DOI: 10.1002/zaac.201500016Ln = Gd, Ce Complexes with 2,6-Bisacetobenzoylpyridine Keywords: Lanthanide complexes; Trinuclear complexes; d-f Mixed metal complexes; β-Diketonate; X-ray str
Trang 1DOI: 10.1002/zaac.201500016
Ln = Gd, Ce) Complexes with 2,6-Bis(acetobenzoyl)pyridine
Keywords: Lanthanide complexes; Trinuclear complexes; d-f Mixed metal complexes; β-Diketonate; X-ray structure
Abstract One-pot reactions of 2,6-bis(acetobenzoyl)pyridine (H2L)
with a mixture of LnCl3 (Ln = Ce, Gd) and Ni(CH3COO)2(ratio 2:1:2)
in CH2Cl2/MeOH in the presence of a supporting base
like Et3N give trinuclear complexes with the general composition
[Ni2Ln(L)2(CH3COO)3(MeOH)2/3] (1) in high yields Trinuclear
[Ni2Ln(L)2(PhCOO)3(MeOH)2] (2) complexes are formed when
sim-ilar reactions are performed starting from NiCl2, and benzoic acid
Introduction
Heteronuclear complexes comprising 3d-4f metal ions have
attracted great interests due to their intriguing physicochemical
properties such as magnetism[1] or photoluminescence.[2]
Ra-tional synthesis of such complexes is commonly done by using
ligand systems containing coordination sites with different
do-nor atoms and chelating abilities Among these systems,
2,6-bis(acetoacetyl)pyridines (H2LR) are the most frequently used
ligands They have three metal binding sites, one central
2,6-diacylpyridine site suitable for lanthanide binding and two
ter-minal 1,3-diketonate sites favorable for transition metal
bind-ing.[3,4] Some series of discrete trinuclear 3d-4f [MIILnIIIMII]
mixed-metal complexes, where MIIis NiII,[5]CoII,[6]CuII,[7]or
ZnII [8] have been prepared In all of the reported complexes,
the three metal ions are chelated by two dinegative
pyridine-2,6-bis(β-diketonato) ligands, which give the
thermo-dynamically stable [MIILnIIIMII(LR)2]3+ framework The
[MIILnIIIMII(LR)2(NO3)n](NO3)3–n where nitrates can act as
counterions and also as auxiliary ligands.[4–8]
* Prof Dr H H Nguyen
Fax: +84-4382-41140
E-Mail: nguyenhunghuy@hus.edu.vn
* Prof Dr T N Trieu
E-Mail: trieuthinguyet@yahoo.com.vn
[a] Department of Chemistry
Hanoi University of Science
Le Thanh Tong str.19
Hanoi, Vietnam
[b] Institute of Chemistry and Biochemistry
Freie Universität Berlin
Fabeckstrasse 34–36
14195 Berlin, Germany
(PhCOOH) is added subsequently Under the same conditions, reac-tions with the corresponding cobalt(II) salts result in the formation
of a neutral [Co8(μ3-O)2(L)6] complex, which has a bis(triple-helical)
structure The cobalt(II) analogues to compounds 1 and 2, however,
can be synthesized by a pre-treatment of the lanthanide salts with H2L and subsequent addition of the cobalt salts, and benzoic acid (in the
case of 2).
The [MIILnIIIMII(LR)2]3+skeletons are expected to be versa-tile building blocks for supramolecules or coordination poly-mers due to (i) their high thermodynamic stability, which gives access to rational syntheses of the supramolecules by connect-ing these blocks with bi-functional linkers, (ii) their planar structure which allows convenient assembling, and (iii) the large variety of coordination sites, which are available with
LnIIIand MIIions Surprisingly, there are hitherto only a few papers dealing with such compounds.[6,8,9]
In the presented work, we report the syntheses and structures of some neutral, trinuclear {NiIILnIIINiII} and {CoIILnIIICoII}complexes with 2,6-bis(acetobenzoyl)pyridine (H2L, Scheme 1) using acetate and benzoate as co-ligands The obtained complexes provide examples other than their nitrate congeners for studies of their physicochemical properties and represent trinuclear prototype compounds for tailored supra-molecules with bridging bis-carboxylato ligands, the synthesis,
of which is planned for the future.
Scheme 1 The ligand H2L used in this work
Trang 2Scheme 2 Reactions of H2L with Ni(CH3COO)2and LnCl3.
