Synthesis and spectral studies of lanthanides coordination compounds based on N-(diphenylphosphoryl)benzamide. the structure of N-(diphenylphosphoryl) benzamide

Article abstract of DOI:10.1016/j.molstruc.2014.03.069

N-(diphenylphosphoryl)benzamide (HL), its sodium salt and new lanthanide coordination compounds of general formula LnL₃ i-PrOH, LnL ₃Dipy LnL₃Phen (Ln = La, Nd, Eu, Gd, Tb; Dipy = α,α′ - dipyridyl; Phen = 1,10-phenanthroli

Full text of DOI:10.1016/j.molstruc.2014.03.069

Journal of Molecular Structure 1068 (2014) 71–76
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and spectral studies of lanthanides coordination
compounds based on N-(diphenylphosphoryl)benzamide.
The structure of N-(diphenylphosphoryl)benzamide
a
a
b
b,c
Nataliia S. Kariaka a, , Victor A. Trush , Tatiana Yu. Sliva , Viktoriya V. Dyakonenko , Oleg V. Shishkin
,
⇑
Vladimir M. Amirkhanov a,1
a Kyiv National Taras Shevchenko University, Department of Chemistry, 64/13, Volodymyrska Street, Kyiv 01601, Ukraine
b SSI ‘‘Institute for Single Crystals’’, National Academy of Science of Ukraine, Lenina ave. 60, 61001 Khar’kov, Ukraine
c Department of Inorganic Chemistry, V. N. Karazin Kharkiv National University, 4 Svobody sq., Kharkiv 61202, Ukraine
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
The crystal structure of
N-(diphenylphosphoryl)benzamide
(HL) was solved.
The novel highly luminescent
lanthanide complexes were
synthesized.
TG analysis and spectral studies were
used to characterize synthesized
compounds.
ꢀ
ꢀ
The luminescence properties of Eu(III)
and Tb(III) complexes were studied.
HL efficiency as lanthanide emission
sensitizer was evaluated.
a r t i c l e i n f o
a b s t r a c t
Article history:
N-(diphenylphosphoryl)benzamide (HL), its sodium salt and new lanthanide coordination compounds
a0 – dipyridyl;
Phen = 1,10-phenanthroline) have been synthesized. The crystal structure of HL was solved. The poly-
Received 20 January 2014
Received in revised form 17 March 2014
Accepted 28 March 2014
Available online 8 April 2014
of general formula LnL3ꢁi-PrOH, LnL3Dipy LnL3Phen (Ln = La, Nd, Eu, Gd, Tb; Dipy =
a,
meric frame of N-(diphenylphosphoryl)benzamide crystal structure was established. The infinite
´
chains of molecules are formed by the NAHꢁꢁꢁO type hydrogen bonds linking neighboring molecules.
The synthesized coordination compounds were studied by means of thermo gravimetric analysis, IR,
NMR 1H, 31P, absorption and luminescence spectroscopy at 298 and 77 K. The obtained Eu (III) and
Tb (III) complexes luminescence characteristics dependence on triplet states of ligands in complexes
is discussed.
Keywords:
Carbacylamidophosphates
Lanthanide
Luminescense
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
For the last few decades the new luminescent materials for pos-
sible application in modern technologies have been actively
retrieved. Therein, lanthanides coordination compounds with
organic ligands, which can be used in lasers, light emitting diodes
and displays devices [1,2], responsive luminescent stains for
⇑
Corresponding author. Tel.: +380 442393392.
E-mail addresses: natka04@i.ua (N.S. Kariaka), v_amirkhanov@yahoo.com
(V.M. Amirkhanov).
1
Fax: +380 442393393.
http://dx.doi.org/10.1016/j.molstruc.2014.03.069
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

72
N.S. Kariaka et al. / Journal of Molecular Structure 1068 (2014) 71–76
biomedical analysis, medical diagnostics and cell imaging [2–4] are
very interesting objects for investigation. Among the most popular
and the most intensively investigated lanthanide coordination
compounds there are lanthanide b-diketonates and their structural
analogs. The explanation is in the variety and relatively easy
synthesis of these ligands, and in unique luminescence properties
of their complexes [1–5].
d = 17.2 (s). – C19H15NNaO2P (343.3): calcd. C 66.48, H 4.40, N
4.08; found C 66.54, H 4.32, N 4.01.
