Synthesis, crystal structure, magnetic and electrochemical studies of two copper complexes with carboxylate rich dinucleating ligand

Article abstract of DOI:10.1016/j.ica.2012.08.013

Three new copper compounds of a symmetric dinucleating ligand, N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[carboxymethyl]-1, 3-diaminopropan-2-ol (H₅ccdp) with diverse coordinating groups, have been synthesized and studied in the solid state as well as in solution. In acetonitrile/H₂O solution, the reaction of stoichiometric amounts of Cu(NO₃)₂·2.5H₂O and the ligand H ₅ccdp, in the presence of K₂CO₃, produced a dinuclear copper compound, K₃[Cu₂(ccdp)(μ-CO ₃)]·7H₂O·C₃H₆O, K ₃[1]·7H₂O·C₃H₆O. Whereas in an alkaline methanol/water solution, the reaction of Cu(ClO ₄)₂·6H₂O and the ligand H ₅ccdp gave a slightly different dinuclear copper compound, Na ₃[Cu₂(ccdp)(μ-CO₃)]·5H₂O, Na₃[1]·5H₂O. The reaction of Cu(ClO ₄)₂·6H₂O and the ligand H ₅ccdp, in the presence of NaOH in water yielded a tetranuclear copper compound, Na₂[Cu₂(ccdp)(H₂O)(μ-OH ₂)]₂·15H₂O, Na₂[2] ·15H₂O. The structures of the all three complexes were determined using single crystal X-ray diffraction analyses. Variable-temperature magnetic susceptibility studies on the powder samples of the complexes showed antiferromagnetic behavior. Electrochemical studies in aqueous solutions of these negatively charged complex ions showed fairly assessable oxidations.

Full text of DOI:10.1016/j.ica.2012.08.013

Inorganica Chimica Acta 394 (2013) 220–228
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, crystal structure, magnetic and electrochemical studies of two
copper complexes with carboxylate rich dinucleating ligand
⇑
Rebecca A. Joy, Hadi Arman, Shengchang Xiang, Ghezai T. Musie
Department of Chemistry, The University of Texas at San Antonio, San Antonio, TX 78249, United States
a r t i c l e i n f o
a b s t r a c t
Three new copper compounds of a symmetric dinucleating ligand, N,N0-bis[2-carboxybenzomethyl]-N,N0-
bis[carboxymethyl]-1,3-diaminopropan-2-ol (H5ccdp) with diverse coordinating groups, have been syn-
thesized and studied in the solid state as well as in solution. In acetonitrile/H2O solution, the reaction of
stoichiometric amounts of Cu(NO3)2ꢀ2.5H2O and the ligand H5ccdp, in the presence of K2CO3, produced a
Article history:
Received 23 April 2012
Received in revised form 27 June 2012
Accepted 11 August 2012
Available online 3 September 2012
dinuclear copper compound, K3[Cu2(ccdp)(
l
-CO3)]ꢀ7H2OꢀC3H6O, K3[1]ꢀ7H2OꢀC3H6O. Whereas in an alka-
line methanol/water solution, the reaction of Cu(ClO4)2ꢀ6H2O and the ligand H5ccdp gave a slightly dif-
ferent dinuclear copper compound, Na3[Cu2(ccdp)(
-CO3)]ꢀ5H2O, Na3[1]ꢀ5H2O. The reaction of
Cu(ClO4)2ꢀ6H2O and the ligand H5ccdp, in the presence of NaOH in water yielded a tetranuclear copper
compound, Na2[Cu2(ccdp)(H2O)(
Keywords:
l
Copper complexes
Polynuclear complexes
Dinucleating ligands
Magnetic properties
Electrochemistry
l
-OH2)]2ꢀ15H2O, Na2[2]ꢀ15H2O. The structures of the all three complexes
were determined using single crystal X-ray diffraction analyses. Variable-temperature magnetic suscep-
tibility studies on the powder samples of the complexes showed antiferromagnetic behavior. Electro-
chemical studies in aqueous solutions of these negatively charged complex ions showed fairly
assessable oxidations.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
several classes of metalloenzymes including oxidases (catechol
oxidase) [8], oxygenases [9], nucleases [10], and phosphatases
Transition metal complexes containing two or more metal ions
have gained significant interest over the years due to their diverse
properties and reactivity, originating from the magnetic exchange
occurring between neighboring metal centers and potential appli-
cations in the field of magnetism [1], in catalysis [2], and as struc-
tural and functional models of metalloenzymes [3]. Polynuclear
systems are ubiquitous in nature, especially in metalloenzymes
[4]. The active sites of many of these metal-containing enzymes
possess oxygen- and nitrogen-rich donating environments. So far,
several copper ions coordinated to oxygen and/or nitrogen atoms
as structural and functional models metalloenzymes are reported
in the literature [5]. However, when compared to N- and other
O- donating groups, there are very few complexes with polycar-
boxylate ligand systems reported in the literature [6].
Copper is the third most abundant transition metal found in liv-
ing systems [4c], and it plays an essential role in biological sys-
tems. Copper is incorporated in metalloenzymes that are
involved mainly in oxygen transport, electron transfer, and cata-
lytic oxidation processes [7]. Synthetic coordination complexes
employing copper(II) have proven effective functional models for
[8b,11].
The symmetrical bridging ligand N,N0-bis-[2-carboxybenzom-
ethyl]-N,N0-bis[carboxymethyl]-1,3-diaminopropan-2-ol (H5ccdp)
[12] is used to create three interesting copper compounds exhibit-
ing diverse coordination chemistry. The compounds are either
dinuclear, K3[1]ꢀ7H2OꢀC3H6O and Na3[1]ꢀ5H2O, or tetranuclear,
Na2[2]ꢀ15H2O, in copper. The ligand, shown in Scheme 1, has two
symmetrical tetradentate cavities, each with a NO3 coordination
site able to coordinate a Cu(II) ion. This leaves the copper centers
coordinatively unsaturated, and thus room for further coordination
by exogenous ligands. This is advantageous in terms of available
binding sites for substrates in modeling metalloenzymes. In this
paper we wish to report the syntheses, structural, magnetic and
electrochemical characterizations of these new multi-copper
compounds.
2. Experimental
2.1. Materials and methods
All starting materials were purchased from commercial sources
and were used without further purification. Elemental analysis was
determined by Galbraith Laboratories, Inc., Knoxville, TN.
⇑
Corresponding author. Tel.: +1 (210) 4585454; fax: +1 (210) 4587428.
E-mail address: ghezai.musie@utsa.edu (G.T. Musie).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.08.013

R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
221
Scheme 1. Schematic representation of the synthesis of N,N0-bis[2-carboxybenzomethyl]-N,N0-bis[carboxymethyl]-1,3-diaminopropan-2-ol, H5ccdp.
Caution: Although no problems were encountered in this work,
perchlorate salts of metal complexes are potentially explosive and
should be handled in small quantities with great care.
collection and unit cell refinement were performed using CRYSTAL
CLEAR software. The total number of data were measured in the
range 2.20° < h < 27.5° using scans. Data processing and absorp-
x
tion correction, giving minimum and maximum transmission fac-
tors, were accomplished with CRYSTAL CLEAR and ABSCOR [14],
respectively. The structure, using SHELXL-97, was solved by direct
methods and refined (on F2) using full-matrix, least-squares tech-
niques [15,16]. All non-hydrogen atoms were refined with aniso-
tropic displacement parameters. All carbon bound hydrogen
atom positions were determined by geometry and refined by a rid-
ing model. Electron density peaks were used to identify oxygen
bound hydrogen atoms and the displacement parameters were
set to 1.5 times the displacement parameters of the bonded atoms.
