Synthesis and characterization of lanthanide complexes with a pentadentate triazine-based ligand

Article abstract of DOI:10.1016/j.poly.2016.08.035

A series of mononuclear [Ln(L)(H₂O)(NO₃)(solv)]·solv, (Ln?=?Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6–6a), Dy (7); solv?=?DMF, DMSO, H₂O) and L?=?2,4-bis(2-hydroxybenzylidenehydrazino)-6-methoxy-s-triazine complexes were prepared. The lanthanide(III) ions are nine-coordinated in the complexes and are bound to the O atoms of bidentate nitrate, three N and two O atoms of a pentadentate L ligand and one O atom from water and one O atom from dimethylformamide with a spherical capped square antiprism coordination environment in 1–7. The compounds have been characterized by means of elemental analysis, IR spectroscopy, UV–Vis spectroscopy, X-ray diffraction, and thermal analysis. Lanthanide-centered emission of the complexes is overlapped by the ligand emission.

Full text of DOI:10.1016/j.poly.2016.08.035

Accepted Manuscript
Synthesis and characterization of lanthanide complexes with a pentadentate tri-
azine-based ligand
Lubomír Pavelek, Vít Ladányi, Marek Nečas, Zdeněk Moravec, Kamil
Wichterle
PII:
S0277-5387(16)30394-1
DOI:
http://dx.doi.org/10.1016/j.poly.2016.08.035
POLY 12172
Reference:
Polyhedron
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24 August 2016
Please cite this article as: L. Pavelek, V. Ladányi, M. Nečas, Z. Moravec, K. Wichterle, Synthesis and
characterization of lanthanide complexes with a pentadentate triazine-based ligand, Polyhedron (2016), doi: http://
dx.doi.org/10.1016/j.poly.2016.08.035
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Synthesis and characterization of lanthanide complexes with
a pentadentate triazine-based ligand
Lubomír Paveleka,*, Vít Ladányib,c, Marek Nečasb,d, Zdeněk Moravecb, Kamil Wichterlea
a
Department of Chemistry, Faculty of Metallurgy and Materials Engineering, VŠB-Technical
University of Ostrava, 17. listopadu 15, Ostrava-Poruba CZ-70833, Czech Republic
b
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno
CZ-61137, Czech Republic
c
RECETOX, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno CZ-62500,
Czech Republic
d
CEITEC – Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00
Brno-Bohunice CZ-62500, Czech Republic
* Corresponding author. Tel.: +420 704735413; E-mail address: lubomir.pavelek@vsb.cz
Abstract: A series of mononuclear [Ln(L)(H2O)(NO3)(solv)]·solv, (Ln = Pr (1), Nd (2), Sm (3),
Eu (4), Gd (5), Tb (6-6a), Dy (7); solv = DMF, DMSO, H2O) and L = 2,4-Bis(2-
hydroxybenzylidenehydrazino)-6-methoxy-s-triazine
complexes
were
prepared.
The
lanthanide(III) ions are nine-coordinated in the complexes and are bound to the O atoms of
bidentate nitrate, three N and two O atoms of a pentadentate L ligand and one O atom from water
and one O atom from dimethylformamide with a spherical capped square antiprism coordination
environment in 1-7. The compounds have been characterized by means of elemental analysis, IR
spectroscopy, UV-vis spectroscopy, X-ray diffraction, and thermal analysis. Lanthanide-centered
emission of the complexes is overlapped by the ligand emission.
Keywords: Lanthanide complexes, Triazine ligands, X-ray structure, Optical properties
1. Introduction
The research on lanthanide(III) complexes have attracted attention in recent years due to their
well-defined spectroscopic and magnetic properties [1-5]. The rare earth RE3+ ions are potential
local luminescent probes for diagnostic application in biological systems [6-8]. RE3+ based
compounds are highly promising building blocks for preparation of a single-molecule and single-
chain magnets [9, 10]. Many other potential applications in areas as diverse as catalysis, optics,
magnetic resonance imaging (MRI) have been reported [11-13].
Chlorinated derivative of s-1,3,5-triazine called cyanuric chloride (C3N3Cl3) and its derivatives
are currently intensively studied heterocyclic compounds with interesting biological qualities for
pharmaceutical industry, mainly antifungal, antibacterial, antimalaric and antineoplastic [14-16].
By simple substitution of chlorine atoms in cyanuric chloride, using controlled conditions

