Azomethine diselenides: Supramolecular structures and facile formation of a bis-oxazoline diselenide

Article abstract of DOI:10.1016/j.jorganchem.2012.07.026

A series of N2Se2 and N2Se2O2 acyclic Schiff base diselenides (3-9) have been synthesized by condensation of bis(o-formylphenyl) diselenide and amines (aniline, p-bromoaniline, benzylamine, ethanolamine, 1-aminopropanol, 2-aminophenol). The Schiff base diselenides were characterized by elemental analysis, ESI-MS, NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy and X-ray crystallography. During crystallization compound 6 afforded bis(phenyloxazoline) diselenide 9 via cyclization of Schiff base of ethanolamine. The supramolecular nature of these diselenides is studied by X-ray crystallographic structure analysis.

Full text of DOI:10.1016/j.jorganchem.2012.07.026

Journal of Organometallic Chemistry 717 (2012) 45e51
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Azomethine diselenides: Supramolecular structures and facile formation
of a bis-oxazoline diselenide
*
*
Snigdha Panda , Pradip Kr. Dutta, G. Ramakrishna, C. Malla Reddy, Sanjio S. Zade
Department of Chemical Sciences, Indian Institute of Science Education and Research-Kolkata, PO: BCKV Campus Main Office, Mohanpur 741252, West Bengal, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of N2Se2 and N2Se2O2 acyclic Schiff base diselenides (3e9) have been synthesized by
condensation of bis(o-formylphenyl) diselenide and amines (aniline, p-bromoaniline, benzylamine,
ethanolamine, 1-aminopropanol, 2-aminophenol). The Schiff base diselenides were characterized by
elemental analysis, ESI-MS, NMR (1H, 13C, 77Se) spectroscopy and X-ray crystallography. During crystal-
lization compound 6 afforded bis(phenyloxazoline) diselenide 9 via cyclization of Schiff base of etha-
nolamine. The supramolecular nature of these diselenides is studied by X-ray crystallographic structure
analysis.
Received 9 May 2012
Received in revised form
4 July 2012
Accepted 15 July 2012
Keywords:
Schiff base
Diselenide
Ó 2012 Elsevier B.V. All rights reserved.
Oxazoline
Supramolecular structure
1. Introduction
crystals in these systems are reported to be influenced by non-
bonding interactions between the
p systems as well as by weak
The chemistry of selenium ligands is a subject of growing
interest as a result of both their increasing accessibility and the
realization that they may display significantly different properties
interactions between chalcogens, chalcogeneheteroatom interac-
tions and hydrogen bonding.
We report here the synthesis and characterization of azome-
thine diselenides and their supramolecular structures. Supramo-
lecular properties of these compounds have been studied by X-ray
crystallography.
compared to
O and S containing ligands. Organoselenium
compounds have been extensively used in a variety of organic
reactions [1e4]. Other major applications of organoselenium
compounds are their use as a ligand [5e8] and biochemical appli-
cations [9e12]. Particularly, the chemistry of intramolecularly
coordinated organoselenium compounds has received a great deal
of attention [13]. Diorgano diselenides are being used as a) elec-
trophilic reagents in organic reactions [3,14,15], b) ligands for
coordination chemistry [2,16] and catalysis [17,18] and c) synthetic
model for glutathione peroxidase enzymes [19]. Organic dis-
elenides create supramolecular arrangement with Se/X
(X ¼ heteroatom) interactions. Molecular devices are constructed
on the concept of supramolecular chemistry [20].
In supramolecular chemistry, the directional forces are important.
These directional forces come from the weak interactions like
hydrogen bonding and pestacking interactions. It has been reported
that unsaturated (low-valent) chalcogen ligands organize themselves
to form columnar stacks [21e23]. The packing of the molecules in the
2. Result and discussion
2.1. Ligand syntheses
The Schiff base diselenide ligands 3e8 were synthesized by
condensation of bis(o-formylphenyl) diselenide [24,25] with aniline,
p-bromoaniline, benzylamine, ethanolamine, 1-aminopropanol,
respectively, at room temperature in dry acetonitrile (Scheme 1).
However, formation of 8 was unsuccessful under similar conditions
that have been used for the formation of 3e7. The bis(o-for-
mylphenyl) diselenide and 2-aminophenol were refluxed in benzene
with a drop of acetic acid as catalyst with removal of water by a dean-
stark apparatus to afford 8. All Schiff bases were obtained in pure
form with high yield. The precursor 2 and the Schiff-bases 3e8 were
characterized by elemental analysis, NMR (1H, 13C and 77Se), IR and
mass spectrometry. The compound 9 was characterized by NMR (1H,
13C and 77Se). The Schiff bases were crystallized from chloroform/
hexane solution. The 77Se NMR spectra of the compounds 3e8 show
high frequency shift compared to precursor diselenide 2. It suggests
* Corresponding authors.
E-mail addresses: snigdha@iiserkol.ac.in (S. Panda), sanjiozade@iiserkol.ac.in
(S.S. Zade).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.07.026

46
S. Panda et al. / Journal of Organometallic Chemistry 717 (2012) 45e51
O
H
CHO
C
R
R
N
N
N
N
CHO
Cl
Amines
Se
Se
Na2Se2/THF
Se
Se
Se
Se
RT, Stirring
HMPA, 18 hr
reflux
CHO
C
H
1
2
O
9
OH
Br
R =
H2C
OH
OH
4
7
3
5
6
8
Scheme 1. Ligands synthesis.
the presence of stronger Se/N nonbonding interaction in 3e8 than
Se/O interaction in diselenide 2.
3.6826(7)) (Fig. 2b) interactions. The phenyl rings bearing Br-atoms
are stabilized by -stacking interactions. The remaining aromatic
rings are also stacked in such a way the -stacking interactions are
optimized (Fig. 3). The selected bond lengths and bond angles are
given in the Table 1.
p
Interestingly, when the compound 6 was crystallized in chlo-
roform/hexane, at ambient condition, the cyclization of the etha-
nolamine was occurred affording a bis(phenyloxazoline) diselenide
9. Recently, Singh et al. have synthesized bis(phenyloxazoline)
diselenide by lithiation procedure [26]. To generalize, if the similar
ring closing phenomenon is occurring with other amino alcohol
precursors, the reaction of bis(o-formylphenyl) diselenide with 3-
amino propanol and 2-aminophenol has been done, however no
ring formation is observed.
p
2.2.3. Crystal structure of compound 5
Compound 5 crystallizes in the monoclinic space group P21/c
with one molecule in the asymmetric unit (Z ¼ 4). Surprisingly the
cell angle
b
was found to be exactly 90ꢀ without any standard
deviations, which is unusual for a monoclinic system as generally
the
b
s 90ꢀ. To check if this is due to a wrong unit cell selection, we
2.2. Crystal structure description
tried to refine the structure in the orthorhombic space group. We
could not enforce the orthorhombic cell using XPREP program
integrated in Bruker APEX 2 software, but succeeded in WINGX
software. With some difficulty we could refine the structure in the
orthorhombic space group Pbca, but the calculated space group in
checkCif of this solution showed as P21/c. The subsequent mono-
clinic (P21/c) solution gave us the structure with an R-factor of
2.46%. So all this indicates that our unit cell selection is correct. The
ORTEP diagram of the compound 5 is shown in Fig. 4a. Interestingly,
The significant bond lengths and bond angles of the compounds
3e5, 8 and 9 are given in Table 1. Because of the hypervalent nature
of Se (strong Se/N non-bonded interaction which is w2.6e2.7 A),
ꢀ
the geometry around Se is found to be T shaped.
2.2.1. Crystal structure of compound 3
Compound 3 crystallizes in the triclinic P-1 space group with one
molecule in the asymmetric unit (Z ¼ 2) (Fig.1). The aromatic groups
around the diselenide centres are twisted away from each other
(Fig. 1a). The torsional angle of the selenium attached phenyl ring is
(C1eSe1eSe2eC14) 80.91(11). The packing diagram shows the
ꢀ
the molecules form a dimer via Se/HeC short contacts (2.936 A
ꢀ
which is well within the mean value of 3.1 A for CeH/Se contact).
