Crystal growth, structure and characterizations of a new semiorganic nonlinear optical material-β-Alanine zinc chloride

Article abstract of DOI:10.1016/j.materresbull.2010.04.020

The title compound, β-alanine zinc chloride-a new semiorganic nonlinear optical crystal was grown by slow evaporation technique. Single crystals of β-alanine zinc chloride have been subjected to X-ray diffraction analysis to determine the crystal structure. The powder X-ray diffractogram of the crystal has also been recorded. The amount of carbon, nitrogen and hydrogen in the crystals was also estimated. Fourier Transform Infrared and Raman spectral measurements have been carried out on the grown crystals in order to identify the functional groups. The presence of hydrogen and carbon in the β-alanine zinc chloride was confirmed by using proton and carbon nuclear magnetic resonance spectral analyses. The percentage of zinc in the crystal was determined by atomic absorption spectroscopy. Optical behavior such as ultraviolet-vis-near infrared transmittance spectrum and second harmonic generation has been investigated. The mechanical strength and thermal behavior of the grown crystal have been analyzed.

Full text of DOI:10.1016/j.materresbull.2010.04.020

Materials Research Bulletin 45 (2010) 897–904
Contents lists available at ScienceDirect
Materials Research Bulletin
journal homepage: www.elsevier.com/locate/matresbu
Crystal growth, structure and characterizations of a new semiorganic nonlinear
optical material—
b
-Alanine zinc chloride
a
b,
b
c
M. Anbuchezhiyan , S. Ponnusamy *, C. Muthamizhchelvan , K. Sivakumar
a
Department of Physics, Valliammai Engineering College, S.R.M. Nagar, Kattankulathur, Chennai 603203, India
b
Centre for Material Science and Nano Devices, Department of Physics, SRM University, Kattankulathur, Kanchipuram, Chennai 603203, India
Department of Physics, Anna University, Chennai 600 025, India
c
A R T I C L E I N F O
A B S T R A C T
Article history:
The title compound,
b
-alanine zinc chloride—a new semiorganic nonlinear optical crystal was grown by
-alanine zinc chloride have been subjected to X-ray
Received 18 June 2009
slow evaporation technique. Single crystals of
b
Received in revised form 20 December 2009
Accepted 21 April 2010
diffraction analysis to determine the crystal structure. The powder X-ray diffractogram of the crystal has
also been recorded. The amount of carbon, nitrogen and hydrogen in the crystals was also estimated.
Fourier Transform Infrared and Raman spectral measurements have been carried out on the grown
Available online 29 April 2010
crystals in order to identify the functional groups. The presence of hydrogen and carbon in the b-alanine
Keywords:
zinc chloride was confirmed by using proton and carbon nuclear magnetic resonance spectral analyses.
The percentage of zinc in the crystal was determined by atomic absorption spectroscopy. Optical
behavior such as ultraviolet–vis–near infrared transmittance spectrum and second harmonic generation
has been investigated. The mechanical strength and thermal behavior of the grown crystal have been
analyzed.
A. Optical properties
A. Organometallic compounds
B. Crystal growth
C. X-ray diffraction
D. Crystal structure
ß 2010 Elsevier Ltd. All rights reserved.
1
. Introduction
Significant advances have been made recently in the field of
acids are also very interesting system for fundamental research as in
the crystalline state they are present as zwitterions. Inorganic
crystals exhibit shortcoming as nonlinear materials due to difficulty
in synthesizing, lack of optical quality and slow electro-optic
response time. Although organic materials like urea exhibit very
high second harmonic generation responses in powder forms, they
cannot be used in practical device because they lack mechanical
strength, dimensional and thermal stability.
A category of organometallic and coordination compounds has
attracteda considerable interest inrecent years inthe searchfornew
NLOmaterials due totheir advantages overtraditional inorganic and
nonlinear optics (NLO) in the area of materials engineering and the
associated optoelectronic device technologies. NLO is now estab-
lished as an alternative field to electronics for future photonic
technologies. The fast growing development in the optical fiber
communication systems has stimulated the search for new NLO
materials that are capable of fast and efficient processing of optical
signals and integrated optics [1]. Researchers are always in the
search of new materials and their single crystal growth. From the
stand-point of the search for newer NLO materials, amino acids offer
a rich choice [2–4]. Amino acids are bifunctional organic molecules
that contain a carboxyl group (–COOH) as well as an amino group (–
organic compounds. Thus
been exploited for the formation of salts with different organic or
inorganic materials [5–11]. In -( )-alanine, the amino group is
attached to the second carbon atoms in the carbon chain whereas in
-alanine the amino group is attached to the third carbon atom.
)-Alanine is naturally occurring amino acid while -alanine is
purely synthetic amino acid. -( )-Alanine has two sterioisomeric
forms but -alanine has only one form. -Alanine, a positional
isomer of -alanine, isnota constituentof proteinsor enzymes, but is
L-arginine, L-histidine and L-alanine have
L
a
NH
group (NH
2
). In the solid state, amino acids contain a protonated amino
+
3
ꢀ
) and de-protonated carboxylic acid group (COO ). This
b
L-
dipolar nature exhibits peculiar physical and chemical properties in
amino acid which makes them an ideal candidate for NLO
application. Except glycine, all naturally occurring amino acids
are chiralspecies, crystallizinginnon-centrosymmetryspace group,
which is one of an essential criterion for NLO applications. Amino
(a
b
L
a
b
b
L
a component of a very few naturally occurring peptides like
carnosine and anserine, and also of pantothenic acid (vitamin B5)
[12]. It also forms crystalline complexes with organic and inorganic
acids or materials. -Alanine single crystal is also a sensitive
b
*
Corresponding author. Fax: +91 44 27456255.
target for weak electromagnetic fields; it has NLO properties [13].
In these series, we have successfully grown a potential semiorganic
E-mail addresses: suruponnus@gmail.com, sponnusamy@sancharnet.in
(
S. Ponnusamy).
0025-5408/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.materresbull.2010.04.020