Coordination compounds of general compositions LnL3ꢁi-PrOH
and LnL3Q were synthesized according to the following schemes:
LnðNO3Þ3 ꢁ nH2O þ 3NaL þ i ꢂ PrOH ! LnL3 ꢁ i ꢂ PrOH
þ 3NaNO3 # þnH2O
It is well known that direct excitation into the 4f excited levels
rarely yields highly luminescent materials. Therefore, an alternative
path, so called luminescence sensitization or antenna effect, has
been worked out. According to the luminescence mechanism,
occurred in coordination compounds, which consist of the initial
excitation of the chromophore (antenna) and further energy transfer
to lanthanide ion, the first and an important step in fluorescent lan-
thanide complexes creation is the ligand fitting [2]. Effective sensiti-
zation of lanthanide luminescence can be expected for complexes
with N-(diphenylphosphoryl)benzamide – ligand that contain tree
powerful antenna. Besides that it has rather high melting point,
which allows us to consider further practical application. The
present work is the continuation of systematic investigations of
complexes with carbacylamidophosphates (CAPh), compounds of
LnðNO3Þ3 ꢁ nH2O þ 3NaL þ Q ! LnL3Q þ 3NaNO3 #
þ nH2OðQ ¼ Dipy or Phen; Ln ¼ La; Nd; Eu; Gd; TbÞ
Preparation of LnL3ꢁi-PrOH (Ln = La, Nd, Eu, Gd, Tb)
Hydrated Ln(III) nitrate (1 mmol) was dissolved in isopropanol
(15 ml) and added to the solution of NaL (3 mmol) in 15 ml of ace-
tone and heated to the boiling point. After cooling during ꢃ15 min
the precipitated NaNO3 was filtered off. The resulting clear solution
was left at ambient temperature in desiccator over anhydrous
CaCl2. In a day the coordination compounds precipitated as pow-
ders were filtered, washed with suction by cold i-PrOH and finally
dried on air (Yield ꢃ 80%). Anal. Calc. for C60H53N3O6P3La
(Mr = 1143,22): C, 63.04; H, 4.67; N, 3.66%. Found: C, 63.09; H,
´
general formula RCONHPOR2 [6–9] and devoted to new lumines-
4.54; N, 3.61%. .M. p. 125 °C. – IR (KBr): mmax = 1590, 1509 (C@O),
cence materials creation. Herein we report the structure of
N-(diphenylphosphoryl)benzamide, synthesis and properties of
some types of lanthanide coordination compounds based on HL.
1438, 1385, 1178, 1128 (P@O), 1066, 910, 726, 694, 549 cmꢂ1
.
–
1H NMR (DMSO-d6): d ꢃ 7.26–7.48 (m, 27H, Ph, Ph2), 7.88 (m,
12H, Ph2), 8.22 (d, 6H, Ph), 1.06 (d, 6H, CH3), 3.79 (h, 1H, CH),
4.09 (d, 1H, OH). Anal. Calc. for C60H53N3O6P3Nd
(Mr = 1146.22): C, 62.87; H, 4.66; N, 3.67%. Found: C, 62.90; H,
Experimental section
4.60; N, 3.63%. .M. p. 130 °C. – IR (KBr):
mmax = 1590, 1507 (C@O),
1437, 1383, 1178, 1128 (P@O), 1066, 910, 726, 693, 549 cmꢂ1
.
Methods
Anal. Calc. for C60H53N3O6P3Eu (Mr = 1157.24): C, 62.27; H,
4.62; N, 3.63%. Found: C, 62.34; H, 4.61; N, 3.60%. .M. p. 135 °C. –
IR measurements were performed on a Perkin–Elmer Spectrum
BX spectrometer on samples in form of KBr pellets.
IR (KBr): mmax = 1590, 1508 (C@O), 1438, 1384, 1179, 1128 (P@O),
1H and 31P NMR spectra in DMSO-d6 solutions were obtained
on a AVANCE 400 Bruker NMR spectrometer at room temperature.
Chemical shifts are reported references to SiMe4 as interior stan-
dard for 1H NMR and H3PO4 as exterior standard for 31P NMR. Ele-
mental analyses (C, H, N) were performed on an EL III Universal
CHNOS Elemental Analyzer.
1066, 909, 727, 693, 549 cmꢂ1. Anal. Calc. for C60H53N3O6P3Gd
(Mr = 1157.24): C, 62.01; H, 4.60; N, 3.62%. Found: C, 62.14; H,
4.56; N, 3.59%. .M. p. 135 °C. – IR (KBr):
mmax = 1591, 1509 (C@O),
1438, 1385, 1179, 1128 (P@O), 1067, 911, 727, 694, 549 cmꢂ1
.
