The self‐assembly properties of two ZnII porphyrin isomers on Cu(111) are studied at different coverage by means of scanning tunneling microscopy (STM). Both isomers are substituted in their meso‐positions by two voluminous 3,5‐di(tert‐butyl)phenyl and two rod‐like 4′‐cyanobiphenyl groups, respectively. In the trans‐isomer, the two 4′‐cyanobiphenyl groups are opposite to each other, whereas they are located at right angle in the cis‐isomer. For coverage up to one monolayer, the cis‐substituted porphyrins self‐assemble to form oligomeric macrocycles held together by antiparallel CN⋅⋅⋅CN dipolar interactions and CN⋅⋅⋅H‐C(sp2) hydrogen bonding. Cyclic trimers and tetramers occur most frequently but everything from cyclic dimers to hexamers can be observed. Upon annealing of the samples at temperatures >150 °C, dimeric macrocyclic structures are observed, in which the two porphyrins are bridged by Cu atoms, originating from the surface, under formation of two CN⋅⋅⋅Cu⋅⋅⋅NC coordination bonds. The trans‐isomer builds up linear chains on Cu(111) at low coverage, whereas for higher coverage the molecules assemble in a periodic, densely packed structure. Both cis‐ and trans‐bis(4′‐cyanobiphenyl)‐substituted ZnII porphyrins behave very differently on Cu(111) compared to similar porphyrins in literature on less reactive surfaces such as Au(111) and Ag(111). On the latter surfaces, there is no signal visible between molecular orientation and the crystal directions of the substrate, whereas on Cu(111), very strong adsorbate–substrate interactions have a dominating influence on all observed structures. This strong porphyrin–substrate interaction enables a much broader variety of structures, including also less favorable intermolecular bonding motifs and geometries.

Spinning tops: A supramolecular rotary device, reminiscent of a mechanical rotary switch, was engineered by a bottom‐up approach. Self‐assembly of a functionalized porphyrin molecule leads to the formation of a porous network that features chiral cavities. These serve as hosts for molecular guests, which can be induced to rotate either thermally or by using the scanning tunneling microscopy tip (see images).

The self‐assembly of three porphyrin derivatives was studied in detail on a Cu(111) substrate by means of scanning tunneling microscopy (STM). All derivatives have two 4‐cyanophenyl substituents in diagonally opposed meso‐positions of the porphyrin core, but differ in the nature of the other two meso‐alkoxyphenyl substituents. At coverages below 0.8 monolayers, two derivatives form molecular chains, which evolve into nanoporous networks at higher coverages. The third derivative self‐assembles directly into a nanoporous network without showing a one‐dimensional phase. The pore‐to‐pore distances for the three networks depend on the size and shape of the alkoxy substituents. All observed effects are explained by 1) different steric demands of the alkoxy residues, 2) apolar (mainly dispersion) interactions between the alkoxy chains, 3) polar bonding involving both cyanophenyl and alkoxyphenyl substituents, and 4) the entropy/enthalpy balance of the network formation.

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