A trigonal prismatic coordination cage endowed with a large cavity is built by self-association of a bis(rhodium) complex and a planar triazatruxene-based ligand. The remarkable versatility of this molecular building in promoting reversible structural transformations is demonstrated through manipulating three orthogonal external stimuli, i.e., cage concentration, guest identity, and pH. Four distinct stable discrete structures can be formed on-demand: a monomeric cage, two distinct host-guest complexes, and a mechanically interlocked cage dimer, and all these structures are fully and readily interconvertible. The cage uniquely couples (i) selective double guest encapsulation, (ii) stimulus-controlled reversible catenation, and (iii) pH-triggered pairwise guest release-uptake. The resulting structures were comprehensively characterized using 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, theoretical calculations, and, in most cases, single-crystal X-ray diffraction.

Switching the handedness of circularly polarized luminescence (CPL) at the molecular level remains a challenge in the development of responsive chiral materials. We report a light-driven molecular motor covalently linked to two perylenediimide (PDI) chromophores, enabling reversible and directional modulation of CPL. The different motor states, which are accessible in a unidirectional fashion via light-irradiation and thermal helix inversion steps, respectively, display significantly distinct chiroptical properties. In addition, our system allows switching of the chiral induction process and hence, the observation of a CPL signal. The present work discloses the first example of reversible CPL sign inversion triggered by light irradiation at the single molecular level, offering a new starting point for designing emitters with light-responsive chirality modulation.

ABSTRACT Incorporating redox active ligands into coordination cages offers a direct way to reach architectures whose structure or composition can be modulated in response to changes in the oxidation state. An exTTF‐based ditopic ligand L affords a M 2 L 4 cage in presence of a palladium(II) salt (M). The resulting M 2 L 4 cavity exhibits selective binding properties for medium length α,ω‐dinitrile alkanes. Modifying the coordination geometry of the ligand by oxidation to its L ox state redirects the self‐assembly process toward a M 2 L ox 2 structure. The oxidized ligand can also be combined with a dibenzothiophene linker (L′) to afford a heteroleptic M 2 L ox L′ 2 structure whose vacant coordination sites enable subsequent dimerization into an unprecedented M 4 L 4 L′ 4 architecture. Key intermediates and products were structurally authenticated by single‐crystal x‐ray diffraction. Notably, these processes are reversible. Reduction converts the M 2 L ox L′ 2 assembly back to the homoleptic M 2 L 4 cage. This sequence illustrates how changes of oxidation state can reshape nuclearity and composition in metal organic assemblies.

Due to the reversible nature of the metal-ligand bond, coordination cages are inherently dynamic architectures which can undergo structural transformations upon appropriate external stimulations. This adaptability has been widely explored in various fields. Herein, we report the preparation of a redox-responsive discrete (Ru2)4L2 architecture through a coordination-driven self-assembly approach, where Ru2 is a bis(ruthenium(II)) complex and L a tetrapyridyl ligand. Importantly, ligand L is designed around the π-extended tetrathiafulvalene framework (exTTF), whose geometry is highly sensitive to its redox state. The resulting (Ru2)4L2 assembly was fully characterized, revealing a twisted configuration with two orthogonally oriented L units in close spatial proximity. Remarkably, this assembly undergoes an oxidation-induced transformation into a (Ru2)4Lox₂ structure, in which the two dicationic ligands are now spatially separated and aligned according to a face-to-face arrangement, affording a cage-like structure. This reorganization is driven by the redox-induced geometric and electronic changes of the exTTF cores and the resulting electrostatic repulsions occurring between both oxidized ligands. The process is fully reversible upon chemical reduction, restoring the original (Ru2)4L₂ structure.

Helical foldamers constitute particularly relevant targets in the field of host-guest chemistry, be that as hosts or substrates. In this context, the strategies reported so far to control the dimensions and shape of foldamers mainly involve modifications of the skeleton through covalent synthesis. Herein, we prepared an oligopyridine dicarboxamide foldamer substituted by photo-active tetraphenylethylene units (TPE). We demonstrate that it is possible to toggle the length of a helical foldamer by two means. First, the elongation of foldamers can be tuned by adjusting the concentration, as demonstrated by DOSY NMR spectroscopy and X-ray diffraction analyses on both the single and the double helix structures. Secondly, and in a more original manner, a photo-induced protonation process triggered by TPE units promotes a novel pathway to unfold helical foldamers, leading to dramatic conformational and spectroscopic changes.

Preparing new smart receptors and materials through controlling foldamer assemblies constitutes an appealing strategy. In this context, the use of a redox input appears as a relevant tool to monitor the self-assembly process, provided a careful design of well-chosen electroactive units. Our research group previously showed how the single-to-double helix equilibrium of foldamers can be shifted thanks to redox processes. Aiming at generalizing this strategy and rationalizing our findings, we designed a long oligopyridine dicarboxamide strand bearing tetrathiafulvalene (TTF) units, which are connected on the periphery through short amide linkers. This design proved to have a dramatic impact on the supramolecular behavior of the foldamer, preventing the formation of double helices in the neutral state. Using a combination of electrochemical and spectroscopic measurements, we show that duplex formation can be triggered by oxidizing a foldamer that does not form double helices in the neutral state.