Results and Discussion
H2L readily reacts with a mixture of Ni(CH3COO)2
and LnCl3 in MeOH/CH2Cl2 at ambient temperature Yellow,
crystalline solids of trinuclear complexes with the
composition [Ni2Gd(L)2(CH3COO)3(MeOH)2] (1a) and
[Ni2Ce(L)2(CH3COO)3(MeOH)3] (1b) were isolated in high
yields (Scheme 2) Addition of a supporting base such as Et3N
accelerates the formation of the products The resulting
com-plexes are well soluble in DMSO or DMF, but only slightly
soluble in CH2Cl2or CHCl3and almost insoluble in alcohols.
The ESI+ mass spectra of complexes 1a and 1b show main
peaks at m/z = 1130.09 and 1112.13, respectively,
correspond-ing to [Ni2Ln(L)2(CH3COO)2]+ fragments A less intense
peak (about 5 % of the base peak) in the spectrum of
the cerium compound at m/z = 1172.02 can be assigned to
[Ni2Ce(L)2(CH3COO)3+ H]+ The fact that no signals of
spe-cies with coordinated methanol can be detected refers to the
only weak coordination of the solvent ligands The IR spectra
of the nickel complexes were taken from carefully
vacuum-dried samples They exhibit no absorption bands of OH
stretches, what reflects the deprotonation of the ligands.
Additionally, the shift of the ν(C=O) bands from 1620 cm–1in
H2L to the region below 1600 cm–1 indicates the formation
of β-diketonato chelate rings Two different absorptions of
1590 cm–1 were previously reported for the trinuclear
[Ni2Ln(LMe)2(NO3)3] complexes, where H2LMe is
2,6-bis(acetoacetyl)pyridine.[5]In the IR spectra of 1, the two
ab-sorptions are slightly bathochromically shifted compared to
those of [Ni2Ln(LMe)2(NO3)3] While one is a sharp strong
ab-sorption around 1600 cm–1, the other is observed as a shoulder
at about 1580 cm–1 The C=O stretching bands of the acetato
ligands appear as broad absorptions with very high intensity at
1570 cm–1 Consequently, they overlap with the second
ab-sorption bands of the ν(C=O) vibrations of β-diketonato rings.
The relatively low frequencies of ν(C=O) absorptions of the
acetato ligands indicate that both of their oxygen atoms are
coordinated.[10]
Crystals of the complexes 1 were obtained by slow
evapora-tion of the reacevapora-tion mixtures They are stable in the mother
solutions, but quickly turn to yellow powders by losing
sol-vents when they run dry An ellipsoid representation of the
molecular structure of 1a is shown in Figure 1 Selected bond
lengths and angles are given in Table 1 The quality of the
single crystals of the cerium complex 1b was not fully
satisfac-tory, so that the corresponding structure determination [space
group P21, a = 10.174(1) Å, b = 23.865(2) Å, c = 11.286(1) Å,
β = 111.12(1)°, V = 2556.1(4) Å3] could only be refined with
isotropic thermal parameters and converged at an R1value of
12 % Thus, a detailed discussion of the bond lengths and angles of this compound shall not be done here Nevertheless, its composition as a trinuclear Ni/Ce/Ni complex can be de-rived from the available data unambiguously Figure 2 depicts the molecular structure of the product, which shows some re-markable differences in contrast to the gadolinium compound
1a.
Figure 1 Ellipsoid representation of the molecular structure of 1a.
Hydrogen atoms are omitted for clarity Thermal ellipsoids represent
50 percent probability Hydrogen bonds were found: H bond / d(D–
H) / d(H···A) / d(D···A) /Å: O7–H7···O6 / 0.87 / 1.77 / 2.58(1);
O8–H8···O1#1 / 0.87 / 1.96 / 2.794(7) Symmetry equivalent #1 : –1+x,+y,+z
Figure 2 Molecular structure of 1b Hydrogen atoms are omitted for
clarity
Both 1a and 1b reveal trinuclear {NiLnNi(L)2}3+ cores, which are similar to the series of trinuclear complexes
{MIILnMII) with 2,6-bis(acetoacetyl)pyridine ligands.[5–8]Two
L2–ligands bind each two NiIIions through the 1,3-diketonato
sites and the LnIIIions through the 2,6-diacetylpyridine sites.
