Influence of the steric properties of pyridine ligands on the structure of complexes containing the {LnCd2(bzo)7} fragment

Article abstract of DOI:10.1007/s11172-020-2934-0

The reaction of Cd(NO₃)₂ · 4H₂O and Eu(NO₃)₃ · 6H₂O or Tb(NO₃)₃ · 6H₂O with potassium 3,5-di-tert-butylbenzoate (Kbzo) and N-donor ligands (1,10-phenanthrol

Full text of DOI:10.1007/s11172-020-2934-0

Russian Chemical Bulletin, International Edition, Vol. 69, No. 8, pp. 1544—1560, August, 2020
1544
Influence of the steric properties of pyridine ligands
on the structure of complexes containing the {LnCd2(bzo)7} fragment*
M. A. Shmelev,а Yu. K. Voronina,a N. V. Gogoleva,a A. A. Sidorov,a M. A. Kiskin,a F. M. Dolgushin,b
Yu. V. Nelyubina,b G. G. Aleksandrov,a† E. A. Varaksina,b,c I. V. Taydakov,b,c,d and I. L. Eremenkoa
aN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 954 1279. E-mail: shmelevma@yandex.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085. E-mail: larina@ineos.ac.ru
cP. N. Lebedev Physical Institute, Russian Academy of Sciences,
53 Leninsky prosp., 119333 Moscow, Russian Federation.
Fax: +7 (499) 135 7880. E-mail: office@lebedev.ru
dMoscow Institute of Physics and Technology,
9 Institutskiy per., 141700 Dolgoprudny, Moscow region, Russian Federation.
Fax: +7 (495) 408 4254. E-mail: info@mipt.ru
The reaction of Cd(NO3)2•4H2O and Eu(NO3)3•6H2O or Tb(NO3)3•6H2O with potas-
sium 3,5-di-tert-butylbenzoate (Kbzo) and N-donor ligands (1,10-phenanthroline (phen),
2,4-lutidine (2,4-lut), 3,4-lutidine (3,4-lut), phenanthridine (phtd), 2,3-cyclododecenopyridine
(cdpy), acridine (acr)) afforded heterometallic LnCd2 complexes: [EuCd2(bzo)7(EtOH)2(phen)] (2),
[LnCd2(bzo)7(2,4-lut)4] (Ln = Eu (3), Tb (4)), [EuCd2(bzo)7(H2O)2(2,4-lut)2]•MeCN (5),
[EuCd2(NO3)(bzo)6(EtOH)2(2,4-lut)2] (6), [EuCd2(bzo)7(H2O)(EtOH)(3,4-lut)2]•5EtOH
(7), 3[EuCd2(bzo)7(H2O)2(phtd)2]•4phtd (8), [EuCd2(bzo)7(EtOH)3(cdpy)] (9), 2[EuCd2-
(bzo)2(EtOH)4]•acr (10). The structures of complexes 2, 3, and 5—10 were determined by
single-crystal X-ray diffraction. The isostructurality of complexes 3 and 4 was confirmed by
powder X-ray diffraction. The structure of the trinuclear {Ln2Cd} metal core is stable and inde-
pendent of the type of peripheral ligands coordinated to cadmium atoms. Photoluminescent
properties of compounds 3 and 4 were studied.
Key words: cadmium, lanthanides, 3,5-di-tert-butylbenzoic acid, luminescence, X-ray
diffraction.
Variations of geometric parameters of ligands involved
turally similar to scorpionate ligands. In the latter moieties,
a group consisting of three carboxylate anions coordinated
to a M atom acts as a chelating ligand for the hetero-
metal Х. The coordination environment of triply charged
lanthanide ions is completed by additional carboxylate
anions or carboxylate and nitrate anions to form the
{LnM2(O2CR)7}, {LnM2(NO3)(O2CR)6}, {Ln2M2(NO3)2-
(O2CR)8}, or {Ln2M2(O2CR)10} units. In these systems,
the coordination environment of M can be completed by
neutral monodentate or chelating ligands to form mo-
lecular complexes and also by neutral bridging ligands to
form coordination polymers.7,10,12,13 The coordination
environment of 3d metals is completed by a monodentate
or chelating, generally N-donor, ligand regardless of the
type of the heterometallic complex. The 3d metal atom
coordinated by a monodentate N-donor ligand has a tetra-
hedral or distorted trigonal-bipyramidal coordination
in the heterometallic chain structural units {M2Xn(O2CR)k}
(M = CoII, NiII, CuII, ZnII, CdII; X = Li (n = 2, k = 6),
Mg (n = 1, k = 6), Ca (n = 1, k = 6), Ln (n = 1, 2, k = 7,
10)), in which 3d metals or cadmium are combined with
lithium, magnesium, calcium, or lanthanide atoms,1—12
can be employed to get knowledge on conformational
flexibility of these metal cores. These data are useful for
the analysis of the structures of more complex polynuclear
compounds, particularly metal-organic frameworks based
on related heterometallic units and structurally similar
metal cores. This heterometallic unit is composed of two
peripheral metal-containing moieties {M(O2CR)3} struc-
* Dedicated to Academician of the Russian Academy of Sciences
A. M. Muzafarov on the occasion of his 70th birthday.
† Deceased.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1544—1560, August, 2020.
1066-5285/20/6908-1544 © 2020 Springer Science+Business Media LLC

