En Route Activity of Hydration Water Allied with Uranyl (UO22+) Salts Amid Complexation Reactions with an Organothio-Based (O, N, S) Donor Base

Article abstract of DOI:10.1021/acs.inorgchem.8b03622

This study provides en route activity of hydration water allied with uranyl salts amid complexation reactions with a donor species L bearing O, N, and S (phenolic, -OH; imine, -HC=N-; and thio-, -S-) donor functionalities. The UO₂²⁺/

Full text of DOI:10.1021/acs.inorgchem.8b03622

Article
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
pubs.acs.org/IC
2+
En Route Activity of Hydration Water Allied with Uranyl (UO ) Salts
2
Amid Complexation Reactions with an Organothio-Based (O, N, S)
Donor Base
Jagriti Singh, Dolly Yadav, and Jai Deo Singh*
Department of Chemistry, Indian Institute of Technology Delhi (IITD), Hauz Khas, New Delhi 110 016, India
*
S Supporting Information
ABSTRACT: This study provides en route activity of hydration water allied with uranyl salts amid complexation reactions with
2
+
a donor species L bearing O, N, and S (phenolic, −OH; imine, −HCN−; and thio-, −S−) donor functionalities. The UO
/
2
L reaction encounters a series of hydrolytic steps with hydration water released from uranyl salts during the complexation
processes. Primarily, the coordinated [L(−HC=N)(OH)(−HC=N) → UO (NO ) /(OAc) ] species formed during the complexation
2
3 2
2
process undergoes partial hydrolysis of the coordinated ligand resulting in the isolation of an aldehyde coordinated uranyl
species [L(−HC=N)(OH)(−HC=O) → UO (NO ) /(OAc) ]. The influence of hydration water continued as the reaction further
2
3 2
2
proceeded to the next stage resulting in alteration of the aldehyde coordinated uranyl species [L(−HC=N)(OH)(−HC=O)
→
UO (NO ) /(OAc) ] to an oxidized carboxy coordinated uranyl species [L → (NO )/(OAc)] without
2
3 2
2
(−HC=N) (OH){−C(O)O}
3
2
the use of any external oxidizing agents. These studies are of particular significance as they allow one to realize the adventitious
role of hydration water released from commonly used uranyl salts during their reaction with organic donor substrates in
2
+
nonaqueous medium. These results also form an experimental basis to understand the critical behavior of UO2 ion activity (as
oxidizing, reducing, or catalytic) relevant in many chemical, biological, and environmental processes.
INTRODUCTION
An understanding of the behavior of the UO22+ ion among the
actinides has been the subject of particular attention due to
increasing global nuclear energy demand. As a consequence,
their presence in nature also poses serious environmental
concerns where they may come across a myriad of chemical,
geochemical, biochemical, and environmental processes.
Naturally, the knowledge of the behavior of cationic UO2
is a prerequisite for a precise monitoring, speciation, and
furthermore their interactions during migration within
terrestrial humic substances. Basically, humic substances
organic solutions result in structural diversities, and therefore,
there is always uncertainty in their actual speciation and
geochemical migration. For example, U(VI) has a strong
tendency to hydrolyze and support a range of oxo- and
■
1
2
+
(2m−n)
hydroxo- species (mUO + nH O ⇌ (UO ) (OH)
+
2
2
2 m
n
+
nH , where the n and m range is 1−5 or 1−9) in aqueous
6
2
medium. There is also a bias to the hydrolysis reaction of the
2
+
2
+
UO2 ion in different environments (acidic or basic conditions
+
as well as aerobic and anaerobic environments) as H and
−
2+
OH ions are freed from hydrolytic activity of UO2 ion
through their biotic and abiotic interactions. This further leads
to substantial uncertainties about speciation of the uranyl ion
in a similar environment as different species and several
coexisting polymeric species at similar concentration and pH
3
have been considered as possible remediation strategies in
safe nuclear waste alteration and reprocessing of nuclear fuel
4
2+
2
sources. Although the interactive behavior of the UO ion
7
range may be produced. Nevertheless, an understanding of
toward humic substances is well documented, uncertainties
remain due to the structural complexities that vary as a
function of pH or as a function of metal ion concentration.
2
+
the behavior of the UO2 ion in diverse environments is
5
2
+
Similarly, intricate reaction dynamics of the UO2 ion that
Received: December 29, 2018
normally go by an oxidative−reductive process in aqueous or
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b03622
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Scheme 1. Synthesis of O, N, S-Based Donor Species L and Its Reactions with UO22+ Salts
−
4
−3
Figure 1. Spectrophotometric UV−Vis titrations: (a) spectroscopic changes titrating the L (1 × 10 M) with UO (NO ) ·6H O (1 × 10 M) in
2
3
2
2
−4
−3
acetonitrile, (b) spectroscopic changes titrating the L (1× 10 M) with UO (OCOCH ) ·2H O (1 × 10 M) in acetonitrile.
2
3
2
2
considered very essential in order to infer their precise
speciation and remediation. Therefore, the pursuit of any new
that contamination of UO22+ in groundwater is a serious
environmental concern and many enzyme catalytic sites in
biological systems frequently embrace nitrogen or/and sulfur
as coordination sites. Interestingly, the ligand L bears donor
sites usually present in humic substances. Usually humic
substances contain a variety of phenolic-, carboxylic-, or even
enolic donor functionalities and are widely distributed in soils,
sediments, oceans, and fresh and ground waters.
2
+
knowledge is fundamental to the advancement of UO
2
8
chemistry, and this can realized through the use of variable
9
donor species or well-structured organic species with
heteroatomic donor combinations. Indeed, the outcome of
their combinations with the UO22 ion may allow further
promoting and understanding structure−property relation-
ships. These studies could offer practical advantages compared
to their individual donor analogues in terms of their
discriminatory functions. Our group also initiated this line of
research by investigating cyclic organic species bearing
heteroatomic (O, N, X) (X = S, Se, or Te) donor
combinations. Such species exhibited a selective binding
+
RESULTS AND DISCUSSION
■
The donor species L was obtained by the condensation
reaction of 2,6-diformyl-4-methylphenol with phenylthioethyl-
amine and was found to be enough stable toward atmospheric
air in ambient laboratory conditions. The outline of the
synthetic procedure for ligand synthesis and their successive
complexation reactions with uranyl ion is shown in Scheme 1.
In order to understand the interactive behavior of L with
metal ions, metal/ligand titration experiments were performed
2
+
affinity for UO2 ions over a variety of transition and heavy
10
metal ions including alkali and alkaline-earth metal ions.
Considering further new application of the chalcogen related
2
+
9
species in UO2 chemistry and their functional behavior, we
recognized and came across an essentially useful acyclic donor
species L bearing an O, N, S donor combination to examine
and monitored by UV−vis spectroscopic changes. Remarkably,
2+
the spectral changes on addition of the UO
ion as
2
2+
the behavior of the UO2 ion. The donor species L bearing
phenolic (−OH), imine (−HCN−), and thio- (−S−), a
Schiff base type donor, is an obvious choice to study its
chemistry with uranyl ions. Besides heteroatomic character-
istics, S···heteroatom(s) interactions may also provide the
donor species as well as their complexes an additional intrinsic
chemical stability to overcome the difficulty associated with
this kind of species, which are often prone to hydrolysis.
Apparently, this study may also be interesting with the view
UO (NO ) ·6H O or UO (OCOCH ) ·2H O to a solution
2
3 2
2
2
3 2
2
of L was special compared to those observed for other
hydrated metal cations (Figure S1). In spectroscopic measure-
2
+
ments, on gradual addition of a solution of the UO2 ion to a
solution of L in acetonitrile, a significant blue shift was
2
+
exhibited when UO2 :L concentrations reached to a molar
ratio of 0.6:1 and continued up to a molar ratio of 2:1 (Figure
1). The appearance of two isosbestic points at 431 and 354 nm
for UO (NO ) ·6H O and 442 and 362 nm for
2
3
2
2
B
DOI: 10.1021/acs.inorgchem.8b03622
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Inorganic Chemistry
Article
1
2+
Figure 2. Changes observed in H NMR spectroscopy on titrating the L with UO (NO ) ·6H O in CD CN (up to L:UO ratio reached 1:0.1 to
2
3
2
2
3
2
1
:1.2). (inset) Peak “a” corresponding to imine proton (−H CN) of L, appearance of new peaks “b” corresponding to coordinated imine proton
a
(
−H CN) and “c” (−H CO) as a consequence of in situ hydrolysis of coordinated species.
b
c
UO (OCOCH ) ·2H O in UV−vis spectra as a function of the
(Figures S5 and S6). The formation of −CHO functionality
might result as a consequence of partial hydrolysis of
coordinated imine linkage hydrolyzed due to released
hydration water associated with uranyl salts. The hydrolysis
aspect may not be very unexpected; however, the partially
hydrolyzed ligand species appeared to remain coordinated to
2
3 2
2
2
+
added UO ion was found to be consistent and reproducible
2
upon repeated experimentation. Nevertheless, these results
reveal an intricate solution behavior, where possibilities of
competition between solvation (CH CN or CH OH) vs
3
3
desolvation, hydration/hydrolysis, complexation followed by
hydrolysis, partial or complete hydrolysis of ligand (L) or
metal salts, and deprotonation of the phenolic (−OH) of
2
+
the UO2 ion through its hydrolytically evolved aldehyde
(−HCO) function.
2
2
+
ligand are likely to occur. Therefore, a real picture of UO
−
The formation of possible uranyl species was experiential
and therefore determining the exact nature and geometry of
these species could reveal precise speciation. In this regard, a
series of experiments were carried out where, a mixed
ligand interactions in organic solvent may not be directly
precise, especially when speciation of the UO22 ion is passing
through a series of parallel reactions with respect to other
metal cations.
+
2
+
(UO2 :L) solution in acetonitrile in varied molar concen-
trations (in molar fraction from 0.2:1 to 1:2) under ambient
conditions were used to obtain their crystals. Upon repeated
attempts, suitable crystal from a solution of combination of
UO (NO ) ·6H O and L (1:1) in acetonitrile was obtained
1
The H NMR spectroscopic titration studies of L with
UO (NO ) ·6H O or UO (OCOCH ) ·2H O in CD CN
2
3 2
2
2
3 2
2
3
2
+
provide a rather reasonable picture of the UO2 ion binding
to some extent and also its post consequences. In
representative H NMR experiments, on adding small aliquots
2
3 2
2
1
and analyzed by single-crystal X-ray diffraction analysis.
The perspective view of the complex 1 (space group P21/c)
is shown in Figure 3. In the crystal structure of the species 1,
2
+
of UO2 solution (a solution of UO (NO ) ·6H O in
2
3
2
2
CD CN) to a solution of L (in CD CN) revealed the
3
3
2
+
appearance of two types of −HCN protons, where one of
the UO2 ion was found to be coordinated with aldehyde
oxygen (−HCO) and phenolic (−OH) as donor atoms of a
partially hydrolyzed ligand with (U−O) bond distances of
2.442(3) and 2.337(3) Å, respectively. The U−O bond
distances for [OUO] are 1.738(4) and 1.733(5) Å with
a bond angle of 178.0(2)°. The nitrate anions were found to be
them coordinates to the UO22 ion via its −N donor center.
+
The coordinated imine proton (−H CN) was assigned to
b
2+
9
.53 ppm. As the concentration of the UO ion increased, the
2
spectral changes continued along with the appearance of the
aldehyde (−H CO) proton signal at δ 10.68 ppm (Figure
c
1
2+
2
). Similar spectral changes in the H NMR spectroscopic
coordinated to the UO2 ion in nearly symmetrical bidentate
measurements were also seen when a solution of UO2-
OCOCH ) ·2H O (in CD CN) was used for titration with L
chelation mode. The U−O (U−ONO ) bond distances were
2
(
found in the range between 2.519(4) and 2.491(3) Å and thus
3
2
2
3
C
DOI: 10.1021/acs.inorgchem.8b03622
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Inorganic Chemistry
Article
2
.534(5) Å. The newly generated carboxylate functionality, in
fact, acts as both bridging as well as bidentate chelating donors
between two uranyl ions and providing nearly a symmetrical
dinuclear structure to two UO2 ions with a U···U separation
of 4.2728(5) Å. The binding of phenolic −OH with a (U−O)
bond length of 2.331(5) Å was similar as seen in 1. The
remaining coordination environment around each uranyl ion
was completed with the help of one of the nitrate ions bonded
to each side of the UO2 ion in bidentate chelation mode. The
crystal structure data of the complex species 3 further allowed
us to realize the alteration of complex species 1 → 3, i.e.,
2
+
2
+
[
[
L ( − H C = N ) ( O H ) ( − H C = O )
→
U O ( N O ) ] t o
2 3 2
Figure 3. Perspective view of the partially hydrolyzed uranyl complex
L( → UO (NO )] (1 → 3).
−HC=N) (OH){−C(O)O}
2
3
2
1
[L(−HC=N)(OH)(−HC=O) → UO (NO ) ].
2+
2
2
3 2
Therefore, the behavior of the UO ion with the acetate
ion further allowed us to examine the crystal studies for
complex 4. The complex species 4 also showed similar bonding
patterns and geometrical arrangement around the uranyl ion as
were seen in complex 3 (Figure 4). It is evident from a
comparison of all three structures (species 1, 3, and 4) that the
providing a hexagonal−bipyramidal coordination environment
2
+
to the UO ion.
2
Curiously, crystal structures obtained from a combination of
hydrated uranyl salts [UO (NO ) ·6H O or
2
3
2
2
UO (OCOCH ) ·2H O)] with L in molar concentration
2+
2
3 2
2
UO2 ion is confined in similar geometrical arrangements, i.e.,
(
1.2:1) in acetonitrile at room temperature were also desirable
a hexagonal−bipyramidal coordination environment. Further,
as changes in UV−vis spectra of L in acetonitrile with
nearly identical U−O bond distances (U−OH
) of
(
phenolic)
2+
increased concentration of UO2 ions were noticeable. The
complex species 3 and 4 were crystallized in the space group
P21/c, and perspective views of complex species 3 and 4 are
shown respectively in Figures 4 and 5.
2.341(3), 2.331(5), and 2.328(3) Å and C−O bond distances
C−OH ) of 1.294(5), 1.303(8), and 1.315(6) Å were
(
(
phenolic)
observed in species 1, 3, and 4, respectively. The U−O bond
distances were found slightly longer than those observed in a
number of uranyl complexes (usually in range of 2.231−2.296
Å) obtained from deprotonated Schiff bases resulting from 2,6-
diformylphenol derivatives. Similarly the C−O bond distances
were found to be similar in range as seen for free Schiff bases
11
or their metal complexes in non-deprotonated form.
Structurally, the donor species appeared to be symmetrical
1
in nature as the H NMR spectrum obtained in CDCl or
3
CD CN showed desired resonances for species L with
3
expected multiplicity. The donor species was also found to
be enough stable toward other hydrated metal cations and
barely showed any hydrolysis of imine (CN) linkage except
2
+
during its reactivity with the UO ion. The L also forms
2
complexes with other metal cations in their hydrated forms,
and no hydrolytic activity on the donor base was seen. Besides,
deprotonation of the phenolic proton on association with other
metal cations was also not seen in current reaction conditions.
Nevertheless, the complex species 1 crystallized out from an
acetonitrile solution as a partially hydrolyzed species
Figure 4. Perspective view of species 3[L(−HC=N)(OH)(COO)
→
UO (NO )] as dinuclear uranyl species.
2
3
2
[
L(−HC=N)(OH)(−HC=O) → UO (NO ) ] confirmed unequal
2 3 2
reactivity of the two azomethine substituted thio-donor arms
2
+
of L toward UO2 ions. The uranyl coordinated azomethine
group undergoes a hydrolytic reaction caused by released
hydrated water from starting materials resulting in the
formation of aldehydo-coordinated species 1 or 2 and parting
the other azomethine (−HCN−) donor arm away from
coordination. It is interesting to note that at this stage of
reaction, hydrolysis of the coordinating uranyl part was not
seen. On moving from speciation of 1 or 2 to further 3 and 4,
the present findings suggest that there is no deprotonation of
2
+
phenolic proton of L in the presence of UO2 ion in methanol
or acetonitrile. The astonishing issue, which is hard to ignore,
is alteration of [L(−HC=N)(OH)(−HC=N) → UO (NO ) /(OAc) ]
Figure 5. Perspective view of species 4 [L(−HC=N)(OH)(COO)
→
UO (OCOCH )] as a dinuclear uranyl species.
