Coordination and extraction of lanthanides(III) with tripodal ligands on the triphenylphosphine oxide platform: Effect of uncoordinating substituents

Article abstract of DOI:10.1016/j.poly.2017.12.025

A ligand system containing three carbamoyl moieties secured onto a triphenylphosphine oxide platform (2-R₂NC(O)CH₂OC₆H₄)₃PO, where R = Me (1), Bu (2), and cyclo-Hex (3) has been developed for lanthanide complexation and extraction from aqueous solutions. The influence of non-coordinating alkyl substituents at the nitrogen atoms in the carbamoyl side arms on coordination and extraction properties of tripodal ligands 1–3 was studied. Two new ligands 1 and 3 with alkyl substituents of different bulkiness were synthesized and characterized by spectroscopic methods. Single-crystal X-ray structures have been determined for ligands 1 and 2. The selected coordination chemistry of ligands 1–3 with Ln(NO₃)₃ (Ln = La, Nd, Lu) has been evaluated. The 1:1 complexes of all ligands 1–3 were synthesized and characterized via elemental analysis and IR spectroscopy; in addition, the crystal structure of the ligand 1 complex with neodymium nitrate was determined by X-ray diffraction. Solution structure of 1:1 complexes was examined by IR and multinuclear (¹H, ¹³C, and ³¹P) NMR spectroscopy. A formation of 1:2 complexes with lanthanum and lutetium nitrates (IR, NMR, ESI-MS) has been examined and structure of the major components of 1:2 complexes solutions has been suggested for ligands 1–3. Preliminary extraction studies of Ln(III) (Ln = La, Nd, Eu, Lu) from 3 M NH₄NO₃ into 1,2-dichloroethane show that ligands 2 and 3 recover lanthanides much better than their mono analog [2-(Bu₂NC(O)CH₂O)-5-Et-C₆H₃]P(O)Ph₂ and known extractant Ph₂P(O)CH₂C(O)NBu₂.

Full text of DOI:10.1016/j.poly.2017.12.025

Accepted Manuscript
Coordination and extraction of lanthanides(III) with tripodal ligands on the tri-
phenylphosphine oxide platform: Effect of uncoordinating substituents
Anna G. Matveeva, Igor Yu. Kudryavtsev, Margarita P. Pasechnik, Anna V.
Vologzhanina, Tatyana V. Baulina, Anna V. Vavina, Georgiy Ya. Sukat, Sergey
V. Matveev, Ivan A. Godovikov, Alexander N. Turanov, Vasilii K.
Karandashev, Valery K. Brel
PII:
S0277-5387(17)30808-2
https://doi.org/10.1016/j.poly.2017.12.025
POLY 12982
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
30 October 2017
22 December 2017
Please cite this article as: A.G. Matveeva, I. Yu. Kudryavtsev, M.P. Pasechnik, A.V. Vologzhanina, T.V. Baulina,
A.V. Vavina, G.Y. Sukat, S.V. Matveev, I.A. Godovikov, A.N. Turanov, V.K. Karandashev, V.K. Brel,
Coordination and extraction of lanthanides(III) with tripodal ligands on the triphenylphosphine oxide platform:
Effect of uncoordinating substituents, Polyhedron (2017), doi: https://doi.org/10.1016/j.poly.2017.12.025
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Coordination and extraction of lanthanides(III) with tripodal ligands on the
triphenylphosphine oxide platform: Effect of uncoordinating substituents
Anna G. Matveevaa*, Igor Yu. Kudryavtseva*, Margarita P. Pasechnika, Anna V. Vologzhaninaa,
Tatyana V. Baulinaa, Anna V. Vavinaa, Georgiy Ya. Sukata, Sergey V. Matveeva, Ivan A.
Godovikova, Alexander N. Turanovb, Vasilii K. Karandashevc,d, and Valery K. Brela
a
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow,
119991 Russia;
b Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia;
c Institute of Microelectronics Technology Problems and High Purity Materials, Russian Academy
of Sciences, Chernogolovka, 142432 Russia;
d National University of Science and Technology MISiS, Moscow, 119049Russia.
*Corresponding authors. E-mail: matveeva@ineos.ac.ru (A.G. Matveeva); zaq@ineos.ac.ru (I.Yu.
Kudryavtsev)
Abstract
A ligand system containing three carbamoyl moieties secured onto a triphenylphosphine oxide
platform (2-R2NC(O)CH2OC6H4)3PO, where R = Me (1), Bu (2), and cyclo-Hex (3)) has been
developed for lanthanide complexation and extraction from aqueous solutions. The influence of
non-coordinating alkyl substituents at the nitrogen atoms in the carbamoyl side arms on
coordination and extraction properties of tripodal ligands 1–3 was studied. Two new ligands 1 and
3 with alkyl substituents of different bulkiness were synthesized and characterized by
spectroscopic methods. Single-crystal X-ray structures have been determined for ligands 1 and 2.
The selected coordination chemistry of ligands 1–3 with Ln(NO3)3 (Ln = La, Nd, Lu) has been
evaluated. The 1:1 complexes of all ligands 1–3 were synthesized and characterized via elemental
analysis and IR spectroscopy; in addition, the crystal structure of the ligand 1 complex with
neodymium nitrate was determined by X-ray diffraction. Solution structure of 1:1 complexes was
examined by IR and multinuclear (1H, 13C, and 31P) NMR spectroscopy. A formation of 1:2
complexes with lanthanum and lutetium nitrates (IR, NMR, ESI-MS) has been examined and
structure of the major components of 1:2 complexes solutions has been suggested for ligands 1–3.
Preliminary extraction studies of Ln(III) (Ln = La, Nd, Eu, Lu) from 3 M NH4NO3 into 1,2-
dichloroethane show that ligands 2 and 3 recover lanthanides much better than their mono analog
[2-(Bu2NC(O)CH2O)-5-Et-C6H3]P(O)Ph2 and known extractant Ph2P(O)CH2C(O)NBu2.
Key words: tripodal ligand, lanthanide complexes, X-ray diffraction, solution structure, liquid
extraction
1. Introduction
Growing interest in lanthanide complexes is determined by both rich coordination chemistry of
these elements and their unique physical and chemical properties allowing application of these
compounds in different multidisciplinary areas such as bioinorganic chemistry and materials
science [1]. Since the structure and properties of lanthanide complexes are affected by not only the
unique properties of Ln(III) but also the structural features of organic ligand, the search for new
ligating systems remains a challenging problem [2]. Among the most interesting ligands for
Ln(III) cations, multidentate tripodal ligands attract special attention. The complexes and ligands
of this type find an application in medical imaging and therapy [3], for transmembrane

transport [4], as synthetic sensors and receptors [5], as extractants [6], for designing single-
molecule magnets [7], etc.
Recently, we reported the synthesis of tripodal ligand on Ph3P(O) platform with anchored
carbamoyl side arms (2-Bu2NC(O)CH2OC6H4)3PO [8]. In the context of further development of
this field, we have prepared new ligands of this type 1 and 3 (Scheme 1) and studied their
coordination behavior toward lanthanide cations, which is determined by the same scaffold and
may be affected by non-coordinating alkyl substituents at the nitrogen atoms in the side arms. As
substituents, we selected methyl, butyl, and cyclohexyl groups. The ligand 1 with the smallest
methyl group provides an example of a molecule with minimal hydrophobic and steric effects.
Compounds with butyl (2) and cyclohexyl (3) groups will exhibit close lipophilicity. At the same
time, cyclohexyl is bulkier than butyl and this fact can affect ligand coordination mode. We
selected La(III), Nd(III), and Lu(III), located in the beginning, the middle and the end of
lanthanide series. Furthermore, neodymium is often used as a typical cation in studies of
lanthanides, while lanthanum and lutetium cations are not paramagnetic, that makes it possible to
use NMR spectroscopy for studying their complexes.
In this paper, we disclose the preparation of new tripodal ligands (1 and 3) and 1:1
complexes of ligands 1–3 with lanthanide(III) nitrates, the characterization of all compounds in
the solid state (X-ray crystallography for 1 and 2 and complex [Nd(1)(NO3)3]) and in solution by
13
31
IR and multinuclear NMR (1H, C, P) spectroscopy. Furthermore, we examined the possibility
to form 1:2 complexes in solution. Complex stoichiometry was established by ESI-MS. Finally,
the lanthanide extraction ability of these ligands from aqueous solution was studied using the
mono analog 4 and known extractant 5 containing the same donor groups as reference compounds
(Scheme 1).
R2N
Bu2N
O
O
O
NR2
O
R2N
O
P
O
Bu2N
O
P
O
P
O
O
O
O
Et
R = Me (1), Bu (2), cyclo-C6H11 (3)
4
5
Scheme 1. Chemical structure of tripodal ligand 1–3 and reference compounds 4, 5.
2. Results and discussion
2.1. Synthesis and characterization of ligands 1, 3
The ligands 1–3 were obtained from available initial compounds in two stages by the following
scheme:
R2N
O
O
OH
ClCH2CONR2
K2CO3, DMF
O
LDA
PO
3
PO
PO
3
3
1-3

Scheme 2. Synthesis of tripodal ligands 1–3.
Initial tris(2-hydroxyphenyl)phosphine oxide (2-HOC6H4)3P(O) was obtained by the treatment of
triphenyl phosphate with lithium diisopropylamide (LDA) [9] and next reacted with the
appropriate N,N-dialkylchloroacetamides to give the corresponding ligands 1–3. Both stages
proceed in high preparative yield (82–90%) and allow preparation of the target compounds of high
purity. We described the synthesis and spectral characteristics of ligand 2 in detail previously [8].
The composition and structure of the new ligands 1 and 3 were confirmed by the data of
13
elemental analysis, IR and NMR (1H, C, 31P) spectroscopy. IR spectra of compounds 1 and 3
exhibit the bands of stretching vibrations of P=O at 1178 and 1183 cm–1, respectively, and C=O in
the region 1641–1670 cm–1. Vibrations ν(C–O–C) are observed within the range 1260–1210 cm–1.
According to quantum chemical calculations, this mixed modes are related mainly to vibrations of
three CAr–O bonds, containing some contribution of ν(P=O) [8].
1H NMR spectra of compound 1 display signals of alkyl substituents at the nitrogen atoms
in the expected region (2.73–2.84 ppm for ligand 1 and 1.15–3.24 ppm for ligand 3). The proton
signals of the CH2O groups are observed at 4.52 and 4.31 ppm for ligands 1 and 3, respectively.
The aromatic protons appear at ~ 7.0 ppm as doublet of doublets (H-3), at 7.03 ppm as triplet (H-
5), at ~ 7.44 as triplet (H-4) for both compounds, and at 7.64 and 7.73 ppm as doublet of doublets
13
(H-6) for ligands 1 and 3, respectively. C NMR spectra display signals of alkyl and aryl carbon
atoms of both compounds in the expected regions. Carbon resonances of C=O and CH2O
fragments are observed as singlets at ~ 167 and ~ 69 ppm, while that of C–P fragment appears as
doublet at ~ 122 ppm (1JC,P ~ 110 Hz). Phosphorus signal appears as singlet in the expected region
at 23.9 and 24.8 ppm for 1 and 3, respectively.
The structure of ligands 1 and 2 was finally established by X-ray diffraction.
(a)
(b)
Fig. 1. Molecular view of ligands 1 (a) and 2 (b) in representation of atoms with thermal ellipsoids
(given with 50% probability).
The molecules of ligand 1 and 2 in crystal have asymmetrical propeller conformations (Fig. 1). In
the molecule of ligand 1, one of the three ortho OCH2 substituents is oriented to the same
direction as the P=O group, while two other substituents are oriented to the opposite direction. On
the contrary, in the molecule of ligand 2, two ortho substituents are oriented to the same direction
as the P=O group, while the third ortho substituent is directed to the opposite side. Ligands 1 and

