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The design, synthesis and operation of a readily accessible two-state switch are demonstrated. The switch initially exists in an intramolecularly hydrogen-bonded self-locked state, as evidenced by the solution-state NMR and solid-state structure. The switch can be reversibly altered between anti–anti and syn–anti conformations by adding and removing Cu+ ions, as evidenced by the NMR and crystallographic study. The anti–anti form was found to be catalytically active in the Michael addition reaction, whereas the syn–anti form was catalytically inactive. [ABSTRACT FROM AUTHOR]

NetState I of the communication-catalysis protocol is defined by a 1 : 1 mixture of the nanoswitches [Cu(1)]+ and 2. Upon one-electron oxidation at the ferrocenyl unit of the switch [Cu(1)]+, copper(i) ions are released that after translocation toggle nanoswitch 2→ [Cu(2)]+ (NetState II) within 4 min. NetState I was fully reset within 1 min by reduction of 1+→ 1. Running this redox-triggered switching protocol in the presence of 4-nitrobenzaldehyde, diethyl malonate and piperidine (catalyst) allows toggling of a catalyzed Knoevenagel addition from ON to OFF and back to ON. [ABSTRACT FROM AUTHOR]

A triangular framework with a terpyridine and shielded phenanthroline at its termini constitutes an open/close nanoswitch that is toggled by chemical inputs. In the presence of copper(I) ions, the open triangular framework (OPEN-I) firmly closes to a catalytically inactive heteroleptic [Cu(phen)(terpy)]+ complex (CLOSE). Reversible switching between CLOSE and OPEN-I states was demonstrated by successive addition and removal of Cu+. In contrast, after addition of iron(II) ions to the CLOSE state a bishomoleptic dimeric [Fe(terpy)2]2+ complex is formed with the copper(I) ions placed in the phenanthroline cavities (OPEN-II). Due to its coordinatively unsaturated [Cu(Phen)]+ sites the dimeric iron complex is able to serve as a catalyst in the cyclopropanation of Z-cyclooctene using ethyl diazoacetate. [ABSTRACT FROM AUTHOR]

Dual coordination at two distinct nitrogen binding sites in various ditopic azabipyridines and azaterpyridines was evaluated by preparing 3- and 4-component complexes. The 4-aza-2,2′-bipyridine unit was implemented into a nanoswitch and used for reversible switching between open and closed forms. [ABSTRACT FROM AUTHOR]

Over years, mathematicians, biologists and chemists have capitalised on the highly useful concept of orthogonality for developing sophisticated complex systems. The use of orthogonal pairs ensures that any modification made on one pair does not propagate any effect onto the other. While the concept equally pertains to dynamic supramolecular interactions, interference-free self-assembly built on multiple orthogonal interactions is still limited and the underlying notions are not yet firmly established. Herein, we identify, classify and evaluate dynamic interactions in various orthogonal settings in order to distill out general recommendations for reliable dynamic orthogonality. Our classification has to exclude templating, allosteric and/or cooperative effects as the latter are specific for individual cases only. [ABSTRACT FROM AUTHOR]

Structural characterization in on-surface synthesis is primarily carried out by Scanning Probe Microscopy (SPM) which provides high lateral resolution. Yet, important fresh perspectives on surface interactions and molecular conformations are gained from adsorption heights that remain largely inaccessible to SPM, but can be precisely measured with both elemental and chemical sensitivity by Normal-Incidence X-ray Standing Wave (NIXSW) analysis. Here, we study the evolution of adsorption heights in the on-surface synthesis and post-synthetic decoupling of porous covalent triazine-phenylene networks obtained from 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (TBPT) precursors on Ag(111). Room temperature deposition of TBPT and mild annealing to ∼150 °C result in full debromination and formation of organometallic intermediates, where the monomers are linked into reticulated networks by C-Ag-C bonds. Topologically identical covalent networks comprised of triazine vertices that are interconnected by biphenyl units are obtained by a thermally activated chemical transformation of the organometallic intermediates. Exposure to iodine vapor facilitates decoupling by intercalation of an iodine monolayer between the covalent networks and the Ag(111) surface. Accordingly, Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and NIXSW experiments are carried out for three successive sample stages: organometallic intermediates, covalent networks directly on Ag(111) and after decoupling. NIXSW analysis facilitates the determination of adsorption heights of chemically distinct carbon species, i.e. in the phenyl and triazine rings, and also for the organometallic carbon atoms. Thereby, molecular conformations are assessed for each sample stage. The interpretation of experimental results is informed by Density Functional Theory (DFT) calculations, providing a consistent picture of adsorption heights and molecular deformations in the networks that result from the interplay between steric hindrance and surface interactions. Quantitative adsorption heights, i.e. vertical distances between adsorbates and surface, provide detailed insight into surface interactions, but are underexplored in on-surface synthesis. In particular, the direct comparison with an in situ prepared decoupled state unveils the surface influence on the network structure, and shows that iodine intercalation is a powerful decoupling strategy.

NetState I of the communication-catalysis protocol is defined by a 1 : 1 mixture of the nanoswitches [Cu(1)] + and 2. Upon one-electron oxidation at the ferrocenyl unit of the switch [Cu(1)] + , copper(i) ions are released that after translocation toggle nanoswitch 2 → [Cu(2)] + (NetState II) within 4 min. NetState I was fully reset within 1 min by reduction of 1+ → 1. Running this redox-triggered switching protocol in the presence of 4-nitrobenzaldehyde, diethyl malonate and piperidine (catalyst) allows toggling of a catalyzed Knoevenagel addition from ON to OFF and back to ON.

The pyridine-pyrimidine (py-pym) arm as the moving part of the two-state nanomechanical rotary switch [Cu(1)](+) is toggled reversibly between two stations using one-electron oxidation/reduction. In state I, the arm is attached via Cu(+) complexation to a sterically encumbered phenanthroline and in state II to a zinc porphyrin station. Toggling is realised by charging and discharging an external input signal, the ferrocene-appended diimine ligand 2. Addition of 2 leads to formation of the intermolecular complex [Cu(1)(2)](+) paralleled by a move of the py-pym arm to the zinc porphyrin station. Upon oxidation at the ferrocenyl unit, 2(+) detaches from [Cu(1)(2)](2+) so that [Cu(1)](+) is formed in state I. Switching was ascertained by NMR, UV-Vis spectroscopy and cyclic voltammetry.

A potential-controlled two-step bidirectional communication protocol between the nanoswitches [Cu(1)](+), 2 and 3 is set up, in which ligand followed by metal-ion oxidation drives two subsequent metal ion translocations (self-sorting) changing the switching state at each switch. The communication is reset to its starting point by a two-electron reduction.

The two states of a new nanomechanical switch were quantitatively and reversibly populated in several subsequent switching cycles using either Cu(+) or cyclam as chemical inputs. State II was demonstrated to cis-trans isomerise diazastilbene upon irradiation selectively in the presence of stilbene, and even to operate as a photocatalyst.