A uranium(VI) complex with a tetradentate N1,N4-disalicyliden-S-ethylisothiosemicarbazone ligand

Article abstract of DOI:10.1016/j.poly.2017.02.044

The Schiff base ligand of bis-(2-hydroxybenzaldehyde)-S-ethylisothiosemicarbazone and its U(VI) complex have been prepared. Their structures were fully characterized by elemental analysis, FT-IR, molar conductivity, UV–Vis and ¹H NMR methods. X-ray diffraction has been used to determine the molecular structure of the uranium complex. The Schiff base complex was found to be pentagonal bipyramidal. The N₂O₂ donor ligand was coordinated to the metal center as a tetradentate binegative agent. Computational studies were performed using the DFT method to estimate the structural preferences in tridentate and tetradentate isothiosemicarbazones. Geometry optimization and natural bond orbital analyses of the UO₂(II) complex have been further discussed in detail. The thermal stabilities of the ligand and its uranium complex have also been determined by thermogravimetric analysis (TGA).

Full text of DOI:10.1016/j.poly.2017.02.044

Accepted Manuscript
1
4
A uranium(VI) complex with a tetradentate N ,N -disalicyliden-S-ethylisothio-
semicarbazone ligand
Alireza Akbari, Ahad Fasihizad, Mehdi Ahmadi, Barbara Machura
PII:
S0277-5387(17)30166-3
DOI:
http://dx.doi.org/10.1016/j.poly.2017.02.044
POLY 12511
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
20 November 2016
13 February 2017
14 February 2017
Please cite this article as: A. Akbari, A. Fasihizad, M. Ahmadi, B. Machura, A uranium(VI) complex with a
1
4
tetradentate N ,N -disalicyliden-S-ethylisothiosemicarbazone ligand, Polyhedron (2017), doi: http://dx.doi.org/
0.1016/j.poly.2017.02.044
1
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

1
4
A
uranium(VI)
complex
with
a
tetradentate
N ,N -disalicyliden-S-
ethylisothiosemicarbazone ligand
a
a
a,*
b,*
Alireza Akbari , Ahad Fasihizad , Mehdi Ahmadi , Barbara Machura
a
Department of Chemistry, Payame Noor University (PNU), 19395-4697, Iran
b
Department of Crystallography, Institute of Chemistry, University of Silesia, ul. Szkolna 9,
4
0-006 Katowice, Poland
a
Dr. Mehdi Ahmadi
Department of Chemistry, Payame Noor University (PNU), 19395-4697, Iran
Tehran
Iran
Tel/Fax: +98 (513) 4693258
E-mail address: mehdieahmadi@ymail.com
b
Professor Barbara Machura
Department of Crystallography
University of Silesia
Katowice
Poland
Tel.: +48322582441; fax: +48322599978.
E-mail addresses: basia@ich.us.edu.pl
1

Abstract:
The Schiff base ligand of bis-(2-hydroxybenzaldehyde)-S-ethylisothiosemicarbazone and its
U(VI) complex have been prepared. Their structures were fully characterized by elemental
1
analysis, FT-IR, molar conductivity, UV-Vis and H NMR methods. X-ray diffraction has
been used to determine the molecular structure of the uranium complex. The Schiff base
complex was found to be pentagonal bipyramidal. The N O donor ligand was coordinated to
2
2
the metal center as a tetradentate binegative agent. Computational studies were performed
using the DFT method to estimate the structural preferences in tridentate and tetradentate
isothiosemicarbazones. Geometry optimization and natural bond orbital analyses of the
UO (II) complex have been further discussed in detail. The thermal stabilities of the ligand
2
and its uranium complex have also been determined by thermogravimetric analysis (TGA).
Keyword: isothiosemicarbazone, uranium, X-ray, DFT, TGA
1
. Introduction
Isothiosemicarbazones are in the center of research interests, not only for the selective
separations of ions [1] but also for their biological properties, which generally arise from
their strong chelating ability with metal ions [2,3]. Isothiosemicarbazone compounds are
sulfur containing Schiff base materials that have been used for designing tailor-made
polydentate ligands [4].
Isothiosemicarbazides have two NH groups. Among them, only the hydrazinic amine group
2
can simply participate in a Schiff base reaction. A metal center with a definite electronic state
is needed to dictate the condensation between the thioamide amine group of
isothiosemicarbazones and the carbonyl group of aldehyde or ketone compounds. In this way,
their interaction is affected by a suitable orientation as a result of their coordination. By
means of the metal template process, multidentate ligands can be obtained, the synthesis of
which is totally impossible under other conditions [5,6].
It is also documented that the template reaction between aldehyde or ketone compounds and
S-alkylatedisothiosemicarbazone in alcohol in the presence of the metal ions of V(IV),
Mn(II), Fe(III), Ni(II), Zn(II), MoO (II) and UO (II) can lead to formation of metal
2
2
complexes containing a tetradentate ligand in high yield [7,8].
By using 2-hydroxobenzaldehyde, an asymmetric N O donor ligand, comparable with Salen,
2
2
can be obtained. Having planar or pseudo-planar conformations of such ligands may enable
complexes with the central atom at the center of a charge-transfer system to be formed. These
2

complexes are suitable for successful applications due to their non-linear optical properties
and for use in the field of optoelectronic technologies [9,10].
Uranyl complexes are interesting to researchers because of their high chemical stability, high
coordination numbers and low radiological hazard [11]. They have received considerable
attention due to their promising luminescent and magnetic properties. Some uranyl
complexes have also been used as catalysts in the oxidation of alcohols to ketones and in acyl
transfer reactions [12].
The first uranium complex of isothiosemicarbazone was investigated structurally by Leovac
et al. [13]. From that time until now, many uranium(VI) complexes of isothiosemicarbazones
have been synthesized and their structures have been studied by means of spectral methods
and X-ray diffraction analysis [14-21]. To the best of our knowledge, however, other analyses
like DFT calculations have been rather rarely performed for these systems.
Herein, we first synthesized a reported Ni(II) complex of the tetradentate ligand bis-(2-
hydroxybenzaldehyde)-S-ethylisothiosemicarbazone by the template process [22]. The
tetradentate ligand can be extracted by adding hydrochloric acid. The uranium dioxide
complex of the tetradentate ligand was then prepared and characterized by the prevailing
1
methods of FT-IR, UV-Vis, H NMR as well as by single crystal X-ray diffraction. The
geometrical parameters, frequency analyses and NBO calculations in the ground state have
been calculated by DFT calculations. An additional study was done to examine the thermal
stability by TGA.
2
2
. Experimental
.1 Reagents and physical measurements
All chemicals were of analytical reagent grade and they were used without further
-1
purification. FT-IR spectra were measured as KBr pellets in the 400-4000 cm region on a
1
FT-IR 8400-SHIMADZU spectrophotometer. The H NMR spectra were recorded in DMSO-
d6 on a Bruker BRX 300 AVANCE spectrometer. The UV-Vis spectra of the compounds
-5
-3
were run in methanol (2 × 10 M) and DMF (10 M) solutions on a SHIMADZU model
2
550 UV-Vis spectrophotometer. C, H and N analyses were carried out using a Thermo
-3
Finnigan Flash Elemental Analyzer 1112EA instrument. The molar conductance of 10 M
solutions of the ligands and the metal complexes in DMF were measured at room temperature
using a Metrohm 712 conductometer. Thermogravimetric analyses (TGA) were carried out
using a TG-50 SHIMADZU under an argon atmosphere over the temperature range 20-800
°
C at a heating rate of 10 °C/min.
3