2 display typical bond lengths and angles (Fig. 1). Selected bond distances are given in Table 1.
The realization of coordination mode with concerted orientation of substituents to provide metal
binding for these ligands requires the rotation of donor arms as compared with these
conformations in the crystalline state. According to quantum chemical calculations [8], this
coordination mode is the most probable.
2.2. Synthesis and solid state characterization of the complexes
Compounds 1–3 are tripodal polytopic ligands, whose molecules include strong donor P=O and
C=O groups and weaker ether oxygen atoms of C–O–C groups, which also can participate in
coordination to lanthanide cations. Worth mentioning that Fawcett and Platt [10] on the basis of
X-ray data reported coordination of the ether oxygen atoms in lanthanide complexes of bis[(2-
diphenylphosphino)phenyl]ether dioxide along with coordination of two P=O groups.
1:1 Complexes of ligands 1–3 with lanthanides nitrates—[La(NO3)3(1)] (6), [Nd(NO3)3(1)]
(7), [Lu(NO3)3(1)] (8), [La(NO3)3(2)] (9), [Nd(NO3)3(2)] (lit. [8]) (10), [Lu(NO3)3(2)] (11),
[La(NO3)3(3)] (12), [Nd(NO3)3(3)] (13), [Lu(NO3)3(3)] (14)—were prepared by the reaction of
stoichiometric amounts of the ligand and the salts in a mixture of aprotic solvents. In the case of 8,
ligand 1 and lutetium nitrate were dissolved in MeCN. The composition and structures of the
complexes in the solid state were studied using elemental analysis, and IR spectroscopy. The
structure of the crystalline complex 7 was also elucidated by X-ray diffraction.
2.2.1. X-ray structure. According to the data of single-crystal X-ray diffraction,
compound 7 is a neutral mononuclear complex, where the neodymium atom coordinates three
nitrate anions in a bidentate-chelate mode (Fig. 2).
Fig. 2. Molecular view of complex 7 in representation of atoms with thermal ellipsoids (given
with 50% probability).
The ligand 1 coordinates to the neodymium atom through the oxygen atoms of P=O and two C=O
groups, while the third carbonyl group and all C–O–C oxygen atoms remain uncoordinated. The
resulting NdO9 coordination polyhedron adopts the tricapped trigonal prismatic geometry with
oxygen atoms of 1 in one prism base and those of three nitrate anions in the second prism base and
three "cap" atoms. The Nd–O bonds to the ligand 1 are significantly shorter than those between
metal atom and the anions (Table 1).
Table 1. Selected bond distances (Å) in 1·DMF, 2 and 7·0.5MeCN.
Bond
1· DMF
7· 0.5MeCN
2.359(3)
2.397(4) – 2.424(4)
2.531(4) – 2.644(4)
1.518(4)
2
Ln–O(P)
Ln–O(C)
Ln–O(N)
P=O
1.486(3)
1.485(1)
C=O (free)
1.223(5) – 1.232(4) 1.225(2) – 1.239(2) 1.220(8)

C=O (coordinated)
1.256(7) – 1.279(7)
The coordinated C=O and P=O bonds are elongated as compared with the free ones, and ligand
conformation also differs from that of crystalline ligand 1. In complex, two of three carbonyl
groups and oxygen atoms of C–O–C groups are oriented to the same direction as the P=O group in
contrast to crystalline 1 where only one carbonyl group is directed in the same mode as the P=O
group.
2.2.2. IR spectroscopy characterization. The data of IR spectra for complex 7 agree well
with the coordination modes from the X-ray data. The formation of the P=O → Nd coordination
bond results in the shift of the ν(P=O) band in the IR spectra of crystalline complexes 7 by ~50
cm−1 to the low frequency region with respect to the band of the free ligand (1178 cm−1). The
formation of two C=O → Nd coordination bonds in complex 7 causes a shift of the ν(C=O) bands
to the low frequency region. A strong band appears at 1629 cm−1 and a weak band appears at 1647
cm−1 that corresponds to vibrations of coordinated C=O groups. The weak band at 1660 cm−1
unambiguously refers to the noncoordinated C=O group. The oxygen atoms of C–O–C groups are
non-coordinated, however, the bands in the region 1270–1210 cm−1 that belong to ν(C–O–C)
vibrations change, thus responding to coordination of phosphoryl group (Table. 2). Let us note
that the spectral appearance of coordination of C–O–C groups could not be determined
unambiguously because, according to quantum chemical calculations [8], the bands in the region
1260–1210cm−1 are related to mixed modes and include contribution of both CAr–O and ν(P=O)
bond vibrations.
Table 2. Selected IR (ν, cm–1) spectroscopic data for ligands 1–3 and their 1:1complexes with
lanthanide nitrates 6–14 in crystallinea and solid state
Compound ν(P=O)
ν(C=O)
1671vs, 1666vs
1660sh, 1631vs
1660sh, 1647sh, 1629s ~1250sh, 1232m
1258m, 1239m
1669s, 1654vs, 1648sh 1244sh, 1236m, 1221sh, 1212m
1665sh, 1630sh, 1610vs 1255m, 1233m, 1218m
1658sh, 1632sh, 1608vs 1245sh,1235sh, 1218m
1660sh, 1638sh, 1613s 1238m, 1216m
ν(C–O–C)
1260m, 1238s
1245m, 1228sh
1a
1178m
1121m
1126m
6
7a
1185sh,1180m 1670s, 1660sh, 1630s
1181s,
8
2a
1121m
1128m
~1120shb
1183m
1122m
1123m
1123m
9
10 [8]
11
3
12
13
14
1660sh, 1641vs
1656m, 1630sh, 1606vs 1230m, 1210sh
1660sh, 1625sh, 1604s 1230m, 1210sh
1225m, 1210sh
1659s, 1630sh, 1608s
1230m, 1210sh
b Shoulder of band at 1142 cm–1.
The strong broad IR bands of bidentately coordinated NO3 groups are detected at 1480 and 1290
cm−1 and relatively weak band is revealed at 1032 cm−1. According to X-ray crystallographic data,
crystalline complex 7 contains 0.5 solvate acetonitrile, but the IR spectra of this sample exhibit no
absorption for the CN group.
The IR spectra of complexes 6, 9–14 are similar to those of crystalline complex 7 (Table
2), which indicates tridentate P(O),C(O),C(O)-coordination of the corresponding ligand and
bidentate coordination of three NO3 groups in these complexes (Scheme 3).

Scheme 3. 1:1 Complexes in the crystalline (7) and solid (6, 9–14) state as well as in CD3CN (6,
7) and in CDCl3 (9–14) solutions.
Ln(III) cations in these complexes have coordination number 9.
Complex 8 has another structure. In this complex, the P=O group of ligand 1 remains free
(the spectrum retains band at 1180 cm−1 with a shoulder at 1185 cm−1). Bands at 1630 cm−1 and
1670 cm−1 with a shoulder at ~ 1660 cm−1 refer to vibrations of coordinated and free C=O groups,
respectively (Table 2). Taking into account that complex 8 is virtually insoluble in common
organic solvents, one can suppose that ligand 1 exhibits chelate-bridge C(O),C(O)-coordination
and binds two lutetium cations, whereas the P=O group and one C=O group remain free and three
nitrate ions are coordinated in bidentate mode. Complex 8 has polymer structure. The coordination
number of lutetium is eight.
Let us note that complexes of monoligand 4 with lanthanide nitrates are unknown,
however, the structure of several complexes of model ligand 5 were studied by X-ray diffraction
and IR spectroscopy [11,12]. The bidentate coordination of ligand 5 with lanthanide cation in the
IR spectra of crystalline complexes results in the shift of ν(P=O) and νC=O bands by 30–50 and
30–40 cm–1, respectively. The wide strong bands at ~1480 and ~1300 cm–1 and weak band at
~1032 cm–1 correspond to nitrato groups coordinated in bidentate mode. Nd(III), Pr(III), and
Eu(III) cations in these complexes have coordination number 9 or 10.
2.3. Solution-state characterization of the complexes
The structure of the lanthanide nitrate complexes with ligands 1–3 in solutions was studied by IR
and multinuclear NMR spectroscopy. The complexes of ligands 2 and 3 were studied in CDCl3,
while complexes of ligand 1 were investigated in CD3CN because they are insoluble in
chloroform.
31
1
13
The selected suitable for analysis parameters of IR and P, H, and C NMR spectra for
the solution of 1:1 complexes 6, 7, 9–14 in comparison with the data for the free ligands 1–3 are
given in Tables 3–5. The tables also include the data for model solutions with metal : ligand ratios
1:2 for lanthanum and lutetium complexes. Model solutions for neodymium complexes were not
studied, because neodymium paramagnetism hampers the use of NMR spectroscopy.
The coordination of the P=O group can be reliably determined from the NMR spectra of
complexes. The signals of the phosphorus nuclei as well as carbon nuclei C-1 of neighboring
groups exhibit corresponding downfield shifts (Tables 3–5) close to those for the known
complexes of akin phosphoryl-containing ligands [13]. The signals of the paramagnetic
neodymium complex show considerable broadening.
The participation of the C=O group in coordination appears in the 13C and 1H NMR spectra
as a downfield shift of the carbon signals of the C=O group relative to the free ligand signals
[13a,14]. The proton and carbon resonances of neighboring CH2 groups also display the
corresponding shifts (Tables 3–5). The participation of C–O–C ethereal oxygen atoms in
coordination should result in the shift of resonances for neighboring C-2 and CH2 groups. The
shift of C-2 nucleus is more reliable indicator of ethereal oxygen coordination, because the signal
of –CH2– group will respond to coordination of both carbonyl and ethereal oxygen atoms.