Anal. Calc. for C60H53N3O6P3Tb (Mr = 1163.24): C, 61.95; H,
4.60; N, 3.61%. Found: C, 62.01; H, 4.57; N, 3.58%. .M. p. 130 °C.
The diffuse reflection spectra are recorded on UV VIS spectro-
photometer Specord M 40 Carl Zeiss.
The thermal stabilities of Eu(III) complexes have been deter-
mined between 20 °C and 1000 °C in air with a heating rate of
10 °C minꢂ1 by thermal gravimetric (TG) and differential thermal
analyses (DTA).
Emission and excitation spectra of the complexes were mea-
sured on «Fluorolog FL 3-22» spectrofluorimeter at 298 and 77 K.
The energies of triplet states of ligands in complexes were deter-
mined on the base of the phosphorescence spectra registered for
La(III) and Gd(III) complexes at 77 K. The f–f-luminescence lifetime
measurements at room temperature were obtained using the
FL-1040 ‘‘Horiba Jobin Yvon’’ phosphorimeter accessory with the
–IR (KBr):
mmax = 1591, 1509 (C@O), 1438, 1385, 1179, 1128
(P@O), 1067, 911, 727, 694, 549 cmꢂ1
.
Preparation of LnL3ꢁDipy (Ln = La, Nd, Eu, Gd, Tb)
Hydrated Ln(III) nitrate (1 mmol) was dissolved in isopropanol
(15 ml) and added to the solution of NaL (3 mmol) in 15 ml of ace-
tone. Then 1 mmol of solid Dipy was added. The resulted mixture
was boiled for some minutes and then cooled to the room temper-
ature. After 15 min the precipitated NaNO3 was filtered off. The
resulting clear solution was left at ambient temperature in desicca-
tor over anhydrous CaCl2. In a day the coordination compounds
precipitated as powders were filtered, washed with suction by cold
i-PrOH and finally dried on air (Yield ꢃ90%). Anal. Calc. for
C67H53N5O6P3La (Mr = 1255.23): C, 64.11; H, 4.26; N, 5.58%.
Found: C, 64.14; H, 4.22; N, 5.55%. .M. p. 130 °C. – IR (KBr):
Fluorolog 3-22 instrument (pulsed Xe–Hg arc lamp, 3 ls bandwidth).
Synthesis
mmax = 1590, 1507 (C@O), 1437, 1384, 1178, 1130 (P@O), 1085,
1066, 908, 726, 694, 548 cmꢂ1. – 1H NMR (DMSO-d6): d ꢃ 7.27–
7.49 (m, 29H, Ph, Ph2, Dipy), 7.88 (m, 14H, Ph2, Dipy), 8.21 (d,
6H, Ph), 8.41 (d, 2H, Dipy), 8.64 (d, 2H, Dipy). Anal. Calc. for
C67H53N5O6P3Nd (Mr = 1258.23): C, 63.96; H, 4.25; N, 5.57%.
Found: C, 63.90; H, 4.26; N, 5.53%. .M. p. 140 °C. – IR (KBr):
N-(diphenylphosphoryl)benzamide – HL – was synthesized
according to procedure described previously [10]. Monocrystals
suitable for X-ray investigations were obtained by recrystallization
from mixture of methanol and isopropanol in ratio 1:1.
NaL was obtained from methanol solution by exchange reaction
between NaOMe and HL. NaL: M. p. 255 °C. – UV/Vis (CH3CN): kmax
mmax = 1591, 1508 (C@O), 1438, 1384, 1178, 1131 (P@O), 1086,
1066, 909, 726, 695, 548 cmꢂ1. Anal. Calc. for C67H53N5O6P3Eu
(Mr = 1269.24): C, 63.40; H, 4.21; N, 5.52%. Found: C, 63.44; H,
(lg
emax) = 230 nm (4.37). – IR (KBr): mmax = 1590, 1518 (C@O),
1436, 1382, 1175, 1142 (P@O), 1122, 1100, 902, 834, 722, 698,
550, 531 cmꢂ1. – 1H NMR (DMSO-d6): d = 7.30 (m, 9H, Ph, Ph2),
7.93 (m, 4H, Ph2), 8.24 (d, 2H, Ph). – 31P NMR (DMSO-d6):
4.12; N, 5.50%. .M. p. 130 °C. – IR (KBr): mmax = 1591, 1509 (C@O),
1437, 1384, 1178, 1133 (P@O), 1088, 1066, 909, 726, 694,
548 cmꢂ1. Anal. Calc. for C67H53N5O6P3Gd (Mr = 1174.34): C,

N.S. Kariaka et al. / Journal of Molecular Structure 1068 (2014) 71–76
73
63.15; H, 4.19; N, 5.50%. Found: C, 63.12; H, 4.14; N, 5.47%. .M. p.
pseudo-torsion angle is ꢂ57.8(3)° and 56.5(3)° for molecules A
and B, respectively). Thus, conformation of ligand is pre-organized
for bidentate chelate type of coordination to metal ions.
