Coal-Tar Dye-based Coordination Cages and Helicates.

Irene Regeni,Julian J Holstein,Guido H Clever,Bin Chen,Marina Frank,Ananya Baksi

doi:10.1002/anie.202015246

Irene Regeni, Julian J Holstein + Show 4 more

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https://doi.org/10.1002/anie.202015246

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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.

Highlights

A strategy to implement four members of the classic coal-tar dye family, Michlers ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self-assemblies is introduced
With respect to discrete coordination cages with an accessible cavity,[8] radical reactions have been realized in hosts where sidewalls can be brought to excited states by irradiation with light.[9]
In full accordance with our previously reported PdII-based cages,[28] coordination of ligands to the metal centers was indicated by downfield shifting of the pyridine 1H NMR signals (in particular Ha and Hb, SI and Figure 2 a for [Pd2(RB-P)4]). 1H DOSY NMR and high-resolution ESI mass spectrometry further support the formation of the desired products

Summary

Introduction

A strategy to implement four members of the classic coal-tar dye family, Michlers ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self-assemblies is introduced. In full accordance with our previously reported PdII-based cages,[28] coordination of ligands to the metal centers was indicated by downfield shifting of the pyridine 1H NMR signals (in particular Ha and Hb, SI and Figure 2 a for [Pd2(RB-P)4]). Two choices of donor groups (3-pyridyl P and 8-isoquinolinyl Q) were examined, giving rise to eight (plus one derivative) ligands that were all found to form intensely colored PdII-mediated cages or helicates (ligand names are composed of backbone and donor label; see Figure S1 in the SI for all ligand structures).

Results

Conclusion