Cerium(iii) complexes with azolyl-substituted thiophenolate ligands: Synthesis, structure and red luminescence

Article abstract of DOI:10.1039/c9ra03199e

In order to obtain molecular Ce(iii) complexes which emit red light by f-d transitions the azolyl-substituted thiophenolates were used as the ligands. The thiophenolate Ce(iii) complexes were synthesized by the reaction of Ce[N(SiMe₃)₂

Full text of DOI:10.1039/c9ra03199e

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Cerium(III) complexes with azolyl-substituted
thiophenolate ligands: synthesis, structure and red
Cite this: RSC Adv., 2019, 9, 24110
luminescence†
a
c
Liubov I. Silantyeva,a Ivan D. Grishin,b Anton V. Rozhkov,
*
Vasily A. Ilichev,
Roman V. Rumyantcev,
a
ab
Georgy K. Fukina and Mikhail N. Bochkarev
In order to obtain molecular Ce(III) complexes which emit red light by f–d transitions the azolyl-substituted
thiophenolates were used as the ligands. The thiophenolate Ce(III) complexes were synthesized by the
reaction of Ce[N(SiMe3)2]3 with respective thiophenols 2-(20-mercaptophenyl)benzimidazole (H(NSN)), 2-
(20-mercaptophenyl)benzoxazole (H(OSN)) and 2-(20-mercaptophenyl)benzothiazole (H(SSN)) in DME
media. The structures of the benzimidazolate (Ce(NSN)3(DME)) and benzothiazolate (Ce(SSN)3(DME))
derivatives were determined by X-ray analysis which revealed that the cerium ion in the molecules is
coordinated by one DME and three anionic thiophenolate ligands. The lanthanum complex
La(OSN)3(DME) has been synthesized similarly and structurally characterized. It was found that the solids
of Ce(SSN)3(DME) and Ce(OSN)3(DME) exhibit a broad band photoluminescence peaking at 620 nm
which disappears upon solvatation. With an example of OSN derivatives it was proposed that this
behaviour is caused by the blue shift of the f–d transition of Ce3+ ions.
Received 29th April 2019
Accepted 30th July 2019
DOI: 10.1039/c9ra03199e
rsc.li/rsc-advances
A new surge of interest in luminescent trivalent cerium
complexes is directly associated with the discovery of photoredox
catalytic activity of these compounds in some reactions.14–16 The
Introduction
Molecular lanthanide(III) complexes exhibiting bright and
efficient photoluminescence (PL) have been successfully
applied in various modern technologies including lasers and
ber ampliers,1 light emitting diodes and solar cells,2–7
bioassays and medicine.8–11 Among these compounds, the
main attention was focused on the derivatives of lanthanides
that emit in the visible or near infrared region due to the
intracongurational transitions inside the 4f subshell, while
the eld of luminescent complexes that have other emitting
congurations was almost undeveloped. First of all, this
relates to f–d luminescent Ce(III) derivatives. This ion is a key
component of a huge number of inorganic phosphors,12,13 but
the overall number of its luminescent molecular species is very
limited to date.
most active photoredox-catalytic complexes are luminescent deriv-
atives of ruthenium and iridium, which have long-lived triplet
excited states.17–20 In the case of Ce(III) complexes the existence of
relatively long-lived excited states is attributed to 5d states of the
cerium ion. The energies of 5d states, in contradistinction to 4f
states, are extremely sensitive to ligand environment. It is known
that some cerium complexes with silylamide,21 guanidinate, aryl-
oxide,15 alkoxide,22 cyclopentadienyl,23–25 tripodal,26,27 carboxylate,28,29
bipyridyl,30 Schiff-base31 and crown-ether32 ligands exhibit the PL in
the range from near ultraviolet (UV) to yellow colour. To the best of
our knowledge the red luminescent Ce(III) complexes are still
unknown.
It was showed by Dorenboos that the energy and wave-
length of f–d transitions of the Ce(III) ions doped in inorganic
hosts varies in the range from near UV to red light.33–35
Noticeable, that the lowest energies and maximal wave-
lengths of these transitions are observed in sulphide
matrices. Therefore, it is reasonable to expect that the Ce(III)
molecular complexes with organosulphide ligands could
emit red light. Such compounds can be used as red lumino-
phores as well as potential photoredox catalysts which effi-
ciently harvest the visible light. In present work we have used
a set of azolyl-substituted thiophenolates to be applied as
ligands for the design of red luminescent Ce(III) molecular
complexes.
aG. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences,
Tropinina 49, 603950 Nizhny Novgorod, Russian Federation. E-mail: ilichev@iomc.
ras.ru
bNizhny Novgorod State University, Gagarina Avenue 23/2, 603950 Nizhny Novgorod,
Russian Federation
cSaint Petersburg State University, Universitetskaya Emb. 7/9, 199034 St Petersburg,
Russian Federation
† Electronic supplementary information (ESI) available: MALDI-TOF spectra,
details of crystallographic, collection and renement data for Ce(SSN)3(DME),
Ce(NSN)3(DME) and La(OSN)3(DME); PL spectra of solid La(OSN)3(DME). CCDC
1907215–1907217. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c9ra03199e
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16.21ꢀ (A/B), 12.20 (C/D) in Ce(SSN)3(DME) and La(OSN)3(-
DME), respectively), and the distances between the centers of
Results and discussion
ꢀ
ꢀ
ꢀ
these fragments are 3.376 A (A/B), 3.639 A (C/D) and 3.583 A
In order form novel cerium complexes we have used the thio-
phenols which contain in o-position the heterocyclic substitu-
ents – 2-benzimidazolyl (H(NSN)), 2-benzoxazolyl (H(OSN)) and
2-benzothiazolyl (H(SSN)). The reaction of the cerium silyla-
mide complex with respective thiophenols readily proceeds at
room temperature in DME media (Scheme 1) resulting in
a formation of targeted complexes in good yields. In case of
benzimidazolyl-substituted thiophenol (H(NSN)) an ultrasonic
treatment was applied because of poor solubility of H(NSN) in
DME. The Ce(III) complexes were isolated as air-sensitive orange
or yellow-orange powders.
In cases of benzimidazolyl and benzothiazolyl derivatives the
X-ray suitable crystals of the cerium complexes were grown.
However, all the attempts to obtain such crystals for the ben-
zoxazolyl derivative were failed. In order to study the structure
by X-rays the lanthanum analogue of OSN-based complex was
synthesized similarly to Scheme 1 but with the use of La
[N(SiMe3)2]3 as the rare-earth precursor. The X-ray suitable
crystals of this lanthanum complex were successfully grown.
According to X-ray data, the lanthanide complexes have
a similar molecular structure. These complexes are monomers
in which the Ln3+ cations are coordinated by three SSN
(Ce(SSN)3(DME)), NSN (Ce(NSN)3(DME)) and OSN (La(OSN)3(-
DME)) ligands and one neutral molecular DME (Fig. 1). Thus,
the coordination number of each lanthanide atom in these
complexes is eight, and the coordination environment of Ln3+ is
a distorted square antiprism (Fig. 2).
ꢀ
(A/B), 3.528 A (C/D) in Ce(SSN)3(DME) and La(OSN)3(DME),
respectively (Fig. 1a and c). These geometrical parameters
indicate the presence of intramolecular p/p interactions in
both complexes.37 Unlike them, in the Ce(NSN)3(DME) complex,
the corresponding values are 3.712 A and 25.52 (A/B), 3.891 A
and 35.62ꢀ (C/D) (Fig. 1b). Such values slightly exceed the
geometric criterion for the presence of pi–pi interactions.37
The Ce–S distances in Ce(SSN)3(DME) and Ce(NSN)3(DME)
ꢀ
ꢀ
ꢀ
ꢀ
lie in the range of 2.8588(8) O 2.9330(11) A and these values are
in a good agreement both with each other and with previously
published cerium complexes containing thiophenolate frag-
ments.38–40 The coordination bonds of Ce–N and Ce–O in
complexes Ce(SSN)3(DME) and Ce(NSN)3(DME) vary over
ꢀ
a wider range (2.549(4) O 2.891(3) A (Ce–N) and 2.568(2) O
ꢀ
2.661(2) A (Ce–O)) (Table 2S†). All Ln–X (X ¼ S, N, O) distances
(Table 2S†) in complex La(OSN)3(DME) are also in the range of
values characteristic for lanthanum complexes.40–42
Despite the large number of aromatic systems in the SSN, NSN
and OSN ligands, intermolecular p/p interactions in all structur-
ally characterized complexes are not detected. It is interesting to
note that the molecules of Ce(NSN)3(DME) form a dimeric pair in
a crystal (Fig. 3). The ligands of neighboring molecules are arranged
in such a way that the distance between the nitrogen atom of one
ꢀ
ligand and the sulfur atom of the other ligand is 3.375 A. This value
indicates the existence of the N–H/S interaction.43
The structure of Ce(OSN)3(DME) was not determined by X-
rays but the elemental analysis, similarity of the MALDI-TOF
spectra of this compound and its lanthanum counterpart and
identity of IR spectra of the La(III) and Ce(III) complexes indicate
that the complex Ce(OSN)3(DME) has a similar structure to its
lanthanum analogue. The most intensive signals in mass-
spectra of complexes Ce(SSN)3(DME), La(OSN)3(DME) recor-
The S(1)S(5)N(1)N(2) and S(3)N(3)O(1)O(2) planes in
Ce(SSN)3(DME), the S(1)S(3)N(1)N(3) and S(2)N(5)O(1)O(2)
planes in Ce(NSN)3(DME) and the S(1)S(3)N(1)N(2) and S(2)N(3)
O(4)O(5) ones in La(OSN)3(DME) are located almost parallel to
each other. The dihedral angles between these planes are 8.96ꢀ,
8.50ꢀ and 11.64ꢀ in Ce(SSN)3(DME), Ce(NSN)3(DME) and
La(OSN)3(DME), respectively.
+
ded in positive mode (Fig. 1Sa†) are ones corresponding to ML2
and M2L5+ species. The molecules of DME do not present in the
structures of the formed ions indicating its weak coordination.
It should be mentioned that the mass spectrum of La(OSN)3(-
DME) is similar to the spectrum of another complexes and
contains the same peaks corroborating the identical structure
of the complex. The spectra of these compounds recorded in
negative mode depicted on the gure of 1Sb† are also similar
and contain identical signals of MxLyꢁ – type ions. The presence
of additional sulfur and oxygen atoms may be result of partial
decomposition of DME or ligand under laser impact.
The complexes Ce(OSN)3(DME) and Ce(SSN)3(DME) in the
solid state exhibit PL in the red range of visible light (Fig. 4).
While the complex Ce(NSN)3(DME) is non-luminescent. The
broad shape of the spectra, the location in the red region of the
spectrum and the independence of the emission intensities
from the temperature indicate the f–d nature of the PL. The
absence of such PL in the case of benzimidazole derivative is
caused, apparently, by quenching effect of hydrogen bounds.
But in the DME solutions the observed red PL of the Ce(III)
complexes disappears. In order to understand this feature, it is
reasonable to use the lanthanum derivatives as reference
The NSN, SSN and OSN ligands in these complexes are largely
non-at. Such geometry is characteristic of related ligands.36 The
dihedral angles between the thiophenolate and benzothiazolyl,
benzimidazolyl and benzoxazolyl fragments are 38.93 O 56.13ꢀ,
40.29 O 49.77ꢀ and 21.06 O 25.69ꢀ, respectively.
It is interesting to note that the NSN and OSN ligands in
Ce(SSN)3(DME) and La(OSN)3(DME) complexes are arranged in
such a way that the planes of the ve-membered heterocycle of
one ligand (A, D) and the phenyl ring of the thiophenolate
fragment of the second ligand (B, C) are almost parallel to each
other (the dihedral angles are 15.62ꢀ (A/B), 27.02ꢀ (C/D) and
Scheme 1
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Fig. 1 Molecular structures of complexes Ce(SSN)3(DME) (a), Ce(NSN)3(DME) (b) and La(OSN)3(DME) (c). The probability ellipsoids are drawn at
the 30% level. The hydrogen atoms are omitted for clarity.
complexes.
A
comparison of the optical properties of the substituted thiophenolates exceed thousands of
L
lanthanum and cerium complexes has been provided with an molꢁ1 cmꢁ1
.
36 As a result of overlapping of these absorption bands
example of OSN ligand. The complex La(OSN)3(DME) exhibit the orange color of Ce(OSN)3(DME) virtually disappears in the
a broad band PL peaked at 500–530 nm in solid state (Fig. 2S†). solution.
The PL behavior in DME solution of both (La and Ce) complexes
is similar to their Gd counterpart.36 As one can see from a photo
of the samples of La(OSN)3(DME) and Ce(OSN)3(DME) the
compounds have different color (Fig. 5).
Experimental
General procedures
This difference, evidently, is caused by the f–d absorption of Ce3+
ions. Orange color corresponds to the absorption in the bluish-
green region at about 500 nm. However, in the DME solutions the
absorption spectra of both compounds are almost identical, no
absorption at 500 nm is observed for the cerium complex. Appar-
ently, this behavior is caused by a shiing of the f–d absorption
towards blue region upon solvatation. It is known that the energy of
f–d transitions in free Ce3+ ion corresponds to UV region and it can
be only red shied by the crystal eld of the ligands.33 The most
powerful shiers are sulphides. Consequently, the solvatation and
dissociation of cerium organosulphide complexes may result only in
blue shi of the f–d transitions. It is important to note that typical
All manipulations were carried out under vacuum using
standard Schlenk techniques or in an argon glove box (H2O <
0.1 ppm; O2 < 1 ppm). The reagents including thiosalicylic
acid, polyphosphoric acid, o-aminophenol, o-amino-
thiophenol, o-phenylenediamine, lanthanum and cerium
amides Ln[N(SiMe3)2]3 (95–98% purity) were purchased from
commercial sources and used as received. The solvents 1,2-
dimetoxyethane (DME), hexane and toluene were dried by
reuxing over sodium for 12 h. The C, H, N and S elemental
analyses were performed on a Euro EA 3000 elemental ana-
lyser. The lanthanide contended was analysed by com-
plexometric titration. IR spectra were obtained on
a PerkinElmer 577 spectrometer and recorded from 4000 to
450 cmꢁ1 as a Nujol mull on KBr plates. Photoluminescence
values of absorption coefficients range at hundreds of
L
molꢁ1 cmꢁ1 (ref. 44) for f–d transitions of Ce3+ while absorption of
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Fig. 3 Fragment of crystal packing of the Ce(NSN)3(DME) complex.
Some hydrogen atoms and non-coordinated DME molecules are
omitted for clarity.
Fig.
4 PL spectra of solid complexes Ce(OSN)3(DME) and
Ce(SSN)3(DME). Excitation – 405 nm laser diode.
Synthetic procedures
H(OSN)
(2-(20-mercaptophenyl)benzoxazole).
o-Amino-
phenol (2.18 g, 20 mmol) and thiosalicylic acid (3.08 g, 20
mmol) were put in 100 mL two-neck ask. The mixture was
blown with argon and then 50 mL of toluene was added. The
Fig. 2 The coordination environment of Ln in complexes Ce(SSN)3(-
DME) (a), Ce(NSN)3(DME) (b) and La(OSN)3(DME) (c).
of solid samples was excited with a 100 mW, 405 nm laser
diode or 365 nm UV diode and detected in a region 365–
1000 nm with Ocean Optics USB2000 spectrometer. The
spectroscopic measurements of the compounds were per-
formed in DME solution using a 1 cm vacuumed quartz cell.
