•A recent 50-years history of synthesis of 1+1 and 2+2 Schiff base and non-Schiff base macrocycles.•Developments in the design and synthesis of pyridine containing macrocycles.•The preparation of ...functionalized ligands containing pendant arms.•A summary of the new approach of these compounds such as mechanically interlocked molecules is reviewed.•The catalytic properties and cofactors and artificial metalloenzymes are also included.
In this paper, there is an attempt to review the developments in the design and synthesis of pyridine containing 1+1 and 2+2 macrocyclic Schiff base ligands, formed by condensations of 2,6-diacylpyridine or 2,6-diformylpyridine and appropriate polyamines, which utilize the templating capability of different metal ions to direct the synthetic pathway. The reduction of the cyclic Schiff bases to their related amine derivatives is also considered since this leads to more flexible ligands capable of structural elaboration through donor groups. Attention is mainly paid to the synthetic and structural aspects of the resulting metal complexes, particularly to the role of the coordination preferences of the different metal ions in directing the synthesis totally or preferentially toward mono-, di- or poly-nuclear entities. The preparation of functionalized ligands, containing pendant arms, capable of promoting rapid complexation and decomplexation and their use in selective metal ion transportation and separation are also paid attention to. Furthermore, a summary of the new approach of these compounds such as mechanically interlocked molecules, catalytic properties and cofactors and artificial metalloenzymes is reviewed.
Co and Fe complexes supported by a novel tetra-imine macrocycle were synthesized and characterized, and their solubility in polar organic solvents was explored.
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The syntheses and ...characterization of Fe and Co complexes supported by a new tetra-imine macrocycle, TEIM (2,3,9,10-tetraethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene), are reported. Templating with Co(OAc)2·4H2O yielded trans-Co(TEIM)Cl2PF6 (1a), which was converted to trans-Co(TEIM)X2PF6 (X = N3 (2a) and NO2 (3a)) through reactions with NaX (X = N3 or NO2). Templating with Fe generated trans-Fe(TEIM)(NCCH3)2PF62, which was oxidized to trans-Fe(TEIM)Cl2PF6 (1b). The reaction of 1b with NaN3 formed Fe(TEIM)(N3)2PF6 (2b) while the reaction with Fe(TEIM)(NCCH3)2PF62 and NaNO2 yielded trans-Fe(TEIM)(NO2)2 (3b). Single crystal X-ray diffraction studies revealed a pseudo-octahedral geometry around the Co / Fe centers with the ethyl groups oriented above or below the plane of the TEIM ring. The absorption spectra of 1b displays weak charge transfer bands near the UV to visible region, while 2b and 3b displayed intense charge transfer bands within the visible region. Cyclic voltammograms of 1a revealed four 1 e− reductions while those of 2a and 3a display only three cathodically shifted reductions. Analogous studies of 1b and 2b revealed two 1 e- reductions while 3b displays only an oxidation event. EPR studies of ferric complexes 1b and 2b indicated a low spin d5 electronic figuration with S = ½ ground state.
Think globally, act locally: The trade‐off between the global and local expression of aromaticity is demonstrated for a series of π‐conjugated macrocyclic furans of various sizes. Whereas smaller ...macrocycles are planar, larger macrocycles distort out of planarity, thereby avoiding global antiaromaticity, and display increasing character of local aromaticity. More information can be found in the Full Paper by O. Gidron et al. (DOI: 10.1002/chem.202103536).
Structural switching of 3catenane was induced by fitting the puzzle pieces. In their Research Article (202217002), Jun Terao et al. report a method for ligand‐controlled structural switching of ...3catenane, which was realized by the complexation of metal ions on 3catenane with added complementarily fitted organic ligands, like pieces in a jigsaw puzzle. The high tailorability of organic ligands offers multiple pieces with various sizes and numbers of coordination sites, enabling multistate structural switching of 3catenane.
Cu bound to Aβ (heads of the meteorites) produces reactive oxygen species (tails) that attack the brain. In the presence of the azamacrocyclic ligand 3N1S (the green belt), the Cu ions are removed by ...the ligand (the head of the meteorite is broken) and the ROS production is abolished (the tail disappears). Hence, the brain is safe behind its shield. In absence of 3N1S, the ROS produced by Cu(Aβ) attack the brain, which is “destroyed”. More information can be found in the Research Article by C. Esmieu, C. Hureau, and co‐workers (DOI: 10.1002/chem.202203667).
Siloxanes have evolved into a multi‐million dollar business due to their manifold of commercial and industrial applications. As siloxanes have high hydrophobicity, low basicity, high flexibility and ...also high chemical inertness in common, their chemistry differs significantly from that of organic ethers. The discovery of organic crown ethers, for instance, is commonly accepted as the birth of synthetic host‐guest chemistry. Regarding the chemical properties of siloxanes, cyclic siloxanes which formally resemble silicon analogues of crown ethers, have received considerably less interest in terms of their host‐guest chemistry. Hence, only little is known about siloxane coordination chemistry in the chemical community and the number of published works in this field has been very low till lately. In the last few years, the field has significantly advanced and elegant methods were established to enable the Si−O−Si unit for coordination. This review therefore summarizes the recent developments in the field, recapitulates the historical aspects of siloxane coordination chemistry and describes the specific Si−O bond character with regard to different siloxane linkages. Implications on Si−O bond activation are included and the limits of siloxane coordination are redefined.
Host guest‐chemistry with a variety of siloxane ligands has been established over the years. This review tackles the recent developments in the field, recapitulates the historical aspects of siloxane coordination chemistry and describes the specific Si−O bond character with respect to different siloxane linkages. Implications on Si−O bond activation are included, and the limits of siloxane coordination are redefined.
The Front Cover shows the open conformer of the 1,4‐phenanthroyl derivatized calix8arene/Cu(I) system that allows for C−S coupling to occur on the right hand side. On the left, a collapsed conformer ...of the same system does not allow for efficient catalysis to occur, since no macrocyclic cavity that may host the reactants is present. In the article, experimental and computational mechanistic studies are combined to unveil the origins for the poor catalytic performance in flexible macrocyclic systems with a vast conformational space. Thanks to @MESHICOLOR for the graphic design. More information can be found in the Research Article by M. Podewitz, I. Castillo and co‐workers.
The Front Cover shows a panorama from the so‐called Path of the Gods, a hiking trail in Southern Italy. At the end of the strenuous journey, the trekker is rewarded with a wonderful view of the ...Amalfi coast. The path to developing (cyclic) peptoids as therapeutic agents is still an uphill hike, but the tremendous advances made in the last few decades in terms of both varied biological activity and structural diversity make them a rather promising class of peptidomimetic drug candidates. More information can be found in the Review by Assunta D'Amato.
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![Desymmetrized pillar[8]aren...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1001-8417/small "Desymmetrized pillar[8]arenes: High-yield synthesis, functionalization, and host-guest chemistry")