2
. 2. X-ray crystal structure determination
The X-ray intensity data of the uranium(VI) complex were collected on a Gemini A Ultra
Oxford Diffraction four-circle kappa geometry diffractometer with Atlas CCD detector
graphite monochromatic MoK radiation ( = 0.71073 Å) at 293.0(2) K. The unit cell

determination and data integration were carried out using the CrysAlis package of Oxford
Diffraction [23]. Intensity data were corrected for Lorentz and polarization effects. The
absorption correction was introduced by the SCALE3 ABSPACK scaling algorithm [23]. The
structure was solved by the Paterson method using SHELXS-97 and refined by full matrix
2
least-squares on F with SHELXL-97, using anisotropic displacement parameters for the non-
hydrogen atoms [24]. The hydrogen atoms were treated as “riding” on their parent carbon
atoms and were assigned isotropic temperature factors equal to 1.2 (aromatic) and 1.5
(methyl) times the value of equivalent temperature factor of the parent atom.
Insert Table 1
2
. 3. Theoretical calculations
The geometry of the compounds was fully optimized with density functional theory (DFT).
All calculations were performed using the B3LYP exchange correlation functional [25]. The
calculations were done using the 6-311G**(d,p) [26] basis set for the H, C, N, O and S atoms
and the Lanl2dz [27] basis set for the metal center in gas and solution phases with the
GAUSSIAN 98 program package [28].
The U(VI) complex and the H L ligands, both Z and E isomers and all the deprotonated
2
structures, were fully optimized. No symmetry constraints were applied in the calculations.
The optimized structures have been used for the frequency calculations. The lack of negative
number of the frequencies showed that the structures were fully optimized. The ground state
energies of the Z and E isomers were also calculated in methanol solution using the CPCM
model (conductor-like polarizable continuum model) [29]. Analysis of the Natural Bond
Orbital (NBO) was done with the NBO-code included in Gaussian 98 [30].
1
2
. 4. Synthesis of 2-hydroxybenzaldehyde S-ethylisothiosemicarbazone H L
2
This compound was synthesized by following the literature procedure [5]. 2-
Hydroxybenzaldehyde (1.22 g, 10 mmol) and S-ethylisothiosemicarbazide (2.47 g, 10 mmol)
were refluxed for 1 h. The reaction was completed by the addition of an equivalent amount of
Na CO (1.06 g, 10 mmol). A yellow precipitate was obtained when the reaction solution was
2
3
4

left to stand overnight. The precipitate was separated and washed several times with cold
ethanol and dried in vacuo over silica gel.
-1
Yield: 1.9 g, 85%. M.p.: 155 °C. Anal. Calc. for C H N OS (223.29 g mol ): C, 53.79; H,
10
13
3
-1
5
.87; N, 18.82. Found (%): C, 35.45; H, 5.72; N, 18.36. FT-IR (KBr, cm ): ν(OH) 3400;
ν (NH ) 3201; ν (NH ) 3068; ν(CH) 2972; ν(C=N) + ν(C=C) 1589, 1520; ν(C=C) 1469,
as
2
as
2
-1
1
450; ν(C-O) 1115; ν(N-N) 1056; δ (C-H) 756. UV-Vis (methanol, λmax, nm (log ε, L mol
opb
-1
-3
-1
-1
cm )): 213 (4.77), 308 (4.49), 346 (4.56). Molar conductivity (1×10 mol L , MeOH, Ω
2
-1
cm mol ): 17.
1
4
2
. 5. Synthesis of (S-ethyl-N ,N -bis-(2-hydroxybenzaldehyde)-isothiosemicarbazide-
N,N',O,O')-nickel(II)
The nickel complex was prepared according to the literature [22]. An ethanolic solution (5
mL) of 2-hydroxybenzaldehyde S-ethylisothiosemicarbazone (0.223 g, 1 mmol) and 2-
hydroxybenzaldehyde (0.122 g, 1 mmol) were mixed for 30 min in the presence of KOH
(
0.122 g, 2 mmol). To the mixture, NiCl .6H O (0.237 g, 1 mmol) was added as a solid. A
2 2
red solution was immediately obtained. The reaction solution was stirred for 30 min at room
temperature. A red crystalline precipitate was obtained which was separated and washed
several times with cold ethanol and dried in vacuo over silica gel.
-1
Yield: 0.24 g, 63%. M.p.: 236 °C. Anal. Calc. for C H N NiO S (384.08 g mol ): C, 53.16;
17
15
3
2
-1
H, 3.94; N, 10.94. Found (%): C, 52.46; H, 3.72; N, 10.71. FT-IR (KBr, cm ): ν(CH) 2923;
ν(C=N) + ν(C=C) 1600, 1573,1527; ν(C=C) 1427; ν(C-O) 1288; ν(N-N) 1026; δ (C-H) 763.
opb
-1
-1
UV-Vis (methanol, λmax, nm (log ε, L mol cm )): 225 (5.02), 245 (4.60), 300 (3.99), 393
-3
-1
-1
2
-1
(
4.38). Molar conductivity (1×10 mol L , MeOH, Ω cm mol ): 24.
2
2
. 6. Synthesis of bis-(2-hydroxybenzaldehyde)-S-ethylisothiosemicarbazone H L
2
1
4
To a 10 mL chloroformic solution of (S-ethyl-N ,N -bis-(2-hydroxybenzaldehyde)-
isothiosemicarbazide-N,N',O,O')-nickel(II) (0.384 g, 1 mmol), hydrochloric acid 32% (0.22
g, 2 mmol) was added gradually until the red color of the solution became light-green. Water
(50 mL) was added to the solution and after vigorous stirring, the organic layer was
separated. This was repeated 3 times to ensure the removal of nickel(II) chloride from the
organic layer. The chloroform was evaporated and the remaining yellow precipitate was
separated and washed several times with cold ethanol and dried in vacuo over silica gel.
-1
Yield: 0.294 g, 90%. M.p.: 163 °C. Anal. Calc. for C H N O S (327.40 g mol ): C, 62.36;
17
17
3
2
-1
H, 5.23; N, 12.83. Found (%): C, 61.83; H, 4.98; N, 12.74. FT-IR (KBr, cm ): ν(OH)
7
1
3
351(m); ν(CH)-aromatic 3012-3063(w); ν(CH)-Et 2854-2966(w); ν(C =N ) + ν(C=C)
5

