Synthèse et caractérisation de complexes hétéroleptiques de cuivre(I) pour la conversion de l'énergie solaire

This thesis describes the synthesis and characterization of new heteroleptic copper(I) complexes with diimine and diphosphine ligands for solar energy conversion. The complexes were synthesized with the HETPHEN approach, and were fully characterized by physicochemical and photophysical techniques.At first, a study of the properties of heteroleptic structures was carried out, considering in particular the effect of the steric hindrance of the coordination sphere. Two new ligands containing an extended phenanthroline core, and bromo groups, are then described together with the corresponding complexes. The improvement of the visible absorption properties was achieved with chromophoric push-pull styrylbipyridine ligands. This strategy allowed to obtain a series of complexes with impressively high absorption coefficients.In chapter 4, the use of heteroleptic copper(I) diimine complexes to build rod-like molecular arrays for photoinduced electron transfer was developed. Two Cu-NDI (naphthalene diimide) dyads were synthesized and characterized. Transient absorption spectroscopy evidenced photoinduced electron transfers. A secondary electron donor (ferrocene) was then included, to provide a triad with an increased charge-separated state lifetime of 30 ns in acetonitrile. The last chapter focuses on the design of complexes containing an anchoring function, for the use as sensitizers in dye-sensitized solar cells (DSSCs). Two series of dyes were prepared, one of them showing very promising photovoltaic performances (2.4% under 1000 W/m2).Cette thèse décrit la synthèse et la caractérisation de complexes hétéroleptiques de cuivre(I) avec des ligands diimine et diphosphine pour la conversion de l’énergie solaire. Les molécules ont été synthétisées en utilisant l’approche HETPHEN, et ont fait l’objet de caractérisations physicochimiques et photophysiques.En premier lieu, la synthèse et l’étude de nouveaux complexes de cuivre hétéroleptiques ont été menées en considérant en particulier l’effet de l’encombrement stérique de la sphère de coordination. Deux ligands originaux contenant un noyau phénanthroline étendu, et des fonctions réactives bromo, sont ensuite décrits ainsi que les complexes correspondants. Une augmentation des coefficients d’absorption dans le visible a été obtenue grâce à l’utilisation de ligands push-pull¬ de type styrylbipyridine.Dans le chapitre 4, l’utilisation des complexes hétéroleptiques de cuivre(I) diimine pour le transfert de charge photoinduit dans des assemblés linéaires a été développée. Deux dyades Cu-NBI (naphthalène bisimide) ont été synthétisées et caractérisées. La spectroscopie d’absorption transitoire a mis en évidence des transferts d’électron photoinduits. Un donneur d’électrons secondaire (ferrocène) a ensuite été rajouté, pour former une triade qui conduit à un temps de vie de l’état à charges séparées de 30 ns dans l’acétonitrile. Le dernier chapitre porte sur la conception de sensibilisateurs dans des cellules solaires à colorant (DSSCs). Deux séries de complexes de cuivre(I) ont été préparées et caractérisées. L’une des deux a montré des performances photovoltaïques très prometteuses (2,4% sous 1000 W/m2)

Enhanced electrochemiluminescence from a stoichiometric ruthenium(II)-iridium(III) complex soft salt

The authors thank NSERC, CFI, FQRNT, PREA, and The University of Western Ontario for generous financial support to this research.Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)3][Ir(ppy)2(CN)2]2 ([Ir][Ru][Ir]), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]2+ and [Ir]− moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)3]2+, ECL in the co-reactant path with tri-n-propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]2+* excited state and no [Ir]−* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low-energy-cost ECL detection systems.PostprintPeer reviewe

Heteroleptic bis-diimine copper(I) complexes for applications in solar energy conversion

