Control of the Intermolecular Coupling of Dibromotetracene on Cu(110) by the Sequential Activation of CBr and CH Bonds

Abstract

Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions.

Strain‐Induced Isomerization in One‐Dimensional Metal–Organic Chains

“…Thed issociation of this bond allows the system to reach the relaxed configuration by releasing the stress of the intermediate structure.I mportantly,o ur calculations also reveal av ertical movement of approximately 0.4 of the whole naphthalene unit as aconsequence of the activation of out-of-plane molecular vibration modes at elevated temperatures.T he temperature-induced vertical movement facilitates the reaction greatly by lowering the activation barrier.T his clearly illustrates the importance of performing free energy calculations at elevated temperatures when seeking to correctly describe on-surface reaction mechanisms and the associated entropic effects. C À Cu À Cb ond cleavage and C À Hb ond activation on catalytically active substrates typically require thermal treatment at over 400 K. [26][27][28][29] They are often followed by direct CÀCc oupling, leading to the formation of graphene-like nanostructures. [5,6] However, unlike the 2D MOC networks reported previously,t he 1D strained MOCs studied here undergo C À Cu À Cb ond cleavage at room temperature as part of acomplex reaction driven by the relief of substrate-induced strain.…”

Strain‐Induced Isomerization in One‐Dimensional Metal–Organic Chains

“…C−Cu−C bond cleavage and C−H bond activation on catalytically active substrates typically require thermal treatment at over 400 K . They are often followed by direct C−C coupling, leading to the formation of graphene‐like nanostructures .…”

Synthesis of armchair graphene nanoribbons from the 10,10′-dibromo-9,9′-bianthracene molecules on Ag(111): the role of organometallic intermediates

“…It is known that on copper and silver surfaces the dehalogenated precursors usually tend to assemble into partly covalent organometallic (OM) intermediates prior to purely covalent C–C coupling. These intermediate structures are composed of molecular units linked through the C–M–C bonds 41 – 47 , 50 – 53 , 60 . In particular, OM chains were observed on Cu(111) surface after deposition of DBBA molecules at room temperature (RT) followed by a complete debromination of DBBA 34 , 58 , 61 .…”