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Funder: Samsung Display Corp., Carbene-metal-amides (CMAs) are an emerging class of photoemitters based on a linear donor-linker-acceptor arrangement. They exhibit high flexibility about the carbene-metal and metal-amide bonds, leading to a conformational freedom which has a strong influence on their photophysical properties. Herein we report CMA complexes with (1) nearly coplanar, (2) twisted, (3) tilted, and (4) tilt-twisted orientations between donor and acceptor ligands and illustrate the influence of preferred ground-state conformations on both the luminescence quantum yields and excited-state lifetimes. The performance is found to be optimum for structures with partially twisted and/or tilted conformations, resulting in radiative rates exceeding 1 × 106 s-1. Although the metal atoms make only small contributions to HOMOs and LUMOs, they provide sufficient spin-orbit coupling between the low-lying excited states to reduce the excited-state lifetimes down to 500 ns. At the same time, high photoluminescence quantum yields are maintained for a strongly tilted emitter in a host matrix. Proof-of-concept organic light-emitting diodes (OLEDs) based on these new emitter designs were fabricated, with a maximum external quantum efficiency (EQE) of 19.1% with low device roll-off efficiency. Transient electroluminescence studies indicate that molecular design concepts for new CMA emitters can be successfully translated into the OLED device.

Funder: Academy of Finland : Flagship Programme “Photonics Research and Innovation”; Grant(s): 320166, Funder: Osk. Huttunen Foundation; Id: http://dx.doi.org/10.13039/501100013507, A series of gold‐centered carbene‐metal‐amide (CMA) complexes are synthesized with the carbazole donor ligand modified by substitution with nitrogen atoms in varying positions. The luminescence of new aza‐CMA complexes shows a significant blueshift depending on the position of the N atom, to provide bright blue‐green (500 nm), sky‐blue (478 nm), blue (450 nm) and deep‐blue (419 nm) light‐emitters. The impact of the electron‐withdrawing aza‐group on the nature of the luminescence and the excited state energies of the locally excited (LE) or charge transfer (CT) states have been interpreted with the help of transient absorption, in‐depth photoluminescence experiments and theoretical calculations. By considering the orbital characters of the lowest CT and LE states, we develop a new concept for simultaneous energy tuning for both of these states with a single aza‐substitution, allowing for fast and blue CT emission. This concept allows the interference of 3LE phosphorescence to be avoided at room temperature. The approach is extended to two N substitutions at the optimal location in the 3‐ and 6‐positions of the carbazole skeleton. These results suggest a practical molecular design towards the development of bright and deep‐blue emitting CMA materials to tackle the stability problem of energy‐efficient deep‐blue OLEDs.

Funder: EC | EC Seventh Framework Programm | FP7 Ideas: European Research Council (FP7-IDEAS-ERC - Specific Programme: "Ideas" Implementing the Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities (2007 to 2013)); Grant(s): 338944-GOCAT, Carbene-metal-amides are soluble and thermally stable materials which have recently emerged as emitters in high-performance organic light-emitting diodes. Here we synthesise carbene-metal-amide photoemitters with CF3-substituted ligands to show sky-blue to deep-blue photoluminescence from charge-transfer excited states. We demonstrate that the emission colour can be adjusted from blue to yellow and observe that the relative energies of charge transfer and locally excited triplet states influence the performance of the deep-blue emission. High thermal stability and insensitivity to aggregation-induced luminescence quenching allow us to fabricate organic light-emitting diodes in both host-free and host-guest architectures. We report blue devices with a peak external quantum efficiency of 17.3% in a host-free emitting layer and 20.9% in a polar host. Our findings inform the molecular design of the next generation of stable blue carbene-metal-amide emitters.

A series of three zwitterionic mixed-ligand bis(carbene) complexes of copper (1), silver (2) and gold (3) have been synthesized, based on a combination of ethyl-substituted cyclic (alkyl)(amino)carbene (Et2CAAC) and an anionic methyl-malonate-derived N-heterocyclic carbene (maloNHC). The crystal structures confirm the linear two-coordinate geometry without close intermolecular contacts. The compounds show blue-white phosphorescence consistent with a wide HOMO-LUMO energy gap (2.87–3.07 eV) estimated by cyclic voltammetry. The excited state lifetimes of crystalline powders decrease in the series Cu > Ag > Au, from 400 µs for copper 1 to 50 µs for the gold complex 3. DFT calculations indicate a large change in the transition dipole moment on excitation, of up to 16 D.