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1545
environment; the 3d metal atom coordinated by chelating
ligands has an octahedral geometry.
molecules are completely or partially replaced depending
on the Cd : L ratio. The reaction with a tenfold excess of
2,4-lut (Cd : Eu : L = 3 : 1 : 30) gives the compounds
[LnCd2(bzo)7(2,4-lut)4] (Ln = Eu (3), Tb (4), see Scheme 1).
The tenfold excess of 2,4-lut was required to completely
prevent the coordination of water or ethanol molecules to
cadmium atoms because the use of a smaller amount of
the ligand (Cd : L = 1 : 5) resulted in the formation of
complexes, in which cadmium atoms are coordinated by
water or ethanol molecules (see Scheme 1): [EuCd2-
(bzo)7(H2O)2(2,4-lut)2]•MeCN (5) and [EuCd2(NO3)-
(bzo)6(EtOH)2(2,4-lut)2] (6). Under similar conditions,
the reaction with 3,4-lutidine (3,4-lut) at Cd : Eu : L =
= 3 : 1 : 15 afforded the molecular complex [EuCd2-
(bzo)7(H2O)(EtOH)(3,4-lut)2]•4EtOH (7). The reaction
with bulkier phenanthridine (phtd) (Cd : Eu : L = 3 : 1 : 9)
gave the complex 3[EuCd2(bzo)7(H2O)2(phtd)2]•4phtd
(8). The reactions with 2,3-cyclododecenopyridine (cdpy)
and acridine (acr) (Cd : Eu : L = 3 : 1 : 9) produced the
asymmetric complex [EuCd2(bzo)7(EtOH)3(cdpy)] (9)
and the complex 2[EuCd2(bzo)2(EtOH)4]•acr (10) con-
taining the outer-sphere N-donor molecule, respectively
(see Scheme 1).
Related complexes of cadmium exhibit specific features
due to the larger coordination number of this metal and
longer bonds of the coordination polyhedron. In this case,
complexes with somewhat different structures can be
synthesized. In such complexes, the coordination environ-
ment of cadmium is completed via the coordination of
additional ligands, e.g., by small solvent molecules.10
Besides, bridging carboxylate groups mediate the spin
exchange coupling between metal centers, which is im-
portant for the preparation of magnetic materials. The
presence of an aromatic moiety in the carboxylate anion
can give rise to ligand-centered luminescence or efficient
energy absorption or transfer to the lanthanide ion and,
as a consequence, lead to enhancement of its emis-
sion.14—16
The aim of this work is to examine the coordination
to a cadmium atom involved in the heterometallic unit
{EuCd2(bzo)7} (bzo is the 3,5-di-tert-butylbenzoate anion)
of monodentate pyridine derivatives with bulky α-sub-
stituents and 1,10-phenanthroline in coordinating sol-
vents, the molecules of which can compete for a coordina-
tion site in the environment of the metal ion. 3,5-Di-tert-
butylbenzoic acid is a readily available aromatic acid
containing bulky alkyl substituents bonded to an aromatic
moiety. Two tert-butyl substituents provide high solubility
of the resulting carboxylate complexes in non-aqueous
media, making it possible to isolate crystals suitable for
X-ray diffraction. Besides, these substituents ensure the
formation exclusively of the {LnM2(O2CR)7} or {LnM2-
(NO3)(O2CR)6} units, which were required for our study.
In almost all cases, we used 96% ethanol as the solvent.
Compact water and ethanol molecules allowed us to ef-
ficiently examine the coordinative unsaturation of cad-
mium atoms under varying conditions of the synthesis.
It is worth noting that in the known heterometallic
3d-metal Ln complexes with monocarboxylic acids, only
one α-substituted pyridine molecule is coordinated to each
3d metal atom, while water, ethanol, or other solvent
molecules are not involved in the coordination; a large
excess of N-donor ligands is not required.1,2,17,18
In the trinuclear metal core of compound 2, the central
Eu atom is linked to the terminal cadmium atoms via one
chelating bridging and two bridging bzo anions (Fig. 1).
The Cd(1) atom (CdO4N2) is coordinated by the chelating
N-donor ligand. The coordination environment of the
Cd(2) atom (CdO6) is completed by two EtOH molecules.
The coordination environment of the cadmium atoms can
be described as a distorted octahedron. The environment
of the Eu(1) atom (EuO8) is completed to a trigonal do-
decahedron by two O atoms of the chelating bzo– anion,
as opposed to compound 1, in which the environment of
the terbium atom (TbO8) is completed by a NO3– anion.
Selected bond lengths and bond angles of complex 2 are
given in Table 1.
Results and Discussion
The heterometallic complex of the composition
[TbCd2(NO3)(bzo)6(phen)2]•2MeCN (1) was synthesized
previously12 by the reaction of cadmium 3,5-di-tert-butyl-
benzoate with Tb(NO3)3•6H2O and 1,10-phenanthroline
(Kbzo : Tb : phen = 3 : 1 : 3). The centrosymmetric struc-
ture of complex 1 and the octahedral environment of
cadmium atoms indicate that the metal atom is efficiently
shielded by its coordination environment, thereby prevent-
ing the coordination of small solvent molecules. Here we
showed that the replacement of Ln(NO3)3•6H2O by
{Ln(bzo)3}, which was prepared in situ by the reaction
similar to that used to synthesize 1, gave an asymmetric
linear complex of the composition [EuCd2(bzo)7-
(EtOH)2(phen)] (2, Scheme 1). The reactions utilizing
2,4-lutidine (2,4-lut) as the ligand (L) afford heterometal-
lic trinuclear complexes, in which coordinated solvent
A comparison of the molecular structures of complexes
1 and 2 determined by X-ray diffraction shows that the
geometry of the {Cd—Ln—Cd} metal core remains un-
changed regardless of the ligand occupying two coordina-
tion sites in the environment of the Cd atom (Fig. 2). Only
slight changes are observed in the bond and torsion angles
and, as a consequence, in the Cd—Ln—Cd angle (173.87°
in complex 1 and 171.44° in complex 2). The geometry of
the coordination polyherdra and the conformations of all
bridging carboxylate groups remain unchanged. The larg-
est difference is observed, as expected, in the positions of
NO3 and bzo– anions, which is reflected in the change
–

Shmelev et al.
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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
Scheme 1
O
N
R
n = 2, 3; R = 3,5-ButC6H3; LnX =
O
(2—5, 7—10),
O
(6); Ln = Eu (2, 3, 5—10), Tb (4)
O
O
Ln
Ln
L
Cd : L
1 : 1
Product
Ln
Eu
Eu
Tb
Eu
Eu
Eu
Eu
Eu
Eu
L1
L2
L3
L4
phen
2,4-lut
2,4-lut
2,4-lut
2,4-lut
3,4-lut
phtd
2
3
4
5
6
7
8
9
10
EtOH
2,4-lut
2,4-lut
2,4-lut
2,4-lut
3,4-lut
phtd
phen
EtOH
2,4-lut
2,4-lut
H2O
EtOH
H2O
H2O
1 : 10
1 : 10
1 : 5
2,4-lut
2,4-lut
2,4-lut
2,4-lut
3,4-lut
phtd
2,4-lut
2,4-lut
H2O
EtOH
EtOH
H2O
1 : 5
1 : 5
1 : 3
cdpy
acr
1 : 3
EtOH
EtOH
cdpy
EtOH
EtOH
EtOH
EtOH
EtOH
1 : 3

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1547
O(4)
O(5)
Cd(1)
O(14)
O(13)
O(3)
Eu(1)
O(11)
N(2)
O(12)
Cd(2)
O(6)
O(1)
N(1)
O(9)
O(2S)
O(2)
O(7)
O(10)
O(1S)
O(8)
Fig. 1. Molecular structure of compound 2. Hydrogen atoms, solvent molecules, and a part of tert-butyl substituents are omitted
for clarity.
...
of the angle between the M—O—C(N) and O—C(N)—
C(O) planes. The corresponding M—O—C(N)—C(O)
torsion angles are 180° and 169.8° in complexes 1 and 2,
respectively. An analysis of intramolecular non-covalent
interactions in complex 2 shows that a decrease in the
torsion angle is apparently attributed to an intramolecular
CH π interaction between the methylene hydrogen atom
of coordinated ethanol and the π system of the bzo– anion.
The presence of bulky conjugated 1,10-phenanthroline
moieties in both complexes is apparently responsible for
...
a considerable contribution of π π interactions to the
crystal packing of the compounds. However, the crystals
Fig. 2. Superposition of the molecular structures of complexes 1 and 2 (atoms of complex 1 are represented by spheres). Hydrogen
atoms, solvent molecules, and a part of tert-butyl substituents are omitted for clarity.