8
2
1
1
613(m); ν(C=C) + δ (OH) 1573(m); ν(C=C) 1485(vs); ν(C =N ) + ν(C=C) 1454(s); ν(CO)
ipb
3
2
2
253(m); ν(N=C-N ) + ν(C O ) 1211(w); δoopb(OH) 812(w); δoopb(CH)-aromatic 752(m);
1
ν(CSC) 650(w). H NMR (300 MHz, DMSO-d ) δ, ppm: 10.1 (s, 2H; exchanges with D O),
6
2
8
.3 (s, 1H, C7H), 8.2 (s, 1H, C8H), 7.35 (d, 2H, C5), 7 (dd, 2H, C2, C14), 6.6 (d, 4H, C3, C4,
-1
-
C12, C13), 1.5 (s, 2H, C16), 1.1 (t, 3H, C17). UV-Vis (methanol, λmax, nm (log ε, L mol cm
1
)): 213 (5.09), 238 (4.73), 284 (4.74), 335 (4.54), 387 (4.30), 408 (4.27). Molar conductivity
-3
-1
-1
2
-1
(
1×10 mol L , MeOH, Ω cm mol ): 21.
1
4
2
.
7. Synthesis of methanol-(S-ethyl-N ,N -bis-(2-hydroxybenzaldehyde)-
isothiosemicarbazide-N,N',O,O')-dioxidouranium(VI)
A methanolic solution (5 mL) of bis-(2-hydroxybenzaldehyde)-S-ethylisothiosemicarbazone
(0.327 g, 1 mmol) was gradually added to a methanolic solution (5 mL) of UO (OAC) .2H O
2 2 2
(0.424 g, 1 mmol). A red solution was obtained. The reaction solution was stirred for 30 min
at 40 °C. Crystals suitable for X-ray analysis were obtained by slow evaporation of the
maternal solution in the fridge after one week. They were separated and washed several times
with cold methanol and dried in vacuo over silica gel.
-1
Yield: 0.53 g, 85%. M.p. 193 °C. Anal. Calc. for C H N O SU (627.45 g mol ): C, 34.46;
18
19
3
5
-1
H, 3.05; N, 6.70. Found (%): C, 35.04; H, 3.12; N, 6.87. IR (KBr) cm : ν(OH)-alcohol
7
1
3
1
409(ms); ν(CH)-aromatic 3012-3063(w); ν(CH)-Et 2854-2966(w); ν(C =N ) + ν(C=C)
8
2
3
589(s); ν(C=C) 1550(vs); ν(C =N ) + ν(C=C) 1435(s); ν(CO) 1250(m); ν(N=C-N ) +
2
2
ν(C O ) 1203(m); ν (trans-UO ) 910(s); ν (trans-UO ) 870(m); δoopb(CH)-aromatic
asy
2
sy
2
1
7
56(m); ν(CSC) 671(w); ν(MO) 586(m); ν(MN) 439(m). H NMR (300 MHz, DMSO-d ) δ,
6
ppm: 9.3 (s, H, OHalcohol; exchanges with D O), 8.35 (s, 1H, C7H), 8.25 (s, 1H, C8H), 7.4-6.1
2
(m, 8H, Ar-CH), 2.75 (s, 3H, C18), 1.5 (s, 2H, C16), 1.4 (t, 3H, C17). UV/Vis (ethanol, λmax,
-1
-1
nm (log ε, L mol cm )): 222 (4.7), 245 (4.62), 311 (4.53), 394 (4.20), 449 (4.06). Molar
-3
-1
2
conductivity (1.0×10 M, MeOH, Ω cm mol): 23.
3
. Results and discussion
Condensation of 2-hydroxobenzaldehyde with S-ethyl-isothiosemicarbazide gave the Schiff
1
1
base ligand H L . The template reaction of H L , 2-hydroxobenzaldehyde and NiCl .6H O in
2
2
2
2
alkaline solution of MeOH resulted the Ni(II) complex. Hydrochloric acid was added to the
chloroformic solution of the nickel complex. Thus, NiCl was extracted and the remaining
2
2
2
yellow precipitate corresponding to H L was prepared. H L was reacted with UO (OAC)
2
2
2
2
in methanol and a new uranium complex was synthesized.
6

The ligands and the complexes are found to be soluble in common organic solvents, like
MeOH, DMF and DMSO, but are insoluble in H O. The elemental analyses confirm that the
2
2
2
complexes are mononuclear and may be formulated as [Ni(L )] and [UO (L )MeOH]. Molar
2
-3
conductivity data in 10 M DMF solutions for the ligands and complexes indicate that they
are non-electrolytes [31,32].
3
.1. General optimization and NBO calculations
The crystal structure of the uranium(VI) complex has been used as the initial geometry for
the optimization. Some of important bond lengths and bond angles are given in Table 3, in
which the calculated values are in good agreement with the experiment values. A small
difference is seen in the bond distances and bond angles. This may be due to the fact that the
DFT calculations were performed in the gas phase, whereas the X-ray crystal diffraction was
performed in the solid state.
The natural charges from the natural population analyses for the donor atoms and metal atom
were calculated in the gas phase. The calculated electronic configurations confirmed electron
donation from the donor atoms towards the metal ion. Also, the calculated formal charge on
the central ion in the complex was near to +2, quite smaller as compared to the formal
oxidation state of the metal (+6), and the net charges on the O1, O2 and O3, O4 atoms are
significantly smaller than -2 and -1, respectively.
According to the NBO calculations for the U=O trans bonds of the U(VI) complex, there are
four σ and π bonding orbitals and four σ* and π* antibonding orbitals. The σ bonding orbitals
of the {U=O} bonds are polarized mainly on the O1 and O2 atoms (respectively 76.02 and
7
7.75 %). The metal center and oxygen atoms use 5d and 4f orbitals and 2s and 2p valence
orbitals for σ bonds, respectively. The π bonding electrons are also polarized towards the O1
and O2 atoms by 78.30 and 78.30% respectively. In the formation of the U=O π bond, the
metal and oxygen atoms use 5d and 4f, and 2p orbitals respectively. Accordingly, the σ* and
π* antibonding orbitals are polarized toward the central metal ion.
1
2
3
. 2. Comparison of the structure stability in different forms of the H L and H L
2 2
ligands
A DFT study was performed to evaluate the conformational preference in the tridentate
1
2
(
H L ) and tetradentate (H L ) ligands. The optimizations have performed for both Z and E
2 2
isomers and their various deprotonated structures. For all the structures, vibrational frequency
calculations have been done as a check for the accuracy of the optimizations.
7