This results in nearly planar {Ni2Ln(L)2}3+ skeletons, which
Trang 3Table 1 Selected bond lengths /Å and angles /° in [Ni2Gd(L)2(CH3COO)3(MeOH)2] (1a), [Ni2Gd(L)2(PhCOO)3(MeOH)2] (2a),
[Ni2Ce(L)2(CH3COO)3(MeOH)(H2O)] (2b) and [Co2Ce(L)2(PhCOO)3(MeOH)(H2O)] (5b) The same atomic labeling schemes were used for all
molecules
Bond lengths
Angles
consist of N2O4 hexagonal bases for the LnIII ions and O4
square-planar bases for the NiIIions There are three additional
acetato ligands bonded to central metal atoms, including two
bidentate ligands and one unidentate ligand In the molecular
structure of 1a (Figure 1), two acetates act as bridges between
the gadolinium and the nickel ions, while the third one is
uni-dentate bonded to GdIII Also in the molecular structure of 1b
(Figure 2), the two bidentate acetates are located above the
{Ni2Ln(L)2}3+plane, but only one of them is a bridging ligand
between CeIIIand one of the NiIIions, whereas the second one
exclusively binds to the central CeIIIion The unidentate
acet-ate ligands are coordinacet-ated to the lanthanides below the
{Ni2Ln(L)2}3+plane, which is defined by the chelating ligands.
Thus, CeIIIand GdIIIshow coordination numbers of 10 and 9,
respectively The higher coordination number of CeIIIis
con-sistent with the larger radius of this cation compared to that of
GdIII The coordination spheres of the six-coordinate NiIIions
are completed by axial methanol molecules.
The slightly different radii of the Gd3+ and Ce3+ions
obvi-ously have also influence on the coordination modes of the
central lanthanide ions Since the size of the central cavity is
mainly determined by the coordination of the two peripheral
nickel ions, the coordination positions of the Gd3+ and Ce3+
ions are controlled by their size The relatively small
gadolin-ium ion is well accommodated in the central hexagonal plane formed by the bis(acetylpyridine) fragments The two organic ligands are slightly twisted to accommodate the GdIIIions in
an optimal way This is consistent with the O13–Gd1–O14,
O13–Gd1–O24, N1–Gd1–N2 trans angles being in the range
of 150–169°, which largely deviate from 180° The O13–Ni1–
O23 and O14–Ni2–O24 angles of 81.4(2)° and 84.2(2)°, respectively, are also significantly lower than expected for an ideal octahedral arrangement The C–O bond lengths in the bridging acetato ligands are almost equal reflecting the delo-calization of electron density In contrast, the two negative charges of L2– are not equally delocalized over three metal cores The highest charge density is localized in the chelate rings of the nickel atoms This is consistent with the fact that the corresponding Ni–O bond lengths are nearly equal to the Ni–O(acetate) bond lengths, while the Gd–O(acetate) bonds are significantly shorter than those to oxygen atoms of the
che-lating ligands Nevertheless, all M–O and M–N bonds in 1a
are in the same ranges of the corresponding bond lengths in
the previously reported trinuclear [NiLnNi] complexes.[5]
In the structure of 1b, the larger Ce3+ion seems to be too big for the cavity formed between the two nickel β-diketonato ligands and, thus, it is positioned above the planar N2O4 hexagonal base toward the two bidentate acetates.
Trang 4Reactions of two equivalents of H2L with a mixture of NiCl2
(2 equiv.) and LnCl3 (1 equiv.) in dichloromethane/methanol
(1:1, v:v) yield deep yellow-green solutions Although no pure
crystalline products could be isolated from such solutions,
there is mass spectrometric evidence for the formation
of trinuclear compounds such as [Ni2Ln(L)2Cl2]+,
[Ni2Ln(L)2(OH)Cl]+, [Ni2Ln(L)2Cl]2+ The addition of acetic
acid to such solutions results in the formation of complexes 1,
but with slightly lower yields compared to the synthesis
starting directly from the transition metal acetates
Neverthe-less, this route represents a synthetic approach to compounds
with other auxiliary carboxylato ligands than acetate.
Accordingly, trinuclear complexes with the composition
[Ni2Ln(L)2(PhCOO)3(solvent)2] (2) can be isolated from such
reactions with benzoic acid in high yields (see Scheme 3).
Scheme 3 Reactions of H2L with M IICl2, LnCl3, and benzoic acid
The IR spectra of 2 are almost identical to those described
for 1 Two absorptions corresponding to the ν(C=O) stretches
of L2– are sharp, strong bands at 1600 cm–1and 1570 cm–1.