Shmelev et al.
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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
Table 1. Selected geometric parameters of complexes 2, 3, 5, and 6
Parameter
Bond
2
3
5
6
d/Å
Cd—N (L)
2.332(3), 2.353(3)
2.250(3), 2.344(3)
2.206(3)—2.634(3)
2.314(3)—2.506(3)
—
2.376(7), 2.384(10)
2.315(4)
2.362(3)
2.21(2), 2.377(9)
2.392(4)
Cd—O (solv)
Cd—O (bzo)
Eu—O (bzo)
Eu—O (NO3)
—
2.205(6)—2.734(7)
2.327(8)—2.504(5)
—
2.225(3)—2.610(3)
2.311(4)—2.511(4)
—
2.234(4)—2.721(4)
2.401(4)—2.479(4)
2.620(5)
...
Cd Eu
3.743(2), 3.745(2)
4.024(9)
3.815(4)
3.927(6)
Angle
ω/deg
166.65
Cd—Eu—Cd
171.44
172.74
170.01
of 1 and 2 exhibit different degrees of overlap between the
π systems, which is reflected in different geometric para-
meters of interactions. Thus, the distances between the
centroids of the phenanthroline moieties are 4.192(3) Å
in 1 and 5.682(2) Å in 2; the centroid—plane distances are
3.316 and 3.547 Å, respectively. This significant difference
in the strength of interactions is apparently attributed to
the presence of EtOH molecules in 2, which form compet-
Complex 3 is the first example of compounds, in which
two 2,4-lutidine molecules containing a substituent in the
α position are coordinated to one metal center involved
in a polynuclear complex and having an octahedral coor-
dination geometry (CdO4N2). A search of the Cambridge
Structural Database showed that only mononuclear carb-
oxylate complexes with two coordinated α-substituted
pyridine molecules were synthesized and characterized.19,20
The coordination modes of the bzo– anions and the
structures of the trinuclear metal cores of complexes 3, 5,
and 6 are similar to those of compounds 1 and 2 (Figs 5
and 6). The coordination environment of the Cd atoms is
completed to an octahedron by the oxygen atom of the
solvent molecule (EtOH or H2O) and the nitrogen atom
of the 2,3-lut molecule (compounds 5 and 6) or by two
N atoms of lut molecules (compound 3). The coordination
of two solvent molecules instead of 2,4-lutidine results in
...
ing hydrogen bonds with both coordinated (O(8) O(1S),
2.753(4) Å) and ethanol solvent molecules that are disor-
dered in the crystal (for this reason, the structure refine-
ment of 2 was performed using the SQUEEZE procedure).
...
The crystal structure of 1 is stabilized by only weak CH
contacts involving acetonitrile solvent molecules.
N
The structure of complex 3 was determined by X-ray
diffraction (Fig. 3). The isostructurality of complexes 3
and 4 was confirmed by powder X-ray diffraction (Fig. 4).
O(4)
O(3)
Eu(1)
O(6)
Cd(1)
O(5)
O(1)
N(2)
O(2)
N(1)
O(7)
Fig. 3. Molecular structure of complex 3. Hydrogen atoms and tert-butyl substituents are omitted for clarity.

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1549
I (arb. units)
I (arb. units)
6000
5000
4000
3000
2000
1000
0
10000
5000
1
2
10
20
30
40
2θ/deg
Fig. 4. Comparison of the experimental powder X-ray diffraction pattern of complex 4 (1) and the simulated diffraction pattern of
complex 3 (2).
O(4)
O(3)
O(6)
N(1)
O(5)
Eu(1)
Cd(1)
O(2)
O(1W)
O(1)
O(7)
Fig. 5. Molecular structure of complex 5. Hydrogen atoms, tert-butyl substituents, and solvent molecules are omitted for clarity.
O(1)
O(2)
O(6)
N(1)
O(5)
Eu(1)
Cd(1)
O(4)
O(9S)
O(3)
O(7)
Fig. 6. Molecular structure of complex 6. Hydrogen atoms, tert-butyl substituents, and solvent molecules are omitted for clarity.

Shmelev et al.
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Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
region of lutidine substituents. It should be noted that the
positions of the coordinated water and ethanol molecules
in complexes 5 and 6 are the same and are stabilized by
...
identical intramolecular hydrogen bonds (O(7) O(1W),
...
2.859(4) Å in the structure of complex 5; O(7) O(9S),
3.024(6) Å in complex 6). The presence of additional
hydrogen bonds with O atoms of coordinated solvent
molecules in the structures of 5 and 6 has no significant
effect on the molecular packing in the crystals. Thus, in
all the three structures, the packing consists of chains
running along the 0а axis and is stabilized mainly via
...
CH O interactions. Only the structure of 5 contains
a hydrogen bond with the MeCN solvent molecule; how-
ever, this interaction does not give rise to supramolecular
...
chains (N(1S) O(1W), 2.915(7) Å).
As opposed to the above-considered complexes with
2,4-lutidine, complex 7 contains 3,4-lutidine as the
N-donor ligand. This ligand has approximately the same
volume and exhibits only slightly different electron density
distribution. Complex 7 crystallizes in space group Р21
and, unlike molecules 3, 5, and 6, occupies a general
position. This is attributed to the fact that the cadmium
atoms in complex 7 are coordinated by asymmetric ligands.
Thus, one cadmium atom is coordinated, apart from
3,4-lutidine, by a water molecule, and another cadmium
atom is coordinated by an ethanol molecule, which com-
pletes the coordination environment of cadmium to an
octahedron. An analysis of the molecular structure of
complex 7 (Fig. 8) shows that its structure is very similar
to that of complex 5 and, in general, differs slightly from
the structures of the complexes with 2,4-lutidine. The
crystal packing is also composed of chains running along
Fig. 7. Superposition of the molecular structures of complexes 3
and 6. Atoms of complex 3 are represented by spheres.
a change of the Cd—Eu—Cd angle from 166.65° in com-
plex 3 to 176.12° and 170.02° in compounds 5 and 6, re-
spectively. Selected bond lengths and bond angles of
complexes 3, 5, and 6 are given in Table 1.
Compounds 3, 5, and 6 have very similar molecular
and crystal structures (Fig. 7). Moreover, the unit cell
parameters of the crystals of 3 and 5 are also similar. These
complexes crystallize in space group C2/c, and the mol-
ecules occupy a special position on a twofold axis passing
through the Eu(1) atom and the carbon or nitrogen atom
of the bzo or NO3 anions, respectively. A comparison of
the geometric parameters of the molecules shows that the
main, although very small, difference is observed in the
O(13)
O(3)
O(14)
O(12)
O(4)
O(6)
Cd(1)
O(5)
O(11)
Cd(2)
N(1)
N(2)
Eu(1)
O(9)
O(10)
O(8)
O(1S)
O(7)
O(1W)
O(1)
O(2)
Fig. 8. Molecular structure of complex 7. Hydrogen atoms and solvent molecules are omitted for clarity.