The aromatic rings of the two molecules from a dimer form the
herring-bone type interactions (Fig. 4b). The packing of molecules
is shown in Fig. 5a. In the packing, the SeeSe bonds are arranged in
the horizontal line along the b-axis as shown in Fig. 5. The selected
bond lengths and angles are given in the Table 1.
formation of a supramolecular structure by p-stacking interactions
between the aromatic groups from adjacent molecules (Fig. 1b and
c). There are no strong hydrogen bonds in the structure which is
stabilized by the 3D close packing of molecules in the lattice. The
selected bond lengths and bond angles are given in Table 1.
2.2.4. Crystal structure of compound 9
The ORTEP diagram of the compound 9 is shown in Fig. 6. The
crystal structure analysis reveals that the most dominant contacts
2.2.2. Crystal structure of compound 4
The ORTEP diagram of the compound 4 is shown in Fig. 2a.
Interestingly, the molecules form a dimer via Se/Br (Se2/Br2,
are
p-stacking interactions. There are no other significant short
contacts, except some weak CeH/N interactions (N2/H9B_C9
Table 1
Some of the important bond lengths and bond angles of the compounds 3e5, 8 and 9.
Bond type
3
4
5
8
9
Se1/Se2
Se1/N1
Se2/N2
Se1/C1
Se2/C14
C]N
2.3741(6)
2.720(2)
2.734(2)
1.929(2)
1.940(3)
1.272(4)
1.272(3)
2.3677(6)
2.687(4)
2.717(4)
1.921(4)
1.933(4)
1.271(6)
1.269(6)
2.3611(4)
2.3316(9)
2.3408(4)
2.6374(19) (Se1/N2)
2.7875(18) (Se2/N1)
1.932(2) (Se2/C1)
1.937(2) (Se1/C15)
1.271(3)
2.766(4) (Se1/N1)
3.371(5) (Se1/O1)
1.923(5) (Se1/C1)
2.768(3) (Se1/N2)
2.772(3) (Se2/N1)
1.928(3) (Se2/C1)
1.932(3) (Se1/C10)
1.266(5) (N1eC7)
1.479(4) (N1eC9)
1.274(4) (N2eC16)
1.477(4) (N2eC18)
1.421(6) (N1eC8)
1.267(7) (N1eC7)
1.271(3)

S. Panda et al. / Journal of Organometallic Chemistry 717 (2012) 45e51
47
Fig. 1. (a) ORTEP diagram of compound 3. Thermal ellipsoids are drawn at 50% probability. (b) The stacking of aromatic rings from two adjacent molecules. (c) Crystal packing view
along b-axis.
2.7000,157.97). The packing diagram of the compound 9 along with
short contacts is shown in Fig. 7. The packing diagram shows the
arrangement of molecules where the SeeSe bonds are arranged in
the alternate up-down positions. The selenium attached phenyl
ring of the molecule in the asymmentric unit and one oxazoline
ring shows co-planarity while the other oxazoline ring deviates
from the co-planarity. The torsional angle of the selenium attached
phenyl ring is (C9eSe1eSe2eC10-83.76(14)), whereas the reported
torsion angle is ꢁ79.5(3)ꢀ [26].
reaction of bis (o-formylphenyl) diselenide with aminoethanol
afforded the corresponding Schiff base diselenide, however, during
crystallization it afforded oxazoline diselenide 9.
