K. Senthil et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 124 (2014) 603–610
605
2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium
naphthalene-2-sulfonate (DESNS) 3
using BRUKER instrument operating with 400 MHz, and DMSO
d6 was used as solvent at room temperature. The optical studies
of DESNS crystal were carried out by using ELICO SL 218 double
beam UV–Vis–NIR spectrometer in the wavelength region of
190–1100 nm. Thermal stability studies were carried out with
TG/DTA instrument SBT Q600 apparatus in a nitrogen atmosphere.
The mechanical behavior of DESNS single crystal was tested by
employing MH-112 Micro-hardness instrument with Vickers in-
denter at room temperature.
Compound 2 (3.9g10 mmol) was dissolved in equal volume of
methanol-acetonitrile (40 ml) mixed solvent by heating and simul-
taneously, naphthalene-2-sulfonate (2.3 g 10 mmol) was dissolved
in 20 ml of equal ratio of methanol-Millipore water by heating. The
two hot solutions were mixed and further heated for 2 h at 80 °C
and then mixer was cooled to ambient temperature. The resulting
red color precipitate was filtered off and dried at 120 °C for 3 h to
get free of water. The purity of DESNS was achieved by repeated
recrystallization first from water, and then from methanol for re-
moval of unreacted materials (m.p. 226 °C). Single crystal of title
compounds was grown using slow evaporation technique. Initially,
several organic solvents in pure and mixed forms solvents were
investigated to know the growth habit of a title crystal, solvent
such as methanol, ethanol, acetonitrile, chloroform, methanol–
water, methanol–chloroform, and methanol–acetonitrile were
dried. Finally, only in the combination of methanol–acetonitrile
mixed solvent system was found to be suitable for the crystal for-
mation was observed. A saturated solution of DESNS material was
prepared at room temperature in methanol–acetonitrile (1:1)
mixed solvent, and then solution was stirred continuously to ob-
tain homogeneous medium by using a magnetic stirrer, and fil-
tered the saturated solution into the beaker using Whatman filter
3. Result and discussion
3.1. Single crystal X-ray diffraction analysis
The new structure of DESNS crystal was determined from single
crystal XRD analysis. From the single crystal XRD studies, it shows
that DESNS belongs to the centrosymmetry crystal structure with
orthorhombic crystal system and space group Pbca. Single crystal
data and further details of the crystallography data collection and
structural refinement results are summarized in Table 1. Selected
lengths bond angles which are given in Tables 2 and 3. The
asymmetric unit of the title compound (Fig. 2(a)) consists of a
2-[4-(diethyl amino) styryl]-1-methylpyridinium (C18 H23 N2+)
cation, and a naphthalene sulfonate (C10 H7 O3 Sꢂ) anion molecule.
The packing of the molecule shows partly viewed along the a-axis
as shown in (Fig. 2(b)). The 2-[4-(diethylamino) styryl]-1-meth-
ylpyridinium cation exists in an E configuration with respect to
the C6@C7 double bond [1.334(2) Å]. The cation is slightly twisted,
with the dihedral angle between the C1AC5/N1 pyridinium and
C8AC13 benzene rings being 10.59 (6)°, and it possess trans config-
uration, which can be confirmed from the torsional angle
C5AC6AC7AC8, ꢂ179.61(16)°. The cation and anion are inclined
to each other which indicated by the dihedral angles between the
C17AC22 sulfonated substituted benzene ring of anion and
pyridinium and C8AC13 benzene rings of cation being 54.90 (10)
and 59.90 (10)°, respectively. The two ethyl groups of diethylamino
moiety are slightly twisted from the mean plane of the attached
C8AC13 ring as indicated by the torsion angles C16AN2AC11A
C12 = ꢂ5.21(3)° and C14AN2AC11AC10 = ꢂ9.1(3)°. In the crystal
paper with porosity 0.1 lm. After that beaker was tightly covered
with aluminum foil, and then with few holes to control evapora-
tion rate of the mixed solvent. Small transparent seed crystals were
obtained over in a period of 3 days through spontaneous nucle-
ation. After around 40 days, bulk size of DESNS single crystal with
dimension up to 15 ꢁ 10 ꢁ 9 mm3 (Fig. 1) was harvested by defect
free seed crystal applied to the saturated solution.
2.2. Characterization studies
The grown crystal structure was investigated by single crystal
X-ray diffraction analysis using a Bruker Kappa APEX II diffractom-
eter (Mo Ka = 0.71073 Å). The structure was solved and full matrix
least squares refinement by direct methods using SHELXS97 pro-
grams [17]. The plots of molecular graphics were created with
the PLATON software [18]. The powder X-ray diffraction analysis
were carried out by using BRUKER X-Ray diffractometer with the
Cu Ka radiation (k = 1.5406 Å) in the range of 10–50°, in steps of
0.02°. The FT-IR spectrum was recorded using SHIMADZU IRAFFIN-
ITY instrument in the wavelength range of 400–4000 cmꢂ1 using
the KBr pellet technique. Proton NMR spectrum was recorded
Table 1
Crystal data structure refinement for 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-
pyridinium naphthalene-2-sulfonate (DESNS).
Empirical formula
Formula weight
C28H30N2O3S
474.60
Temperature
298(2) K
Wavelength
0.71073 Å
Crystal system, space group
Unit cell dimentions
Orthorhombic, Pbca
a = 11.5148(3) Å
a = 90°
b = 15.4352(4) Å b = 90°
c = 27.2187(7) Å
4837.7(2) Å3
8, 1.303 Mg/mꢂ3
0.167 mmꢂ1
2016
c = 90°
Volume
Z, Calculated density
Absorption coefficient
F (000)
Crystal size
Theta range for data collection
Limiting indices
0.20 ꢁ 0.18 ꢁ 0.15 mm
2.32ꢂ29.36°
ꢂ15 6 h 6 12, ꢂ21 6 k 6 18, ꢂ37 6 l 6 37
34372/6492 [R (int) = 0.0331]
99.8%
Reflections collected/unique
Completeness to theta = 25.00
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma (I)]
R indices (all data)
None
0.9754 and 0.9674
Full-matrix least-squares on F2
6492/0/310
1.002
R1 = 0.0472, wR2 = 0.1039
R1 = 0.0969, wR2 = 0.1236
0.256 and ꢂ0.266 e Åꢂ3
Largest diff. peak and hole
Fig. 1. Photograph of DESNS crystal grown by slow evaporation.
Senthil
