Atomic-scale perspective on individual thiol-terminated molecules anchored to single S vacancies in MoS2

Sulfur vacancies in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>MoS</a:mi><a:mn>2</a:mn></a:msub></a:math> on Au(111) have been shown to be negatively charged as reflected by a Kondo resonance. Here, we use scanning tunneling microscopy to show that these vacancies serve as anchoring sites for thiol-based molecules <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mo>(</b:mo><b:msub><b:mi>CF</b:mi><b:mn>3</b:mn></b:msub><b:mtext>−</b:mtext><b:mn>3</b:mn><b:mi mathvariant="normal">P</b:mi><b:mtext>−</b:mtext><b:mi>SH</b:mi><b:mo>)</b:mo></b:mrow></b:math> with two distinct reaction products, one of them showing a Kondo resonance. Based on comparisons with density-functional theory (DFT) calculations, including a random structure search and computation of energies and electronic properties at a hybrid exchange-correlation functional level, we conclude that both anchored molecules are charge neutral. We propose that one of them is an anchored intact <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msub><d:mi>CF</d:mi><d:mn>3</d:mn></d:msub><d:mtext>−</d:mtext><d:mn>3</d:mn><d:mi mathvariant="normal">P</d:mi><d:mtext>−</d:mtext><d:mi>SH</d:mi></d:mrow></d:math> molecule while the other one is the result of catalytically activated dehydrogenation to <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:msub><f:mi>CF</f:mi><f:mn>3</f:mn></f:msub><f:mtext>−</f:mtext><f:mn>3</f:mn><f:mi mathvariant="normal">P</f:mi><f:mtext>−</f:mtext><f:mi mathvariant="normal">S</f:mi></f:mrow></f:math> with subsequent anchoring. Our investigations highlight a perspective of functionalizing defects with thiol-terminated molecules that can be equipped with additional functional groups, such as charge donor or acceptor moieties, switching units, or magnetic centers.