Regioisomerism in cationic sulfonyl-substituted [Ir(C^N)2(N^N)]+ complexes: its influence on photophysical properties and LEC performance

In a series of regioisomeric [Ir(C^N) 2 (bpy)] + complexes containing methylsulfonyl groups on the cyclometallating ligands, the influence of the substitution position on photophysical, electrochemical and LEC device properties is investigated

Highly stable and efficient light-emitting electrochemical cells based on cationic iridium complexes bearing arylazole ancillary ligands

A series of bis-cyclometalated iridium(III) complexes of general formula [Ir(ppy)2(N∧N)][PF6] (ppy− = 2-phenylpyridinate; N∧N = 2-(1H-imidazol-2-yl)pyridine (1), 2-(2-pyridyl)benzimidazole (2), 1-methyl-2-pyridin-2-yl- 1H-benzimidazole (3), 2-(4′-thiazolyl)benzimidazole (4), 1- methyl-2-(4′-thiazolyl)benzimidazole (5)) is reported, and their use as electroluminescent materials in light-emitting electrochemical cell (LEC) devices is investigated. [2][PF6] and [3][PF6] are orange emitters with intense unstructured emission around 590 nm in acetonitrile solution. [1][PF6], [4][PF6], and [5][PF6] are green weak emitters with structured emission bands peaking around 500 nm. The different photophysical properties are due to the effect that the chemical structure of the ancillary ligand has on the nature of the emitting triplet state. Whereas the benzimidazole unit stabilizes the LUMO and gives rise to a 3MLCT/3LLCT emitting triplet in [2][PF6] and [3][PF6], the presence of the thiazolyl ring produces the opposite effect in [4][PF6] and [5][PF6] and the emitting state has a predominant 3LC character. Complexes with 3MLCT/3LLCT emitting triplets give rise to LEC devices with luminance values 1 order higher than those of complexes with 3LC emitting states. Protecting the imidazole N−H bond with a methyl group, as in complexes [3][PF6] and [5][PF6], shows that the emissive properties become more stable. [3][PF6] leads to outstanding LECs with simultaneously high luminance (904 cd m−2), efficiency (9.15 cd A−1), and stability (lifetime over 2500 h).Spanish Ministry of Economy and Competitiveness (MINECO) of Spain (projects CTQ2014- 58812-C2-1-R, MAT2014-55200, CTQ2014-55583-R, CTQ2014-61914-EXP, CTQ2015-71955-REDT, CTQ2015- 70371-REDT, CTQ2015-71154-P, and Unidad de Excelencia Marıá de Maeztu MDM-2015-0538), European Feder funds (CTQ2015-71154-P), Obra Social “la Caixa” (OSLC-2012- 007), Junta de Castilla y León (BU033-U16), and Generalitat Valenciana (Prometeo2016/135

CF3 Substitution of [Cu(P^P)(bpy)][PF6] complexes: Effects on Photophysical Properties and Light-emitting Electrochemical Cell Performance

We report [Cu(P^P)(N^N)][PF 6 ] complexes with P^P = bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos), N^N = CF 3 -substituted 2,2'-bipyridines (6,6'-(CF 3 ) 2 bpy, 6-CF 3 bpy, 5,5'-(CF 3 ) 2 bpy, 4,4'-(CF 3 ) 2 bpy, 6,6'-Me 2 -4,4'-(CF 3 ) 2 bpy). We present the effects of CF 3 substitution on structures, and electrochemical and photophysical properties. The HOMO–LUMO gap is tuned by the N^N ligand; the largest redshift in the MLCT band is for [Cu(P^P)(5,5'-(CF 3 ) 2 bpy)][PF 6 ]. In solution, the compounds are weak yellow to red emitters. The emission properties depend on the substitution pattern but this cannot be explained by simple electronic arguments. For powders, [Cu(xantphos)(4,4'-(CF 3 ) 2 bpy)][PF 6 ] has the highest PLQY (50.3%) with an emission lifetime of 12 µs. Compared to 298 K solution behaviour, excited state lifetimes lengthen in frozen Me-THF (77 K) indicating thermally activated delayed fluorescence (TADF). TD-DFT calculations show that the energy gap between the lowest-energy singlet and triplet excited states (0.12–0.20 eV) permits TADF. LECs with [Cu(POP)(6-CF 3 bpy)][PF 6 ], [Cu(xantphos)(6-CF 3 bpy)][PF 6 ] or [Cu(xantphos)(6,6'-Me 2 -4,4'-(CF 3 ) 2 bpy)][PF 6 ] emit yellow electroluminescence. A LEC with [Cu(xantphos)(6,6'-Me 2 -4,4'-(CF 3 ) 2 bpy)][PF 6 ] had the fastest turn-on time (8 min); the LEC with the longest lifetime ( t 1/2 = 31 h) contained [Cu(xantphos)(6-CF 3 bpy)][PF 6 ]; these LECs reached maximum luminances of 131 and 109 cd m –2

