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Download fileMechanistic Insight into Bis(amino) Copper Formate Thermochemistry for Conductive Molecular Ink Design
journal contribution
posted on 2020-07-10, 14:39 authored by Homin Shin, Xiangyang Liu, Thomas Lacelle, Ryan J. MacDonell, Michael S. Schuurman, Patrick R. L. Malenfant, Chantal PaquetIncreasing
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
H2 via the dimerization of Cu(II) hydride. This result
suggests that the monomeric elimination of H2 is not favorable
for the Cu(II) to Cu(I) reduction and thus identifies dimeric amino copper formate as an important intermediate for copper reduction
whose thermodynamic stabilities are also dictated by the nature of
the amine ligands.