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Uniting Ruthenium(II) and Platinum(II) Polypyridine Centers in Heteropolymetallic Complexes Giving Strong Two-Photon Absorption

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posted on 07.12.2015, 00:00 by Pengfei Shi, Benjamin J. Coe, Sergio Sánchez, Daqi Wang, Yupeng Tian, Marcin Nyk, Marek Samoc
New trinuclear RuPt2 and heptanuclear RuPt6 complex salts are prepared by attaching PtII 2,2′:6′,2″-terpyridine (tpy) moieties to RuII 4,4′:2′,2″:4″,4‴-quaterpyridine (qpy) complexes. Characterization includes single crystal X-ray structures for both polymetallic species. The visible absorption bands are primarily due to RuII → qpy metal-to-ligand charge-transfer (MLCT) transitions, according to time-dependent density functional theory (TD-DFT) calculations. These spectra change only slightly on Pt coordination, while the orange-red emission from the complexes shows corresponding small red-shifts, accompanied by decreases in intensity. Cubic molecular nonlinear optical behavior has been assessed by using Z-scan measurements. These reveal relatively high two-photon absorption (2PA) cross sections σ2, with maximal values of 301 GM at 834 nm (RuPt2) and 523 GM at 850 nm (RuPt6) when dissolved in methanol or acetone, respectively. Attaching PtII(tpy) moieties triples or quadruples the 2PA activities when compared with the RuII-based cores.