Toward Tunable Electroluminescent Devices by Correlating Function and Submolecular Structure in 3D Crystals, 2D-Confined Monolayers, and Dimers

Abstract

The synthesis of new Pt(II) complexes bearing tailored cyclometalated C^N*N^C luminophores is reported along with their photophysical properties. The emission of the monomeric species can be blue shifted upon formal isosteric replacement of two C-H units by N atoms at the two cyclometalating rings. Their remarkable stability upon sublimation was demonstrated by means of scanning tunneling microscopy, which also revealed a defined self-assembly behavior leading to supramolecular arrays, showing a 3-fold symmetry in 2D-confined monolayers. The supramolecular organization is driven by van der Waals interactions of the side chains and does not depend on the nature of the luminophores, as also observed in the crystalline phases showing no significant Pt-Pt interactions in 3D. Conversely, the luminescence properties in glassy matrices at 77 K and in amorphous solids are indicative of intermolecular interactions with sizable intermetallic coupling, which was demonstrated by reproducing the emission spectra of dimeric species by means of (TD)DFT calculations. The tendency toward aggregation was also traceable by cyclic voltammetry, whereas thermogravimetric analyses confirmed their stability. Solution-processed and vacuum-deposited OLED devices showed a concentration-dependent electroluminescence that red shifts with increasing doping ratios. Due to the stability of the complexes, solution-processed and vacuum-deposited devices showed identical electroluminescence spectra. Besides favoring aggregation, introduction of two N atoms has a detrimental effect on the device performance, due to the prolonged excited-state lifetimes favoring triplet-triplet annihilation.

Structural Tunability and Diversity of Two‐Dimensional Lead Halide Benzenethiolate

“…[23,24] This PL lifetimei sl ongert han that of most transition metal dichalcogenides and n = 12 Dh alide perovskite materials, [25] but much shorter than that of phosphorescent materials with triplet emission. [26,27] Recently,s imilar broad emission states with al arge Stokes shift have been observed in many halide-based perovskites and perovskite-like materials. [24][25][26] It is generally believed that such intriguing emissions arise from self-trapped excitons associated with as oft and deformable crystal lattice.…”

“…[26,27] Recently,s imilar broad emission states with al arge Stokes shift have been observed in many halide-based perovskites and perovskite-like materials. [24][25][26] It is generally believed that such intriguing emissions arise from self-trapped excitons associated with as oft and deformable crystal lattice. [24][25][26] Density functional theory (DFT) calculations were performed to better understand the bonding properties, energetics, and band structures.…”

“…[24][25][26] It is generally believed that such intriguing emissions arise from self-trapped excitons associated with as oft and deformable crystal lattice. [24][25][26] Density functional theory (DFT) calculations were performed to better understand the bonding properties, energetics, and band structures. Projected density of states (PDOS) and the band structure of Pb 2 I(S-C 6 H 5 ) 3 were obtained to reveal the characteristics of the valence bands and conduction bands.…”

Reaktive Oberflächenplanarisierung von Pt(II)‐Komplexen

“…Hier berichten wir vom unerwarteten oberflächen-vermittelten Bruch einer CÀN-Bindung in einer Reihe organometallischer Pt(II)-Komplexe mit tetradentaten Liganden. Um zu untersuchen, welche Faktoren den C À N-Bindungsbruch beeinflussen, wurden Pt(II)-Ausgangskomplexe mit unterschiedlichen Einheiten am verbrückenden N-Atom in Lçsung mittels geeigneter Synthese [14] hergestellt (s. Schema 1) und dann auf drei verschiedene Metalloberflächen (Au(111), Ag(111), and Cu(111)) im Ultrahochvakuum [15] sublimiert (siehe Hintergrundinformationen zu experimentellen Details und spektroskopischer Charakterisierung). Diese Reihe von Experimenten zielt darauf ab,d en Einfluss der chemischen Komposition und Geometrie der Pt(II)-Komplexe sowie die Beschaffenheit des Substrats auf den CÀ N-Bindungsbruch zu beleuchten.…”

“…Daneben kçnnen auch intakte Monomere anhand ihrer hellen Phenylbrücke und einem hellen Mittelpunkt, der dem herausragenden d z 2 -Orbital des Pt-Zentrums zuzuordnen ist, klar identifiziert werden. [14] Daraufhin wurde die Probe 10 min lang einer Temperatur von 435 Ka usgesetzt. Es entstanden einige kleeblattfçrmige Gebilde (s.Abbildung S60 b), die als Komplex C2 identifiziert werden kçnnen.…”