Scheme 1. Synthetic Route and Cartoon Representation of Double-Metallacycle 1
紧接着,作者通过31P{1H}和1H NMR光谱对反应产物进行了表征(Fig.1),结果表明形成了一个单一的、离散的、具有高对称性的复合物。为了进一步确定该反应产物的结构,作者又通过单晶X射线衍射分析其固态结构(Fig.2),发现结果与溶液中的结构表征一致。有趣的是,在1的结构中并没有观察到明显的分子内氢键和Π-Π堆积相互作用,而是通过这些单独的双金属环与分子间的CH-··O氢键结合在一起,形成了无限双金属环链(如Fig.2b所示)。这些C-H---O和C-H---π相互作用共同稳定了一维双金属环链。Figure 1. 31P{1H} NMR spectra (acetone-d6, 121.4 MHz) of building block 4 (a) and double-metallacycle 1 (b). Partial 1H NMR spectrum (acetone-d6, 500 MHz) of 1 (c). Experimental (red, e) and calculated (blue, d) ESI-TOF-MS of 1 (m/z = 1430.85, [M – 2OTf –]2+).
Figure 2. (a) X-ray single-crystal structure of 1. Hydrogen atoms and two acetone solvent molecules are omitted for clarity. (b) Infinite double-metallacycle chain linked by intermolecular C–H···O hydrogen bonds and C–H···π interactions.
Figure 3. (a) Infinite 2-D hydrogen-bonding framework consisting of alternating double-metallacycle chains and triflate anions in the crystal structure of 1. (b–e) Coordination geometry of the crystallographically independent triflate anions showing the different C–H···O and C–H···F multiple hydrogen-bonding modes.
Figure 4. Fluorescence emission spectra (a) and plots of maximum emission intensity and wavelength (b) of 1 versus hexane fraction in acetone/hexane mixtures (λex = 380 nm, c = 10.0 μM). (c) Emission of 1 (10.0 μM) in acetone/hexane mixtures with different fractions of hexane under ultraviolet light (365 nm) at 298 K.
Figure 5. Fluorescence emission spectra (a), CIE chromaticity coordinates (b) of 1 in different solvents (λex = 380 nm, c = 10.0 μM), and emission of 1 (10.0 μM) under UV light (365 nm) in different solvents (c).
Figure 6. (a) Solid fluorescence emission spectra of the building block 2 and platinum complex 1 (λex = 380 nm). Solid emission of 2 (b) and 1 (c) under a 365 nm UV lamp.