In a number of small molecule reductions mediated by metalloenzymes, control of proton and electron movement is of paramount importance. For instance, the addition of a proton and an electron to the nitrite ligand at a copper(II) site results in NO release in copper nitrite reductase CuNIR. Additional motivation is provided by the goal of interconverting bound N2 with its reduced forms such as N2H2, N2H4, and NH3 as achieved by nitrogenase. We will describe the synthesis of a family of tris(pyrazolyl)borate ligands pyTp that possess differently substituted pyridyl arms with the goal to engage metal-bound substrates in H-bonding as well as reduction via proton-coupled electron transfer (PCET). Synthetic routes will be described that enable tuning of H-bonding and ultimately PCET by these pyTp ligands through modification of the pyridyl groups. We will illustrate the binding preferences of this family of pyTp ligands through the synthesis of a variety of copper complexes. Interactions with the pyridyl arm range from strained metal coordination to H-bonding interactions with copper-bound functionalities. We also examine the reduction potential of corresponding copper(II) complexes as a function of the electronic properties of the pyTp ligand, necessary for a detailed investigation of ligand based reduction in pyTpCu-X species (X = NO2-, N2).

Copper complexes featuring tris(pyrazolyl)borate ligands that mediate H-bonding interactions with bound functionalities

254th National Meeting (2017)

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