文摘
Azophenine, C<sub>6sub>H<sub>2sub>(═NPh)<sub>2sub>(NHPh)<sub>2sub>, 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<sup>∧sup>N end by anchoring two or four trans-RC≡CPt(PBu<sub>3sub>)<sub>2sub>(C≡C) units (R = hexa-n-hexyltruxene (Tru)) on the azophenine. Complexes of the general formulas C<sub>6sub>H<sub>2sub>(═NC<sub>6sub>H<sub>4sub>C≡CSiMe<sub>3sub>)<sub>2sub>(NHPtTru)<sub>2sub> (DiPtTruQ) and C<sub>6sub>H<sub>2sub>(═NPtTru)<sub>2sub>(NHPtTru)<sub>2sub>(TertPtTruQ), where Pt = trans-C<sub>6sub>H<sub>4sub>C≡CPt(PBu<sub>3sub>)<sub>2sub>C≡C, exhibit fluorescence (420 nm) and phosphorescence (512 nm) bands arising from upper localized ππ*/C<sub>6sub>H<sub>4sub>C≡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 = C<sub>6sub>H<sub>2sub>N<sub>2sub>(NH)<sub>2sub>). No emission band (fluorescence or phosphorescence) associated with these CT states has been detected at 298 K, but weak fluorescence bands (λ<sub>maxsub> ∼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 C<sub>6sub>H<sub>4sub> plane and the central C<sub>6sub>H<sub>2sub>N<sub>2sub>(NH)<sub>2sub> core. No evidence for electron transfer between the TruPt arms and Q was observed.