In the solid state, isothiosemicarbazones crystallize in either the Z or E configuration, while
the simultaneous presence of both the Z and E configurations in the solution phase were
reported [33,34]. In the E isomer, the N1 and N3 atoms lie in cis positions, while in the Z
1
isomer they are in trans positions with respect to each other [33]. The E structure of H L is
2
-1
more stable than the Z form by 9 and 4 K cal mol in the gas and solution phases
2
respectively. Also, the stability of the Z structure of H L is significantly higher compared to
2
-1
the E form, by 7 and 4 K cal mol in the gas and solution phases respectively.
1
In the E configuration of H L , the S atom is generally in a trans position with respect to the
2
atom N1. Thus, the N1 and N3 atoms are placed in positions suitable for intramolecular
N1...H-N3 hydrogen bonding. The hydrogen bonding interaction is thus preferred to the 1,4
N...S contact, which would take places in the Z conformation [34].
2
In the Z form of H L , the S and N1 atoms are favourably oriented to give an intramolecular
2
through-space 1,4S...N interaction. Also, intramolecular hydrogen bonding within the
molecule cannot occur. Thus, the cis form becomes more stable than the trans form.
2
Adoption of the cis form by H L also forces the phenyl rings far away from each other [34].
2
1
2
For the deprotonated structures of the cis and trans isomers of H L and H L , the di-
2
2
deprotonated species have higher energies than the corresponding mono-deprotonated
species. This shows that the probability of simultaneous deprotonation of the NH and OH
2
1
2
groups in H L and O1H and O2H groups in H L in the solution is low. Another conclusion
2
2
1
indicates that deprotonation in the E form of the H L firstly occurs at the OH group and then
2
2
at the NH group. Also, deprotonation in the Z form of H L firstly occurs at the O1H group
2
2
and then at the O2H group
3
. 3. Infrared spectroscopy
1
In the FT-IR spectrum of H L , the asymmetric and symmetric stretching vibrations of the
2
-1
-1
NH group are observed at 3201 and 3068 cm as sharp bands. The strong band at 3400 cm
2
-1
is characteristic of ν(O-H). The peak at 756 cm is attributed to the out of plane bending
-1
vibration of the aromatic ring. The peaks at 1589 and 1529 cm are due to the combination of
-1
ν(C=N) and ν(C=C). The stretching vibration of the C-O bond is observed at 115 cm [31].
The FT-IR spectrum of the Ni(II) complex does not show ν (NH ) and ν (NH ), showing the
as
2
s
2
template reaction had been performed successfully. Stretching bands due to ν(C=N) + ν(C=C)
in the spectrum of the Ni(II) complex are recorded at lower frequencies than the
1
corresponding bands of H L .
2
8

Useful information related to the U(VI) complex formation can be obtained by a comparison
between the experimental and theoretical FT-IR spectra. Experimental and theoretical
vibrational frequency values of the tetradentate ligand and its U(VI) complex are tabulated in
Table 2. The tetradentate ligand and its U(VI) complex belong to the C1 point group and
because of their low symmetry, they show a lot of peaks in the infrared spectra. The
calculated frequencies were scaled by the suitable scale factor of 0.968 [32].
2
One of the significant differences seen between the IR spectra of H L and its U(VI) complex
2
-1
is due to the presence of more strong bands at 910 and 870 cm for the metal complex. They
are due to ν (trans-UO ) and ν (trans-UO ). Theoretical values are disclosed at 901 and
asy
2
sy
2
-
1
-1
-1
8
1
61 cm . The ligand band at 1253 cm (calculated at 1263 cm ) assigned to ν(C-O), shifts to
-
1
-1
250 cm (calculated at 1245 cm ) on complexation, confirming involvement of the oxygen
atoms in the complex formation [8]. The infrared spectrum of the tetradentate ligand shows a
-1
-1
ν(OH) band at 3351 cm while in the calculation it is determined at 3431 cm . The absence
of this band in the infrared spectrum of the U(VI) metal complex indicates deprotonation of
-1
the hydroxyl group during the chelation. The sharp intense bands at 1613 and 1485 cm in
2
7
1
8
2
the spectrum of H L can be assigned to ν(C =N ) + ν(C=C) and ν(C =N ) + ν(C=C) [7]. A
2
downward shift in ν(C=N) is observed upon coordination, indicating that the nitrogen atoms
of the azomethine groups are involved in the coordination. The uranium complex shows a
-1
-1
broad band at 3409 cm in the experiment and at 3531 cm in the calculation, which can be
assigned to ν(OH) of the coordinated solvent molecule. The new bands present at 586 and
-1
4
39 cm are due to metal-oxygen and metal-nitrogen stretching vibrations. The calculations
-1
disclose these bands at 559 and 411 cm .
Insert Table 2.
3
. 4. UV-Vis study
1
2
The electronic absorption spectra of H L and H L and their Ni(II) and U(VI) complexes in
2
2
MeOH solution have been recorded in the region 800-200 nm. The electronic spectrum of
1
H L displays two absorption bands at 213 and 308 nm. They can be attributed to π→π*
2
transitions in the benzene ring and azomethine (C=N) group. Another band at 346 nm is most
probably due to the n→π* transitions of the azomethine and thioamide groups [9].
2
1
The electronic spectrum of H L has some extra bands in comparison with H L . They can be
2
2
due to the extra benzene ring and the formation of a new azometinic C=N moiety. Three
2
intense bands appeared at 213, 238 and 284 nm in the UV-Vis spectrum of H L , which are
2
assignable to π→π* transitions of the benzene rings. These bands show a red shift in the
spectra of the complexes [8]. The n→π* transitions of the azomethine and thioamide moieties
9