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1551
Table 2. Selected geometric parameters of complexes 7—10
Parameter
Bond
7
8
9
10
d/Å
Cd—N (L)
Cd—O (solv)
2.259(6), 2.262(5)
2.334(4) (H2O),
2.29(2), 2.38(2)
2.322(4)—2.355(5)
2.339(3)
2.265(3)—2.424(3)
—
2.26(1)—2.349(7)
2.333(3) (EtOH)
2.220(4)—2.694(4)
2.309(4)—2.568(4)
3.735(4), 3.778(4)
Cd—O (bzo)
Eu—O (bzo)
2.242(3)—2.650(5)
2.305(4)—2.538(4)
3.707(5), 3.751(6),
3.808(5)
2.202(2)—2.659(2)
2.328(2)—2.524(2)
3.706(3), 3.852(3)
2.182(10)—2.613(6)
2.323(6)—2.551(6)
3.740(8), 3.763(8)
...
Cd Eu
Angle
ω/deg
Cd—Eu—Cd
176.11
172.91, 173.09
170.81
179.32
the 0а axis. A hydrogen bonding system is somewhat more
extensive due to the presence of four ethanol solvent
molecules per complex 7. However, as in the structure of 5,
these interactions do not give rise to supramolecular chains
which retains the structure of the trinuclear metal core
{CdEuCd} observed in the above complexes. The sol-
vent molecules coordinated to the Cd atoms are only
partially replaced. Thus, each metal center (Cd) is coor-
dinated by the N atom of only one phtd molecule
and a water O atom, thereby completing the coordina-
tion environment to a distorted octahedron (CdNO5).
The coordination polyhedron of Eu(1) can be de-
scribed as a trigonal dodecahedron (EuO8). Selected
bond lengths and bond angles of complex 8 are given in
Table 2.
...
...
(O(1W) O(1), 2.745(6) Å; O(1S) O(2), 2.771(6) Å;
... ...
O(1W) O(2S), 2.645(7) Å; O(3S) O(4S), 2.70(1) Å;
...
...
O(1W) O(4S), 2.901(6) Å; O(5S) O(12), 2.88(1) Å).
Selected bond lengths and bond angles of complex 7 are
given in Table 2.
The replacement of lutidine by bulky phenanthridine
(phtd) resulted in the crystallization of complex 8 (Fig. 9),
N(4S)
O(21)
O(15)
O(16)
O(20)
Cd(2)
O(11)
O(14)
Cd(3)
O(18)
O(10)
Eu(1)
N(2)
O(17)
O(2W)
N(3)
O(13)
O(12)
O(9)
O(8)
O(3W)
O(2)
O(1)
O(6)
O(4)
N(1)
O(5)
O(7)
Cd(1)
N(1)
O(1W)
O(3)
Cd(1)
O(7)
O(1W)
O(6)
Eu(1)
O(1)
O(4)
O(5)
O(2)
N(5S)
Fig. 9. Fragment of the crystal packing of complex 8. Hydrogen atoms and tert-butyl substituents are omitted for clarity.

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Due to steric hindrance created by the phtd molecule, the
coordination of the second phtd molecule to the same metal
center is energetically and sterically less favorable than the co-
ordination of a water molecule present in the reaction
mixture. Only one example of the coordination of two phtd
molecules to one Cd atom in a mononuclear complex of
the composition [Cd(phtd)I2], in which cadmium has the
coordination number 4, was described in the literature.21
The investigation of homometallic cadmium pivalates
demonstrated that 2,3-cyclododecenopyridine ensures the
formation of a paddle-wheel binuclear complex, whereas
binuclear complexes only with two bridging anions crystal-
lize in the presence of 2,4-lutidine and phenanthridine.22
In the series of the heterometallic complexes with the
pyridine derivatives under consideration, 2,3-cyclodode-
cenopyridine contains the largest conformationally flex-
ible aliphatic substituent. Despite the presence of an excess
of cdpy in the reaction solution, only one cadmium atom,
Cd(1), in complex 9 (Fig. 10, Table 2) is coordinated by
a cdpy molecule and, additionally, by an EtOH molecule,
as opposed to lutidine- and phenanthridine-containing
compounds 2—8. The coordination environment of the
Cd(2) atom is completed to an octahedron by two EtOH
molecules. It cannot be ruled out that a complex, in which
a pyridine ligand is coordinated to each Cd atom, is gen-
erated in solution, but this apparently would lead to
a significant increase in its solubility, resulting in the
precipitation of the least soluble compound among those
present in equilibrium in the reaction solution.
Complexes 8 and 9 are distinguished from compounds
2—7 by much bulkier N-donor ligands. An analysis of the
geometry of complexes 8 and 9 suggests that the region of
the molecules, where the bulky N-donor ligand and the
small solvent molecule are coordinated, does not undergo
changes compared to complexes 2—7. However, the region
of the molecule of complex 9, where only two ethanol
molecules are coordinated, is significantly different. In
particular, one EtOH molecule occupies a coordination
site, which belongs to the carboxylate group in the other
complexes, and the O atom of the bridging bzo group oc-
cupies the site of the solvent molecule (the Eu—O—C—O
and Cd—O—C—O torsion angles of the correspond-
ing 3,5-di-tert-butylbenzoate moiety are 128.69(2)° and
–4.23(3)° in complex 8; –108.02(3)° and 66.24(3)° in
complex 9, respectively).
Interestingly, the asymmetric unit of the crystal struc-
ture of compound 8 contains 1.5 molecules of the complex
and two phtd molecules. It should be noted that the ge-
ometry of two independent molecules 8 is the same within
experimental error.
Since the refinement of both experimental data sets
was performed using the SQUEEZE procedure to account
O(4)
O(3)
O(7)
O(8)
O(10)
O(2)
O(9)
Eu(1)
O(11)
O(1A)
O(1)
O(5)
Cd(1)
N(1)
O(6)
Cd(1)
O(3A)
O(14)
O(2A)
O(13)
O(12)
Fig. 10. Molecular structure of complex 9. Hydrogen atoms and tert-butyl substituents are omitted for clarity.

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1553
N(1)
O(5)
O(1)
O(13)
O(14)
O(6)
O(2)
O(11)
O(9)
Eu(1)
O(1S)
Cd(1)
O(2S)
O(10)
O(3S)
Cd(2)
O(12)
O(3)
O(4)
O(7)
O(4S)
O(8)
Fig. 11. Molecular structure of complex 10. Hydrogen atoms, solvent molecules, and tert-butyl substituents are omitted for clarity.
for disordered ethanol solvent molecules, it is difficult to
discuss a hydrogen bonding system in the crystal. In gen-
eral, the system of non-covalent bonds in complex 8 is
somewhat more complex due to the presence of the phen-
anthridine solvent molecule involved both in the hydrogen
are occupied by ethanol molecules. As can be seen in Fig. 12,
which presents the superposition of complexes 10 and 3,
the metal core remains almost unchanged. Hence, it can
...
...
...
...
Table 3. π π Interactions in the crystal packing of complexes 2
bonding (O(1W) O(7), 2.842(7) Å; O(1W) N(5S),
and 8
...
2.81(1) Å; O(2W) O(8), 2.792(6) Å; O(2W) N(4S),
...
2.807(7) Å; O(3W) O(13), 2.749(6) Å in the structure of
Interaction
Cg—Cg Cg—Perp
Å
α
/deg
...
...
complex 8; O(1A) O(13), 2.822(5) Å; O(3A) O(14),
2.825(3) Å in 9) and π π overlap (Table 3).
...
To evaluate the degree of influence of coordinated
bulky N-donor ligands on the geometry of the metal core
in the compounds under consideration, it was interesting
to compare these compounds with a related system lack-
ing N-donor ligands. For this purpose, we synthesized and
structurally characterized a complex with acridine (acr)
of the composition 2[EuCd2(bzo)2(EtOH)4]•acr (10,
Fig. 11, Table 2). Low solubility and steric hindrance did
not allow acridine to be involved in the complex, and the
N-donor in the crystal of 10 is present as a solvent mol-
ecule. The molecular structure of trinuclear complex 10
is similar to those of complexes 2—9 (Fig. 12). The coor-
dination sites in the environment of both cadmium atoms
Complex 2
phen—phen
2.934
1.660
0.00
Complex 8
phtd(N(1A))—phtd(N(1A))
phtd(N(1A))—phtd(N(1B))
phtd(N(1B))—phtd(N(1B))
phtd(N(2A))—phtd(N(4S))
phtd(N(2B))—phtd(N(4S))
Phtd(N(3))—phtd(N(4S))
3.443
3.480
3.538
3.541
3.536
3.595
3.389
3.426
3.472
3.491
3.489
3.497
5.696
1.537
4.818
4.698
2.698
3.001
Note. Cg is the centroid of aromatic rings, Perp is the perpen-
dicular to the ring plane, α is the angle between the planes of
aromatic moieties.

