Four diplatinum(II) complexes with the formula [Pt(pypm)(μ-F n )] 2 (2, 3a−c) bearing both a pyridine-pyrimidinate chelate and formamidinate bridge, where (pypm)H and F n H stand for 5-(pyridin-2-yl)-2-(trifluoromethyl)pyrimidine and functional formamidines with various substituents of i Pr (n = 1), Ph (n = 2), C 6 H 4 t Bu (n = 3), and C 6 H 4 CF 3 (n = 4), were synthesized en route from a mononuclear intermediate represented by [Pt(pypm)Cl-(F 1 H)] (1). Single-crystal X-ray diffraction studies confirmed the structure of 1 and 3a comprised of an individual "Pt(pypm)" unit and two "Pt(pypm)" units with a Pt•••Pt distance of 2.8845(2) Å, respectively. Therefore, in contrast to the structured emission of mononuclear 1 with the first vibronic peak wavelength at 475 nm, all other diplatinum complexes with shortened Pt•••Pt separation exhibited greatly red shifted and structureless metal−metal to ligand charge transfer (MMLCT) emission that extended into the near-infrared region in solid states. Their photophysical characteristics were measured under three distinctive morphological states (i.e., crystals, sublimed powders, and vacuum-deposited thin films) by steady-state UV−vis spectroscopy, while retention of Pt•••Pt interactions in deposited thin films of 2 and 3a−c was confirmed using Raman spectroscopy, demonstrating lowered Pt•••Pt stretching at 80−200 cm −1 . Most importantly, complexes 3a−c exhibited a gradual red shift with the trends crystals < sublimed powders < vacuum-deposited thin films, a result of increased intermolecular π−π stacking interactions and Pt•••Pt interactions, while crystalline samples exhibited the highest luminescence among all three morphological states due to the fewest defects in comparison to other morphologies. Finally, 3b was selected as a nondoped emitter for the fabrication of NIR-emitting OLEDs, giving an electroluminescence peak at 767 nm and a maximum external quantum efficiency of 0.14% with negligible roll-off.
In this letter, we demonstrate the first verticalchannel organic transistor using nanoimprint technology to produce a base electrode with high-density nanometer pores to well control the channel current vertically flowing through the pores. The aspect ratios of nanopores, which determine the switching performance of the vertical transistor, are greatly enhanced by transferring the nanostructure to the underlying layers. Without pore accumulation, a low leakage current can be achieved. The vertical transistor delivers an ON current of 0.35 mA/cm 2 and an ON/OFF current ratio of around 3000 at 1.8 V. The results prove the feasibility to produce low-voltage organic transistors over a large area with potentially low production cost.
A hybrid crystal–glass metamaterial fiber architecture foregrounds the prospect of intracavity and resonant SHG conversions for monolithically integrated photonic circuits.
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