Mechanochromic luminescent property and anti-counterfeiting application of AIE-active cyclometalated platinum(II) complexes featuring a fused five-six-membered metallacycle. (January 2022)

• Record Type: Journal Article
• Authors: Zhang, Hua-Hong; Wu, Shui-Xing; Wang, Yu-Qi; Xie, Tai-Gai; Sun, Shi-Shu; Liu, Yan-Ling; Han, Li-Zhi; Zhang, Xiao-Peng; Shi, Zai-Feng
• Is Part Of: Dyes and pigments. Volume 197(2022)
• Publication Date: 2022-01
• Subjects: Mechanochromic luminescence -- Aggregation-induced emission -- Cyclometalated platinum(II) complexes -- Five-six-membered metallacycle; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2021.109857
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: Two couples of pinene-containing N^C*N and C*N^N-coordinated Pt(II) complexes featuring a fused five-six-membered metallacycle have been developed, and their structures were confirmed by NMR, MS and single crystal X-ray crystallography. Cyclometalated complex (−)-2 has two polymorphs involving yellow-orange form (−)-2 ·CH3 COCH3 and orange form (−)-2 ·CH3 SOCH3, revealing different conformations and intermolecular π − π interactions. Complexes (−)-1 and (−)-2 display prominent aggregation-induced emission (AIE) in THF-water solution system with emission quantum yield ( Φ em ) strengthening from 0.2% to 37%. Despite the structural similarity of complexes (−)-1 and (−)-2, different mechanochromic luminescent phenomena have been distinguished. No detectable change in color and luminescence of yellow solids (−)-1 can be found during the grinding process, whereas yellow solids of complex (−)-2 show a reversible mechanochormic luminescent behavior and a simultaneous crystal-to-amorphous transformation. It is speculated that dimeric structures containing weak π − π interactions are formed under the mechanical force, and simultaneously the molecular conformation becomes more planar, improving the conjugation, inducing the emissive state variance with more 3 MLCT/ 3 ILCT character. Moreover, anti-counterfeiting application based on complex (−)-2 has been explored. This research provides a new design strategy for exploring AIE-active Pt(II) complexes with high-contrast mechanochromic luminescence. Graphical abstract: Image 1 Highlights: Two couples of Pt(II) complexes featuring a fused five-six-membered metallacycle have been prepared. Two pseudo-polymorphs of complex (−)-2 have been obtained. All complexes exhibit prominent aggregation-induced emission (AIE). Distinct mechanochromic luminescent phenomena have been distinguished for complex (−)-2.