Table 3. Selected IR (ν, cm–1) and 31P{1H}, 1H and 13C NMR (δ, ppm; (W )a, ppm) spectroscopic data for the ligand 1 and their complexes with lanthanide
½
nitrates in CD3CN (0.01 M) at 25 °C
Sample ν(P=O) ν(C=O)
δP (W )
δH (OCH2)
δC (C=O) δC (OCH2)
½
1178m 1669vs, 1654s
23.9 s (0.01) 4.48 s
166.98 s
168.48 s
67.47 s
65.82 s
65.97 s
62.0 s
1
6
1126m 1669m,1650sh, 1630vs 32.0 s (0.05) 4.73 s
(6+1b)c 1123m 1668m, 1653sh, 1635s 30.7 s (0.26); 4.6 br s
–
d
d
3.4-3.6 v br s
1128m 1669m, 1643sh, 1625s 121 (1)
–
7
a The band width at half-height (in ppm);
b Ligand 1 added to solution of complex (Ln:L = 1:2) (see Section 4.4.);
c The medium band at 1356 cm−1 – νE(NO3); signals of minor component in 1H and 31C NMR spectra; additional singlet at 44.9 ppm (~ 3%) in 31P NMR
spectrum (see Section 2.3.2.1.);
d Not observed.
Table 4. Selected IR (ν, cm–1) and 31P{1H}, 1H and 13C NMR (δ, ppm) spectroscopic data for the ligand 2 and their complexes with lanthanide nitrates in
CDCl3 (0.02 M) at 25 °C
Sample ν(P=O) ν(C=O)
δP (W )a
24.4 (0.01) 4.40 s
δH (OCH2)
δC (C=O)
167.34 s
167.7 v br s 65.97 s
167.6 v br s 66.5 br s
δC (OCH2) δC (C-1)
½
216
9
1175m 1662s, 1639vs
68.71 s
122.21 d
1128m 1662m, 1630sh, 1619s 31.4 (0.4) 4.7 v br s
~117.7 v br d
~118 v br d
(9+2b)c 1123m 1660s, 1620vs
30.0 (0.5)d 4.6 br s
1016
11
1130m 1661m, 1630sh, 1616s
v br s –e
–
e
1175f
1625s
34.2 (0.3) 4.7 br s
167.80 s
167.7 v br s 65.45 br s
65.60 s
117.44 d
(11+2b)c 1128m 1658s, 1642sh, 1617s 34.0 (0.9)g 4.6 br s
~117.6 v br d
a The band width at half-height (in ppm);
b Ligand 2 added to solution of complex (Ln:L = 1:2) (see Section 4.4.);
c The medium band at 1356 cm−1 – νE(NO3) (see Section 2.3.2.2.);
d Additional overlapping signal at 31.1 ppm;
e Not observed;
f Shoulder of the band at 1166 cm–1;
g Minor signal at 25.3 ppm.

Table 5. Selected IR (ν, cm–1) and 31P{1H}, 1H and 13C NMR (δ, ppm) spectroscopic data for the ligand 3 and their complexes with lanthanide nitrates in
CDCl3 (0.02 M) at 25 °C
δP (W )a
Sample ν(P=O)
ν(C=O)
δH (OCH2)
δC (C=O)
δC (OCH2)
δC (C-2)
½
1183m
1125m
1659s, 1636m
1659m, 1625sh,
1606vs
24.8 (0.01)
31.4 (0.5)
4.29 s
4.6 br s
166.81 s
167.3 br s
70.33 s
69.0 v br s
161.24 d
159.97 s
3
12
(12+3b)c 1125m
1658s, 1625sh,
1608vs
31.2 (1.1)d
93 (5.4)
4.25 br.s,
~4.8 v br s
~167.8 br s
70.0 v br s, 66.1 br s
66.5 v br s
160.0 br s;165.0 br s
f
f
f
1125m,
1150she
1659m, 1625sh,
1606vs
13
14
–
–
–
1125m
1656s, 1623s,
1608sh
35.7 (0.6); 35.1 (0.5)g 4.7 br s
~166.6 v.br s
68.1 br s
160.18 d
(14+3b)c 1125m,1183w 1656s, 1630sh,
37.0 (1.5), 35.0 (1.1), 4.32 br s,
166.79 s, 169.3 br s; 70.0 br s; 68.2 br s,
67.2 br s
161.11 s;160.15 br s,
165.0 br s
1608s
25.2 (0.6)h
4.0–4.7 vv br s
a The band width at half-height (in ppm);
b Ligand 3 added to solution of complex (Ln:L = 1:2) (see Section 4.4.);
c The medium band at 1356 cm−1 – νE(NO3) (see Section 2.3.2.3.);
d Minor signals at 36.5 and 45.4 ppm;
e Shoulder of the band at 1166 cm–1;
f Not observed;
g Integral intensity ratio ~2:1;
h Integral intensity ratio ~ 1.1:2.8:1.

2.3.1. 1:1 Complexes
The IR spectrum of complex 7 in solution virtually retained when compared with the spectrum of
the crystalline sample (Tables 2, 3). The band of the coordinated P=O group is detected at 1128
cm−1, the bands of coordinated C=O and free C=O groups are observed at 1625 and 1669 cm−1,
respectively. The bands at ~1450 and ~1310 cm−1 correspond to nitrato groups coordinated in
bidentate mode. One can suppose that the ligand 1 is coordinated in a P(O),C(O),C(O)-tridentate
mode and compound 7 in CD3CN solution is present as mononuclear neutral complex
[Nd{P(O),C(O),C(O)-1}(OO-NO3)3]0 (Scheme 3).
NMR spectra of complex 7 provide little information owing to paramagnetic properties of
31
Nd but generally agree well with the proposed structure. The P NMR spectrum displays only one
1
broadened signal at 121 ppm. The signals in H NMR spectrum are very broadened and could not
13
be interpreted. In C NMR spectrum, no signals of ipso–Ph and C=O were observed. On account
of the lack of fine structure, the assignment of signals of aromatic protons is impossible; the signals
of Me and CH2O groups display expected shifts (Table 3).
The IR spectra of complexes 6 and 7 are virtually identical (Table 3), which enables us to
suppose that the complexes have the same structure (Scheme 3). NMR spectral data agree well with
the suggested structure (Table 3). The 31P{1H} NMR spectrum of solution of complex 6 shows one
broadened (W = 0.5 ppm) singlet at 32.0 ppm shifted downfield toward the signal of the free
½
ligand. The participation of the C=O groups in coordination appears in the 13C NMR spectrum as a
downfield shift of the carbon signals of the C=O groups. Signal change for neighboring groups
(OCH2, C-2, etc.) in 1H and 13C NMR spectra (Table 3, Fig. B1, B2) confirms the conclusion on the
coordination of Р=О and two C=O groups. No signal of C-1 nucleus is observed in the spectrum
because it falls in the solvent signal at ~117 ppm on expected upfield shift by ~4.5 ppm. One can
suppose that compound 6 in CD3CN solution, like complex 7, is present as mononuclear neutral
complex [La{P(O),C(O),C(O)-1} (OO-NO3)3]0 (Scheme 3).
The analysis of spectral data for solutions of 1:1 complexes of the studied ligands 1–3 with
lanthanum and neodymium nitrates (Tables 3–5) indicate that they have similar structure. The
structure of 1:1 complexes in solution is the same as in solid state. Irrespective of the nature of
substituent at the nitrogen atom, ligand molecules 1–3 in the corresponding mononuclear neutral
complexes 6, 7, 9, 10, 12, and 13 exhibit P(O),C(O),C(O)-tridentate coordination (Scheme 3).
In contrast to the spectra of 1:1 complexes of light lanthanides, the structure of 1:1 lutetium
complexes changes on passing from solid state to solutions. The spectral data for lutetium complex
of ligand 2 are the most unusual.
11
sole
The 1H and 13C NMR spectral data agree well with assumption on the coordination of all three
groups (Table 4).
The changes in chemical shifts (ΔδH) for the CH2O and (ΔδC) for C=O and CH2O groups
(Table 4) confirm the assumption on the coordination of all three C=O group. Let us note that the
13C NMR spectra of complex 11 (Fig. B3) and previously studied [{Lu(NO3)3}2(2)] complex [8]
13
show no broadening for all С nuclei, as distinct from the spectra of other complexes of ligand 2
(Table 4).
31P{1H} NMR spectrum shows
only
shifted
relative to the signal of free ligand by 9.8 ppm, which evidences the formation of P=O→Lu
coordination bond.
Thus, according to NMR spectra, the ligand in complex 11 is coordinated in tetradentate
mode, but, as distinct from the data of IR spectroscopy, there are no direct evidences on the
presence of non-coordinated P=O group. This contradiction seems to be explained by the nature of
both methods.
] The spatial structure of the coordination site of ligand 2 (Fig. 3) has such a
configuration that, at symmetrical tridentate coordination of all three C=O groups, the lutetium

atom will be disposed virtually above the P=O group even in the lack of P(O)→Lu coordination
bond and the pseudocontact interaction of O and Lu nuclei will be sufficiently strong (Fig. 3)
Lu
Bu2N
O
O
NBu2
O
Bu2N
O
O
O
O
P
Fig. 3. Visualization for the spatial structure of C(O),C(O),C(O)-coordinated ligand 2 in 1:1
complex with Lu(III). Ligand conformation corresponds to the global minimum [8].
We believe that this type of coordination of ligand 2 (without involvement of the P=O group)
occurs in solutions of lutetium complexes with metal : ligand ratio 1:1 (this work) and 2:1 [8]. All
nitrate ions in complex 11 are coordinated in bidentate mode, lutetium cation has coordination
number 9.
Although IR spectrum of 1:1 complex 14 (Table 5) is the same as the spectrum of solid
complex (Table 2), the data of NMR spectra allow us to suppose the presence in solution of two (or
31
several) complex forms. This assumption is supported by the presence of two signals in P{1H}
NMR spectrum at 35.7 and 35.1 ppm with integral intensity ratio ~ 2:1. Usually, such a shape of
spectrum is explained by the presence of equilibrium between neutral and cationic (as a contact ion
pair) complexes of ligand with coordinated P=O group (vide infra, [13c]). The structures
[Lu{P(O),C(O),C(O)-2}(NO3)3]0 (Scheme 3) and [Lu{P(O),C(O),C(O)-2}(NO3)2]+·(NO3)– are the
1
most likely. The data of H and 13C NMR (Table 5) do not contradict this assumption. The
coordination number of lutetium in these complexes is 9 or 7.
Thus, the nature of substituents at the nitrogen atom has no effect on the structure of 1:1
complexes of light lanthanides in both solid state and solutions. In neutral mononuclear lanthanum
and neodymium complexes, the ligands display tridentate P(O),C(O),C(O)-coordination. For
lutetium, which has the smallest radius, the structure of complexes in solution considerably differs
from that in solid state and depends on the nature of substituent at the nitrogen atom. Ligand 2
shows C(O),C(O),C(O)-coordination mode instead of P(O),C(O),C(O)-mode, whereas ligand 3
produces ionic complex along with neutral one.
2.3.2. Formation of 1:2
Since lanthanides(III) have large coordination numbers (up to 12), we examined the possibility for
the formation of 1:2 complexes with lanthanum and lutetium nitrates. The spectral data for model
solutions of 1:2 composition are given in Tables 3–5.
The major feature of IR spectra of all 1:2 complexes as compared with 1: 1 complexes is the
emergence of a band of “free” nitrate ion at ~1355 cm–1 and intensity redistribution for the bands of
coordinated and uncoordinated C=O group. The band of coordinated P=O group, as previously, is
observed at ~ 1125 cm–1. The spectrum retains the bands of nitrato groups coordinated in bidentate
mode. 31P NMR spectra exhibit additional minor signals and broadening of the main signal of
1
coordinated P=O group. The signals in H NMR spectra undergo considerable broadening, which
13
prevents adequate interpretation of the spectra. The C NMR spectra also display additional minor
signals, but the main difference consists in change in the chemical shift for C-2 nucleus in the
spectra of 1:2 complexes of ligand 3 (vide infra).