2.2. Synthesis of metal complexes
2.2.1. Synthesis of K3[1]ꢀ7H2OꢀC3H6O
An acetonitrile–H2O solvent mixture (4:1 by vol) (5 ml) with
Cu(NO3)2ꢀ2.5H2O (0.1965 g, 0.845 mmol) was slowly added drop
wise, at ambient temperature, to a stirring 10 ml acetonitrile–
H2O (4:1 by vol) solution of the ligand H5ccdp (0.200 g,
0.422 mmol) and K2CO3 (0.2512 g, 2.53 mmol) in a period of
15 min. After complete addition, a layer of blue was seen separat-
ing in solution. The whole reaction mixture was stirred overnight
at room temperature. The solution was filtered using gravity filtra-
tion and was setup for crystallization. The X-ray quality single
crystals were grown by slow acetone or THF diffusion into the ace-
tonitrile–H2O solution of the complex. Yield: 0.1724 g (43%). Anal.
Calc. for C24H39Cu2N2K3O21: C, 30.28; H, 4.2; N, 2.99. Found: C,
2.3.2. Electrochemical analysis
Electrochemical measurements were made on a BAS-CV50
electroanalyzer controlled with a Pentium III computer and utiliz-
ing three electrodes: a glassy carbon or platinum working elec-
trode, a platinum wire counter electrode, and a Vycor-tipped Ag/
AgNO3 reference electrode. Working electrodes were polished to
a mirror finish on a microcloth of diamond or alumina (1.0 and
0.05 mm particles, respectively) and were cleaned electrochemi-
cally. Cyclic voltammograms were obtained from a 1 to 2.5 mM
analyte concentration in H2O, using 0.2 M KCl supporting electro-
lyte. Data were analyzed using the software provided with this
instrumentation. Solutions were degassed with a purge of N2 for
10 min, and a blanket of N2 was maintained over the solution while
making the measurements. The iR compensation between the
working and reference electrodes was accomplished by applying
the positive feedback from the BAS-CV50 current follower. All
potentials were measured at room temperature and scaled to
NHE using methyl viologen as an internal standard (MV2+/MV+ lit-
erature value is E1/2NHE = ꢁ0.45 V versus NHE in water) [17].
29.81; H, 3.28; N, 3.38%. UV–Vis (H2O) kmax/nm (e
/L molꢁ1 cmꢁ1):
768 (160).
2.2.2. Synthesis of Na3[1]ꢀ5H2O
This compound was prepared in a similar manner to complex 1
but methanol and NaOH were used in places of acetonitrile and
K2CO3, respectively. The X-ray quality single crystals were grown
by slow acetone–H2O (6:1 by vol) diffusion into the methanoic
solution of the complex. Yield: 0.1633 g (47%). Anal. Calc. for C24-
H51Cu2N2Na3O27: C, 28.94; H, 5.16; N, 2.81. Found: C, 28.02; H,
5.19; N, 2.73%. UV–Vis (H2O) kmax/nm (
e
/L molꢁ1 cmꢁ1): 756 (143).
2.2.3. Synthesis of Na2[2]ꢀ15H2O
A water solution (3 ml) of Cu(ClO4)2ꢀ6H2O (0.313 g, 0.845 mmol)
was slowly added drop wise, at ambient temperature, to a stirring
8 ml water solution of the ligand H5ccdp (0.200 g, 0.422 mmol)
and NaOH (0.1014 g, 2.54 mmol) in a period of 15 min. After com-
plete addition, a blue solution was obtained. The whole reaction
mixture was stirred overnight at room temperature. The solution
was filtered using gravity filtration and was setup for crystalliza-
tion. The X-ray quality single crystals were grown by slow acetone
or THF diffusion into the H2O solution of the complex. Yield:
0.3465 g (53%). Anal. Calc. for C46H76Cu4N4Na2O35: C, 35.74; H,
2.3.3. Magnetic measurement
Magnetic measurements were carried out on polycrystalline
powder samples ranging from 2 to 300 K at the applied fields of
5 kOe using a SQUID based sample magnetometer on a QUANTUM
Design Model PPMS instrument.
3. Results and discussion
4.96; N, 3.63. Found: C, 35.01; H, 4.78; N, 3.36%. UV–Vis (H2O) kmax
/
3.1. Syntheses
nm (
e
/L molꢁ1 cmꢁ1): 766 (339).
The reaction of Cu(NO3)2 salt with the ligand, H5ccdp, in 2:1 M
ratio in presence of a mild base, such as K2CO3, at pH ꢂ8 in an ace-
tonitrile/H2O solution under ambient conditions overnight affor-
ded a dark blue solution, that was easily crystallized into a blue
dinuclear copper compound K3[1]ꢀ7H2OꢀC3H6O. Similarly, reaction
of Cu(ClO4)2 salt with the H5ccdp ligand in 2:1 M ratio in presence
2.3. Physico-chemical measurements
2.3.1. X-ray crystallography and data analysis
The data were collected at 98(2) K using a Rigaku AFC12/Saturn
724 CCD fitted with Mo K radiation (k = 0.71073 Å) [13]. Data
a

222
R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
of a strong base, such as NaOH, at pH ꢂ10 afforded a blue dinuclear
copper compound, Na3[1]ꢀ5H2O, and a blue tetranuclear copper
compound, Na2[2]ꢀ15H2O, in a methanol/H2O solution and in
water, respectively. The syntheses of the ligand H5ccdp and the
respective metal complexes are depicted in Scheme 1 and Fig. 1,
respectively. Molecular structures of the three compounds have
been established using single crystal X-ray crystallography.
carbonato ligand oxygens, O(10) and O(11), are bridging the two
copper ions in a syn–syn coordination mode. The main distortion
of the resulting octahedral coordination sphere originates in
the large bite angles for N(1)–Cu(1)–O(10) = 166.74(7)° and
O(5)–Cu(2)–O(8) = 169.28(6)°, as well as, in the small bite angles
for N(1)–Cu(1)–O(3) = 82.54(6)°, O(5)–Cu(1)–N(1) = 85.10(7)°,
O(10)–Cu(1)–O(3) = 110.72(6)°,
O(5)–Cu(2)–N(2) = 85.76(7)°,
O(5)–Cu(2)–O(6) = 97.70(6)°, O(11)–Cu(2)–O(6) = 101.25(7)° and
N(2)–Cu(2)–O(6) = 81.06(6)° of the complex. Furthermore, the
Cuꢀ ꢀ ꢀCu distance measures 3.4699(4) Å, which is in agreement
with previously reported dinuclear copper(II) complexes [18,19],
and falls well within the range of metalꢀ ꢀ ꢀmetal distances ob-
served in several metallohydrolases [20,21]. The aliphatic carbox-
ylate oxygens, O(3) and O(6), coordinated to each copper ion
exhibit significantly longer bond lengths compared to the average
copper–oxygen bond length. The Cu(1)–O(3) distance of
2.1898(15) Å and the Cu(2)–O(6) distance of 2.2371(15) Å are
markedly longer than the average Cu–O distances (2.0104(30) Å
for Cu(1) and 2.0112(31) Å for Cu(2)). The bond distances and
bond angles for 1 are reported in Table 2 and are consistent with
values reported in the literature [22].
3.2. Crystal and molecular structures
The solid-state structures were confirmed by their single crystal
X-ray diffraction studies. The K3[1]ꢀ7H2OꢀC3H6O compound crystal-
lizes in a triclinic system, and according to the observed systematic
ꢀ
extinction, the structure was solved as P1 space group. Compound
Na3[1]ꢀ5H2O crystallizes in a monoclinic system, and the structure
was solved in the P21/c space group. The Na2[2]ꢀ15H2O compound
crystallizes in a triclinic system, and the structure was solved in
ꢀ
the P1 space group. Table 1 summarizes the crystallographic data
and refinement details for K3[1]ꢀ7H2OꢀC3H6O, Na3[1]ꢀ5H2O and
Na2[2]ꢀ15H2O. The packing diagrams for the compounds are given
in the Figs. S1, S2 and S3 (Supporting information), respectively.