2
3
2
2
3 2
2
(
complexes 1 or 2) to oxidized species [L(−HC=N)(OH)(−COO)
→
Complex species 3 that resulted as a conversion of CHO →
COO further binds to the uranyl ion with (U−O) bond
distances of 2.442(5) Å and to another uranyl ion in bidentate
UO (NO )/(OAc)] (complexes 3 or 4), i.e., conversion of
2 3 2
−
−
−CHO to −COO donor functionalities without use of any
external oxidizing agents. In general, binding of uranyl ions
with carboxylate functionality is seen in enzymes and humic
chelation mode with (U−O) bond distances of 2.481(5) and
D
DOI: 10.1021/acs.inorgchem.8b03622
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Inorganic Chemistry
Article
1
2
substances. Basically, humic substances have been considered
CONCLUSIONS
■
2+
as a possible way to alter UO2 and retard its biogeochemical
The present study is of particular interest as it targets the use of
O, N, S-based organic donors in understanding uranyl
chemistry under nonaqueous conditions. The donor combi-
nations of ligand species provide opportunities in under-
standing the hidden behavior of the uranyl ion that would not
have been possible to observe in aqueous medium. The present
study is of particular curiosity that allows one to realize the
adventitious role of hydration water, normally associated with
analytically used uranyl salts, which influences the reactivity of
13
migration under abiotic and biotic conditions. A correlation
of spectroscopic observations with those of single crystal X-ray
studies of 1, 3 and 4 allows one to remark on the chemical
−
pathways for the conversion of −CHO to −COO
functionality. Normally, complexes comprising uranyl-Schiff
bases with the CN bond are relatively stable in organic
solvents albeit little bit susceptible to hydrolysis under acidic
conditions. Hydrolysis of coordinated L in present case may be
suggested to involve a carbinolamine [−NH−CH(OH)−]
intermediate, formed by the addition of released water to the
imine linkage followed by C−N bond cleavage in the N
protonated form. Further, the possible chemical conversion of
2
+
UO
ion through its en route activity. These results also form
2
2
+
an experimental basis in viewing the critical behavior of UO2
ion activity (as oxidizing, reducing, or catalytic) and may be
relevant to many chemical, biological, and environmental
processes especially in their biogeochemical migration.
−
CHO to −COOH is likely to happen only under oxidative
conditions either when oxidizing agents are added or possible
oxidizing substrates were formed during the reaction. We
further point out that formation of peroxouranyl species from
EXPERIMENTAL SECTION
■
Caution! Uranyl nitrate UO (NO ) ·6H O and uranyl acetate
2
3
2
2
2
+
238
UO2 has also been suggested under photolytic and
UO
2
(OCOCH
3
)
2
·2H
2
O principally containing the isotope ( U) are
14
reportedly radioactive materials and must be handled in dedicated fume
hoods or glove boxes with a proper facility for their disposal. Any solid
waste (such as gloves) can be disposed of as ordinary waste, unless heavily
contaminated.
nonphotolytic conditions in aqueous medium. Mostly these
reports suggest that the peroxide formation occurs due to
2
+
+
water oxidation by a light generated excited *U(VI)O2
species to yield H O and the reduced uranyl species U(V)O
2
2
2
Synthesis of Ligand (L). To a stirred solution of 2,6-diformyl-4-
methylphenol (0.25 g, 1.0 mmol) in dry methanol (20 mL) 2-
phenylthioethylamine (2.0 mmol) in dry methanol (20 mL) was
added dropwise, and the reaction mixture was allowed to stir at room
temperature for 4−5 h under dinitrogen atmosphere. After
completion of the reaction, the solvent was evaporated under reduced
pressure, which gave ligand as a yellow solid that was pure enough for
further reactions.
that is consequently reoxidized by O or may disproportionate
2
to yield U(VI)O22 and insoluble U(IV) species.
+
15−17
Complex species 1 or 2 were found to be enough stable
when left open for weeks to atmospheric air in ambient
laboratory conditions and even recovered unaltered from their
solutions in methanol or acetonitrile. We also could not find
any other genuine experimental reason in our reaction
conditions to support formation of H O or interference of
C H N OS (L) Yield: 85%; mp 60 °C; IR (KBr pellet): ν (in
2
5
26
2
2
−
1
cm ) 3727, 3445, 3056, 2924, 2855, 2360, 1636, 1596, 1532, 1457,
368, 1033, 971, 840, 739, 688, 490; H NMR (300 MHz, CDCl ): δ
2
2
1
1
(
(
=
atmospheric oxygen that can lead to the conversion of uranyl
→ UO (NO ) /
3
ppm): 8.48 (s, 2H), 7.41−7.38 (m, 4H), 7.35 (s, 2H), 7.29−7.24
coordinated −CHO [L
(
−HC=N)(OH)(−HC=O)
2
3 2
m, 4H), 7.19−7.14 (m, 2H), 3.82 (t, 4H), J = 6.6 Hz), 3.23 (t, 4H, J
(
[
O A c ) ] ( c o m p l e x e s
1
o r 2 ) t o − C O O
13
1
2
6.6 Hz), 2.27 (s, 3H); C{ H} NMR (75 MHz, CDCl ): δ (ppm):
3
L(
−HC=N) (OH){−C(O)O}
→ (NO )/(OAc)] (complexes 3 or
3
2
159.2, 135.7, 132.7, 129.7, 129.1, 127.6, 126.3, 121.0, 59.6, 34.6, 20.3;
+
4) functionality. We considered all possible experimental
ES-MS: 435.1532 [M + H] ; Anal. Calcd. for C H N OS : C, 69.09;
2
5
26
2
2
1
5−18
factors
and reasoned that the formation of species 3 and 4
H, 6.03; N, 6.45; Found: C, 69.32; H, 5.98; N, 6.98.
