Our first project focuses on the
synthesis and reactivity of bimetallic
complexes in the activation and sensing of
small molecules. A variety of bimetallic and
multimetallic centers in nature demonstrate
metal-metal cooperativity in binding,
recognition, and activation of various
substrates. Our roadmap to the cooperativity
involves careful design of dinucleating
ligand platforms which are tailored for
specific substrates and transformations.
Specific reactions of interest include
reductive coupling and splitting of
heteroallenes, reduction of dioxygen, and
selective recognition (sensing) of
dicarboxylates and sugars.
Flexible dinucleating ligand allows
formation of dinuclear complexes of Ni and
Cu. We also demonstrate that the di-Ni
complex is capable of binding two molecules
of carbon disulfide (right) and positioning
them side by side (left).
A similar system
was synthesized with oxidized Ni (right).
This system is capable of binding oxalate
between the metal centers (right). The
system is selective for oxalate versus other
mono- and di-carboxylates. Oxalate
coordination is reversed by addition of CaBr2,
making it a recyclable oxalate sensor.
A more rigid
xanthene-based bis(iminopyridine) ligand
forms a di-copper(I) complex. Its reaction
with O2 leads to the isolation of
tetranuclear copper(II) cluster with
bridging hydroxides, as one of the
products (full structure given left). With
CO2, a
tetranuclear mu-carbonate cluster is
isolated (the structure with t-Bu groups
is given right).