4. Experimental
4.1. Materials and methods
All the reagents were obtained from commercial sources and
used without further purifications otherwise mentioned. All reac-
tions were carried out under inert atmosphere. Acetonitrile was
distilled from P2O5 and kept over molecular sieves. UVevis spectra
2.2.5. Crystal structure of compound 8
Compound 8 crystallizes in the tetragonal space group I4(1)/
a with one molecule in the asymmetric unit (Z ¼ 8). The ORTEP
diagram of the compound 8 is shown in Fig. 8. Interestingly
molecules in the asymmetric unit form dimmer with another
were recorded on
a Hitachi U4100 spectrophotometer, with
a quartz cuvette (path length, 1 cm). 1H and 13C NMR spectra were
recorded on a JEOL-FT NMR-AL 400 MHz spectrophotometer using
CDCl3/DMSO-d6 as solvent and tetramethylsilane SiMe4 as internal
molecule via aromatic
3.294(8)) as shown in Fig. 9a. The crystal packing is stabilized
exclusively through the -stacking interactions (Fig. 9b). The 2-
p-stacking interactions (C13/C13_e
standards. Data are reported as follows: chemical shifts in ppm (
d),
p
multiplicity (s singlet, doublet, br broad singlet,
¼
d
¼
¼
hydroxybenzylidene ring shows the co-planarity with selenium-
attached phenyl rings. The torsional angle of the selenium-
attached phenyl ring is (C1eSe1eSe1_aeC1_a 81.1(2)).
m ¼ multiplet), coupling constants, integration, and interpretation.
Silica gel 60 (60e120 mesh) was used for column chromatography.
4.2. General synthetic procedure for azomethine diselenides 3e8
3. Conclusion
A stirred solution of bis(o-formylphenyl) diselenide in dry
acetonitrile was treated drop-wise with amines at room tempera-
ture for overnight. After evaporation of the solvent a yellow
precipitate obtained.
In conclusion we have demonstrated the supramolecular
structures of novel azomethine diselenides formed by various weak
contacts such as Se/H, CeH/N and
p-stacking interactions. The

48
S. Panda et al. / Journal of Organometallic Chemistry 717 (2012) 45e51
Fig. 2. (a) ORTEP diagram of compound 4. Thermal ellipsoids are drawn at 50% probability. (b) Ball and stick model showing a dimer formed by short Se/Br intermolecular
interactions.
4.2.1. Schiff base diselenide 3
3.06%. IR (KBr, cmꢁ1): 1623 cmꢁ1 (C]N stretching). ESI-MS:
C26H18Br2N2Se2 (675.82). 1H NMR (CDCl3, 400 MHz):
8.74 (s,
CH]N, 2H), 7.97e7.19 (m, aromatic protons, 16H). 13C NMR (CDCl3,
400 MHz): 159.69 (imine carbon), 148.6, 134.76, 134.43, 132.73,
Yield 96% (0.12 g). Mp 128.7 ꢀC. Anal. calc. for C26H20N2Se2
(518.37): C, 60.24; H, 3.89; N, 5.4. Found: C, 59.8; H, 3.02; N, 5.06%.
d
IR (KBr, cmꢁ1): 1623 cmꢁ1
(n
C]N stretching); ESI-MS: C26H20N2Se2
(517). 1H NMR (CDCl3, 400 MHz):
8.78 (s, CH]N, 2H), 7.99e7.25
(m, C6H5, 16H). 13C NMR (CDCl3, 400 MHz):
159.35 (imine
d
d
132.32, 131.84, 131.27, 126.13, 122.82, 120.04 (aromatic carbons).
d
77Se NMR (CDCl3, 400 MHZ):
d 475 ppm.
carbon), 149.01, 135.0, 133.58, 131.76, 131.58, 130.52, 129.6, 128.55,
128.02, 127.04, 125.79 (aromatic carbons). 77Se NMR (CDCl3,
4.2.3. Schiff base diselenide 5
400 MHz):
d
473 ppm.
Yield 96% (0.1 g). Mp 136.5 ꢀC. Anal. calc. for C28H24N2Se2
(546.42): C, 61.55; H, 4.43; N, 5.13. Found: C, 61.02; H, 4.3; N, 5.13%.
