Cyclometalated Platinum(II) Complex with Strong and Broadband Nonlinear Optical Response

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• 作者：Pin Shao ; Yunjing Li ; Wenfang Sun
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：February 14, 2008
• 年：2008
• 卷：112
• 期：6
• 页码：1172 - 1179
• 全文大小：224K
• 年卷期：v.112,no.6(February 14, 2008)
• ISSN：1520-5215

文摘

A cyclometalated platinum(II) 4,6-diphenyl-2,2'-bipyridyl pentynyl complex (1) has been synthesized andstructurally characterized. Its photophysical and third-order nonlinear optical properties have been systematicallyinvestigated. This complex exhibits a metal-to-ligand charge-transfer (¹MLCT) absorption band between 400and 500 nm and a ³MLCT emission band at ~591 nm at room temperature with a lifetime of ~100 ns. At77 K, the emission band blue shifts. Both UV-vis absorption and emission spectra show solvent dependence.Low-polarity solvents cause a bathochromic shift of the absorption and emission bands. This complex alsoexhibits a broad and strong transient absorption from the near-UV to the near-IR spectral region, with atriplet absorption coefficient of 4933 L·mol^-1·cm^-1 at 585 nm and a quantum yield of 0.51 for the formationof the triplet excited state. Nonlinear transmission and Z-scan techniques were employed to characterize thethird-order nonlinearities of this complex. A strong and broadband reverse saturable absorption was observedfor nanosecond and picosecond laser pulses due to the reduced ground-state absorption in the visible spectralrange. It also exhibits a self-defocusing effect at 532 nm for nanosecond laser pulses. The excited-stateabsorption cross section deduced from the open-aperture Z-scan increases at longer wavelengths, with anexceptionally large ratio of excited-state absorption to ground-state absorption of 160 at 570 nm for picosecondlaser pulses.