are displayed at 335, 387 and 408 nm. Three n→π* transitions within the ligands are omitted
in the spectra of the complexes and only one band for the n→π* transition is observed at 393
and 394 nm in the UV-Vis spectra of the Ni(II) and U(VI) complexes, respectively [10].
By comparison of the electronic spectra of the ligands with their Ni(II) and U(VI) complexes,
it is clearly obvious that some bands show blue or red shifts which can be considered as
evidence for the complex formation. Additionally, new bands are observed in the spectra of
the complexes corresponding to certain ligand to metal and metal to ligand charge transitions.
1
3
. 5. H NMR spectroscopy
1
Scheme 1 can be applied for the assignment of the proton resonances. The H NMR spectra
2
(
300 MHz, δ in ppm) of H L and its diamagnetic UO (II) complex were recorded in DMSO-
2
2
d6. The aromatic ring protons of the ligand are detected at 7.35, 7 and 6.6 ppm, while the
aromatic ring protons for the complex consist of a set of multiplets in the range 7.4-6.1 ppm
(m, 8H, Ar-CH). The signal of the OH protons for the free ligand disappear in the spectrum
of the complex, showing coordination take places through the deprotonated phenolic oxygen
atoms. Also, the upfield shift of the azomethinic proton signals in the spectrum of the
complex with respect to the corresponding value of the free ligand reveals coordination
through the azomethinic nitrogen atoms. The signals related to the protons of the alcohol
molecule in the spectrum of the complex suggest that the molecule is not coordinated to the
1
uranium center in the presence of DMSO as the H NMR solvent.
Insert Scheme 1.
3
. 6. Thermogravimetry
The thermal analyses of the tetradentate N O donor ligand and its uranium complex were
2
2
performed to obtain information about their thermal stability. Thermogravimetric studies
-1
were done in the temperature range 20-1000 ºC at a heating rate of 10 ºC min . The TG
curves are depicted in Fig. 1. Fig. 2 shows the partial mass losses with the assignments at
each decomposition stage, based on mass calculations. The obtained results are in good
agreement with the theoretical values suggested from the C, H and N analysis.
The ligand gives a decomposition pattern of three stages. The first stage, in the region 163-
1
84 ºC, corresponds to the evolution of the S-ethyl moiety, with a found mass loss of 18.16%
(calcd. 18.67%). The second stage, in the temperature range 203-2236 ºC, is related to the
loss of the C=N-N=C-N=C fragment, with a found mass loss of 24.86% (calcd. 25.37%). The
final stage of the thermal decomposition of the ligand is attributed to the loss of two C H OH
6
6
1
0

fragments, with a found mass loss of 57.83% (calcd. 57.48%), within the temperature range
45-294 ºC.
2
The complex gives a decomposition pattern of two stages. The first stage, within the
temperature range 198-263 ºC, corresponds to the evolution of S-ethyl and MeOH molecules,
with a found mass loss of 15.00% (calcd. 14.84%). The second stage, within the temperature
range 293-468 ºC, is attributed to the loss of the remaining parts of the ligand, with a found
mass loss of 43.33% (calcd. 42.60%), leaving the final residuum U O with a weight 43.08%
3
8
(calc. 44.73%), which is stable from 468 to 1000 °C.
Insert Fig. 1.
Insert Fig. 2.
3
. 7. X-ray study
X-ray diffraction provided detailed structural parameters for the studied complex. The ortep
plot with the atom numbering is shown in Fig. 3. Selected bond lengths and bond angles are
tabulated in Table 3. In order to compare the structural futures of the new U complex with
similar compounds, we tabulated some data from the Cambridge Structural Database (CSD)
in Tables 4 and 5. The parameters used for comparison are explained in Scheme 2.
1
4
The complex contains a N ,N -disalicyliden-S-ethyl-thiosemicarbazone ligand with a trans-
UO ion and one methanol molecule. [Trans-UO (L)(MeOH)] crystallizes in the Pbca space
2
2
group with unit cell parameters a = 22.287(3) Å, b = 15.6245(14) Å, c = 11.4339(16) Å , α =
o
o
o
9
0 , β = 11.4339(16) , γ = 11.4339(16) , with eight molecules in the unit cell. The
pentagonal-bipyramidal geometry of the complex is easily seen in Fig. 3. Two imine nitrogen
atoms (N1 and N3) and two phenolic oxygen atoms (O3 and O4) from the tetradentate
thiosemicarbazone ligand and one oxygen atom (O5) from the coordinated methanol
molecule form a pentagon, while the two oxo groups (O1 and O2) occupy axial sites [5].
Coordination of the teteradentate ligand to the metal center results in one six-membered and
to two five-membered chelate rings. Similar to the studied complex here, in U-based
isothiosemicarbazone complexes the six-membered chelate rings show a half-chair
conformation, but the conformation of the five-membered chelate ring may be planar or not,
due to the some electron delocalization in the thiosemicarbazide group. The orientations of
the coordinated solvents and S-alkyl groups in the uranyl complexes are somewhat different,
probably due to different crystal packing.
The U1-O3, U1-O4, U1-N1 and U1-N3 bond distances in the tetradentate ligand are 2.28(1),
2
.22(1), 2.57(2) and 2.54(2) Å. From Table 4, the U-O and U-N bond distances are in the
region previously published for uranium isothiosemicarbazone complexes (e.g., in the
1
1