The amide group is slightly non-planar. The O(1)AC(1)AN(1)
AP(1) torsion angle is ꢂ11.3(4)° in molecule A and 6.3(4)° in B.
The carbonyl bond is not co-planar to phenyl ring (the
130 °C. – IR (KBr):
mmax = 1592, 1511 (C@O), 1437, 1385, 1178,
1130 (P@O), 1088, 1067, 910, 724, 696, 546 cmꢂ1. Anal. Calc. for
C60H53N3O6P3Tb (Mr = 1175.25): C, 63.10; H, 4.19; N, 5.49%.
Found: C, 63.14; H, 4.22; N, 5.44%. .M. p. 135 °C. – IR (KBr):
m
max = 1591, 1511 (C@O), 1438, 1384, 1179, 1132 (P@O), 1089,
1066, 911, 726, 695, 548 cmꢂ1
.
O(1)AC(1)AC(2)AC(3) torsion angle is ꢂ10.8(5)° in
A and
16.4(5)° in B).
The geometry around the phosphorus atoms in both molecules
can be described as slightly distorted tetrahedron. The PAO and
PAN bond lengths have values (Table 1) typical for such the type
compounds [12,13]. The phenyl rings at the phosphorous atom
have different orientations relatively to the P@O bond. The
Preparation of LnL3ꢁPhen (Ln = La, Nd, Eu, Gd, Tb)
Complexes were obtained in a similar manner to foregoing ones
except for the use of 1,10-phenanthroline (1 mmol) instead of 1,2-
dipyridyl. (Yield ꢃ90%). Anal. Calc. for C69H53N5O6P3La
(Mr = 1280.02): C, 64.74; H, 4.17; N, 5.47%. Found: C, 64.81; H,
C(8)ꢁꢁꢁC(13)
ring
has
synperiplanar
orientation
(the
4.15; N, 5.43%. M.p. 140 °C. – IR (KBr): mmax = 1590, 1506 (C@O),
C(9)AC(8)AP(1)AO(2) torsion angle is ꢂ68.4(3)° and 46.1(3)° for
A and B respectively) while the C(14)ꢁꢁꢁC(19) ring is almost co-pla-
nar to the P@O bond (the C(15)AC(14)AP(1)AO(2) torsion angle is
ꢂ6.0(3)° for A and 17.8(3)° for B).
1438, 1384, 1178, 1130 (P@O), 1085, 1066, 908, 725, 695,
548 cmꢂ1. – 1H NMR (DMSO-d6): d ꢃ 7.25–7.38 (m, 27H, Ph,
Ph2), 7.69 (m, 2H, Phen), 7.88 (m, 14H, Ph2, Phen), 8.20 (d, 6H,
Ph), 8.40 (d, 2H, Phen), 9.12 (d, 2H, Phen). Anal. Calc. for
C69H53N5O6P3Nd (Mr = 1285.35): C, 64.47; H, 4.16; N, 5.45%.
Found: C, 63.52; H, 4.18; N, 5.43%. M.p. 150 °C. – IR (KBr):
In the crystal phase molecules A and B are bonded by the
NAHꢁꢁꢁO and CAHꢁꢁꢁ
p hydrogen bonds (Table 1). This leads to the
formation of hydrogen bonded chains along [100] crystallographic
direction (Fig. 1b). Neighboring chains are bonded by the
C(5A)AH(5A)ꢁꢁꢁC(11B)0 (x, 0.5ꢂy, 0.5 + z) hydrogen bonds (HꢁꢁꢁC
2.75 Å, CAHꢁꢁꢁC 159°).
m
max = 1590, 1508 (C@O), 1438, 1384, 1178, 1130 (P@O), 1085,
1066, 909, 725, 694, 548 cmꢂ1. Anal. Calc. for C69H53N5O6P3Eu
(Mr = 1293.07): C, 63.09; H, 4.13; N, 5.42%. Found: C, 64.12; H,
4.12; N, 5.39%. M.p. 190 °C. – IR (KBr): mmax = 1590, 1511 (C@O),
1437, 1384, 1179, 1133 (P@O), 1088, 1066, 909, 726, 695,
547 cmꢂ1. Anal. Calc. for C69H53N5O6P3Gd (Mr = 1298.36): C,
63.83; H, 4.11; N, 5.39%. Found: C, 63.84; H, 4.10; N, 5.34%. M. p.
