Synthesis, structural and DFT interpretation of a Schiff base assisted Mn(III) derivative

Article abstract of DOI:10.1016/j.molstruc.2019.126985

A mononuclear Mn^III derivative, [Mn(L)(SCN)(H₂O)] (1) [where H₂L = N,N′-bis(salicyaldehydene)-1,3-diaminopropan-2-ol] has been synthesized and systematically characterized. In 1, the central Mn^III ion is linked

Full text of DOI:10.1016/j.molstruc.2019.126985

Journal of Molecular Structure 1199 (2020) 126985
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis, structural and DFT interpretation of a Schiff base assisted
Mn(III) derivative
,
Kuheli Das a **, Chiara Massera b, Eugenio Garribba c, Antonio Frontera d,
,
*
Amitabha Datta e
a Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Kolkata, 700009, India
b
ꢀ
ꢀ
Dipartimento di Scienze Chimiche, della Vita e della Sostenibilita Ambientale, Universita degli Studi di Parma, Viale delle Scienze 17/A, 43124, Parma, Italy
c
ꢀ
Dipartimento di Chimica e Farmacia, Universita di Sassari, Via Vienna 2, I-07100, Sassari, Italy
d Departament de Química, Universitat de les Illes Balears, Crta de Valldemossa km 7.5, 07122, Palma de Mallorca, Baleares, Spain
e Institute of Chemistry, Academia Sinica, Nankang, Taipei, 115, Taiwan
a r t i c l e i n f o
a b s t r a c t
A mononuclear MnIII derivative, [Mn(L)(SCN)(H2O)] (1) [where H2L ¼ N,N0-bis(salicyaldehydene)-1,3-
diaminopropan-2-ol] has been synthesized and systematically characterized. In 1, the central MnIII ion
is linked to the NNOO donor atoms of the potentially binucleating precursor L2ꢀ and additionally co-
ordinates one water molecule and the pseudohalide SCNꢀ, thus yielding a distorted octahedral geometry.
Article history:
Received 9 April 2019
Received in revised form
19 August 2019
Accepted 25 August 2019
Available online 26 August 2019
The UVeVis spectra of 1 shows an intense band corresponding to a 5T2g
ꢀ
5Eg transition at 545 nm; thus
presuming the octahedral geometry around the Mn ion. The solid and solution EPR spectra of 1 have
been simulated with an HP 53150A microwave frequency counter which has confirmed the þ3 oxidation
state of the metal ion. We have also conducted a DFT computational study which has confirmed that
Keywords:
Mn(III)
Schiff base
Crystal structure
EPR
compound 1 self assembles into a two-dimensional network via O‒H/O,
pep, and unconventional C‒H
…
p
(SCN) interactions involving the -system of the thiocyanate. The room temperature magnetic
p
susceptibility of compound 1 has yielded an effective magnetic moment (meff) value of 4.96 B.M.
© 2019 Elsevier B.V. All rights reserved.
DFT
1. Introduction
inertness [7e9]. The geometry of these metal derivatives depends
upon the size and electronic configuration of the metal ions, the
The rational design and synthesis of new coordination com-
plexes of transition metals and multifunctional bridging ligands is
of great research interest, due to their potential applications as
functional materials and for the interesting topologies they can
create. In this context, substantial research is devoted to the
chemistry of manganese complexes with different oxidation states
incorporating N,O donor ligands [1e6] of various denticity. Indeed,
these ligands can display stereochemical diversity, specifically with
respect to their coordination numbers and/or geometry when
combined with different transition metals. In this framework, tri-
dentate and tetradentate precursors like salen-type Schiff bases
have been shown to form metal derivatives which can manifest
unusual coordination, high thermodynamic stability and kinetic
inherent rigidity of the ligand due to the presence of aromatic rings,
the presence of repulsive forces between non-bonded atoms in
different ligand arms etc [10e15]. Manganese(III) salen-type com-
plexes are very well studied because this type of Schiff base pre-
cursors [16,17] have revealed to be suitable for biological
applications [18,19]; besides, structurally diverse derivatives can be
good candidates for molecule-based magnetic materials [20e23].