2
(temperature) and different nucleophiles, various 2,4,6-mono, di- and trisubstituted, symmetrical
and non-symmetrical derivatives bearing different substituents can be prepared [17]. Cyanuric
chloride has temperature-dependent differential reactivity for displacement of chlorides with
nucleophiles during SNAr as shown in reaction Scheme 1 [18].
Please insert Scheme 1 here
Cyanuric chloride reacts efficiently with hydrazine hydrate to give mono-, di- or tri- substituted
hydrazo- derivatives [19]. Several hydrazo-s-triazine derivatives have already been prepared and
thoroughly studied [20, 21]. s-Triazine derivatives are of considerable current interest in
coordination chemistry and supramolecular chemistry [22]. 2,4,6-trisubstituted-triazine derivatives
proved their great potential in the field of material chemistry, both for their π-interaction abilities
and for their aptitude to be involved in intricate H-bond networks [23].
Lanthanides in their trivalent state form complexes with strongly chelating ligands containing
highly electronegative donor atoms [24, 25]. The ligands may have potential qualities to be
applied in solvent extraction procedures of lanthanides and actinides as presented in several
published papers, where similar triazine-based ligands were used [26-30]. These developments
have inspired us to pursue the study which involves the systematic variation of different
substituents on 2,4,6-trisubstituted-1,3,5-triazine. By condensation of aromatic aldehydes with 2,4-
bis(hydrazino)-6-(S)-1,3,5-triazine, we already prepared a new, highly versatile group of
pentadentate chelating agents which we have used to obtain uranyl(VI) complexes [31]. This work
represents a continuation of the study with a focus on RE3+ lanthanide ions. Finally, we have
synthesized a L ligand exhibiting high affinity to RE3+ ions.
Here we report the synthesis, structural characterizations and optical properties of eight
lanthanide(III)
coordination
compounds
(2),
[Pr(L)(H2O)(NO3)(DMF)]·DMF
[Sm(L)(H2O)(NO3)(DMF)]·DMF
[Gd(L)(H2O)(NO3)(DMF)]·DMF
[Tb(L)(H2O)(NO3)(DMSO)]·2H2O
(1),
(3),
[Nd(L)(H2O)(NO3)(DMF)]·DMF
[Eu(L)(H2O)(NO3)(DMF)]·DMF
[Tb(L)(H2O)(NO3)(DMF)]·DMF
(4),
(5),
(6),
(6a),
[Dy(L)(H2O)(NO3)(DMF)]·DMF (7) (L = C18H17N7O3).
2. Experimental
2.1. Reagents and techniques
Dy(NO3)3·H2O, Pr(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·5H2O, Gd(NO3)3·6H2O,
Tb(NO3)3·6H2O, Nd(NO3)3·6H2O (Sigma-Aldrich), N,N-Dimethylformamide (Sigma-Aldrich,
98%), cyanuric chloride (Aldrich, 99%), hydrazine hydrate (Sigma-Aldrich, 50-60%), sodium
bicarbonate (Sigma-Aldrich), methanol (Sigma-Aldrich, anhydrous, 99.8%), tetrahydrofuran
(Sigma-Aldrich, anhydrous, 99.9%) and dimethyl sulfoxide (Sigma-Aldrich, anhydrous, 99.9%)
were commercially available and were used without further purification.

3
FT-IR spectra were recorded using ATR technique by ALPHA FT-IR spectrometer (Bruker) in
the 4000 – 400 cm-1 region. The reported FT-IR signal intensities were defined as w = weak, m =
medium and s = strong.
UV-vis absorption spectra of ligands and complexes were recorded using a Shimadzu UV-1602
spectrophotometer or GBC Scientific Equipment Cintra 2020 spectrophotometer in 1-cm quartz
cuvette. The fluorescence emission spectra were performed on a FLS 920 fluorescence
spectrometer (Edinburgh instruments) equipped with a 450 W Xe lamp and PMT detector with a
double grating monochromator for both the excitation and the emission. Florescence spectra of the
ligand and complexes were recorded upon excitation wavelength around their absorption
maximum; spectra were collected from three repetitions. The measurements were performed in 1-
cm fluorescence cuvettes in front face-geometry arrangement [31]. Elemental analysis (C, H and
N) were performed using Elementar Vario EL III.
Diffraction data were collected on a Rigaku MicroMax-007 HF rotating anode CCD
diffractometer using Mo Kα radiation at 120 K. The structures were solved by direct methods and
refined using the full-matrix least-squares method on F2 with anisotropic thermal parameters for
all non-hydrogen atoms (ShelXTL) [32]. A summary of the crystallographic data and structure
refinement parameters is given in Table 4. The molecular graphics as well as additional structural
calculations
were
drawn
and
interpreted
using
Diamond,
ver.
3.2
(http://www.crystalimpact.com/diamond/Default.htm).
Thermal analysis (TG/DSC) was recorded on a Netzsch STA 449C Jupiter apparatus from 30 to
1000 °C under flowing synthetic air (70 cm3.min-1) with a heating rate of 5 K min-1. Powder
diffraction patterns were collected with the PANalytical X'Pert PRO diffractometer equipped with
conventional X-ray tube (Cu Kα radiation, 40 kV, 30 mA) and a linear position sensitive detector
PIXcel with an anti-scatter shield. Qualitative analysis was performed with HighScorePlus
software package (PANalytical, The Netherlands, version 4.1.0), and Match3
(http://www.crystalimpact.com/match/Default.htm).
2.2. Synthesis of ligand L
The synthetic pathways to obtain intermediate and final compounds are shown in Scheme 2.
Stage 1: Cyanuric chloride (13.0 g, 70 mmol) was added into a solution of sodium bicarbonate
(6.5 g, 77 mmol) in methanol (100 ml) at 10 ºC and the resulting suspension was stirred for 1 h at
room temperature. Solid white product was removed by filtration. Dry product was recrystallized
from hot hexane to give 2,4-dichloro-6-methoxy-s-triazine (DCMT) in 85% isolated yield.
Stage 2: DCMT (10.05 g, 55.56 mmol) was suspended in tetrahydrofuran (200 ml) and stirred
vigorously for 10 min. One portion of hydrazine hydrate (11.5 g, 0.227 mol) was added at room
temperature and stirred for 1 h. After that, the mixture was refluxed for additional 12 h. The
solution was cooled at room temperature. Cold distilled water was added into the solution and the

4
precipitated product was collected by filtration and dried to obtain pure DHMT (2,4-
Bishydrazino-6-methoxy-s-triazine) powder in 70% isolated yield.
Stage 3: A reaction sequence according to Scheme 2 for L: DHMT (1.37 g, 8 mmol) was
dissolved in 200 mL of anhydrous tetrahydrofuran and salicylaldehyde was added in one step (L)
(1.95 mL, 16 mmol). The solution was heated under reflux overnight. After cooling the solution to
room temperature, the crude product was obtained as a white powder.
For L (white powder): Yield: 31%. Anal. Calc. for C18H17N7O3 (379.37): C, 56.99; H, 4.52; N,
25.84%. Found: C, 56.78; H, 4.61; N, 25.69%. IR (ATR, ν/cm-1): ν = 3568 (w); 2915 (w); 1618
(s); 1574 (s); 1516 (s); 1479 (s); 1366 (s); 1268 (m); 1156 (m); 951 (w); 799 (m); 742 (s).
Please insert Scheme 2 here
2.2. Synthesis of complexes 1-7
[Pr(L)(H2O)(NO3)(DMF)]·DMF (1). A suspension of L (379.4 mg; 1 mmol) in DMF (30 mL)
was heated for 10 min. Then, solid Pr(NO3)3·6H2O (434 mg; 1 mmol) was slowly added to the
mixture under continuous heating and stirring to give a yellow solution. After 10 min of heating,
Et3N (1.51 mL; 1.5 mmol) was added dropwise and the mixture was heated for further 15 min.
The resulting solution was stirred for 1 h and subsequently filtered. The yellow filtrate was left to
evaporate slowly over three weeks, giving brown-yellow crystals suitable for X-ray diffraction
analysis. The needle crystals were collected by filtration, washed with methanol and diethyl ether,
and dried in air. Yield: 53%. Anal. Calc. C24H31N10O9Pr (744.50): C, 38.55; H, 4.18; N, 18.73%.
Found: C, 37.95; H, 3.58; N, 18.44%. IR (ATR, ν/cm-1): ν = 3216 (w); 2925 (w); 1647 (m); 1603
(m); 1540 (s); 1466 (s); 1382 (m); 1379 (m); 1293 (m); 1198 (m); 1144 (w); 804 (m); 735 (m).
The syntheses of complexes 2-7 followed the procedure described for complex 1.
[Nd(L)(H2O)(NO3)(DMF)]·DMF (2). Brown-yellow crystals. Yield: 47%. Anal. Calc.
C24H31N10O9Nd (747.83): C, 38.72; H, 4.20; N, 18.81%. Found: C, 38.34; H, 3.78; N, 18.59%. IR
(ATR, ν/cm-1): ν = 3404 (w); 2927 (w); 1646 (s); 1540 (s); 1463 (s); 1382 (m); 1308 (m); 1197
(m); 1142 (m); 804 (m); 735 (m); 655 (w).
[Sm(L)(H2O)(NO3)(DMF)]·DMF (3). Brown-yellow crystals. Yield: 52%. Anal. Calc.
C24H31N10O9Sm (753.94): C, 38.23; H, 4.14; N, 18.58%. Found: C, 37.44; H, 3.72; N, 18.17%. IR
(ATR, ν/cm-1): ν = 3447 (w); 2929 (w); 1650 (s); 1540 (m); 1467 (m); 1385 (m); 1100 (w); 804
(w); 736 (w); 657 (w).
[Eu(L)(H2O)(NO3)(DMF)]·DMF (4). Brown-yellow crystals. Yield: 48%. Anal. Calc.
C24H31N10O9Eu (755.55): C, 38.15; H, 4.14; N, 18.54%. Found: C, 37.88; H, 3.78; N, 18.24%. IR
(ATR, ν/cm-1): ν = 3419 (w); 2928 (w); 1649 (s); 1540 (m); 1468 (m); 1384 (m); 1090 (w); 804
(w); 736 (w); 655 (w).