IR and electronic spectroscopy
IR investigations of carbasylamidophosphates and their com-
plexes are suitable for a preliminary analysis of coordinating mode
195 °C. – IR (KBr):
mmax = 1591, 1511 (C@O), 1438, 1384, 1179,
1133 (P@O), 1088, 1066, 910, 726, 694, 547 cmꢂ1. Anal. Calc. for
C69H53N3O6P3Tb (Mr = 1300.24): C, 63.75; H, 4.11; N, 5.39%.
Found: C, 63.74; H, 4.12; N, 5.36%. .M. p. 200 °C. – IR (KBr):
m
max = 1590, 1512 (C@O), 1438, 1384, 1179, 1134 (P@O), 1088,
1067, 911, 726, 695, 548 cmꢂ1
.
All obtained compounds are stable on air, slightly colored
respective to of Ln(III) aqua ion colors. They are soluble in nonpolar
aromatic solvents, acetone, chloroform, DMFA, DMSO, soluble
poorly in isopropanol and water.
X-ray crystallography
X-ray diffraction data were collected on an XCalibur 3 diffrac-
tometer equipped with graphite-monochromated Mo Ka radiation
(k = 0.71073 Å). The structure was solved by direct method and
refined against F2 by full-matrix least-squares method using the
SHELXTL package [11]. All non-hydrogen atoms were refined
within anisotropic approximation. The H atoms were located from
the difference map of electron density and refined by ‘‘riding’’
model with Uiso = 1.2Ueq of carrier non-hydrogen atom.
Crystals of C19H16NO2P (Mr = 321.30) at 294(2) K are
monoclinic, space group P21/c, a = 9.464(2), b = 16.999(3),
c = 21.910(3) Å,
a
= 90.00, b = 91.064(18), = 90.0°, V = 3524.2
c
(11) Å3, Z = 8,
l
(Mo ,
K
a
) = 0.164 mmꢂ1 dcal = 1.211 g/cm3,
F(000) = 1344, 29,957 reflections measured (Hmax = 55.00°), 8034
unique (Rint = 0.0838) and of these 3902 had F > 4 (F) and were
r
considered to be observed. The final R1, wR2 values were 0.0729
and 0.1594 respectively, for 415 parameters.
Results and discussion
Description of crystal structure
According to X-ray diffraction data two HL molecules (A and B)
with slightly different geometrical parameters are located in asym-
metric part of the crystal unit cell (Fig. 1). The carbonyl and the
P@O bond have synclinal orientation (the O(2)AP(1)ꢁꢁꢁC(1)AO(1)
Fig. 1. Structural representation of HL: (a) – atom numbering scheme of molecule
A; and (b) – fragment of the crystal packing along [100] axis. (hydrogen atoms are
omitted for clarity).

74
N.S. Kariaka et al. / Journal of Molecular Structure 1068 (2014) 71–76
Table 1
geometry and coordination number eight for neodymium ions in
Selected bond lengths (Å) in the HL structure.
NdL3Dipy and NdL3Phen, and coordination number seven in case
of NdL3ꢁi-PrOH [15,16]. These conclusions are in agree with 1H
NMR spectroscopy data, obtained for La(III) complexes. The posi-
tions of the bands in absorption spectra (in toluene and acetonitrile
solutions) and in diffuse reflection for all complexes are very sim-
ilar, so analogous geometries of the nearest Nd3+ environment in
solutions and in solid state were suggested.
