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Photoluminescent hybrid polyoxometalates

Hélène Serier-Brault (Associate Professor), Rémi Dessapt (Associate Professor)

We design new photoluminescent hybrid organic-inorganic materials in which POMs are used as efficient redox and optically active co-factors to tune the energy or the emission intensity of exogenous organic molecules in the solid state.

1. POM/cyclometalated iridium (III) complex hybrid systems

We have recently designed a new class of photoluminescent hybrid systems by combining for the first time cationic cyclometalated iridium (III) complexes and POMs. Using a straightforward one-step synthetic procedure, the solid-state phosphorescence of the archetypal [IrIII(ppy)2(bpy)]+ complex, which is a well-known orange emitter, has been successfully tuned from green to yellow, orange and red by its association with a series of polyoxometalates (Figure 1a). Such a strong emission color modulation requires no ligand functionalization of the pristine iridium(III) complex because both the nature of the POM used and the design of the framework govern the relative contributions of the 3CT and 3LC emitting states in the phosphorescence process of the iridium(III) complex.

Such new materials can also exhibit remarkable vapoluminescence properties under ambient conditions via a new polymorphous conversion mechanism. (Figure 1b). They can be used as efficient chemosensors for detection of volatile organic compounds (VOCs) in the environment or workplace, even in the presence of moisture.




Figure 1. (a) Top: Schematic assemblies of [Ir]+ and POM units in [Ir]2(TBA)2[b-Mo8O26]-A (Ir2Mo8-A), [Ir]2(TBA)2[b-Mo8O26]-B (Ir2Mo8-B), [Ir]4[a-Mo8O26] (Ir4Mo8), [Ir]2[Mo4O10(OCH3)6]∙2CH3OH (Ir2Mo4), and [Ir]2[W6O19] (Ir2W6), and photographs of their solid-state emission colors at 298 K compared with that of [Ir](PF6) (lex = 365 nm). (blue octahedra = MoO6 and WO6; orange sphere: oxygen; black sphere: carbon). Bottom: Room temperature steady-state photoluminescence spectra and colorimetric coordinates (insert) of Ir2Mo8-A (l), Ir2Mo8-B (►), Ir4Mo8 (Ù), Ir2Mo4 (¿), Ir2W6 (ì), and [Ir](PF6) (*). (b) Room temperature solid-state luminescence spectra (ex = 365 nm) of Ir2Mo8-A (red solid line), Ir2Mo8-A exposed to acetonitrile vapor for 48h (black solid line), Ir2Mo8-B (blue solid line), and Ir2Mo8-A exposed to acetonitrile vapor for 48h, and then heated at 120°C for 4h (green dashed line). Insert: Photographs of the reversible solid-state vapoluminescence of Ir2Mo8-A upon exposure to acetonitrile vapor and after heating.


Drastic solid-state luminescence color tuning of an archetypal Ir(III) complex using polyoxometalates and its application as a vapoluminescence chemosensor
P. Bolle, H. Serier-Brault, R. Génois, E. Faulques, A. Boulmier, O. Oms, M. Lepeltier, J. Marrot, A. Dolbecq, P. Mialane, R. Dessapt, J. Mater. Chem. C 4, 11392 (2016)

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