Organometallics and coordination complexes for linear and non linear optics

Keywords : transition metal complexes, dithienylethenes, non linear optics, molecular surfaces

Today, the foreseeable skills limitations of electronic memory devices are about to be reached. The ever-increasing data storage demand has drawn the field of data storage devices and more particularly the development of new types of optical molecular material. To date, the best way to write information at the molecular level with light relies upon the fine controllability of photochromism. In this project the photochromism will regulate the nonlinear optical properties of the molecule (NLO). The combination of photochromism and nonlinear optics gives rise to all-optical molecular systems to write, store and read information with light as the only tool. Conceptually, light is used as sole and unique external vector to write, store, transport and read the information on photoresponsive organized arrays of photochromic metal complexes, grafted onto surfaces. The originality of this approach is settling on accurate combination of photochromism and nonlinear optics (NLO) and allows to get rid of the loss-of-symmetry phenomenon with time while preserving the high NLO contrasts upon photochromism. The methodology relies on the surface-grafting of a chosen azido terminated metal complex to an alkyne pre-functionalized surface by azide-alkyne click-conjugation.

Contact : Julien Boixel

Keywords : dialkynyl Ru and Pt complexes; pyranylidene push-pull chromophores, second order non linear optics (NLO); ICT

Transition-metal complexes with second-order Non-Linear Optical (NLO) properties are important as molecular building block materials for the growing field of molecular photonics. Over the past few years, our research has dealt with synthesizing and studying the properties of asymmetrical push-pull dialkynyl ruthenium- and platinum-based complexes with D–π–M–π–A arrangements.  All complexes incorporate pro-aromatic donor groups (D), such as pyranylidene ligands whose electron-donating ability is based on the formation of an aromatic pyrylium fragment upon an ICT process, and various electron attracting groups (A), such as methyl pyrimidinium, separated by a metal center and π-conjugated linkers.
While we have synthesized asymmetrical Ru(II) and Pt(II) complexes through conventional cross-coupling reactions, we have developed an original one-pot approach for the synthesis of targeted ruthenium-diacetylide complexes.
Second-order Non-Linear Optical (NLO) properties of the synthesized complexes and their entirely organic analogues were determined by the Electric Field-Induced Second Harmonic (EFISH) generation method. All compounds (organic and organometallic) exhibited positive µβ values, which dramatically increased upon methylation of the pyrimidine acceptor fragment.  With the same donor-acceptor combination, the strongest NLO response was obtained with the ruthenium complexes placing them among the more efficient NLO alkynyl metal complexes reported so far.

Contacts : Sébastien Gauthier, Sylvain Achelle, Raphaël Durand, Françoise Robin-Le Guen

Keywords : coordination complexes, pi-conjugated systems, two-photon photo-absorbers, advanced materials

We are interested in the study of RuLn(bpy)3-n heteroleptic complexes with a large effective cross-section (biphotonic absorption) and carrying a complementary function. We wish to extend their potential to fileds where the use of efficient multiphotonic absorbers is critical (photo-induced polymerization, phototherapy, sensing...) and by their integration in multifunctional materials.
This work focus in particular on the engineering of two-photon photo-initiator complexes for the design of nanostructured molecular materials will be pursued along two lines:
- for interface (solide/liquid or gaz) detection (coll. J-P Malval [IS2M, Mulhouse], F. Gauffre, [ISCR], R. Marsac [GeoSciences Rennes]).
- for the development of new polymeric devices for detection, based on electrochemiluminescence of ruthenium complexes (coll. J-P Malval [IS2M, Mulhouse], N. Sojic [ENSCPB Bordeaux]).

Contact : Jean-Luc Fillaut

Keywords: transition metals; Schiff bases; donor-acceptor; nonlinear optics.

The Schiff base family constitutes a major class of ligands in inorganic chemistry. Their formidable success relies on their high affinity for a great number of metal ions in various oxidation states to form a wide range of stable complexes, and their modular synthesis, which allows for a convenient tuning of both the electronics of the ligand and the steric hindrance around the metal. They found numerous applications in both chemical and biological processes. In the field of functional molecular materials, complexes of assymmetric Schiff bases that are dipolar molecules bearing electron donor and acceptor groups connected through a π-conjugated spacer, have proven to be efficient chromophores exhibiting large second-order nonlinear optical (NLO) responses controlled by low-energy metal-to-ligand charge transfer (MLCT) excitations. On the other hand, they show excellent catalytic activities in various reactions at high temperatures and in the presence of moisture. Our interest has been centered in the design and construction of novel transition metal complexes supported by N2O2-tetradentate unsymmetrically-substituted Schiff base ligands (CCR 2018, 357,  144; NJC 2020, 40, 9190) exhibiting redox-switchable opto-electronic properties (NJC 2019, 43, 10468). Enhancement of the NLO properties was achieved on progressing from small molecules to main-chain oligomers and side-chain metallopolymers. Those complexes are also efficient and reusable precatalyst for the CuAAC (click) reactions (NJC 2016, 40, 3308) and ROP of rac-lactides (polyhedron 2019, 162, 91). This research work is performed as part of the Chilean-French International Research program “Multifunctional Molecules and Materials” (IRP M3-CNRS No. 1207).

Contact : Jean-René Hamon.