2.3.2.1. Ligand 1 complexation with La(NO3)3 at La:L ratio of 1:2 in CD3CN. In
accordance with the spectral data in Table 3 and the arguments given above, one can suppose that
1:2 complex of ligand 1 is a contact or solvent-separated ion pair where one ligand molecule is
coordinated in a P(O),C(O),C(O) tridentate mode, while another molecule coordinates in
P(O),C(O)-bidentate mode; lanthanum coordination number is 9 (Scheme 4).
Scheme 4. Cation of 1:2 complexes of ligands 1, 2 with Ln(NO3)3 (Ln = La, Lu) in solution.
Taking into account the typical lanthanum coordination number of ten, one can also suppose that
31
coordination of acetonitrile molecule is possible. The P NMR spectrum shows additional narrow
1
13
singlet at 44.9 ppm of a minor component (~3%) that causes supplementary signals in H and C
NMR spectra. Let us note that NMR spectra of 1:2 complexes of ligand 1 display the least number
of additional signals and the smallest broadening as compared with the spectra of complexes from
ligands 2 and 3 (cf. Tables 3–5). No signal of C-1 nucleus expected due to shift at ~117 ppm was
observed because it is obscured by the solvent signal, while the shift of signal from C-2 is small
(0.32 ppm).
2.3.2.2. Ligand 2 complexation with Ln(NO3)3 (Ln = La, Lu) at Ln:L ratio of 1:2 in
CDCl3. The spectral data for solution with La:L = 1:2 for ligand 2 are close to those for ligand 1
(cf. Table 3 and 4) except for larger line broadening in NMR spectra and emergence of an
additional signal in 31P NMR spectrum at ~ 31.1 ppm. In accordance with these data, one can
suppose that bisligand complex of ligand 2 also has structure shown in Scheme 5. Since La(III)
cation typically has coordination number 10 and chloroform does not show coordinating properties,
one can suppose that the main component [La{P(O),C(O),C(O)-2}{P(O),C(O)-2}(NO3)2]+·(NO3)–
is in equilibrium with a second complex where both ligand molecules are coordinated in tridentate
mode [La{P(O),C(O),C(O)-2}2(NO3)2]+·(NO3)–. This assumption explains the presence of two
1
close broadened signals in 31P NMR spectrum. The data of H and 13C NMR spectra agree well
with suggested structures.
Spectral data for solution with Lu:L = 1:2 (Table 4) allow us to suppose that the lutetium
and lanthanum complexes of 1:2 composition have the same structure (Scheme 4). Difference is the
presence of trace signals of minor component at δP ~ 25.3 ppm in the spectrum of the lutetium
complex, which enables one to suppose either ligand coordination without participation of the P=O
1
13
group or the presence of free ligand. H and C NMR spectra provide no possibility to clarify the
structure of the minor component.
2.3.2.3. Ligand 3 complexation with Ln(NO3)3 (Ln = La, Lu) at Ln:L ratio of 1:2 in
CDCl3. The IR spectrum of solution at La:L = 1:2 is the same as for other 1:2 complexes (Tables
3–5). Certain variations in spectra in the region 1270–1210 cm−1 could not be interpreted
unambiguously. Difference is visible in NMR spectra (Table 5).
The signal in 31P{1H} NMR spectrum is shifted downfield by 6 ppm relative to the signal of
free ligand and considerably broadened (Table 5). Moreover, the spectrum exhibits trace signals at
36.5 and 45.4 ppm, which can be related to cationic complexes with larger charge than that of the
1
main complex species. The signals in H NMR spectrum are considerably broadened and poorly
13
interpretable. Analytical signals in the C NMR spectrum presented in Table 5 are broadened. The

shift of broadened signal by ΔδC(C=O) ~ 1 ppm indicates that a part of C=O groups are involved in
coordination. The major feature of 13C NMR spectrum is the emergence of a broadened signal of C-
2 at ~ 165 ppm along with a signal at 160.0 ppm (Fig. B4). We believe the first signal to indicate
bidentate coordination of ligand molecule via P=O group and the ethereal oxygen atom (Fig. 4),
while the second signal present in the spectra of all studied complexes and shifted relative to the
corresponding signal of free ligand by 1.0–1.2 ppm is related to the ligand in P(O),C(O),C(O)-
tridentate coordination mode.
(a)
(b)
Fig. 4. Visualization for the portion of the spatial structure of P(O),C(O)-coordinated ligand 2 (a)
and of P(O),Oeth-coordinated ligand 3 (b) in 1:2 complexes with Ln(III).
In accordance to the body of IR and NMR spectral data, the structure of the major component of
1:2 complex can be represented by Scheme 5. Lanthanum has coordination number 9.
Scheme 5. Cation of 1:2 complexes of ligand 3 with Ln(NO3)3 (Ln = La, Lu) in chloroform
solution.
Other cationic complexes, in particular cationic complex in Scheme 5, seem to exist in equilibrium
with this complex, which agrees well with change in the band intensity of C=O groups observed on
comparison of IR spectra of 1:2 lanthanum complexes of ligands 2 and 3 (see Tables 4 and 5).
Such considerable changes in ligand coordination mode are caused by the replacement of
butyl substituents at the nitrogen atom by the bulkier cyclohexyl fragments. In spite of much lower
donor ability of the ethereal oxygen atom as compared with carbamoyl one R2NC(O), the steric
hindrances on coordination of the second ligand molecule lead to change in coordination mode. Let
us note that P(O),P(O),Oeth-tridentate coordination mode with participation of ethereal oxygen atom
was detected by X-ray diffraction method in 1:2 complexes of bis[(2-
diphenylphosphino)phenyl]ether dioxide with lanthanide halides [10].
The IR spectrum of solution at Lu:L = 1:2 in the region of C=O vibrations is similar to the
spectrum of solution at La:L ratio of 1:2 for this ligand (see Table 5). However, in contrast to the

latter spectrum, the spectrum of 1:2 solution with lutetium nitrate shows a weak band of
uncoordinated P=O group at 1183 cm–1, while the intensity of the band of “free” nitrate ion at ~
1360 cm–1 is larger. The 31P{1H} NMR spectrum displays three broadened signals at 37.0, 35.0, and
1
25.2 ppm with integral intensity ratio ~ 1.1 : 2.8 : 1 (Fig. B5). The signals of OCH2 group in H
13
NMR spectrum are considerably broadened. In C NMR spectrum, the signals of diagnostic C=O,
OCH2, and C-2 groups are complicated and detected at several values (Table 5). Thus, the signals
of C-2 atom are detected at ~160.15 (br), 161.11, and ~165.1 (br) ppm, while broadened singlets of
OCH2 are observed at 70.0, 68.2, and 67.2 ppm. The signals of C=O are observed at 169.3
(broadened) and 166.79 ppm. The body of these data allows us to suppose the presence in solution
of several complexes where the ligand exhibits coordination in different modes: P(O),C(O),C(O)-
tridentate, P(O),Oeth-bidentate, as well as C(O),C(O)- and P(O),C(O)-bidentate coordinations.
Moreover, cationic complexes may include two or one nitrate ions in coordination sphere, which
makes spectral pattern more complicated.
Furthermore, using this solution as an example, we elucidate the reason of emergence of
31
additional signals in P{1H} NMR spectra shifted downfield relative of the signal of free ligand.
Previously (see above), we supposed that two phosphorus signals shifted downfield correspond to
two complexes with the same ligand coordination mode but different number of nitrate ions in
coordination sphere. These are exemplified by molecular complex [Ln(NO3)3(L)n]0 and cationic
species as solvent-separated and/or contact ion pairs [Ln(L)n(NO3)2]+ · (NO3)–. We described in
detail the separate detection of molecular and ionic complexes earlier [13c]. Indeed, the addition of
10 moles of Bu4NNO3 to a solution with Lu(NO3)3 : 3 = 1:2 leads to disappearance of signal at 37.0
ppm (Fig. B6), i.e., the equilibrium is shifted toward molecular complex.
We used also ESI-MS to determine complex composition. Positive-ion electrospray mass
spectral data for solutions of 1:1 complexes of ligands 2 and 3 in MeCN were recorded under the
same experimental conditions. Peak assignment was made on the basis of analysis of isotope
distribution and fragmentation of ions. The data of ESI-MS spectra for solutions of Ln(III)
complexes are given in Table B1. Almost all spectra show a dominant peak corresponding to
[LnL2(NO3)]2+ ion (see as an example Fig. B7) and a number of additional peaks, such as [LnL2]3+,
and [LnL(NO3)2]+. However, there are no peaks that may be related to tris-ligand complex.
Let us note that, according to preliminary data, the majority of Ln(III) cations are extracted
with ligands 2 and 3 as bis-ligand complexes (the study of extraction properties is in progress).
Thus, the structure of complexes of related ligands in solutions is determined by not only the
main coordination modes caused by the same structure of ligand frame but also is considerably
affected by the spatial properties of non-coordinated alkyl substituents at the nitrogen atom. In
solutions of 1:1 complexes with light lanthanide nitrates possessing large coordination sphere, all
three ligands 1–3 display P(O),C(O),C(O)-tridentate coordination mode. However, on coordination
of ligand 2 with butyl substituents at the nitrogen atom to lutetium nitrate, the ligand unexpectedly
displays the C(O),C(O),C(O)-tridentate coordination mode, in contrast to its homolog, ligand 3.
Even more differences in coordination mode occur upon formation of 1:2 complexes. The ligands 1
and 2 commonly show two coordination modes: P(O),C(O),C(O) and P(O),C(O), irrespectively of
lanthanide nature, whereas ligand 3 along with these modes also displays the P(O),Oeth-bidentate
coordination in 1:2 complexes with both light and heavy lanthanides.
2.4. Solvent extraction of lanthanides(III)
The extraction ability of ligands 2 and 3 was studied by the example of the extraction of certain
lanthanides(III) (La, Nd, Eu, Lu) from neutral aqueous solutions (3 M NH4NO3) into 1,2-
dichloroethane (DCE). Ligand 1 with methyl substituents at the nitrogen atom was prepared as a
model compound to study coordination properties and was not studied in extraction experiments
because it is markedly soluble in water. Distribution ratio (DL = [Lorg]/[Laq]) between organic and