Pseudohalide (OCNꢀ, SCNꢀ, N3ꢀ, etc.) ions can coordinate to tran-
sition metal atoms in different ways, for example as a terminal or
bridging ligands [24]. The crystallographic networks of Mn(III)
compounds containing pseudohalides as ligands have also been
reported by some groups [25e28]. Finally, Mn(III) compounds
incorporating salen-type Schiff base precursors with ancillary N-
donor co-ligands show interesting structural diversity and topo-
logical features [29e34]. In this context, we [35e41] and other
groups [42e47] have reported a large variety of metal complexes
with tridentate (N2O donor) and tetradentate (N2O2 donor) Schiff
base precursors. These studies have demonstrated the role played
* Corresponding author.
** Corresponding author.
E-mail addresses: kuheli.chemistry@gmail.com (K. Das), amitd_ju@yahoo.co.in
(A. Datta).
https://doi.org/10.1016/j.molstruc.2019.126985
0022-2860/© 2019 Elsevier B.V. All rights reserved.

2
K. Das et al. / Journal of Molecular Structure 1199 (2020) 126985
by the different transition metal ions and the Schiff base ligands in
the formation of coordination motifs with different nuclearities,
dimensionalities and topologies. Employing the precursor, [salicy-
ladimine ligand system], before several articles are published
mainly on CuII, CoII and NiII metal ions; but there is no report of the
Mn-derivative coupled with same precursor and pseudohalide
(-SCN) alongwith DFT interpretation till date. In the present
contribution, we have employed a potentially N,O-donor Schiff
base precursor, which, however, uses four coordination sites
(NNOO) to afford a new Mn(III) derivative, [Mn(L)(SCN)(H2O)] (1)
[where H2L ¼ C6H4(OH)-CH]N(CH2)-CH(OH)-(CH2)N]CH-(OH)
C6H4] [48]. We have carried out a systematic investigation of
complex 1 by means of different spectroscopic measurements.
Density functional theory calculations have been used to assess the
structural optimization of the compound and have been conducted
in combination with MEP and NCI plots to explain the self-assembly
of 1 into a two-dimensional network that rationalizes the ener-
getically most-favoured conformations.
compound of general formula [Mn(L)(NCS)(H2O)], where H2L is
N,N0-bis(salicyaldehydene)-1,3-diaminopropan-2-ol. The com-
pound crystallizes in the monoclinic space group C2/c, and its
asymmetric unit is shown in Fig.1. The Mn(III) ion shows a distorted
octahedral geometry of the type O3N3, where the deprotonated
ligand chelates the metal through two O and two N atoms, while a
water molecule and a thiocyanate ion occupy the two remaining
positions (See Table 1 for selected bond distances and angles). The
water molecule forms an intramolecular H-bond with the oxygen
atom O1 of the ligand. In the lattice, the complexes are connected
through a network of hydrogen bonds involving the coordinated
water molecule O1W and the hydroxyl group O1-H1 (see Table 2
and Fig. 2).
In particular, a double, centrosymmetric ribbon is formed along
the c-axis direction through O1-H1/O2i and O1W-H1W/O3ii in-
teractions [symmetry codes: (i) ¼ x, -y, ꢀ1/2 þ z; (ii) ¼ 2-x, y, 3/2-z].
These ribbons are in turn connected in the ab plane through S1/S1
interactions [4.393(3) Å [53], see Fig. 3).
