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OK, as it seems neither the manual nor google find an answer, maybe "you" as a community have an idea.

Can I draw an aromatic ring with a delocalised bond (attached to the ring) in ChemFig?

One example would be the anion interaction in Wikipedia: https://en.wikipedia.org/wiki/Pi_interaction#Anion_.CF.80-interactions

In my case I am interested in representing the isomers of cresols using a single molecule notation which is commonly done by showing a bond between the OH and the aromatic ring.

Not sure if this shows for the non-academics, a figure in a paper. The last molecule is a cresol and the type of molecule I'm interested in, ideally with a proper aromatic ring: http://onlinelibrary.wiley.com/enhanced/figures/doi/10.1002/cphc.200700563#figure-viewer-sch1

For those that want a minimum working example, here is a a single cresol in LaTex/ChemFig:

\documentclass[11pt,a4paper]{article}%

%\usepackage[version=4]{mhchem}
\usepackage{chemfig}
\setatomsep{2em}
%\usepackage{siunitx}
%\sisetup{range-phrase=-,range-units=single}

\begin{document}
\chemfig{
**6(-(-OH)---(-)--)
}
\end{document}
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1 Answer 1

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With a recent version of chemfig, you can make use of the node name cyclecenter<n> (where <n> is the serial number of the relevant ring) in a \chemmove command to refer to the center of a ring drawn in the previous \chemfig command. This way, you can reproduce the molecule like in the paper you refer to. With a little TikZ magic, you can "break" the ring at the relevant position where the line crosses it:

\documentclass[border=10pt]{standalone}
\usepackage{chemfig}
\setchemfig{atom sep=2em}

\begin{document}
\chemfig{
    *6(-=-(-CH_3)=-=)
}
\chemmove{
    \draw[-] (cyclecenter1) -- +(1,0) 
        node[right, inner sep=2pt] {\printatom{OH}};
}

\bigskip

\chemfig{
    *6(-=-(-CH_3)=-=)
}
\chemmove{
    \draw[-, preaction={draw, white, line width=3pt}] 
        (cyclecenter1) -- +(1,0) 
        node[right, inner sep=2pt] {\printatom{OH}};
}
\end{document}

enter image description here


You can also set different TikZ options to the \chemfig drawing using the atom style option, such as yscale to achieve an effect similar to that of the molecule in the linked Wikipedia article (if you don't want to use cram bonds like in the answers linked in the comments):

\documentclass[border=10pt]{standalone}
\usepackage{chemfig, mathtools}
\setchemfig{atom sep=2em}

\begin{document}
\rule{0pt}{1.5cm} % add some space

\chemfig[atom style={yscale=0.5}]{
    *6(-=-=-=)
}
\chemmove{
    \draw[-, densely dotted, thick] (cyclecenter1) -- +(0,1) 
        node[above, inner sep=2pt] {\printatom{X^{\mathrlap{-}}}};
}
\end{document}

enter image description here

Here as well, you could use the preaction trick to "break" the circle:

\documentclass[border=10pt]{standalone}
\usepackage{chemfig, mathtools}
\setchemfig{atom sep=2em}

\begin{document}
\rule{0pt}{1.5cm} % add some space

\chemfig[atom style={yscale=0.5}]{
    *6(-=-=-=)
}
\chemmove{
    \draw[-, densely dotted, thick, preaction={draw, white, line width=3pt}] 
        (cyclecenter1) -- +(0,1) 
        node[above, inner sep=2pt] {\printatom{X^{\mathrlap{-}}}};
}
\end{document}

enter image description here

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