aqueous phases for ligand 1 is 0.53, whereas DL values for ligands 2 and 3 are equal to ~ 10000 and
8000, respectively.
To compare the efficiency and selectivity of the studied ligands 2 and 3 as well as their
mono analog 4 [16] and well-known extractant 5, we compared the distribution ratios of the
lanthanides (D = [Ln]org/[Ln]aq) for extractants 2–5 under the same experimental conditions (Fig. 5).
D
120
100
80
60
40
20
0
3
La
2
Nd
4
Eu
5
Lu
Fig. 5. Comparative data on Ln(III) extraction with ligand 2–5 from 3 M NH4NO3 in DCE (0.05 M
ligand in DCE and 4·10–6 М metal in aqueous phase)
Fig. 5 shows that both compounds 2 and 3 extract Ln(III) much more efficiently than their mono
analog 4. This fact indicates the cooperative interaction of coordinating centers of the polytopic
system of ligands 2, 3 with lanthanide cations, which agrees well with structure of complexes (see
Section 2.3). Furthermore, compounds 2 and 3 recover Ln(III) much better than the known
extractant 5 containing the same donor centers P=O and C=O involved into coordination with
metal.
Extraction efficiency and selectivity is known to be dependent in complicated manner on
numerous factors, including the strength and structure of extracted complexes,
hydrophilicity/lipophilicity balance of a ligand and its complexes. Although ligands 2 and 3 exhibit
almost equal lipophilicity (see above), they differ considerably in Ln(III) extraction efficiency (Fig.
5). We suppose that the different structure of their 1:2 lanthanide complexes in solution is one of
the reasons of this difference. Such a structural difference should affect the strength and
lipophilicity of extracted complexes. Moreover, it was found preliminary that, in contrast to ligand
2, the stoichiometry of extracted complexes of ligand 3 is also dependent on lanthanide atomic
number (in progress).
The selectivity of both ligands differs insignificantly but it is slightly higher for ligand 2
(see Fig. 5). Thus, separation factor (SF = DLa/DLu) for ligand 2 is 9, while that for ligand 3 is only
2.3.
Thus, the nature of the tested substituents at the nitrogen atom has little effect on ligand
lipophilicity but considerably affects ligand coordination mode and its ability to recover metals into
organic phase.
3. Conclusion
Coordination and extraction properties of new type of tripodal ligands on the triphenylphosphine
oxide platform were studied. Two new tripodal ligands with alkyl substituents of different bulkiness

were synthesized. The influence of non-coordinating alkyl substituents (Me, n-Bu, cyclo-Hex) at
the nitrogen atoms in the side arms on coordination and extraction properties of tripodal ligands 1–
3 was studied. Eight new mononuclear 1:1 complexes of 1–3 ligands with Ln(NO3)3 (Ln = La, Nd,
Lu) were studied in the solid state (elemental analysis, IR, X-ray) and in solution (IR, 1H NMR, 13C
NMR, 31P NMR).
Irrespective of the type of substituent at the nitrogen atom, ligands 1–3 exhibit
P(O),C(O),C(O)-denticity in all studied solid 1:1 сomplexes (except for [Lu(1)(NO3)3]). In solution,
this coordination mode is retained for all 1:1 complexes except for [Lu(2)(NO3)3] (11). In complex
11, the ligand displays symmetrical C(O),C(O),C(O)-dentate coordination mode to form so-called
“hammock” for lutetium cation without coordination with the P=O group.
The possibility for the formation of 1:2 complexes with lanthanum and lutetium nitrates (IR,
NMR, ESI-MS) has been examined and solution structure of the major components of 1:2
complexes has been suggested. In solutions of 1:2 complexes, steric switching of coordination
mode from P(O),C(O),C(O)- and P(O),C(O)-dentate for ligands 1 and 2 to P(O),C(O),C(O)- and
P(O),Oet-dentate for ligand 3 is observed.
New polytopic tripodal ligands 2 and 3 extract Ln(III) much more efficiently than their
mono analog 4 and the known ditopic CMPO ligand 5. The efficiency and selectivity of lanthanide
extraction with ligand 3 is much higher than that with ligand 2, which seems to be due to change in
coordination mode in 1:2 complexes because the lipophilicity of ligands 2 and 3 is almost the same.
Further application of tripodal ligands on the triphenylphosphine oxide platform in
coordination and extraction chemistry is expected.
4. Experimental
4.1. General
Solvents were purified and dried using standard procedures [17]. Deuterated solvents, CD3CN
(99.8% D, Sigma–Aldrich) and CDCl3 (99.8% D, Sigma–Aldrich), were used as received.
1
Multinuclear H, 13C, and 31P{1H} NMR spectra were recorded on a Bruker Avance 400
spectrometer (operating at 400.23, 100.61, and 161.98 MHz, respectively) and a Bruker Avance
500 instrument (operating at 500.15, 202.46 and 125.75 MHz, respectively) at ambient temperature
using CD3CN (c = 0.01 M) or CDCl3 (c = 0.02 M) solution. Chemical shifts (ppm) refer to the
1
13
31
residual protic solvent peaks (for H and C), and 85% H3PO4 (for P) as external standards and
coupling constants are expressed in hertz (Hz), the band width at half-height (W1/2) is given in ppm
(for 31P{1H} NMR spectra). IR spectra in the region 400–4000 cm−1 were obtained on a Bruker
Tensor 37 FTIR spectrometer. The samples were KBr pellets and mulls in Nujol as well as 0.01 and
0.02 M solutions in CD3CN, and CDCl3, respectively, in CaF2 cuvettes. The content of C, H, and N
was determined on a Carlo Erba 1106 instrument. The content of P was determined according to the
published procedures [18]. Melting points were determined in open capillary tubes on a Stanford
Research Systems MPA120 EZ-melt automated melting point apparatus and were not corrected.
The
reagents—tris(2-hydroxyphenyl)phosphine
oxide
[9],
tris(2-N,N-
dibutylcarbamoylmethoxyphenyl)phosphine oxide (2) [8] model compound (N,N-
dibutylcarbamoylmethyl)diphenylphosphine oxide (5) [19], N,N-dimethylchloroacetamide [20] and
N,N-dicyclohexylchloroacetamide [21]—were prepared by the literature procedures.
Salts La(NO3)3·6H2O (reagent grade), Nd(NO3)3·6H2O (reagent grade), Eu(NO3)3·6H2O
(pure grade), and Lu(NO3)3·xH2O (Aldrich) were used without further purification. The water
content (x = 3) in commercial lutetium nitrate was determined experimentally.
The following reagents were used for the preparation of solutions in the extraction study:
bidistilled water, 1,2-dichloroethane (reagent grade), HNO3 (high purity grade). Solutions for
spectral and extraction studies were prepared by volumetric/gravimetric method.
4.2. Ligand synthesis

4.2.1. Tris[2-(N,N-dimethylcarbamoylmethoxy)phenyl]phosphine oxide (1). A mixture
of 0.98 g (3 mmol) of tris(2-hydroxyphenyl)phosphine oxide, 4.15 g (30 mmol) of K2CO3 , 1.24 g
(10 mmol) of N,N-dimethylchloroacetamide (see ESI), and 15 mL of DMF was heated with
magnetic stirring at 60 °C for 3 h. The mixture was evaporated to dryness in vacuum, 30 mL of
water and 30 mL of CH2Cl2 was added, the organic layer was separated, the aqueous layer was
extracted with CH2Cl2 (310 mL). The combined extracts were washed with water (210 mL) and
dried with Na2SO4. The solvent was removed in a vacuum to dryness and the residue was
crystallized from chloroform–hexane mixture to give 1 (1.58 g, 90.6%). Mp 183–184 °C. Anal.
Calc. for C30H36N3O7P: C, 61.95; H, 6.24; N, 7.22; P, 5.33%. Found: C, 61.79; H, 6.20; N, 7.07; P,
1
5.49. IR (KBr disk): νmax/cm–1 1671vs, 1666vs (C=O), 1178m (P=O). H NMR (500.13 MHz,
CDCl3, 0.02 M): δ 2.73 (9H, s, CH3), 2.84 (9H, s, CH3), 4.52 (6H, s, CH2), 7.00 (3H, dd, 3J3,4 = 8.4,
JH,P = 5.6, H-3), 7.05 (3H, td, 3J4,5 = J5,6 = 7.5, 4J3,5 = 1.2, H-5), 7.46 (3H, t, 3J3,4 = 3J4,5 = 7.8, H-4),
3
4
13
7.64 (3H, ddd, JHP = 14.8, 3J5,6 = 7.6, J4,6 = 1.4, H-6). C{1H} NMR (125.76 MHz, CDCl3, 0.02
M): δ 35.53 (s, N-CH3), 36.47 (s, N-CH3), 68.67 (s, OCH2), 112.93 (d, 3JC,P = 6.3, C-3), 121.39 (d,
3JC,P = 12.7, C-5), 121.67 (d, 1JC,P = 110.4, C-1), 133.53 (d, 4JC,P = 1.8, C-4), 134.40 (d, 2JC,P = 8.6,
C-6), 160.19 (d, 2JC,P = 2.1, C-2), 167.63 (s, C=O). 31P{1H} NMR (202.46 MHz, CDCl3, 0.02 M): δ
23.9 (s). Slow crystallization from the mother liquor resulted in single crystals of DMF solvate of
ligand 1 (mp 171–172 ºC) suitable for X-ray diffraction study.
4.2.2. Tris[2-(N,N-dicyclohexylcarbamoylmethoxy)phenyl]phosphine oxide (3) was
obtained in similar manner. Yield 82%, mp 145–147 °C. Anal. Calc. for C60H84N3O7P: C, 72.77; H,
8.55; N, 4.24; P, 3.13%. Found: C, 72.74; H, 8.69; N, 4.25; P, 3.21. IR (KBr disk): νmax/cm–1
1
1660sh, 1641vs (C=O), 1183m (P=O). H NMR (500.13 MHz, CDCl3, 0.01 M): δ 1.00–1.80 (54H,
m, CH2 (cyclo-Hex)), 2.39 (6H, br s, CH2 (cyclo-Hex)), 2.91 (3H, br s, N–CH), 3.20–3.30 (3H, m,
3
4
3
N–CH), 4.29 (6H, s, CH2O), 6.97 (3H, dd, J3,4 = 8.3, JH,P = 5.3, H-3), 7.02 (3H, td, J5,6 = 3J5,4
=
7.5, 4J5,3 = 1.5, H-5), 7.39 (3H, t, J4,5 = 3J4,3 = 7.5, H-4), 7.74 (3H, dd, J6,5 = 7.3, 3JH,P = 14.3, H-
6). 13C{1H} NMR (125.76 MHz, CDCl3, 0.01 M): δ 25.25 (s, CH2 (cyclo-Hex)), 25.30 (s, CH2
(cyclo-Hex)), 25.68 (s, CH2 (cyclo-Hex)), 26.55 (s, CH2 (cyclo-Hex)), 29.77 (s, CH2 (cyclo-Hex)),
3
3
31.20 (s, CH2 (cyclo-Hex)), 55.90 (s, N–CH), 56.85 (s, N–CH), 70.33 (s, CH2O), 114.74 (d, 3JCP
=
2
1
4
6.4, C-3), 121.60 (d, JCP = 12.5, C-5), 122.94 (d, JCP = 110.3, C-1), 133.04 (d, JCP = 1.3, C-4),
134.43 (d, JCP = 8.8, C-6), 161.26 (d, JCP = 2.5, C-2), 166.83 (s, C=O). P{1H} NMR (202.46
2
2
31
MHz, CDCl3, 0.01 M): δ 24.82 (s).
4.3. Synthesis of lanthanides(III) complexes
4.3.1. General procedure for the synthesis of 6–14. The complexes 6–14, including those
suitable for X-ray analysis, were prepared according to a similar procedure, with a ratio of reagents
of 1 : 1. A solution of Ln(NO3)3∙xH2O in acetonitrile was added dropwise with stirring to a solution
of ligand in chloroform or MeCN. The yields were 70–90%, but no attempts were made to optimize
the yield for each individual complex.
4.3.1.1. [La(1)(NO3)3], 6. A solution of 0.0335 g (0. 0773 mmol) of La(NO3)3∙6H2O in 3
mL of acetonitrile was added dropwise with stirring to a solution of 0.0449 g (0.0773 mmol) of
ligand 1 in 3 mL of chloroform. The resultant transparent solution was stirred at ambient
temperature for 1 h. The solution was evaporated to dryness under reduced pressure to give 0.06 g
of solid. The residue was washed with anhydrous ether and dried in vacuo (~ 1 Torr) at 62 °C to
give 0.057 g (81%). Mp 162–163 ºC. Anal. Calc. for C30H36LaN6O16P: C, 39.75; H, 4.00; N, 9.27%.
Found: C, 38.97; H, 3.71; N, 9.44. IR (KBr disk): νmax/cm−1 1631s, 1660sh (C=O), 1121m (Р=О),
1
1460s (N=O), 1290s (NO2)as, 1032w (NO2)s. H NMR (500.13 MHz, CD3CN, 0.01 M): δ 2.88
(9H, s, CH3), 2.92 (9H, s, CH3), 4.73 (6H, s, CH2), 7.12–7.15 (6H, m, H-3 + H-5), 7.50 (3H, dd,
3
3
3
3JHP = 15, J5,6 = 10, H-6,), 7.66 (3H, t, J3,4 = J4,5 = 7.5, H-4). 13C{1H} NMR (125.75 MHz,
CD3CN, 0.01 M): δ 35.20 (s, N–CH3), 35.62 (s, N–CH3), 65.82 (s, CH2O), 113.48 (d, 3JCP = 6.3, C-
3), 121.89 (d, JCP = 12.5, C-5), 134.41 (d, JCP = 10.0, C-6), 135.00 (s, C-4), 159.94 (s, C-2),
3
2
168.48 (s, C=O). No signal of C-1 nucleus expected due to shift at ~117 ppm was observed because