The absorptions of ν(C=O) stretches of carboxylato ligands
appear at about 1550 cm–1 and are well separated from the
ν(C=O) stretches belonging to L2– The mass spectra of 2 do
not show the molecular ions but intense fragment ions with
m/z = 1254.04 for the gadolinium complex 2a and m/z =
1236.12 for the cerium compound 2b due to ions of the
com-position [Ni2Ln(L)2(PhCOO)2]+.
The complexes 2 are moderately soluble in CH2Cl2and CHCl3.
Single crystals of [Ni2Gd(L)2(PhCOO)3(MeOH)(H2O)] (2a)
and [Ni2Ce(L)2(CH3COO)3(MeOH)2] (2b) were obtained by
slow evaporation of the reaction mixtures Figure 3 and
Fig-ure 4 illustrate the molecular structFig-ures of these compounds.
Selected bond lengths and angles of the complexes are
summa-rized in Table 1.
The cores of compounds 2 reveal trinuclear {NiLnNi(L)2}3+
arrangements similar to those described for 1a and 1b The
three positive charges of the skeletons are compensated by
each three benzoate anions to form neutral complexes All
benzoates serve as bidentate ligands Two of them act as
brid-ges between NiII and LnIIIand one binds exclusively to the
LnIII ion Thus, in both complexes, the LnIII atoms possess
coordination number 10 with a nearly planar hexagonal base
formed by N1, N2, O13, O14, O23, and O24 atoms of two
2,6-diacetylpyridine sites and each two oxygen donors from
acetates above and below this base The two nickel atoms are
six-coordinate with a distorted octahedral environment, where
Figure 3 Molecular structure of 2a Hydrogen atoms are omitted for
clarity Thermal ellipsoids represent 50 percent probability Hydrogen
bonds were found, H bond / d(D–H) / d(H···A) / d(D···A) /Å: O7–
H7···O5 / 0.86(3) / 1.88(3) / 2.728(2); O8–H8···O6 / 0.87 / 2.00 /
2.828(2)
Figure 4 Molecular structure of 2b Hydrogen atoms are omitted for
clarity Thermal ellipsoids represent 50 percent probability Hydrogen
bonds were found, H bond / d(D–H) / d(H···A) / d(D···A) /Å: O7–
H7···O5 / 0.832(10) / 2.001(12) / 2.818(2); O8–H8···O6 / 0.80(3) /
1.97(3) / 2.760(2)
the donor atoms of the diketonato units of two L2– ligands occupy the equatorial positions The axial positions are com-pleted by only weakly bonded methanol or aqua ligands The
Gd–O and Gd–N bonds in 2a are slightly shorter than the cor-responding Ce–O, Ce–N bonds in 2b, what can be explained
by the smaller ionic radius of Gd3+ Similar to the situation in
1a, the smaller size of GdIIIalso results in a marked distortion
of the main {Ni2Ln(L)2}3+ framework, which is indicated by
small N–Ln–N, O–Ln–O, O–Ni–O trans angles.
In order to obtain analogous trinuclear complexes of CoII, the reactions of H2L with mixtures of Co(CH3COO)2 and
LnCl3or CoCl2, LnCl3, and benzoic acid were carried out
un-der the same conditions applied for the syntheses of 1 and 2.
All such reactions, however, resulted in a mixture of products,
from which dark-red hexagonal plates of compound 3 were isolated as the main product The IR spectrum of 3 shows two
absorptions corresponding to ν(C=O) stretches of L2– at
1609 cm–1 and 1572 cm–1 The second band is well resolved
Trang 5and much less intense compared to that of 1 and 2 This
sug-gests the absence of acetate in the ligand sphere of 3 The ESI+
MS spectrum of 3 shows a very intense peak at m/z = 1360.01
corresponding to the cation [Co4(L)3(OH)]+ Dark red
hexago-nal plates of 3, suitable for crystal structure ahexago-nalysis, were
ob-tained by a slow evaporation of its MeOH/CH2Cl2 solution.
The compound is a neutral, octanuclear bis(triple-helical)
che-late complex of the composition [Co8(μ3-O)2(L)6] (3) A
struc-tural sketch of the compound is given in Figure 5a Figure 5b
represents an ellipsoid representation of the asymmetric unit
of 3, from which the complete molecule is derived by a
three-fold axis.
Figure 5 (a) Structure of 3 (b) Ellipsoid representation of the
asym-metric cell Hydrogen atoms are omitted for clarity Thermal ellipsoids
represent 50 per cent probability
Like analogous octanuclear cobalt complexes,[11]complex 3
consists of eight Co2+ ions forming a twofold capped, twisted
trigonal prism with a μ3-O2–ion centered in each of the two
inner faces All six doubly negatively charged L2–ligands act
as pentadentate ligands and bind to three cobalt atoms: to two
by the two β-diketonate moieties and to the remaining ones by
the 2,6-diacetylpyridine site The two antipodal cobalt atoms
and two μ3-O2–ligands are placed on the threefold rotational
axis The other six central cobalt atoms are divided into three
pairs, which are symmetrically equivalent Finally, all eight Co
atoms are six-coordinate, from which the two antipodal atoms
show an octahedral tris(β-diketonato) ligand sphere and the
remaining six Co atoms reveal a slightly distorted
trigonal-prismatic arrangement, bonded to one bidentate β-diketonate,
one tridentate 2,6-diacetylpyridine site, and one μ3-O2–ligand.
Selected bond lengths and angles are summarized in Table 2.
Table 2 Selected bond lengths /Å in compound 3.
Co1–O11 2.062(4) Co3–O26 2.051(3) Co1–O13 2.076(4) Co3–O3 1.936(1) Co2–O21 2.069(3) Co4–O23 2.181(3) Co2–O23 2.078(3) Co4–N2 2.128(4) Co3–O13 2.200(3) Co4–O24 2.238(3) Co3–N1 2.094(4) Co4–O14 2.087(3) Co3–O14 2.488(5) Co4–O16 2.106(3) Co3–O24 2.062(3) Co4–O4 2.020(1)
Mixed cobalt(II)/lanthanide(III) complexes with the core structures [Co2Ln(L)2(CH3COO)3] (4) and [Co2Ln(L)2(PhCOO)3] (5), however, can be rationally
synthe-sized in high yields via a three-step reaction: (1) H2L is first
fixed on the LnIII ion by the reaction with LnCl3 solutions, (2) CoII and a supporting base like Et3N are added in order
to form the main skeleton [Co2Ln(L)2]3+, and (3) the [Co2Ln(L)2]3+ cores are stabilized by the coordination of
bridging acetate (in the case of 4) or by the addition of benzoic acid (in the case of 5).
IR and MS spectra of 4 and 5 are almost identical to those discussed for 1 and 2, which strongly suggest analogous struc-tures Compounds 4 and 5 are better soluble in chlorinated
solvents like CH2Cl2 or CHCl3 than the corresponding nickel complexes While no single crystals of reasonable quality
could be obtained for compounds 4, single crystals of
[Co2Ce(L)2(Benz)3](MeOH)(H2O)] (5b) were formed easily
by slow evaporation of the corresponding reaction mixture.
The molecular structure of 5b is shown in Figure 6 Selected
bond lengths and angles of the complexes are compared with the values in the analogous nickel compounds in Table 1 The
bonding situation in 5b is virtually the same to that of com-pounds 2 The CeIIIion has the coordination number 10 and two CoIIhave the coordination number 6 Similar to the
situa-tion of 2b, one CoIIin 5b has a coordinated methanol and the
other has a water ligand in its octahedral ligand sphere All
Figure 6 Molecular structure of 5b Hydrogen atoms are omitted for
clarity Thermal ellipsoids represent 50 percent probability Hydrogen
bonds were found, H bond / d(D–H) / d(H···A) / d(D···A) /Å: O7–
H7···O6 / 0.88(1) / 1.99(2) / 2.72(1); O8–H8B···O16#1/ 0.87 / 2.59 /
3.22(1); O8-H8A···O26#1/ 0.87 / 1.99 / 2.76(1) Symmetry equivalent
#1 : 1 –x,–y,1-z.
Trang 6Co–O bonds in 5b are slightly longer than the equivalent
Ni–O bonds in 2b.
Conclusions
The ready combination of thermodynamically stable
trinu-clear [MIILnMII(L)2]3+cores (MII= Ni, Co; Ln = Gd, Ce) with
carboxylic acids recommends the use of bifunctional
carb-oxylic linkers to build supramolecules from [MIILnMII(L)2]3+
building blocks Ongoing studies about such coordination
polymers with the use of dicarboxylic acids are presently
un-derway in our laboratories.
