Cfrgtkky

I want to draw the molecule attached with chemfig. Could not find anything for the core of the connections. Any idea?

Maybe not the answer you like but I do not know an elegant way to subject chemfig pictures to 3d projection that does not either nest tikzpictures or use saveboxes, in which case you can no longer access the nodes from outside. So I propose to draw the hexagons with elementary TikZ methods, and to use tikz-3dplot as well as the 3d library to do the projections. I acknowledge comments by andselisk, which clarified a couple of things for me which I did not know. I am not a chemist, so I do not know what a point group D_{3h} is, even though, like any marmot, I would know what a point group D_3 is. Anyway, this is an update with big thanks going to andselisk. (As requested, I add some explanations to the code. The idea is to use 3d coordinates and let TikZ do the projections. The tikz-3dplot package allows you to choose a view, defined by two angles, and the 3d library allows you to draw things in planes in 3d coordinates. So we are going to draw 3 hexagons in 3 planes which are rotated w.r.t. each other by 120 degrees. And then we are going to connect them in 3d. I added some annotations to the code.)

documentclass[tikz,border=3.14mm]{standalone}

usepackage{tikz-3dplot}

usetikzlibrary{shapes.geometric,3d,calc}

begin{document}

tdplotsetmaincoords{70}{20} % sets the view angles, see the tik-3dplot manual for details 

begin{tikzpicture}[tdplot_main_coords,% use the above view

hexa/.style={regular polygon, % just a hexagon shape; the corners are anchors

regular polygon sides=6,minimum size=3cm,draw}] 

foreach Z in {1,2,3} % Z labels three planes

{tdplotsetrotatedcoords{0}{Z*120}{0}

begin{scope}[tdplot_rotated_coords,transform shape,

canvas is yz plane at x=0] % switch to a rotated plane

  node[hexa] (hZ) at (0,{3*sin(60)}) {}; % draw a hexagon in the plane

  foreach X [evaluate=X as Y using {int(mod(X+1,6))}] in {2,4,6} 

  {draw ($(hZ.corner X)!0.2!(hZ.center)$) -- 

  ($(hZ.corner Y)!0.2!(hZ.center)$);} % draw thick hexagon edges

  draw[ultra thick] (hZ.corner 2) -- (hZ.corner 3) -- (hZ.corner 4);

% uncomment these out to see where the rotated coordinate axes point to

% begin{scope}[blue]

% draw[-latex] (0,0,0) -- (2,0,0) node[pos=1.1]{$x'$};

% draw[-latex] (0,0,0) -- (0,2,0) node[pos=1.1]{$y'$};

% draw[-latex] (0,0,0) -- (0,0,2) node[pos=1.1]{$z'$};

% end{scope}

 end{scope}

draw (hZ.corner 5) -- (0,{3*sin(60)/2},0); % thin connecting the 3 hexagons in the back

path (hZ.corner 4) -- (0,{-3*sin(60)/2},0) coordinate[midway](aux);

draw[ultra thick] (hZ.corner 4) -- (aux);

draw[double distance=1.6pt,ultra thick,white,double=black] (aux) --

(0,{-3*sin(60)/2},0); % draw the thick connections to the point between the

% three hexagons in the foreground (with "gaps" around the path

}

% uncomment these out to see where the main coordinate axes point to

% draw[-latex] (0,0,0) -- (3,0,0) node[pos=1.1]{$x$};

% draw[-latex] (0,0,0) -- (0,3,0) node[pos=1.1]{$y$};

% draw[-latex] (0,0,0) -- (0,0,3) node[pos=1.1]{$z$};

end{tikzpicture}

end{document}

The advantage of this is that you can change the view angle at will.

documentclass[tikz,border=3.14mm]{standalone}

usepackage{tikz-3dplot}

usetikzlibrary{shapes.geometric,3d,calc}

begin{document}

foreach ZZ in {5,15,...,355}

{tdplotsetmaincoords{70+20*sin(ZZ)}{ZZ}

pgfmathtruncatemacro{itest}{sign(cos(ZZ))}

begin{tikzpicture}[tdplot_main_coords,hexa/.style={regular polygon,regular polygon sides=6,

minimum size=3cm,draw}]

 path[tdplot_screen_coords,use as bounding box] (-5,-5) rectangle (5,5);

 foreach Z in {1,2,3}

 {tdplotsetrotatedcoords{0}{Z*120}{0}

 begin{scope}[tdplot_rotated_coords,transform shape,canvas is yz plane at x=0]

   node[hexa] (hZ) at (0,{3*sin(60)}) {};

   foreach X [evaluate=X as Y using {int(mod(X+1,6))}] in {2,4,6}

   {draw ($(hZ.corner X)!0.2!(hZ.center)$) -- ($(hZ.corner Y)!0.2!(hZ.center)$);}

   ifnumitest=1

    draw[ultra thick] (hZ.corner 2) -- (hZ.corner 3) -- (hZ.corner 4);

   else

    draw[ultra thick] (hZ.corner 1) -- (hZ.corner 6) -- (hZ.corner 5);

   fi  

  end{scope}

  ifnumitest=1

   path (hZ.corner 4) -- (0,{-3*sin(60)/2},0) coordinate[midway](aux);

   draw[ultra thick] (hZ.corner 4) -- (aux);

   draw[double distance=1.6pt,ultra thick,white,double=black] (aux) --

   (0,{-3*sin(60)/2},0);

   draw (hZ.corner 5) -- (0,{3*sin(60)/2},0);

  else

   path (hZ.corner 5) -- (0,{3*sin(60)/2},0) coordinate[midway](aux);

   draw[ultra thick] (hZ.corner 5) -- (aux);

   draw[double distance=1.6pt,ultra thick,white,double=black] (aux) --

   (0,{3*sin(60)/2},0);

   draw (hZ.corner 4) -- (0,{-3*sin(60)/2},0);

  fi 

 }

end{tikzpicture}}

end{document}

I always felt that some of the Star Wars space ships were inspired by molecules. This also explains why they can produce sound waves in vacuum.;-)