2. Results & discussion
2.3. Electronic spectra
2.1. Synthesis and characterization
The Schiff base precursor, H2L [where H2L ¼ N,N0-bis(sali-
cyaldehydene)-1,3-diaminopropan-2-ol] is a condensed product of
salicylaldehyde and 1,3-diamino-2-propanol [48]. The stoichio-
metric reaction of H2L, MnCl2.4H2O and NaSCN in a methanol/water
mixture affords compound 1 in moderate yield (see Scheme 1), in
which the Mn(II) ion has undergone an oxidation to Mn(III). The
FTIR spectrum of compound 1 has been analyzed in comparison
with that of the respective free Schiff base ligand in the region
3600-450 cmꢀ1 and it shows data consistent with the structure of
the metal derivative.
The UVeVisible spectrum of compound 1 was recorded using
HPLC grade methanol in the range of 200e800 nm. The observed
electronic spectral data are in good agreement with the geometry
displayed by the compound. The electronic transition bands appear
at 215, 233, 279 and 375 nm which may be attributed to
p/p* and
n/ * transitions [54]. In the spectrum, a much weaker, less well-
p
defined broad band is originated in the lower energy regions
associated with ded transitions. Thus, compound 1 is concluded to
have an octahedral geometry, showing an intense band corre-
sponding to a 5T2g ꢀ 5Eg transition at 545 nm; this band specifically
indicates the presence of a Mn(III) derivative, comparable to pre-
vious data reported in the literature [55e57] (see Fig. 4).
The absence of a weak broad band, observed in the region of
3600-3400 cmꢀ1 due to OHphenolic absorption of the free Schiff base
precursor, agrees with the formation of a new CeO absorption band
after complexation with the metal center, as the ligand undergoes
deprotonation [49]. The nC
]
N
band, appearing at 1611 cmꢀ1 in 1,
indicates that the azomethine nitrogen atom is coordinated by the
metal center [50e52], since for the free ligand, the same band is
found at 1690 cmꢀ1. Besides, the strong band at 2057 cmꢀ1 corre-
sponds to the stretching vibration of the N-coordinated eSCN
moiety. The water molecule coordinated by the Mn(III) ion displays
a broad band at 3321 cmꢀ1. The ligand coordination to the metal
centre is further substantiated by the band appearing at 455 cmꢀ1
which is mainly attributed to a nM-N stretching frequency. Finally,
the single-crystal X-ray diffraction analysis has confirmed that the
resulting compound is
derivative.
a
mononuclear octahedral Mn(III)
2.2. Crystal structure
The molecular structure of
1 consists of a mononuclear
Fig. 1. Asymmetric unit of 1 with partial labelling scheme.
Scheme 1. Formation of compound 1.

K. Das et al. / Journal of Molecular Structure 1199 (2020) 126985
3
Table 1
2.5. EPR spectra
Selected bond lengths [Å] and angles [o] for 1.
The EPR spectra on the polycrystalline powder of 1, recorded as a
function of the temperature, are reported in Fig. S2 and are silent
between 298 and 100 K. However, even if no resonances were
revealed while changing temperature, some important findings can
be argued. In particular, the lack of signals can be ascribed to the
even number of electrons, a situation for which the zero field
splitting is usually large, and to the fast relaxation time [59,60]. This
indicate an oxidation state þIII for Mn, which is generally inactive
at the X-band frequency [61]; in contrast, both Mn(II) (3d5) and
Mn(IV) (3d3) would give well-resolved spectra even at room tem-
perature [59e61]. Moreover, the results are compatible with those
obtained for other Mn(III)-salen compounds for which a S ¼ 2 state
Mn1-N1
Mn1-N2
Mn1-O2
Mn1-O3
2.028(3)
2.052(4)
1.881(3)
1.898(2)
Mn1-O1W
2.302(5)
171.2(1)
174.5 (1)
172.2(2)
N1-Mn1-O3
N2-Mn1-O2
N3-Mn1-O1W
Table 2
Relevant geometrical parameters (Å, ꢁ) for the hydrogen bonding network in 1.
