Shin Homin, Liu Xiangyang, Lacelle Thomas, MacDonell Ryan J, Schuurman Michael S, Malenfant Patrick R L, Paquet Chantal
National Research Council of Canada, 100 Sussex Drive, Ottawa, ON K1A 0R6, Canada.
Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
ACS Appl Mater Interfaces. 2020 Jul 22;12(29):33039-33049. doi: 10.1021/acsami.0c08645. Epub 2020 Jul 10.
Increasing attention has been given to amine-copper formate complexes for their use as low-cost printable conductive inks. The structure of amine ligands coordinated to copper centers has been reported to dictate the properties of copper molecular inks, such as stability and printability, thereby influencing the copper reduction pathway during the thermolysis. Yet, the underlying mechanism by which formate is oxidized when complexed with amine ligands is still not fully understood. Here, we propose a mechanistic pathway of copper formate dehydrogenation and decarboxylation and examine the critical role that amine ligands play in their thermal decomposition by employing first-principles electronic structure computations and experimental analyses of thermolysis reactions. Based on the computational characterization of the relevant reaction pathways for a number of primary and secondary amines as well as pyridine ligand complexes, we are the first to show that the hydrogen bonds formed between the amine ligand and formate are the key factors governing the activation energy, providing a design principle for the synthesis of organic ligands that can tune the height of the reaction barriers of the dehydrogenation and decarboxylation reactions. The calculations, confirmed by NMR studies, show that the reduction of Cu(II) to Cu(I) occurs in concert with the release of H via the dimerization of Cu(II) hydride. This result suggests that the monomeric elimination of H is not favorable for the Cu(II) to Cu(I) reduction and thus identifies amino copper formate as an important intermediate for copper reduction whose thermodynamic stabilities are also dictated by the nature of the amine ligands.
胺 - 甲酸铜配合物作为低成本可印刷导电油墨的应用受到了越来越多的关注。据报道，与铜中心配位的胺配体的结构决定了铜分子油墨的性质，如稳定性和可印刷性，从而影响热解过程中的铜还原途径。然而，甲酸与胺配体络合时被氧化的潜在机制仍未完全理解。在此，我们提出了甲酸铜脱氢和脱羧的机理途径，并通过采用第一性原理电子结构计算和热解反应的实验分析，研究了胺配体在其热分解中所起的关键作用。基于对多种伯胺、仲胺以及吡啶配体配合物相关反应途径的计算表征，我们首次表明胺配体与甲酸之间形成的氢键是控制活化能的关键因素，为合成能够调节脱氢和脱羧反应势垒高度的有机配体提供了设计原则。经核磁共振研究证实的计算结果表明，Cu(II)还原为Cu(I)与通过氢化铜二聚体释放H同时发生。这一结果表明，H的单体消除不利于Cu(II)还原为Cu(I)，从而确定氨基甲酸铜是铜还原的重要中间体，其热力学稳定性也由胺配体的性质决定。