The absorption spectra were recorded with a PerkinElmer
Lambda 25 UV/VIS spectrometer from 200 to 800 nm. The PL
and PLE spectra were recorded with a PerkinElmer LS 55
uorescence spectrometer. MALDI-TOF mass-spectra of the
compounds were obtained on a Bruker Microex LT spec-
trometer equipped with a nitrogen laser (337 nm). During
experiments 0.5 mg of solid samples were deposited on
a stainless steel target plate, rubbed over the surface by using
a spatula and analysed.
Fig. 5 DME solution absorption spectra (a) and photo (b) of complexes
Ce(OSN)3(DME) (right) and La(OSN)3(DME) (left).
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ask was mixed with a magnetic stirrer for 10 minutes, and then analysis: found C, 53.98; H, 3.59; N, 4.40; S, 20.13; Ce, 14.62 for
phosphorus trichloride (1.75 mL, 20 mmol) was added dropwise 43H34N3O2S6Ce: calculated C, 53.95; H, 3.58; N, 4.39; S, 20.10;
C
for 10 minutes at 40–60 ꢀC. The mixture was reuxed for 4 hours Ce, 14.64. Crystals used for X-ray analysis was obtained by
with argon atmosphere. Then reaction mixture was cooled at crystallization from DME solution. IR (Nujol, cmꢁ1): 1581 (m),
the room temperature and volatile products were rotary evap- 1561 (w), 1547 (w), 1409 (w), 1322 (m), 1249 (w), 1201 (s), 1106
orated. Remaining viscous product was sublimed twice (125– (s), 1052 (s), 970 (s), 861 (s), 760 (s), 700 (m), 690 (m), 644 (m)
ꢁ3
ꢀ
150 C; 1 ꢂ 10 mbar) to give 923 mg of H(OSN) (20.6%) as (Fig. 3S†).
light-beige powder. IR (Nujol, cmꢁ1): 2320 (br), 1679 (w), 1589
Ce(NSN)3(DME). A mixture of 2-(20-mercaptophenyl)benz-
(m), 1561 (w), 1539 (m), 1339 (w), 1272 (m), 1243 (s), 1196 (m), imidazole (H(NSN)) (170 mg, 0.75 mmol) and Ce[N(SiMe3)2]3
1092 (w), 1032 (s), 925 (m), 864 (w), 816 (s), 695 (w), 655 (w), 627 (155.1 mg, 0.25 mmol) in DME solution (10 mL) was stirred in
(w) (Fig. 3S†). Mass spectra: m/z ¼ 227. Elemental analysis: ultrasonic bath for 10 hours at the room temperature. Then
found C, 68.73; H, 3.95; N, 6.19; S, 14.12 for C13H9NOS: calcu- volatile products were rotary evaporated. Solid precipitate
lated C, 68.70; H, 3.99; N, 6.16; S, 14.11.
was washed with hexane and dried in vacuum for 1 hour at
H(SSN) (2-(20-mercaptophenyl)benzothiazole). The synthesis the room temperature. Product (Ce(NSN)3(DME)) was iso-
was realized similarly to H(OSN) from o-aminothiophenol (2.14 lated as yellow-orange powder in 86% yield (195.0 mg).
mL, 20 mmol), thiosalicylic acid (3.08 g, 20 mmol) and phos- Elemental analysis: found C, 57.02; H, 4.15; N, 9.30; S, 10.60;
phorus trichloride (1.75 mL, 20 mmol) the product was isolated Ce, 15.41 for C43H37N6O2S3Ce: calculated C, 57.00; H, 4.12; N,
in 41.9% yield (2 g) as orange-red powder. IR (Nujol, cmꢁ1): 2320 9.27; S, 10.62; Ce, 15.46. Crystals used for X-ray analysis were
(br), 1586 (w), 1555 (w), 1314 (m), 1243 (m), 1222 (w), 1212 (m), obtained by crystallization from DME solution.
1041 (m), 965 (s), 939 (s), 858 (w), 854 (s), 690 (m), 650 (w), 625
(w) (Fig. 3S†). Mass spectra: m/z ¼ 243. Elemental analysis: Ce(OSN)3(DME)
found C, 64.18; H, 3.75; N, 5.79; S, 26.36 for C13H9NS2: calcu- (H(OSN)) (170.5 mg, 0.75 mmol) and La[N(SiMe3)2]3 (155.0 mg,
lated C, 64.16; H, 3.73; N, 5.76; S, 26.35. 0.25 mmol). Product (La(OSN)3(DME)) was isolated as lemon-
H(NSN) (2-(20-mercaptophenyl)benzimidazole). A mixture of yellow powder in 91% yield (206.5 mg). Elemental analysis:
thiosalicylic acid (3.08 g, 20 mmol) and o-phenylenediamine found C, 56.85; H, 3.71; N, 4.65; S, 10.60; La, 15.25 for C43
(2.16 g, 20 mmol) was stirred in polyphosphoric acid (50 mL) 34N3O5S3La: calculated C, 56.89; H, 3.77; N, 4.63; S, 10.60; La,
La(OSN)3(DME). The synthesis was realized similarly to
from
2-(20-mercaptophenyl)benzoxazole
-
H
at a temperature of 220 ꢀC for 5 h. Then the reaction mixture 15.30. IR spectrum of La(OSN)3(DME) is identical to that of
was cooled to the room temperature and solved in ice-cold Ce(OSN)3(DME). Crystals used for X-ray analysis were obtained
water. Then sodium hydrocarbonate was added until by crystallization from DME solution.
neutral or alkalescent pH. The precipitate was ltered, dried
in vacuum and sublimed to give H(NSN) as yellow powder in
21% yield (0.95 g). Elemental analysis: found C, 69.03; H,
X-ray
4.51; N, 12.32; S, 14.16 for C13H10N2S: calculated C, 69.00; H, The X-ray diffraction data for the complexes were collected on
4.45; N, 12.38; S, 14.17. IR (Nujol, cmꢁ1): 3055 (w), 2300 (br), a Bruker AXS SMART APEX (Ce(SSN)3(DME)) and Oxford
1942 (w), 1728 (w), 1690 (w), 1587 (w), 1556 (m), 1495 (w), Xcalibur Eos (La(OSN)3(DME), Ce(NSN)3(DME)) diffractome-
ꢀ
1315 (m), 1243 (m), 1215 (m), 968 (m), 946 (m), 752 (s), 690 ters (Mo-Ka radiation, u-scan technique, l ¼ 0.71073 A). The
(m). Mass spectra: m/z ¼ 226.
intensity data were integrated by SAINT (Ce(SSN)3(DME))45
Ce(OSN)3(DME). A mixture of 2-(20-mercaptophenyl)ben- and
CrysAlisPro
(La(OSN)3(DME),
Ce(NSN)3(DME))46
zoxazole (H(OSN)) (170.5 mg, 0.75 mmol) and Ce[N(SiMe3)2]3 programs. SADABS (Ce(SSN)3(DME))47 and SCALE3 ABSPACK
(155.1 mg, 0.25 mmol) in DME solution (10 mL) was stirred at (La(OSN)3(DME), Ce(NSN)3(DME))48 programs were used to
the room temperature for 30 minutes. Then the volatile perform absorption corrections. The La(OSN)3(DME)
products were rotary evaporated. Solid precipitate was washed complex was solved by direct method and Ce(NSN)3(DME)
with hexane and dried in vacuum for 1 hour at the room and Ce(SSN)3(DME) complexes were solves by dual method.49
2
temperature. Product (Ce(OSN)3(DME)) was isolated as orange All structures were rened on Fhkl using SHELXTL package.50
powder in 89% yield (202.2 mg). Elemental analysis: found C, All non-hydrogen atoms were rened anisotropically. All
56.84; H, 3.72; N, 4.65; S, 10.60; Ce, 15.40 for C43H34N3O5S3Ce: hydrogen atoms were placed in calculated positions and were
calculated C, 56.81; H, 3.77; N, 4.62; S, 10.58; Ce, 15.41. IR rened in the riding model (Uiso(H) ¼ 1.5Ueq(C) for CH3-
(Nujol, cmꢁ1): 1601 (m), 1584 (m), 1550 (m), 1519 (m), 1415 groups and Uiso(H) ¼ 1.2Ueq(C, N) for other groups). The
(m), 1240 (s), 1190 (m), 1134 (m), 1044 (s), 1018 (w), 1004 (w), main crystallographic data and structure renement details
861 (s), 813 (s), 653 (m), 627 (m), 560 (m) (Fig. 3S†). Crystals for Ce(NSN)3(DME), La(OSN)3(DME), Ce(SSN)3(DME) are
used for X-ray analysis were obtained by crystallization from presented in Table 1S.† The asymmetric unit of Ce(SSN)3(-
DME solution.