D-H$$$A
D-H
H$$$A
D$$$A
D-H$$$A
O1W-H2W/O1
O1-H1/O2i
0.83(9)
0.82
0.77(5)
2.01(7)
2.879(5)
2.07(5)
2.808(5)
2.882
2.803(4)
160(7)
159
159(6)
O1W-H1W/O3ii
Fig. 2. Hydrogen-bonded chains of 1 along the ceaxis direction. Only the H atoms involved in the supramolecular interactions (blue dotted lines) are shown. Symmetry codes:
(i) ¼ x, -y, ꢀ1/2 þ z; (ii) ¼ 2-x, y, 3/2-z.
Fig. 3. Packing of 1 viewed along the b-axis direction, in the ab plane. H atoms have
been omitted for clarity.
Fig. 4. Electronic spectrum of compound 1, measured in methanol.
2.4. Magnetic susceptibility
has been demonstrated [62,63]. In DMSO and MeOH solution an
Generally speaking, the magnetic properties of a compound
identical behavior of 1 was revealed and no EPR signals could be
arise from the spin and orbital angular momentum of its electrons.
detected (Fig. S3). These results would suggest that the elongated
However, the spin-only magnetic moment survives in all cases and
is related to the total number of unpaired electrons. The magnetic
moment of the Mn(III) derivative (1) was obtained on a solid
sample at room temperature. For this compound, the magnetic
octahedral structure and þIII oxidation state of 1 are retained in an
organic solvent.
2.6. DFT studies
value (meff ¼ 4.96 mB) is comparable with that of other high-spin
octahedral Mn(III) compounds [58]. The spin-only (g ¼ 2) value
The theoretical study here reported is devoted to the analysis of
the H-bonding network observed in the solid state of compound 1,
for S ¼ 2 is 3.00 cm3 K molꢀ1
.

4
K. Das et al. / Journal of Molecular Structure 1199 (2020) 126985
first elucidated through X-ray diffraction on single crystals (see
Section 2.2 and Fig. 2). Particularly, we have studied and compared
two H-bonded dimers involving either the Mn-coordinated water
molecule or the hydroxyl group of the Schiff-base ligand. First of all,
we have computed the molecular electrostatic potential (MEP)
plotted onto the van der Waals surface (isosurface 0.001 a.u.) of
compound 1 (Fig. 5) in order to investigate the electron rich and
electron poor regions of the molecule. Two different orientations
are represented in Fig. 5 and it can be observed that the most
positive region is located at the OH group of the Schiff-base ligand
(þ65 kcal/mol, Fig. 5a). The MEP is also large and positive at the
coordinated water molecule (þ50 kcal/mol, Fig. 5a) probably due to
its coordination to Mn. The most negative region is located in the
middle of both the O-atoms of the ligand (ꢀ52 kcal/mol, Fig. 5b).
Moreover, the MEP is also large and negative (ꢀ44 kcal/mol,
Fig. 5b) at the SCN ligand. Therefore, the most favoured interactions
from an electrostatic point of view are H-bonds between the OH/
H2O groups as donors and the O-atoms of the ligand and SCN as
acceptors. Fig. 6a shows a partial view of the X-ray crystal structure
of compound 1 (H-atoms omitted) where the two infinite 1D chains
are represented. Two H-bonded dimers are highlighted, which are
important connecting the 1D polymeric chains. The dimer denoted
as “A” is self-assembled (Fig. 6b) where each coordinated water
molecule establishes a bifurcated non-symmetrical H-bonding in-
teractions with the two phenolic O-atoms of the Schiff-base ligand
(blue and black dashed lines), O1W-H1W/O2ii and O1W-
H1W/O3ii, respectively; ii ¼ 2-x, y, 3/2-z). The interaction energy
D
E2 ¼ ꢀ23.4 kcal/mol. Finally, in order to estimate the contribution
of the CeH$$$ (SCN) interaction we have computed an additional
theoretical model where we have replaced the SCN ligand by a
hydrido ligand (Fig. 6d). As a result, the interaction energy is
reduced to
bution of the CeH$$$
p
D
E3 ¼ ꢀ20.3 kcal/mol thus indicating that the contri-
p
(SCN) interaction is modest (ꢀ3.1 kcal/mol).
