Luminescent properties of coordination assemblies for optoelectronic applications.

I-Coordination chains and polymers with organometallic linkers 

Our group has recently designed a new family of organometallic o– and p-quinonoïd complexes of iridium and rhodium. These compounds were used as organometallic-linkers “OM-linkers” to construct a novel class of luminescent coordination assemblies and polymers. Interestingly the chalcogen atoms of the p-quinonoïd complexes (Figure) are highly nucleophilic and hence are able to bind a wide range of transition metal based chromophores such as Cu(I), Ag (I), Ru(II), Pt(II), Rh(III) and Ir(III). Moreover the related o- and p-thioquinonoid OM-linkers (E= S,) were prepared for the first time following an appropriate synthetic procedure. These highly reactive intermediates were metal-stabilized and isolated as “Cp*Ir” complexes.

Figure: Organometallic o- and p-quinonoïd Complexes ACIE 200847, 1372.

The dithiobenzoquinone complexes (E=S) are of particular interest since they allowed the preparation of a new family of polypyridyl platinum(II) compounds exhibiting important π–π and Pt(II)•••Pt(II) interactions responsible of thermochromism and photoluminescence properties (Collaboration Prof V. W. W. Yam). These compounds are potentially of great interest as luminescent material devices.

Figure. Photoluminescence and Thermochromism behavior of 1D Pt-chain with p-thioquinonoid OM-linker Dalton Trans. 2007, 3526. Organometallics201332, 4985. Orgnometallics, 2017, 36, 4794.

More recently we were able to isolate the first example of a diselenobenzoquinone (E= Se) as a metal complex. The X-ray molecular structure of this molecule was determined. Furthermore this species exhibited important antitumoral properties comparable to that of cis-platin. This work was heralded the cover of the prestigious journal Angewandte Chemie.

Figure. Molecular structure of the  p-diselenobenzoquinone as a metal complex: ACIE201049, 7530. (very important paper). Highlighted by Chemistry World September 2010. Highlighted by  Angewandte Chemie 201049, 8304.  Highlighted on CNRS website Octobre 2010.

II. Discrete square planar and octahedral assemblies with organometallic linkers

Another interesting class of luminescent assemblies are the octahedral Ir(III), Rh(III) and Ru(II) and the square planar platinum complexes containing the o-quinonoid and o-thioquinonoid organometallic linkers. The resulting bimetallic assemblies act as panchromatic absorbers and display interesting photoluminescence properties from blue to red emitters and such in some cases NIR emissions were observed. These complexes hold promise for applications in the area of optoelectronics.

Figure. Luminescent bimetallic assemblies with o-quinonoid OM-linker. Organometallics2009, 28, 397. Inorg. Chem. 201049, 10762. Chem. Comm201349, 3796. Inorg. Chem201756, 2050. Inorg. Chem. 2022, 61, 4909.

III- Phosphorescent Iridium(III) complexes with chromophoric N-heterocyclic carbene (NHC) ligands.

The current work describes the preparation of deep red phosphorescent octahedral iridium cyclometalated complexes. These compounds feature N-heterocyclic carbene attached to a naphthalimide chromophore. The introduction of this organic chromophore onto the carbene moiety changes the character of the lowest excited state from  3MLCT to 3LC. All complexes display a naphthalimide-based deep red phosphorescence emission above 630 nm with good quantum yields (φ ≈ 0,2) and long lifetimes.

Figure.Octahedral iridium cyclometalated complexes containing chromophoric-NHC ligands. 
Eur J. Inorg. Chem. 2016, 1631. Inorganics, 2017, 5, 85. Dalton Trans, 2018, 47, 3440. Chem. Rev. 2023, 123, 230.

IV- Luminescent pyridylidene and phosphinine platinum(II) complexes

We are interested in the design of unusual late transition metal complexes with phosphinine and carbene ligands. We have recently reported the first luminescent metal complex with phosphinine ligands, we have shown that a long-lived emission arises from a phosphinine-localised triplet excited state. Phosphinines are among the most -acidic ligands and thus could provide interesting red and near-infrared emitting materials due to a very low LUMO localized on the phosphabenzene ring.

Figure. (a) The first luminescent platinum(II) complex bearing phosphinine co-ligands with a long-lived emission from a phosphinine-localised triplet excited state : (a) Dalton Trans., 201443, 8162; (b) Eur. J. Inorg. Chem. 2016, 761.

We are also interested in the preparation of luminescent late transition metal complexes of unusual carbene ligands. We have for instance reported two unprecedented pincer-like palladium(II) and platinum(II) complexes with a rare bis-chelating tridentate pyridyl-carbene-pyridyl N^C^N ligand exhibiting a six membered NHC central core. The solid-state molecular structures of the complexes showed formation of 1D supramolecular chains displaying short metallophilic M(II)•••M(II) et π-π.

Figure. Luminescence spectra of 2b in the solid state at 298 K (green line) and of 2band 2a in butyronitrile glass at 77 K (red and blue lines respectively).. Dalton Trans.201645, 12644.