5
[Gd(L)(H2O)(NO3)(DMF)]·DMF (5). Brown-yellow crystals. Yield: 58%. Anal. Calc.
C24H31N10O9Gd (760.84): C, 37.89; H, 4.11; N, 18.41%. Found: C, 36.88; H, 3.81; N, 18.22%. IR
(ATR, ν/cm-1): ν = 3420 (w); 2930 (w); 1649 (s); 1541 (m); 1468 (m); 1385 (m); 1102 (w); 804
(w); 735 (w); 656 (w).
[Tb(L)(H2O)(NO3)(DMF)]·DMF (6). Brown-yellow crystals. Yield: 60%. Anal. Calc.
C24H31N10O9Tb (762.51): C, 37.80; H, 4.10; N, 18.37%. Found: C, 37.40; H, 3.78; N, 18.17%. IR
(ATR, ν/cm-1): ν = 3412 (w); 3221 (w); 2929 (w); 1649 (s); 1541 (m); 1469 (m); 1385 (m); 1104
(w); 805 (w); 736 (w); 656 (w).
[Dy(L)(H2O)(NO3)(DMF)]·DMF (7). Brown-yellow crystals. Yield: 55%. Anal. Calc.
C24H31N10O9Dy (766.09): C, 37.63; H, 4.08; N, 18.28%. Found: C, 37.68; H, 3.95; N, 18.13%. IR
(ATR, ν/cm-1): ν = 3416 (w); 3215 (w); 2929 (w); 1650 (s); 1543 (m); 1513 (m); 1373 (m); 1306
(w); 1198 (m); 953 (w); 742 (m); 665 (m).
[Tb(L)(H2O)(NO3)(DMSO)]·2H2O (6a). A suspension of L (379.4 mg; 1 mmol) in MeOH
(30 mL) was heated for 10 min. Then, solid Tb(NO3)3·6H2O (453 mg; 1 mmol) was slowly added
to the mixture under continuous heating and stirring to give a yellow solution. After 10 min of
heating, Et3N (1.51 mL; 1.5 mmol) was added dropwise and the mixture was heated for further 15
min. After being cooled to room temperature, yellow powder was collected through suction
filtration and washed with methanol. The light-brown needle crystals suitable for X-ray diffraction
studies were obtained by recrystallization of a yellow powder from DMSO for over two months at
room temperature.Yield: 60%. Elemental Anal. Calc. C20H27N8O10STb (730.48): C, 32.89; H,
3.73; N, 15.34; S, 4.39%. Found: C, 32.68; H, 3.55; N, 15.13; S, 4.30%. IR (ATR, ν/cm-1): ν =
3408 (w); 3227 (w); 2918 (w); 1604 (m); 1535 (s); 1469 (s); 1439 (s); 1377 (s); 1305 (m); 1199
(m); 1152 (w); 996 (w); 802 (w); 752 (m).
3. Results and discussion
3.1. IR spectra
The infrared spectra of the all complexes 1-7 were recorded in the region 4000-400 cm-1 (Fig.
S1 in ESI). A broad band in the region 3500-3300 cm-1 indicates the presence of water (OH)
molecule coordinated to the lanthanide atom [33]. The characteristic C=N stretching of triazine
ring in L appears as a medium intensity signal in the region 1550-1480 cm-1 [34]. The IR strong
stretching frequency of the C=N is found at 1650-1604 in all the complexes. The positive shift of
the ν(C=N) band, which is observed at 1618 cm-1 in the free ligand, is related to the coordination
of the nitrogen atom of the hydrazine chain group [35]. Weak absorption bands in the region 3200-
2900 cm-1 are typical of NH stretching vibrations in hydrazine side chain and a series of
absorption bands in the range 1385-1280 cm-1 are typical of the coordinated nitrate group ν(N=O)