Experimental Section
Materials: All chemicals used in this study were reagent grade and
used without further purification Solvents were freshly distilled unless
otherwise stated
Physical Measurements: Infrared spectra were measured as KBr
pel-lets with a Shimadzu IRAffinity - 1S FTIR spectrometer between 400
and 4000 cm–1 Positive ESI mass spectra were measured with an
Ag-ilent 6210 ESI-TOF (AgAg-ilent Technology) mass spectrometer All MS
results are given in the form: m/z, assignment Elemental analysis of
carbon, hydrogen, and nitrogen were determined with a Heraeus vario
EL elemental analyzer
Synthesis of the Ligand: H2L was prepared by a standard
pro-cedure.[12] The product was obtained as a yellow crystalline solid
Yield 65 % C23H17NO4: calcd C 74.38; H 4.61; N 3.77 %; found: C
75.26; H 4.49; N 3.54 % IR (KBr):ν˜ = 3130 (w), 3074 (w), 1620
(vs), 1570 (vs), 1489 (m), 1261 (m), 1228 (m), 1070 (s), 997 (m), 923
(m), 773 (vs), 702 (s), 684 (s), 617 (s) cm–1 +ESI-MS: 372.12 (100 %
base peak, [M + H]+, 394.10 (20 % base peak, [M + Na]+)
Syntheses of the Ni II Complexes
[Ni 2Ln(L)2 (CH 3 COO) 3 ] (1 ⬘): A solution of Ni(CH3COO)2 ·4H2O
(49.8 mg, 0.2 mmol) and LnCl3 ·xH2O (0.1 mmol) in MeOH (5 mL)
was added to a solution of H2L (74.2 mg, 0.2 mmol) in CH2Cl2
(10 mL) The mixture was stirred for 5 min at room temperature and
then triethylamine (50.5 mg, 0.5 mmol) was added Upon the addition
of Et3N, the color of the solution turned from light green to deep
yellow-green The resulting solution was allowed to evaporate at room
temperature for several days to give single crystals of 1, which were
suitable for X-ray structure analysis The crystals of 1 collected by
suction filtration and dried in vacuo to obtain pure powders 1⬘, which
were used for the physical measurements This drying operation
obvi-ously also removed coordinated solvent molecules as is strongly
sug-gested by the analytical data
[Ni 2 Gd(L) 2 (CH 3 COO) 3 ] (1a ⬘): Yield 84.9 % (109.3 mg)
C52H39N2O14Co2Gd: calcd C 52.46; H 3.30; N, 2.35 %; found: C
52.32; H 3.21; N 2.22 % IR (KBr):ν˜ = 3065 (w), 1605 (vs), 1568
(vs), 1520 (vs), 1460 (s), 1435 (s), 1283 (m), 1244 (w), 1159 (w) 1074
(w), 939 (w), 763 (m), 723 (w), 650 (w), 534 (w) cm–1 +ESI-MS:
1130.09 (100 % base peak, [M-CH3COO]+)
[Ni 2 Ce(L) 2 (CH 3 COO) 3 ] (1b ⬘): Yield 82.0 % (96.0 mg)
C52H39N2O14Co2Ce: calcd C 53.23; H 3.35; N 2.39 %; found: C
53.12; H 3.23; N 2.25 % IR (KBr):ν˜ = 3064 (w), 1600 (vs), 1566
(vs), 1519 (vs), 1457 (s), 1435 (s), 1280 (m), 1242 (w), 1157 (w) 1026
(w), 939 (w), 766 (m), 721 (w), 651 (w), 534 (w) cm–1 +ESI-MS:
1172.02 (5 % base peak, [M + H]+), 1112.13 (100 % base peak, [M-CH3COO]+)
NiCl2·6 H2O (47.5 mg, 0.2 mmol) and LnCl3·xH2O (0.1 mmol) was added to a solution of H2L (74.2 mg, 0.2 mmol) in CH2Cl2(10 mL)
After stirring for 5 min at room temperature, solid benzoic acid (36.6 mg, 0.3 mmol) and then triethylamine (80.8 mg, 0.8 mmol) were added to obtain deep yellow-green solutions The isolation of products
