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We synthesized a planar macrocyclic dinuclear nickel(II) metallohost from the corresponding macrocyclic imine ligand containing two N2O2 chelate coordination sites and an O6 cation binding site like 18‐crown‐6 as well as peripheral hexyl groups. Due to the lipophilic nature of the hexyl groups, the metallohost was soluble in less polar media where its interaction with alkali metal ions was enhanced. The binding studies by NMR spectroscopy clearly showed its strong tendency to form multi‐layered structures. The metallohost formed 2 : 1 and 1 : 1 (host/guest) complexes with Na+ with the two‐step binding constants of logK1=6.6 and logK2=3.0. In contrast, its complexation with larger alkali metal ions (K+, Rb+, Cs+) preferentially gave 3 : 2 (host/guest) complexes when 2/3 equiv. of the guest was present. The three‐layered structures of these 3 : 2 complexes were well characterized by mass spectrometry and 2D COSY/ROESY experiments as well as DFT calculations, elucidating their unique structural feature with three chemically different environments due to the oppositely curved two [Ni(saloph)] moieties of the metallohost. Therefore, the three‐layered structures were preferentially formed when larger alkali metal ions (K+, Rb+, Cs+) were complexed with the metallohost. [ABSTRACT FROM AUTHOR]

We report the reversible transformation between a singly stapled dynamic α‐helical peptide and a doubly stapled quasi‐static one through redox‐triggered dithiol/disulfide conversions of a stapling moiety. This process allows the rate of interconversion between the right‐handed (P) and left‐handed (M) α‐helices to be altered by a factor of approximately 103 before and after the transformation. An as‐obtained doubly stapled α‐helical peptide, which is composed of an achiral peptide having an l‐valine carboxylic acid residue at the C‐terminus, a disulfide‐based reversible staple, and a biphenyl‐based fixed staple, adopts an (M)‐rich form as a kinetically trapped state. The (M)‐rich helix was subsequently transformed into the thermodynamically stable (P)‐rich form in 1,1,2,2‐tetrachloroethane with the half‐life time (t1/2) of approximately 44 days at 25 °C. Reduction of the doubly stapled peptide with tri‐n‐butylphosphine in tetrahydrofuran/water (10/1, v/v) produced the corresponding singly stapled dynamic α‐helical peptide bearing two thiol groups at the side chains, which underwent solvent‐induced reversible helicity inversion. The resulting dithiol of the singly stapled peptide could be reoxidized to form the original doubly stapled form using 4,4'‐dithiodipyridine. Furthermore, the P/M interconversion of a doubly stapled peptide with two flexible hydrocarbon‐based staples is considerably more rapid than that with more rigid staples. [ABSTRACT FROM AUTHOR]

Dynamic M/P invertible helicity was successfully induced at a SiO2 surface immobilized with a dynamic helical trinuclear cobalt complex, [LCo3(NHMe2)6](OTf)3, using chiral ((R) or (S))-1-phenylethylamine. Solid-state CD spectra and theoretical calculations suggested that the fixation of the M/P helical complex on the surface via coordination interactions was the key factor of the induced chirality at the surface. [ABSTRACT FROM AUTHOR]

Pillar[n]arenes can be constructed using a Friedel–Crafts alkylation process. However, due to the reversible nature of the alkylation, mixture of large pillar[n]arenes (n≥7) are obtained as minor products, and thus laborious purification are necessary to isolate the larger pillar[n]arenes. Moreover, inert methylene bridges are introduced during the alkylation process, and the multi‐functionalization of the bridges has never been investigated. Herein, an irreversible Friedel–Crafts acylation is used to prepare pillar[n]arenes. Due to the irreversible nature of the acylation, the reaction of precursors bearing carboxylic acids and electron‐rich arene rings results in a size‐exclusive formation of pillar[n]arenes, in which the ring‐size is determined by the precursor length. Because of this size‐selective formation, laborious separation of undesired macrocycles is not necessary. Moreover, the bridges of pillar[n]arenes are selectively installed with reactive carbonyl groups using the acylation method, whose positions are determined by the precursor used. The carbonyl bridges can be easily converted into versatile functional groups, leading to various laterally modified pillar[n]arenes, which cannot be accessed by the alkylation strategy. [ABSTRACT FROM AUTHOR]

The article in Chemistry - A European Journal discusses the preferential formation of three-layered host-guest complexes by complexing a macrocyclic dinickel metallohost with larger alkali metal ions (K+, Rb+, Cs+). Spectroscopic and theoretical investigations confirm the unique structure of these complexes, where three metallohost molecules are stacked in a parallel manner with oppositely curved nickel complex moieties. The research was conducted by S. Akine and co-workers, providing further details in the Research Article (DOI: 10.1002/chem.202403071). [Extracted from the article]

A C4h symmetrically substituted phthalocyanine, 1,8,15,22‐tertrakis(2,4‐dimethylpent‐3‐oxy)phthalocyanine (H2TdMPPc), was used to synthesize Tb3+‐phthalocyanine double‐decker complexes ([Tb(TdMPPc)2]s). Because H2TdMPPc has C4h symmetry, S,S, R,R, and meso isomers of [Tb(TdMPPc)2] were obtained depending on the difference in the direction of the coordination plane of two C4h‐type phthalocyanines with respect to a central Tb3+ ion. We investigated the physical properties of these [Tb(TdMPPc)2] isomers, including their single‐ion magnetic properties, and found that the spin‐reversal energy barrier (Ueff) of the meso isomer was apparently higher than that of the enantiomers. Detailed crystal structural analyses indicated that the meso isomer has a more symmetrical structure than do the enantiomers, thereby suggesting that the higher Ueff of the meso isomer originated from the more highly symmetrical structure. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of octanuclear zinc(II) and cobalt(II) clusters that could be obtained by the cooperative tetrameric assembling of the 3-hydroxy-salamo ligand is reported. The structural analysis of the zinc(II) complex in solution has displayed the significant stability of the octanuclear core, suggesting that the tetrameric self-assembly took place highly cooperatively.