P(1A)AO(2A)
P(1A)AN(1A)
C(1A)AO(1A)
C(1A)AC(2A)
1.475(2)
1.689(3)
1.232(4)
1.486(5)
1.365(4)
2.02
168°
1.99
165°
P(1B)AO(2B)
P(1B)AN(1B)
C(1B)AO(1B)
C(1B)AC(2B)
1.480(2)
1.682(3)
1.220(4)
1.498(4)
1.376(4)
2.83
158°
2.84
156°
2.77
N(1A)AC(1A)
N(1B)AC(1B)
N(1A)ꢁꢁꢁH(1A)
H(15A)ꢁꢁꢁC(10B)
C(15A)AH(15A)ꢁꢁꢁC(10B)
H(19A)ꢁꢁꢁC(9B)
N(1A)AH(1A)ꢁꢁꢁO(2B)
N(1B)ꢁꢁꢁH(1B)
4
In the I9/2–2P1/2 transition region (425–435 nm) for all com-
N(1B)AH(1B)ꢁꢁꢁO(2A)
C(19A)AH(19A)ꢁꢁꢁC(9B)
H(15B)ꢁꢁꢁC(10A)
C(15B)AH(15B)ꢁꢁꢁC(10A)
plexes single bands are observed with the maxima at 430.3 nm
for NdL3Dipy, NdL3Phen and and at 430.8 nm for NdL3ꢁi-PrOH. This
suggests in average more covalent character of the metal–ligand
bonds for last complex in comparison to the previous two com-
plexes [17].
158°
Table 2
Averaged values of main vibrational frequencies in the IR spectraa of synthesized
compounds (Ln = La, Nd, Eu, Gd, Tb) and their assignments, cmꢂ1
Thermal gravimetric analyses
.
Considering complexes’ possible applications, thermal stability
of luminescent complexes was examined. TG analysis was
performed for europium and terbium complexes LnL3ꢁi-PrOH,
LnL3Dipy and LnL3Phen (where Ln = Eu, Tb). The first weight loss
5.3% and 5.1% for EuL3ꢁi-PrOH and TbL3ꢁi-PrOH respectively is
observed at 100 °C and is attributed to 2-propanol molecule
removal. Increasing of this value in respect to boiling point of
i-PrOH confirms the solvent coordination to europium ion. Further
decomposition of these complexes starts at 290 °C for europium
and at 230 °C for terbium complex and occurs in two stages.
For europium complex the first stage lays in temperature
range 280–360 °C, the second one is in 530–600 °C temperature
range. For terbium complex the first stage lays in temperature range
230–350 °C, the second one is in 520–600 °C temperature range. For
both europium and terbium complexes the first stage is accompanied
with weight loss 28% and the second one – with weight loss 36%.
In case of LnL3Dipy (Ln = Eu, Tb) complexes, there are no effects
on TG curve till 280 and 260 °C respectively. The temperature
regions and weight loss percentages on the first stages of decom-
position (with indication of corresponding weight loss in brackets)
are equal to 280–360 °C (34%) for EuL3Dipy and 260–320 °C (30%)
for TbL3Dipy respectively, and on the second stages – 550–630 °C
(31%) and 490–690 °C (33%) respectively.
HL
NaL
LnL3iPrOH
LnL3Phen
LnL3Dipy
Assignment
3064
1670
1199
1456
875
–
–
–
–
m
m
m
(NH)
(CO)
(PO)
1518
1143
1382
902
1508
1128
1384
911
1508
1130
1384
909
1510
1131
1384
909
Amide II
(PN)
m
a
Positions of the strongest absorption bands are given in section ‘Synthesis’.
of the ligands [14]. It was demonstrated that in the neutral form,
the CAPh ligands coordinate to the metal ions mostly in a mono-
dentate manner via the oxygen atom of P@O group, whereas in
the deprotonated form they coordinate in a bidentate maner via
the oxygen atoms of the phosphoryl and carbonyl groups, with
the formation of six-membered chelate cycles, which can be
inferred from the values of the valence vibrations
(C@O).
Table 2 lists the averaged values of positions of main absorption
bands in IR spectra of synthesized compounds. For all complexes
low-frequency shift of (PO) and (CO) with respect to spectrum
of NaL is observed:
(PO) = 12–15 cmꢂ1 (CO) = 8–10 cmꢂ1
m(P@O) and
m
m
m
D
m
,
D
m
.
That is because of PO and CO bond multiplicity reduction condi-
tioned by chelate cycle formation due to the ligand bidentate coor-
Decomposition of LnL3Phen (Ln = Eu, Tb) complexes occurs in a
similar manner to foregoing ones. There are no effects on TG curve
till 260 and 250 °C for EuL3Phen and TbL3Phen respectively. The
temperature regions and weight loss percentages on the first
stages of decomposition (with indication of corresponding weight
loss in brackets) are equal to 260–310 °C (25%) for EuL3Phen and
250–400 °C (34%) for TbL3Phen respectively, and on the second
stages – 530–610 °C (43%) and 450–670 °C (33%) respectively.
dination. The absence of valence vibrations
m(NAH) in region
3064 cmꢂ1 confirms ligand deprotonated form in the complexes.
