aromaticity (red) of the benzene rings whereas the central 4-membered ring is found to be antiaromatic (blue). In the triplet (b), the whole molecule is found to be aromatic (red) according to Baird’s rule.

An analysis of norcorrole using either its doubly protonated form (a) or a nickel complex (b) highlights the antiaromaticity at the centre of this molecule whereas an aromatic pathway is found at the perimeter (see also [P. B. Karadakov, Org. Lett. 2020, 22, 8676]).

For more examples of how this type of analysis is used in the literature, see e.g., [Angew. Chemie – Int. Ed. 2020, 59, 19275] and [ChemPhysChem 2021, 22, 741].

Welcome Dylan

Dylan Morgan joined the group to work on his MChem project: “Visualisation of Aromaticity in Macrocycles”. The project is inspired by recent findings that anti-aromaticity in macrocycles provides a promosing route for the design of new battery anodes.

Aromaticity, despite its ubiquity in the discussions, is still surprisingly hard to visualise and quantify. We will endeavour to compare the different available techniques – nucleus-independent chemical shifts, current density plots, and the GIMIC method – with the goal of identifying the most promising ones and streamlining the workflows. In particular, we are interested in 1D, 2D, or even 3D scans of NICS values as inspired by a recent paper on excimers.

Welcome Dylan!

New functionality for OpenMolcas

An update of the WFA module has been posted to OpenMolcas. This update integrates the fragment-based analysis that was previously only available via the TheoDORE code. In particular, it allows the automatic analysis of excited-state character in transition metal complexes [1, 2] with just a few added lines in the input file to OpenMolcas. This functionality is described here.

Thank you to Feng Chen from Loughborough University’s Research Software Engineering program for implementing the new code.

Release of TheoDORE 2.0 (beta)

Version 2.0 of the TheoDORE wavefunction analysis package has been released, download below. The two main features of TheoDORE 2.0 are the computation of conditional electron densities and compatibility with python3.

Conditional electron densities can be used for the visualisation of excited-state electron correlation, see ChemPhotoChem (2019). Below, the application of this method to a PPV oligomer is shown. Here, the probe hole (red) is always fixed on the terminal phenyl ring and the different shapes for the conditional electron density (blue) for the first six excited states is observed. One can see that for the different states the electron is either repelled, attracted or unaffected by the hole.

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