Phosphane tuning in heteroleptic [Cu(N^N)(P^P)]+ complexes for light-emitting electrochemical cells

The synthesis and characterization of five [Cu(P^P)(N^N)][PF6] complexes in which P^P = 2,7-bis(tert-butyl)-4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (tBu2xantphos) or the chiral 4,5-bis(mesitylphenylphosphino)-9,9-dimethylxanthene (xantphosMes2) and N^N = 2,2'-bipyridine (bpy), 6-methyl-2,2'-bipyridine (6-Mebpy) or 6,6'-dimethyl-2,2'-bipyridine (6,6'-Me2bpy) are reported. Single crystal structures of four of the compounds confirm that the copper(I) centre is in a distorted tetrahedral environment. In [Cu(xantphosMes2)(6-Mebpy)][PF6], the 6-Mebpy unit is disordered over two equally populated orientations and this disorder parallels a combination of two dynamic processes which we propose for [Cu(xantphosMes2)(N^N)]+ cations in solution. Density functional theory (DFT) calculations reveal that the energy difference between the two conformers observed in the solid-state structure of [Cu(xantphosMes2)(6-Mebpy)][PF6] differ in energy by only 0.28 kcal mol‒1. Upon excitation into the MLCT region (λexc = 365 nm), the [Cu(P^P)(N^N)][PF6] compounds are yellow to orange emitters. Increasing the number of Me groups in the bpy unit shifts the emission to higher energies, and moves the Cu+/Cu2+ oxidation to higher potentials. Photoluminescence quantum yields (PLQYs) of the compounds are low in solution, but in the solid state, PLQYs of up to 59% (for [Cu(tBu2xantphos)(6,6'-Me2bpy)]+) are observed. Greatly increased excited-state lifetimes at low temperature are consistent with the complexes exhibiting thermally activated delayed fluorescence (TADF). This is supported by the small energy difference calculated between the lowest-energy singlet and triplet excited states (0.17-0.25 eV). The compounds were tested in simple bilayer light-emitting electrochemical cells (LECs). The optoelectronic performances of complexes containing xantphosMes2 were generally lower with respect to those with tBu2-xantphos, which led to bright and efficient devices. The best performing LECs were obtained for the complex [Cu(tBu2xantphos)(6,6'-Me2bpy)][PF6] due to the increased steric hindrance at the N^N ligand resulting in higher PLQY

Luminescent copper(I) complexes with bisphosphane and halogen-substituted 2,2'-bipyridine ligands

Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is a halo-substituted 2,2'-bipyridine (bpy) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9- dimethylxanthene (xantphos) have been synthesized and investigated. To stabilize the tetrahedral geometry of the copper(I) complexes, the steric demands of the bpy ligands have been increased by introducing 6- or 6,6'-halo-substituents in 6,6'-dichloro-2,2'-bipyridine (6,6'-Cl2bpy), 6-bromo-2,2'- bipyridine (6-Brbpy) and 6,6'-dibromo-2,2'-bipyridine (6,6'-Br2bpy). The solid-state structures of [Cu(POP)(6,6'-Cl2bpy)][PF6], [Cu(xantphos)(6,6'-Cl2bpy)][PF6].CH2Cl2, [Cu(POP)(6-Brbpy)][PF6] and [Cu(xantphos)(6-Brbpy)][PF6].0.7Et2O obtained from single crystal X-ray diffraction are described including the pressure dependence of the structure of [Cu(POP)(6-Brbpy)][PF6]. The copper(I) complexes with either POP or xantphos and 6,6'-Cl2bpy, 6-Brbpy and 6,6'-Br2bpy are orange-to-red emitters in solution and yellow-to-orange emitters in the solid state, and their electrochemical and photophysical properties have been evaluated with the help of density functional theory (DFT) calculations. The emission properties are strongly influenced by the substitution pattern that largely affects the geometry of the emitting triplet state. [Cu(POP)(6,6'-Cl2bpy)][PF6] and [Cu(xantphos)(6,6'-Cl2bpy)][PF6] show photoluminescence quantum yields of 15 and 17%, respectively, in the solid state, and these compounds were tested as luminophores in light-emitting electrochemical cells (LECs). The devices exhibit orange electroluminescence and very short turn-on times (<5 to 12 s). Maximum luminance values of 121 and 259 cd m−2 for [Cu(POP)(6,6'-Cl2bpy)][PF6] and [Cu(xantphos)(6,6'-Cl2bpy)][PF6], respectively, were achieved at an average current density of 100 A m−2; external quantum efficiencies of 1.2% were recorded for both complexes