Synthesis of UO (VI) Complex (1). A solution of UO (NO ) ·
comes into view as a result of further hydrolytic activity of 1
2
2
3 2
2
+
6H O (1.0 mmol) in acetonitrile (2 mL) was added to a solution of L
1.0 mmol) in acetonitrile (8 mL), and instantly the solution turned
2
and 2 in a reaction mixture with increasing UO2 solution.
This may have possibly proceeded as en route activity of
hydration water. Considering possible ways of oxidation in
uranyl chemistry, we propose the conversion of
(
red from yellow and was kept stirring overnight. The reaction mixture
was concentrated under reduced pressure, and the resulting viscous
mass was washed with diethyl ether; the obtained precipitate was
dried and dissolved in acetonitrile and kept for crystallization, and
after a few days red crystals were obtained suitable for X-ray analysis.
mp 180−184 °C, Anal. Calcd. for C H N O SU: C, 29.49; H, 2.33;
[
[
L(−HC=N)(OH)(−HC=O) → UO (NO ) /(OAc) ] to
2 3 2 2
L(
→ UO (NO )/(OAc)] resulted
2 3 2
−HC=N) (OH){−C(O)O}
1
7
16
3
10
from partially hydrolyzed species 1 or 2 which further got
hydrolyzed as only one of the anion bound to uranyl ion was
seen resulting in dinuclear complexes. This hydrolysis may
have further led to the formation of a reactive intermediate
species, where the uranyl bonded aldehyde group may
accommodate a positive charge followed by a charge balancing
N, 6.07; Found: C, 29.38; H, 2.28; N, 5.96; IR (KBr pellet): ν (in
−1
cm ) 3492, 3430, 3245, 3165, 3019, 2932, 2853, 2353, 1660, 1629,
1
528, 1437, 1382, 1281, 1193, 1130, 1037, 939, 876, 828, 745, 683,
563, 509.
Synthesis of UO
in identical manner as complex 1. A solution of UO (OAc) ·2H O
(VI) Complex (2). Complex 2 was synthesized
2
2
2
2
(
1.0 mmol) in acetonitrile (2 mL) was added to a solution of L (1.0
mmol) in acetonitrile (8 mL). Suitable yellow crystals obtained for X-
−OH group in place of the liberated anion. The positively
charged carbon of coordinated −CHO may be possibly further
stabilized by the −OH group bonded to the uranyl ion. This
situation may allow reduction of U(VI) species to U(V)
followed by hydration of the aldehyde group. The released
ray analysis. mp 185−189 °C, Anal. Calcd. for C H NO SU: C,
2
1
24
8
3
6.63; H, 3.51; N, 2.03; Found: C, 36.56; H, 3.49; N, 1.98; IR (KBr
−
1
pellet): ν (in cm ) 3787, 3616, 3163, 3004, 2944, 2357, 2292, 2252,
1826, 1635, 1441, 1376, 1038, 918, 748, 693, 552, 477, 434.
Synthesis of UO (VI) Complex (3). A solution of UO (NO ) ·
−
−
anion (NO or CH OCO ) might act as a base and abstract
2
2
3 2
3
3
+
6H
(
O (1.2 mmol) in acetonitrile (2 mL) was added to a solution of L
2
1.0 mmol) in acetonitrile (8 mL); instantly solution turned to red
from yellow and was kept stirring in the dark overnight. The reaction
mixture was concentrated to evaporate the solvent, resulting viscous
mass was washed with diethyl ether, and the obtained precipitate was
the H from the coordinated hydrated aldehyde site to give
donor carboxylate functionality and recurring uranyl(V)
species back to its original oxidation state U(VI) through
dimerization as seen by the formation of species 3 or 4.
E
DOI: 10.1021/acs.inorgchem.8b03622
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Inorganic Chemistry
Article
dried and dissolved in acetonitrile and kept for crystallization; after a
few days red crystals were obtained suitable for X-ray analysis. Yield:
113, 995−1015. (c) Andrews, M. B.; Cahill, C. L. Uranyl bearing
hybrid materials: synthesis, speciation, and solid-state structures.
Chem. Rev. 2013, 113, 1121−1136.
(3) (a) Gorden, A. E. V.; Xu, J.; Raymond, K. N.; Durbin, P.
Rational design of sequestering agents for plutonium and other
actinides. Chem. Rev. 2003, 103, 4207−4282. (b) Hancock, R. D.;
Martell, A. E. Ligand design for selective complexation of metal ions
in aqueous solution. Chem. Rev. 1989, 89, 1875−1914.