Shmelev et al.
1554
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
band corresponds to the 5D0→7F2 transition, which is very
sensitive to the coordination environment of the europium
ion. This is indicative of the absence of a center of inver-
sion. On the contrary, the probability of the 5D0→7F1
magnetic dipole transition in the first approximation is
constant and independent of the geometry of the complex.
The integrated intensity ratio of 5D0→7FJ, J = 0, 2, 4,
transitions to 5D0→7F1 are 0.05, 4.29, and 0.97, respectively
and are indicative of low symmetry of the Eu3+ coordina-
tion environment.
The luminescence spectrum of complex 4 (Fig. 14)
shows intense bands assigned to 5D4→7FJ, J = 6—3, tran-
sitions. The 5D4→7FJ, J = 2—0, transitions have expectedly
low intensity.
The optical excitation spectra of complexes 3 and 4
(Fig. 15) display narrow f—f transition lines of lanthanide
ions and broad bands associated with ligand absorption.
The broadband excitation appears as two closely spaced
bands I and II with maxima at wavelengths of 282 and
295 nm, respectively, which are apparently assigned to
S0→S1 transitions of the 2,4-lut (I) and bzo (II) ligands.23
It should be noted that terbium complexes 3 and 1 exhibit
similar excitation spectra (see Ref. 12), whereas the exci-
tation spectra of related europium complexes are signifi-
cantly different. This may be attributed to the contribution
of the 1,10-phenanthroline molecule to sensitization of
the Eu3+ ion in complex 1. Therefore, despite the remote-
ness of 1,10-phenanthroline from the emission center, this
ligand is actively involved in the excitation of the central
lanthanide ion. In the isostructural terbium complex, this
pathway of luminescence excitation of the central ion is
less efficient. Apparently, in both Tb3+ complexes, the bzo
Fig. 12. Superposition of the molecular structures of complexes
3 (atoms in the structure of complex 3 are represented by spheres)
and 10. Hydrogen atoms, solvent molecules, and tert-butyl sub-
stituents are omitted for clarity.
be concluded that the {LnCd2(O2CR)7} metal core weakly
depends on the type of peripheral ligands coordinated to
cadmium atoms.
The luminescence properties of solid samples of com-
plexes 3 and 4 were studied at room temperature. These
compounds were chosen because their syntheses are well
reproducible and phase-pure samples can easily be prepared.
Figure 13 displays the luminescence spectrum of com-
plex 3 showing characteristic 5D0→7FJ, J = 0—4, electronic
transitions of the Eu3+ ions. At the wavelength of 537 nm,
the spectrum has a weak 5D1→7F1 transition indicative of
the partial internal conversion 5D1→5D0. The most intense
I (arb. units) 550
10
600
650
700 λ/nm
10
5D0→7F2
5D0→7F1
8
6
4
2
8
6
4
2
5D0→7F4
5D0→7F3
5D0→7F0
18000
17000
16000
15000
Е/cm–1
Fig. 13. Luminescence spectrum of complex 3 at λex = 300 nm and T =300 K.

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1555
I (arb. units)
10
500
550
600
650 λ/nm
10
5D4→7F5
5D4→7F4
8
6
4
2
8
5D4→7F6
5D4→7F3
6
4
2
5D4→7F2-0
20000
18000
16000
Е/cm–1
Fig. 14. Luminescence spectrum of complex 4 at λex = 300 nm and T = 300 K.
ligand makes the major contribution to the energy trans-
fer to the emission center.
The intensity of direct f—f excitation lines of the ter-
bium ion is much weaker than the intensity of ligand ex-
citation, which is indicative of efficient sensitization of
excitation of the lanthanide ion in complex 4 through the
d block. The probability of energy transfer from the ligand
to the lanthanide ion greatly depends on the energy dif-
I (arb. units)
300
350
400
450 500 550 λ/nm
II
16
16
14
12
10
I
14
12
LMCT
10
8
8
a
6
6
4
4
2
2
b
30000
25000
20000 Е/cm–1
35000
Fig. 15. Optical excitation spectra of complexes 3 (a, λem = 615 nm) and 4 (b, λem = 545 nm) at T = 300 K.