1
4
complexes
of
dimethylsulfoxide-(S-ethyl-N ,N -bis-(2-hydroxybenzaldehyde)-
isothiosemicarbazide-N,N',O,O')-dioxidouranium(VI), with U1-O3/4 of 2.25 Å on average
1
4
and U1-N1/3 of 2.58 Å on average [14], and ethanol-(S-methyl-N ,N -bis-(2-
hydroxybenzaldehyde)-isothiosemicarbazide-N,N',O,O')-dioxidouranium(VI), with U1-O3/4
of 2.24 Å on average and U1-N1/3 of 2.56 Å on average [13]).
2
However, the U1-O5 bond length is longer than those in [UO (L )DMSO], with the parent
2
organic ligand. This is due to the different nature of the coordinated solvents. Subsequently,
2
the U1-N1 and U1-N3 bond lengths in the [UO (L )DMSO] complex are longer than in the
2
studied complex here, imposed by the trans effect of the DMSO ligand. As can be seen in
Table 3, the uranium-oxygen bond distances in the complex are shorter than the uranium-
nitrogen bond distances, based on the hard and soft acid-base concept explained by Pearson.
The U=O1 and U=O2 bond distances are 1.76(1) Å, much shorter than the equatorial U-O
bond lengths, including the multiple bond order. A search in the Cambridge Structural
Database (CSD) demonstrates the coordination environments around the uranyl cations have
very little effect on the U=O bond lengths.
The apical U1-O2/3 bond distances are in good accordance with the values reported
previously for seven-coordinated uranyl complexes (e.g., in the complexes of 1-nonanol-(S-
1
4
methyl-N -(3,5-dichlorosalicylidene)-N -(2-hydroxybenzaldehyde)-isothiosemicarbazide-
N,N',O,O')-dioxidouranium(VI), with U1-O2/3 of 1.76 Å on average [15], and allyl alcohol-
1
4
(
S-propyl-N ,N -bis-(5-bromosalicylidene)-isothiosemicarbazide-N,N',O,O')-
dioxidouranium(VI) with U1-O2/3 of 1.76 Å on average [16]
The atoms N1, N3, O3, O4, O5 and U1 deviate from the pentagonal plane by 0.309, 0.354,
0
.24, 0.14, 0.05 and 0.02 Å. Atoms N1, N3 and O3 are significantly out of the pentagonal
plane, as indicated by the torsion angle O3N1N3O4 of 32.17°. The central ion in the complex
is approximately located on the pentagonal plane. From Table 5, this is in common with
similar structures. The two oxo atoms O1 and O2 of the uranyl moiety lie trans to each other,
as indicated by the O1=U1=O2 angle of 178.9°.
In an ideal pentagonal-bipyramidal geometry, each of the five angles subtended at the
equatorial plane must be 72°. The angles around the U atoms are not equivalent and stand in
the interval 61.8(5)-81.34(4)°, showing significant distortion [13]. Distortion of the ideal
pentagonal-bypiramidal geometry is also well detectable by the O(oxo)-U-O,N angles, that
are in the region 85.8(5) to 94.1(5)°. The dihedral angle between the UN O plane and the
2
3
plane including the metal and two axial O atoms is 87.55°.
1
2

The phenolic parts of the ligand are not planar and show a propeller-like conformation with
respect to each other, as can be seen by the dihedral angle of 42.42°. This may be due to the
large radius of the uranium ion, without putting significant strain on the backbone of the
ligand. The propeller-like conformation of the complex is also detectable by considering the
angles between the mean planes U1-N1-C7-C6-C1-O3 and U1-N3-C9-C10-C15-O4, which is
calculated to be 29.51º. This distortion in the uranium complexes, including bis-
isothiosemicarbazones, is common (see Table 5) [8].
The dihedral angles between the pentagon plane of O5-O3-N1-N3-O4 and the benzene rings
planes of C1-C2-C3-C4-C5-C6 and C14-C15-C10-C11-C12-C13 are 31.48 and 43.32°
respectively, indicating a non-planar disposition of the tetradentate isothiosemicarbazone
ligand. As can be seen from the values of folding of the chelating rings 1, 2 and 3 along
N1…N3, N1…O3 and N3…O4 respectively, it is clearly obvious the ligand is coordinated to
the uranium center in a concave way and this is in common with most tetradentate N O
2
2
donor isothiosemicarbazone complexes (see Scheme 2 and Table 5).
The intermolecular hydrogen bonds detected in the crystal structure of the complex are
summarized in Table 6. The molecule has the donor as well as the acceptor group and forms
centrosymmetric dimers through an interaction between the O5-H5A donor of the
-
coordinated methanol solvent and the O acceptor of the phenolato group. The ring pattern is
2
R (8) (Fig. 4.).
2
2
The studied complex [UO (L )MeOH] links with a neighbouring complex and forms an O-
2
H…O hydrogen bond using the hydroxyl group of the MeOH ligand and the phenolic oxygen
2
atom of the adjacent molecule. However, the reported complex [UO (L )DMSO] with the
2
parent organic ligand does not show this intermolecular interaction due to absence of a
hydroxyl group [14].
Insert Table 3.
Insert Table 4.
Insert Table 5.
Insert Table 6.
Insert Scheme 2.
Insert Fig. 3.
Insert Fig. 4.
4
. Conclusion
1
3

This study presents the successful synthesis and characterization of a new tetradentate
isothiosemicarbazone ligand and its UO (II) complex. Based on the spectral and structural
2
data, it was found that the ligand coordinates to the metal center as a tetradentate N O donor.
2
2
The uranium complex adopts a pentagonal bipyramidal geometry and has a propeller-like
1
conformation. Results from DFT calculations for the structural preference reveal that H L
2
2
(
tridentate) and H L (tetradentate) adopt the E and Z forms respectively. According to the
2
2
NBO calculations, the N and O donor atoms of H L transmit electrons towards the central
2
U(VI) metal ion. Also, in the trans-UO fragment, the σ and π bonding orbitals and the σ*
2
and π* antibonding orbitals are polarized toward the ligand and metal ion respectively.
Thermogravimetric analysis showed the thermal decomposition results in the metal oxide
U O as the final residue.
3
8
Finally, the uranium complex is air-stable and is soluble in most solvents. These may lead to
a trend for researchers to develop its applications in biological and catalytic activities [35,36].
DFT calculations can be applied successfully to predict the structural geometry and interpret
the natural bond orbital analyses [37,38].
Supplementary data
CCDC 1510074 contains the supplementary crystallographic data of the complex. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgments
We would like to thank Silesia University for the provision of a diffractometer.
References
[
1] V.B. Arion, V.C. Kravtsov, R. Goddard, E. Bill, J.I. Gradinaru, N.V. Gerbeleu, V.
Levitschi, H. Vezin, Y.A. Simonov, J. Lipkowski, V.K. Belskii, Inorg. Chim. Acta 317
(
[
(
[
2001) 33-44.
2] M.T. Cocco, C. Congiu, V. Onnis, M.L. Pellerano, A.D. Logu, Bioorg, Med. Chem. 10
2002) 501-506.
3] E. Maccioni, M.C. Cardia, L. Bonsignore, A. Plumitallo, M.L. Pellerano, A.D. Logu, Il
Farmaco 57 (2002) 809-817.
4] M. shahin, T.B. Demirci, G.P. Soylu, B. Ulkuseven, Inorg. Chim. Acta 362 (2009) 2407-
412.
[
2
1
4

