Mondal Bijnaneswar, Bhandari Pallab, Mukherjee Partha Sarathi
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560012, India.
Chemistry. 2020 Nov 20;26(65):15007-15015. doi: 10.1002/chem.202003390. Epub 2020 Oct 15.
Coordination-driven self-assembly of discrete molecular architectures of diverse shapes and sizes has been well studied in the last three decades. Use of dynamic imine bonds for designing analogous metal-free architectures has become a growing challenge recently. This article reports an organic molecular barrel (OB4 ) as a potential template for nucleation and stabilization of very tiny (<1.5 nm) Ag nanoparticles (AgNPs). Imine bond condensation of a rigid tetra-aldehyde with a flexible diamine followed by imine-bond reduction yielded the discrete tetragonal organic barrel (OB4 ). The presence of a molecular pocket ornamented with eight diamine moieties gives the potential for encapsulation of silver(I). The organic barrel was finally used as a molecular vessel for the controlled nucleation of silver nanoparticles (AgNPs) with fine size tuning through binding of Ag ions in the confined space of the barrel followed by reduction. Transmission electron microscopy (TEM) analysis of the Ag @OB4 composite revealed that the mean particle size is 1.44±0.16 nm. The composite material has approximately 52 wt % silver loading. The barrel-supported ultrafine AgNPs [Ag @OB4 ] are found to be an efficient photocatalyst for facile Ullmann-type aryl-amination coupling of haloarenes at ambient temperature without using any additives. The catalyst was stable for several cycles of reuse without any agglomeration. The new composite Ag @OB4 represents the first example of discrete organic barrel-supported AgNPs employed as a photocatalyst in Ullmann-type coupling reactions at room temperature.
在过去三十年中，对不同形状和尺寸的离散分子结构的配位驱动自组装进行了深入研究。最近，利用动态亚胺键设计类似的无金属结构已成为一项日益严峻的挑战。本文报道了一种有机分子桶（OB4），它可作为极微小（<1.5 nm）银纳米颗粒（AgNPs）成核和稳定化的潜在模板。刚性四醛与柔性二胺的亚胺键缩合，随后进行亚胺键还原，得到了离散的四方有机分子桶（OB4）。带有八个二胺部分的分子口袋的存在为封装银（I）提供了可能性。最终，该有机分子桶被用作分子容器，通过在桶的受限空间内结合银离子然后还原，实现对银纳米颗粒（AgNPs）的可控成核并进行精细的尺寸调节。对Ag@OB4复合材料的透射电子显微镜（TEM）分析表明，平均粒径为1.44±0.16 nm。该复合材料的银负载量约为52 wt%。发现桶负载的超细AgNPs [Ag@OB4]是一种高效的光催化剂，可在室温下实现卤代芳烃的简便乌尔曼型芳基胺化偶联反应，且无需使用任何添加剂。该催化剂在几个循环的重复使用中保持稳定，没有任何团聚现象。新型复合材料Ag@OB4代表了在室温下用于乌尔曼型偶联反应的离散有机分子桶负载AgNPs作为光催化剂的首个实例。
