ABSTRACT
The prediction of coordination modes is of high importance when structure-property relationships are discussed. Herein, the coordination chemistry of copper(i) with pyridine-amines with a varying number of coordinating N-atoms, namely pyridine-benzimidazole, -triazole and -tetrazole, or their deprotonated analogues, and different phosphines was systematically studied and the photoluminescence properties of all synthesized complexes examined and related to DFT data. Each complex was characterized by single-crystal X-ray analysis and elemental analysis, and a set of prediction rules derived for the coordination chemistry of copper(i) with these ligands. A mononuclear cationic coordination motif was found for PPh3 or DPEPhos with all N^N ligands, which exhibits blue to green luminescence of MLCT character d(Cu) â π*(pyridine-amine ligand) with quantum yields up to 46%. With the deprotonated N^N ligands, mononuclear neutral complexes were only expected with DPEPhos. The emission's nature of this complex type is strongly dependent on the electronic effects of the N^N ligand and was characterized as (ML + IL)CT transition. In contrast to the high quantum yields up to 78% for the tetrazolate complexes (as reported before), the triazolate and imidazolate based complexes show much lower emission efficiencies below 10%. Besides the mononuclear copper(i) complexes, cluster-type complexes were obtained, which show moderate luminescence in the blue to green region of the visible spectrum (469-505 nm).
ABSTRACT
This section covers both metal-organic and organic materials that feature thermally activated delayed fluorescence (TADF). Such materials are especially useful for organic light-emitting diodes (OLEDs), a technology that was introduced in commercial displays only recently. We compare both material classes to show commonalities and differences, highlighting current issues and challenges. Advanced spectroscopic techniques as valuable tools to develop solutions to those issues are introduced. Finally, we provide an outlook over the field and highlight future trends.
Subject(s)
Metal-Organic Frameworks/chemistry , Coordination Complexes/chemistry , Copper/chemistry , Fluorescence , Nitriles/chemistry , Quantum Theory , Sulfones/chemistry , TemperatureABSTRACT
Intersystem crossing in thermally activated delayed fluorescence (TADF) materials is an important process that controls the rate at which singlet states convert to triplets; however, measuring this directly in TADF materials is difficult. TADF is a significant emerging technology that enables the harvesting of triplets as well as singlet excited states for emission in organic light emitting diodes. We have observed the picosecond time-resolved photoluminescence of a highly luminescent, neutral copper(I) complex in the solid state that shows TADF. The time constant of intersystem crossing is measured to be 27 picoseconds. Subsequent overall reverse intersystem crossing is slow, leading to population equilibration and TADF with an average lifetime of 11.5 microseconds. These first measurements of intersystem crossing in the solid state in this class of mononuclear copper(I) complexes give a better understanding of the excited-state processes and mechanisms that ensure efficient TADF.
Subject(s)
Copper/chemistry , Fluorescence , Hot Temperature , Luminescence , Spectrometry, Fluorescence/methods , TemperatureABSTRACT
Strongly luminescent, neutral copper(I) complexes bearing 5-(2-pyridyl)tetrazolate and various phosphine ligands were synthesized. While the cationic copper(I) precursors 1b-4b do not exceed photoluminescence quantum yields (PLQY) of 4-46%, the neutral complexes 1a-4a show PLQYs of up to 89%.
Subject(s)
Coordination Complexes/chemistry , Copper/chemistry , Phosphines/chemistry , Tetrazoles/chemistry , Ligands , LuminescenceABSTRACT
Foram estudados, quanto a alteraçöes subclínicas presentes em ecocardiograma uni-bidimensional com doppler-fluxo a cores, 20 pacientes portadores de cirrose alcoólica sem manifestaçöes clínicas, radiológicas e eletrocardiográficas de cardiopatia e comparados a um grupo controle com as mesmas características e sem doença hepática. Os achados ecocardiográficos dos dois grupos foram semelhantes, levando à conclusäo de que, näo havendo sinais evidentes de comprometimento cardíaco, säo improváveis achados ecocardiográficos subclínicos indicativos de miocardiopatia nos pacientes portadores de cirrose alcoólica
