Abstract
Dissymmetric reactions, which enable differentiated functionalization of equivalent sites within one molecule, have many potential applications in synthetic chemistry and materials science, but they are very challenging to achieve. Here, the dissymmetric reaction of 1,4-dibromo-2,5-diethynylbenzene (2Br-DEB) on Ag(111) is realized by using a stepwise activation strategy, leading to an ordered two-dimensional organometallic network containing both alkynyl–silver–alkynyl and alkynyl–silver–phenyl nodes. Scanning tunneling microscopy and density functional theory calculations are employed to explore the stepwise conversion of 2Br-DEB, which starts from the H-passivation of one Br-substituted site at 300 K in accompaniment with an intermolecular reaction to form one-dimensional organometallic chains containing alkynyl–silver–alkynyl nodes. Afterwards, the other equivalent Br-substituted site undergoes metalation reaction at 320–450 K, resulting in transformation of the chains into the binodal networks. These findings exemplify the achievement of the dissymmetric reaction and its practical application for controlled fabrications of complicated yet ordered nanostructures on a surface.
Highlights
Dissymmetric reactions, which enable differentiated functionalization of equivalent sites within one molecule, have many potential applications in synthetic chemistry and materials science, but they are very challenging to achieve
On-surface dissymmetric molecular adsorption and assembly dictated by substrate lattice mismatches have been reported[23], closing in achievement of differentiated chemical modifications of equivalent functional groups
A stepwise activation strategy is employed to mediate the dissymmetric reaction of 1,4-dibromo-2,5-diethynylbenzene (2Br-DEB, Fig. 1) on Ag(111) which leads to a binodal organometallic network on the surface
Summary
Dissymmetric reactions, which enable differentiated functionalization of equivalent sites within one molecule, have many potential applications in synthetic chemistry and materials science, but they are very challenging to achieve. Scanning tunneling microscopy and density functional theory calculations are employed to explore the stepwise conversion of 2Br-DEB, which starts from the H-passivation of one Br-substituted site at 300 K in accompaniment with an intermolecular reaction to form one-dimensional organometallic chains containing alkynyl–silver–alkynyl nodes. Three families of organometallic products resulted from the intermolecular metalations are phenyl–silver–phenyl (PSP), alkynyl–silver–phenyl (ASP) and alkynyl–silver–alkynyl (ASA) species Some of these reactions are involved in the conversion of 2Br-DEB on Ag(111) by sequential thermal treatment, resulting in the dissymmetric reactions of the two identical Br-substituted sites in the molecule step by step, as revealed by ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The reaction forms a 2D metal-organic hybrid structure containing two types of organometallic nodes These findings demonstrate that dissymmetric reaction can be employed to efficiently control on-surface preparations of complicated yet ordered nanostructures
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