31
it is obscured by the solvent signal. Р{1H} NMR (202.46 MHz, CD3CN, 0.01 M): δ 32.0 (s, W1/2
= 0.05).
4.3.1.2. [Nd(1)(NO3)3], 7. A solution of 0.0472 g (0.1078 mmol) of Nd(NO3)3∙6H2O in 3
mL of acetonitrile was added dropwise on stirring to a solution of 0.0627 g (0.1078 mmol) of
ligand 1 in 3 mL of chloroform. The resultant transparent solution was stirred at ambient
temperature for 1 h. The solution was evaporated to dryness under reduced pressure to give 0.100 g
of solid. The residue was washed with anhydrous ether and dried in vacuo (~ 1 Torr) at 62 °C to
give 0.082 g (83%). Mp 233ºC. Anal. Calc. for C30H36N6NdO16P: C, 39.52; H, 3.98; N, 9.22%.
Found: C, 39.47; H, 3.94; N, 9.00. The residue (40 mg) was dissolved in 4.5 ml CH3CN. After a
few days, a light lilac crystals of [Nd(1)(NO3)3]·0.5CH3CN, formed, some of them were suitable for
X-ray diffraction study. The crystals were separated by decantation, washed with anhydrous ether
and dried in air (20 mg, 50%). On storage in air, especially upon trituration, the complex easily
loses solvent of crystallization. The IR band and Raman lines of the acetonitrile molecules were not
observed in the vibrational spectra of sample. The elemental analysis indicated that the formula of
crystals of is [Nd(1)(NO3)3]. Complex is not soluble in chloroform. IR (KBr disk): νmax/cm−1 1629,
1
1647sh, 1670sh (C=O), 1126 (P=O), 1465s (N=O), 1290s (NO2)as, 1032w (NO2)s. H NMR
(400.23 MHz, CD3CN, 0.01 M): the signals are very broad because of paramagnetic properties of
neodymium and could not provide precise integration and interpretation. 13C{1H} (100.61 MHz,
CD3CN, 0.01 M): δ 35.42 (s, N–CH3), 35.74 (s, N–CH3), 61.99 (br s, OCH2), 112.89 (s), 122.63 (d,
3JCP = 2.0), 135.37 (s), 137.43 (br s,),161.71 (s). No signals of ipso–Ph and C=O were observed.
31P{1H} NMR (161.98 MHz, CD3CN, 0.01 M): 121 (br s, W = 1).
½
4.3.1.3. [Lu(1)(NO3)3], 8. A solution of 44.1 mg (0.1062 mmol) Lu(NO3)3·3H2O in 2 ml of
MeCN was added dropwise on stirring to a solution of 61.7 mg (0.1062 mmol) 1 in 2 ml of MeCN.
The resultant transparent solution was stirred at ambient temperature for 1 h. In an hour, a white
fine-crystalline precipitate of 8 formed. One day later, the crystals were separated by decantation,
washed with anhydrous ether and dried in vacuo (~ 1 Torr) at 62 °C to give 0.093 g (93%). Mp
(with decomp.) 307–308 °C. Anal. Calc. for C30H36LuN6O16P: C, 38.23; H, 3.85; N, 8.92%. Found:
C, 38.14; H, 3.79; N, 9.00. IR (KBr disk): νmax/cm−1 1630s, 1660sh, 1670s (C=O), 1180m,1185sh
(Р=О), 1480s (N=O), 1300s (NO2)as, 1035w (NO2)s. Complex is virtually insoluble in common
solvents for NMR.
4.3.1.4. [La(2)(NO3)3], 9. This compound was synthesized according to the general method
similar to preparation of complex 7, starting with 0.0367 mmol (26.2 mg) La(NO3)3·6H2O and
0.0367 mmol (36.3 mg) 2. The mixture was concentrated in vacuo (~5 Torr) up to a volume of ~1.3
mL. The fine-crystalline white precipitate formed was filtered, washed by diethyl ether and dried in
vacuo (~1 Torr) at 62 °C to give 0.050 g (74.6%) of 9. Mp 112–114 °C. Anal. Calc. for
C48H72N6LaO16P: C, 49.74; H, 6.28; N, 7.25%. Found: C, 49.47; H, 6.24; N, 7.10. IR (KBr disk):
νmax/cm−1 1610vs, 1630sh, 1665sh (C=O), 1121m (Р=О), 1480s (N=O), 1300s (NO2)as, 1035w
1
(NO2)s. H NMR (400.13 MHz, CDCl3, 0.02 M): δ 0.86–0.91 (18H, m, CH3), 1.19–1.30 (12H, m,
CH3–CH2), 1.37–1.48 (12H, m, N–CH2–CH2), 3.03–3.07 (6H, m, N–CH2), 3.24–3.36 (6H, v br s,
N–CH2), 4.7 (6H, br s, CH2O), 6.96 (3H, br s, H-3), 7.04 (3H, br s, H-5), ca 7.4 (extremely br s, H-
6), 7.51–7.56 (3H, m, H-4). 13C{1H} NMR (100.61 MHz, CDCl3, 0.02 M): δ 13.78 (s, CH3), 13.92
(s, CH3), 19.99 (s, CH3–CH2), 20.05 (s, CH3–CH2), 29.41 (s, N–CH2–CH2), 30.51 (s, N–CH2–CH2),
1
46.73 (s, N–CH2), 47.08 (s, N–CH2), 65.97 (s, CH2O), 133.33 (s, C-3), ~117.7 (br d, JCP ~ 112, C-
3
1), 112.10 (d, JCP = 12.5, C-5), 134.62 (s, C-4), 134.98 (s, C-6), 160.04 (s, C-2), ~167.7 (br s,
C=O). 31P{1H} NMR (161.98 MHz, CDCl3, 0.02 M): δ 31.4 (s, W1/2 = 0.4 ppm).
4.3.1.5. [Lu(2)(NO3)3], 11. This compound was synthesized according to the general
method similar to the preparation of complex 9, starting from 0.0837 mmol (34.7 mg)
Lu(NO3)3·3H2O and 0.0837 mmol (69.8 mg) 2. The white precipitate, 0.080 g (80%). Mp 84–85
°C. Anal. Calc. for C48H72N6LuO16P: C, 48.24; H, 6.07; N, 7.03%. Found: C, 47.97; H, 6.14; N,
7.10. IR (KBr disk): νmax/cm−1 1613s, 1638sh, 1660sh(C=O), 1120sh (P=O), 1480s (N=O), 1300s
(NO2)as, 1035w (NO2)s. 1H NMR (400.13 MHz, CDCl3, 0.02 M): δ 0.91–0.95 (18H, m, CH3), ~1.3
(12H, br s, CH3–CH2), ~1.5 (12H, br s, N–CH2–CH2), ~3.1 (6H, br s, N–CH2), ~3.3 (6H, br s, N–