4.2.2. Schiff base diselenide 4
1H NMR (CDCl3, 400 MHz):
d
8.66 (s, CH]N, 2H), 7.918e7.22 (m,
aromatic protons, 18H), 4.99 (s, eCH2). 13C NMR (CDCl3, 400 MHz):
162 (imine carbon), 139.01, 134.77, 133.58, 131.76, 131.58, 130.52,
Yield 96% (0.12 g). Mp 155 ꢀC. Anal. calc. for C15H15NSeBr
(368.15): C, 48.94; H, 3.84; N, 3.81. Found: C, 46.03; H, 3.02; N,
d
Fig. 3. Crystal packing view down c-axis to show the optimization of
p-stacking interactions.

S. Panda et al. / Journal of Organometallic Chemistry 717 (2012) 45e51
49
Fig. 6. ORTEP diagram of compound 9. Thermal ellipsoids are drawn at 50%
probability.
129.6, 128.55, 128.02, 127.04, 125.79 (aromatic carbons), 64.06
(eCH2). 77Se NMR (CDCl3, 400 MHz):
d 470 ppm.
4.2.4. Schiff base diselenide 6
Yield 75% (0.092 g). Mp 215 ꢀC. Anal. calc. for C18H20N2O2Se2
(454.28): C, 47.59; H, 4.44; N, 6.17. Found: C, 46.98; H, 4.02; N,
6.00%. 1H NMR (CDCl3, 400 MHz):
d
8.6 (s, CH]N, 2H), 7.88e7.2 (m,
aromatic, 8H), 3.96 (t, 4H), 3.89 (t, 4H). 13C NMR (CDCl3, 400 MHz):
162.9, 132, 131.77, 129.57, 129.53, 126.25, 125.51, 67.4, 54.6. 77Se
NMR (CDCl3, 400 MHz): 450 ppm.
d
d
4.2.4.1. Oxazoline diselenide 9. Oxazoline diselenide 9 was obtained
during the crystallization of diselenide 6. 1H NMR (CDCl3,
400 MHz):
d 7.84 (m, aromatic, 4H), 7.23 (m, aromatic, 4H), 4.47 (t,
4H), 4.24 (t, 4H). 13C NMR (CDCl3, 400 MHz):
d 133, 131, 130, 129.7,
125.9, 125.7, 67.47, 55. 77Se NMR (CDCl3, 400 MHz):
d 450 ppm.
4.2.5. Schiff base diselenide 7
Yield 85% (0.13 g). Mp 121 ꢀC. ESI-MS: C20H24N2NaO2Se2
(507.0092). 1H NMR (CDCl3, 400 MHz):
d 9.15 (s, azomethine H),
9.04 (d, 2H), 8.15 (d, 2H), 7.70 (t, 2H), 7.55 (t, 2H), 4.46 (t, 4H), 3.71 (t,
4H), 2.19 (m, 4H), 1.69 (b, OH). 13C NMR (DMSO-d6, 400 MHz):
d
Fig. 4. (a) ORTEP diagram of compound 5. Thermal ellipsoids are drawn at 50%
probability. (b) Stick model of a dimer to show weak Se/H short contacts between
two adjacent molecules.
161.5, 134.6, 132.3, 131.9, 130.4, 130.3, 126.0, 58.6, 56.1, 34.0. 77Se
NMR (CDCl3, 400 MHz):
d 470 ppm.
Fig. 5. Packing diagram, view down b-axis of compound 5 to show the molecular arrangement in the crystal.

50
S. Panda et al. / Journal of Organometallic Chemistry 717 (2012) 45e51
Fig. 7. Packing diagram of compound 9 to show the molecular arrangement in the structure.
Fig. 8. ORTEP diagram of compound 8. Thermal ellipsoids are drawn at 50% probability.
Fig. 9. (a) Stacking of phenyl rings from adjacent molecules of compound 8. (b) Packing diagram view down b-axis to show the molecular arrangement in the crystal structure.

S. Panda et al. / Journal of Organometallic Chemistry 717 (2012) 45e51
51
Table 2
Crystallographic data and structure refinement parameters for compounds 3, 4, 5, 8 and 9.
