期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 18, 期 15, 页码 4593-4606出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201103095
关键词
luminescence; nonlinear optics; photophysics; platinum; two-photon absorption
资金
- National Science Foundation [CHE-0449598, CHEM-0946990]
- Army Research Laboratory [W911NF-06-2-0032]
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [0946990] Funding Source: National Science Foundation
- Office Of The Director
- EPSCoR [0814442] Funding Source: National Science Foundation
A platinum complex with the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9H-fluoren-2-yl)-2,2'-bipyridinyl ligand (1) was synthesized and the crystal structure was determined. UV/Vis absorption, emission, and transient difference absorption of 1 were systematically investigated. DFT calculations were carried out on 1 to characterize the electronic ground state and aid in the understanding of the nature of low-lying excited electronic states. Complex 1 exhibits intense structured 1pp* absorption at ?abs<440 nm, and a broad, moderate 1MLCT/1LLCT transition at 440520 nm in CH2Cl2 solution. A structured 3pp*/3MLCT emission at about 590 nm was observed at room temperature and at 77 K. Complex 1 exhibits both singlet and triplet excited-state absorption from 450 nm to 750 nm, which are tentatively attributed to the 1pp* and 3pp* excited states of the 6-(7-benzothiazol-2'-yl-9,9-diethyl-9H-fluoren-2-yl)-2,2'-bipyridine ligand, respectively. Z-scan experiments were conducted by using ns and ps pulses at 532 nm, and ps pulses at a variety of visible and near-IR wavelengths. The experimental data were fitted by a five-level model by using the excited-state parameters obtained from the photophysical study to deduce the effective singlet and triplet excited-state absorption cross sections in the visible spectral region and the effective two-photon absorption cross sections in the near-IR region. Our results demonstrate that 1 possesses large ratios of excited-state absorption cross sections relative to that of the ground-state in the visible spectral region; this results in a remarkable degree of reverse saturable absorption from 1 in CH2Cl2 solution illuminated by ns laser pulses at 532 nm. The two-photon absorption cross sections in the near-IR region for 1 are among the largest values reported for platinum complexes. Therefore, 1 is an excellent, broadband, nonlinear absorbing material that exhibits strong reverse saturable absorption in the visible spectral region and large two-photon-assisted excited-state absorption in the near-IR region.
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