In order to further characterize the non-covalent interactions
commented above, we have used the NCI plot index computational
tool. Non-covalent interactions are efficiently visualized and iden-
tified by using the NCI plot tool. It allows an easy assessment of
hosteguest complementarity and the extent to which weak in-
teractions stabilize a complex. Thþe color scheme is a red-yellow-
green-blue scale with red for rcut (repulsive) and blue for rcꢀut
(attractive). Yellow and green surfaces correspond to weak repul-
sive and weak attractive interactions, respectively. The NCI plot of
the dimer A of compound 1 is represented in Fig. 7a. The short
(stronger) H-bond is characterized by a small and blue isosurface
located between the O and the H atoms and the longer H-bond is
characterized by a green isosurface. The NCI plot also reveals the
presence of more extended isosurfaces between the aromatic rings,
thus indicating the existence of
pep stacking interactions in this
dimer that further stabilize the assembly. The NCI plot of the dimer
B is represented in Fig. 7b. Similarly to dimer A, the bifurcated H-
bond is characterized by one blue and one green isosurfaces located
between the hydroxyl group and the O-atoms. In addition, the NCI
plot shows a more extended and green isosurface that is located
between the SCN ligand and two aliphatic H-atoms of the Schiff
base ligand thus confirming the existence of the unconventional
of this dimer is very large (
DE1 ¼ ꢀ29.9 kcal/mol) due to the for-
mation of these four electrostatically enhanced H-bonds, as sug-
gested by the MEP surface in Fig. 5. Moreover, other long range
CeH$$$p(SCN) interaction. Finally, the intramolecular HB is char-
acterized by a small and blue isosurface.
interactions (pep stacking) contributing to the interaction energy
are also present in this dimer, as further commented below. In
dimer B (Fig. 6c) the OH group forms a bifurcated H-bond with the
phenolic O-atoms, in good agreement with the MEP analysis (see
also Fig. 2: O1-H1/O2i and O1-H1/O3i; i ¼ x, -y, ꢀ1/2 þ z).
Interestingly, in this dimer the H-atoms of the aliphatic linker
3. Conclusion
A new Mn(III) derivative has been synthesized by employing a
N2O3 donor Schiff base precursor, [N,N0-bis(salicyaldehydene)-1,3-
diaminopropan-2-ol], H2L. The solid state structure of 1 reveals
that the MnIII atom possesses an octahedral environment based on
the N2O2 donor atoms of the ligand and on the coordination of a
water molecule and an SCNꢀ anion. The EPR spectroscopy carried
out both in the solid state and in different solvents (DMSO and
CH3OH) confirms the þ3 oxidation state of the Mn ion. Compound 1
interact with the
unconventional CeH$$$
p-system of the SCN ligand, thus establishing
p
(SCN) interactions (C1iii-H1Biii$$$S1, C1iii-
H1Biii$$$C18 and C2iii-H2iii$$$N3; iii ¼ x, -y, ½þz). This agrees well
with the MEP analysis that shows positive MEP values at these H-
atoms (Fig. 5a) and negative at the thiocyanate ligand. The com-
bination of both interactions [H-bonds and CeH$$$
p
(SCN)] ex-
self assembles into a 2D network structure via O‒H/O, , and
p
ep
plains the large interaction energy computed for this dimer, i.e.
unconventional C‒H … (SCN) interactions involving the p-system
p
of the thiocyanate. DFT studies combined with MEP and NCI plots
have been used to characterize and rationalize the interactions that
are energetically very favorable due to the enhanced acidity of the
H-bond donors and the anionic nature of the acceptors. Further
exploration on electrocatalytic water oxidation studies utilizing
this MnIII derivative is in progress in our laboratory.
4. Experimental section
4.1. Materials
All the experiments were carried out under aerobic conditions.