For neodymium complexes the diffuse reflection spectra (DFS)
in the regions of hypersensitive transitions I9/2–4G5/2
,
2G7/2 (a)
4
and in the region of I9/2–2P1/2 (b) were studied (see Fig. 2).
Analysis of the form of hypersensitive transitions and the inten-
sity ratios of the bands in DFS allow to conclude about analogous
4
Fig. 2. Diffuse reflection spectra of synthesized neodymium coordination compounds: 1 – NdL3ꢁi-PrOH, 2 – NdL3Dipy, 3 – NdL3Phen.

N.S. Kariaka et al. / Journal of Molecular Structure 1068 (2014) 71–76
75
Table 3
The spectroscopic characteristic of synthesized lanthanide complexes.
Compound
s
ms
,
D
E(ET
?
5D0), 5D4),
Compound
s
,
D
E(ET
?
cmꢂ1
ms
cmꢂ1
EuL3ꢁiPrOH 0.86 8810
TbL3ꢁiPrOH 1.11 5610
EuL3Dipy
EuL3Phen
1.24 5583
1.55 4252
TbL3Dipy
TbL3Phen
1.44 2383
1.37 1052
tion spectra: kexc = 275 nm for EuL3ꢁiPrOH, kexc = 320 nm for
EuL3Dipy and kexc = 345 nm for EuL3Phen. An intensive emission
of these compounds points to an effective energy transfer from
the ligands to the emitting lanthanide levels. The 5D0 emission
spectra of europium complexes consist of five 5D0 ? 7Fj transitions
(j = 0–4). Also two transitions from 5D1 level are registered.
The high intensity of 5D0 ? 7F2 transitions compared to the
allowed magnetic 5D0–7F1 transition suggests relatively low sym-
metry of Eu(III) surroundings in complexes.
The singlet in the region of 5D0–7F0 transition (Fig. 3a) testifies
the presence of one luminescent center in each of the complexes
under study.
The terbium complexes emission spectra (kexc = 276 nm for
TbL3ꢁiPrOH, kexc = 320 nm for TbL3Dipy and kexc = 330 nm for
TbL3Phen) are presented on Fig. 4. All complexes show strong
green emission. In the luminescence spectra recorded at 298 K only
four f–f transitions (5D4–7Fj, j = 6–3) from seven possible are clearly
observed.
The lowest ligand triplet states for the complexes GdL3ꢁi-PrOH,
LaL3Dipy and LaL3Phen (ET ꢄ 26,110 cmꢂ1
,
22,883 cmꢂ1 and
21,552 cmꢂ1 respectively) were localized based on the phospho-
rescence spectra at 77 K.
Table 3 lists luminescence lifetimes, energy gaps between
ligand triplet states and lanthanide emissive levels (
pium and terbium complexes under study.
DE) for euro-
Fig. 3. Normalized luminescence spectra of synthesized europium complexes:
EuL3ꢁiPrOH (1), EuL3Dipy (2), EuL3Phen (3). (a) The 5D1 emission spectra at 77 K; and
(b) the 5D0 emission spectra at 77 K.
Comparing the energies of the lowest ligand triplet state for the
complexes with lanthanide emissive levels one can evaluate the
possibility of back (from lanthanide ion to ligand) energy transfer.
As the named energy gaps values in all studied europium com-
plexes and in two terbium complexes exceed the limit level
1850 cmꢂ1 established by M. Latva and coworkers [18] we can
exclude any back energy transfer from lanthanide to ligands in
these complexes and expect effective energy transfer for them.
For TbL3Phen the
DE value is under limit level that presages
5D4 ? ET energy transfer as possible process and, as a result, low
quantum yield is expected.
Conclusions
X-ray diffraction investigation of the HL compound have shown
that N-(diphenylphosphoryl)benzamide molecules in the crystal
´
state are linked by the NAHꢁꢁꢁO and CAHꢁꢁꢁ
p hydrogen bonds form-
ing infinite chains along [100] crystallographic axis. Neighboring
chains are connected by CAHꢁꢁꢁ
p
interactions.
