NCAFM2023 Programme Booklet

Tuesday 1420 - 1440

SULFOXIDE MOLECULES STUDIED BY ncAFM ON METAL END INSULATING SUBSTRATES

M.Hankache 1 , V.Magné 3 , E.Geagea 1 , P.Simon Marqués 2 , S.Clair 1 , F.Para 1 , L.Giovanelli 1 , J.Bonvoisin 2 , G.Rapenne 2 , E.Maerten 3 , O.Thillaye du Boullay 3 , C.Kammerer 2 , D.Madec 3 , L.Nony 1 , and C.Loppacher 1

1-Aix-Marseille University, CNRS, IM2NP, UMR 7334, Marseille, France 2- CEMES, Université de Toulouse, CNRS, Toulouse, France 3- LHFA, CNRS, UMR 5069, Toulouse, France Email: Christian.Loppacher@im2np.fr

Due to their photoreactivity in solution, sulfoxide (S-oxide) molecules are promising organic precursor molecules for the development of novel routes for on-surface synthesis, for example by means of deoxy¬genation under UV-illumination [1]. We studied two sulfoxide derivatives, the dibenzothiophene S-oxide (DBTSO, Fig. 1), as well as its dibrominated derivate (ortho-Br) 2 -DBTSO (Fig. 3). The two Br atoms were attached, first, to serve as polar anchoring groups to increase the molecule-substrate interaction on ionic crystal substrates, and second, to permit Ullmann coupling to create larger, covalently bond fibers on metal substrates. The latter are more stable for tip-induced deoxygenation by for example voltage pulses. Our results comprise a detailed study on the adsorption mechanisms on NaCl(001) and Au(111) substrates, as well as on ultrathin NaCl layers on Au(111). By means of high-resolution imaging with CO functionalized tips we conclude that the molecules adsorb with their oxygen atom of the sulfoxide group oriented to the surface of Au(111) (Fig. 1). Furthermore, we observe the organization of the molecules, and we determine the interactions which guide the self-assembly on all substrates. On Au(111) we investigate isolated molecules (Fig. 1), octamers stabilized by halogen bonding, monolayers (Fig. 2) as well as covalently bond fibers. On NaCl(001) bulk (Fig. 3) and thin films, we investigate self-assembled monolayers. Finally, we discuss the effect of both, voltage pulses applied by the tip as well as UV-illumination on the deoxygenation.

Fig. 1 : Δf image acquired in constant-height mode above a DBTSO molecule on Au(111). CO-tip.

Fig. 3: Δf image of (o-Br)2-DBTSO on bulk NaCl(001), dual-pass mode.

Fig. 2 : STM image of DBTSO on Au(111).

References [1] Mrinmoy Nag and William S. Jenks, «Photochemistry of Substituted Dibenzothiophene Oxides: The Effect of Trapping Groups», J. Org. Chem. 2005, 70 (9), 3458-3463

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