MnCl2$4H2O was purchased from Aldrich Chemicals. Salicylalde-
hyde, 1,3-diamino-2-propanol and sodium thiocyanate were pur-
chased from Merck, India. Solvents were of reagent grade and used
without further purification. The Schiff base precursor was pre-
pared according to the literature [48].
4.2. Physical measurements
Microanalytical data (C, H, and N) were collected on
a
Fig. 5. Two views of the MEP surface of a model of compound 1. The values at selected
points of the surface are indicated.
PerkineElmer 2400 CHNS/O elemental analyzer. FTIR spectra were

K. Das et al. / Journal of Molecular Structure 1199 (2020) 126985
5
Fig. 6. (a) Partial view of the X-ray crystal structure of compound 1. H-atoms have been omitted for clarity. (bed) Theoretical models used to evaluate the noncovalent interactions.
Distances in Å. H-atoms have been omitted for clarity apart from those participating in H-bonding interactions.
Fig. 7. NCI plots of the dimers A (a) and B (b). The gradient cut-off is s ¼ 0.35 au, and the color scale is ꢀ0.04 <
r < 0.04 au.
recorded on a PerkinElmer RX-1 spectrophotometer in the range
4.3. Synthesis of the ligand (H2L)
3600-450 cmꢀ1 as KBr pellets. Electronic spectra were measured on
a PerkinElmer Lambda 25 (U.V.eVis.eN.I.R.) spectrophotometer.
EPR spectra were recorded from 0 to 8000 Gauss in the tempera-
ture range 100e298 K on the polycrystalline powder and at 100 K
on the polycrystalline powder dissolved in DMSO or MeOH with an
X-band Bruker EMX spectrometer equipped with a HP 53150A
microwave frequency counter. The instrumental parameters were
as follows: microwave frequency, 9.40e9.41 GHz; microwave po-
wer, 20 mW; time constant, 81.92 ms; modulation frequency,
100 kHz; modulation amplitude, 0.4 mT; resolution, 4096 points.
Room temperature magnetic susceptibilities were measured with
the 155 PAR vibrating sample magnetometer fitted with a Waker
Scientific 175 FBAL magnet.
First a 30 mL methanol solution of salicyldehyde (30 mmol,
3.66 g) was added to a 15 mL methanol solution of 1,3-diamino-2-
propanol (15 mmol, 1.35 g). The resulting orange solution was
then refluxed for 1 h, and after cooling down, the solvent was
removed under reduced pressure to afford an orange crystalline
solid which was collected as the ligand. Yield: 69%. Anal. Calc. for
C17H18N2O3: C, 68.42; H, 6.09; N, 9.39. Found: C, 68.77; H, 5.73; N,
9.71%.
4.4. Synthesis of compound (1)
To
a methanol solution (10 mL) of MnCl2$4H2O (0.197 g,
1 mmol), H2L (1 mmol) in 15 mL of methanol was added under
constant stirring. The resulting green solution was kept boiling for

6
K. Das et al. / Journal of Molecular Structure 1199 (2020) 126985
10 min. After that, still in warm condition, a 10 mL water solution of
sodium thiocyanate (0.081 g, 1 mmol) was added and the mixture
was kept undisturbed at room temperature. Dark brown
rectangular-shaped single crystals of 1 were generated after one
week. These were separated by filtration and air-dried before car-
rying out all physical measurements and analyses. Yield: 0.71 g.