Shmelev et al.
1556
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
•6H2O (99.99%, Lanhit), Tb(NO3)3•6H2O (99.99%, Lanhit),
KOH (chemical purity grade, Reakhim), 3,5-di-tert-butylbenzoic
acid (>98%, Sigma-Aldrich), 1,10-phenanthroline (99%, Alfa
Aesar), 2,4-lutidine (99%, Sigma-Aldrich), 3,4-lutidine (98%,
Sigma-Aldrich), phenanthridine (97%, Sigma-Aldrich), 2,3-cyclo-
dodecenopyridine (98%, Sigma-Aldrich), and acridine (98%,
Sigma-Aldrich). Potassium 3,5-di-tert-butylbenzoate (Kbzo) was
prepared in situ by the reaction of stoichiometric amounts of
KOH and Hbzo in EtOH or an EtOH—MeCN mixture. Attenu-
ated total internal reflection IR spectra were recorded on
a Spectrum 65 Fourier-transform infrared spectrometer (Perkin
Elmer) in the frequency range of 4000—400 cm–1. Elemental
analysis was performed on a EuroEA 3000 CHNS analyzer
(EuroVector).
ference ΔE between the triplet level of the ligand and the
emission state of the lanthanide ion. According to the
empirical rule for the efficient energy transfer from the
ligand to Eu3+ and Tb3+ ions, ΔE should be in the ranges
of 2000—2500 and 2000—4000 cm–1, respectively.24,25 As
follow from the intensities of the ligand and f—f transitions,
the antenna effect in complex 3 is much less pronounced
compared to complex 4 due to the large value of ΔE. In
these complexes, ΔE with respect to the triplet levels of
2,4-lut (ca. 28700 cm–1) and bzo (26800 cm–1 23
) are larger
than 6000 cm–1 for 4 and 9000 cm–1 for 3, i.e., this value
for the europium complex is significantly larger than the
optimal value. Hence, the quantum yield of luminescence
of complex 3 (10%) is much lower compared to complex
4 (24%). The band II in the excitation spectrum of com-
plex 3 is more intense than the band I, which may be at-
tributed to more efficient energy transfer from the ligand
with slightly lower energy S1 and T1 levels due to approach-
ing to the optimal energy values. Besides, the excitation
spectrum of complex 3 exhibits a weak broad band in the
spectral range of 310—350 nm, which is absent in the
excitation spectrum of 4. This band can be assigned to the
charge transfer from the ligand to the europium(III) ion
(ligand-to-metal charge transfer, LMCT). Since the
LMCT state lies lower than the singlet S1 state, the charge
transfer can compete with the intrasystem S1→T1 transfer
and lead to a decrease in the quantum yield of lumines-
cence of complex 3.26
In summary, we synthesized a series of complexes of
similar composition [LnCd2(bzo)7L3/4] or [LnCd2(NO3)-
(bzo)6L4], in which monodentate and chelating ligands of
different nature can act as L. The competition between
N-donor molecules and water or ethanol molecules for
two sites in the Cd coordination environment was shown
for the complex with 2,4-lutidine. Due to an increase in
the volume of the α-substituent in pyridine, the coordina-
tion of the second N-donor in the complexes with phtd
and cdpy is highly improbable. The coordination of the
acr molecule to the cadmium atom in {LnCd2(bzo)7} is
not observed. The variation of N-donor ligands has only
a slight effect on the geometric characteristics of the LnCd2
metal core. According to the photoluminescence spectra,
samples 3 and 4 exhibit weak metal-centered emission.
The efficiency of luminescence enhancement of Tb and
Eu by aromatic organic ligands is low due to the large
energy difference ΔE between the triplet level of the ligands
and the excited state (>6000 cm–1) and the charge trans-
fer from the ligand to the europium(III) ion.
(3,5-Di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-butyl-
benzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-κ2O,O´)-
(1,10-phenanthroline)diethanoleuropium(III)dicadmium(II), [Eu-
(bzo-κ2O,O´)Cd2(μ-bzo-κ3O,O,O´)2(μ-bzo-κ2O,O´)4(EtOH)2-
(phen)] (2). A solution of Kbzo (0.175 g, 0.649 mmol) in EtOH
(10 mL) was added to a solution of Cd(NO3)2•4H2O (0.100 g,
0.325 mmol) in EtOH (15 mL). The reaction mixture was stirred
with heating (t = 70 °C) for 15 min. The white precipitate of
KNO3 that formed was filtered off, and a suspension, which
was prepared by the reaction of Eu(NO3)3•6H2O (0.048 g,
0.108 mmol) with Kbzo (0.088 g, 0.325 mmol) in EtOH (5 mL)
and MeCN (5 mL), was added to the filtrate. The resulting
.
reaction mixture was stirred at 75 °C for 30 min, the precipitate
of KNO3 was filtered off, and phen (0.059 g, 0.325 mmol) was
added to the filtrate. The reaction mixture was stirred at 75 °C
for 5 min, cooled to room temperature, and kept to allow slow
evaporation for 7 days. Colorless crystals of complex 2 suitable
for X-ray diffraction that precipitated were separated from the
mother liquor by decantation, washed with cold acetonitrile
(5 °C), and dried in air. The yield of 2 was 0.109 g (43.4% with
respect to Eu(NO3)3•6H2O). Found (%): C, 63.7; H, 7.7; N, 1.5.
C121H167Cd2EuN2O16. Calculated (%): C, 63.7; H, 7.4; N, 1.2.
IR, ν/cm–1: 3277 w, 2962 m, 2903 s, 2865 w, 1603 m, 1531 s,
1464 s, 1434 m, 1396 s, 1362 m, 1289 m, 1251 m, 1247 m, 1209 m,
1151 w, 1127 w, 1115 w, 1016 m, 923 m, 874 m, 842 m, 790 s,
763 m, 725 s, 704 s, 655 m, 582 m, 550 w, 531 m, 507 m, 477 m,
440 m, 426 s, 418 s, 412 s.
(3,5-Di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-butyl-
benzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-κ2O,O´)-
tetrakis(2,4-lutidine)europium(III)dicadmium(II), [Eu(bzo-κ2O,O´)-
Cd2(μ-bzo-κ3O,O,O´)2(μ-bzo-κ2O,O´)4(2,4-lut)4] (3). Com-
pound 3 was synthesized as described for 2 using 2,4-lut
(0.375 mL, 3.251 mmol, Cd : L = 1 : 10) instead of phen. Colorless
crystals suitable for X-ray diffraction that formed within 3 days
were separated from the mother liquor by decantation and washed
with cold acetonitrile (t ≈ 5 °C). The yield of 3 was 0.168 g (62.3%
with respect to Eu(NO3)3•6H2O). Found (%): C, 65.2; H, 7.3;
N, 2.2. C133H183Cd2EuN4O14. Calculated (%): C, 65.5; H, 7.6;
N, 2.3. IR, ν/cm–1: 3675 w, 2964 m, 2901 m, 1609 m, 1566 s,
1477 m, 1436 m, 1394 s, 1361 s, 1290 s, 1248 m, 1203 w, 1164 w,
1066 s, 1048 s, 922 m, 892 m, 818 s, 790 s, 737 s, 703 s, 599 w,
533 m, 473 m, 440 m, 419 m, 414 m, 407 m.
Experimental
(3,5-Di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-butyl-
benzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-κ2O,O´)-
tetrakis(2,4-lutidine)terbium(III)dicadmium(II), [Tb(bzo-κ2O,O´)-
Cd2(μ-bzo-κ3O,O,O´)2(μ-bzo-κ2O,O´)4(2,4-lut)4] (4). Com-
pound 4 was synthesized as described for complex 3 using
All manipulations for the synthesis of new complexes were
performed in air using EtOH (96%), MeCN (≥99.5%), and THF
(99%). New compounds were synthesized using the following
reagents: Cd(NO3)2•4H2O (99+%, Acros Organics), Eu(NO3)3•