Selected bond distances and bond angles are given in Table 2.
3.2.2. Na3[1]ꢀ5H2O
3.2.1. K3[1]ꢀ7H2OꢀC3H6O
A view of the dinuclear copper anion of the compound is de-
picted in Fig. 3, and selected bond lengths and bond angles are listed
in Table 2. The crystal structure of the complex is very similar the
structure of K3[1]ꢀ7H2OꢀC3H6O, except for the three Na+ ions, in-
stead of K+ ions, and fewer water molecules and no acetone of crys-
tallization. The coordination geometry around each copper ion is
best described as a distorted square pyramidal geometry. A struc-
tural view of 1 is depicted in Fig. 2. The Cu(1) center is coordinated
to O(1) and O(3) of aromatic and aliphatic carboxylates of the li-
gand, respectively. The Cu(2) center is coordinated to O(6) and
O(8) of aromatic and aliphatic carboxylates of the ligand, respec-
tively, which are cis to each other. Since the synthesis of the com-
pound uses NaOH, the presence of the carbonato ligand in the
structure must have come from the atmospheric carbon dioxide.
In the crystal structure of K3[1]ꢀ7H2OꢀC3H6O, the complex an-
ion 1 contains a dinucleating ligand ccdp5ꢁ and a bridging carbo-
nato group to produce a five-coordinate geometries around the
copper ions. The coordination geometry around each copper ion
is best described as a distorted square pyramidal geometry
formed by an alkoxo oxygen, an aliphatic carboxylate oxygen,
an aromatic carboxylate oxygen, and a tertiary amine nitrogen
of the ligand, plus one oxygen atom from the bridging carbonato.
The structural view of 1 is depicted in Fig. 2. While Cu(1) is coor-
dinated to O(2) and O(3) of aromatic and aliphatic carboxylates of
the ligand, respectively, in a cis to each other fashion, Cu(2) is
coordinated to O(6) and O(8) of aromatic and aliphatic carboxyl-
ates of the ligand, respectively, also in a cis fashion. The bidentate
Fig. 1. Schematic representation of the synthesis of complexes 1 and 2, shown are only the anioinc complexes.

R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
223
Table 1
Summary of crystallographic data for the compounds.
K3[1]ꢀ7H2OꢀC3H6O
Na3[1]ꢀ5H2O
Na2[2]ꢀ15H2O
Empirical formula
Formula weight
Crystal system
K3Cu2O20N2C27H41
1907.3
Na3Cu2O17N2C24H31
801.54
Monoclinic
P21/c
Na2Cu4O35N4C46H76
3317.01
Triclinic
Triclinic
ꢀ
ꢀ
Space group
P1
P1
0
9.4973(8)
18.322(3)
14.177(3)
18.009(4)
18.663(5)
a (AÅ)
0
11.6634(11)
18.2100(17)
7.4425(10)
23.236(4)
b (AÅ)
0
c (AÅ)
a
b (°)
c
V (ÅA3)
Z, Z0
(°)
97.910(6)
100.740(7)
109.900(7)
1818.8(3)
90
110.287(2)
103.704(3)
102.243(2)
4109.6(17)
111.293(2)
90
2952.2(8)
(°)
0
2,1
4,1
2,1
qcalc
k
1.741
0.71073
98(2)
979
1.597
1.803
0.71073
98(2)
1632
1.568
1.721
0.71073
98(2)
1679
1.120
T (K)
F(000)
l
(mmꢁ1
)
Tmin, Tmax
2h range (°)
Reflections collected
Independent reflections
Data/restraints/parameters
wR(F2 all data)
0.864, 1.000
2.00–27.50
14348
8226 [Rint = 0.0163]
8226/0/530
0.0853
0.792, 1.000
2.44–27.50
21720
6764 [Rint = 0.0285]
6746/0/457
0.0722
0.876, 1.000
2.07–26.00
32001
15995 [Rint = 0.0319]
15995/0/1036
0.1933
R(F obsd data)
0.0308
1.009
0.0312
1.019
0.0809
1.14
GOOF on F2
Observed data [I > 2
r(I)]
7985
6284
14191
Largest and mean shift/s.u.
0.001/0.000
0.968/ꢁ0.574
0.006/0.000
0.904/ꢁ0.429
0.010/0.000
2.235/ꢁ0.641
Largest difference in peak and hole (e/Å3)
2
wR2 = {
R
[w(Fo ꢁ Fc2)2]/
R
[w(Fo2)2]}1/2; R1
=
R
||Fo| ꢁ |Fc||/R|Fo|.
The main distortion of the resulting octahedral coordination
sphere originates in the large bite angles for O(5)–Cu(1)–
O(1) = 165.38(7)° and O(5)–Cu(2)–O(8) = 163.84(6)°, as well as, in
the small bite angles for N(1)–Cu(1)–O(3) = 102.85(6)°,
Cu(1) and Cu(4) adopt a distorted square pyramidal geometry,
Cu(2) and Cu(3) centers exhibit a distorted trigonal bipyramidal
geometry. This is an interesting occurrence since all four copper
ions are surrounded by one bridging alkoxo oxygen, one monoden-
tate aliphatic carboxylate oxygen, one monodentate terminal aro-
matic carboxylate oxygen, and one tertiary amine nitrogen of the
ccdp5ꢁ ligand, and one oxygen from the bridging water molecule.
The two different geometries observed within each dinuclear unit
is due to the different coordination modes adopted between the
extremely flexible ccdp5ꢁ ligand and the metal ions in response
to steric constraints within the complex. Each dinuclear unit pro-
duces a twisted conformation with respect to the aromatic rings
due to one is coordinated towards the front of the complex, while
the other ring is coordinated towards the back. This strain has
yielded a concave shaped cluster core illustrated in Fig. 5.
The inter-copper distances in the intraligand unit is
3.6814(14) Å for Cu(1)ꢀ ꢀ ꢀCu(2) and 3.7132(14) Å for Cu(3)ꢀ ꢀ ꢀCu(4).
The interligand Cuꢀ ꢀ ꢀCu separation is 3.3698(12) Å for
Cu(1)ꢀ ꢀ ꢀCu(3) and 3.4764(13) Å for Cu(2)ꢀ ꢀ ꢀCu(4). The interligand
Cuꢀ ꢀ ꢀCu separation is slightly shorter than the interaligand dis-
tances due to an acute bond angle observed between the two cop-
pers coordinated to the bridging water molecules. These bond
distances are in agreement with those reported for metallohydro-
lase enzymes [20,21,4a].
N(1)–Cu(1)–O(3) = 81.87(6)°,
O(5)–Cu(2)–O(6) = 111.01(6)°,
O(11)–Cu(2)–O(6) = 100.28(6)°, O(8)–Cu(2)–O(6) = 84.38(6)° and
N(2)–Cu(2)–O(6) = 82.26(6)° of the complex. Furthermore, the
Cuꢀ ꢀ ꢀCu distance measures 3.4972(7) Å, which is in agreement with
synthetic copper(II) complexes [18,19] and some metallohydrolase
enzymes reported in the litreature [20,21]. The bond distances and
bond angles for complex 1 are consistent with values reported in
the literature [22].
