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Additional details of the thermogravimetric analysis, emissive properties, topographical steric maps, and theoretical studies (PDF)., Coordinates of the optimized structures (XYZ).

Complete experimental section; copies of 1H and 13C NMR spectra for all new compounds; copies of the absorption (UV–vis) and excitation/emission spectra of complexes 3–6; decay curves and fitting data for the determination of the half-life time of complexes 3–6; Cartesian coordinates of all new optimized complexes 3–6 in the ground state using the wB97XD and M06-2X functionals; Cartesian coordinates of S1 optimized geometries using the wB97XD and M06-2X functionals; tables of calculated orbital energies (Hartree) and metal participation, along with the HOMO–LUMO gap (eV) using the wB97XD and M06-2X functionals for the ground state of 3–6; tables with the calculated vertical transitions for the lowest T1, T2, T3, S1, and S2 excited states of 3–6 with the wB97XD and M06-2X functionals; tables with the calculated emission properties from the S1 optimized geometry for the lowest T1, T2, T3, S1, and S2 excited states of 3–6 with the wB97XD and M06-2X functionals; crystallographic tables of compounds 1a, 1e, 3c, 3d, 3g and 7h; and discussion of the structures of compounds 1a, 1e, 3c, 3d, 3g, and 7h.

In luminescent species triplet harvesting and emission through phosphorescence or thermally activated delayed fluorescence (TADF) (Figure 1) represent advantageous mechanisms which make them interesting species for OLED design. Our interest is focused on group 11 complexes displaying such properties. In this work different group 11 N-heterocyclic carbene complexes with different ancillary P, N or C ligands (L) (Figure 2) are studied. The complexes presented have been characterised by different analytical techniques: nuclear magnetic resonance (NMR), mass spectrometry and X-ray crystallography. In addition, the optical properties of the complexes, emission and excitation energies, lifetimes and quantum yields have been analysed.

Trigonal planar coordination at gold allows phosphorescent 3MC transitions, not expected for luminescent mononuclear linear gold complexes. The careful selection and nature of the ancillary ligands bonded to gold, being fluorophore groups or not emissive ligands may cause a distortion of ideal trigonal planar coordination favoring different origins for the emissions. Consequently, intraligand (IL) or charge transfer (CT) transitions may be present and besides the expected phosphorescent MC transitions, fluorescence or thermally activated delayed fluorescence (TADF) may be the origin of the luminescence. In addition of the advantages of triplet population and deactivation via phosphorescent or delayed fluorescence processes, these systems are very versatile and may show interesting properties such as mechanochromism and vapochromism and, consequently, have revealed as promising candidates for optical applications. The objective of this review is to provide an overview of the reported luminescent three-coordinated gold systems and to get insight into their emissive properties.

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)2 to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C–H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.

PMMA composites and solids of complexes of formulas [AgX(P–P)]n [n = 1 and 2; X = Cl, NO3, ClO4, CF3COO, and OTf; P–P = dppb, xantphos, (PR2)2C2B10H10 (R = Ph and iPr)] display the whole palette of colors from blue to red upon selection of the anionic ligand (X) and the diphosphane (P–P). The diphosphane seems to play the most important role in tuning the emission energy and thermally activated delayed fluorescence (TADF) behavior. The PMMA composites of the complexes exhibit higher quantum yields than that of the diphosphane ligands and those with dppb are between 28 and 53%. Remarkably, instead of blue-green emissions which dominate the luminescence of silver diphosphane complexes in rigid phases, those with carborane diphosphanes are yellow-orange or orange-red emitters. Theoretical studies have been carried out for complexes with P–P = dppb, X = Cl; P–P = dppic, X = NO3; P–P = dppcc, X = Cl, NO3, and OTf and the mononuclear complexes [AgX(xantphos)] (X = Cl, Br). Optimization of the first excited triplet state was only possible for [AgX(xantphos)] (X = Cl and Br). A mixed MLCT and MC nature could be attributed to the S0 → T1 transition in these three-coordinated complexes.

Phosphorescence in the liquid crystal state with one of the highest quantum yield values, 42%, at room temperature is reported. This property is achieved with cyclic trinuclear copper(I) complexes prepared using 3,5-dimethyl-4-(trialkoxyphenyl)pyrazolate ligands. The compounds show well-organized hexagonal columnar mesophases that are stable at room temperature or near room temperature with intracolumnar order at distances of 3.6 Å, red emission and lifetimes consistent with the excimeric metal-centered phosphorescence typical of copper trinuclear pyrazolato complexes. A non-mesogenic analogue shows similar properties, and the single crystal structure is formed by stacked molecules forming a supramolecular extended structure with two different intermolecular Cu⋯Cu contacts, 3.368 Å and 3.666 Å, which are in the range of previously reported weak cuprophilic interactions. The results demonstrate that metallomesogens with efficient room temperature phosphorescence can be obtained with metal complexes other than the widely explored and precious metal-based iridium or platinum complexes.

Three cyclic trinuclear pyrazolate complexes with Au(I), Ag(I), or Cu(I) have been studied. These complexes have interesting and distinct optical and thermal properties depending on the metal, namely, liquid crystalline behavior, red or deep-red phosphorescence at room temperature, thermoluminochromism, and response to silver ions. The selected ligand, 4-hexyl-3,5-dimethylpyrazolate, maximizes the effect that the nature of the metals has on the properties of the complexes, thus allowing the intermolecular metallophilic interactions to be responsible for the optical properties. Moreover, the gold and silver complexes show columnar liquid crystal phases at high temperature. All of the complexes have good solubility properties for processing as poly(methyl methacrylate) (PMMA) doped films. Films of the gold, silver, and copper complexes show interesting optical behavior such as wide-range color switching or phosphorescence turn-on upon cooling. In addition, films of the gold complex show a bright color switching (red to blue) in the presence of silver ions. The gold and copper complexes are bright phosphors with phosphorescent quantum yields of 90% in PMMA films, the highest values reported for this class of compounds at room temperature.

Este trabajo recoge la síntesis y caracterización de complejos catiónicos y neutros de cobre(I) con el ligando 2-(2’-piridil)benzimidazol y diferentes difosfinas. Los complejos obtenidos se han empleado en la preparación de materiales compuestos con PMMA de los cuales se han estudiado sus propiedades emisoras para analizar la influencia de la variación de la difosfina y el carácter neutro o catíonico del complejo en dichas propiedades.