DME) contains a solvate molecule of DME whereas the crys-
Ce(SSN)3(DME). The synthesis was realized similarly to tals of Ce(NSN)3(DME) contain 1.25 disordered molecules of
Ce(OSN)3(DME) from 2-(20-mercaptophenyl)benzothiazole DME per one complex molecule.
(H(SSN)) (and 182.3 mg, 0.75 mmol) and Ce[N(SiMe3)2]3
CCDC 1907215 (La(OSN)3(DME)), 1907216 (Ce(NSN)3(DME))
(155.1 mg, 0.25 mmol). Product (Ce(SSN)3(DME)) was isolated and 1907217 (Ce(SSN)3(DME)) contain the supplementary
as yellow-orange powder in 92% yield (220.1 mg). Elemental crystallographic data.†
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9 H. Li, C. Xie, R. Lan, S. Zha, C.-F. Chan, W.-Y. Wong, K.-L. Ho,
B. D. Chan, Y. Luo, J.-X. Zhang, G.-L. Law, W. C. S. Tai, J.-C.
Conclusions
¨
G. Bunzli and K.-L. Wong, J. Med. Chem., 2017, 60, 8923.
In summary, we have synthesized a set of novel Ce(III) complexes
with azolyl-substituted thiophenolate ligands – 2-(20-mercapto-
phenyl)benzimidazole (NSN(H)), 2-(20-mercaptophenyl)benzox-
azole (OSN(H)) and 2-(20-mercaptophenyl)benzothiazole
(SSN(H)). The lanthanum complex with OSN ligand has been
also synthesized to be used as a reference compound. The data
of X-ray and MALDI-TOF revealed that all the synthesized
complexes are monomeric species which contain three anionic
thiophenolate ligands and one coordinated neutral DME
molecule. It was found that Ce(OSN)3(DME) and Ce(SSN)3(-
DME) in the solid state exhibit the PL peaked at 620 nm. This is
the maximal wavelength ever observed for f–d luminescent
Ce(III) molecular complexes. But no red PL is observed in the
solutions of these complexes that is caused, apparently, by the
blue shi of the f–d transitions. We believe that synthesis of
novel molecular Ce(III) f–d luminophores with long-lived and
low-energy 5d states would become a modern challenge in
coordination chemistry because these compounds will be
useful as red or infrared emitters and can replace noble metal
derivatives in photoredox catalyzed processes.
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Conflicts of interest
There are no conicts to declare.
22 D. M. Kuzyaev, T. V. Balashova, M. E. Burin, G. K. Fukin,
R. V. Rumyantcev, A. P. Pushkarev, V. A. Ilichev,
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Acknowledgements
This work was supported by the Russian Foundation for Basic
Research (project no. 18-33-20103). The structure of the
complexes was dened in the Framework of the Russian State
Assignment (Theme 45.6, Reg. N AAAA-A19-119011690055-0).
The work was performed using the instrumental base of the
Analytical Center of the G. A. Razuvaev Institute of Organome-
tallic Chemistry, Russian Academy of Sciences. The analysis of
complexes using MALDI mass spectrometry was done in
accordance with the task of Ministry of Science and Higher
Education of Russia (task 4.5706.2017/B).
26 X.-L. Zheng, Y. Liu, M. Pan, X.-Q. Lu, J.-Y. Zhang, C.-Y. Zhao,
Y.-X. Tong and C.-Y. Su, Angew. Chem., Int. Ed., 2007, 46,
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