New luminescent "carbene-metal-amide"(CMA) Cu, Ag, and Au complexes based on monocyclic (C6) or bicyclic six-ring (BIC6) cyclic (alkyl)(amino)carbene ligands illustrate the effects of LUMO energy stabilization, conformational flexibility, excited state energy, and geometry on the photoluminescent properties, leading to 100% luminescence quantum yields, short excited state lifetimes Cu > Au > Ag down to 0.5 μs, and high radiative rates of 106 s-1. Gold complexes with the BIC6 ligand exhibit exceptional photostability under hard and soft UV light compared with analogous complexes with C5 and C6 carbenes. Steady-state and time-resolved photoluminescence spectroscopy at 298 and 77 K enabled an estimate of the energy levels of the charge transfer (CT) and locally excited (LE) states with singlet and triplet character. A four-state model is applied to describe thermally activated delayed fluorescence (TADF) properties in CMA materials and correlates excited state lifetimes with the energy difference between LE and CT states.

New luminescent “carbene-metal-amide” (CMA) Cu, Ag and Au complexes based on monocyclic (C6) or bicyclic six-ring (BIC6) cyclic (alkyl)(amino)carbene ligands illustrates the effects of LUMO energy stabilization, conformational flexibility and excited state energy on the photoemission properties, leading to near-quantitative quantum yields, short excited state lifetimes Cu > Au > Ag down to 0.5 µs and high radiative rates of 106 s–1.

Six ruthenium(II)- and four gold(I)-phosphine based complexes were synthesized and fully characterized. Some of them displayed strong antiproliferative properties for several types of cancer including colon, breast, and lung. Notably, two of the Ru(II) complexes displayed an IC50 of around 2 μM, which is exceptional for these types of complexes. The dramatic impact of the nature of the arene coordinated on the ruthenium center was clearly evidenced.

International audience; Herein we report the synthesis of new ditopic ligands, which consist of a phenoxy group and N,N,N'trisubstituted amidines linked by a methylene spacer (L1-L4). Their coordination chemistry has been studied/investigated with Zn(II) and Al(III). Alkane elimination route between the phenol-amidine proligands (L1H-L4H) and Et2Zn led to dinuclear complexes [(L1-L4)ZnEt]2 (1a-4a) in which the Zn centers are chelated by phenoxyamidine ligands and bridged through the oxygen atom of the phenoxy groups. Salt metathesis reaction between two equivalents of the sodium amidine phenate L1Na and ZnCl2 led to a bis-chelate chiral spiro-complex (L12Zn) 1a'. Analogous alkane elimination route between AlMe3 and the phenol-amidine proligands L1H-L4H allowed the preparation of the mononuclear complexes [(L1-L4)AlMe2] (1b-4b). The phenoxyamidine-Al and Zn complexes have been characterized by NMR spectroscopy, elemental analysis and/or high resolution ESI-MS. The solid state structures of the proligands [L1H2][Br] and L2H as well as of six complexes have been established by single crystal X-ray diffraction analysis. Fluxional properties of the proligands L1H-L2H and of the complexes 1a and 2b have been investigated by VT NMR experiments. In the presence of an alcohol source, complexes 1a-4a and 1b-4b were used as initiators for the controlled ring-opening polymerization (ROP) of rac-lactide to afford atactic polylactic acid (PLA).

Rational design of ruthenium complexes with optimized ligands is a promising approach to modulate their stability and antiproliferative effects in cancerous cells. The release of ligands from the coordination sphere of the ruthenium complexes can lead to the formation of biologically active Ru species that are able to exert cytotoxic effects. Herein, we have studied this approach on four ruthenium(II) complexes bearing (3,5-cycloheptadienyl)diphenylphosphine or (cycloheptyl)diphenylphosphine and ethylbenzoate or p-cymene and an unusual bimetallic analogue. The stability of the complexes was investigated in DMF as well as DMEM/FBS using 1H and 31P{1H} NMR spectroscopy. We studied the photo-cytotoxicities of the complexes in two cell lines – HeLa and RPE-1 – to understand their behavior and cytotoxicity upon ligand dissociation. All complexes showed moderate to high cytotoxicity in the two cell lines upon light irradiation.

