Abstract
Strain-induced on-surface transformations provide an appealing route to steer the selectivity towards desired products. Here, we demonstrate the selective on-surface synthesis of extended all-trans poly(2,6-pyridine) chains on Au(111). By combining high-resolution scanning tunneling and atomic force microscopy, we revealed the detailed chemical structure of the reaction products. Density functional theory calculations indicate that the synthesis of extended covalent structures is energetically favored over the formation of macrocycles, due to the minimization of internal strain. Our results consolidate the exploitation of internal strain relief as a driving force to promote selective on-surface reactions.
Highlights
On-surface synthesis of carbon-based nanostructures has rapidly emerged as a fascinating method for the synthesis of nanomaterials, with structures and functionalities not achievable by wet chemistry [1,2,3,4]
Intramolecular strain relief represents another appealing approach to promote the formation of desired molecular products as the on-surface planarization of distorted polycyclic aromatic hydrocarbons [14] and the synthesis of nanographene [15,16]
With density functional theory (DFT) calculations, we show that internal strain relief favors the formation of extended covalent chains composed of all-trans pyridines, while all-cis pyridine macrocycles represent only a minority of the surface products
Summary
On-surface synthesis of carbon-based nanostructures has rapidly emerged as a fascinating method for the synthesis of nanomaterials, with structures and functionalities not achievable by wet chemistry [1,2,3,4]. The close-packed Cu(111) surface was observed to steer the formation of covalent macrocycles, while Cu(110) favors the growth of extended structures [11,12]. Aiming at achieving extended nanostructures, intermolecular steric effects have been shown to play a crucial role in driving the sequential cyclohydrogenation reaction of polyantracene oligomers for the synthesis of graphene nanoribbons [17]. Surface by using 6,600 -dibromo-2,20 :60 ,200 -terpyridine (DBTP) molecules as precursors. With density functional theory (DFT) calculations, we show that internal strain relief favors the formation of extended covalent chains composed of all-trans pyridines, while all-cis pyridine macrocycles represent only a minority of the surface products. DBTP molecules were sublimed onto th sample surface at 300 K, followed by annealing to 470 K to initiate polym
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