Achieving NIR emission for tetradentate platinum (II) salophen complexes by attaching dual donor-accepter frameworks in the heads of salophen. (March 2017) - Zhang, Youming
Abstract: Two novel tetradentate platinum (II) salophen complexes A and B, respectively substituted by dual donor-accepter frameworks of phenazine-triphenylamine in the heads and waists of salophen, were synthesized and characterized. By changing the substituted positions of dual phenazine-triphenylamine units, different optophysical, electrochemical and electroluminescent properties were remarkably observed for the both platinum (II) salophen complexes. Using a blend of poly(vinyl-carbazole) (PVK) and 1, 3-bis(5-(4-( tert -butyl) phenyl)-1, 3, 4-oxadiazol-2-yl)benzene (OXD-7) as host matrix, the platinum (II) salophen complexes A and B exhibited a deep red emission at 653 nm and a near-infrared (NIR) emission at 695 nm in the single-emissive-layer polymer light-emitting devices, respectively. The maximum external quantum efficiency ( EQE ) of 1.36% and highest radiant intensity ( R ) of 45 μ W cm −2 were obtained in the complex B-doped devices, which are 13.6 and 2.6 times of those corresponding values in the complex A-doped devices. It indicates that appending dual donor-accepter frameworks in the heads of salophen is an efficient strategy to achieve NIR emission for their tetradentate platinum (II) complexes. Graphical abstract: Two novel tetradentate platinum (II) salophen complexes A and B appending dual donor (D)-accepter (A) frameworks were synthesized and characterized. Using both platinum (II) complexes as a single dopant and a blend of PVK and OXD-7 as host matrix, the made polymer light-emitting devices exhibited a deep red emission at 651 nm with an external quantum efficiency ( EQE ) of 0.1% and radiant ( R ) intensity of 17 μ W cm −2 for the complex A, but a near-infrared emission at 695 nm with a EQE of 1.36% and a R of 45 μ W cm −2 for the complex B. It demonstrates that appending the dual D-A chains into the 1, 4-phenylene head of the salophen can significantly improve electroluminescent properties for their Pt (II) complexes. Highlights: Two novel tetradentate platinum (II) salophen complexes A and B were synthesized and characterized. Different properties were observed by changing the substituted positions of dual D-A units. The EQE of 1.36% and R of 45 μ W cm −2 were obtained in the complex B doped devices. EQE and R values of B-doped devices are 13.6 and 2.6 times of A-doped devices.