Luminescent Organometallic Complexes Built upon the Nonemissive Azophenine
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- 作者：Hu Lei ; Shawkat M. Aly ; Paul-Ludovic Karsenti ; Daniel FortinPierre D. Harvey
- 刊名：Organometallics
- 出版年：2017
- 出版时间：February 13, 2017
- 年：2017
- 卷：36
- 期：3
- 页码：572-581
- 全文大小：661K
- ISSN：1520-6041
文摘
Azophenine, C6H2(═NPh)2(NHPh)2, is renowned to be nonemissive in solution or in the solid state at 298 and 77 K. It was rendered luminescent in solution at room temperature without using any cyclization strategy of the N∧N end by anchoring two or four trans-RC≡CPt(PBu3)2(C≡C) units (R = hexa-n-hexyltruxene (Tru)) on the azophenine. Complexes of the general formulas C6H2(═NC6H4C≡CSiMe3)2(NHPtTru)2 (DiPtTruQ) and C6H2(═NPtTru)2(NHPtTru)2(TertPtTruQ), where Pt = trans-C6H4C≡CPt(PBu3)2C≡C, exhibit fluorescence (420 nm) and phosphorescence (512 nm) bands arising from upper localized ππ*/C6H4C≡C to TruC≡C charge transfer singlet and triplet excited states in 2MeTHF at 298 and 77 K. This latter assignment is based on DFT computations (B3LYP). Moreover, DiPtTru and TertPtTru exhibit low-energy absorption bands with maxima in the 470–485 nm range extending all the way to 600–650 nm. These spectral features are associated with charge transfer (CT) excited states: namely, TruPt → Q (Q = C6H2N2(NH)2). No emission band (fluorescence or phosphorescence) associated with these CT states has been detected at 298 K, but weak fluorescence bands (λmax ∼750 nm) decaying on the picosecond time scale have been observed in both cases. Biexponential decays were also often noted and likely reflect the presence of the possible conformers associated with the two possible dihedral angles made by the C6H4 plane and the central C6H2N2(NH)2 core. No evidence for electron transfer between the TruPt arms and Q was observed.