Azobenzene and its derivatives are among the most commonly used switching units in organic chemistry. The switching process consists of two states, in which the trans isomer has a stretched and the cis isomer a compact form. Here, we have designed a system in which all isomeric states of an azobenzene moiety (trans → cis-(M) → cis-(P)) are passed step by step. The first step involves a change in the distance between the benzene units, which is common for azobenzene derivatives. In the second step an inversion of the helicity (M→P) of the cis azobenzene unit takes place. The third step leads back to the stretched trans isomer. This switching cycle is achieved by coupling the azobenzene unit with two chiral clamps and with a further azobenzene switching unit.

Most metallo-supramolecular assemblies of low nuclearity adopt simple topologies, with bridging ligands spanning neighboring metal centers in a direct fashion. Here we contribute a new structural motif to the family of host compounds with low metal count (two) that consists of a pair of doubly-interlocked, Figure-eight-shaped subunits, also termed "lemniscates". Each metal is chelated by two chiral bidentate ligands, composed of a peptidic macrocycle that resembles a natural product with two pyridyl-terminated arms. DFT calculation results suggest that dimerization of the mononuclear halves is driven by a combination of 1) Coulomb interaction with a central anion, 2) p-stacking between intertwined ligand arms and 3) dispersive interactions between the structures compact inner core bedded into an outer shell composed of the cavitand-type macrocycles. The resulting cage-like architecture was characterized by NMR, MS and Xray structure analyses. This new mechanically bonded system highlights the scope of structural variety accessible in metalmediated self-assemblies composed of only a few constituents.

Oligomers of azole peptides have been isolated from a multitude of marine organisms. Up to now, these azole-containing dipeptide-analogue oligomers have only been found as cyclic n-mers (mostly tri- and tetramers) in nature. Herein, we show that imidazole-containing pseudopeptides form helixlike secondary structures in different solvents. The screw sense of the helix can be determined by attaching a single chiral imidazole unit to the N terminus of the oligomer. Investigation by means of circular dichroism (CD) spectroscopy showed that the folding process of the helix depends on the water content of the solvent in a parabolic way. In a pure organic medium, the helix is stabilized by hydrogen bonds between the hydrogen atoms of the amide groups and the nitrogen atoms of the azole ring. In aqueous solution, the formation of the helix is driven by dispersion interactions. The formation of the helix is more pronounced in aqueous solution than in organic solvents.

Polyynes show as trictly linear relationship between the energy impact and the bending of the polyyne chain. The energy,w hich is necessary to bend the acetylenic chain, decreases with the increasing number of acetylene units. Ad eviation from linearity in polyynes can be realizedi ns olution by violation of the mutual-exclusion principle betweenI Ra nd Raman spectra. However,t here is still no possibility to measure the extent of the nonlinearity in solution. Herein, we show that the 13 CNMR spectroscopy represents an appropriate tool for this as we found an almost perfect linear relationship between the bendingo ft he alkyne chain and the change of the chemical shift of the outer acetylenic carbon atoms. By using molecular bows in which the alkyne chain can be bent by switching the azobenzene unit, this correlation can be proved experimentally.I nt he future, this correlation should enablet he determination of the extent of the bendinga nd the strain energyi np olyynes. Consequently, polyynes could be employed as probesf or measuring further molecular forces.Polyynes consisting of alternate single and triple bonds can be found in interstellar space, in plants,m ushrooms,a nd in marine organisms. [1] They are also used intensively as building blocks for materials and in supramolecular chemistry. [2] Investigationso ft he stabilityo fp olyynes revealt hat the reactivity regardingt heir dimerization [3] and decomposition increases with growingc hain length. [4] Therefore, it is necessary for the synthesis of higherp olyynest oa ttach large, sterically demanding end-capping groups in order to preventd ecomposition of the polyyne. [5] Using this strategy the synthesis and isolationo fa polyyne with 22 conjugatedt riple bonds wasachieved. [6] With increasing number of acetylene units, the energy of the bending vibration along the molecular axis decreases and, therefore, ad eviation from the linearityo ft he molecular struc-

Cyclic oligomers of azole peptides can be isolated from marine organisms and are used for a multitude of applications in supramolecular chemistry. They are used in particular as receptors, since the recognition units attached to these azole cyclopeptides show a predefined orientation to each other. Here we present the synthesis of an imidazole cyclopeptide showing a switchable behavior due to the incorporation of two azobenzene moieties into the macrocycle. The synthesis, in particular the cyclization to the macrocycle proved to be difficult. However, by using an optimized route the platform could be isolated in a rather good yield (32 %). Quantum chemical calculations, UV and NMR spectra showed that the platform can be light‐inducedly switched between the elongated trans,trans isomer and the compact cis,cis isomer. This switching process leads to a drastic change in the distance between the methyl groups attached to the imidazole rings.