[
[
5] M. Ahmadi, J.T. Mague, A. Akbari, R. Takjoo, Polyhedron 42 (2012) 128-134.
6] V.M. Leovac, V. Divjakovic, A.F. Petrovic, N.V. Gerbeleu, Monatsh. Chem. 120 (1989)
1
81-186.
7] A. Fasihizad, A. Akbari, M. Ahmadi, M. Dusek, M. S. Henriques, M. Pojarova,
Polyhedron 115 (2016) 297-305.
[
[
[
8] N. Özdemir, M. Sahin, T. Bal-Demirci, B. Ülküseven, Polyhedron 30 (2011) 515-521.
9] B. Atasever, B. Ülkuseven, T.B. Demirci, S.E. Kuruca, Z. Solakoglu, Invest. New Drugs.
2
8 (2010) 421-432.
10] V.B. Arion, P. Rapta, J. Telser, S.S. Shova, M. Breza, K. Luspai, J. Kozisek, Inorg.
Chem. 50 (2011) 2918-2931.
11] L.R. Morss, N.M. Edelstein, J. Fuger, The Chemistry of the Actinide and
Transactinide Elements (Set Vol.1-6): Volumes 1-6, Springer, 2010.
12] P. Zanello, A. Cinquantini, P. Guerriero, S. Tamburini, P.A. Vigato, Inorg. Chim. Acta
17 (1986) 91-96.
13] V.M. Leovac, E.Z. Ivegeš, N. Galešić, D. Horvatić, Inorg. Chim. Acta. 162 (1989) 277-
80.
[
[
[
1
[
2
[
[
14] R. Takjoo, S. W. Ng, E. R. T. Tiekink, Acta Cryst. E. 68 (2012) m244-m245.
15] M. Sahin, A. Koca, N. Ozdemir, M. Dincer, O. Buyukgungor, T. Bal-Demirci, B.
Ulkuseven, Dalton Trans. 39 (2010) 10228-10237.
16] M. Şahin, T. Bal-Demirci, N. Özdemir, B, Ülküseven, J. Coord. Chem. 66 (2013) 3519-
530.
17] R. Takjoo, G. Dutkiewicz, M. Kubicki, Acta Crystallogr., Sect. E 67 (2011) m1824-
m1825.
18] R. Takjoo, A. Najafi, S.W. Ng, E.R.T. Tiekink, Acta Crystallogr., Sect. E 68 (2012)
m255-m256.
19] R. Takjoo, M. Ahmadi, S.W. Ng, E.R.T. Tiekink, Acta Crystallogr., Sect. E 68 (2012)
m279-m280.
[
3
[
[
[
[
[
20] R. Centore, M. Ahmadi, A. Peluso, Acta Crystallogr., Sect. E 69 (2013) m362-m363.
21] M. Sahin, N. Ozdemir, T. Bal-Demirci, B. Ulkuseven, M. Dincer, M.S. Soylu,
Spectrochim. Acta, Part A 135 (2015) 994-1001.
[
[
[
[
22] B. Ülküseven, M. Ceritoglu, Transition Met. Chem. 27 (2002) 390-393.
23] CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.37.35g, 2014
24] G.M. Sheldrick, ActaCrystallogr., Sect. A 64 (2008) 112-122.
25] A.D. Becke, J. Chem. Phys. 98 (1993) 5648-5652.
1
5

[
[
26] J.S. Binkley, J.A. Pople, W.J. Hehre, J. Am. Chem. Soc. 102 (1980) 939-947.
27] a) T.H. Dunning, P.J. Hay, H.F. Schaefer, In Modern Theo. Chem.; third ed., vol. 3,
Plenum Press, New York, 1976, p. 1; b) P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 299;
c) P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270.
[
[
[
[
28] M.J. Frisch et al., Gaussian 98, Revision A.7, Gaussian, Inc., Pittsburgh PA, 1998.
29] V. Barone, M. Cossi, J. Phys. Chem. A. 102 (1998) 1995-2001.
30] E. Reed, L.A. Curtiss, F. Weinhold, Chem. Rev. 88 (1988) 899-926.
31] M. Ahmadi, A. Fasihizad, B. Machura, R. Kruszynski, T. Barak, Polyhedron 81 (2014)
1
15-122.
32] A. Fasihizad, T. Barak, M. Ahmadi, M. Dusek, M. Pojarova, J. Coord. Chem. 67 (2014)
160-2170.
[
2
[
[
[
[
[
33] A. Forni, J. Gradinaru, Acta Cryst. B. 58 (2002) 900-902.
34] A. Forni, J. Gradinaru, Acta Cryst. C. 58 (2002) 342-344.
35] K. Takao, Y. Ikeda, Inorg. Chem., 46 (2007) 1550-1562.
36] J.L. Sessler, P.J. Melfi, G.D. Pantos, Coord. Chem. Rev., 250 (2006) 816-843.
37] M. Udayakumar, K. Jagatheeswaran, S.S. Ganesan, N.S. Venkataramanan, S.M. Kumar,
K. Byrappa, S. Thamotharan, J. Mol. Struct. 1133 (2017) 510-518.
38] E.K. Astani, N.L. Hadipour, C.-J. Chen, Chem. Phys. Lett. 672 (2017) 80-88.
[
1
6

Figure captions:
Scheme 1. A key for the assignment of the proton resonances.
Scheme 2. Schematic of U(VI) isothiosemicarbazones as a key to the quantities in Tables 3
and 4.
Fig. 1. Thermal decomposition diagrams.
Fig. 2. The proposed mechanisms for thermal decomposition.
Fig. 3. Ortep diagram of the complex. Thermal ellipsoids are drawn at the 30% probability
level.
Fig. 4. Centrosymmetric H bonded dimer in the complex. H bonds are represented by dashed
thick lines.
1
7

