Homochiral Double Helicates Based on Cyclooctatetrathiophene: Chiral Self-Sorting with the Intramolecular S⋅⋅⋅N Interaction

Adjusting the balance between hydrogen and chalcogen bonds

A complex is assembled which pairs a carboxyl group of X₁COOH with a 1,2,5-chalcogenadiazole ring containing substituents on its C atoms. The OH of the carboxyl group donates a proton to a N atom of the ring to form a OH⋯N H-bond (HB), while its carbonyl O engages in a Y⋯O chalcogen bond (ChB) with the ring in which Y = S, Se, Te. The ChB is strengthened by enlarging the size of the Y atom from S to Se to Te. Placement of an electron-withdrawing group (EWG) X₁ on the acid strengthens the HB while weakening the ChB; the reverse occurs when EWGs are placed on the ring. By selection of the proper substituents on the two units, it is possible to achieve a near perfect balance between the strengths of these two bonds. These bond strengths are also reflected in the NMR spectroscopic properties of the chemical shielding of the various atoms and the coupling between the nuclei directly involved in each bond.

Self-sorting assembly of artificial building blocks

Self-assembly to build high-level structures, which is ubiquitous in living systems, has captured the imagination of scientists, striving to emulate the intricacy, homogeneity and versatility of the naturally occurring systems, and to pursue a similar level of organization in artificial building blocks. In particular, self-sorting assembly in multicomponent systems, based on the spontaneous recognition and consequent spatial aggregation of the same or interactive building units, is able to realize very complicated assembly behaviours, and usually results in multiple well-ordered products or hierarchical structures in a one-step manner. This highly efficient assembly strategy has attracted tremendous research attention in recent years, and numerous examples have been reported in artificial systems, particularly with supramolecular and polymeric building blocks. In the current review, we summarize the progress in recent years, and classify them into five main categories, based on their working mechanisms or principles. With the review of these strategies, we hope to provide not only some deep insights into this field, but also and more importantly, useful thoughts in the design and fabrication of self-sorting systems in the future.

Organic microporous crystals driven by pure C-H⋯π interactions with vapor-induced crystal-to-crystal transformations

Organic porous crystals constructed by only a single kind of weak molecular interaction are invaluable to understanding the nature of the formation of organic porous materials and developing new types of porous materials. Here, we designed and synthesized two pure organic compounds of PBO and PBS through integrating planar dibenzothiophene/dibenzofuran and two phenothiazine groups together with twisted C-N bonds, which form organic microporous crystals with very good stability against strong acids and bases VIA pure C-H⋯π interactions. Accordingly, the effective absorption of toluene has been successfully realized with an adsorbing capacity of 6.20 mmol g^-1, regardless of the interference of water vapor. Excitingly, these microporous materials exhibit interesting crystal-to-crystal transformation (CCT) properties accompanied by changed pore size on being exposed to different organic vapors. Therefore, the desorption process of toluene could be completed through a simple exposure to dichloromethane (DCM) vapor and the second transformation of the crystal occurred in this process.

Experimental and theoretical insights into the trans influence of organo-sulfur and -selenium ligands in 5,6-membered palladium(ii) cationic pincer complexes based on iminophosphoranes

The trans influence of organochalcogen ancillary ligands was assessed by experimental and DFT studies in 5,6-membered SNS and SNSe Pd(ii) pincers.

Sorting Phenomena and Chirality Transfer in Fluoride-Bridged Macrocyclic Rare Earth Complexes

The reaction of fluoride anions with mononuclear lanthanide(III) and yttrium(III) hexaaza-macrocyclic complexes results in the formation of dinuclear fluoride-bridged complexes. As indicated by X-ray crystal structures, in these complexes two metal ions bound by the macrocycles are linked by two or three bridging fluoride anions, depending on the type of the macrocycle. In the case of the chiral hexaaza-macrocycle L1 derived from trans-1,2-diaminocyclohexane, the formation of these μ2-fluorido dinuclear complexes is accompanied by enantiomeric self-recognition of macrocyclic units. In contrast, this kind of recognition is not observed in the case of complexes of the chiral macrocycle L2 derived from 1,2-diphenylethylenediamine. The reaction of fluoride with a mixture of mononuclear complexes of L1 and L2, containing two different Ln(III) ions, results in narcissistic sorting of macrocyclic units. Conversely, a similar reaction involving mononuclear complexes of L1 and complexes of achiral macrocycle L3 based on ethylenediamine results in sociable sorting of macrocyclic units and preferable formation of heterodinuclear complexes. In addition, formation of these heterodinuclear complexes is accompanied by chirality transfer from the chiral macrocycle L1 to the achiral macrocycle L3 as indicated by CPL and CD spectra.

Ag-Induced metallogel based on cyclooctatetrathiophene: structural characterization and stimuli-responsive properties

Based on saddle-shaped cyclooctathiophene (COTh) as a building block, ligands 2 and 3 were synthesized bearing 3- or 4-substituted pyridyl groups as coordination groups, which showed strong gelation abilities with AgBF4 in several solvents at room temperature. This Ag+-induced metallogel exhibited outstanding stimuli-responsive properties upon addition of halogen ions, acetonitrile or H2O.

The Chirality Induction and Modulation of Polymers by Circularly Polarized Light

Chirality is a natural attribute nature of living matter and plays an important role in maintaining the metabolism, evolution and functional activities of living organisms. Asymmetric conformation represents the chiral structure of biomacromolecules in living organisms on earth, such as the L-amino acids of proteins and enzymes, and the D-sugars of DNA or RNA, which exist preferentially as one enantiomer. Circularly polarized light (CPL), observed in the formation regions of the Orion constellation, has long been proposed as one of the origins of single chirality. Herein, the CPL triggered asymmetric polymerization, photo-modulation of chirality based on polymers are described. The mechanisms between CPL and polymers (including polydiacetylene, azobenzene polymers, chiral coordination polymers, and polyfluorene) are described in detail. This minireview provides a promising flexible asymmetric synthesis method for the fabrication of chiral polymer via CPL irradiation, with the hope of obtaining a better understanding of the origin of homochirality on earth.