6
and νas(NO2) [36]. The νs(NO2) is detected at 1035 cm-1 [37]. After coordination, the various
vibrations of Ln-O are assigned to bands occurring at 580-520 cm-1 and Ln-N are assigned to
weak bands occurring at 480-410 cm-1, respectively, which confirms the involvement of the
oxygen and nitrogen atoms in the coordination sphere of Ln(III) [38]. The series of a weak
absorption bands in the range 1270-1150 cm-1 is typical of the C-O-C bonds [39].
Please insert Table 1 here
3.2. Electronic absorption spectra
Solutions of the ligand and complexes for UV-vis absorption and fluorescence measurements
were prepared in DMF. The calculations of molar absorption coefficients of the ligand and
complexes are summarized in Table 2. Absorption spectrum of the ligand L is characterized by
two strong absorption bands with major maxima at 302 nm and 342 nm (Fig. S2 in ESI).
Absorption spectra of all the prepared lanthanide complexes are characteristic by disappearance of
the second major band observed in the spectrum of the ligand in the 315–360 nm region. A new
strong absorption band appears in the 330–450 nm region with major maximum around 372 nm
for all the presented complexes. We assume the new absorption band belongs to considerably
hyperchromically shifted n→π band of the ligand (λmax = 375 nm). A similar phenomenon we
observed in our previous study dealing with uranium complexes, where the aforementioned
absorption band was hyperchromically and slightly hypsochromically shifted [31].
Please insert Figure 1 here
Recorded fluorescence emission spectra of the ligand L and the complexes have one broad
relatively uniformly shaped band with one maximum. The emission maximum of the ligand L and
complexes 1, 3, 4, 6, 6a and 7 is located in the 422–430 nm region, emission maximum of
complex 2 (451 nm) and 5 (460 nm) is bathochromically shifted. All-important luminescence data
are summarized in Table 3, emission spectra are presented in Figs. S3-S5 in ESI. Lanthanide-
centered emission of the prepared complexes is overlapped by the strong emission signal of the
ligand.
Please insert Table 2 here
Please insert Table 3 here
3.3. X-ray structure of complexes

7
In all the present compounds, lanthanide ions are nine-coordinate. The coordination polyhedron
is completed with three nitrogen and two oxygen atoms of the organic chelating ligand, two
oxygen atoms of a bidentate nitrate ligand, and two oxygen atoms from water and either DMF (1
to 7) or DMSO (6a) ligands (Fig. 2, 3). The organic ligand inherently forms an equatorial plane
which divides the coordination polyhedron in two halves (Fig. 4). While the first is occupied by
both the nitrate ligand and the DMF/DMSO, the second one contains a single water ligand.
Because of a steric crowd from the former, the equatorial plane of the organic ligand is shifted
towards the water ligand. The r.m.s. deviations for the least-squares planes calculated for the five
donor atoms of the organic ligand in 1 to 7 range from 0.0667 to 0.0723 Å, and the respective
lanthanide ions deviations progressively decrease from 0.5633(9) to 0.5158(8) Å with decreasing
ionic radii. The deviation of Tb in 6a (0.5204(8) Å) is in accordance with this trend, although the
respective least-squares plane through the donor atoms shows significantly higher r.m.s. deviation
of 0.1898 Å.
Selected bond lengths and angles are listed in Table 5. With decreasing lanthanide radii, the
Ln–O and Ln–N bond lengths get progressively shorter in 1 (Pr) to 5 (Gd) and 7 (Dy), which is
further reflected in the ligand bite angles. As the smaller lanthanide ions get deeper into the
chelate rings, the constituent bite angles get wider while the O2–Ln–O3 angles get narrower.
The water ligands mediate the formation of centrosymmetric dimers via two pairs of O—H···O
hydrogen bonds to oxygen acceptors from the organic ligands in the other complex molecule (Fig.
5). Another centrosymmetric pairs of N—H···O bonds to oxygen acceptors from the nitrate
ligands are responsible for the formation of one-dimensional supramolecular architecture along the
b axis. In the isostructural compounds 1 to 6 and 7, donor-acceptor distances are very similar,
being on average 2.78 Å for the first of the two O—H···O bonds, 2.67 Å for the second, and
2.87 Å for the N—H···O bond. The related donor-acceptor distances in 6a are 2.958(2), 2.610(2)
and 2.982(2) Å, respectively. A second N–H group from the organic ligand is bound to a solvating
DMF molecule in the crystalline complexes 1 to 7. In 6a, two water molecules per formula unit
are present, which form a rhomboidal structural unit via hydrogen bonds with their
centrosymmetry-related counterparts. These rhomboidal units connect the above-mentioned
supramolecular chains through pairs of N—H···O and O—H···N bonds with donor-acceptor
distances of 2.816(3) and 2.924(3) Å, respectively. For complexes 1-7, the coordination geometry
around the metals were analyzed using by program Shape 2.1 [40]. Any coordination sphere can
be described by an ideal polyhedron that has the lowest deviation from the real geometry. The
lowest value of deviation for 1-7 was found for spherical capped square antiprism (C4v) (complete
results of the geometric analyses are given in Table 6).
Please insert Figure 2 here
Please insert Figure 3 here
Please insert Figure 4 here