The coordination compounds of general formula LnL3ꢁiPrOH,
LnL3Dipy, LnL3Phen (Ln = La, Nd, Eu, Gd, Tb, Dipy = 2,20 – dipyridyl,
Phen = 1,10-phenanthroline) have been synthesized and studied by
TG analysis, IR, NMR 1H, UV–Vis absorption and luminescence
spectroscopy.
Fig. 4. Normalized luminescence spectra of synthesized terbium complexes at
298 K.
High intensity f–f-luminescence at 298 K and 77 K was found
for europium and terbium complexes. The luminescence decay
curves obtained at 298 K are monoexponential and show rather
high luminescence decay time values of studied complexes
(0.86–1.55 ms for europium complexes and 1.11–1.44 ms for ter-
bium ones).
The IR spectra of thermal decomposition products are similar to
the lanthanide polyphosphate spectra.
Photoluminescence studies
Fig. 3 presents europium complexes’ luminescence spectra
recorded upon ligand excitation at maxima of luminescence excita-
The highest luminescence decay times values were registered
for EuL3Phen and TbL3Dipy complexes with the smallest ‘ligand

76
N.S. Kariaka et al. / Journal of Molecular Structure 1068 (2014) 71–76
[3] H. Tsukube, S. Shinoda, H. Tamiaki, Chem. Rev. 102 (2002) 227–234.
[4] G. Mathis, Clin. Chem. 41 (9) (1995) 1391–1397.
[5] Koen. Binnemans, Chem. Rev. 109 (2009) 4283–4374.
[6] K.E. Gubina, V.M. Amirkhanov, Z. Naturforsch 55b (2000) 1015–1019.
[7] G. Oczko, J. Legendziewicz, V. Trush, V. Amirkhanov, New J. Chem. 27 (2003)
948–956.
triplet level – lanthanide emissive level’ energy gaps thus exceed-
ing 1850 cmꢂ1
.
Supplementary material
[8] J. Legendziewicz, G. Oczko, R. Wiglusz, V. Amirkhanov, J. Alloys Compd. 323–
324 (2001) 792–799.
[9] K.O. Znovjyak, V.A. Ovchynnikov, T.Yu. Sliva, S.V. Shishkina, V.M. Amirkhanov,
Acta Cryst. E66 (2010) 306.
[10] R. Garcia-Bueno, M.D. Santana, G. Sanchez, J. Garcia, G. Garcia, J. Perez, L.
Garcia, J. Organomet. Chem. 694 (2009) 316–322.
[11] G.M. Sheldrick, Acta Cryst. A64 (2008) 112.
[12] H.L. Milton, M.V. Wheatley, A.M.Z. Slawin, J.D. Woollins, Polyhedron 23 (2004)
2575–2585.
[13] H.L. Milton, M.V. Wheatley, A.M.Z. Slawin, J.D. Woollins, Polyhedron 23 (2004)
3211–3220.
CCDC 964373 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/data_request/cif or from the Cambridge Crys-
tallographic Data Center, 12 Union Road, Cambridge, CB2 1EZ, UK;
fax: +44 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
[14] V.V. Skopenko, V.M. Amirkhanov, T.Yu. Sliva, I.S. Vasilchenko, E.L. Anpilova,
A.D. Garnovskii, Usp. Khim. 73 (2004) 797–813.
[15] K.O. Znovjyak, O.V. Moroz, V.A. Ovchynnikov, T.Yu. Sliva, S.V. Shishkina, V.M.
Amirkhanov, Polyhedron 28 (2009) 3731–3738.
[16] V.A. Ovchynnikov, V.M. Amirkhanov, K.V. Domasevtich, I. Siler, V.V. Skopenko,
Zhurn. Neorgan. Khim. 46 (2001) 615–622.
Authors would like to thank to Dr. S.S. Smola and Dr. N.V.
Rusakova (A.V. Bogatsky Physico-chemical Institute of the National
Academy of Sciences of Ukraine) for fruitful discussion and provid-
ing luminescence investigations.
[17] K.B. Yatsimirsky, N.K. Davydenko, N.A. Kostromina, T.V. Ternovaya,
Teoreticheskaya i Eksperementalnaya Khim. 1 (1965) 100–105.
[18] M. Latva, H. Takalo, V.-M. Mukkala, C. Matachescu, J.C. Rodríguez-Ubis, J.
Kankare, J. Lumin. 75 (1997) 149–169.
References
[1] J. Kido, Y. Okamoto, Chem. Rev. 102 (2002) 2357–2368.
[2] S.V. Eliseeva, J-C.G. Bünzli, Chem. Soc. Rev. 39 (2010) 189–227.