4
2
0%; mp >200 °C; Anal. Calcd. for C H N O S U : C, 31.59; H,
34 32 4 16 2 2
.49; N, 4.33; Found: C, 31.46; H, 2.41; N, 4.29; IR (KBr pellet): ν
−
1
(in cm ) 3434, 3061, 2927, 2362, 1659, 1555, 1482, 1375, 1318,
1
251, 1190, 1045, 927, 881, 798, 744, 682, 604, 563, 492.
Synthesis of UO (VI) Complex (4). A solution of UO (OAc) ·
2
2
2
2
H O (1.2 mmol) in acetonitrile (2 mL) was added to a solution of L
2
(1.0 mmol) in acetonitrile (8 mL), and a similar procedure as
(4) (a) Lan, T.; Wang, H.; Liao, J.; Yang, Y.; Chai, Z.; Liu, N.; Wang,
D. Dynamics of humic acid and its interaction with uranyl in the
presence of hydrophobic surface implicated by molecular dynamics
simulations. Environ. Sci. Technol. 2016, 50, 11121−11128. (b) Stew-
art, B. D.; Cismasu, A. C.; Williams, K. H.; Peyton, B. M.; Nico, P. S.
Reactivity of uranium and ferrous iron with natural iron oxy-
hydroxides. Environ. Sci. Technol. 2015, 49, 10357−10365. (c) Gorden,
A. E. V.; DeVore, M. A., II; Maynard, B. A. Coordination chemistry
with f-element complexes for an improved understanding of factors
that contribute to extraction Selectivity. Inorg. Chem. 2013, 52, 3445−
described above was adopted. The precipitate was dissolved in
acetonitrile, filtered, and kept for crystallization. After few days, yellow
crystals formed which were suitable for X-ray analysis. Yield: 37%; mp
>
200 °C; Anal. Calcd. for C H N O S U : C, 35.41; H, 3.13; N,
38 40 2 14 2 2
1
−
2.17; Found: C, 35.34; H, 3.06; N, 2.10; IR (KBr pellet): ν (in cm )
3430, 3057, 2925, 2865, 2362, 1658, 1553, 1484, 1374, 1251, 1190,
1048, 924, 819, 795, 743, 680, 602, 499, 426.
ASSOCIATED CONTENT
* Supporting Information
■
S
3
(
458.
5) (a) Knope, K. E.; Soderholm, L. Solution and solid-state
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.8b03622.
structural chemistry of actinide hydrates and their hydrolysis and
condensation products. Chem. Rev. 2013, 113, 944−994. (b) Qiu, J.;
Burns, P. C. Clusters of actinides with oxide, peroxide, or hydroxide
bridges. Chem. Rev. 2013, 113, 1097−1120.
Experimental details and spectroscopic data (PDF)
(
6) Altmaier, M.; Gaona, X.; Fanghan
aqueous actinide chemistry and thermodynamics. Chem. Rev. 2013,
13, 901−943. (b) Geckeis, H.; Lutzenkirchen, J.; Polly, R.; Rabung,
̈
el, T. Recent advances in
Accession Codes
CCDC 1889546−1889548 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
1
̈
T.; Schmidt, M. Mineral−water interface reactions of actinides. Chem.
Rev. 2013, 113, 1016−1062. (c) Knope, K. E.; Soderholm, L. Solution
and solid-state structural chemistry of actinide hydrates and their
hydrolysis and condensation products. Chem. Rev. 2013, 113, 944−
9
(
94.
7) (a) Zanonato, P. L.; Di Bernardo, P.; Bismondo, A.; Liu, G.;
Chen, X.; Rao, L. Hydrolysis of Uranium(VI) at variable temperatures
10−85 °C). J. Am. Chem. Soc. 2004, 126, 5515−5522. (b) Muller, K.;
AUTHOR INFORMATION
Corresponding Author
E-mail: jaideo@chemistry.iitd.ernet.in.
■
(
̈
Brendler, V.; Foerstendorf, H. Aqueous Uranium(VI) hydrolysis
species characterized by attenuated total reflection fourier-transform
infrared spectroscopy. Inorg. Chem. 2008, 47, 10127−10134.
*
ORCID
(c) Quach, D. L.; Wai, C. M.; Pasilis, S. P. Characterization of
Jai Deo Singh: 0000-0003-2987-3676
Notes
The authors declare no competing financial interest.
Uranyl(VI) nitrate complexes in a room temperature ionic liquid
using attenuated total reflection-fourier transform infrared spectrom-
etry. Inorg. Chem. 2010, 49, 8568−8572. (d) Quiles, F.; Nguyen-
̀
Trung, C.; Carteret, C.; Humbert, B. Hydrolysis of Uranyl(VI) in
Acidic and Basic Aqueous Solutions Using a Noncomplexing Organic
Base: A Multivariate Spectroscopic and Statistical Study. Inorg. Chem.
ACKNOWLEDGMENTS
■
We thank UGC, India, for financial support and FIST and
IITD for X-ray diffraction instrumentation. The authors are
grateful to Prof. Raymond J. Butcher (Howard University) and
Dr. Yoshiaki Tanabe (Tokyo University) for determining the
crystal structure of the complexes. We also acknowledge Prof.
Namakkal Govind Ramesh (IITD) for fruitful discussion.