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1557
Tb(NO3)3•6H2O (0.049 g, 0.108 mmol) instead of Eu(NO3)3•
•6H2O. Colorless crystals suitable for X-ray diffraction that
formed within 5 days were separated from the mother liquor by
decantation and washed with cold acetonitrile (t ≈ 5 °C). The
yield of 4 was 0.149 g (56.9% with respect to Tb(NO3)3•6H2O).
Bis(μ-3,5-di-tert-butylbenzoato-κ3O,O,O´)tetrakis(μ-3,5-
di-tert-butylbenzoato-κ2O,O´)bis(2,4-lutidine)(nitrato-κ2O,O´)-
diethanoleuropium(III)dicadmium(II), [Eu(NO3-κ2O,O´)Cd2(μ-
bzo-κ3O,O,O´)2(μ-bzo-κ2O,O´)4(EtOH)2(2,4-lut)2] (6). A solu-
tion of Kbzo (0.175 g, 0.649 mmol) in EtOH (10 mL) was added
to a solution of Cd(NO3)2•4H2O (0.100 g, 0.325 mmol) in EtOH
(15 mL). The reaction mixture was stirred with heating (t = 70 °C)
for 15 min. The white precipitate of KNO3 that formed was fil-
tered off, Eu(NO3)3•6H2O (0.048 g, 0.108 mmol) was added to
the filtrate, and the mixture was stirred for 10 min at 80 °C. Then
2,4-lut (0.188 mL, 1.625 mmol, Cd : L =1 : 5) was added to the
reaction mixture, and the mixture was stirred for 10 min. The
resulting transparent solution was kept at room temperature for
7 days. Crystals suitable for X-ray diffraction that precipitated
were separated from the mother liquor by decantation, washed
with cold acetonitrile (t ≈ 5 °C), and dried in air. The yield of 6 was
0.089 g (38.6% with respect to Eu(NO3)3•6H2O). Found (%):
C, 60.1; H, 7.1; N, 1.8. C108H156Cd2EuN3O17. Calculated (%):
C, 60.5; H, 7.3; N, 1.9. IR, ν/cm–1: 3675 w, 2962 m, 2902 m,
1608 w, 1524 m, 1475 m, 1438 m, 1392 s, 1362 s, 1317 m, 1289 m,
1248 m, 1202 m, 1163 w, 1128 w, 1079 m, 1067 m, 1047 m,
923 m, 894 m, 823 m, 816 s, 791 s, 742 m, 703 s, 674 m, 593 w,
531 m, 474 m, 457 w, 445 m, 419 m, 406 m.
Found (%): C, 65.0; H, 7.3; N, 2.1. C133H183Cd2TbN4O14
.
Calculated (%): C, 65.3; H, 7.5; N, 2.3. IR, ν/cm–1: 3675 w,
2962 m, 2901 m, 1609 m, 1568 m, 1475 m, 1436 m, 1396 s, 1360 s,
1290 s, 1248 m, 1204 m, 1164 w, 1066 s, 1048 s, 922 m, 893 m,
816 s, 789 s, 736 s, 705 s, 599 w, 535 m, 473 m, 441 m, 418 m,
414 m, 406 m.
Diaqua(3,5-di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-
butylbenzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-
κ2O,O´)bis(2,4-lutidine)europium(III)dicadmium(II), solvate with
acetonitrile, [Eu(bzo-κ2O,O´)Cd2(μ-bzo-κ3O,O,O´)2(μ-bzo-
κ2O,O´)4(H2O)2(2,4-lut)2]•MeCN (5). Compound 5 was syn-
thesized as described for complex 2 using 2,4-lut (0.188 mL,
1.625 mmol, Cd : L = 1 : 5) instead of phen. Colorless crystals
suitable for X-ray diffraction that formed within 3 days were
separated from the mother liquor by decantation and washed
with cold acetonitrile (t ≈ 5 °C). The yield of 5 was 0.107 g (42.3%
with respect to Eu(NO3)3•6H2O). Found (%): C, 63.1; H, 7.1;
N, 2.4. C123H175Cd2EuN4O16. Calculated (%): C, 63.1; H, 7.5;
N, 2.4. IR, ν/cm–1: 3675 w, 2962 m, 2902 m, 1608 w, 1524 m,
1475 m, 1438 m, 1392 s, 1362 s, 1317 m, 1289 m, 1248 m, 1202 m,
1163 w, 1128 w, 1079 m, 1067 m, 1047 m, 923 m, 894 m, 823 m,
816 s, 791 s, 742 m, 703 s, 674 m, 593 w, 531 m, 474 m, 457 w,
445 m, 419 m, 406 m.
Aqua(3,5-di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-
butylbenzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-
κ2O,O´)di(3,4-lutidine)ethanoleuropium(III)dicadmium(II), solvate
with five ethanol molecules, [Eu(bzo-κ2O,O´)Cd2(μ-bzo-
κ3O,O,O´)2(μ-bzo-κ2O,O´)4(H2O)(EtOH)(3,4-lut)2]•5EtOH
Table 4. Crystallographic parameters and the structure refinement statistics for compounds 2, 3, and 5
Parameter
2
3
5
Molecular formula
М
Т/K
Crystal system
Space group
a/Å
C
121H167Cd2EuN2O16
2282.32
C133H183Cd2EuN4O14
2438.58
C123H175Cd2EuN4O16
2342.42
120(2)
150(2)
123(2)
Triclinic
Monoclinic
C2/с
26.9463(18)
22.9817(15)
20.7788(13)
90
97.718(2)
90
12751.2(14)
4
1.270
0.876
25.999
0.872/0.924
Monoclinic
C2/с
26.956(2)
22.4576(19)
20.5806(17)
90
98.809(2)
90
12312.0(18)
4
1.264
0.906
26.000
0.856/0.912
–
P1
17.370(19)
18.346(11)
21.352(14)
81.600(11)
88.36(3)
84.373(19)
6699(9)
2
b/Å
c/Å
α/deg
β/deg
γ/deg
V/Å3
Z
dcalc/g cm–3
μ/mm–1
θmax/deg
Tmin/Tmax
Number of reflections
measured
unique
1.132
0.830
26.000
0.658/0.811
59215
26221
20010
(0.0297)
4856
1.023
0.0338
0.0887
38271
12340
5388
(0.1471)
3218
0.968
60115
12116
9479
(0.0845)
3865
1.055
with I > 2σI
(Rint
)
Number of refined parameters
GOOF
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
0.0755
0.2096
0.0458
0.1178
Residual electron density
–0.628/1.104
–1.835/2.274
–1.026/1.989
(Δρmin/Δρmax)/e Ǻ–3

Shmelev et al.
1558
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
(7). Compound 7 was synthesized as described for complex 2
using 3,4-lut (0.187 mL, 1.625 mmol, Cd : L = 1 : 5) instead of
phen. Colorless crystals suitable for X-ray diffraction that formed
within 5 days were separated from the mother liquor by decanta-
tion and washed with cold acetonitrile (t ≈ 5 °C). The yield of 7
was 0.130 g (47.7% with respect to Eu(NO3)3•6H2O). Found (%):
C, 62.9; H, 8.0; N, 1.3. C131H203Cd2EuN2O21. Calculated (%):
C, 62.5; H, 8.1; N, 1.1. IR, ν/cm–1: 3665 w, 3021 w, 2947 w,
2958 m, 2902 m, 1596 s, 1524 m, 1490 m, 1438 m, 1392 s, 1362 s,
1317 m, 1296 m, 1241 m, 1202 m, 1170 w, 1128 w, 1079 m,
1067 m, 1049 m, 923 m, 894 m, 823 m, 816 s, 791 s, 742 m, 703 s,
674 m, 593 w, 522 m, 457 w, 445 m, 419 m, 406 m.
(3,5-Di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-butyl-
benzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-κ2O,O´)-
bis(2,3-cyclododecenopyridine)triethanoleuropium(III)dicadmi-
um(II), [Eu(bzo-κ2O,O´)Cd2(μ-bzo-κ3O,O,O´)2(μ-bzo-κ2O,O´)4-
(EtOH)3(cdpy)] (9). Compound 9 was synthesized as described
for 2 using cdpy (0.217 g, 0.974 mmol, Cd : L = 1 : 3) instead of
phen. Colorless crystals suitable for X-ray diffraction that formed
within 7 days were separated from the mother liquor by decanta-
tion and washed with cold acetonitrile (t ≈ 5 °C). The yield of 9 was
0.122 g (47.7% with respect to Eu(NO3)3•6H2O). Found (%):
C, 64.3; H, 8.0; N, 0.6. C130H198Cd2EuNO19. Calculated (%):
C, 64.0; H, 8.0; N, 0.6. IR, ν/cm–1: 2952 w, 1608 s, 1562 w,
1438 w, 1395 w, 1361 w, 1290 w, 1247 m, 1203 s, 1164 s, 1044 s,
922 s, 894 m, 823 m, 790 w,742 w,704 w, 596 s, 531m, 475 m,
416 w.
Tri[diaqua(3,5-di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-
tert-butylbenzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzo-
ato-κ2O,O´)bis(phenanthridine)europium(III)dicadmium(II)],
solvate with four phenanthridine molecules, [Eu(bzo-κ2O,O´)-
Cd2(μ-bzo-κ3O,O,O´)2(μ-bzo-κ2O,O´)4(H2O)2(phtd)2]3•4phtd
(8). Compound 8 was synthesized as described for complex 2
using phtd (0.174 g, 0.974 mmol, Cd : L = 1 : 3) instead of phen.
Colorless crystals suitable for X-ray diffraction that formed
within 5 days were separated from the mother liquor by decanta-
tion and washed with cold acetonitrile (t ≈ 5 °C). The yield of 8
was 0.113 g (39.5% with respect to Eu(NO3)3•6H2O). Found (%):
C, 67.4; H, 7.0; N, 1.8. C445H544Cd6Eu3N10O48. Calculated (%):
C, 67.5; H, 6.8; N, 1.8. IR, ν/cm–1: 3675 w, 2962 s, 2902 s, 1558
m, 1524 m, 1438 m, 1394 s, 1361 m, 1289 m, 1248 m, 1202 w,
1164 w, 1067 w, 1048 m, 923 w, 893 m, 824 m, 789 s, 746 s, 703 s,
655 s, 584 w, 531 w, 506 w, 472 m, 426 s, 419 s, 413 s.
Di[(3,5-di-tert-butylbenzoato-κ2O,O´)bis(μ-3,5-di-tert-butyl-
benzoato-κ3O,O,O´)tetrakis(μ-3,5-di-tert-butylbenzoato-κ2O,O´)-
tetraethanoleuropium(III)dicadmium(II)], solvate with acridine,
[Eu(bzo-κ2O,O´)Cd2(μ-bzo-κ3O,O,O´)4(μ-bzo-κ2O,O´)2-
(EtOH)4]•acr (10). Compound 10 was synthesized as described
for 2 using acr (0.174 g, 0.974 mmol, Cd : L = 1 : 3) instead of
phen. Colorless crystals suitable for X-ray diffraction that formed
within 10 days were separated from the mother liquor by decan-
tation and washed with cold acetonitrile (t ≈ –5 °C). The yield
of 10 was 0.169 g (63.9% with respect to Eu(NO3)3•6H2O).
Found (%): C, 63.1; H, 7.6; N, 0.4. C239H352Cd4Eu2N2O36
.
Calculated (%): C, 62.8; H, 7.7; N, 0.3. IR, ν/cm–1: 3280 w,
2961 m, 2867 m, 1621 m, 1555 s, 1516 m, 1477 w, 1460 m, 1437 m,
Table 5. Crystallographic parameters and the structure refinement statistics for compounds 6—8
Parameter
6
7
8
Molecular formula
М
Т/K
C108H156Cd2EuN3O17
2145.11
120(2)
C131H203Cd2EuN2O21
2518.70
120(2)
C445H544Cd6Eu3N10O48
7931.15
150(2)
Crystal system
Space group
a/Å
Monoclinic
C2/с
17.6197(12)
29.232(2)
21.462(2)
90
96.3800(10)
90
10985.8(15)
4
1.297
1.009
26.000
0.834/0.860
Monoclinic
P21
15.8851(9)
27.3294(15)
17.8939(10)
90
114.5681(11)
90
7065.0(7)
2
1.184
0.796
25.999
0.765/0.812
Monoclinic
C2/c
70.236(3)
18.5297(9)
34.9673(16)
90
94.1134(8)
90
45391(4)
4
1.161
0.745
27.544
0.797/0.943
b/Å
c/Å
α/deg
β/deg
γ/deg
V/Å3
Z
dcalc/g cm–3
μ/mm–1
θmax/deg
Tmin/Tmax
Number of reflections
measured
unique
87983
10785
8116
67971
27696
24724
100006
49676
27743
with I > 2σI
(Rint
)
(0.0848)
3598
(0.0398)
3697
(0.0633)
9945
Number of refined parameters
GOOF
1.045
1.010
1.017
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
0.0486
0.0346
0.0697
0.1316
0.0789
0.1963
Residual electron density
–2.413/0.978
–0.587/0.582
–0.952/1.540
(Δρmin/Δρmax)/e Ǻ–3