3.2.3. Na2[2]ꢀ15H2O
A view of the anion of the tetracopper complex 2 is shown in
Fig. 4, and selected bond lengths and bond angles are listed in Ta-
ble 2. The crystal structure of Na2[2]ꢀ15H2O can be described as
two [Cu2(ccdp)(l
-OH2)]2ꢁ anion units, two sodium ions as counter
cations, bridged with two water molecules, along with fifteen
water molecules of crystallization. The metal ions within each
[Cu2]ꢁ pair are chelated to one ccdp5ꢁ ligand. Two water molecules
act as bridges between the two anion units through the Cu(1)–
H2O(19)–Cu(3) and Cu(2)–H2O(20)–Cu(4) links. This arrangement
has important characteristic in terms of active nucleophile possi-
bilities that could be influenced by pH changes for purposes of
bond hydrolysis [23]. The Cu(1)–H2O(19)–Cu(3) and Cu(2)–
H2O(20)–Cu(4) bond angles of 123.2(2)° and 128.1(2)°, respec-
tively, are open enough to afford the further coordination by two
oxygens of the bridging water molecules in a syn–syn bidentate
bridging mode to the pair of copper ions in each dinuclear unit.
The dinucleating ligand within each dinuclear unit binds the cop-
per ions through one bridging alkoxo moiety, one aliphatic and
one aromatic carboxylates as well as amine groups. While all the
four Cu(II) centers are penta-coordinated, they assume two differ-
ent coordination geometries around the metal ions. Whereas both
Furthermore, the flexibility of the H5ccdp ligand originating
from the aromatic and aliphatic carboxylate groups and the bridg-
ing capabilities to the metal centers is highlighted in this structure.
The aromatic carboxylates experience a greater restriction in con-
formation with a separation between carboxylate oxygens being
6.108(5) Å, for Cu(1)ꢀ ꢀ ꢀCu(2), and 6.335(8) Å, for Cu(3)ꢀ ꢀ ꢀCu(4);
whereas the aliphatic carboxylates are less rotationally hindered
showing
a carboxylate oxygen separation of 7.187(8) Å for
Cu(1)ꢀ ꢀ ꢀCu(2), and 7.381(8) Å for Cu(3)ꢀ ꢀ ꢀCu(4). In comparison to
the dinuclear complexes, K3[1]ꢀ7H2OꢀC3H6O and Na3[1]ꢀ5H2O, the
complex showed a significant change in the distance separating

224
R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
Table 2
Selected bond distances and bond angles for compounds.
K3[1]ꢀ7H2OꢀC3H6O
Na3[1]ꢀ5H2O
Na2[2]ꢀ15H2O
Bond lengths (Å)
Cu1–O5
Cu1–O10
Cu1–O2
Cu1–N1
Cu1–O3
Cu1–Cu2
Cu2–O5
Cu2–O11
Cu2–O8
Cu2–N2
Cu2–O6
1.9339(15)
1.9379(15)
1.9798(15)
2.0740(18)
2.1898(15)
3.4699(4)
1.9067(15)
1.9374(16)
1.9637(15)
2.0867(17)
2.2371(15)
Cu1–O5
Cu1–O10
Cu1–O1
Cu1–N1
Cu1–O3
Cu1–Cu2
Cu2–O5
Cu2–O11
Cu2–O8
Cu2–N2
Cu2–O6
1.9130(15)
1.9289(16)
1.9816(15)
2.0772(18)
2.1790(15)
3.4972(7)
1.9129(15)
1.9287(15)
1.9986(15)
2.0440(18)
2.2480(15)
Cu1–N1
Cu1–O1
Cu1–O3
Cu1–O19
Cu1–O5
Cu2–N2
Cu2–O5
Cu2–O6
Cu2–O8
Cu2–O20
Cu3–O19
Cu3–O14
Cu3–N3
Cu3–O12
Cu3–O10
Cu4–O20
Cu4–O14
Cu4–O15
Cu4–N4
Cu4–O17
2.019(5)
2.283(5)
2.009(4)
1.925(4)
1.955(4)
2.040(5)
2.002(4)
2.078(5)
2.096(4)
1.928(4)
1.906(4)
1.994(4)
2.009(5)
2.090(4)
2.159(4)
1.939(4)
1.975(4)
2.006(4)
2.026(5)
2.260(4)
Bond angles (°)
O5–Cu1–O10
O5–Cu1–O2
O10–Cu1–O2
O5–Cu1–N1
O10–Cu1–N1
O2–Cu1–N1
O5–Cu1–O3
O10–Cu1–O3
O2–Cu1–O3
N1–Cu1–O3
Cu1–O5–Cu2
O5–Cu2–O11
O5–Cu2–O8
O11–Cu2–O8
O5–Cu2–N2
O11–Cu2–N2
O8–Cu2–N2
O5–Cu2–O6
O8–Cu2–O6
N2–Cu2–O6
O11–Cu2–O6
93.79(6)
173.71(6)
90.21(6)
85.10(7)
166.74(7)
89.90(7)
93.68(6)
110.72(6)
89.44(6)
82.54(6)
129.23(8)
92.79(6)
169.28(6)
89.84(7)
85.76(7)
177.43(7)
91.20(7)
97.70(6)
91.97(6)
81.06(6)
101.25(7)
O5–Cu1–O10
O5–Cu1–O1
O10–Cu1–O1
O5–Cu1–N1
O10–Cu1–N1
O1–Cu1–N1
O5–Cu1–O3
O10–Cu1–O3
O1–Cu1–O3
N1–Cu1–O3
Cu1–O5–Cu2
O5–Cu2–O11
O5–Cu2–O8
O11–Cu2–O8
O5–Cu2–N2
O11–Cu2–N2
O8–Cu2–N2
O5–Cu2–O6
O8–Cu2–O6
N2–Cu2–O6
95.22(6)
165.38(7)
89.11(6)
86.09(7)
178.30(7)
89.88(7)
102.85(6)
96.77(6)
90.46(6)
81.87(6)
132.15(8)
94.33(6)
163.84(6)
87.42(6)
85.30(7)
177.38(7)
92.21(7)
111.01(6)
84.38(6)
82.26(6)
O19–Cu1–O5
O19–Cu1–O5
O19–Cu1–O3
O5–Cu1–O3
O19–Cu1–N1
O5–Cu1–N1
O3–Cu1–N1
O19–Cu1–O1
O5–Cu1–O1
O3–Cu1–O1
N1–Cu1–O1
Cu1–O5–Cu2
O20–Cu2–O5
O5–Cu2–N2
94.33(17)
94.33(17)
94.17(18)
164.48(19)
174.2(2)
86.7(2)
83.6(2)
92.68(17)
96.11(19)
96.44(19)
92.9(2)
137.0(2)
95.99(17)
84.9(2)
125.5(2)
88.43(17)
92.50(19)
95.99(17)
84.9(2)
128.1(2)
92.10(18)
175.4(2)
86.6(2)
95.16(18)
132.76(19)
82.6(2)
91.92(17)
118.60(18)
92.6(2)
107.74(17)
123.2(2)
95.68(17)
94.80(18)
162.49(19)
175.49(19)
85.43(19)
83.1(2)
90.66(17)
98.38(18)
95.48(17)
93.51(18)
138.6(2)
O5–Cu2–O6
O20–Cu2–O8
N2–Cu2–O8
O20–Cu2–O5
O5–Cu2–N2
Cu2–O20–Cu4
O19–Cu3–O14
O19–Cu3–N3
O14–Cu3–N3
O19–Cu3–O12
O14–Cu3–O12
N3–Cu3–O12
O19–Cu3–O10
O14–Cu3–O10
N3–Cu3–O10
O12–Cu3–O10
Cu3–O19–Cu1
O20–Cu4–O14
O20–Cu4–O15
O14–Cu4–O15
O20–Cu4–N4
O14–Cu4–N4
O15–Cu4–N4
O20–Cu4–O17
O14–Cu4–O17
O15–Cu4–O17
N4–Cu4–O17
Cu4–O14–Cu3
the aliphatic carboxylate oxygens. For example, in complex K3-
[1]ꢀ7H2OꢀC3H6O, the distance between aromatic carboxylate oxy-
gens and aliphatic carboxylate oxygens is 7.179(3) and
3.450(3) Å, respectively. The degree of flexibility and bridging
capabilities of the ligand is also nicely displayed when the dicopper
and the tetracopper structures are compared. The distance be-
tween the oxygens, O(19)–O(20), of the two bridging waters in
complex Na2[2]ꢀ15H2O measures 2.681(5) Å, which is a much lar-
ger separation than the distance between the two oxygens,
O(10)–O(11), of the bridging carbonato ligand, measuring
2.268(3) Å in K3[1]ꢀ7H2OꢀC3H6O. The Cu–O bond distances are
within range of previously reported alkoxo bridged dinuclear cop-
per systems [22a,b], except for the Cu–Ocarboxylate (aromatic) which
are markedly longer than the average distances. The Cu–Ocarboxylate

R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
225
and Cu–Namine bond distances are in the range of those previously
reported in the literature [22].