Anal. Calc. for C18H18O4N3SMn: C, 50.42; H, 4.47; N, 9.80. Found: C,
50.11; H, 4.71; N, 9.57%.
calculations [69]. To evaluate the interactions in the solid state, the
crystallographic coordinates were used and only the position of the
H-bonds has been optimized. This procedure and theoretical
method have been successfully used in the past to evaluate similar
interactions [40,41,70]. The interaction energies were computed by
calculating the difference between the energies of the isolated
monomers and their assembly. The NCI plot is a visualization index
that efficiently allows the identification and visualization of non-
covalent interactions [71]. It is based on the electron density and
its derivatives and the isosurfaces correspond to both favorable and
unfavorable interactions. They are easily differentiated by the sign
of the second density Hessian eigenvalue and defined by the iso-
surface color. NCI analysis is a very convenient tool to rationalize
hosteguest complementarity and to know which interactions sta-
bilize a complþex. The color scheme is a red-yellow-green-blue scale
with red for rcut (repulsive) and blue for rꢀcut (attractive). Yellow and
green surfaces correspond to weak repulsive and weak attractive
interactions, respectively [72]. The molecular electrostatic potential
surfaces were computed at the same level using the G09 program
and plotted using the Gaussview software.
4.5. X-ray crystallography
The crystal structure of compound 1 was determined by X-ray
diffraction methods. Intensity data and cell parameters were
recorded at 293(2) K on a Bruker Breeze diffractometer (MoK
a ra-
diation
l
¼ 0.71073 Å) equipped with a CCD area detector and a
graphite monochromator. The raw frame data were processed us-
ing the programs SAINT and SADABS to yield the reflection data file
[64]. The structure was solved by Direct Methods using the SIR97
program [65] and refined on Fo2 by full-matrix least-squares pro-
cedures, using the SHELXL-2014/7 program [66] in the WinGX suite
v.2014.1 [67]. All non-hydrogen atoms were refined with aniso-
tropic atomic displacements, while the H atoms bound to C and O
were placed in calculated positions and refined isotropically using
the riding model, with CeH distances ranging from 0.93 to 0.98 Å,
OeH ¼ 0.82 Å and Uiso(H) set to 1.2e1.5Ueq(C/O). The H atoms of
the water molecule were found in the difference Fourier map and
refined freely. The weighting scheme used in the last cycle of
Statement
We wish to assure that our manuscript does not contain any
potential interest or “no conflict of interest”.
Acknowledgments
refinement was w ¼ 1/[
s
2Fo2 þ (0.0514P)2 þ 8.6151P], where P ¼ (Fo2
þ 2F2c)/3. Crystal data and experimental details for data collection
and structure refinement are reported in Table 3. Crystallographic
data for the structure reported have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publi-
cation no. CCDC-1907942 and can be obtained free of charge on
application to the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: þ44-1223-336-033; e-mail deposit@ccdc.cam.ac.uk or http://
www.ccdc.cam.ac.uk).
KD expresses her appreciation to the SERB (Science and Engi-
neering Research Board, India) Grant (PDF/2016/002832) for
financial assistance. AF wish to thank the DGICYT of Spain (project
CTQ2017-85821-R FEDER funds). We also thank the CTI (UIB) for
computational facilities.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.molstruc.2019.126985.
4.6. Theoretical methods
The calculations of the noncovalent interactions and molecular
electrostatic potential (MEP) surfaces were carried out using the
Gaussian-09 program [68] and the B3LYP-D/def2-TZVP level of
theory. Grimme's dispersion correction has been used in the
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Table 3
Crystallographic data of compound 1.
Empirical formula
Formula weight
Temperature
Wavelength (Å)
Crystal system
Space group
a, Å
C18H18O4N3SMn
427.35
293(2)
0.71073
Monoclinic
C2/c
21.588(8)
14.338(5)
14.719(5)
124.524(4)
3754(2)
8
1.512
0.844
1760
18086
3158 (0.0606)
2382
1.002
0.0456, 0.1050
0.583, ꢀ0.369
b, Å
c, Å
b
, deg
Volume, Å3
Z
Dcalc (mg mꢀ3
)
m
(Mo K
F(000)
Total reflections
Unique reflections (Rint
a
) (mmꢀ1
)
)
Observed reflections [Fo > 4s(Fo)]
GOF on F2a
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R
indices [Fo>4
s
(Fo)]bR1, wR2
Largest diff. peak and hole, e.Åꢀ3

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