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Liu X.-G.,North Dokota State University | Sun W.,North Dokota State University
Inorganica Chimica Acta | Year: 2012

A series of platinum(II) complexes bearing 2-(7-(4-R-phenylethynyl)-9,9-dihexadecyl-fluoren-2-yl)-1,10-phenanthroline ligand were synthesized and characterized. Their photophysical properties were systematically investigated by UV-Vis absorption, emission, and transient absorption spectroscopy. All complexes exhibit 1π,π * absorption bands below 410nm and charge transfer transitions at 415-550nm in CH 2Cl 2. They all emit at ca. 624nm with vibronic structures. Both UV-Vis absorption and emission spectra show negative solvatochromic effect. All complexes exhibit broad and moderately strong triplet transient absorption from the near-UV to the near-IR spectral region. Reverse saturable absorption of these complexes in CH 2Cl 2 for ns laser pulses at 532nm was demonstrated. © 2012 Elsevier B.V. Source

Liu X.-G.,North Dokota State University | Sun W.,North Dokota State University
European Journal of Inorganic Chemistry | Year: 2013

Six platinum(II) complexes bearing 2-(9,9-dihexadecyl-7-R-fluoren-2-yl)-1, 10-phenanthroline ligands (R = NO2, CN, I, H, benzothiazole, thiophene for ligands 1-6, respectively) were synthesized and their photophysics and reverse saturable absorption (RSA) were systematically investigated. All complexes exhibit intense absorption bands between 350 and 450 nm, which are attributed to 1π,π/1ILCT (intraligand charge transfer) transitions, and broad 1MLCT (metal to ligand charge transfer) transitions between 475 and 550 nm. All complexes are emissive at room temperature in a variety of solvents and at 77 K in butyronitrile glassy matrix, with the long-lived, structured emission appearing between 600 and 750 nm. The emitting states are assigned to predominantly the 3π, π* state with an admixture of 3MLCT characters. Upon ns laser excitation at 355 nm, all complexes display broad, moderately strong transient absorption from the visible to the near-IR region. As a result, RSA is observed from all complexes at 532 nm for ns laser pulses. The strength of the RSA for these complexes follows the trend: Pt-2 > Pt-3 > Pt-4 > Pt-1 >> Pt-5 > Pt-6, which correlates well with the trend of the estimated ΦTσex/σ0 values (where ΦT is the triplet excited state quantum yield, and σex and σ0 are the excited-state and ground-state absorption cross-section, respectively) at 532 nm. It is revealed that substitution at the 7-position of the fluorenyl component exerts a distinct effect on the photophysics and RSA of the complexes. Aromatic substituents such as benzothiazol-2-yl and 2-thionyl cause pronounced red-shifts of the absorption bands, the emission bands, and the transient difference absorption bands, but a decrease of the RSA at 532 nm. Platinum(II) complexes bearing 2-(9,9-dihexadecyl-7-R-fluoren-2-yl)-1,10-phenanthroline ligands exhibit a long-lived, broadband-absorbing excited state and strong reverse saturable absorption (RSA) at 532 nm for ns laser pulses. The substituent at the 7-position of the fluorenyl component exerts a pronounced effect on both the photophysical properties and the RSA. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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