Lead(II) 4,4′-Bipyridine N-Oxide Coordination Polymers - Highly Phosphorescent Materials with Mechanochromic Luminescence Properties

详细信息    查看全文

• 作者：Oksana Toma ; Nicolas Mercier ; Magali Allain ; Francesco Meinardi and Chiara Botta
• 刊名：European Journal of Inorganic Chemistry
• 出版年：2017
• 出版时间：January 26, 2017
• 年：2017
• 卷：2017
• 期：4
• 页码：844-850
• 全文大小：2896K
• ISSN：1099-0682c

文摘

In the Pb^IIX₂/bp4mo (4,4′-bipyridine N-oxide) system, four coordination polymers (CPs) with the formulation of [PbX₂(bp4mo)] are obtained. Compounds 1 and 2, in which X = Cl and Br, are polymorphs whose acentric structures are based on 2D CPs. On the contrary, the compound 3 (X = I) shows a close, but centrosymmetrical, structure compared with the ones of 1 and 2. Finally, the structure of compound 4, in which X = NO₃^–, is described by two-interpenetrated 3D networks. They all exhibit phosphorescence properties characterized by a broad emission band at around 600 nm, with lifetimes longer than tens of µs and quite high quantum yields that increase in the halide series from 6 % (1) to 27 % (3) and up to 34 % for 4. They also exhibit mechanochromic luminescence (MCL) properties: the grinding (g) of samples 1–4 involves nearly complete extinction of the luminescence, as well as a crystal to amorphous transition of the corresponding samples 1-g to 4-g. This phenomenon, which can be also considered a crystallization-enhanced emission process, is reversible either by heating, exposure to vapour (H₂O, acetone) or by recrystallization in a few drops of acetone; however, it is accompanied by a loss of emission intensity. These compounds represent the first examples of MCL materials based on Pb²⁺.