Btukfyl

I'm trying to get this kind of appearance for chemical structure (see highlighted regions):

By so far I could manage to do like this:

This is my code:

documentclass[12pt]{standalone}

usepackage{tikz}

usepackage{fontspec}

setmainfont{Times New Roman} 



usepackage{chemfig}

usepackage[version=3]{mhchem}

usetikzlibrary{arrows,shadows,calc,shapes,backgrounds,intersections,positioning} 

makeatletter

defCF@node@content{%

expandafterexpandafterexpandafter

printatomexpandafterexpandafterexpandafter

{csname atom@numberCF@cnt@atomnumberendcsname}%

ensuremath{CF@node@strut}%

}

makeatother

setdoublesep{0.35700 em}  % 'Bond Spacing'

setatomsep{1.78500 em}    % 'Fixed Length'

setbondoffset{0.18265 em} % 'Margin Width'

newcommand{bondwidth}{0.06642 em} % 'Line Width'

setbondstyle{line width = bondwidth}

renewcommand*{printatom}[1]{{sffamilycf{#1}}}

begin{document}

begin{tikzpicture}[font=small ,line width=1pt,node distance=1cm, inner sep=-0.05cm]

node[anchor=north] at(0,0){ 

chemname{

chemfig{[:135]Ru?[o](-[,2.2]N*6([:80]=-=-*6(=<=>(-*6([:-120]-=(-*6(-=-(-*6(=*6(-=-=-)-=-*6(-=-=-)=-))=-=-))-=([:-80]-*6(=-=-*6(-=-[,,,,line width=2pt]=N?[o,{-}]-)=-))-N?[o,{-}]=))=)--))([:45]-[,2.2]N*6([:100]-*6(-(-*6([:-60]-N?[o,{-}]=([:-100]-*6(=*6(-N?[o,{-}]=-=-)-=<=>-))-=(-*6(=-=(-*6(-*6(-=-=-)=-=*6(-=-=-)-=))-=-))-=))=-@{tr}=-=)--=-[,,,,line width=2pt]=))}}{textbf{large 2}}

chemmove{draw[very thick,inner sep=0pt](tr)++(1cm,-.1cm)--++(0,2em)node[anchor=north west,yshift=-4mm]{$sf left(PF_{6}right)_2$}--++(-2em,0);}

};

path (0,.5)--++(2,0);

path (0,-6.5)--++(1,0);

end{tikzpicture}

end{document}

How I could achieve the appearance I want using chemfig?

I'd draw the bold single bonds with the line-width command -[,,,,line width=2pt].
A bold double bond can be achieved by drawing a bold single bond backwards (angle = 180°) over the double bond: -[::180,,,,line width=2pt].

Here is an example:

documentclass[a4paper]{scrreprt}

usepackage[utf8]{inputenc}



usepackage{chemfig}

renewcommand*printatom[1]{smallensuremath{mathsf{#1}}}

setatomsep{16.5pt}

setbondstyle{line width=0.6pt}

setcrambond{3pt}{0.6pt}{1.5pt}

setdoublesep{2.6pt}

setbondoffset{1.6pt}

setarrowdefault{,1.0,}



begin{document}



chemfig{*6(=(-[::180,,,,line width=2pt])-(*6(=-=(-NH_2)-(-*6(=(-NHTs)(-[::180,,,,line width=2pt])-[,,,,line width=2pt]=(-[::180,,,,line width=2pt])-(*6(=-=-=-))--))=-))--=(-[::180,,,,line width=2pt])-[,,,,line width=2pt])}



end{document}

I am not really an expert on pgf and tikz so probably this can be done even better. But here is my solution, where I define a new style of the bond.