3.4. Magnetic studies
Magnetic measurements were carried out on polycrystalline
powder samples ranging from 2 to 300 K at the applied fields of
5 kOe. The compounds K3[1]ꢀ7H2OꢀC3H6O and Na2[2]ꢀ15H2O (due
to structural similarity of K3[1]ꢀ7H2OꢀC3H6O and Na3[1]ꢀ5H2O, we
carried out the magnetic study only for K3[1]ꢀ7H2OꢀC3H6O) show
similar behavior. In Fig. 6 we represent the magnetic behavior of
1 and 2 in the forms of vM versus T and
vMT versus T plots.
It is well-known that the magnetic behavior of divalent copper
complexes bridged by a pair of hydroxide or alkoxide oxygen
atoms is highly dependent on the Cu-O–Cu bridge angle [24,25].
Also it can be influenced, but in smaller measure, by the Cu–O
bridge distance, the Cuꢀ ꢀ ꢀCu separation, the geometry around the
copper(II) center, and the geometry around the bridging oxygen
atom. Hatfield and Hodgson have found a linear correlation be-
tween the experimentally determined exchange coupling constant
Fig. 2. ORTEP drawing with atomic numbering scheme of the molecular structure
of complex ion, 1, from K3[1]ꢀ7H2OꢀC3H6O. Hydrogen atoms, counter ions, and
solvent molecules of crystallization have been omitted for clarity.
and the Cu–O–Cu angle (
r
). An antiferromagnetic character is
larger than 97.6°, while ferromagnetic
. An apparent similar linear relation-
found for complexes with
r
appears for smaller values of
r
ship for alkoxide cases shows that at angles around 95.6° the ex-
change integral approaches zero, the point of the ‘‘accidental
orthogonality’’. The magnetic response of compounds 1 and 2
probably will be dominated by the expected strong antiferromag-
netic coupling via the alkoxide bridge with the Cu–O–Cu bond an-
gles range from 123.2° to 138.6°.
Compound 1 shows a v
MT value of 0.38 cm3 K molꢁ1 for the Cu2
unit, smaller than that expected for two uncoupled S = 1/2 ions
with g = 2.0 (0.75 cm3 K molꢁ1). On cooling, the magnetic suscepti-
bility vM presents a maximum at 143.8 K, whereas
vMT decreases
quickly, indicating a very strong antiferromagetic coupling. From
|J|/kTmax = 1.599, |J| is estimated to be about 159.8 cmꢁ1 [26]. The
vM value increases below 32 K because of magnetic impurity. The
experimental magnetic data were fitted using the Bleaney–Bowers
expression (1), based on the following Hamiltonian: H = ꢁJ(S1S2)
[27].
Fig. 3. ORTEP drawing with atomic numbering scheme of the molecular structure
of complex ion, 1, from the Na3[1]ꢀ5H2O. Hydrogen atoms, counter ions, and solvent
molecules of crystallization have been omitted for clarity.
2Nb2g2
kðT ꢁ hÞ ½3 þ expðꢁJ=kTÞꢃ
þ TIP
1
Nb2g2S0ðS0 þ 1Þ
ð1 ꢁ Þ þ
3kT
q
vm
¼
q
ð1Þ
The parameters N, g, b, and k in the equation have their usual
meanings with some applied corrections: paramagnetic impurity
(fraction ), TIP (temperature independent paramagnetism), and
q
a Weiss-like corrective term (h). After the best least-squares fit to
the experimental data, the parameters are given as: g = 2.01,
J = ꢁ169.6 cmꢁ1, h = 0 K,
q
= 0.08, and TIP = 6.37 ꢄ 10ꢁ4 emu molꢁ1
with a final agreement factor R = 4.86 ꢄ 10ꢁ5 [R =
R
(v
mTobsd
ꢁ
vm-
T
calcd)2/ mTobsd)2] and the correlation coefficient R2 of 0.9976.
R(v
Complex 2 shows a
unit, smaller than that expected for tetranuclear uncoupled S = 1/
2 ions with g = 2.0 (1.5 cm3 K molꢁ1). Upon cooling,
MT decreases
v
MT value of 0.55 cm3 K molꢁ1 for the Cu4
v
sharply, while vM presents a maximum at 175.7 K, and then de-
creases quickly reaching a practically diamagnetic behavior below
50 K, indicating a very strong antiferromagnetic coupling. The
similar behavior was also observed in a tetranuclear copper
compound [28]. In complex 2, two alkoxide and two water oxy-
gen atoms alternatively bridge the four copper ions to form a
Cu4O4 ring with the sequential bridging Cu–O–Cu angles of
137.0°, 123.2°, 138.6° and 128.1°. The Hamiltonian to use is
H = ꢁJ1S1S2 ꢁ J2S2S3 ꢁ J3S3S4 ꢁ J4S1S4. Taking into account the com-
pound topology, one can count the four exchange pathways,
grouped into two averaged different exchange parameters, J1 and
Fig. 4. ORTEP drawing with atomic numbering scheme of the molecular structure
of complex ion, 2, from Na2[2]ꢀ15H2O. Hydrogen atoms, counter ions, and solvent
molecules of crystallization have been omitted for clarity.

226
R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
Fig. 5. (Left) Representation of the metal core and bridging water molecules (representing by O19 and O20) linking the two dinuclear units in complex ion, 2. (Right)
Representation of the metal core emphasizing its concave shape in complex ion, 2.
J2, corresponding to the alkoxide and water bridges, respectively.
But it is difficult to find the energies and eigenfunctions of a spin
0.0025
Hamiltonian for the two J model with D2h symmetry. On the base
of the assumption that J = J1 = J2 = J3 = J4, in order to use the conven-
0.012
0.0020
tional spin–vector coupling model, eigenvalues of the Hamiltonian
can be obtained analytically and are given by Eq. (2).
0.0015
0.009
0.0010
J
2
EðS0; S13; S24Þ ¼ ꢁ ½ðS0ðS0 þ 1Þ ꢁ ðS13ðS13 þ 1Þ ꢁ ðS24ðS24 þ 1Þꢃ
ð2Þ
0.0005
0.0000
0.006
0.003
0.000
where S13 = S1 + S3; S24 = S2 + S4; S0 = S1 + S2 + S3 + S4. The relative
50
100
150
200
250
300
M
χ
energies of the states are:
Quintet: E (2,1,1) = ꢁJ
Triplets: E (1,1,1) = J
E (1,1,0) = 0
E (1,0,1) = 0
Singlets: E (0,1,1) = ꢁ2J
0
50
100
150
200
250
300
E (0,0,0) = 0
T
/ K
By substituting the appropriate energy terms into the modified
van Vleck Eq. (3) refers to the energy of each spin state defined by
S0, the susceptibility values can be computed as a function of
temperature.