(2 and 2⬘) was done essentially the same as described for [Ni2Ln(L)3](CH3COO)3]
[Ni 2 Gd(L) 2 (PhCOO) 3 ] (2a ⬘): Yield 73 % (100.3 mg)
C67H45O14N2Ni2Gd: calcd C 58.45; H 3.29; N 2.03 %; found: C 58.50;
H 3.21; N 2.15 % IR (KBr):ν˜ = 3061 (w), 1599 (vs), 1571 (s), 1551 (vs), 1520 (vs), 1460 (vs), 1434 (s), 1281 (m), 1242 (w), 1157 (w)
1066 (w), 937 (w), 766 (m), 721 (m), 652 (w), 538 (w) cm–1
+ESI-MS: 1254.04 (100 % base peak, [M-PhCOO]+)
C67H45O14N2Ni2Ce: calcd C 59.19; H 3.34; N 2.06 % ; found: C
58.90; H 3.22; N 2.11 % IR (KBr):ν˜ = 3063 (w), 1599 (vs), 1570 (s),
1551 (vs), 1517 (vs), 1458 (vs), 1435 (s), 1278 (m), 1240 (w), 1157 (w) 1070 (w), 956 (w), 765 (m), 721 (m), 650 (w), 536 (w) cm–1
+ESI-MS: 1236.12 (100 % base peak, [M-PhCOO]+)
[Co 8 (L) 6 (O) 2 ] (3): Compound 3 was isolated as main product from
reactions mixtures, which were described for the syntheses of 1 and 2,
but with Co(CH3COO)2·4H2O or CoCl6·6H2O instead of the corre-sponding nickel salts as starting materials Typical yield: 50 % (34.0 mg) C138H90N6O26Co4: calcd C 60.94; H 3.34; N 3.09 %;
found: C 60.12; H 3.25; N 2.97 % IR (KBr):ν˜ = 3059 (w), 1609 (vs),
1572 (s), 1516 (vs), 1454 (vs), 1417 (s), 1269 (m), 1240 (w), 1159 (w)
1068 (w), 938 (w), 760 (m), 721 (m), 636 (w), 527 (w) cm–1
+ESI-MS: 1360.01 (100 % base peak, [Co4L3(OH)] +)
[Co 2Ln(L)2 (CH 3 COO) 3 ] (4⬘): LnCl3 ·xH2O (0.1 mmol) was dissolved
in methanol (3 mL) and added to a solution of H2L (74.2 mg, 0.2 mmol) in CH2Cl2(10 mL) The mixture was stirred for 15 min at room temperature Subsequently, a methanol solution (3 mL) of Co(CH3COO)2·H2O (49.8 mg, 0.2 mmol) and triethylamine (50.5 mg, 0.5 mmol) were added to the obtained solution, Upon the addition of Et3N, the color of the solution turned to deep red The resulting solu-tion was stirred for addisolu-tional 30 min and then allowed to evaporate
at room temperature Red single crystals of 4, which were suitable for
X-ray structure analysis, were obtained after a few days They were collected by suction filtration and used for the X-ray analyses Drying
in vacuo gave red powders of solvent-free 4⬘.
[Co 2 Gd(L) 2 (CH 3 COO) 3 ] (4a ⬘): Yield 83.7 % (997 mg)
C52H39N2O14Co2Gd: calcd C 52.44; H, 3.30; N, 2.35 % Found: C,
52.31; H, 3.29; N, 2.27 % IR (KBr):ν˜ = 3063 (w), 1593 (vs), 1564 (vs), 1524 (vs), 1456 (s), 1420 (s), 1282 (m), 1246 (w), 1159 (w) 1026 (w), 937 (w), 769 (m), 721 (w), 671 (w), 534 (w) cm–1 +ESI-MS:
1132.21 (100 % base peak, [M-CH3COO]+)
[Co 2 Ce(L) 2 (CH 3 COO) 3 ] (4b ⬘): Yield 88.0 % (0.103 g)
C52H39N2O14Co2Ce: calcd C 53.21; H 3.35; N 2.39 %; found: C
53.29; H 3.30; N 2.29 % IR (KBr):ν˜ = 3064 (w), 1599 (vs), 1564 (vs), 1520 (vs), 1458 (vs), 1429 (s), 1279 (m), 1242 (w), 1156 (w)
1024 (w), 937 (w), 766 (m), 720 (w), 671 (w), 532 (w) cm–1
+ESI-MS: 1114.06 (100 % base peak, [M-CH3COO]+)
Trang 7Table 3 Crystal data and refinement results.