Inspired by Creating delocalized double bonds in chemfig without tikzset? and Passing parameters to pgfdeclaredecoration

documentclass[a4paper]{article}



usepackage{chemfig}

usetikzlibrary{decorations}



makeatletter

pgfdeclaredecoration{halfbold}{initial}{%

state{initial}[width=0.5*pgfdecoratedpathlength,next state=final]{%

pgfsetlinewidth{5pgflinewidth}

pgfpathmoveto{pgfpoint{0}{0}}

pgfpathlineto{pgfpoint{pgfdecoratedpathlength}{0}}

pgfusepathqstroke

pgfsetlinewidth{tikzscope@linewidth}

pgfpathmoveto{pgfpoint{2pt}{4pt}}

pgfpathlineto{pgfpoint{0.9*pgfdecoratedpathlength}{4pt}}

pgfusepathqstroke

}

state{final}{%

pgfpathmoveto{pgfpoint{0pt}{0pt}}

pgfpathlineto{pgfpoint{0.5*pgfdecoratedpathlength}{0}}}}

makeatother



tikzset{myrbond/.style={decorate, decoration=halfbold}}

tikzset{mylbond/.style={decorate, decoration={halfbold, mirror}}}



setatomsep{4em}



begin{document}



chemfig{[:-30]R-C-[::60]C(-[::60,,,,,mylbond]O)-[,,,,myrbond]N(-[::-60]H)-[::60]C-R}



end{document}

You can adjust the thickness in the line pgfsetlinewidth{5pgflinewidth} and the distance between the double bonds on lines

pgfpathmoveto{pgfpoint{2pt}{4pt}}

pgfpathlineto{pgfpoint{0.9*pgfdecoratedpathlength}{4pt}}

But I am really not sure, if this is a better (or nicer) solution that the one proposed by @dieg0

I achieved a nice result.
This is my commented code:

documentclass[10pt]{article}

pagestyle{empty} % required

usepackage{chemfig}



renewcommand{familydefault}{sfdefault}

usepackage[scaled=1]{helvet}

usepackage[helvet]{sfmath}

everymath={sf}



begin{document}

    setchemfig{

        atom sep=15pt,

        double bond sep=2.6pt,

        bond join=true,

        cram width=3.0pt,

        cram dash width=0.75pt,

        cram dash sep=2.0pt

    }



    chemfig{

        Ru?[Ru] % central atom (with hook)

        % 1st moiety (left)

        (-[:180,3.25,,,dash pattern=on 2pt off 2pt] % long dashed bond to pyridyl  left ring

        N*6(=( % pyridyl ring

        -[::-45] % to avoid stay too close to Ru atom

        *6(=( % 1st 8-quinolyl ring (upper left benzene ring)

        *6(-N?[Ru,,{dash pattern=on 2pt off 2pt}]=-=-) % 8-quinolyl (pyridine ring, with hook to Ru bond)

        )-=<=( % 1st 8-quinolyl ring (continuation)

        -[::0,0.1,,,draw=none]-[::180,1.2,,,line width=2pt] % bold bond as a branch

        )>)) % 1st 8-quinolyl (end)

        -=(-R_{1})-= % pyridyl (continuation)

        (-[::-75] % to avoid stay too close to Ru atom

        *6(=-=-( % 2nd 8-quinolyl ring (lower left)

        *6(- % benzene ring

        (-[::60,1.01,,,line width=2pt]-[::60,1.01,,,line width=2pt]) % bold bond as a branch

        =-=N?[Ru,,{dash pattern=on 2pt off 2pt}] % 8-quinolyl (pyridine ring, with hook to Ru bond)

        (-[::180,1.05,,,line width=2pt])-))=-)) % bold N= bond as a branch

        -)) % Ending the 1st moiety

        %

        % 2nd moiety (right, same as above)

        (-[:0.0,3.25,,,dash pattern=on 2pt off 2pt]

        N*6(=(

        -[::-45]

        *6(=(

        *6(-N?[Ru,,{dash pattern=on 2pt off 2pt}]=-=-)

        )-=<=(

        -[::0,0.1,,,draw=none]-[::180,1.2,,,line width=2pt]

        )>))

        -=(-R_{2})-=

        (-[::-75]

        *6(=-=-(

        *6(-

        (-[::60,1.01,,,line width=2pt]-[::60,1.01,,,line width=2pt])

        =-=N?[Ru,,{dash pattern=on 2pt off 2pt}]

        (-[::180,1.05,,,line width=2pt])-))=-))

        -))

    }       

end{document}

The final result: