Syntheses, crystal structures, thermal and magnetic properties of new heterotrinuclear CuII–LnIII–CuII complexes incorporating N2O4-donor Schiff base ligands

Article abstract of DOI:10.1016/j.poly.2018.01.023

New heterotrinuclear complexes [Cu₂La(H₂hamp)₂(NO₃)₂H₂O]NO₃·6MeOH (1), [Cu₂Pr(H₂hamp)₂(NO₃)₃]·6MeOH (2), [Cu₂Nd(

Full text of DOI:10.1016/j.poly.2018.01.023

Polyhedron 144 (2018) 225–233
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Syntheses, crystal structures, thermal and magnetic properties of new
heterotrinuclear CuII–LnIII–CuII complexes incorporating N2O4-donor
Schiff base ligands
a
b
a
Beata Cristóvão a, , Dariusz Osypiuk , Barbara Miroslaw , Agata Bartyzel
⇑
a Department of General and Coordination Chemistry, Maria Curie-Sklodowska University, Maria Curie-Sklodowska sq. 2, 20-031 Lublin, Poland
b Department of Crystallography, Maria Curie-Sklodowska University, Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 November 2017
Accepted 23 January 2018
New heterotrinuclear complexes [Cu2La(H2hamp)2(NO3)2H2O]NO3ꢀ6MeOH (1), [Cu2Pr(H2hamp)2(NO3)3]ꢀ
6MeOH (2), [Cu2Nd(H2hamp)2(NO3)(MeOH)2](NO3)2ꢀH2O (3) where H2hamp is the dideprotonated forms
of the N,N0-bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane were obtained in the reac-
tion of the Schiff base ligand with the respective salts of CuII and LnIII. The compounds 1–3 crystallize in
the monoclinic space group P21/n. The X-ray structures of 1–3 show the central LnIII ion surrounded by
two CuH2hamp units, so that LnIII and CuII ions are linked by phenoxido bridging groups. The compounds
1–3 are stable at room temperature and their decomposition processes proceed in the similar way. The
temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicated
that the interaction between CuII and LnIII ions (Ln = Pr and Nd) is antiferromagnetic.
Keywords:
Schiff base
N2O4-donor ligand
Heterotrinuclear complex
Phenoxo bridge
3d–4f complex
Ó 2018 Elsevier Ltd. All rights reserved.
1. Introduction
complexes of the general formula [{ML(py)}2U] (M = Co, Ni, Zn)
or [{CuL(py)}M0{CuL}] (M0 = U, Th, Zr). In the series of obtained
N,N0-Bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethyl-
propane (abbreviated as H4hamp) is the salicylaldimine derivative
with hydroxyl groups in the 3- and 30-position which contains six
potential donor atoms. The Cambridge Structural Database [1]
includes only several compounds with the above Schiff base: the
tetranuclear complex [U4(L2)2(H2L2)2(py)2O][CF3SO3]2 reported by
complexes a weak antiferromagnetic coupling was observed
between the Ni(II) and the U(IV) ions, while a ferromagnetic inter-
action was revealed between the Cu(II) and U(IV) ions [4,5]. Chaud-
hury et al. reported a rare type of all-oxido heterotrimetallic
compound [L3{(ReVO)(OCH3)}{(VVO)(OCH3)(
l-OCH3)}2]. In its crys-
tal structure the smaller N2O2 compartment of the hexadentate
Schiff base ligand is occupied by rhenium(V) whereas two vana-
dium(V) centres are accommodated in the more flexible and larger
O4 compartment. The solvent CH3OH plays a crucial role as it sup-
plies the AOCH3 donor groups, both bridging and monodentate, to
stabilize vanadium in the +5 oxidation state [6].
Herein we report syntheses, structures, spectroscopic, thermal
and magnetic properties of the new heterotrinuclear complexes
[Cu2La(H2hamp)2(NO3)2H2O]NO3ꢀ6MeOH (1), [Cu2Pr(H2hamp)2
(NO3)3]ꢀ6MeOH (2), [Cu2Nd(H2hamp)2(NO3)(MeOH)2](NO3)2ꢀH2O
(3) with the N2O4 Schiff base compartmental ligand N,N0-bis(2,3-
dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane (H4hamp).
Salmon et al. that contains a U4 tetrahedron held by a central,
l-
oxo ion and eight bridging oxygen atoms from the N2O4-donor
ligands. In the crystal structure of this compound the two Schiff
base ligands in the asymmetric unit display different conforma-
tions, either slightly curved with an uranium atom in the inner
N2O2 site or very strongly folded with an uranium atom bound to
the outer O4 site, with further bridging in both cases [2]. Salmon
et al. described also heterodinuclear CuII/NiII–UIV anionic com-
plexes [Hpy][CuL5(py)UCl3] and [Hpy][NiL5(py)UCl3], respectively.
Results of X-ray analysis show that 3d transition metal ions occupy
the smaller N2O2 cavity of the Schiff base ligand whereas uranium
atoms place the bigger O4 one. The copper(II)/nickel(II) and
uranium(IV) ions are bridged by the two oxygen atoms of the
salicylidene fragments [3]. H4hamp was also used by Ephritikhine,
Girerd et al. for the synthesis of heterotrinuclear 3d–5f–3d
2. Experimental
2.1. Materials
⇑
The chemicals: 2,3-dihydroxybenzaldehyde, 2,2-dimethyl-1,3-
propanediamine, Cu(CH3COO)2ꢀH2O, La(NO3)3ꢀ6H2O, Pr(NO3)3ꢀ5H2O,
Corresponding author.
E-mail address: beata.cristovao@poczta.umcs.lublin.pl (B. Cristóvão).
https://doi.org/10.1016/j.poly.2018.01.023
0277-5387/Ó 2018 Elsevier Ltd. All rights reserved.

226
B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
Nd(NO3)3ꢀ5H2O and CH3OH (solvent) were of analytical reagent
grade. They were purchased from commercial sources and used
as received without further purification.
Q5000 analyzer TA Instruments, New Castle, Delaware, USA, inter-
faced to the Nicolet 6700 FTIR spectrophotometer (Thermo Scien-
tific). The complex samples were put in an open platinum crucible
and heated from ambient temperature to 1000 °C. The analysis
was carried out at a heating rate of 20 °C minꢁ1 under nitrogen at
flow rate of 20 mL minꢁ1. To reduce the possibility of gasses con-
densing along the transfer line, the temperature in the gas cell and
transfer line was set to 250 and 240 °C, respectively. Gas analysis
was performed by matching the spectra against those from the spec-
trum library Nicolet TGA Vapor Phase of the software Ominic
together with the literature sources. The X-ray powder diffraction
patterns of the products of decomposition process were collected
at room temperature on an Empyrean PANanalytical automated
2.2. Synthesis of the H4hamp
The Schiff base ligand (C19H22N2O4) was synthesized by the 2:1
condensation reaction between 2,3-dihydroxybenzaldehyde (1.38
g, 10 mmol) and 2,2-dimethyl-1,3-propanediamine (0.51 g,
5
mmol) in hot methanol (50 ml) following the procedure reported
in the literature [7,8]. The compound was separated as orange nee-
dles and recrystallized twice from methanol. The empirical for-
mula and the molecular weight are C19H22N2O4 and 342.00 g/mol
respectively. Yield 84%. Analytical data (%), Calcd: C, 66.60; H,
6.43; N, 8.19. Found: C, 66.50; H, 6.30; N, 8.10.
powder diffractometer with CuKa radiation (ka = 1.54187 Å) over
the scattering angular range 2h = 20–120°. Magnetic susceptibility
measurements were performedon finely groundcrystallinesamples
over the temperature range 1.8–300 K at magnetic field 0.1 T using a
Quantum Design SQUID-VSM magnetometer. Field dependences of
magnetization were measured at 2 K in an applied field up to 5 T.
Corrections are based on subtracting the sample – holder signal
2.2.1. General procedure of preparation of complexes
The heterotrinuclear compounds 1, 2 and 3 were prepared as
follows: the solution of copper(II) acetate (Cu(OAc)2ꢀH2O 0.4 mmol,
0.0799 g) in methanol (10 mL) was added dropwise to the stirred
solution of H4hamp (0.4 mmol, 0.1368 g) in methanol (20 mL) to
produce a green coloured mixture. The reaction mixture was stir-
red for 30 min at 45 °C. Next, the freshly prepared solution of La
(NO3)3ꢀ6H2O (0.2 mmol, 0.0860 g), Pr(NO3)3ꢀ6H2O (0.2 mmol,
0.0870 g) or Nd(NO3)3ꢀ6H2O (0.2 mmol, 0.0877 g) in methanol (5
mL) was added slowly to the mixture with constant stirring and
the resulting deep green solution was stirred for another 30 min.
A small amount of precipitate that appeared was filtered off. Green
single crystals suitable for X-ray diffraction analysis were formed
at 4 °C (in a refrigerator) after several weeks.
and contribution vD estimated from the Pascal’s constants [9,10].
2.4. X-ray crystal structure determination
The X-ray diffraction intensities for H4hamp were collected at
100 K on Oxford Diffraction Xcalibur CCD diffractometer with the
graphite-monochromatized MoKa radiation (k = 0.71073 Å). Crys-
tal data for 1–3 were collected at 120 K on SuperNova X-ray diffrac-
tometer equipped with Atlas S2 CCD detector using the mirror-
monochromatized CuKa radiation (k = 1.54184 Å). All data were
collected using the scan technique, with an angular scan width
x
2.2.1.1. [Cu2La(H2hamp)2(NO3)2H2O]NO3ꢀ6MeOH (1). The empirical
formula and the molecular weight are C44H66N7O24Cu2La and
1343.04 g/mol, respectively. Yield 29%. Analytical data (%), Calcd:
C, 38.33; H, 4.71; N, 7.45; Cu, 9.67; La, 10.56. Found: C, 38.10; H,
4.60; N, 7.20; Cu, 9.50; La, 10.20.
of 1.0°. The programs CrysAlis CCD, CrysAlis Red and CrysAlisPro
[11,12] were used for data collection, cell refinement and data
reduction. The structures were solved by direct methods using
SHELXS-2013 and SHELXS-97 and refined by the full matrix least-
squares on F2 using SHELXL-2013 [13] implemented in the WinGX
software package [14] and SHELXL-97 implemented in OLEX2 [15]. All
non-hydrogen atoms with except of the two disordered nitrate N
and O atoms in complexes were refined with anisotropic displace-
ment parameters. The hydrogen atoms residing on carbon atoms
were positioned geometrically and refined applying the riding
model [CAH = 0.93–0.97 Å and with Uiso(H) = 1.2 or 1.5 Ueq(C)].
The hydrogen atom at one of the hyrdroxyl group in H4hamp is dis-
ordered over two positions: at O3 and N2 atoms. They were located
in the difference Fourier map and then refined using riding model
(with Uiso(H) = 1.5 Ueq(O) or 1.2 Ueq(N)). The other hydrogen linked
to O and N atoms in H4hamp were also found from the difference
Fourier map and refined isotropically. Some of methanol and water
molecules in 1–3 were refined isotropically, as well as the disor-
dered nitrate ion in the crystal 3. The disorder is over two positions
around inversion center with sof’s being 0.5. The crystallographic
and refinement data for this compound are summarized in the
Tables 1 and S1 (Supplementary materials).
2.2.1.2. [Cu2Pr(H2hamp)2(NO3)3]ꢀ6MeOH (2). The empirical formula
and the molecular weight are C44H64Cu2N7O23Pr and 1327.03
g/mol respectively. Yield 24%. Analytical data (%), Calcd: C, 39.79;
H, 4.82; N, 7.38; Cu, 9.58; Pr, 10.62. Found: C, 39.80; H, 4.60; N,
7.10; Cu, 9.30; Pr, 10.40.
2.2.1.3. [Cu2Nd(H2hamp)2(NO3)(MeOH)2](NO3)2ꢀH2O (3). The empiri-
cal formula and the molecular weight are C40H50Cu2NdN7O20 and
1220.21 g/mol, respectively. Yield 26%. Analytical data (%), Calcd:
C, 39.34; H, 4.10; N, 8.03; Cu, 10.42; Nd, 11.82. Found: C, 39.80;
H, 4.15; N, 7.90; Cu, 10.20; Nd, 11.60.
2.3. Methods
The contents of carbon, hydrogen and nitrogen in the complexes
were determined by elemental analysis using a CHN 2400 Perkin
Elmer analyser. The contents of copper and lanthanides were estab-
lished using ED XRF spectrophotometer (Canberra–Packard). The
FTIR spectra of compounds were recorded over the range of 4000–
400 cmꢁ1 using M-80 spectrophotometer (Carl Zeiss Jena). Samples
for FTIR spectra measurements were prepared as KBr discs. Thermal
analyses of complexes 1, 2 and 3 and the H4hamp were carried out
by the thermogravimetric (TG) and differential scanning calorime-
try (DSC) methods using the SETSYS 16/18 analyser (Setaram). The
experiments were carried out under air flow in the temperature
range of 20–1000 °C (compounds) and 20–700 °C (Schiff base) at a
heating rate of 10 °C minꢁ1. The samples 7.68 mg (1), 7.79 mg (2),
7.67 mg (3) and 7.54 mg (H4hamp) were heated in Al2O3 crucibles.
The TG–FTIR of the title compounds was recorded using the TGA
3. Result and discussion
3.1. Infrared spectra
In order to obtain some information about binding mode of the
N2O4-donor ligand to Cu(II) and Ln(III) ions the FTIR spectra of the
complexes 1–3 were compared with the spectrum of the free Schiff
base (H4hamp) (Table 2). All heterotrinuclear coordination com-
pounds show similar FTIR spectral features exhibiting a strong
band at 1620 cmꢁ1 attributable to
m
(C@Nimine), which is shifted
20 cmꢁ1 lower than that in the spectrum of the H4hamp ligand,

B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
227
Table 1
Crystal data and structure refinement details for 1–3.
Identification code
1
2
3
Empirical formula
Formula weight
T (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
44H66N7O24Cu2La
C44H64N7O23Cu2Pr
1327.03
120.0(1)
monoclinic
P21/n
C40H50N7O20Cu2Nd
1220.21
120.0(1)
monoclinic
P21/n
1343.04
120.0(1)
monoclinic
P21/n
13.1508(4)
20.1662(6)
21.4930(9)
104.022(4)
5530.2(3)
4
1.6130
7.503
13.1445(4)
20.2259(6)
21.4443(7)
104.175(3)
5527.6(3)
4
1.5945
8.275
14.9951(5)
17.8574(6)
18.2642(6)
103.726(3)
4751.0(3)
4
b (Å)
c (Å)
b (°)
V (Å)3
Z
qcalc (g cm3)
1.7058
9.989
l
(mm–1
)
F(000)
2732.2
2695.4
2447.7
Crystal size (mm)
0.35 ꢂ 0.22 ꢂ 0.2
0.35 ꢂ 0.28 ꢂ 0.25
0.3 ꢂ 0.25 ꢂ 0.08
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
68078
37633
33684
9673 [Rint = 0.0757, Rsigma = 0.0333]
9673/7/717
1.048
9980 [Rint = 0.0802, Rsigma = 0.0583]
9980/4/705
1.034
9822 [Rint = 0.0768, Rsigma = 0.0611]
9822/13/647
1.032
Final R indexes [I > 2
r
(I)]
R1 = 0.0417, wR2 = 0.1075
R1 = 0.0436, wR2 = 0.1101
1.74/ꢁ1.13
R1 = 0.0523, wR2 = 0.1385
R1 = 0.0581, wR2 = 0.1455
1.69/ꢁ1.27
R1 = 0.0601, wR2 = 0.1609
R1 = 0.0728, wR2 = 0.1809
2.40/ꢁ1.92
Final R indexes [all data]
Largest difference in peak and hole (e Åꢁ3
CCDC No.
)
1584666
1584667
1584669
(1640 cmꢁ1). It indicates a decrease in the C@N bond order due to
the coordinate bond formation between the Cu(II) ion and the
imine nitrogen lone pair of the Schiff base [16–20]. The strong peak
at about 1468 cmꢁ1, 1312–1304 cmꢁ1, 1096 cmꢁ1 and 784 cmꢁ1
[22]. The presence of a broad band at about 3400 cmꢁ1 character-
istic of m(OAH) stretching vibrations is associated with coordinated
characteristic of phenolic
m
(CAO) stretching vibration band
and/or solvated water/methanol molecules, but unfortunately it
interferes with the observation of protonated hydroxyl groups of
the organic ligand [8,16–20].
observed at 1240 cmꢁ1 for the H4hamp is observed as a doublet
in the FTIR spectra of complexes 1–3 and occurs at 1256 and
1220 cmꢁ1, indicating the involvement of the phenolic oxygen
atoms in the metal–ligand bonding [19,21]. The bands attributed
to asymmetric and symmetric stretching vibrations of the methyl
3.2. Crystal and molecular structure
group,m .
(CH3) are presented at around 2960 cmꢁ1 and 2860 cmꢁ1
In the FTIR spectra of 1–3 the characteristic frequencies of nitrate
groups acting as mono- and bidentate ligands overlap and occur
The slow crystallization of the H4hamp from methanol resulted
in formation of crystals suitable for X-ray structural analysis. Its
molecular structure is displayed in Fig. 1. The structure of N,N’-
Table 2
Selected spectroscopic data of the H4hamp, CuII–LaII–CuII (1), CuII-PrIII–CuIII (2) and CuII-NdIII–CuII (3).
H4hamp
1
2
3
Proposed assignments
–
3424 m
–
2956 w
–
3432 w
–
2960 w
–
3436 w
–
m
m
m
m
m
m
m
(OAH) +
m
(CAH)
3204 m
–
–
1640 vs
1548 m
1464 s
1384 m
1352 m
–
(OAH) M
(CH3)as
(CH3)s
(C@N)
(C@C)
m(NAH)
2956 w
2860 w
1620 vs
1568 m
1468 s
1384 s
–
1304 s
1256 s
1220 m
1168 w
1096 w
1048 w
–
1620 vs
1568 m
1468 vs
1384 s
–
1308 s
1256 s
1220 s
1168 w
1096 w
1048 w
972 w
–
864 m
784 w
740 s
648 m
620 w
532 w
–
1620 vs
1568 m
1468 s
1384 w
–
1312 s
1256 s
1220 s
1168 w
1096 w
1044 w
972 w
–
864 m
784 w
740 s
648 m
620 w
536 w
–
(C@C) +
m
(NAO)comp.
(CCC))
sc(CAH) +
d(OAH)
m
m
m
m
m
(CAN) +
(CAO)
(CAO) + d(OAH)
(CAC) + tw(CAH)
x(CAH) + m(NAO)
–
1240 vs
1184 vs
1080 w
1056 w
–
896 w
848 m
784 w
740 vs
644 w
612 w
–
d (CAH) + m(NAO)
skeletal
q
(CAH) + CH2 + d(CCC)
(OAH)
d(CAN@C)
–
c
864 m
784 w
740 s
628 w
612 w
536 w
524 w
504 w
364 w
c
c
(CAH) +
(CAH)
m(NAO)
d(C@C) + ring deform.
ring deform.
m(MAO)
c(CAH)
c(CAH)
m(MAN)
500 w
–
496 m
364 w
500 s
364 w
vs – very strong, s – strong, m – medium, w – weak, br – broad,
deformation out of plane, as – asymmetric, sym – symmetric.
m – stretching, d – deformation in plane, sc – scissoring, x – waggining, tw – twisting, q – rocking, c –

228
B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
Fig. 1. ORTEP view with the atom numbering scheme of H4hamp. Displacement ellipsoids are drawn at the 30% probability level. The site-occupation factors of the
disordered H atom is 0.58(6) at hydroxy O3 atom and 0.42(6) at N2 atom.
bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane
has been previously reported by Aguiari et al. [7] and Bermejo et al.
[8]. Both X-ray measurements of single crystals were made at room
temperature. Aguiari and co-workers synthesized crystals of
H4hamp where one half contained a protonated nitrogen atom
(zwitterionic form) whereas in the second dihydroxybenzaldimine
moiety the hydrogen atom was located on the oxygen atom. The
CAN distances are practically identical (Table S2) and indicates
double character of these bonds [7]. The compound described by
Bermejo and co-workers crystallizes in the phenol-imine/keto-
amine form [8]. The X-ray analysis of H4hamp prepared by us
was performed at 100 K. Similar to previously described structures
the N2O4-ligand has a non-planar conformation. The dihedral
angles between the plane formed by two aromatic rings (C1AC6/
C14AC19) is 47.6(1)°. The C7AN1 (1.296(3) Å) and C2AO1 (1.295
(2) Å) lengths have intermediate values between single and double
CAO (1.362 Å and 1.222 Å) and CAN (1.339 and 1.279 Å) bond dis-
tance [23]. The shortened C2AO1 distance and the slightly longer
C7AN2 bond indicates that in this half of the molecule the stabi-
lization of the zwitterionic form occurs. The similar value of related
bonds for the zwitterionic forms of Schiff base was reported earlier
[24–27]. In the second dihydroxybenzaldimine moiety the N2AC13
and C15AO3 bonds are equal to 1.283(3) and 1.336(3) Å, respec-
tively. This can indicate that the hydrogen atom is delocalized
between the two positions, i.e., partly bound to oxygen and nitrogen
atoms (Fig. S1). The position of hydroxyl and amine H-atom was
determined from the difference Fourier map and their occupancies
were refined complementarily. The site occupancy factors for H
atoms attached to O3/N2 atoms were 0.58(6)/0.42(6).
isostructural. The main differences between 1, 2 and 3 originate
in the nature of the polynuclear species (cationic (1, 3) versus neu-
tral (2)), the kind and amount of solvent molecules in the outer
coordination sphere and the type of ligands coordinated to
copper(II). The structures of 1–3 presented in Figs. 2–4 show the
that the coordination modes of the Schiff base ligands toward the
lanthanide(III) and copper(II) ions are the same. The central LnIII
ion is surrounded by two Cu(H2hamp) units, so that the LnIII and
CuII ions are linked by phenoxido bridging groups. In the all com-
plexes 1–3 the LnIII ion is ten-coordinated by eight atoms origi-
nated from two H2hamp ligands and two O atoms coming from
the bidentate (g
2-chelating) nitrate ion (Fig. S2). The external
hydroxyl groups of the Schiff base ligands closing the outer com-
partment O2O2 are undeprotonated and they are involved in the
intra- and intermolecular hydrogen bonds (Table S3). The LnAO
bond lengths vary from ca. 2.47 Å for phenoxy groups presented
inside the coordination cavity of the Schiff base ligand, through
the protonated hydroxy groups closing this compartment up to
ca. 2.68 Å for less coordinated nitrate groups (Table 3). The five-
coordinated CuII ions are in a square pyramidal environment, the
N2O2 atoms of the Schiff base ligands defining the basal plane with
the CuAN and CuAO bond distances in the range of 1.957(5)–1.997
(3) Å and 1.923(3)–1.979(3) Å, respectively (Table 3) while oxygen
atoms coming from different species: aqua and nitrate ion (1),
nitrate ions (2) and methanol molecules (3), respectively occupy
the apical position (Fig. S2). The intramolecular separations
Cu1. . .Ln1/Cu2. . .Ln1 and Cu1. . .Cu1/Cu2. . .Cu2 are within the nor-
mal range of values for similar heteronuclear CuII–LnIII complexes,
being ca. 3.62–3.68 Å and 7.11–7.18 Å, respectively [28–35].
In order to check the influence of the kind of substituents in the
benzene ring on the structure and properties of the coordination
Single-crystal X-ray studies of the coordination compounds 1–3
revealed that [Cu2La(H2hamp)2(NO3)2H2O]NO3ꢀ6MeOH (1), [Cu2Pr
(H2hamp)2(NO3)3]ꢀ6MeOH (2), [Cu2Nd(H2hamp)2(NO3)(MeOH)2]
(NO3)2ꢀH2O (3) where H2hamp = C19H20N2O4 is a dianion of N,N0-
bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane
crystallize in the monoclinic space group P21/n. Details for the
structure solution and refinement are summarized in Table 1.
The selected bond distances and angles are listed in Tables 3 and
4. Although compounds 1–3 crystallize in the same space group
and the crystal unit cell dimensions are similar they are not
compounds some structural parameters (CuAN, CuAOphen
LnAOphen, LnAOhydroxy, Cuꢀ ꢀ ꢀLn) of the obtained complexes 1–3
with H4hamp were compared with ones (CuAN, CuAOphen
,
,
LnAOphen, LnAOmethoxy/ethoxy, Cuꢀ ꢀ ꢀLn) of chosen heteronuclear
CuIIALnIII compounds synthesised with N,N0-bis(2-hydroxy-
3-methoxybenzylidene)-1,3-diamino-2,2-dimethylpropane
N,N0-bis(2-hydroxy-3-ethoxybenzylidene)-1,3-diamino-2,2-dimethyl-
propane (Tables and S4). The aforementioned ligands are
or
3

B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
229
Table 3
Bond lengths and selected intramolecular distances for crystals 1–3.
Atom
Atom
Length (Å)
Atom
Atom
Length (Å)
Atom
Atom
Length (Å)
1
2
3
La1
La1
La1
La1
La1
La1
La1
La1
La1
La1
Cu1
Cu1
Cu1
Cu1
Cu1
Cu2
Cu2
Cu2
Cu2
Cu2
Cu1
Cu2
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O1
O2
N1
N2
O20
O5
O6
N3
N4
O15
La1
La1
2.520(3)
2.548(3)
2.572(3)
2.595(3)
2.520(3)
2.552(2)
2.569(3)
2.521(3)
2.654(3)
2.677(3)
1.930(3)
1.963(3)
1.987(3)
1.968(3)
2.736(5)
1.979(3)
1.944(3)
1.982(3)
1.997(3)
2.449(3)
3.6679(6)
3.6776(5)
Pr1
Pr1
Pr1
Pr1
Pr1
Pr1
Pr1
Pr1
Pr1
Pr1
Cu1
Cu1
Cu1
Cu1
Cu1
Cu2
Cu2
Cu2
Cu2
Cu2
Cu1
Cu2
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O1
O2
N2
N1
O14
O5
O6
N3
N4
O20
Pr1
Pr1
2.479(3)
2.514(3)
2.526(4)
2.498(4)
2.492(3)
2.518(3)
2.535(3)
2.560(4)
2.627(4)
2.619(4)
1.979(3)
1.942(3)
1.990(4)
1.979(4)
2.432(3)
1.923(3)
1.960(3)
1.982(4)
1.962(4)
2.785(4)
3.6393(7)
3.6403(6)
Nd1
Nd1
Nd1
Nd1
Nd1
Nd1
Nd1
Nd1
Nd1
Nd1
Cu1
Cu1
Cu1
Cu1
Cu1
Cu2
Cu2
Cu2
Cu2
Cu2
Cu1
Cu2
O1
O2
O3
O4
O5
O6
O7
O8
2.478(4)
2.474(4)
2.526(4)
2.489(4)
2.525(4)
2.473(4)
2.539(4)
2.496(4)
2.665(5)
2.555(5)
1.926(5)
1.951(4)
1.974(6)
1.969(6)
2.771(6)
1.963(4)
1.924(4)
1.957(5)
1.975(6)
2.680(6)
3.617(1)
3.635(1)
O9
O10
O1
O2
N1
N2
O12
O5
O6
N3
N4
O13
Nd1
Nd1
Table 4
Bond angles for 1–3.
Atom
Atom
Atom
Angle (°)
Atom
Atom
Atom
Angle (°)
Atom
Atom
Atom
Angle (°)
1
2
3
Cu1
Cu1
Cu2
Cu2
O1
O2
O5
O6
La1
La1
La1
La1
110.3(1)
108.1(1)
109.1(1)
109.0(1)
Cu1
Cu1
Cu2
Cu2
O1
O2
O6
O5
Pr1
Pr1
Pr1
Pr1
108.9(1)
108.8(1)
108.2(1)
110.4(1)
Cu1
Cu1
Cu2
Cu2
O1
O2
O5
O6
Nd1
Nd1
Nd1
Nd1
109.8(2)
109.1(2)
107.5(2)
110.9(2)
Fig. 2. Molecular structure with atom numbering scheme of CuII–LaIII–CuII (1). The outer coordination sphere solvent molecules were omitted for clarity.
differentiated by the presence in benzene ring the various substituent
at the meta position (AOH or AOCH3/AOC2H5). As shown in the
Scheme 1 and in the Table S4 all compared complexes consist of
diphenoxo-bridged heterometallic cores in which 3d metal ion is sit-
uated in the smaller N2O2 compartment of the Schiff base ligand,
while the 4f ion is present in the larger and open O2O2 [O(phenoxo)2
O(methoxy/ethoxy/hydroxy)2] one. The CuAN and CuAOphen bond distances
are similar and range from 1.92 to 1.99 Å (complexes 1–3) and from
1.95 to 2.00 Å (compounds placed in the Table S4). The LnAOphen
bond distances from the phenolato oxygen atoms range from 2.47
to 2.55 Å (complexes 1–3) and from 2.33 to 2.43 Å (compounds
placed in the Table S4) are shorter than those from the hydroxy/meth-
oxy/ethoxy oxygens LnAOhydroxy/methoxy/ethoxy range from 2.49 to 2.60
Å (complexes 1–3) and 2.43 to 2.65 Å (compounds placed in the
Table S4), respectively. The intramolecular separation CuꢀꢀꢀLn is
ꢃ3.62–3.68 Å (complexes 1–3) and ꢃ3.44–3.52 Å (compounds placed

230
B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
Fig. 3. Molecular structure with atom numbering scheme of CuII–PrIII–CuII (2). The outer coordination sphere solvent molecules were omitted for clarity.
Fig. 4. Molecular structure with atom numbering scheme of CuII–NdIII–CuII (3). The outer coordination sphere solvent molecules were omitted for clarity.
in the Table S4). In the benzene ring the hydroxy as well as aloxy
groups are electron donating substituents so they have similar influ-
ence on the structural parameters of the compared complexes. The
structure of CuII–LnIII coordination compounds depends also on the
oxophilicity of the lanthanides(III), the preference of the copper(II)
ion for nitrogen atoms, the degree of deprotonation of the ligands,
the stoichiometry of the used reagents, kind of used solvents etc. In
the analysed complexes nitrato anions contributing to the electroneu-
trality and also to the completion of the coordination sphere of the 4f
and 3d metal ions as a monodentate or a bidentate chelating ligand
[28–35].
which is characteristic of the melting process. The melting point
observed on the DSC curve is about 175 °C and the enthalpy of
fusion equals 27.75 kJ molꢁ1. The DSC peak is sharp which indi-
cates that the ligand is a crystalline, pure substance. As shown in
Fig. 5 and Figs. S4–S6 the complexes 1–3 are stable at room tem-
perature. The recorded TG curves of 1–3 display very similar mass
loss patterns. The samples of compounds 1–3 during heating up to
ca. 190 °C undergo desolvation process. The complex 1 in the first
step loses one methanol and water molecules (mass loss found
3.20%, calculated 3.70%) while the second one is mainly related
to the further partial release of methanol molecules (ca. two mole-
cules). The remaining solvents are removed together with nitrate
ions above 200 °C. In the case of the compound 2 the first mass loss
9.40% corresponds to the loss of four methanol molecules per for-
mula unit (calculated 9.40%). Similarly to the complex 1, the two
methanol molecules are removed at higher temperature (above
200 °C) together with nitrate ions. Overall found mass loss for six
methanol molecules and three nitrate ions is 29.00% whereas the
calculated one is equal to 28.50%. During the heating of 3 the
two-step desolvation process connected with loss molecules of
3.3. Thermal properties
In order to examine the thermal behaviour and the stability of
the H4hamp and CuII–LnIII–CuII coordination compounds 1–3 the
TG, DTG and DSC curves were recorded in air atmosphere. The
N2O4-donor ligand is stable up to 170 °C (Fig. S3). During further
heating of the sample an endothermic effect is observed on the
DSC curve. This effect is connected with the negligible mass loss,

B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
231
Scheme 1. Schematic representation of the synthesis and structural units of the diphenoxo bridged CuII–LnIII–CuII complexes.
the DSC curves with the maximum at ꢃ98 °C (1), ꢃ112 °C (2),
ꢃ106 °C and ꢃ136 °C (3). The values of the enthalpy of the above
processes are 58.79 kJ molꢁ1 (1), 105.08 kJ molꢁ1 (2) and 76.85 kJ
molꢁ1 (3), respectively. The decomposition process of the CuII–
LnIII–CuII complexes 1–3 is intricate and it was not possible to dis-
tinguish intermediate solid products. The final products (mixtures
of metal oxides CuO and CuLn2O4 Ln = La, Pr, Nd) obtained during
thermal decomposition of 1–3 in air were calculated from TG
curves and experimentally verified by X-ray diffraction powder
patterns. The percentages 24.50% (1), 25.50% (2), 25.90% (3) calcu-
lated from TG curves at about 700 °C are coincide fairly with the
theoretical values 25.42% (1), 24.82% (2), 26.82% (3).
3.4. Magnetic properties
The magnetic properties of heteronuclear CuII–LnIII compounds
are governed by three factors: the thermal population of the Stark
components of LnIII, the CuIIꢀ ꢀ ꢀCuII interactions (including inter-
molecular interaction) and the CuIIꢀ ꢀ ꢀLnIII interactions. Tempera-
ture-dependent molar susceptibility measurements of randomly
oriented crystalline samples of CuII–LaIII–CuII (1), CuII–NdIII–CuII
(2) and CuII–PrIII–CuII (3) were carried out in an applied magnetic
field of 0.1 T over the temperature range 1.8–300 K. The Fig. 7
Fig. 5. TG curves of thermal decomposition of complexes 1–3 in air.
methanol and water is observed (overall mass loss found 8.50%,
calculated 8.20%). These results are also confirmed by the TG-FTIR
analysis. The recorded FTIR spectra of evolved gas phase for the
complexes 1–3 (Figs. 6 and S7, S8) show that water and methanol
are the main products released during this stage. The characteristic
vibration bands in the wavenumber ranges 4000–3400 cmꢁ1 and
2060–1260 cmꢁ1 correspond to stretching and deforming vibra-
tions of H2O molecules, whereas the bands associated with the
presence of CH3OH are observed at 3368 cmꢁ1, 1307 cmꢁ1 and
1095 cmꢁ1, respectively [19]. The desolvation process of the com-
pounds 1–3 is accompanied with small endothermic effect seen on
shows the
susceptibility and T is the absolute temperature). At a high temper-
ature region, the MT value approached the theoretical values.
For CuII–LaIII–CuII (1) the experimental
MT is equal to 0.730
v
MT and vꢁM1 versus T plots (vM is the molar magnetic
v
v
cm3 molꢁ1 K at 300 K. This value is close to the theoretically calcu-
lated one 0.750 cm3 molꢁ1 K by the Eq. (1) for two uncorrelated
CuII (3d9, S = ½) ions, since no contribution is expected from the
nonmagnetic LaIII ion (4f 0, S = 0).

232
B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
Fig. 6. FTIR spectra of gaseous products evolved during the desolvation process of 1 recorded at 83, 163 and 196 °C.
v
MT ¼ ðNb2=3kÞ2gC2uSCuðSCu þ 1Þ
ð1Þ
v
MT ¼ ððNb2=3kÞ½2gC2uSCuðSCu þ 1Þ þ gL2nJLnðJLn þ 1ÞꢄÞ
ð2Þ
where N is Avogadro constant, b is the Bohr magneton and k is
Boltzman’s constant. In this equation gLn is the g factor of the
ground J terms of LnIII and is expressed as:
where N is Avogadro constant, b is the Bohr magneton and k is
Boltzman’s constant.
As the temperature decreases the
vMT product remains almost
unchanged in magnitude until 1.8 K. In 1 the intramolecular
Cu1. . .Cu2 distance of 7,1813(8) Å is relatively large and may pre-
clude any significant magnetic interactions between the copper
centers in the heterotrinuclear unit. The magnetization versus field
curve of 1 at 2 K is depicted in Fig. 8. The measurement shows a
saturation value of ca. 1.9 mB, which is the expected value for two
independent S = 1/2 system with g = 2.
3
2
SðS þ 1Þ ꢁ LðL þ 1Þ
2JðJ þ 1Þ
gLn
¼
þ
ð3Þ
Similarly for 3 the experimental value 2.02 cm3 molꢁ1 K at 300
K is close to the calculated value equal to 2.39 cm3 molꢁ1 K (the
equation (1)) for one NdIII (4f 3, J = 9/2, S = 3/2, L = 6, I9/2) and
4
two CuII (3d9, S = ½) noninteracting metal ions.
In the case of 2 the experimental value of vMT at room temper-
ature equal to 2.23 cm3 molꢁ1 K corresponds to the value 2.35 cm3
molꢁ1 K theoretically calculated (Eq. (2)) for one PrIII (4f 2, J = 4, S =
1, L = 5, 3H4) and two CuII (3d9, S = ½) isolated paramagnetic metal
ions.
Fig. 7. Temperature dependence of experimental
LaIII–CuII (1) CuII–PrIII–CuII (2) and CuII–NdIII–CuII (3).
v
MT and vꢁM1 versus T for CuII–
Fig. 8. Field dependence of the magnetization for complexes 1, 2 and 3 at 2 K.

B. Cristóvão et al. / Polyhedron 144 (2018) 225–233
233
As depicted in Fig. 7 the values of
v
MT decrease by lowering of
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or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at https://doi.
org/10.1016/j.poly.2018.01.023.
temperature to 0.52 cm3 molꢁ1 K for 2 and 0.22 cm3 molꢁ1 K for 3,
respectively in 1.8 K. This decrease could be caused by crystal field
effect, as well as the antiferromagnetic interactions between
neighboring 3d and 4f metal ions. Unfortunately, the quantitative
description of the magnetic properties of heterometallic complexes
containing lanthanide(III) ions is not an easy task because of the
ligand-field effect and spin–orbit coupling of the LnIII ion [36,37].
To confirm the nature of the ground state of 2 and 3, we investi-
gated the variation of the magnetization, M, with respect to the
field, at 2 K (Fig. 8). The compounds do not reach the saturation
in the applied field range and magnetization in 5 T is equal to
1.90 mB for 2 and 1.00 mB for 3. This further indicates that studied
CuI2ILnIII systems display an antiferromagnetic coupling. In fact, this
results are in good agreement with a theoretical model of Kahn
[37] according to the LnIII ions with f1–f6 configurations should exhi-
bit antiferromagnetic coupling.
References
[1] A.F.H. Allen, Acta Crystallogr. Sect. B 58 (2002) 380.
[2] L. Salmon, P. Thuéry, M. Ephritikhine, Polyhedron 25 (2006) 1537.
[3] L. Salmon, P. Thuéry, M. Ephritikhine, Polyhedron 26 (2007) 645.
[4] T. Le Borgne, E. Riviére, J. Marrot, J.-J. Girerd, M. Ephritikhine, Angew. Chem.,
Int. Ed. 39 (9) (2000) 1647.
[5] T. Le Borgne, E. Riviére, J. Marrot, P. Thuéry, J.-J. Girerd, M. Ephritikhine, Chem.
Eur. J. 8 (4) (2002) 773.
[6] K. Bhattacharya, M. Maity, S.M.T. Abtab, M.C. Majee, M. Chaudhury, Inorg.
Chem. 52 (2013) 9597.
[7] A. Aguiari, E. Bullita, U. Casellato, P. Guerriero, S. Tamburini, P.A. Vigato, Inorg.
Chim. Acta 202 (1982) 157.