0.6
0.5
0.4
0.3
0.2
0.1
0.0
P
Nb2g2
S0ðS0 þ 1Þð2S0 þ 1Þ expðꢁEðSÞ=kTÞ
P
vm
¼
ð1 ꢁ Þ
q
ð2S0 þ 1Þ expðꢁEðSÞ=kTÞ
3kðT ꢁ hÞ
Nb2g2SðS þ 1Þ
3kT
q
þ
þ TIP
ð3Þ
After the best least-squares fit to the experimental data above
50 K, the parameters are given as: g = 2.00, J = ꢁ186.4 cmꢁ1
,
T
= 0.15, and TIP = 7.82 ꢄ 10ꢁ4 cm3 molꢁ1 with a final
M
h = 0 K,
q
χ
1 per Cu2
2 per Cu2
2 per Cu4
agreement factor R = 9.85 ꢄ 10ꢁ5 [R =
R
(v
mTobsd
ꢁ
v R(vm-
mTcalcd)2/
T
obsd)2] and the correlation coefficient R2 of 0.9972. If considering
the exchange coupling J2 via the water oxygen bridge can be ne-
glected, the magnetic susceptibility will follow the Eq. (1). The best
least-squares fit gave the parameters as: g = 2.00, J1 = ꢁ228.6 cmꢁ1
,
0
50
100
150
200
250
300
= 0.14, and TIP = 7.31 ꢄ 10ꢁ4 cm3 molꢁ1 with a final
T
/ K
h = 0 K,
q
agreement factor R = 4.50 ꢄ 10ꢁ5 [R =
R
(v
mTobsd
ꢁ
v R(vm-
mTcalcd)2/
Fig. 6. (Top) Plot of vM vs. T for K3[1]ꢀ7H2OꢀC3H6O ( ) and Na2[2]ꢀ15H2O ( ). The
inset shows the maximum between 50–300 K. (Bottom) Plot of observed MT vs. T
T
obsd)2] and the correlation coefficient R2 of 0.9950. Although we
v
cannot employ the irreducible tensor operator formalism (ITO) to
fit the two J model with D2h symmetry, the exchange coupling J1
for K3[1]ꢀ7H2OꢀC3H6O ( ),Na2[2]ꢀ15H2O per Cu4 unit ( ) or Cu2 unit ( ). The solid
lines represent the best theoretical fits.

R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
227
Table 3
via the alkoxide bridge in 3 in both cases above is larger than that
in 1, which is reasonable due to the corresponding Cu–O–Cu bridg-
ing angles in 2 larger than the one in 1.
Electrochemical data for copper complexes K3[1]ꢀ7H2OꢀC3H6O, Na3[1]ꢀ5H2O, and
Na2[2]ꢀ15H2O.
Complex
E1/2, V (
D
Ep, mV)
Epc (V)
ꢁ0.051
Epa (V)
ipc/ipa
K3[1]ꢀ7H2OꢀC3H6Oa
0.050
3.5. Electrochemical studies
ꢁ0.134
Na3[1]ꢀ5H2Ob
Na2[2]ꢀ15H2Oa
ꢁ0.013 (339)
ꢁ0.021 (60)
ꢁ0.182
ꢁ0.127
ꢁ0.419
0.157
3.7216
0.650
ꢁ0.110
0.085
The redox properties of the complexes in water have been
investigated by cyclic voltammetry using a glassy carbon or a plat-
inum working electrode, KCl and platinum wire as supporting elec-
trolyte and auxiliary electrode, respectively. The cathodic scan of
solutions of complexes K3[1]ꢀ7H2OꢀC3H6O, Na3[1]ꢀ5H2O and
Na2[2]ꢀ15H2O within 750 to ꢁ1000 mV potential window at a rate
of 75 mV/s resulted in an electrochemical activity. Whereas the
cyclic voltammograms are presented in Fig. 7, the electrochemical
data for the complexes are given in Table 3. Additionally, the cyclic
voltammograms of the complexes in 20–150 mV/s scan rate range,
are presented in Figs. 4S, 5S and 6S (Supporting information). Un-
der similar experimental conditions, the electrochemical studies of
the free ligand using cyclic voltammetry revealed no electrochem-
ical activity within the scanned potential window. Hence, the elec-
trochemical waves observed in the cyclic voltammagrams of the
complex can be characterized as metal-based electron transfer pro-
cesses. The electrochemical properties of complex K3[1]ꢀ7H2OꢀC3-
H6O, Na3[1]ꢀ5H2O and Na2[2]ꢀ15H2O feature an irreversible one
electron reduction and one oxidation peak. On the other hand,
complex Na2[2]ꢀ15H2O showed a more complex electrochemical
behavior with two oxidation waves and two reduction waves.
Cyclic voltammograms in aqueous solutions of the compounds were measured at a
scan rate of 75 mV/s using aPt and bGC working electrodes and 0.2 M KCl supporting
electrolyte. All potential are scaled to NHE using methyl viologen as a standard
(MV2+/MV+, E1/2NHE = ꢁ0.45 V vs. NHE in water) [25].
Fig. 7(a) shows the electrochemical response of complex K3[1]ꢀ7H2-
OꢀC3H6O when initially the potential was scanned towards nega-
tive values. The irreversible reduction peak at 0.050 V is assigned
to the reduction of [1]3ꢁ/4ꢁ. Further scanning towards more nega-
tive potentials resulted only in the reduction of the solvent mole-
cule. Upon reversing the scan towards positive potentials, two
separate irreversible oxidations at ꢁ0.050 and ꢁ0.134 V were ob-
served, and have been assigned to the [1]4ꢁ/3ꢁ and [1]3ꢁ/2- oxida-
tions. Shown in Fig. 7(b) is the electrochemical response of
complex 2 under similar experimental conditions. The voltammo-
gram shows a clear irreversible reduction with Epc value at
-0.182 V and oxidation with Epa at 0.157 V are assigned to the
[1]4ꢁ/3ꢁ redox couple. Presented in Fig. 7(c) is cyclic voltammo-
gram of complex Na2[2]ꢀ15H2O in aqueous solution. Unlike to the
dicopper(II) complexes, the electrochemical response of this tetra-
copper complex exhibited more complex redox activity. The data
indicate one reversible and one quasi reversible redox behavior.
While the reversible peak, due to the [2]2ꢁ/3ꢁ couple, has E1/2 value
of ꢁ0.021 V, the quasi reversible peak has its Epc and Epa peaks at
ꢁ0.419 and 0.085 V, respectively. The cathodic peak is assigned
a
2.5 µA
to the reduction of [2]3ꢁ/4ꢁ and the anodic peak is due to [2]4ꢁ/3ꢁ
.
When the values of the first reduction potentials for the dicop-
per(II) and the tetracopper(II) complex are compared, a positive
cathodic shift in the E1/2 value of [2]2ꢁ/3ꢁ versus [1]3ꢁ/4ꢁ is
observed. The potential shift is partly attributed to the difference
in the overall charge of the complexes, dianionic versus trianionic
nature of the complexes in solution. The accessibility of reduction
potential values of the complexes are similar when compared to
the di- and trianionic copper complexes reported in the literature
[29].
b
5 µA
4. Conclusions
Three new polynuclear copper complexes with interesting coor-
dination chemistry have been synthesized and fully characterized.
The symmetrical dinucleating ligand, H5ccdp, forms a dinuclear
copper complex, K3[1]ꢀ7H2OꢀC3H6O, in the presence of a weak base.