Incorporating chiral elements in host–guest systems currently attracts much attention because of the major impact such structures may have in a wide range of applications, from pharmaceuticals to materials science and beyond. Moreover, the development of multi-responsive and -functional systems is highly desirable since they offer numerous benefits. In this context, we describe herein the construction of a metal-driven self-assembled cage that associates a chiral truxene-based ligand and a bis-ruthenium complex. The maximum separation between both facing chiral units in the assembly is fixed by the intermetallic distance within the lateral bis-ruthenium complex (8.4 Å). The resulting chiral cavity was shown to encapsulate polyaromatic guest molecules, but also to afford a chiral triply interlocked [2]catenane structure. The formation of the latter occurs at high concentration, while its disassembly could be achieved by the addition of a planar achiral molecule. Interestingly the planar achiral molecule exhibits induced circular dichroism signature when trapped within the chiral cavity, thus demonstrating the ability of the cage to induce supramolecular chirogenesis.

Helical foldamers constitute particularly relevant targets in the field of host-guest chemistry, be that as hosts or substrates. In this context, the strategies reported so far to control the dimensions and shape of foldamers mainly involve modifications of the skeleton through covalent synthesis. Herein, we prepared an oligopyridine dicarboxamide foldamer substituted by photo-active tetraphenylethylenes (TPE). We demonstrate that it is possible to toggle the length of a helical foldamer by two means. First, the elongation of foldamers can be tuned by adjusting the concentration, as demonstrated by DOSY NMR spectroscopy and X-ray diffraction analyses on both the single and the double helix structures. Secondly, and in a more original manner, a photo-induced protonation process triggered by TPE units promotes a novel pathway to unfold helical foldamers, leading to dramatic conformational and spectroscopic changes.

Helical foldamers have attracted much attention over the last decades given their resemblance to certain biomacromolecules and their potential in domains as different as pharmaceutics, catalysis and photonics. Various research groups have successfully controlled the right- or left- handedness of these oligomers by introducing stereogenic centers through covalent or non-covalent chemistry. However, developing helical structures whose handedness can be reversibly switched remains a major challenge for chemists. To date, such an achievement has been reported with light-responsive single-stranded foldamers only. Herein, we demonstrate that grafting a unidirectional motor onto foldamer strands constitutes a relevant strategy to i) control the single or double helical state of a foldamer, ii) switch on the chiral induction process from the motor to the helical strands and iii) select the handedness of double helical structures through photochemical and thermal stimulations.

The binding properties of electron-rich M 4 L 2 metallacages with different cavity sizes, constructed through coordination-driven self-assembly of extended tetrathiafulvalene (exTTF)-based ligands, are evaluated and show a high size selectivity for different guest molecules.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Peri-thiaxanthenothiaxanthene, an S-doped analog of peri-xanthenoxanthene, is used as a polycyclic aromatic hydrocarbon (PAH) scaffold to tune the molecular semiconductor properties by editing the oxidation state of the S-atoms. Chemical oxidation of peri-thiaxanthenothiaxanthene with H2 O2 led to the relevant sulfoxide and sulfone congeners, whereas electrooxidation gave access to sulfonium-type derivatives forming crystalline mixed valence (MV) complexes. These complexes depicted peculiar molecular and solid-state arrangements with face-to-face π-π stacking organization. Photophysical studies showed a widening of the optical bandgap upon progressive oxidation of the S-atoms, with the bis-sulfone derivative displaying the largest value (E00 =2.99 eV). While peri-thiaxanthenothiaxanthene showed reversible oxidation properties, the sulfoxide and sulfone derivatives mainly showed reductive events, corroborating their n-type properties. Electric measurements of single crystals of the MV complexes exhibited a semiconducting behavior with a remarkably high conductivity at room temperature (10-1 -10-2  S cm-1 and 10-2 -10-3  S cm-1 for the O and S derivatives, respectively), one of the highest reported so far. Finally, the electroluminescence properties of the complexes were tested in light-emitting electrochemical cells (LECs), obtaining the first S-doped mid-emitting PAH-based LECs.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Pillar[5]arene derivatives decorated with ten peripheral TTF or exTTF subunits were prepared and their electrochemical properties investigated. These electron-rich macrocyclic systems are suitable receptors for a fullerene guest.

Coordination driven self-assembly of achiral components, i.e., hexa-alkylated truxene ligands (L) with bis-metallic complexes (M2), afforded three chiral face-rotating stereoisomer polyhedra (M6L2). By tuning the length of the alkyl chains as well as the distance between both ligands facing each other in the self-assemblies (M6L2), one can control the diastereomeric distribution between the expected homo- and hetero-chiral structures.

Association of C 3 -symmetric pyrene- and naphthalene diimide-based derivatives afforded gels through aromatic interactions. The corresponding (xero)gels displayed original spectroscopic features in comparison to the corresponding one-component materials.