CSF - chemdraw compatibility

This release is inspired by the feedback to v1.0.0. The standard tool for chemists is ChemDraw, which has some free to use alternatives such as developing MolDraw. Therefore, some chemists suggested that it would be enormously useful if chemical structures could be imported from ChemDraw files (.cdxml or .mol). In addition, it was suggested that output of the relevant Clar structures as ChemDraw files would be a super nice feature, because this would allow users draw aromatic rings as circles and mark unpaired electrons with dots. We have implemented these features and added on-the-fly verification by a new stretchable inset presenting a 2D chemical structure formula ('H2O' button) and 3D ball & stick model ('cube' button) as shown in Figs. 1 and 2 below. These apparently simple changes, however, forced us to significantly revise the interface using minimalistic style to adjust more controllers into a limited space. Given these changes, we also re-brand the GUI as CSF that still stands for ClarStructureFinder. Finally, we have added a mouse tool that drops several vertices in a single click of the mouse left button, which facilitates building of regular polygons up to an octagon. Before dropping vertices, the polygons can be rotated by holding the mouse right button pressed.

Fig. 1: The 2D structural formula accompanying kekulene molecule analysis.

Fig. 2: The 3D representation of the kekulene molecule Clar's structure spanning the whole canvas.

The aromatic π-sextet

In organic chemistry, the Clar's aromatic sextet is a simple, intuitive and useful concept for structure analysis and properties prediction of polycyclic aromatic hydrocarbons (PAHs). Nevertheless, despite its over 50 years history, its usage has not been automated yet. This release bridges this obvious gap by delivering an interactive constructor of PAHs, including non-benzenoid ones, which may feature pentagonal or tetragonal defects etc., and a built-in analyzer of their structural properties in terms of aromatic π-sextets. This shall be useful in designs of novel polyradicaloids, including those possessing topological frustration Figs. 1 and 2, with peculiar magnetism suitable for spintronics and quantum computing applications.

Fig. 1: The Clar's structure analysis of a laterally extended Clar's goblet in the released GUI, see Nat. Synth (2026).

Fig. 2: The Clar's structure analysis of a triangulene dimer - results saved in .png via 'Save' button, see Angew. Chem. Int. Ed. 59, 12041 (2020).