Recent advances in the development of anti-infective prophylactic and/or therapeutic agents based on Toll-Like Receptor (TLRs)

Toll-like receptors (TLRs) are key players in innate immunity. They are able to sense different microorganisms ranging from protozoa to bacteria, fungi or viruses. Innate immune responses can directly influence adaptive immune responses. Therefore, TLRs are considered as relevant targets for therapeutic applications in immune diseases: such as autoimmune disorders, allergy, sepsis, and cancer. We here review the recent patents based on the modulation of the toll-like receptors to develop anti-infective (prophylactic and/or therapeutic) agents.This work was supported by the Junta de Comunidades de Castilla-La Mancha (JCCM), project PII1I09-0243-4350.Peer Reviewe

Exploring the effect of the cyclometallating ligand in 2-(pyridine-2-yl)benzo[d]thiazole-containing iridium(III) complexes for stable light-emitting electrochemical cells

The preparation and characterization of a series of iridium(III) ionic transition-metal complexes for application in light-emitting electrochemical cells (LECs) are reported. The complexes are of the type [Ir(C^N) 2 (N^N)][PF 6 ] in which C^N is one of the cyclometallating ligands 2-(3-( tert -butyl)phenyl)pyridine (tppy), 2-phenylbenzo[ d ]thiazole (pbtz), 1-phenyl-1 H -pyrazole (ppz) and 1-phenylisoquninoline (piq), and N^N is 2-(pyridine-2-yl)benzo[ d ]thiazole (btzpy). The variation in the C^N ligands allows the HOMO energy level to be tuned, leading to HOMO−LUMO gaps in the range 2.76‒3.01 eV and values of of 0.81‒1.11 V. In solution, the complexes are orange to deep-red emitters ( λ max in the range 600-660 nm), with quantum yields between 2% for [Ir(tppy) 2 (btzpy)][PF 6 ] to 41% for [Ir(pbtz) 2 (btzpy)][PF 6 ]. Similar trends for the emission maxima and photoluminescence quantum yields are observed in the solid state. Density functional theory (DFT) calculations support the charge transfer nature of the emission. Very bright electroluminescence was observed for LECs containing [Ir(pbtz) 2 (btzpy)][PF 6 ], although the device was not stable under continuous operation; this is attributed to an unbalanced charge distribution and/or to a fast ionic migration. Significantly, LECs fabricated with [Ir(tppy) 2 (btzpy)][PF 6 ] in the active layer are very stable, produce pure red emission and show no signs of degradation over a period of 5 days of continuous operation

The shiny side of copper: bringing copper(i) light-emitting electrochemical cells closer to application

Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), 4,5,6-trimethyl-2,2′-bipyridine (4,5,6-Me3bpy), 6-(tert-butyl)-2,2′-bipyridine (6-tBubpy) and 2-ethyl-1,10-phenanthroline (2-Etphen) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP, PIN [oxydi(2,1-phenylene)]bis(diphenylphosphane)) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos, PIN (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane)) have been synthesized and their NMR spectroscopic, mass spectrometric, structural, electrochemical and photophysical properties were investigated. The single-crystal structures of [Cu(POP)(5,5′-Me2bpy)][PF6], [Cu(xantphos)(5,5′-Me2bpy)][PF6], [Cu(POP)(6-tBubpy)][PF6], [Cu(POP)(4,5,6-Me3bpy)][PF6]·1.5Et2O, [Cu(xantphos)(4,5,6-Me3bpy)][PF6]·2.33CH2Cl2, [Cu(POP)(2-Etphen)][PF6] and [Cu(xantphos)(2-Etphen)][PF6] are described. While alkyl substituents in general exhibit electron-donating properties, variation in the nature and substitution-position of the alkyl group in the N^N chelate leads to different effects in the photophysical properties of the [Cu(P^P)(N^N)][PF6] complexes. In the solid state, the complexes are yellow to green emitters with emission maxima between 518 and 602 nm, and photoluminescence quantum yields (PLQYs) ranging from 1.1 to 58.8%. All complexes show thermally activated delayed fluorescence (TADF). The complexes were employed in the active layer of light-emitting electrochemical cells (LECs). The device performance properties are among the best reported for copper-based LECs, with maximum luminance values of up to 462 cd m−2 and device half-lifetimes of up to 98 hours

