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In-Depth Information
thermodynamics of dioxygen binding to
were also studied by
stopped-flow techniques; rapid dioxygen binding occurs
(183
K), with
(183 K) , a n d
53,54
The first x-ray crystallographic description for a copper-dioxygen
adduct, synthetic or protein, came with our characterization of the 2:1 adduct
(
1
), with
or
counter-anions,
formed by
reversible oxygenation of copper(I) precursor complex
(
1a
, R = Me, Et, TMPA = tris[2-pyridylmethyl]amine) (Chart 2).
55,56
The
dication
1
is best described as a peroxo-dicopper(II) species.
It is essentially
diamagnetic, possessing a moiety with
and O-O = 1.432 Å. Other relevant physical properties are
(resonance Raman), and UV-vis (i.e., peroxo-to-Cu(II) LMCT) bands at
440 nm
(11,500), ~ 600 nm (sh, ~ 7600)
and a d-d band at 1035 nm (180).
57
Kinetics studies
54,58
reveal that
(
1a
) reacts with
to give a transient
(at -80°C,
410 nm) 1:1 superoxo-copper(II) adduct,
(
1b
), with
suggested end-on coordination (Chart 1). The full kinetics and
thermodynamics of these reactions, and those with complexes with ligands
TMPAE, BPQA, BQPA, plus binucleating analogues D1 and DO (Chart 3),
have been elucidated and described.
54,58-60
We have shown that ligand DO
confers room temperature stability to the resulting dioxygen adduct
Reedijk and co-workers
61
have also been able to obtain
similar room-temperature stability for a adduct with a macrocyclic
binucleating ligand, which possesses pyrazolyl and alkylamine donors. The
60
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