White light emission from a green cyclometalated platinum() terpyridylphenylacetylide upon titration with Zn() and Eu( )

• Published in: Dalton transactions : an international journal of inorganic chemistry 2020-08, Vol.49 (32), p.11163-11169
• Main Authors: Qiu, Yuqing, Feng, Yuquan, Zhao, Qian, Wang, Hongwei, Guo, Yingchen, Qiu, Dongfang
• Format: Article
• Language: English
• Subjects: Absorption spectra; Banded structure; Benzene; Conjugation; Crystallography; Energy transfer; Fluorescence; Light emission; Phosphorescence; Platinum; Receptors; Sensitizing; Stoichiometry; Titration; White light; Zinc
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d0dt02336a

The cyclometalated Pt( ii ) acetylide derivative with a 1,3-bis( N -octyl-benzimidazol-2-yl)benzene (N^C^N) ligand and a free terpyridine (TPY) receptor has been successfully synthesized and characterized. X-ray crystallography shows its inefficient conjugation degree between the [(N^C^N)Pt] and TPY planes. This bifunctional complex shows an enhanced 1 MLCT/LLCT absorption band ( = 3.30 × 10 4 dm 3 mol −1 cm −1 ) centered at λ max = 365 nm, and the well-resolved vibronic-structured 3 MLCT/LLCT emission bands ( Φ = 0.08, τ = 3.43 μs) in the range of ca . 475-700 nm. Consecutive titrations show that added Zn 2+ and Eu(HFA) 3 bond to its free TPY receptor with 1 : 2 and 1 : 1 stoichiometry to form the heterotrinuclear Pt-Zn-Pt ( K a = 3.48 × 10 4 mol −1 dm 3 ) and heterodinuclear Pt-Eu ( K a = 1.73 × 10 4 mol −1 dm 3 ) complexes, respectively. A sensitizing effect of Zn 2+ on the TPY unit, and the incomplete d → f energy transfer from the [(N^C^N)Pt( ii )] antenna donor to the Eu( iii ) center with maximum efficiency of 51.8% are observed. Using an in situ mixed titration strategy, the R/G/B emission triads consisted of red [(TPY)Eu(HFA) 3 ] and green [(N^C^N)Pt( ii )] dual phosphorescence and blue [(TPY)Zn(TPY)] fluorescence, which can be well balanced to realize the white-light-emission with CIE coordinates ( x = 0.36, y = 0.36) by precisely controlling the molar ratio (9 : 1 : 2) of the parent complexes, Eu(HFA) 3 and Zn(ClO 4 ) 2 . A white-light-emission ternary system consisting of polypyridyl Eu( iii ) (red), Pt( ii ) (green) and Zn( ii ) (blue) complexes is synthesized.