Coal‐Tar Dye‐based Coordination Cages and Helicates

• Published in: Angewandte Chemie International Edition Vol. 60; no. 11; pp. 5673 - 5678
• Main Authors: Regeni, Irene, Chen, Bin, Frank, Marina, Baksi, Ananya, Holstein, Julian J., Clever, Guido H.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 08-03-2021; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Assemblies; Cages; Catalysis; chirality transfer; Chromophores; Communication; Communications; Coordination; coordination cages; Crystal structure; Dyes; Ionic mobility; Ligands; Mass spectrometry; Mass spectroscopy; Methylene blue; Optical materials; Palladium; Piperazine; Pyridines; Quinoline; Rhodamine; Ring structures; self-assembly; Single crystals; supramolecular chemistry; Visible spectrum; self-assembly; dyes; coordination cages; supramolecular chemistry; chirality transfer
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202015246

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.
A family of classic organic dyes, known since the advent of modern chemistry, was integrated into 3‐dimensional, self‐assembled nano‐objects via a novel piperazine‐based linker strategy that conserves the auxochromic substituents. The dynamic nature of the lantern‐shaped cages and helicates allows to recognize enantiopure guests via chirality transfer to the host, detected by circular dichroism response far in the visible region.