AbstractThe development of molecular materials for conversion of solar energy into electricity and fuels is one of the most active research areas, in which the light absorber plays a key role. In this article, we present a class of photo-sensitizers constituted by heteroleptic bis-diimine copper(I) complexes, whose features rely on their tunable MLCT excited states and earth abundant and environmentally friendly nature of copper. These properties make this class of dyes compatible with a sustainable development. Their synthesis through the HETPHEN strategy and the background of their photophysical properties as well as the recent advances in the fields of both dye-sensitized solar cells and photoinduced charge separation are presented. The presented examples prove that bis-diimine copper(I) complexes are valuable dyes to be used to build multicomponent arrays for long range electron transfer and for dye-sensitized solar cells. These examples illustrate that one major advantage of heteroleptic complexes is the possibility to finely tune their opto-electronic properties to a larger extent than homoleptic complexes

Heteroleptic diimine copper(i) complexes with large extinction coefficients: synthesis, quantum chemistry calculations and physico-chemical properties.

International audience: Using the HETPHEN approach, five new heteroleptic copper(i) complexes composed of a push-pull 4,4'-styryl-6,6'-dimethyl-2,2'-bipyridine ligand and a bulky bis[(2-diphenylphosphino)phenyl]-ether (DPEphos) or a bis2,9-mesityl phenanthroline (Mes2Phen) were prepared and characterized by electronic absorption spectroscopy, electrochemistry, and TD-DFT calculations. These complexes exhibit very intense absorption bands in the visible region with extinction coefficient in the range of 5-7 × 10(4) M(-1) cm(-1). The analysis of the position, intensity and band shape indicates a strong contribution from an intra-ligand charge-transfer transition centered on the styrylbipyridine ligand along with MLCT transitions. These new complexes experimentally demonstrate that good light harvesting properties with bis-diimine copper(i) complexes are a reality if one chooses suitable ligands in the coordination sphere. This constitutes a milestone towards using bis-diimine copper(i) complexes for solar energy conversion (artificial photosynthesis and solar cells)

Exploring energy transfer in luminescent heterometallic ruthenium–iridium ion pairs

Here, we report the synthesis of a luminescent ion pair with the formula [Ru(dtBubpy)3][Ir(ppy)2(CN)2]2. The crystal structure of this three component, heterometallic assembly is described, along with the luminescence properties of the salt. The modulation of the energy transfer between the blue-emitting iridium complex and the red-emitting ruthenium complex is also discussed as a function of both medium and concentration.PostprintPeer reviewe

Fluorine-free blue-green emitters for light-emitting electrochemical cells

Date of Acceptance: 29/05/2014There is presently a lack of efficient and stable blue emitters for light-emitting electrochemical cells (LEECs), which limits the development of white light emitting systems for lighting. Cyclometalated iridium complexes as blue emitters tend to show low photoluminescence efficiency due to significant ligand-centred character of the radiative transition. The most common strategy to blue-shift the emission is to use fluorine substituents on the cyclometalating ligand, such as 2,4-difluorophenylpyridine, dFppy, which has been shown to decrease the stability of the emitter in operating devices. Herein we report a series of four new charged cyclometalated iridium complexes using methoxy- and methyl-substituted 2,3′-bipyridine as the main ligands. The combination of donor groups and the use of a cyclometalated pyridine has been recently reported for neutral complexes and found electronically equivalent to dFppy. We describe the photophysical and electrochemical properties of the complexes in solution and use DFT and TDDFT calculations to gain insights into their properties. The complexes exhibit bluish-green emission with onsets around 450 nm, which correspond to the maximum emission at 77 K. Furthermore, photoluminescence quantum yields in solution are all above 40%, with the brightest in the series at 66%. Finally, LEECs were prepared using these complexes as the emissive material to evaluate the performance of this particular design. Compared to previously reported devices with fluorine-containing emitters, the emitted colours are slightly red-shifted due to methyl substituents on the coordinating pyridine of the main ligand and overall device performances, unfortunately including the stability of devices, are similar to those previously reported. Interestingly within the series of complexes there appears to be a positive effect of the methoxy-substituents on the stability of the devices. The poor stability is therefore attributed to the combination of cyclometalated pyridine and methoxy groups.PostprintPeer reviewe