CH2), 4.7 (6H, br s, CH2O), 6.9 (3H, br s, H-3), 7.0 (3H, br s, H-5), ca 7.4 (~ 3H, v br s, H-6), 7.5
13
(3H, br s, H-4). C{1H } NMR (100.61 MHz, CDCl3, 0.02 M): δ 13.75 (s, CH3), 13.83 (s, CH3),
19.99 (s, CH3–CH2), 20.06 (s, CH3–CH2), 29.39 (s, N–CH2–CH2), 30.66 (s, N–CH2–CH2), 46.83 (s,
1
N–CH2), 47.21 (s, N–CH2), 65.60 (s, CH2O), 112.85 (s, C-3), 117.44 (d, JCP = 115, C-1), 121.73
(d, 3JCP = 12.0, C-5), 134.62 (d, 2JCP = 10.0, C-6), 134.75 (s, C-4), 160.40 (s, C-2), 167.80 (s, C=O).
31Р{1H} NMR (161.98 MHz, CDCl3, 0.02 M): δ 34.2 (br. s, W1/2 = 0.3)
4.3.1.6. [La(3)(NO3)3], 12. This compound was synthesized according to the general
method similar to preparation of complex 9, starting with 0.0532 mmol (23 mg) La(NO3)3·6H2O
and 0.0532 mmol (52.7 mg) 3. The white fine-crystalline precipitate, 0.061 g (87%). Mp 208–209
°C. Anal. Calc. for C60H84LaN6O16P: C, 54.79; H, 6.44; N, 6.39%. Found: C, 54.32; H, 6.48; N,
6.53. IR (KBr disk): νmax/cm−1 1606vs, 1630sh, 1656m (C=O), 1122m (Р=О), 1480s (N=O), 1300s
1
(NO2)as, 1035w (NO2)s. H NMR (500.13 MHz, CDCl3, 0.02 M): δ 1.15–1.70 (br m, 60H, CH2
(cyclo-Hex)), ~2.9 (~3H, br s, CH (cyclo-Hex)), ~3.1 (~ 3H, br s, CH (cyclo-Hex)), ~4.6 (~ 6H, br
s, CH2O), 6.90–7.15 (9H, br m, Ar-H), 7.5–7.65 (~ 3H, br m, Ar-H). 13C{1H} NMR (125.75 MHz,
CDCl3, 0.02 M): δ 24.98 (s, CH2 (cyclo-Hex)), 25.66 (s, CH2 (cyclo-Hex)), 26.42 (s, CH2 (cyclo-
Hex)), 29.47 (s, CH2 (cyclo-Hex)), 30.76 (br s, CH2 (cyclo-Hex)), 57.2 (br s, N–CH), ~ 69.0 (v br s,
CH2O), ~ 117.3 (v br s, C-1), 122.68 (s, C-5), 134.67 (s, C-6 + C-4), 159.97 (s, C-2), 167.30 (br s,
C=O). 31P{1H} NMR (202.46 MHz, CDCl3, 0.02 M): δ 31.4 (br s, W1/2 = 0.5).
4.3.1.7. [Nd(3)(NO3)3], 13. This compound was synthesized according to the general
method similar to preparation of complex 9, starting with 0.0530 mmol (23.2 mg) Nd(NO3)3·6H2O
and 0.0530 mmol (52.5 mg) 3. The fine-crystalline precipitate, 0.0567 g (81%). Mp 203–204 °C.
Anal. Calc. for C60H84N6NdO16P: C, 54.57; H, 6.41; N, 6.36%. Found: C, 54.45; H, 6.28; N, 6.40.
IR (KBr disk): νmax/cm−1 1604s, 1625sh, 1660sh (C=O), 1123m (Р=О), 1480s (N=O), 1300s
1
(NO2)as, 1035w (NO2)s. In H NMR spectrum, the proton signals of CH2 c-Hex groups are
considerably broadened. No signals for the remaining groups the CH and CH2 protons are observed.
13C{1H} NMR (100.61 MHz, CDCl3, 0.02 M): δ 24.71 (s), 24.91 (s), 25.26 (s), 26.35 (s), 28.8 (br
s), 30.0 (br s), 56.7 (br s), 58.4 (v br s), 66.5 (v br s), 114.3 (v br s), 123.45 (br s), 134.90 (br s).
31P{1H} NMR (161.98 MHz, CDCl3, 0.02 M): δ 93 (br s, W1/2 = 5.4).
4.3.1.8. [Lu(3)(NO3)3], 14. This compound was synthesized according to the general
method similar to preparation of complex 9, starting with 0.0518 mmol (21.5 mg) Lu(NO3)3·3H2O
and 0.0518 mmol (51.3 mg) 3. The white fine-crystalline precipitate, 0.060 g (85%). Mp 198–199
°C. Anal. Calc. for C60H84LuN6O16P: C, 53.33; H, 6.27; N, 6.22%. Found: C, 53.02; H, 6.38; N,
6.33. IR (KBr disk): νmax/cm−1 1608s, 1630sh, 1659s (C=O), 1123m (Р=О), 1480s (N=O), 1300s
1
(NO2)as, 1035w (NO2)s. In H NMR spectrum, the proton signals of all groups are considerably
broadened and could not be integrated (Fig. S19). 1H NMR (400.13 MHz, CDCl3, 0.02 M): δ 1.13–
1.83 (br m, CH2 c-C6H11), ~2.9 (v br s), ~3.1 (v br s), ~4.7 (v br s, CH2O), 7.0 (br s, Ar-H), 7.1 (br
13
s, Ar-H), ca 7.6 (v br m, Ar-H). C{1H } NMR (100.61 MHz, CDCl3, 0.02 M): δ 25.04 (s, CH2
(cyclo-Hex)), 25.65 (s, CH2 (cyclo-Hex)), 26.44 (s, CH2 (cyclo-Hex)), 29.75 (s, CH2 (cyclo-Hex)),
30.82 (s, CH2 (cyclo-Hex)), 56.88 (s, N–CH), 57.28 (s, N–CH), ~ 68.1 (v br s, CH2O), 114.92 (s, C-
3), 122.45 (d, 3JCP = 12.5, C-5), 134.82 (s, C-4), 134.99 (s, C-6), 160.18 (d, 2JCP = 2.5, C-2), 166.50
(v br s, C=O). 31Р{1H} NMR (161.98 MHz, CDCl3, 0.02 M): δ 35.7 (br. s, W1/2 = 0.6), 35.1 (sh).
4.4. General procedure for the preparation of model solution with metal:ligand ratios of 1:2
To prepare solution with metal : ligand molar ratio of 1:2, a calculated amount of ligand was added
to a solution of corresponding 1:1 complex in CD3CN or CDCl3.
4.5. X-ray crystallography
Single crystals of the 1·DMF, 2, and 7·0.5 MeCN were grown from their saturated solutions in
DMF, CHCl3 and MeCN, respectively, at room temperature. The intensities of reflections were
measured with a Bruker Apex II CCD diffractometer using graphite monochromated MoK
radiation (for 1·DMF and 7·0.5MeCN,  = 0.71073 Å) or CuK radiation with multilayer optics
(for 2,  = 1.54178 Å). The structures were solved by the direct method and refined by full-matrix

least squares on F2. Non-hydrogen atoms were refined in anisotropic approximation. The unit cell
of crystal of ligand 1 contains one solvate DMF molecules which have been treated as a diffuse
contribution to the overall scattering without specific atom positions by SQUEEZE/PLATON [22].
Chemical formula, formula weight and dc were calculated taking the solvate molecules into
account. Positions of the hydrogen atoms were calculated. All hydrogen atoms were included in the
refinement by the riding model with Uiso(H) = nUeq(C), where n = 1.5 for methyl groups and 1.2 for
the other atoms. All calculations were made using the SHELXL-2015 [23]] and OLEX2 [24]
program packages. The main crystallographic data and experimental details are collected in Table
6.
Table 6. Crystallographic data and refinement parameters for 1·DMF, 2 and 7·0.5MeCN
7·0.5MeCN
C31H37.5N6.5NdO16P
932.38
Compound
Empirical formula
Fw
1·DMF
C33H43N4O8P
654.68
2
C48H72N3O7P
834.05
Color, habit
Crystal size (mm3)
F(000)
Light yellow, prism
0.32 × 0.31 × 0.26
1392
Colorless, plate
0.26 × 0.10 × 0.04 0.32 × 0.31 × 0.26
904
120
Light pink, prism
944
120
T, K
120
Space group, Z
Monoclinic, P 21/c, 4
Triclinic, P
12.3182(1)
13.7729(2)
16.0655(2)
68.309(1)
68.382(1)
85.757(1)
2348.38(5)
1.180
1
, 2
Triclinic, P , 2
1
a (Å)
b (Å)
c (Å)
α (°)
16.082(3)
22.421(4)
9.0671(15)
90
95.266(4)
90
3255.7(9)
1.336
0.142
10.6694(16)
12.1311(19)
15.608(2)
93.779(4)
95.448(3)
91.022(3)
2006.1(5)
1.544
β (°)
γ (°)
V (Å3)
dc (g/cm3)
(MoK) (cm−1)
θmax ()
Ihklcoll/uniq
Rint
0.927
67.79
1.409
28.99
15721 / 10398
0.024
29.64
18015 / 7918
0.082
29268 / 7988
0.024
Obs. refl. / N / restraints 3865 / 370 / 0
7207 / 538 / 0
0.039
0.085
1.00
1574777
9158 / 509 / 1
0.060
0.142
1.03
1574778
R,a % [I > 2σ(I)]
Rw,b %
0.088
0.181
1.05
GOFc
Refcoded
1574776
aR =  Fo – Fc / Fo bRw = [(w(Fo2 – Fc2)2)/(w(Fo2))]1/2. сGOF = [w(Fo2 – Fc2)2/(Nobs – Nparam)].1/2 d Code of compound at the CSD.
    .

4.6. Electrospray ionization mass spectrometry (ESI-MS)
The ESI mass spectra were recorded using a Finnigan LCQ Advantage mass spectrometer with 50–
2000 m/z range octapole ion trap mass analyzer (Thermo Electron Corp., San Jose, CA, USA) and
XCalibur version 1.3 equipped with Surveyor MS pump and Surveyor autosampler with MeCN as
mobile phase. The temperature of heated capillary was kept at 120 °C. Nitrogen was used as the
sheath and auxiliary gas and was set at 10 and 10 psi, respectively. The spray voltage was kept
under 4.5 kV. The distance between the needle and the counter electrode was 1 cm. Samples were
introduced directly in source with 5 μL min–1 by syringe pump. The full scan modes from 50 to
1800 Da and constant cone voltage at 13 V were used. For sample preparation, the measured
amount (0.9–1.2 mg) of compounds was dissolved in 1.00 mL MeCN and sonicated. The stock
solutions were further series diluted up to concentrations 1.5·10–5 M. The fresh analyte solutions
were immediately introduced into the mass spectrometer. The spectra of all studied compounds
were recorded under the same conditions and at the same concentrations.
4.7. Extraction of lanthanides(III)

