Solution‐Stable Triple Helicates of Quaterimidazole: Three‐Dimensional Crystal Structures and Optical Resolution by Chiral‐Column HPLC

Abstract

Complex formation of quaterimidazole with FeII, CoII, and NiII yielded dinuclear triple helicates in the solution state by the self‐assembling ability of the ligand based on the strong chelating coordination bonds. Crystallization of the CoII complex from aqueous solution afforded the CoIII complex with a triple‐helical structure. X‐ray crystal structure analyses revealed that the helicates are linked through N–H···X hydrogen bonds with counteranions and solvent molecules to form three‐dimensional networks. The spectrophotometric titration experiment showed that quaterimidazole forms triple helicates with various d‐block transition metal ions with high selectivity. The outward intermolecular interactions and high stability of the helicates from the rigid molecular structures combined with the intramolecular π–π interactions of imidazole moieties and their strong chelating coordination enabled the successful optical resolution of right‐ and left‐handed helicates by chiral‐column HPLC.

High-Fidelity Stereochemical Memory in a FeII4L4 Tetrahedral Capsule

“…A general strategy to influence the stereochemistry of self-assembled systems and capsules − ,, is the introduction of additional stereocenters, in the form of either enantiopure building blocks, ,,,− chiral ancillary ligands, ,, chiral guests, , or counterions. , The fixed stereochemistry of these stereocenters thus influences the conformations of new stereocenters formed during self-assembly resulting in diastereomerically enriched structures. The isolation of enantiomerically pure assemblies has been achieved through self-resolution or chiral chromatography of assemblies originally prepared in racemic form, , as pioneered in the context of Ga 4 L 6 clusters by the Raymond group . Systems with stereochemical memory ,,− are able to process and conserve the information first introduced by a chiral auxiliary after its removal or replacementthe crucial step of this strategy.…”

Stereochemical Communication within Tetrahedral Capsules

“…76,77 In contrast, the chiral memory concept®first reported by Aida 78 and Yashima 79 and applied to porphyrin aggregates and helical polymers, respectively®has allowed for the enantioselective synthesis of several self-assembled structures.…”

Tetrathiafulvalene‐Type Electron Donors Bearing Biimidazole Moieties: Multifunctional Units with Hydrogen Bonding Abilities

“…The structural features of 4,4′‐Bim has resulted in the construction of diverse and multidimensional H‐bonding networks in transition‐metal complexes17 and CT salts with TCNQ 18. Furthermore, our intensive studies on the self‐assembly of oligo(imidazole)s revealed that their rigid molecular structures and robust chelating coordination bonds formed triple helicates with various d‐block transition‐metal ions exhibiting high selectivity and inertness 19c,19d. These features of oligo(imidazole)–helicates allowed the design of the first electron‐spin‐based Lloyd model for scalable matter spin‐qubit 19c,20…”