A non-enzymatic ethanol sensor based on a nanostructured catalytic disposable electrode

Herein, a simple and fast method for the electrocatalytic detection of ethanol using disposable nanostructured screen-printed carbon electrodes (SPCEs) is presented for the first time. Platinum nanoparticles (PtNPs), prepared in the presence of citrate and later purified and dispersed in ultrapure water, were employed in the modification of the SPCEs (SPCE-PtNPs). The synthetized nanoparticles and the catalytic nanostructured solid surface were characterized with transmission electron microscopy (TEM) and with scanning electron microscopy (SEM), respectively. Both systems were also characterized using voltammetric techniques. Finally, the PtNPs modified SPCEs were employed for the electro-oxidation of ethanol in an alkaline medium using portable instrumentation. The electrochemical results revealed that PtNPs can effectively enhance the electron transfer between the analyte of interest and the electrode. The content of ethanol was assayed in real samples (alcoholic beverages) revealing an accurate performance. Additionally, a stability study of the nanostructured surface was carried out. The results obtained corroborate the promising catalytic activity of PtNPs in ethanol detection using disposable, cost-effective and miniaturized sensing devices.José Solla-Gullón acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante

Thienylpyridine-based cyclometallated iridium(III) complexes and their use in solid state light-emitting electrochemical cells

The synthesis and characterization of four iridium(III) complexes [Ir(thpy)2(N^N)][PF6] where Hthpy = 2-(2′-thienyl)pyridine and N^N are 6-phenyl-2,2′-bipyridine (1), 4,4′-di-tbutyl-2,2′-bipyridine (2), 4,4′-di-tbutyl-6-phenyl-2,2′-bipyridine (3) or 4,4′-dimethylthio-2,2′-bipyridine (4) are described. The single crystal structures of ligand 4 and the complexes containing the [Ir(thpy)2(1)]+ and [Ir(thpy)2(4)]+ cations have been determined. In [Ir(thpy)2(1)]+, the pendant phenyl ring engages in an intra-cation π-stacking interaction with one of the thienyl rings in the solid state, and undergoes hindered rotation on the NMR timescale in [Ir(thpy)2(1)]+ and [Ir(thpy)2(3)]+. The solution spectra of [Ir(thpy)2(1)][PF6] and [Ir(thpy)2(4)][PF6] show emission maxima around 640 nm and are significantly red-shifted compared with [Ir(thpy)2(2)][PF6] and [Ir(thpy)2(3)][PF6] which have structured emission bands with maxima around 550 and 590 nm. In thin films, the emission spectra of the four complexes are similar with emission peaks around 550 and 590 nm and a shoulder around 640 nm that are reminiscent of the features observed in solution. In solution, quantum yields are low, but in thin films, values range from 29% for [Ir(thpy)2(1)][PF6] to 51% for [Ir(thpy)2(4)][PF6]. Density functional theory calculations rationalize the structured emission observed for the four complexes in terms of the 3LC nature predicted for the lowest-energy triplet states that mainly involve the cyclometallated [thpy]− ligands. Support for this theoretical result comes from the observed features of the low temperature (in frozen MeCN) photoluminescence spectra of the complexes. Photoluminescence and electroluminescence spectra of the complexes in a light-emitting electrochemical cell (LEC) device configuration have been investigated. The electroluminescence spectra are similar for all [Ir(thpy)2(N^N)][PF6] complexes with emission maxima at ≈600 nm, but device performances are relatively poor probably due to the poor charge-transporting properties of the complexes