ESR spectra of low-symmetry high-spin cobalt(II) complexes. 7. Trigonal-bipyramidal pentakis(picoline N-oxide)cobalt(II) perchlorate
Descrição do Produto
Journal of Molecuh 0 EkevlerSclentific
ESR
SPECTRA
OF LOW-SYMXETRY
HIGH-SPIN
mTbe
COBALT(I1)
tetra-n-butylammonium 2 tensor oE the A
and the calculation
A. BENCINI,
C. BENELLI,
50132 Florence,
tribromo(quinoline)
cobaltate
and C. ZANCHINI
D. GATTESCHI,
Lab. CNR and Istituto di Chimica
Netherlands
COMPLEXES
Pseudotetrahedral
Sk.
Part
401
Structure, 60 (1980) 401-404 Publishing Company, Amsterdam--Printed
Generale,
LJniversit5
di Firenze,
via
Nardi
39,
Italy.
ABSTRACT X-ray
structure
a symmetry crystal angle
near
dependent
are
with
Ligand
the cobalt
the
to C3,
spectra oE ~20~
[N(?z-C4Hq)4][CoBr3(q
OF
Co-N
largely Co-N.
Field
hyperfine
bond
direction
anisotropic:
These
results The
Model.
coupling
being
g1=6.31. are
the complex
the pseudo
Cg axis.
gS=1.61.
interpreted
of
is also
that
g2=2.33,
easily
application
constant
shows
uinoline)l
the model
gj
using
possesses
The
single
makes
an
a symmetry
ip
to the calculation
of
shown.
INTRODUCTION In the
last
attracted
the interest
the complexes Ligand
Field
their
few years
play
compounds
Model
the
had
been
to include
We wish
high
to report
tools
that
in determining
the
Field
spin
as simple
cobalt(I1)
complexes
have
the characterization
feature
of
components
of
the spectra,
oE the
making
a way
by Cerloch et aZ.
of low symmetry to
the
that
they More
the A tensor
and
(ref.
of
1,7,8).
effective
The
investigat -
enough symmetry
possessed recently
for the
transition metal corn -
interpretation
complexes
as possible. of
for
low symmetry
Model, developed applied
in such
cobalt(I1)
(ref.4,5).
susceptibility
the calculation (ref.
as
spin
clear
successfully
chosen
interpretation
published
role
of the magnetic
of low symmetry
become
Ligand
(ref. 61, has been
g values
of high
straightforward
independent
interpretation
been
not
spectra
researchers,
It has
a major
interpretation
plexes
keep
of many
(ref.2,3).
A symmetry
ed
the ESR
we
the relevant
have
extended
equations
to the
has
9).
here the application
single crystal spectra oE the triclinic
of the Model
to the interpretation
[N(n-CqHq)4][CoBr3(quinoline)]
the Zn analogue, which we reported previously
of the
doped into
(ref. lo), but we were unable
to
justify on the basis of the nature of the ground level of the complex. Further we want
to report some examples
of the cobalt hyperfine * For
Part
4 see
reE.1.
of application
coupling constant,
of the new Eormalism
for the calculation
in order to check its ability
to justify
402 the experimental
RESULTS
AND
The
DISCUSSION
single
Zn analogue spin
A values.
crystal
have
been
Hamiltonian
Although crystal
(reE.
(ref.
LL),
and
of C;, symmetry.
principal
to the Co-N
reflecting symmetry)
In
spectra
and
low
are
directions
are
oE
a S=$
effective
Ear
fact
CS asis),
syrmnetry of
and the single 3 interpreted with this
successfully anisotropic
those
direction,
an angle
the chromophore
to c
(g1=6.31,g2=2.33,g3=
from
distant
the gS
makes
is near
anticipated
which
oE s23"
is
with
on
the
the nearest
it,
clearly
(C7 crystallographic
site
-
opinion
Model are
these
previously
used
data
can be
described
justified
(ref.
coordinates
In order
to keep
the number
of parameters
constant
5 and
the orbital
to the Eree ion value r anisotropy
the quinoline
of
plane
reduction -1
('533 cm
and
using
this
k are
the
model
the bonding
to a minimum
factor
ligand
the projection
considered
oE
can
be estimated
the Co-BrL
varied.
and
5 is
12) so
other
over
a wide
1 the results
OF some
the angle
from
(ref.
This angle LS found to be N that ctc/z r;'W.O6 The is espected.
from
direction
data
are
are
coupling
isotropic
bond -14"
the z7 values
Ligand
crystallographic
parameters
the spin-orbit
to L (x axis).
In Figure
the X-ray
eX
orthogonal
range.
low symmetry
>.
the quinoline
and
only
7). With
geometrical
The
been
highly
as
kept
using
interpreted
the chromophore have
spectra
(pseudo
the actual
our
FieLd data
g
of
As a matter
bond
doped into the
[N(~~-C~H9)~][CoBr3(quinoline)]
reported
symmetry
the ESR
1.61)
of
10).
electronic
basis one
the
spectra
previously
the idealized
polarized
symmetry
ESR
the X-ray
parameters
representative
between
in the plane structural
were
varied
calculation
oE
shown.
6 5 9 4 3
2 1
Fig.
1. The
calculated
g values
Ear
IN(tz-But)q[[CoBr3quinl.
From
efEect of changing the indicated parameter, the other ones are: -1 Br BrcO 3 eN ._, rsloz =0.2, .z~~a/e~~=O.O, k-0.9,5 =533 cm-'. cm ,c TT /en
left
to right
Dq "=750,
the
DqN=900
403 10DqL=3e~+Z(e~s+e~c ). Good agreement
In Figure 1 we have defined transitions 750-850 Field
was
cm?;
calculations
insensitive of
found
e;s/eI
ratios
The
and
of e
ligands
-O.-O.4
g tensor
well and
(ref.
with
the electronic 0. -0.1.
N /ez and the era
in good
agreement
efr/eF with
the other
A values
onesto are
less
than
cm-L ). This
which
fit well
the observed
rationalizes
the electronic -1 ; DqR',
previous
Ligand
more
and
other
are
marked
suggests
findings
quite
dependence the
for
use of
pyridine,
L,L2).
[N(n-C4Hg)4][CoBr3(quinoline)]
the values
cm
transitions
The
have
no
shown
so
=9e9pBuNc
with
DqN=900-1000
in accord
in the range
!&a is on
O--0.2)
; k=0.85-0.90;
that a fitting of the A values cannot be made. -3 contact term constant, r B and K , the isotropic
structure
Table
of
The
directions
halogen
cm
+efr-
11).
the range
spectra
(0.0254
(ref.
and
(in
pyrazole,
B=730-750
to a variation
the g values
low
for
=O.-0.3;
-1
the g values
linewidths,
the
fact
even
that
resolved
Nevertheless
P at the
the hyperfine
l),
fixing
the calculated
free
coupling
P
using
as parameters,
(see Table
with
hyperfine
ion
was
value
not
observed.
1
Representative
of g and A values
fittings
for some
high
spin
cobalt(I.1)
complexes
C omplex
[N(n-But4)] [(Zn,Co)Br3quin]b
talc. obs.
6.46 6.31
2.35 2.33
1.65 1.61
~60 39
CL5 0.1
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