Intramolecular hydrogen bonds between first sphere ligands and second sphere residues are now recognized to be extremely important in controlling the chemistry of metalloenzyme active sites. We have prepared two series of ligands capable of creating intramolecular hydrogen bonding networks upon binding to transition metal centers. The first class are N3 pincer ligand containing a central 2,6-pyridinedicarboxamide unit, while the second class are N4 tripodal ligands based on the 2,2',2''-nitrilotris(N-(pyridin-2-yl)acetamide framework.  The coordination chemistry of these ligands has been explored through the preparation of numerous metal complexes with Fe, Ni or Cu centers. The resulting complexes were characterized with X-ray crystallography and electronic absorption spectroscopy. In the Cu(II) complexes, intramolecular H-bonds are formed between protonated pyridine (or pyrimidine) groups in the second sphere and first sphere ligands such as chloride, water, and/or triflate. Our results demonstrate that intramolecular H-bonds affect the structural, electronic, and electrochemical properties of the transition metal complexes.

Pincer and tripodal ligands for the formation of intramolecular hydrogen bonding networks in transition-metal complexes: Synthesis, coordination chemistry, and electronic properties

246th National Meeting (2013)

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