TY - JOUR
T1 - Near-Infrared Emission Induced by Shortened Pt-Pt Contact
T2 - Diplatinum(II) Complexes with Pyridyl Pyrimidinato Cyclometalates
AU - Wang, Sheng Fu
AU - Fu, Li-Wen
AU - Wei, Yu-Chen
AU - Liu, Shih-Hung
AU - Lin, Jia-An
AU - Lee, Gene-Hsiang
AU - Chou, Pi-Tai
AU - Huang, Jian-Zhi
AU - Wu, Chih-I
AU - Yuan, Yi
AU - Lee, Chun-Sing
AU - Chi, Yun
PY - 2019/10/21
Y1 - 2019/10/21
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.inorgchem.9b01754
DO - 10.1021/acs.inorgchem.9b01754
M3 - RGC 21 - Publication in refereed journal
C2 - 31565936
SN - 0020-1669
VL - 58
SP - 13892−13901
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 20
ER -