2
011, 50, 2811−2823. (e) Drobot, B.; Bauer, A.; Steudtner, R.;
Tsushima, S.; Bok, F.; Patzschke, M.; Raff, J.; Brendler, V. Speciation
studies of metals in trace concentrations: the mononuclear uranyl(VI)
hydroxo complexes. Anal. Chem. 2016, 88, 3548−3555. (f) Bader, M.;
Rossberg, A.; Steudtner, R.; Drobot, B.; Großmann, K.; Schmidt, M.;
Musat, N.; Stumpf, T.; Ikeda-Ohno, A.; Cherkouk, A. Impact of
haloarchaea on speciation of uranium-a multispectroscopic approach.
Environ. Sci. Technol. 2018, 52, 12895−12904.
REFERENCES
■
(
1) (a) Albrecht-Schmitt, T. E. Actinide chemistry at the extreme.
(8) (a) Bart, S. C.; Anthon, C.; Heinemann, F. W.; Bill, E.; Edelstein,
N. M.; Meyer, K. Carbon dioxide activation with sterically pressured
mid- and high-valent uranium complexes. J. Am. Chem. Soc. 2008, 130,
12536−12546. (b) Bart, S. C.; Heinemann, F. W.; Anthon, C.;
Hauser, C.; Meyer, K. A New Tripodal ligand system with steric and
electronic modularity for uranium coordination chemistry. Inorg.
Chem. 2009, 48, 9419−9426. (c) Pattenaude, S. A.; Coughlin, E. J.;
Collins, T. S.; Zeller, M.; Bart, S. C. Expanding the library of uranyl
amide derivatives: new complexes featuring the tert-butyldimethylsi-
lylamide ligand. Inorg. Chem. 2018, 57, 4543−4549.
(9) (a) Matson, E. M.; Fanwick, P. E.; Bart, S. C. Formation of
trivalent U−C, U−N, and U−S bonds and their reactivity toward
carbon dioxide and acetone. Organometallics 2011, 30, 5753−5762.
(b) Matson, E. M.; Breshears, A. T.; Kiernicki, J. J.; Newell, B. S.;
Fanwick, P. E.; Shores, M. P.; Walensky, J. R.; Bart, S. C. Trivalent
Uranium phenylchalcogenide complexes: exploring the bonding and
Inorg. Chem. 2019, 58, 1721−1723. (b) Abney, C. W.; Mayes, R. T.;
Saito, T.; Dai, S. Materials for the recovery of uranium from seawater.
Chem. Rev. 2017, 117, 13935−14013. (c) Beltrami, D.; Cote, G.;
Mokhtari, H.; Courtaud, B.; Moyer, B. A.; Chagnes, A. Recovery of
uranium from wet phosphoric acid by solvent extraction processes.
Chem. Rev. 2014, 114, 12002−12023. (d) Mayer, K.; Wallenius, M.;
Varga, Z. Nuclear forensic science: correlating measurable material
parameters to the history of nuclear material. Chem. Rev. 2013, 113,
8
84−900. (e) Burns, P. C.; Ewing, R. C.; Navrotsky, A. Nuclear fuel
in a reactor accident. Science 2012, 335, 1184−1188. (f) Awwal, M.
A.; Carswell, D. J. Aqueous repossessing of reactor fuel. Chem. Rev.
1
(
2
966, 66, 279−295.
2) (a) Nitsche, H. Introduction to nuclear chemistry. Chem. Rev.
013, 113, 855−857. (b) Walther, A.; Denecke, M. A. Actinide
colloids and particles of environmental concern. Chem. Rev. 2013,
F
DOI: 10.1021/acs.inorgchem.8b03622
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
reactivity with CS in the Tp* UEPh series (E = O, S, Se, Te). Inorg.
of μ -oxido/hydroxido bridged trinuclearUranyl(VI) complexes with
2
2
3
Chem. 2014, 53, 12977−12985. (c) Coughlin, E. J.; Qiao, Y.;
Lapsheva, E.; Zeller, M.; Schelter, E. J.; Bart, S. C. Uranyl
functionalization mediated by redox-active ligands: Generation of
O−C bonds via acylation. J. Am. Chem. Soc. 2019, 141, 1016−1026.
tridentate schiff-base ligands. Inorg. Chem. 2017, 56, 4057−4064.
(e) Chaudhry, M. T.; Lelj, F.; MacLachlan, M. J. Expanded
campestarene hosts for tetra- and dinuclearuranyl(VI) complexes.
Chem. Commun. 2018, 54, 11869−11872.
(10) (a) Khan, S.; Singh, J. D.; Mahajan, R. K.; Sood, P. Synthesis of
(17) (a) Alexander, V. Design and synthesis of macrocyclic ligands
and their complexes of lanthanides and actinides. Chem. Rev. 1995,
95, 273−342. (b) Jones, M. B.; Gaunt, A. J. Recent developments in
synthesis and structural chemistry of nonaqueous actinide complexes.
Chem. Rev. 2013, 113, 1137−1198. (c) Bharara, M. S.; Heflin, K.;
Tonks, S.; Strawbridge, K. L.; Gorden, A. E. V. Hydroxy- and alkoxy-
bridged dinuclearuranyl−schiff base complexes: hydrolysis, trans-
amination and extraction studies. Dalton Trans. 2008, 2966−2973.
(18) For instance, a number of organic donor bases bearing usually
O and N donor functionalities with acyclic and cyclic structures
including Schiff bases and their complexes with hydrated uranyl salts
in organic solvents are known. However influence of en route
hydration water on uranyl coordination as a logical source has never
lariat organochalcogenoethers based on azacalix[3]arenes for the
2
+
potentiometric detection of [UO2] ions. Tetrahedron Lett. 2007, 48,
605−3608. (b) Kumar, A.; Singh, J. D. An Organoselenium-Based
Highly Sensitive and Selective Fluorescent “Turn-On” Probe for the
3
2+
Hg Ion. Inorg. Chem. 2012, 51, 772−774. (c) Neeru; Yadav, D.;
Tiwari, G.; Singh, J. D.; Butcher, R. J. Responsive Nature of 1,2,4,5-
Tetrakis(2-pyridylthiomethyl)benzene Toward Group 12 Metal
Nitrates: Activity of Coordinated Nitrate in Metal Complexes.
