Hierarchical Dehydrogenation Reactions on a Copper Surface

Abstract

Hierarchical control of chemical reactions is being considered as one of the most ambitious and challenging topics in modern organic chemistry. In this study, we have realized the one-by-one scission of the X-H bonds (X = N and C) of aromatic amines in a controlled fashion on the Cu(111) surface. Each dehydrogenation reaction leads to certain metal-organic supramolecular structures, which were monitored in single-bond resolution via scanning tunneling microscopy and noncontact atomic force microscopy. Moreover, the reaction pathways were elucidated from X-ray photoelectron spectroscopy measurements and density functional theory calculations. Our insights pave the way for connecting molecules into complex structures in a more reliable and predictable manner, utilizing carefully tuned stepwise on-surface synthesis protocols.

On‐Surface Driven Formal Michael Addition Produces m‐Polyaniline Oligomers on Pt(111)

“…Theabove-described mechanism is based on asequence of different dehydrogenation reactions in amine moieties and carbon rings,w hich have been previously described to take place stepwise at different temperatures on different surfaces. [31,48,49] Moreover,the proposed mechanism, confirmed by DFT calculations,explains why coupling occurs at adifferent site than the radical formation, as one could expect ap riori. We show that although para-precursors are used the bonding with the surface changes the coupling position resulting in a meta-coupling of the chains.…”

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 .…”