Near-Infrared Emission Induced by Shortened Pt-Pt Contact : Diplatinum(II) Complexes with Pyridyl Pyrimidinato Cyclometalates

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

View graph of relations

Author(s)

  • Sheng Fu Wang
  • Li-Wen Fu
  • Yu-Chen Wei
  • Shih-Hung Liu
  • Jia-An Lin
  • Gene-Hsiang Lee
  • Pi-Tai Chou
  • Jian-Zhi Huang
  • Chih-I Wu
  • Yi Yuan

Detail(s)

Original languageEnglish
Pages (from-to)13892−13901
Journal / PublicationInorganic Chemistry
Volume58
Issue number20
Online published30 Sep 2019
Publication statusPublished - 21 Oct 2019

Abstract

Four diplatinum(II) complexes with the formula [Pt(pypm)(μ-Fn)]2 (2, 3a-c) bearing both a pyridine-pyrimidinate chelate and formamidinate bridge, where (pypm)H and FnH stand for 5-(pyridin-2-yl)-2-(trifluoromethyl)pyrimidine and functional formamidines with various substituents of iPr (n = 1), Ph (n = 2), C6H4tBu (n = 3), and C6H4CF3 (n = 4), were synthesized en route from a mononuclear intermediate represented by [Pt(pypm)Cl(F1H)] (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.

Citation Format(s)

Near-Infrared Emission Induced by Shortened Pt-Pt Contact : Diplatinum(II) Complexes with Pyridyl Pyrimidinato Cyclometalates. / Wang, Sheng Fu; Fu, Li-Wen; Wei, Yu-Chen; Liu, Shih-Hung; Lin, Jia-An; Lee, Gene-Hsiang; Chou, Pi-Tai; Huang, Jian-Zhi; Wu, Chih-I; Yuan, Yi; Lee, Chun-Sing; Chi, Yun.

In: Inorganic Chemistry, Vol. 58, No. 20, 21.10.2019, p. 13892−13901.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal