The preparation,
structures, and electrochemical and magnetic properties
supported by density functional theory (DFT) calculations of three
new copper(II) compounds with [1,2,5]thiadiazolo[3,4-
f
][1,10]phenanthroline 1,1-dioxide (td)
and its radical anion (td
·–
) are reported:
{[Cu
II
Cl(td)](μ-Cl)
2
[Cu
II
Cl(td)]} (
1
), which incorporates only neutral
td ligands; [Cu
II
Cl(td
·–
)(td)]·2MeCN
(
2
), which comprises one neutral td and one radical td
·–
; and PPN[Cu
II
Cl(td
·–
)
2
]·2DMA (
3
), where Cu
II
ions
are coordinated by two radical anions td
·–
(DMA,
dimethylacetamide; PPN
+
, the bis(triphenylphosphine)iminium
cation). All three compounds show interesting paramagnetic behavior
with low-temperature features indicating significant antiferromagnetic
coupling. The magnetic properties of
1
are dominated
by Cu
II
···Cu
II
interactions (
J
CuCu
) mediated through the Cl
–
bridges, while the magnetic properties of
2
and
3
are governed mainly by the td
·–
···td
·–
(
J
tdtd
) and Cu
II
–td
·–
(
J
Cutd
) exchange interactions. The structure of
2
features only two major magnetic coupling pathways enabling the
fitting of experimental data with
J
tdtd
= −36.0(5) cm
–1
and
J
Cutd
= −12.6(2) cm
–1
only. Compound
3
exhibits a complex network of magnetic contacts. Attempt
to approximate its magnetic behavior using only a local magnetic contacts
model resulted in
J
tdtd
= −5.6(1)
cm
–1
and two
J
Cutd
constants,
−12.4(2) and −22.6(4) cm
–1
. The experimental
fitting is critically compared with the results of broken symmetry
density functional theory (BS DFT) calculations for inter- and intramolecular
contacts. More consistent results were obtained with the M06 functional
as opposed to popular B3LYP, which encountered problems reproducing
some of the experimental intermolecular exchange interactions. Electrochemical
measurements of
2
and
3
in MeCN showed three
reversible nearly overlapping redox peaks appearing in a narrow potential
range of −600 to −100 mV vs Fc/Fc
...