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Synthesis, Structural Characterization, Photophysics, and Broadband Nonlinear Absorption of a Platinum(II) Complex with the 6‐(7‐Benzothiazol‐2′‐yl‐9,9‐diethyl‐9 H ‐fluoren‐2‐yl)‐2,2′‐bipyridinyl Ligand
Author(s) -
Zhang Bingguang,
Li Yunjing,
Liu Rui,
Pritchett Timothy M.,
Azenkeng Alexander,
Ugrinov Angel,
Haley Joy E.,
Li Zhongjing,
Hoffmann Mark R.,
Sun Wenfang
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201103095
Subject(s) - excited state , singlet state , chemistry , absorption (acoustics) , absorption spectroscopy , ultrafast laser spectroscopy , photochemistry , triplet state , ground state , atomic electron transition , spectroscopy , materials science , spectral line , atomic physics , optics , physics , quantum mechanics , composite material , astronomy
A platinum complex with the 6‐(7‐benzothiazol‐2′‐yl‐9,9‐diethyl‐9 H ‐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 1 π–π* absorption at λ abs <440 nm, and a broad, moderate 1 M LCT/ 1 LLCT transition at 440–520 nm in CH 2 Cl 2 solution. A structured 3 π – π*/ 3 M LCT 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 1 π–π* and 3 π–π* excited states of the 6‐(7‐benzothiazol‐2′‐yl‐9,9‐diethyl‐9 H ‐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 CH 2 Cl 2 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.