ic5017214_si_001.pdf (6.78 MB)
Donor–Acceptor Ligand-to-Ligand Charge-Transfer Coordination Complexes of Nickel(II)
journal contribution
posted on 2014-08-18, 00:00 authored by Wesley
W. Kramer, Lindsay A. Cameron, Ryan A. Zarkesh, Joseph W. Ziller, Alan F. HeydukA family
of charge-transfer chromophores comprising square-planar nickel(II)
complexes with one catecholate donor ligand and one α-diimine
acceptor ligand is reported. The nine new chromophores were prepared
using three different catecholate ligands and three different α-diimine
ligands. Single-crystal X-ray diffraction studies on all members of
the series confirm a catecholate donor–nickel(II)−α-diimine
acceptor electronic structure. The coplanar arrangement of donor and
acceptor ligands manifests an intense ligand-to-ligand charge-transfer
(LL′CT) absorption band that can be tuned incrementally from
650 nm (1.9 eV) to 1370 nm (0.9 eV). Electrochemical studies of all
nine complexes reveal rich redox chemistry with two one-electron reduction
processes and two one-electron oxidation processes. For one dye, both
the singly reduced anion and the singly oxidized cation were prepared,
isolated, and characterized by EPR spectroscopy to confirm ligand-localization
of the redox processes. The optical and electrochemical properties
of these new complexes identify them as attractive candidates for
charge-transfer photochemistry and solar-energy conversion applications.