3
4
5
8
9
Formula
C26H20N2Se2
Triclinic
P-1
C26H18Br2N2Se2
Monoclinic
P2(1)/c
9.8668(5)
24.9479(12)
9.4414(5)
90
90.834(3)
90
2323.8(2)
4
C28H24N2Se2
Monoclinic
P21/c
10.8124(5)
22.6756(9)
9.3971(4)
90
C26H20N2O2Se2
Tetragonal
I4(1)/a
11.6781(10)
11.6781(10)
33.121(3)
90
90
90
4517.0(3)
8
0.71073
1.619
C18H16N2O2Se2
Triclinic
P-1
Crystal system
Space group
ꢀ
a [A]
7.7491(17)
9.2040(19)
15.745(3)
79.318(5)
80.441(5)
86.542(5)
1087.7(4)
2
7.8435(5)
9.7654(6)
11.1628(7)
77.558(3)
78.116(3)
82.810(3)
814.11(9)
2
ꢀ
b [A]
ꢀ
c [A]
a
b
g
[ꢀ]
[ꢀ]
[ꢀ]
90
90
3
ꢀ
V [A ]
2303.96(17)
4
0.71073
1.575
1096.0
3.229
2.60e28.25
ꢁ14 ꢂ h ꢂ 5
ꢁ28 ꢂ k ꢂ 29
ꢁ12 ꢂ l ꢂ 12
296(2)
Z
l
ꢀ
[A]
0.71073
1.583
516.0
0.71073
1.933
1304.0
0.71073
1.775
444.0
rcalcd[g cmꢁ1
F[000]
]
2192
3.301
m
[mmꢁ1
[ꢀ]
]
3.415
6.637
4.553
q
2.25e27.6
ꢁ9 ꢂ h ꢂ 10
ꢁ11 ꢂ k ꢂ 11
ꢁ20 ꢂ l ꢂ 20
100(2)
2.16e28.28
ꢁ13 ꢂ h ꢂ 13
ꢁ32 ꢂ k ꢂ 31
ꢁ10 ꢂ l ꢂ 12
296(2)
2.46e19.51
ꢁ11 ꢂ h ꢂ 10
ꢁ10 ꢂ k ꢂ 11
ꢁ32 ꢂ l ꢂ 31
296(2)
2.57e46.40
ꢁ9 ꢂ h ꢂ 10
ꢁ12 ꢂ k ꢂ 12
ꢁ14 ꢂ l ꢂ 14
296(2)
Index ranges
T [K]
R1
0.0323
0.0468
0.0246
0.0251
0.0352
wR2
0.0712
0.1091
0.0429
0.0658
0.0884
Rmerge
0.0435
0.0574
0.0426
0.0441
0.0394
Parameters
GOF
272
1.020
224
1.044
290
0.696
146
0.530
169
1.442
Reflns total
Unique reflns
Obsd reflns
CCDC
19,120
4167
4976
867326
20,477
5593
4785
867327
10,548
5400
2835
867328
8909
1103
738
867330
12,855
3496
3174
867329
4.2.6. Schiff base diselenide 8
Yield 88% (0.13 g). Mp 185 ꢀC. ESI-MS: C26H20N2NaO2Se2
(574.9958). 1H NMR (CDCl3, 400 MHz):
8.89 (s, azomethine H),
7.9e7.07 (m, aromatic, 16 H). 13C NMR (CDCl3, 400 MHz):
158.3,
References
[1] C. Paulmier, in: J.E. Baldwin (Ed.), Selenium Reagents and Intermediates in
Organic Synthesis, Pergamon Press, Oxford, U.K, 1986.
[2] T. Wirth, Angew. Chem. Int. Ed. 39 (2000) 3740e3749.
[3] D.M. Freudendahl, S. Santoro, S.A. Shahzad, C. Santi, T. Wirth, Angew. Chem.
Int. Ed. 48 (2009) 8409e8411.
d
d
151.6, 135, 134.4, 133.8, 132.7, 131.42, 131.38, 129.3, 126.4, 120.4,
116.5, 115.6. 77Se NMR (CDCl3, 400 MHz):
d 463 ppm.
