A study of the surface assisted self-assembly of 1,2,4,5-tetracyanobenzene （TCNB） acceptor molecules and Fe atoms on an Au（111） surface is presented. While conditions to get the two-dimensional arrays of stable Fe...A study of the surface assisted self-assembly of 1,2,4,5-tetracyanobenzene （TCNB） acceptor molecules and Fe atoms on an Au（111） surface is presented. While conditions to get the two-dimensional arrays of stable Fe（TCNB）4 complexes are clearly identified, ultrahigh vacuum scanning tunneling microscopy and spectroscopy （STM/STS） coupled with first-principles calculations reveals that situations may occur where Fe and TCNB survive on the surface （as Fe-4TCNB entities） at a higher density than the original molecular monolayer without forming coordination bonds with each other. It is found that the square planar coordination of the Fe（TCNB）4 monomer complexes cannot fully develop in the presence of lateral strain due to growth-induced confinement. A phenomenon similar to steric hindrance involving a strongly modified chirality with a Fe-N-C bond angle of 120° compared to the 180° for the stable complex may then explain why the Fe atom keeps its metallic bond with the surface. The competition between steric and electronic effects, not reported before, may arise elsewhere in surface chemistry involved in the synthesis of new and potentially useful organic nanomaterials.展开更多
On-surface synthesis under ultrahigh vacuum provides a promising strategy to control matter at the atomic level, with important implications for the design of new two-dimensional materials having remarkable electronic...On-surface synthesis under ultrahigh vacuum provides a promising strategy to control matter at the atomic level, with important implications for the design of new two-dimensional materials having remarkable electronic, magnetic, or catalytic properties. This strategy must address the problem of limited extension of the domains due to the irreversible nature of covalent bonds, which prevents the ripening of defects. We show here that extended materials can be produced by a controlled co-deposition process. In particular, co-deposition of quinoid zwitterion molecules with iron atoms on a Ag（111） surface held at 570 K allows the formation of micrometer-sized domains based on covalent coordination bonds. This work opens up the construction of micrometer-scale single-layer covalent coordination materials under vacuum conditions.展开更多
文摘A study of the surface assisted self-assembly of 1,2,4,5-tetracyanobenzene （TCNB） acceptor molecules and Fe atoms on an Au（111） surface is presented. While conditions to get the two-dimensional arrays of stable Fe（TCNB）4 complexes are clearly identified, ultrahigh vacuum scanning tunneling microscopy and spectroscopy （STM/STS） coupled with first-principles calculations reveals that situations may occur where Fe and TCNB survive on the surface （as Fe-4TCNB entities） at a higher density than the original molecular monolayer without forming coordination bonds with each other. It is found that the square planar coordination of the Fe（TCNB）4 monomer complexes cannot fully develop in the presence of lateral strain due to growth-induced confinement. A phenomenon similar to steric hindrance involving a strongly modified chirality with a Fe-N-C bond angle of 120° compared to the 180° for the stable complex may then explain why the Fe atom keeps its metallic bond with the surface. The competition between steric and electronic effects, not reported before, may arise elsewhere in surface chemistry involved in the synthesis of new and potentially useful organic nanomaterials.
文摘On-surface synthesis under ultrahigh vacuum provides a promising strategy to control matter at the atomic level, with important implications for the design of new two-dimensional materials having remarkable electronic, magnetic, or catalytic properties. This strategy must address the problem of limited extension of the domains due to the irreversible nature of covalent bonds, which prevents the ripening of defects. We show here that extended materials can be produced by a controlled co-deposition process. In particular, co-deposition of quinoid zwitterion molecules with iron atoms on a Ag（111） surface held at 570 K allows the formation of micrometer-sized domains based on covalent coordination bonds. This work opens up the construction of micrometer-scale single-layer covalent coordination materials under vacuum conditions.