1,2-Dichloroethane (DCE) of reagent grade was used without additional purification as the organic
solvent. Solutions of extractants at 0.05 M concentration were prepared from accurately weighed
samples. The initial aqueous lanthanide(III) solutions were prepared by dissolving the respective
nitrates in water, followed by the addition of NH4NO3. The initial concentrations of metal ions were
4·10–6 M, the concentration of NH4NO3 was 3 M. The phases were contacted at room temperature
by agitation with a stirrer at 60 rpm for 1 h, which is sufficient to establish constant values of
distribution ratios. The concentration of lanthanides(III) in the initial and equilibrated aqueous
solutions was determined by mass spectrometry with inductively coupled plasma ionization of
samples (ICP-MS), using a Thermo Elemental X-7 mass spectrometer according to a published
method [25]. The content of elements in the organic phase was determined after back extraction
with a 0.1 М solution of 1-hydroxyethane-1,1-diphosphonic acid. The distribution ratios for the
elements were calculated as ratios of the equilibrium concentration in the organic and aqueous
phases (DM = [Morg]/[Maq]). The error of the determined DM values did not exceed 5%.
The distribution ratios (DL = [Lorg]/[Laq]) for the extractants 1–3 were calculated as ratios of
the equilibrium concentration in the organic and aqueous phases. The initial concentration of the
extractants in DCE was 0.05 M, the concentration of NH4NO3 in aqueous solution was 3 M. The
concentration of extractants in the equilibrium aqueous solutions was evaluated by phosphorus
content determination using inductively coupled plasma atomic emission spectrometry (ICP-AES)
on an ICAP-61 spectrometer (Thermo Jarrel Adh).
Acknowledgements
This work was supported by the Russian Foundation for Basic Research (Grant No. 17–03–00800).
VVK acknowledges partial financial support from the Ministry of Education and Science of the
Russian Federation within the framework of the Competitiveness Enhancement Program of NUST
MISiS (No. K2-2016-070). The contribution of the Center for Molecule Composition Studies,
Nesmeyanov Institute of Organoelement Copmpounds, Russian Academy of Science is gratefully
acknowledged.
Appendix A. Supplementary data CCDC 1574776–1574778 contains the supplementary
crystallographic data for 1, 2 and 7, respectively. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Appendix B. Supplementary data associated with this article can be found, in the online version, at
http://...
References
[1] (a) J.A. Kitchen, Coord. Chem. Rev. 340 (2017) 232; (b) A.J. Amoroso, I.A. Fallis, S.J.A. Pope,
Coord. Chem. Rev. 340 (2017) 198; (c) C. Bazzicalupi, A. Bianchi, E. Garcнa-Espaсa, E.
Delgado-Pinar, Inorg. Chim. Acta 417 (2014) 3; (d) N.C. Martinez-Gomez, H N. Vu, E.
Skovran, Inorg. Chem. 55 (2016) 10083; (e) D.N. Woodruff, R.E.P. Winpenny, R.A. Layfield,
Chem. Rev. 113 (2013) 5110; (f) S.N. Misra, M.A. Gagnani, I. Devi M., R.S. Shukla, Bioinorg.
Chem. Appl. 2(2004) 155; (g) M. Murugesu, E.J. Schelter, Inorg. Chem. 55 (2016) 9951; (h) J.-
C.G. Bünzli, J. Coord. Chem. 67 (2014) 3706; (i) M.C. Heffern, L.M. Matosziuk, T.J. Meade,
Chem. Rev. 114 (2014) 4496; (j) L.-J. Xu, G.-T. Xu, Z.-N. Chen, Coord. Chem. Rev. 273–274
(2014) 47; (k) Y. Zheng, C.C. Zhang, Q. Wang, Sensors and Actuators, B 245 (2017) 622; (l)
A.A. Trifonov, D.M. Lyubov, Coord. Chem. Rev. 340 (2017) 10; (m) L. Sorace, C. Benelli, D.
Gatteschi, Chem. Soc. Rev. 40 (2011) 3092; (n) S. Cotton, Lanthanide and Actinide Chemistry,

Wiley, 2006; (o) Luminescence of Lanthanide Ions in Coordination Compounds and
Nanomaterials, first ed., Wiley, 2014.
[2] (a) G. Parkin, Polyhedron 125 (2017) 1; (b) A. de Bettencourt-Dias, J.S.K. Rossini, Inorg.
Chem. 55 (2016), 9954; (c) R. Sessoli, A.K. Powell, Coord. Chem. Rev. 253 (2009) 2328 and
references cited therein.
[3] F. Silva, C. Fernandes, M.P.C. Campello, A. Paulo, Polyhedron 125 (2017) 186 and references
cited therein.
[4] (a) P.K. Mohapatra, M. Iqbal, D.R. Raut, W. Verboom, J. Huskens, V.K. Manchanda, J.
Membr. Science 375 (2011) 141; (b) B.N. Mahanty, P.K. Mohapatra, D.R. Raut, D.K. Das,
P.G. Behere, Md. Afzal, W. Verboom, J. Environ. Chem. Eng. 4 (2016) 1826; (c) P.A. Gale,
J.T. Davis, R. Quesada, Chem. Soc. Rev. 46 (2017) 2497.
[5] (a) Y. Zhu, Y.-M. Wang, J. Xu, P. Liu, H.A.B.M.D.Weththasinha,Y.-L.Wu, X.-Q. Lu, J.-M.
Xie, J. Solid State Chem. 219 (2014) 259; (b) S.V. Eliseeva, J.-C.G. Bünzli, Chem. Soc. Rev.
39 (2010) 189;(c) A.B. Aletti, D.M. Gillen, T. Gunnlaugsson, Coord. Chem. Rev. (2017) DOI:
10.1016/j.ccr.2017.06.020.
[6] (a) A. Leoncini, S.A. Ansari, P.K. Mohapatra, A. Boda, S.M. Ali, A. Sengupta, J. Huskens, W.
Verboom, Dalton Trans. 46 (2017) 1431; (b) H.T. Sartain, S.N. McGraw, C.L. Lawrence, E.J.
Werner, S.M. Biros, Inorg. Chim. Acta 426 (2015) 126; (c) S.A. Ansari, P.K. Mohapatra, J.
Chromatography A 1499 (2017) 1; K. Matloka, A.K. Sah, M.W. Peters, P. Srinivasan, A.V.
Gelis, M. Regalbuto, M.J. Scott, Inorg. Chem. 46 (2007) 10549; (d) E.V. Sharova, O.I.
Artyushin, A.N. Turanov, V.K. Karandashev, S.B. Meshkova, Z.M. Topilova, I.L. Odinets,
Centr. Eur. J. Chem. 10 (2012) 146.
[7] (a) M. Chen, H. Zhao, Z.-W. Wang, E.C. Sañudo, C.-S. Liu, Inorg. Chem. Commun. 56 (2015)
48; (b) E. Lucaccini, J.J. Baldoví, L. Chelazzi, A.-L. Barra, F. Grepioni, J.-P. Costes, L. Sorace,
Inorg. Chem. 56 (2017) 4728.
[8] I.Yu. Kudryavtsev, T.V. Baulina, M.P. Pasechnik, S.V. Matveev, A.G. Matveeva,
Phosphorus, Sulfur, and Silicon and the Related Elements 189 (2014) 946.
[9] I.Yu. Kudryavtsev, T.V. Baulina, V.N. Khrustalev, P.V. Petrovskii, M.P. Pasechnik and E.E.
Nifant’ev, Doklady Chemistry 448 (2013) 55
[10] J. Fawcett, A.W.G. Platt, S. Vickers, M.D. Ward, Polyhedron 23 (2004) 2561
[11] L.J. Caudle, E.N. Duesler, and R.T. Paine, Inorg. Chem. 24 (1985) 4441.
[12] E.V. Sharova, O.I. Artyushin, Yu.V. Nelyubina, K.A. Lyssenko, M.P. Passechnik, I.L.
Odinets, Russ. Chem. Bull. 57 (2008) 1890
[13] (a) A.G. Matveeva, A.V. Vologzhanina, E.I. Goryunov, R.R. Aysin, M.P. Pasechnik, S.V.
Matveev, I.A. Godovikov, A.M. Safiulina, and V.K. Brel, Dalton Trans. 45 (2016) 5162; (b) A.
Bowden, S.J. Coles, M.B. Pitak, A.W.G. Platt, Polyhedron 68 (2014) 258; (c) A.G. Matveeva,
A.S. Peregudov, E.I. Matrosov, Z.A. Starikova, S.V. Matveev, E.E. Nifant'ev, Inorg. Chim.
Acta 362 (2009) 360; (d) M. Atanassova, V. Lachkova, N. Vassilev, S. Varbanov, I. Dukov,
Polyhedron 29 (2010) 655. (e) A.W.G. Platt, Coord. Chem. Rev. 340 (2017) 62.
[14] S Wahu, J.-C. Berthet, P. Thuéry, D. Guillaumont, M. Ephritikhine, R. Guillot, G. Cote and C.
Bresson, Eur.J. Inorg. Chem. (2012) 3747.
[15] D.A. Atwood, The Rare Earth Elements: Fundamentals and Applications, 1st ed.; John Wiley
and Sons Ltd.: Chichester, 2012, pp. 501-536
[16] A.N. Turanov, V.K. Karandashev, V.E. Baulin, I.P. Kalashnikova, E.V. Kirillov, S.V. Kirillov,
V.N. Rychkov and A.Yu. Tsivadze, Russ. J. Inorg. Chem. 61 (2016) 377
[17] W.L.F.Armarego, C.L.L. Chai, Purification of Laboratory Chemicals, 6th ed., Elsevier:
Amsterdam, Boston, 2009.
[18] N.E. Gel'man, Е.А. Terent'eva, T.M. Shanina, L.M. Kiparenko and V. Rezl, Methods of
Quantitative Organic Elemental Microanalysis [in Russian]; Khimiya: Moscow, 1987.
[19] E.V. Sharova, O.I. Artyushin, A.S. Shaplov, G.V. Myasoedova and I.L. Odinets, Tetrahedron
Lett. 49 (2008) 1641]

[20] T. Miyazawa, K. Tanaka, E. Ensatsu, R. Yanagihara, T. Yamada, J. Chem. Soc., Perkin Trans.
1, (2001) 87.
[21] T. Gramstad, W.J. Fuglevik, Acta Chem. Scand., 16 (1962) 1369
[22] A.L. Spek, Acta Crystallogr., Sect. C C71 (2015) 9.
[23] G.M. Sheldrick, Acta Crystallogr., Sect. C C71 (2015) 3.
[24] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard and H. Puschmann, J. Appl. Cryst.
42 (2009) 339.
[25] A.N. Turanov, V.K. Karandashev, V.E. Baulin, E.N. Tsvetkov, Russ. J. Inorg. Chem. 40
(1995) 1926.

Coordination and extraction of lanthanides(III) with tripodal ligands on the
triphenylphosphine oxide platform: Effect of uncoordinated substituents
Anna G. Matveeva, Igor Yu. Kudryavtsev, Margarita P. Pasechnik, Anna V. Vologzhanina, Tatyana
V. Baulina, Anna V. Vavina, Georgiy Ya. Sukat, Sergey V. Matveev, Ivan A. Godovikov, Alexander
N. Turanov, Vasilii K. Karandashev and Valery K. Brel
New tripodal ligands were synthesized and characterized. Nine lanthanide 1:1 complexes were
synthesized and studied by IR and X-ray diffraction. Solution structure of 1:1 and 1:2 complexes
was studied by IR, multinuclear NMR spectroscopy, and ESI-MS. Effect of non-coordinating
substituents at N atom on coordination and extraction properties was revealed.