Scheme 1.
1
8

Scheme 2.
1
9

Fig. 1.
2
0

Fig. 2.
2
1

Fig. 3.
2
2

Fig. 4.
2
3

Table 1. Crystal data and structure refinement for the uranium complex.
Empirical formula
Formula weight
Temperature [K]
Wavelength [Å]
Crystal system
Space group
C H N O SU
18 19 3 5
627.45
293.0(2)
0.71073
Orthorhombic
Pbca
a = 22.287(3)
b = 15.6245(14)
c = 11.4339(16)
3981.6(9)
8
2.093
8.293
2368
Unit cell dimensions [Å, °]
3
Volume [Å ]
Z
3
Calculated density [Mg/m ]
-
1
Absorption coefficient [mm ]
F(000)
Crystal size [mm]
0.164 x 0.111 x 0.037
3.52 to 25.05

range for data collection []
-
-
-
26  h  21
18 k 13
13 l 10
Index ranges
Reflections collected
10822
Independent reflections
3518 [R(int) = 0.0777]
99.8
1.000 and 0.23380
3518 / 2 / 258
Completeness to 2= 25.05º [%]
Max. and min. transmission
Data / restraints / parameters
2
Goodness-of-fit on F
1.110
Final R indices [I>2(I)]
R1 = 0.0798, wR2 = 0.1666
R1 = 0.1312, wR2 = 0.1843
2.145 and -1.837
R indices (all data)
-
3
Largest diff. peak and hole [e Å ]
2
4

Table 2. The experimental and calculated IR vibrational frequencies of the tetradentate ligand and its U(VI) complex.
2
H L
2
U complex
Scaled.
a
Exp.
-
Scaled.
-
Exp.
439(m)
Assignment.
ν(MN)
ν(MO)
ν(CSC)
δoopb(CH)-aromatic
411
559
642
-
-
586(m)
671(w)
6
50(w)
635
7
8
-
52(m)
12(w)
734
801
-
756(m)
-
870(m)
764
-
861
δoopb(OH)
ν (trans-UO )
sy
2
-
-
910(s)
1203(m)
1250(m)
1435(s)
1550(vs)
-
901
ν (trans-UO )
asy
2
1
1
1
1
1
1
2
3
3
-
211(w)
253(m)
454(s)
1241
1265
1427
1493
1600
1603
2914-3023
3062-3121
3431
-
1227
1245
1463
1567
-
3
2
2
ν(N=C-N ) + ν(C O )
ν(CO)
8
2
ν(C =N ) + ν(C=C)
ν(C=C)
485(vs)
573(m)
613(m)
ν(C=C) + δipb(OH)
1589(s)
1592
7
1
ν(C =N ) + ν(C=C)
ν(CH)-Et
854-2966(w)
012-3063(w)
351(m)
2854-2966(w) 2904-3011
3012-3063(w) 3024-3131
ν(CH)-aromatic
ν(OH)
ν(OH)-alcohol
-
-
3409(ms)
3531
a
-1
Wavenumbers (cm )
Abbreviation: vs; very strong, s; strong, m; medium, w; weak, sy; symmetric, asy; asymmetric, ν; stretching, δ;
bending, oopb; out of plane bending; ipb; in plane bending.
2
5

Table 3. Selected bond lengths (Å) and bond angles (°) of the complex [trans-UO (L)(MeOH)].
2
a
b
a
b
Bond lengths X-ray
Optimized
Optimized
Bond angles X-ray
O2-U1-O1 178.9(6)
Optimized Optimized
U1-O1
U1-O2
U1-O3
U1-O4
U1-O5
U1-N3
U1-N1
C7-N1
N1-N2
N2-C8
C8-N3
N3-C9
C15-O4
C1-O3
C8-S1
1.76(1)
1.78
1.78
2.29
2.26
2.58
2.55
2.58
1.30
1.39
1.28
1.40
1.30
1.30
1.30
1.78
1.79
1.79
2.25
2.26
2.55
2.58
2.56
1.30
1.39
1.29
1.40
1.30
1.30
1.31
1.78
177.8
89.7
89.4
91.6
90.2
71.9
63.2
71.5
85.6
72.4
176.2
1.76(1)
2.28(1)
2.22(1)
2.41(1)
2.54(2)
2.57(2)
1.28(3)
1.43(2)
1.26(3)
1.42(3)
1.31(3)
1.32(2)
1.32(2)
1.72(2)
O2-U1-O4
O2-U1-O3
O1-U1-O4
O1-U1-O3
O3-U1-N1
N1-U1-N3
N3-U1-O4
O4-U1-O5
O5-U1-O3
90.5(5)
85.8(5)
89.2(5)
94.1(5)
69.9(4)
61.8(5)
71.3(5)
79.4(5)
81.3(4)
89.5
89.7
90.6
91.7
71.1
62.2
70.8
82.4
73.0
a
gas phase
b
solution phase
2
6

Table 4. Comparison of the chelated ligand geometries (Å and º) for the [trans-UO (L)(MeOH)] complex.
2
U=O1
1.76(1) 1.76(1) 2.28(1) 2.22(1) 2.57(2) 2.54(2) 178.9(6)
1.77(8) 1.76(8) 2.24(8) 2.26(7) 2.55(9) 2.56(8) 176.6(4)
U=O2
U-O3
U-O4
U-N1
U-N3
O1=U=O2 O4-N3-N1-O3
1
2
3
4
32.2(8)
19.3(5)
1.77(4) 1.77(4) 2.23(4) 2.29(4) 2.56(4) 2.56(5) 177.6(2)
1.74(1) 1.74(1) 2.20(2) 2.27(1) 2.54(3) 2.59(1) 175.76
32.2(2)
10.64
1
2
3
4
U complex studied here.
CCDC entry EPIJET (Ref. [8]).
CCDC entry KAZKED (Ref. [5]).
CCDC entry VAXKAG (Ref. [23]).
2
7

Table 5. Conformational angles (º) for the [trans-UO (L)(MeOH)] complex.
2
Fold of ring Fold of ring Fold of ring Angle
Angle
between the
Angle
between the
Distance of
The metal
1
along
2 along
3 along
between the
1
3
1
3
3
4
N …N
N …O
N …O
mean planes mean planes mean planes from
the
of rings
and 2
1
of rings
and 3
1
of rings
and 3
2
pentagon
plane
of
O3-N1-N3-
O4-X
0.02
0.03
0.02
1
2
3
4
1.96
7.48
2.56
4.14
15.66
4.88
19.77
1.39
20.76
22.56
17.53
10.96
13.41
15.85
10.35
7.07
16.10
20.71
16.85
10.81
29.51
31.98
27.05
15.53
0.00
1
2
3
4
U complex studied here.
CCDC entry EPIJET (Ref. [8]).
CCDC entry KAZKED (Ref. [5]).
CCDC entry VAXKAG (Ref. [23]).
2
8

Table 6. Hydrogen bonds for [trans-UO (L)(MeOH)] [Å and °].
2
Symmetry code on A atom
D-H···A
d(D-H)
d(H···A) d(D···A) <(DHA)
1.8(1) 2.64(2) 161(16)
O5-H5...O3
0.9(1)
1-x, 1-y, 1-z
2
9