8
Please insert Figure 5 here
Please insert Table 4 and Table 4 (cont.) here
Please insert Table 5 here
Please insert Table 6 here
3.4. Thermal analyses
TG/DSC experiments show that the complexes 6 and 6a follow similar decomposition
pathways regardless of different solvents present in their structures. The weight losses during
heating from 30 to 150 °C correspond to the evaporation of DMF and water for 6 or DMSO and
water for 6a. Degradation of the organic part of the complexes was observed from 300 to 500 °C,
and consists of two separated exothermic steps. The total mass losses of 74.9 and 73.9 % for 6 and
6a (calculated values 75.6 and 74.5, respectively) correspond to the formation of Tb7O12, which
has been confirmed by X-ray powder patterns of final residues left after the TG/DSC experiments
(Figs. S6-S7 in ESI).
4. Conclusions
In summary, we have prepared a large, nearly planar s-triazine Schiff base ligand by
condensation of 2,4-bis(hydrazino)-6-methoxy-1,3,5-triazine with salicylaldehyde and presented
its lanthanide complexes, which have been characterized by elemental analysis, IR and UV-vis
spectroscopy, thermal analysis, and X-ray diffraction technique. The lanthanide(III) ions are 9-
coordinated by six O atoms, two of which come from the nitrate anion, two from the triazine
Schiff base ligand, one from water and one from the solvent DMF/DMSO. The ligand behaves as
pentadentate with N3O2 donor set (two imine nitrogen atoms, one triazine nitrogen atom, and two
phenolic group oxygen atoms) and the Ln(III) ions fit the ligand acyclic cavity.
Acknowledgments
This research has been financially supported by the Ministry of Education, Youth and Sports of
the Czech Republic under the projects CEITEC 2020 (LQ1601) and SP2016/77. We acknowledge
the CF X-ray diffraction and Bio-SAXS supported by the CIISB research infrastructure
(LM2015043 funded by MEYS CR) for their support with obtaining scientific data presented in

9
this paper. The authors also thank Michal Babiak (Masaryk University) for helpful comments
concerning X-ray analysis, further Gabriela Ondrušková and Ján Krausko (Masaryk University)
for their help with luminescent measurements. We thank Dr. P. Bezdicka for PXRD analyses.
Appendix A. Supplementary Data
CCDC 1495956-1495963 contain the supplementary crystallographic data for complexes 1-7.
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. Supplementary data associated with
this article can be found, in the online version, at

10
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Figure captions
Scheme 1. Differential reactivity of cyanuric chloride with R-NH2, R1-NH2, R2-NH2 = N
nucleophiles.
Scheme 2. The reaction conditions for preparing L: (a) CH3OH, NaHCO3, 10 ºC, 1 h; (b)
N2H4·H2O, THF, reflux 12 h; (c) 2-Hydroxybenzaldehyde, CH3OH, reflux 24 h.
Fig. 1. The molar absorption coefficients spectra of ligand L, complexes 1–4.
Fig. 2. Molecular structure of 6. Thermal ellipsoids are drawn at the 50% probability level.
Fig. 3. Molecular structure of 6a. Thermal ellipsoids are drawn at the 50% probability level.
Fig. 4. Coordination polyhedron of the europium atom in the complex 4.
Fig. 5. Hydrogen bonding in the crystal structure of 6 and the resulting supramolecular
architecture. Solvent DMF and hydrogen atoms were omitted except for (O)H and (N)H.

14
Scheme 1.

15
Scheme 2.

16
Fig. 1.

17
Table 1 Selected infrared spectral data of ligand L, and complexes 1-7 (ν/cm-1).
Selected Type
Ln-O
Ln-N
νO-H
νNO
(coordinate)
2
Compound
L
Triazine bands
of stretching
(phenolic)
1618 (C=N)
3118 (N-H)
3568
3417
3420
3447
3419
3420
3411
3408
-
-
-
1573 (C=NSchiff
3124 (N-H)
)
)
)
)
)
)
)
)
1
2
1647 (C=N)
1646 (C=N)
1650 (C=N)
1649 (C=N)
1649 (C=N)
1649 (C=N)
1629 (C=N)
1382; 1308
1379; 1294
1385; 1291
1384; 1299
1385; 1301
1385; 1304
1378; 1305
524
519
520
520
520
520
520
483
478
477
477
477
477
477
1540 (C=NSchiff
3116 (N-H)
1540 (C=NSchiff
3119 (N-H)
3
1540 (C=NSchiff
3120 (N-H)
4
1540 (C=NSchiff
3125 (N-H)
5
1541 (C=NSchiff
3125 (N-H)
6
1541 (C=NSchiff
3131(N-H)
6a
1535 (C=NSchiff
1023 (S-O)
7
1650 (C=N)
3125 (N-H)
3421
1384; 1314
520
477
1543 (C=NSchiff
)

