Issue 42, 2018

Structure-switching M3L2 Ir(iii) coordination cages with photo-isomerising azo-aromatic linkers


Cyclotriguaiacylene has been functionalised with 3- or 4-pyridyl-azo-phenyl groups to form a series of molecular hosts with three azobenzene-type groups that exhibit reversible photo-isomerisation. Reaction of the host molecules with [Ir(C^N)2(NCMe)2]+ where C^N is the cyclometallating 2-phenylpyridinato, 2-(4-methylphenyl)pyridinato or 2-(4,5,6-trifluorophenyl)pyridinato results in the self-assembly of a family of five different [{Ir(C^N)2}3(L)2]3+ coordination cages. Photo-irradiation of each of the cages with a high energy laser results in EZ photo-isomerisation of the pyridyl-azo-phenyl groups with up to 40% of groups isomerising. Isomerisation can be reversed by exposure to blue light. Thus, the cages show reversible structure-switching while maintaining their compositional integrity. This represents the largest photo-induced structural change yet reported for a structurally-integral component of a coordination cage. Energy minimised molecular models indicate a switched cage has a smaller internal space than the initial all-E isomer. The [Ir(C^N)2(NCMe)2]+ cages are weakly emissive, each with a deep blue luminescence at ca. 450 nm.

Graphical abstract: Structure-switching M3L2 Ir(iii) coordination cages with photo-isomerising azo-aromatic linkers

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Article information

Article type
Edge Article
06 Aug 2018
29 Aug 2018
First published
06 Sep 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 8150-8159

Structure-switching M3L2 Ir(III) coordination cages with photo-isomerising azo-aromatic linkers

S. Oldknow, D. R. Martir, V. E. Pritchard, M. A. Blitz, Colin W. G. Fishwick, E. Zysman-Colman and M. J. Hardie, Chem. Sci., 2018, 9, 8150 DOI: 10.1039/C8SC03499K

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