[8] M.R. Bermejo, M.I. Fernandez, E. Gomez-Forneas, A. Gonzalez-Noya, M.
Maneiro, R. Pedrido, M.J. Rodriguez, Eur. J. Inorg. Chem. (2007) 3789.
[9] O. Kahn, Molecular Magnetism, VCH Publishers Inc, New York, 1993.
[10] G.A. Bain, J.F. Berr, J. Chem. Educ. 85 (2008) 532.
[11] Oxford Diffraction Xcalibur CCD System, CRYSALIS Software System Version
1.171, Oxford Diffraction Ltd., Abingdon, Oxfordshire, UK, 2009.
[12] CrysAlisPro Software System, Version 1.171.37.34, Agilent Technologies,
Oxford, UK, 2014.
[13] M. Sheldrick, Acta Cryst. A 64 (2008) 112.
[14] L.J. Faruggia, J. Appl. Crystallogr. 32 (1999) 837.
[15] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H.J. Puschmann, Appl.
Cryst. 42 (2009) 339.
[16] G.-B. Li, X.-J. Hong, Z.-G. Gu, Z.-P. Zheng, Y.-Y. Wu, H.-Y. Jia, J. Liu, Y.-P. Cai,
Inorg. Chim. Acta 392 (2012) 177.
[17] A.-N.M.A. Alaghaz, B.A. El-Sayed, A.A. El-Henawy, R.A.A. Ammarb, J. Mol.
Struct. 1035 (2013) 83.
[18] R.K. Dubey, P. Baranwal, A.K. Jha, J. Coord. Chem. 65 (2012) 2645.
[19] A. Bartyzel, J. Coord. Chem. 66 (2013) 4292.
[20] A. Gutiérrez, M.F. Perpiñán, A.E. Sánchez, M.C. Torralba, V. González, Inorg.
Chim. Acta 453 (2016) 169.
[21] R. Takjoo, A. Hashemzadeh, H.A. Rudbari, F. Nicolò, J. Coord. Chem. 66 (2013)
345.
4. Conclusion
The X-ray crystal structure analysis of 1–3 revealed that the
coordination modes of the Schiff base ligands toward the lan-
thanide(III) and copper(II) ions are the same. In the CuII–LnIII–CuII
core the Ln(III) ion is ten-coordinated whereas the coordination
number of copper(II) ions is equal to five. The main differences
between 1, 2 and 3 originate in the nature of the polynuclear spe-
cies (cationic (1, 3) versus neutral (2)), the kind and amount of sol-
vent molecules in the outer coordination sphere and the type of
ligands coordinated to copper(II). The desolvation process of 1–3
is consistent with the lose molecules of methanol and water
(1, 3) and only methanol (2). The interaction between neighboring
CuII and PrIII/NdIII ions is antiferromagnetic.
[22] B. Cristóvão, J. Kłak, B. Miroslaw, J. Coord. Chem. 67 (2014) 2728.
[23] F.H. Allen, O. Kennard, D.G. Watson, L.A. Brammer, G. Orpen, J. Chem. Soc.
Perkin Trans., 2 (1987) S1.
Acknowledgements
[24] A.A.B.C. Júnior, G.S.G. De Carvalho, L.F. Marques, C.C. Corrêa, A.D. Da Silva, F.C.
Machado, Acta Cryst. C 69 (2013) 934–936.
[25] K. Ouari, M. Merzouguia, L. Karmazin, Acta Cryst., E 71 (2015) 1010.
[26] G. Alpaslan, M. Macit, A. Erdönmez, O. Büyükgüngör, J. Mol. Struct. 997 (2011)
70.
[27] A. Bartyzel, Polyhedron 134 (2017) 30.
[28] T. Kajiwara, M. Nakano, K. Takahashi, S. Takaishi, M. Yamashita, Chem. Eur. J.
17 (2011) 196.
[29] J.P. Costes, F. Dahan, A. Dupuis, J.P. Laurent, New J. Chem. 22 (1998) 1525.
[30] J.P. Costes, F. Dahan, A. Dupuis, Inorg. Chem. 39 (2000) 165.
[31] J.P. Costes, F. Dahan, A. Dupuis, J.P. Laurent, Inorg. Chem. 36 (1997) 3429.
[32] G. Novitchi, J.P. Costes, B. Donnadieu, Eur. J. Inorg. Chem. (2004) 1808.
[33] T. Ishida, R. Watanabe, K. Fujiwara, A. Okazawa, N. Kojima, G. Tanaka, S. Yoshii,
H. Nojiri, Dalton Trans. 41 (2012) 13609.
The X-ray crystal structure determination of complexes 1–3
was carried out with the equipment purchased thanks to the finan-
cial support of the European Regional Development Fund in the
framework of the Operational Program Development of Eastern
Poland 2007–2013 (Contract No. POPW.01.03.00-06-009/11-00,
equipping the laboratories of the Faculties of Biology and Biotech-
nology, Mathematics, Physics and Informatics, and Chemistry for
studies of biologically active substances and environmental
samples).
[34] T. Kajiwara, K. Takahashi, T. Hiraizumi, S. Takaishi, M. Yamashita, Polyhedron
28 (2009) 1860.
Appendix A. Supplementary data
[35] J.P. Costes, F. Dahan, W. Wernsdorfer, Inorg. Chem. 45 (2006) 5.
[36] G. Li, C.A. Jones, V.H. Grassian, S.C. Larsen, J. Catal. 234 (2005) 401.
[37] A.J. Blake, V.A. Cherepanov, A.A. Dunlop, C.M. Grant, P.E.Y. Milne, J.M. Rawson,
R.E.P. Winpenny, J. Chem. Soc. Dalton Trans. (1994) 2719.
CCDC 1584666–1584669 contains the supplementary crystallo-
graphic data for H4hamp and its complexes 1–3. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/re-
trieving.html, or from the Cambridge Crystallographic Data Centre,