Three new gold(I)-coumarin-based trackable therapeutic complexes and two non-trackable analogues have been synthesised and fully characterised. They all display anti-proliferative properties on several types of cancer cell lines, including those of colon, breast, and prostate. Two complexes displayed significant anti-inflammatory effects; one displayed pro-inflammatory behaviour; this highlights the impact of the position of the fluorophore on the caffeine scaffold. Additionally, the three coumarin derivatives could be visualised in vitro by two-photon microscopy.

International audience; The synthesis and characterization of a series of arene ruthenium complexes bearing either (3,5-cycloheptadienyl)diphenylphosphine or (cycloheptyl)-diphenylphosphine are reported. Upon irradiation or heating, all these complexes lose their arene ligand but then exhibit a different behavior depending on the nature of the phosphine ligand. (Cycloheptadienyl)phosphine complexes 1 and 3 give a cationic dinuclear Ru complex 5 for which the two Ru atoms are bridged by three chlorido ligands and flanked by two tridendate (cycloheptadienyl)phosphines. (Cycloheptyl)-diphenylphosphine complexes 2 and 4 undergo arene exchange when toluene is used as solvent or degrade in dithloromethane. ATRA catalytic trials conducted in parallel with these complexes using CCl4 and styrene as standard substrates, highlighted the deep impact of the dienyl moiety on the results. Under smooth conditions (UV irradiation or moderate heating), only (cycloheptyl)phosphine derivatives give Karasch adduct in satisfactory yields. Their performance was considerably improved by combining irradiation and heating. At higher temperature, cationic dinuclear complex 5 was revealed as active and robust, giving turnover numbers as high as 9700 when tetradecene and CCl4 were used as substrates.

Gold phosphine complexes, such as auranofin, have been recognized for decades as antirheumatic agents. Clinical trials are now underway to validate their use in anticancer or anti-HIV treatments. However, their mechanisms of action remain unclear. A challenging question is whether the gold phosphine complex is a prodrug that is administered in an inactive precursor form or rather that the gold atom remains attached to the phosphine ligand during treatment. In this study, we present two novel gold complexes, which we compared to auranofin and to their phosphonium analogue. The chosen ligand is a phosphine-based smart probe, whose strong fluorescence depends on the presence of the gold atom. The in vitro biological action of the gold complexes and the phosphonium derivative were investigated, and a preliminary in vivo study in healthy zebrafish larvae allowed us to evaluate gold complex biodistribution and toxicity. The different analyses carried out showed that these gold complexes were stable and behaved differently from phosphonium and auranofin, both in vitro and in vivo. Two-photon microscopy experiments demonstrated that the cellular targets of these gold complexes are not the same as those of the phosphonium analogue. Moreover, despite similar IC50 values in some cancer cell lines, gold complexes displayed a low toxicity in vivo, in contrast to the phosphonium salt. They are therefore suitable for future in vivo investigations.

Two p-cymene-ruthenium complexes 1 and 2 were isolated in high yields by treating the [RuCl2(p-cymene)]2 dimer with new hybrid phosphane- or NHC-linked diene ligands. Both complexes were fully characterized by NMR spectroscopy, and the molecular structure of the ruthenium–p-cymene complex 1, containing the phosphane–diene ligand system, was determined by X-ray diffraction analysis. The catalytic activities of both compounds were probed in atom-transfer radical addition (ATRA) and polymerization (ATRP), in the cyclopropanation of olefins, in the ring-opening metathesis polymerization (ROMP) of norbornene, and in the synthesis of enol esters from hex-1-yne and 4-acetoxybenzoic acid.

International audience; Two new gold(I)–BODIPY–imidazole based trackable therapeutic bimetallic complexes have been synthesized and fully characterized. They display strong antiproliferative properties on several types of cancers including colon, breast, and prostate and one of them presents a significant anti-inflammatory effect. Additionally, the two compounds could be visualised in vitro by confocal microscopy in the submicromolar range.

International audience; The remarkable photothermal properties of pegylated nickel-bis(dithiolene) complexes in water can induce cell death under laser irradiation in the near infrared (NIR) region.