Inorg. Chem. 2014, 53, 5887−5889.
(11) (a) Sun, X.; Kolling, D. R. J.; Mazagri, H.; Karawan, B.; Pierron,
C. Investigation of charge-transfer absorptions in the uranyl
UO22 (VI) ion and related chemical reduction of UO2 (VI) to
+
2+
16,17
+
been claimed.
UO (V) by UV−Vis and electron paramagnetic resonance spectros-
2
copies. Inorg. Chim. Acta 2015, 435, 117−124. (b) Borisova, N. E.;
Reshetova, M. D.; Ustynyuk, Y. A. Metal-Free Methods in the
Synthesis of Macrocyclic Schiff Bases. Chem. Rev. 2007, 107, 46−79.
(
c) Jia, Y.; Li, J. Molecular Assembly of Schiff Base Interactions:
Construction and Application. Chem. Rev. 2015, 115, 1597−162.
d) Bharara, M. S.; Tonks, S.; Gorden, A. E. V. Uranyl stabilized
Schiff base complex. Chem. Commun. 2007, 4006−4008.
12) (a) Odoh, S. O.; Bondarevsky, G. D.; Karpus, J.; Cui, Q.; He,
(
(
2
+
C.; Spezia, R.; Gagliardi, L. UO2 uptake by proteins: understanding
the binding features of the super uranyl binding protein and design of
a protein with higher affinity. J. Am. Chem. Soc. 2014, 136, 17484−
1
7494. (b) Zhou, W.; Saran, R.; Liu, J. Metal sensing by DNA. Chem.
Rev. 2017, 117, 8272−8325.
13) (a) Vukovic, S.; Hay, B. P.; Bryantsev, V. S. Predicting stability
(
constants for uranyl complexes using density functional theory. Inorg.
Chem. 2015, 54, 3995−4001. (b) Odoh, S. O.; Schreckenbach, G.
−
−
2−
DFT study of uranyl peroxo complexes with H O, F OH CO and
2
3
−
NO . Inorg. Chem. 2013, 52, 5590−5602. (c) Clark, D. L.; Hobart,
D. E.; Neu, M. P. Actinide carbonate complexes and their importance
3
in actinide environmental chemistry. Chem. Rev. 1995, 95, 25−48.
(d) Dang, D. H.; Novotnik, B.; Wang, W.; Georg, R. B.; Evans, R. D.
Uranium isotope fractionation during adsorption, (Co) precipitation,
and biotic reduction. Environ. Sci. Technol. 2016, 50, 12695−12704.
(
14) (a) McGrail, B. T.; Pianowski, L. S.; Burns, P. C.
Photochemical water oxidation and origin of nonaqueous uranyl
peroxide complexes. J. Am. Chem. Soc. 2014, 136, 4797−4800.
(b) Thangavelu, S. G.; Cahill, C. L. Uranyl-promoted peroxide
generation: synthesis and characterization of three uranylperoxo
[
(
(UO ) (O )] complexes. Inorg. Chem. 2015, 54, 4208−4221.
2
2
2
c) Kirkegaard, M. C.; Miskowiec, A.; Ambrogio, M. W.; Anderson,
B. B. Evidence of a nonphotochemical mechanism for the solid-state
formation of uranyl peroxide. Inorg. Chem. 2018, 57, 5711−5715.
(15) (a) Chatelain, L.; White, S.; Scopelliti, R.; Mazzanti, M.
Isolation of a star shaped uranium(V/VI) cluster from the anaerobic
photochemical reduction of uranyl(VI). Angew. Chem., Int. Ed. 2016,
5
5, 14325−14329. (b) Faizova, R.; Scopelliti, R.; Chauvin, A.-S.;
Mazzanti, M. Synthesis and characterization of a water stable
uranyl(V) complex. J. Am. Chem. Soc. 2018, 140, 13554−13557.
(16) (a) Rose, D.; Chang, Y.-D.; Chen, Q.; Zubieta, J. Reactions of
Uranylthiolate complexes with molecular oxygen: synthesis and
crystal and molecular structures of the uranylthiolateperoxo species.
́
Inorg. Chem. 1994, 33, 5167−5168. (b) Thuery, P.; Villiers, C.; Jaud,
J.; Ephritikhine, M.; Masci, B. Uranyl-based metallamacrocycles: tri-
and tetranuclear complexes with (2R3R4S5S)-tetrahydrofurantetra-
carboxylic acid. J. Am. Chem. Soc. 2004, 126, 6838−6839. (c) Vaughn,
A. E.; Bassil, D. B.; Barnes, C. L.; Tucker, S. A.; Duval, P. B.
Contrasting solvent and capping ligand effects directing the
photochemistry of Uranyl(VI) Schiff base complexes. J. Am. Chem.
Soc. 2006, 128, 10656−10657. (d) Yoshimura, T.; Nakaguchi, M.;
Morimoto, K. Synthesis, structures, and proton self-exchange reaction
G
DOI: 10.1021/acs.inorgchem.8b03622
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