Complexes based on {LnCd2(bzo)7} fragment
Russ. Chem. Bull., Int. Ed., Vol. 69, No. 8, August, 2020
1559
Table 6. Crystallographic parameters and the structure refinement statistics for compounds 9 and 10
Parameter
9
10
Molecular formula
М
Т/K
Crystal system
Space group
a/Å
C130H198Cd2EuNO19
2455.64
C239H352 Cd4Eu2NO36
4568.71
100(2)
150(2)
Triclinic
Monoclinic
C2/c
40.65(9)
23.71(6)
31.35(11)
90
128.04(3)
90
23800(117)
4
1.275
0.936
26.000
0.742/0.885
–
P1
17.6662(8)
18.4364(8)
20.8438(9)
77.8890(10)
87.0900(10)
80.5180(10)
6546.1(5)
2
b/Å
c/Å
α/deg
β/deg
γ/deg
V/Å3
Z
dcalc/g cm–3
μ/mm–1
θmax/deg
Tmin/Tmax
Number of reflections
measured
unique
1.246
0.856
26.000
0.897/0.919
63747
25724
21597
75694
23335
14774
with I > 2σI
(Rint
)
(0.0302)
5023
(0.0874)
4256
Number of refined parameters
GOOF
1.013
1.022
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
0.0391
0.0536
0.1003
0.1342
Residual electron density
–1.612/2.156
–1.723/1.799
(Δρmin/Δρmax)/e Ǻ–3
1393 s, 1361 s, 1316 w, 1289 s, 1247 m, 1203 w, 1162 w, 1142 w,
1044 m, 922 w, 895 m, 854 w, 824 m, 789 s, 739 s, 703 s, 657 w,
600 m, 532 m, 471 m, 419 m, 414 w, 404 m.
data_request/cif. The geometry of the polyhedra of the metal
atoms was determined using the SHAPE 2.1 program.31,32
Single-crystal X-ray diffraction studies were performed on
Bruker Apex II (for 2, 3, 8, and 10) and Bruker Apex II DUO
(for 5—7 and 9) diffractometers equipped with a CCD detector
(Mo-Kα, λ = 0.71073 Å, graphite monochromator).27 For all
the compounds, semiempirical absorption corrections were ap-
plied with the SADABS program.28 The structures were solved
by direct methods and refined by the full-matrix least-squares
method with anisotropic displacement parameters for all non-
hydrogen atoms. The OH hydrogen atoms of water and ethanol
molecules in complexes 2, 5, 8, and 9 were located in difference
Fourier maps; all other hydrogen atoms were positioned geo-
metrically. All hydrogen atoms were refined isotropically using
a riding model. The solvent molecules in the structures of com-
plexes 2 and 7—10 disordered over several positions were sub-
tracted using the SQUEEZE/Platon procedure. The calculations
were performed using the SHELX program suite29 and the OLEX2
software package.30
Crystallographic parameters and the structure refinement
statistics for compounds 2, 3, and 5—10 are given in Tables 4—6.
The structural data for compounds 2, 3, and 5—10 were depos-
ited with the Cambridge Crystallographic Data Centre (CCDC
1993446 (2), 1993447 (3), 1993448 (5), 1993449 (6), 1993450
(7), 1993451 (8), 1993561 (9), 1993562 (10)) and are available
at deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/
Single-crystal X-ray diffraction analysis (compounds
2, 3, 8, and 10), powder X-ray diffraction studies, IR
spectroscopy measurements, and elemental analysis were
performed using equipment of the Shared Facility Center
for Physical Research Methods of the N. S. Kurna-
kov Institute of General and Inorganic Chemistry of
the Russian Academy of Sciences (IGIC RAS) within
the framework of the State assignment of the IGIC RAS
in the field of fundamental scientific research. Com-
plexes 5—7 and 9 were structurally characterized with
the financial support from the Ministry of Science and
Higher Education of the Russian Federation using equip-
ment of the Center for Molecular Composition Studies
of the A. N. Nesmeyanov Institute of Organoelement
Compounds of the Russian Academy of Sciences. We
thank D. A. Makarov for help in synthesizing com-
pounds 7 and 9.
Complexes 2—5 and 8—10 were synthesized and char-
acterized with the financial support from the Russian
Science Foundation (Project No. 16-13-10537); com-
plexes 6 and 7, within the framework of the State assign-

Shmelev et al.
1560
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Received April 7, 2020;
accepted May 25, 2020