However, a different di-copper compound, Na3[1]ꢀ5H2O, and a tet-
ra-copper compound Na2[2]ꢀ15H2O, was synthesized in the pres-
ence of a strong base. In Na2[2]ꢀ15H2O, the crystal structure
comprises a rare topology of eight-membered ring formed by link-
ing four coppers and two bridging water molecules. The coordina-
tion environment around the Cu(II) ions of the dinuclear
complexes assume a distorted square pyramidal geometry. In the
tetranuclear complex, however, the copper centers possess either
a distorted square pyramidal or distorted trigonal bipyramidal
geometry. As attempts to obtain crystals of compound Na3[1]ꢀ5H2O
in Argon atmosphere have been unsuccessful, this clearly indicates
that atmospheric carbon dioxide plays a role in the formation of
the Na3[1]ꢀ5H2O. Studies are underway to further explore the reac-
tivity of the complex towards carbon dioxide. The variable-temper-
c
1 µA
650
350
50
-250
-550
-850
Potential (mV)
Fig. 7. Cyclic voltammograms in aqueous solutions of (a) Compound K3[1]ꢀ7H2-
OꢀC3H6O; (b) compound Na3[1]ꢀ5H2O and (c) compound Na2[2]ꢀ15H2O measured at
a scan rate of 75 mV/s using Pt (complexes K3[1]ꢀ7H2OꢀC3H6O and Na2[2]ꢀ15H2O)
and GC (complex Na3[1]ꢀ5H2O) working electrodes and 0.2 M KCl supporting
electrolyte. All potential are scaled to NHE using methyl viologen as a standard
(MV2+/MV+, E1/2NHE = ꢁ0.45 V vs. NHE in water) [25].

228
R.A. Joy et al. / Inorganica Chimica Acta 394 (2013) 220–228
(f) E.E. Kim, H.W. Wyckoff, J. Mol. Biol. 218 (1991) 449;
(g) T. Knofel, N. Strater, J. Mol. Biol. 309 (2001) 239;
(h) L.W. Guddat, A.S. McAlpine, D. Hume, S. Hamilton, J. Jersey, J.L. Martin,
Structure 7 (1999) 757.
ature magnetic susceptibility studies of K3[1]ꢀ7H2OꢀC3H6O and
Na2[2]ꢀ15H2O reveal the overall strong antiferromagnetic coupling
between Cu(II) ions with J values of ꢁ169.6 and ꢁ186.4 cmꢁ1
,
[5] (a) M. Li, X.-G. Meng, J. Du, P. Zhang, W.-P. Zeng, Y. Liu, X.-C. Zeng, J. Dispersion
Sci. Technol. 30 (2009) 1182;
respectively. The fairly accessible metal based oxidation of the
complexes is partly attributed to the di- and tri-anionic nature of
the complexes in solution. This work demonstrates the versatility
of the penta-anionic ligand, ccdp5ꢁ, in forming different anionic
multi-copper complexes, under different reaction conditions, with
very accessible CuIII/II reduction potentials and strong antiferro-
maginc coupling.
(b) N. Burzlaff, Adv. Inorg. Chem. 60 (2008) 101;
(c) M. Jarenmark, H. Carlsson, E. Nordlander, C. R. Chim. 10 (2007) 433.
[6] (a) D. Mastropaolo, D.A. Powers, J.A. Potenza, H.J. Schugar, Inorg. Chem. 15
(1976) 1444;
(b) A. Drzewiecka, A.E. Koziol, M. Lowczak, T. Lis, Acta Crystallogr., Sect. E 63E
(2007) m2339;
(c) G. Zhang, G. Yang, J.S. Ma, Cryst. Growth Des. 6 (2006) 375.
[7] (a)K.D. Karlin, Z. Tyeklar (Eds.), Bioinorganic Chemistry of Copper, Chapman &
Hall, New York, London, 1993;
Acknowledgments
(b) B. Reinhammer, Copper Proteins and Copper Enzymes, vol. 3, CRC Press,
Boca Raton, FL, 1984. pp. 1–35;
(c) E.I. Solomon, P. Chen, M. Metz, S.K. Lee, A.E. Palmer, Angew. Chem., Int. Ed.
40 (2001) 4570;
(d) E.I. Solomon, U.M. Sundaram, T.E. Machonkin, Chem. Rev. 96 (1996) 2563;
(e) K.A. Magnus, H. Ton-That, J.E. Carpenter, Chem. Rev. (1994) 727;
(f) M.C. Linder, Biochemistry of Copper, Plenum, New York, 1991;
(g) E.T. Adman, Adv. Protein Chem. 42 (1991) 145.
We are indebted to the Robert A. Welch Foundation for their
support of this work under Grant AX-1540, and the Chemistry
Department at the University of Texas at San Antonio for the
support.
[8] (a) G.-F. Zhang, Q.-P. Zhou, Y.-L. Dou, M.-H. Yin, Y. Wang, Appl. Organomet.
Chem. 21 (2007) 1059;
(b) S. Sreedaran, K.S. Bharathi, A.K. Rahiman, L. Jagadish, V. Kaviyarasan, V.
Narayanan, Polyhedron 27 (2008) 2931.
[9] W.B. Tolman, Acc. Chem. Res. 30 (1997) 227.
Appendix A. Supplementary material
CCDC CD845591, CD845589, and CD845590 contain the supple-
mentary
crystallographic
data
for
K3[1]ꢀ7H2OꢀC3H6O,
[10] (a) F.H. Zelder, A.A. Mokhir, R. Kramer, Inorg. Chem. 42 (2003) 8618;
(b) E.L. Hegg, J.N. Burstyn, Inorg. Chem. 35 (1996) 7474;
(c) E.L. Hegg, J.N. Burstyn, K.A. Deal, L.L. Kiessling, Inorg. Chem. 36 (1997)
1715;
(d) E.L. Hegg, J.N. Burstyn, Coord. Chem. Rev. 173 (1998) 133;
(d) Y. An, M.-L. Tong, L.-N. Ji, Z.-W. Mao, Dalton Trans. (2006) 2066;
(e) M.J. Belousoff, L. Tjioe, B. Graham, L. Spiccia, Inorg. Chem. 47 (2008) 8641;
(f) M.J. Belousoff, B. Graham, L. Spiccia, Eur. J. Inorg. Chem. (2008) 4133.
[11] (a) M. Golicnik, Acta Chim. Slov. 57 (2010) 272;
(b) M.C.B. Oliveira, D. Mazera, M. Scarpellini, P.C. Severino, A. Neves, H.
Terenzi, Inorg. Chem. 48 (2009) 2711;
Na3[1]ꢀ5H2O and Na2[2]ꢀ15H2O, respectively. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via http://www.ccdc.cam.ac.uk/data_request/cif. Supple-
mentary data associated with this article can be found, in the on-
line version, at http://dx.doi.org/10.1016/j.ica.2012.08.013.
References
(c) H.-C. Liang, Y. Zhang, M.M. Hetu, Inorg. Chem. Commun. 10 (2007) 204;
(d) M.J. Belousoff, M.B. Duriska, B. Graham, S.R. Batten, B. Moubaraki, K.S.
Murray, L. Spiccia, Inorg. Chem. 45 (2005) 3746;
(e) F.H. Fry, A.J. Fischmann, M.J. Belousoff, L. Spiccia, J. Brugger, Inorg. Chem. 44
(2005) 941;
[1] (a) M. Zhao, C. Stern, A.G.M. Barrett, B.M. Hoffman, Angew. Chem., Int. Ed. 42
(2003) 462;
(b) H. Zheng, W. Zhe-Ming, G. Song, Y. Chun-Hua, Inorg. Chem. 45 (2006) 6694;
(c) J.S. Miller, Dalton Trans. (2006) 2742;
(d) C. Cadiou, M. Murrie, S. Parsons, J.M. Rawson, R.E.P. Winpenny, Chem.