[4] D.M. Freudendahl, S.A. Shahzad, T. Wirth, Eur. J. Org. Chem. (2009)
1649e1664.
[5] A. Panda, Coord. Chem. Rev. 253 (2009) 1056e1098.
[6] W. Levason, S.D. Orchard, G. Reid, Coord. Chem. Rev. 225 (2002) 159e199.
[7] A.K. Singh, S. Sharma, Coord. Chem. Rev. 209 (2000) 49e98.
[8] U. Englich, K. Ruhlandt-Senge, Coord. Chem. Rev. 210 (2000) 135e179.
[9] G. Mugesh, W.-W. du Mont, H. Sies, Chem. Rev. 101 (2001) 2125e2180.
[10] T.G. Chasteen, R. Bentley, Chem. Rev. 103 (2003) 1e26.
[11] C.W. Nogueira, G. Zeni, J.B.T. Rocha, Chem. Rev. 104 (2004) 6255e6286.
[12] G. Zeni, D.S. Lüdtke, R.B. Panatieri, A.L. Braga, Chem. Rev. 106 (2006)
1032e1076.
[13] A.J. Mukherjee, S.S. Zade, H.B. Singh, R.B. Sunoj, Chem. Rev. 110 (2010)
4357e4416.
[14] L. Zhao, Z. Li, T. Wirth, Eur. J. Org. Chem. (2011) 176e182.
[15] T.G. Back (Ed.), Organoselenium Chemistry, Oxford University Press, Oxford,
1999.
4.3. X-ray crystallography
Intensity data were collected on a Bruker’s Kappa Apex II CCD
Duo diffractometer with graphite monochromatic MoK radiation
a
ꢀ
(0.71073 A) at the temperature of 100(2) K. Scaling and multiscan
absorption correction were employed using SADABS [27]. The
structures were solved by direct methods and all the non-
hydrogen atoms were refined anisotropically while the hydrogen
atoms fixed in the predetermined positions by Shelxs-97 and
Shelxl-97 packages respectively [28]. Crystal data are given in
Table 2.
[16] A. Panda, S. Panda, K. Srivastava, H.B. Singh, Inorg. Chim. Acta 372 (2011) 17e31.
[17] A. Braga, D.S. Ludtke, F. Vargas, R.C. Braga, Synlett 10 (2006) 1453e1466.
[18] C. Santi, S. Santoro, B. Battistelli, Curr. Org. Chem. 14 (2010) 2442e2462.
[19] K.P. Bhabak, G. Mugesh, Acc. Chem. Res. 43 (2010) 1408e1419 (and references
therein).
Acknowledgement
[20] K. Ariga, T. Kunitake, Supramolecular Chemistry-Fundamentals and Applica-
tions, Springer-Verlag, Berlin, Heidelberg, 2006.
[21] D.B. Werz, T.H. Staeb, C. Benisch, B.J. Rausch, F. Rominger, R. Gleiter, Org. Lett.
4 (2002) 339e342.
[22] D.B. Werz, R. Gleiter, F. Rominger, J. Org. Chem. 67 (2002) 4290e4297.
[23] T.H. Staeb, R. Gleiter, F. Rominger, Eur. J. Org. Chem. (2002) 2815e2822.
[24] L. Syper, J. Mlochowski, Tetrahedron 44 (1988) 6119e6130.
[25] S. Panda, S.S. Zade, H.B. Singh, R.J. Butcher, J. Organomet. Chem. (2005)
3142e3148.
SP is thankful to DST (grant no. SR/FT/CS-17/2011). PKD is
thankful to UGC India for fellowship. GRK thanks IISER Kolkata for
fellowship.
Appendix A. Supplementary material
[26] S. Kumar, K. Kandasamy, H.B. Singh, R.J. Butcher, New J. Chem. 28 (2004)
640e645.
[27] Bruker, SADABS V2008e1, Bruker AXS, Madison, WI, USA, 2008.
[28] G.M. Sheldrick, SHELX 97, Program for Crystal Structure Determination,
University of Göttingen, Göttingen, Germany, 1997.
CCDC 867326e867330 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.