18
Table 2 Absorption properties of ligand L and complexes 1–7.
λmax, nm, (ε, mol-1 dm3 cm-1)
293 (33600), 302 (38800), 332 (36500), 342 (37400), 375 (4900),
405 (3500)
L
295.9 (33700), 308.7 (34200), 372.1 (23300)
297.4 (29400), 309.2 (33100), 371.6 (24800)
298.3 (25400), 309.2 (28700), 372.6 (22100)
298.3 (32000), 309.2 (35400), 371.6 (26900)
296.9 (29900), 308.8 (30600), 372.2 (23300)
299.3 (27100), 309.2 (30300), 372.6 (25400)
295.9 (34900), 307.8 (34400), 372.1 (25500)
298.3 (25400), 309.2 (23900), 333.0 (8300), 371.6 (22400)
1
2
3
4
5
6
6a
7
Concentration of Lc = 1.5 · 10-5 M, 1c = 1.9 · 10-5 M, 2c = 2.4 · 10-5 M, 3c = 2.0 · 10-5 M,
4c = 1.8 · 10-5 M, 5c = 1.9 · 10-5 M, 6c = 2.0 · 10-5 M, 6ac = 3.9 · 10-5 M, 7c = 2.0 · 10-5 M.

19
Table 3 Luminescence properties data.
c / mol dm-3
λexc / nm
λem, max / nm
5.5 · 10-4
9.7 · 10-5
1.2 · 10-4
1.0 · 10-4
9.0 · 10-5
7.9 · 10-5
1.5 · 10-4
1.2 · 10-4
9.9 · 10-5
300
295
308
308
320
308
311
295
311
429
423
451
422
426
460
430
422
422
L
1
2
3
4
5
6
6a
7

20
Fig. 2.

21
Fig. 3.

22
Fig. 4.

23
Fig. 5.

Table 4
X-ray structure data collection and refinement parameters for the complexes 1 to 7.
1
2
3
4
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C24H31N10O9Pr
744.50
C24H31N10O9Nd
747.83
C24H31N10O9Sm
753.94
C24H31N10O9Eu
755.55
Triclinic
P-1
Triclinic
P-1
Triclinic
P-1
Triclinic
P-1
10.1082(3)
11.9110(4)
14.0456(4)
107.861(3)
109.148(3)
97.092(3)
1472.55(8)
2
10.0858(2)
11.9513(3)
14.0750(3)
107.901(2)
109.105(2)
97.062(2)
1477.62(6)
2
10.0616(4)
11.8693(4)
13.9526(5)
107.646(3)
108.967(3)
97.021(3)
1455.91(9)
2
10.0649(3)
11.8631(4)
13.9507(4)
107.567(3)
108.937(2)
97.101(3)
1456.04(8)
2
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
Dcalcd. (g·cm-3)
1.679
1.681
1.720
1.723
F(000)
752
754
758
760
µ(mm-1)
1.723
1.825
1.825
2.223
Measured/unique reflections
Data/restraints/parameters
R1/wR2 [I >2σ(I)]
R1/wR2 [all data]
GooF
18464/5379
5379/2/408
0.0243/0.0533
0.0290/0.0551
1.035
14312/5403
5403/2/408
0.0258/0.0762
0.0266/0.0766
1.087
16259/5317
5317/2/408
0.0219/0.0507
0.0236/0.0518
1.076
14708/5322
5322/2/408
0.0272/0.0587
0.0319/0.0609
1.060
∆ρmax /∆ρmin (e. Å-3)
0.843/-0.434
1.993/-0.682
1.139/-0.625
1.545/-0.756

Table 4 (cont.)
5
6
6a
7
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C24H31N10O9Gd
760.84
C24H31N10O9Tb
762.51
C20H27N8O10STb
730.48
C24H31N10O9Dy
766.09
Triclinic
P-1
Triclinic
Triclinic
P-1
Triclinic
P-1
P-1
10.0546(2)
11.8642(2)
13.9444(2)
107.472(2)
108.885(2)
97.099(2)
1455.66(4)
2
10.05090(10)
11.8566(2)
13.9219(2)
107.3600(10)
108.9010(10)
97.0560(10)
1453.18(4)
2
9.9332(2)
11.6533(3)
12.0804(3)
107.199(2)
97.010(2)
98.424(2)
1301.03(5)
2
10.04230(10)
11.84790(10)
13.9106(2)
107.2910(10)
108.9070(10)
97.0400(10)
1450.47(3)
2
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
Dcalcd. (g·cm-3)
1.736
1.743
1.865
1.754
F(000)
762
764
728
766
µ(mm-1)
2.347
2.503
2.869
2.645
Measured/unique reflections
Data/restraints/parameters
R1/wR2 [I >2σ(I)]
R1/wR2 [all data]
GooF
14021/5257
5257/2/408
0.0149/0.0358
0.0154/0.0359
1.077
13968/5285
5285/2/408
0.0158/0.0387
0.0169/0.0418
1.135
16228/4732
4732/6/382
0.0181/0.0446
0.0187/0.0449
1.068
13548/5213
5213/2/408
0.0167/0.0456
0.0172/0.0497
1.180
∆ρmax /∆ρmin (e. Å-3)
0.715/-0.331
0.740/-0.414
1.028/-0.527
0.763/-0.521