Commun. 24 (2001) 2666;
(e) D. Gatteschi, R. Sessoli, J. Magn. Magn. Mater. (2004) 272;
(f) P. Guerriero, S. Tamburini, P.A. Vigato, Coord. Chem. Rev. 139 (1995) 17;
(g) C.J. Cairns, D.H. Busch, Coord. Chem. Rev. 69 (1986) 1;
(h) O. Kahn, Molecular Magnetism, VCH, Weinheim, Germany, 1993;
(i) O. Kahn, Struct. Bonding 68 (1987) 89.
(f) L.R. Gahan, S.J. Smith, A. Neves, G. Schenk, Eur. J. Inorg. Chem. (2009) 2745.
[12] A.B.S. Curtiss, M. Bera, G.T. Musie, D.R. Powell, Dalton Trans. (2008) 2717.
[13] CRYSTALCLEAR
,
User Manual, Rigaku/MSC Inc., Rigaku Corporation, The
Woodlands, TX, 2005.
[14] Higashi, ABSCOR, Rigaku Corporation, Tokyo, Japan, 1995.
[15] G.M. Sheldrick, SHELXS97. Program for the Solution of Crystal Structures,
University of Göttingen, Germany, 1997.
[16] G.M. Sheldrick, SHELXL97. Program for Crystal Structure Analysis, University of
Göttingen, Germany, 1997.
[17] S. Rode, C. Henninot, C. Vallieres, M. Matlosz, J. Electrochem. Soc. 151 (2004)
405.
[18] S. Gupta, A. Mukherjee, M. Nethaji, A.R. Chakravarty, Polyhedron 24 (2005)
1922.
[19] C.-H. Weng, S.-C. Cheng, H.-M. Wei, H.-H. Wei, C.-J. Lee, Inorg. Chim. Acta 359
(2006) 2029.
[20] (a) E. Jabri, M.B. Carr, R.P. Hausinger, P.A. Karplus, Science 268 (1995) 998;
(b) S. Benini, W.R. Rypniewski, K.S. Wilson, S. Miletti, S. Ciurli, S. Mangani,
Structure 7 (1999) 205.
[21] M.H. Kim, W.-C. Choi, H.O. Kang, J.S. Lee, B.S. Kang, K.-J. Kim, Z.S. Derewenda,
T.-K. Oh, C.H. Lee, J.-K. Lee, Proc. Natl. Acad. Sci. 49 (2005) 17606.
[22] (a) T.-C. Lai, W.-H. Chen, C.-J. Lee, B.-C. Wang, H.-H. Wei, J. Mol. Struct. 935
(2009) 97;
[2] (a) V.B. Romakh, B. Therrien, G. Labat, H.S. Evans, G.B. Shulpin, G. Suess-Fink,
Inorg. Chim. Acta 359 (2006) 3297;
(b) M. Costas, M.C. Anda, A. Llobet, T. Parella, H.S. Evans, E. Pinilla, Eur. J. Inorg.
Chem. 4 (2004) 857;
(c) R. Delgado, M.F. Cabral, R. Castanheira, A. Zhang, R. Herrmann, Polyhedron
21 (2002) 2265.
[3] (a) J.L. McLain, J. Lee, J.T. Groves, in: B. Meunier (Ed.), Biomimetic Oxidations
Catalyzed by Transition Metal Complexes, Imperial College Press, London,
2000;
(b)G.L. Eichhorn, L.G. Marzilli (Eds.), Models in Inorganic Biochemistry,
Prentice-Hall, Engle-wood Cliffs, NJ, 1993;
(c) T.S. Dzhabiev, A. Shilov, Russ. J. Phys. Chem. A 85 (2011) 397;
(d) M. Komiyama, J. Sumaoka, Curr. Opin. Chem. Biol. 2 (1998) 751;
(e) P. Molenveld, J.F.J. Engbersen, D.N. Reinhoudt, Chem. Soc. Rev. 29 (2000) 75;
(f) T. Niittymaki, H. Lonnberg, Org. Biomol. Chem. 4 (2006) 15;
(g) Q.-X. Xiang, J. Zhang, P.-Y. Liu, C.-Q. Xia, Z.-Y. Zhou, R.-G. Xie, X.-Q. Yu, J.
Inorg. Biochem. 99 (2005) 1661;
(h) W. Peng, P.-Y. Liu, N. Jiang, H.-H. Lin, G.-L. Zhang, X.-Q. Yu, Bioorg. Chem. 33
(2005) 374;
(i) Q.-L. Li, J. Huang, G.-L. Zhang, N. Jiang, C.-Q. Xia, H.-H. Lin, J. Wu, X.-Q. Yu,
Bioorg. Med. Chem. 14 (2006) 4151;
(j) C.-Q. Xia, L. Jiang, J. Zhang, S.-Y. Chen, H.-H. Lin, X.-Y. Tan, Y. Yue, X.-Q. Yu,
Bioorg. Med. Chem. 14 (2006) 5756;
(k) X.-Y. Wang, J. Zhang, K. Li, N. Jiang, S.-Y. Chen, H.-H. Lin, Y. Huang, L.-J. Ma,
X.-Q. Yu, Bioorg. Med. Chem. 14 (2006) 6745;
(l) E.T. Papish, M.T. Taylor, F.E. Jernigan, M.J. Rodig, R.R. Shawhan, G.P. Yap, F.A.
Jove, Inorg. Chem. 45 (2006) 2242.
(b) P. Seppala, E. Colacio, A.J. Mota, R. Sillanpaa, Inorg. Chim. Acta 363 (2010)
755;
(c) J. Fielden, J. Sprott, D.-L. Long, P. Kogerler, L. Cronin, Inorg. Chem. 45 (2006)
2886;
(d) L. Wang, J. Wang, C. Xie, J. Coord. Chem. (2008) 3401;
(e) V. Chandrasekhar, T. Senepati, A. Dey, E.C. Sanudo, Inorg. Chem. 50 (2011)
1420.
[23] D. Lee, P.-L. Hung, B. Spingler, S.J. Lippard, Inorg. Chem. 41 (2002) 521.
[24] V.H. Crawford, H.W. Richardson, J.R. Wasson, D.J. Hodgson, W.E. Hatfield,
Inorg. Chem. 15 (1976) 2107.
[25] M. Kodera, N. Terasako, T. Kita, Y. Tachi, K. Kano, M. Yamazaki, M. Koikawa, T.
Tokii, Inorg. Chem. 36 (1997) 3861.
[26] B. Bleaney, K.D. Bowers, Proc. R. Soc. (Lond.) Ser. A 214 (1952) 451.
[27] O. Kahn, Molecular Magnetism, VCH, New York, 1993.
[28] M.S.E. Fallah, A. Escuer, R. Vicente, F. Badyine, X. Solans, M. Font-Bardia, Inorg.
Chem. 43 (2004) 7218.
[4] (a) J.E. Coleman, Annu. Rev. Biophys. Biomol. Struct. 21 (1992) 441;
(b) A. Volbeda, A. Lahm, F. Sakiyama, D. Suck, EMBO J. 10 (1991) 1607;
(c)I. Bertini, H.B. Gray, S.J. Lippard, J.S. Valentine (Eds.), Bioinorganic
Chemistry, University Science Books, Mill Valley, CA, 1994;
(d) E.Y. Tshuva, S.J. Lippard, Chem. Rev. 104 (2004) 987;
(e) E.R. Kantrowitz, in: A. Messerschmidt, W. Bode, M. Cygler (Eds.), Handbook
of Metalloproteins, vol. 3, John Wiley & Sons, Chichester, 2004;
[29] C.L. Bird, A.T. Kuhn, Chem. Soc. Rev. 10 (1981) 49.