Formula C56.5H57GdN2Ni2O21 C71H57Cl4GdN2Ni2O16 C69H55CeN2Ni2O17 C138H90Co8N6O26 C69H53CeCl2Co2N2O16
Crystal system triclinic triclinic triclinic trigonal triclinic
No of indept (Rint) 10963(0.0365) 15955 (0.0357) 15135 (0.0543) 8967 (0.0618) 14736 (0.0428)
R1 / wR2 0.0635 / 0.1486 0.0291 / 0.0656 0.0333 / 0.0622 0.0732 / 0.2125 0.0411 / 0.0993
[Co 2Ln(L)2 (PhCOO) 3 (5): The synthesis of 5 was done essentially
similar to that described for 4 except that CoCl2 ·6H2O was used
in-stead of Co(CH3COO)2·4H2O After the addition of CoCl2·6 H2O to
the yellow mixture of LnCl3(0.1 mmol) and H2L (0.2 mmol), solid
benzoic acid (36.6 mg, 0.3 mmol) was added and the mixture was
stirred for 5 min The addition of triethylamine (80.8 mg, 0.8 mmol)
immediately gave red solutions The isolation of 5 and 5⬘ was the same
as that of 4 and 4⬘
[Co 2 Gd(L) 2 ](PhCOO) 3 ] (5a ⬘): Yield 76.3 % (0.105 g)
C67H45N2O14Co2Gd: calcd C 58.43; H 3.29; N 2.03 %; found: C
58.28; H 3.20; N 2.275 % IR (KBr):ν˜ = 3065 (w), 1595 (vs), 1564
(vs), 1525 (vs), 1455 (s), 1420 (s), 1281 (m), 1247 (w), 1162 (w) 1025
(w), 933 (w), 765 (m), 721 (w), 668 (w), 534 (w) cm–1 +ESI-MS:
1256.03 (100 % base peak, [M–PhCOO]+)
[Co 2 Ce(L) 2 ](PhCOO) 3 ] (5b ⬘): Yield 81.3 % (0.113 g)
C67H45N2O14Co2Ce: calcd C 59.17; H 3.33; N 2.06;%; found: C
59.03; H 3.25; N 2.11 % IR (KBr): ν˜ = 3063 (w), 1593 (vs), 1564
(vs), 1524 (vs), 1456 (s), 1420 (s), 1282 (m), 1246 (w), 1159 (w) 1026
(w), 937 (w), 769 (m), 721 (w), 671 (w), 534 (w) cm–1 +ESI-MS:
1238.02 (100 % base peak, [M–PhCOO]+)
X-ray Crystallography: The intensities for the X-ray determinations
were collected with a Bruker D8 Quest instrument with Mo-Kα
radia-tion (λ = 0.71073 Å) Standard procedures were applied for data
re-duction and absorption correction Structure solution and refinement
were performed with SHELXS97 and SHELXL97.[13]More details on
data collections and structure calculations are listed in Table 3
The single crystal used for the structure determination of compound
1a was found to be a non-merohedral twin with two components The
integration using Apex2, resulted in a total of 31027 reflections 3784
reflections (1385 unique) involved component 1 only (mean I/σ =
69.4), 3657 reflections (1315 unique) involved component 2 only
(mean I/σ = 32.2), and 23527 reflections (10509 unique) involved both
components (mean I/σ = 32.5) The data were corrected for absorption
using Twinabs[14]and the structure was solved by direct methods with
only the non-overlapping reflections of component 1 The structure
was refined using the HKLF 5 routine resulting in a BASF value of
0.225(1) In an asymmetric cell of 1a, non-coordinated solvents
includ-ing 2.5 molecules of H2O and 2.5 molecules of MeOH are disordered
and were refined isotropically Hydrogen atoms of water molecules cannot be located unambiguously and thus, they were excluded
To finish the structure calculations of 3, highly disordered solvent was
treated by the SQUEEZE option in PLATON[15] identified a remarkably large potential solvent volume of 2422 Å3for the unit cell volume The use of PLATON/SQUEEZE resulted in an improvement
of the R1values of about 4 %
Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1041205 (1a·2.5H2O·2.5MeOH), CCDC-1041207 (2a·2CH2Cl2), CCDC-1041206 (2b·MeOH), CCDC-1041208 (3), and
CCDC-1041209 (5b·CH2Cl2) (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk)
Acknowledgements
We thank Vietnam’s National Foundation for Science and Technology Development for financial support through Project 104.02–2011.31
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Received: January 11, 2015 Published Online: February 25, 2015