Coal‐Tar Dye‐based Coordination Cages and Helicates

Abstract

A strategy to implement four members of the classic coal‐tar dye family, Michler's ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self‐assemblies is introduced. Chromophores were incorporated into bis‐monodentate ligands using piperazine linkers that allow to retain the auxochromic dialkyl amine functionalities required for intense colors deep in the visible spectrum. Upon palladium coordination, ligands with pyridine donors form lantern‐shaped dinuclear cages while quinoline donors lead to strongly twisted [Pd2L4] helicates in solution. In one case, single crystal X‐ray diffraction revealed rearrangement to a [Pd3L6] ring structure in the solid state. For nine examined derivatives, showing colors from yellow to deep violet, CD spectroscopy discloses different degrees of chiral induction by an enantiomerically pure guest. Ion mobility mass spectrometry allows to distinguish two binding modes. Self‐assemblies based on this new ligand class promise application in chiroptical recognition, photo‐redox catalysis and optical materials.

Increasing structural and functional complexity in self-assembled coordination cages

“…18). 117 Key structural element is further the implementation of piperazine linkers between the chromophores and coordinating donors as crucial requirement to retain the dyes' properties by serving as auxochromic groups (as they mimic the typical dimethyl amine substituents of many coal tar dyes, serving to reduce the HOMO-LUMO gap in the extended push-pull electronic system). helicates that rapidly convert between two enantiomeric conformers (Fig.…”

Fine‐Tuning of Chiral Microenvironments within Triple‐Stranded Helicates for Enhanced Enantioselectivity

“…[9] Helicates or metallohelices,p ioneered by Lehn, [10] are discrete coordination complexes in which one or more organic ligands helically wrapped and coordinated to cations (or anions) by coordination bonds. [11] Ty pically,t he assembly of pre-designed ligands and metal ions can form various helicates with structurally well-defined shapes and sizes, including double-stranded, [12] triple-stranded, [13] quadruplestranded, [14] six-stranded, [15] and circular helicates. [16] For example,N itschke and co-workers recently reported the assembly of six-stranded hollow helicates [Ag I 8 L 6 ]a nd [Ag I 12 L 6 ], where the templating anion plays an integral structure-defining role.…”

Hierarchical Two‐Level Supramolecular Chirality of an Achiral Anthracene‐Based Tetracationic Nanotube in Water

“…[3] Inspired by this, conformationally adaptive hosts including macrocycles and cages that possess the ability to undergo a conformational response during host-guest complexation have been developed for chiral recognition and stimuli-responsive systems. [4,5] Recently, the adaptive chirality of an achiral host that undergoes a rotational conformational transformation has been defined and used for the chiral recognition of amino acids, deoxynucleotides, peptides, proteins, and DNA in water. [6] This achiral host exhibited circular dichroism (CD) and/or circularly polarized luminescence (CPL) upon binding.…”