Abstract
Two new maleimide derivatives have been synthesized, prone to self-assemble and react with graphene as dienophiles. Both compounds bear a long alkyl chain on the carbon-carbon double bond position 3. The maleimide 1 bears a second alkyl chain at the nitrogen, while in compound 2, three maleimide functionalities are linked to a triethynylbenzene core.
Highlights
Chemical functionalization of graphene is essential [1] for future practical applications of this attractive material and it has been recently shown that its peculiar electronic structure allows it to react both as a diene or a dienophile in Diels-Alder reaction, permitting a large variety of additions in relatively mild conditions [2]
Different disconnections can be envisaged for the alkyl-functionalized maleic anhydride 3. The synthesis of this kind of derivatives has largely been studied in the literature, due to their interesting biological activity [17]
It is possible to assume that the protonated and deprotonated forms are in equilibrium: the so formed carbanion a can act as a Michael donor and attack maleic anhydride in position 3, to give an adduct b that after a sequence of reactions (β-elimination, ring opening and decarboxylation) yields the 1-pyridine-3-dodecyl-4-methyl functionalized maleimide d
Summary
Chemical functionalization of graphene is essential [1] for future practical applications of this attractive material and it has been recently shown that its peculiar electronic structure allows it to react both as a diene or a dienophile in Diels-Alder reaction, permitting a large variety of additions in relatively mild conditions [2]. Current work in progress involves the [2 + 2] and [2 + 4] cycloadditions of several maleimides with graphene on silicon carbide surfaces or with graphene flakes supported on silicon dioxide In this context, we recently synthesized the derivatives 1 and 2 where the dienophile groups are functionalized maleimides. The first maleimide derivative of the series, 1, bears two alkyl chains –C12H25 directly connected to the core at positions 1 and 3 (Figure 1). The maleimide reactive groups are born by a triethynylbenzene platform This kind of aromatic core is chosen for two reasons: (1) it favors the molecular adsorption on the surface thanks to π-π interactions; (2) it allows the tuning of reactive sites density on the surface by varying the length of the phenyl-ethynyl spacers. The role of the alkyl chain –C12H25 is to promote the adsorption on the surface by establishment of CH-π interactions
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