R. Kavipriya et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 150 (2015) 476–487
477
Table 1
bicarbonate (0.01 mol). This resulted in the formation of slurry of
cyanuric chloride. To this slurry, solution of piperidine
Optimized geometrical structural parameters of DPTA using B3LYP/6-31G(d) method.
a
(0.01 mol) in 5 ml acetone was added. The reaction mixture was
then neutralized by saturated solution of sodium bicarbonate.
The mixture was stirred for 2 h at 0–5 °C. To the resultant product,
a mixture of sodium hydroxide (0.02 mol) and aniline (0.01 mol)
was added slowly. The reaction was continued for 4 h and the pro-
duct obtained was filtered and re-crystallized from ethanol. The
FT-IR spectrum of the compound was recorded in Perkin-Elmer
180 Spectrometer between 4000 and 400 cmꢁ1. The spectral reso-
lution is 2 cmꢁ1. The FT-Raman spectrum of the compound was
also recorded between 3500 and 100 cmꢁ1 in the same instrument
with FRA 106 Raman module equipped with Nd:YAG laser source
operating at 1064 nm line width with 200 mW power. The spectra
were recorded with scanning speed of 30 cmꢁ1 minꢁ1 of spectral
width 2 cmꢁ1. The frequencies of all sharp bands are accurate to
Parameters
Method
XRD
Bond length (Å)
C1–N2
C1–N6
N2–C3
C3–N4
1.380
1.386
1.389
1.389
1.380
1.386
1.413
1.409
1.410
1.414
1.414
1.001
1.001
1.451
1.456
1.415
1.414
1.528
1.394
1.101
1.370
N4–C5
C5–N6
C3–N24
C5–N19
C1–N26
C15–N26
C11–N19
N26–H47
N19–H48
N24–C20
N24–C25
N26–C15
N19–C11
C20–C21
C16–C17
C10–H33
1.007
1.015
1 cmꢁ1
.
1.518
1.383
Quantum chemical calculations
The quantum chemical calculations have been performed at
B3LYP/6-31G(d) basis sets using the Gaussian 03 W program
[16]. The optimized structural parameters have been evaluated
for the calculations of vibrational frequencies by assuming Cs point
group symmetry. At the optimized geometry for the title molecule
no imaginary frequency modes were obtained, therefore a true
minimum on the potential energy surface was found. As a result,
the unscaled calculated frequencies, infrared intensities, Raman
activities and depolarization ratios are obtained. Gauss View
Program [16] has been considered to get visual animation and
for the verification of the normal modes assignment.
Furthermore, in order to show nonlinear optical (NLO) activity of
the title molecule, dipole moment, linear polarizability and first
hyperpolarizability were obtained.
Bond angle (°)
N4–C3–N24
N2–C3–N4
C25–N24–C20
N24–C20–C46
C3–N4–C5
117.83
124.15
116.19
108.96
115.4
124.15
122.3
119.4
119.1
125.6
115.7
108.93
116.12
N2–C3–N4
C1–N26–C15
C12–C7–H35
C5–N19–H48
C11–C12–H36
114.67
120.63
116.6
XRD values are taken from Refs. [14,23].
as automobile paints, reinforced plastics, sheet molding compound
etc., [10–13]. It is also used in the chemical modification of starch,
which leads to products that are capable of removing heavy metal
ions from industrial waste water [14]. Melamine also acts as tri-
dentate ligand. It has been reported that melamine salts like 2,4,
6-triamino-1,3,5-triazine-1-ium chloride hemihydrate exhibit
interesting properties like non-linear optical behavior [15].
Results and discussion
Molecular geometry
The macroscopic properties of the crystals can be better under-
stood from the vibrational behavior like multi photon resonances
and coupling. Hence it is worthwhile to characterize triazine
derivatives with the help of vibrational spectroscopy. In the pre-
sent work, harmonic-vibrational frequencies are calculated for
the N,N0-diphenyl-6-piperidin-1-yl-[1,3,5]-triazine-2,4-diamine(D
PTA) using B3LYP/6-31g(d)method. The calculated spectra of this
molecule are compared to that of experimentally observed FT-IR
and FT-Raman spectra. The HOMO and LUMO analysis have been
used to elucidate information regarding ionization potential (IP),
The optimized structural parameters of the DPTA calculated by
B3LYP/6-31G(d) basis sets are listed in Table 1 and the atom num-
bering scheme is also given in Fig. 1. Since the crystal structure of
the DPTA molecule is not solved till now, the optimized structure
of DPTA is compared withother similarcompoundsfor whichcrystal
structures are solved. It is most often observed that the optimized
bond lengths are slightly larger than the experimental bond lengths,
due to the fact that the theoretical calculations refers to isolated
molecules in gaseous phase but the experimental results represents
molecules in solid state. The optimized geometry of DPTA molecule
determined by B3LYP/6-31G(d) basis sets have the C–N ring bond
distances of 1.380, 1.386, 1.389 and 1.379 Å while the side chain
C–N mean bond distances of 1.414 and 1.409 Å. They are in good
agreement with the ring C–N bond distances determined from the
XRD data values 1.370 Å but the side chain C–N bond distances are
observed at 1.324 Å. The increase in the bond length of C–N is also
interpreted in NBO analysis. The optimized geometrical parameters
represent a good approximation and they form the bases for calcu-
lating other properties like vibrational frequencies and thermody-
namic properties [17,18].
electron affinity (EA), electronegativity ( ), electrophilicity index
v
(x
), hardness ( ), and chemical potential (l). These are confirming
g
the charge transfer within the molecule and also molecular elec-
trostatic potential (MESP) contour map show the various elec-
trophilic region of the title molecule. However, molecular
hyperpolarizability is also calculated by DFT method.
Experimental details
The starting materials required for the preparation of the com-
pound under investigation namely N,N0-diphenyl-6-piperidin-1-y
l-[1,3,5]-triazine-2,4-diamine (C20N6H22) (hereafter it is referred
as DPTA) are purchased from M/S Aldrich Chemicals, (USA) with
spectroscopic grade and it is used as such without any further
purification. A solution of cyanuric chloride (0.01 mol) in 6 ml ace-
tone was added along with stirring to a cold solution of sodium
Vibrational spectral analysis
In our present study, we have performed a frequency calcula-
tion analysis to obtain the spectroscopic details of DPTA. The title
molecule consists of 48 atoms. Therefore they have 138 vibrational