Table 5
Selected bond lengths [Å] and angles [°] for 1 to 7.
1
2
3
4
5
6
6a
7
Ln1–O2
Ln1–O3
2.2988(17)
2.3336(17)
2.5212(18)
2.6410(18)
2.6430(17)
2.5073(19)
2.550(2)
2.2937(18)
2.3293(18)
2.5009(19)
2.6270(19)
2.6351(19)
2.489(2)
2.2659(16)
2.3040(16)
2.4596(18)
2.5996(17)
2.6083(17)
2.4621(18)
2.5046(19)
2.632(2)
2.258(2)
2.301(2)
2.445(2)
2.583(2)
2.595(2)
2.454(2)
2.491(3)
2.623(2)
2.616(2)
86.93(8)
69.11(8)
68.67(8)
62.74(8)
62.68(7)
123.81(8)
2.2541(11)
2.2954(11)
2.4257(11)
2.5779(11)
2.5895(11)
2.4372(12)
2.4849(13)
2.6135(14)
2.6082(13)
86.24(4)
2.2378(13)
2.2843(13)
2.4133(14)
2.5697(14)
2.5805(14)
2.4262(14)
2.4709(16)
2.6056(16)
2.5956(16)
85.50(5)
2.2792(15)
2.2158(16)
2.4256(16)
2.5985(17)
2.5349(16)
2.4176(16)
2.4518(18)
2.5689(19)
2.5899(18)
85.07(6)
2.2219(16)
2.2754(16)
2.3982(16)
2.5588(17)
2.5703(16)
2.4115(17)
2.4581(19)
2.5954(19)
2.5857(19)
85.17(6)
Ln1–O4
Ln1–O5
Ln1–O6
Ln1–O8
Ln1–N3
2.534(2)
Ln1–N6
2.678(2)
2.664(2)
Ln1–N7
2.664(2)
2.654(2)
2.6254(19)
87.49(6)
O2–Ln1–O3
O2–Ln1–N6
O3–Ln1–N7
N3–Ln1–N6
N3–Ln1–N7
N6–Ln1–N7
89.55(6)
88.78(6)
68.28(6)
68.41(7)
69.02(6)
69.38(4)
69.60(5)
69.34(6)
69.72(6)
67.90(6)
68.17(7)
68.41(6)
68.73(4)
68.97(5)
70.81(6)
69.00(6)
61.70(6)
62.01(7)
62.50(6)
62.85(4)
63.10(5)
63.62(6)
63.26(6)
61.78(6)
62.04(7)
62.58(6)
62.97(4)
63.23(5)
63.28(6)
63.43(6)
121.85(6)
122.40(7)
123.46(6)
124.16(4)
124.68(5)
124.90(6)
125.01(6)

Table 6
Results of continuous shape measures calculations using program SHAPE 2.1 for complexes 1-7. a
Pr1(III)
Nd2(III)
Sm3(III)
Eu4(III)
Gd5(III)
Tb6(III)
Tb6a(III)
Dy7(III)
CN=9b
CCU-9
JCSAPR-9
CSAPR-9
JTCTPR-9
JCCU-9
7.927
2.508
1.831
4.079
8.912
7.893
2.441
1.763
4.079
8.885
7.954
2.393
1.697
3.991
8.958
7.950
2.362
1.670
3.974
8.952
8.010
2.328
1.632
3.954
9.014
8.080
2.308
1.613
3.960
9.080
6.854
2.080
1.383
3.276
7.905
8.083
2.266
1.575
3.932
9.079
a The listed values correspond to the deviation between the ideal and real coordination polyhedra, the lowest values are in red color.
b CCU-9 = spherical capped cube, JCSAPR-9 = capped square antiprism J10, CSAPR-9 = spherical capped square antiprism, JTCTPR-9 = tricapped
trigonal prism J51, JCCU-9 = capped cube J8.

Graphical abstract
•
•
Eight new lanthanide(III) complexes of a Schiff-base ligands based on s-triazine derivative
have been synthesized.
The
X-ray
crystal
structures
of
[Pr(L)(H2O)(NO3)(DMF)]·DMF
[Sm(L)(H2O)(NO3)(DMF)]·DMF
[Gd(L)(H2O)(NO3)(DMF)]·DMF
[Tb(L)(H2O)(NO3)(DMSO)]·2H2O
(1),
(3),
[Nd(L)(H2O)(NO3)(DMF)]·DMF
[Eu(L)(H2O)(NO3)(DMF)]·DMF
[Tb(L)(H2O)(NO3)(DMF)]·DMF
(2),
(4),
(5),
(6),
(6a),
[Dy(L)(H2O)(NO3)(DMF)]·DMF (7) have been determined.
•
•
The luminescence, FTIR and UV-vis spectra of all complexes 1-7 have been studied.
The TG and +DSC analyses of all complexes 1-7 have been determined.