8
98
M. Anbuchezhiyan et al. / Materials Research Bulletin 45 (2010) 897–904
b-alanine zinc chloride single crystal that has NLO properties and
could be used in optoelectronics.
In the present work, the title compound has been synthesized
by slow evaporation method and the grown crystal was
characterized by single crystal and powder X-ray diffractogram
(XRD) analyses, Fourier Transform Infrared (FTIR) and FT Raman
spectra, FT NMR studies, atomic absorption spectroscopy (AAS),
CHN analysis, UV–vis–NIR spectrum, second harmonic generation
(SHG) studies, Vickers microhardness and thermal analysis such as
thermogravimetry (TG), differential thermal analysis (DTA) and
differential scanning calorimetry (DSC).
2
. Experimental procedure
2.1. Synthesis and growth
The
b
-alanine zinc chloride crystals were grown by using
-Alanine and zinc chloride procured
solution growth technique.
b
from LOBA (AR grade, 99% purity) were used for the growth of the
crystals. A mixture of triple distilled water and acetone taken in the
ratio 1:1 was used as a solvent. Calculated amounts of
b-alanine
and zinc chloride were dissolved in the solvent according to the
stoichiometric ratio (1:1) as shown by the Eq. (1).
C
3
H
7
NO
2
þ ZnCl
2
! C
3
H
7
NO
2
ZnCl
2
(1)
The solution is maintained at the temperature of 35 8C. The stirring
of the mixture was carried out for 8 h. Then it is allowed to stand
for an hour. It is filtered using a micro filter paper (10
mm) to
remove any insoluble impurities. It was then transferred to a
beaker. The beaker was optimally closed using a perforated thin
polyethylene sheet and was kept in a constant temperature bath
equipped with EUROTHERM temperature controller of accuracy
Fig. 1. Photograph of the as grown crystals of b-AZC.
ꢀ
1
100 cm . Nd-YAG laser source of wave length 1064 nm and
InGaAs detector were used in FT Raman measurement. In the
ꢁ
0.01 K. The temperature was maintained at 35 8C and solvent
was allowed to evaporate spontaneously. Crystals appeared after a
1
13
present investigation, the H NMR and C NMR spectra of the
AZC have been recorded with a JEOL-GSX400 NMR Spectrometer
operating at 400 MHz with deuterated chloroform CDCl as
solvent. To determine the optical transmittance range and hence
to know the suitability of -AZC single crystals for optical
b-
period of 1 month. The grown crystals of b-alanine zinc chloride
(
abbreviated as b-AZC) are shown in Fig. 1.
3
2.2. Characterizations studies
b
applications, the UV–vis–NIR transmittance spectrum has been
recorded using a Varian Cary 5E UV–vis–NIR spectrophotometer in
the range of 200–2500 nm covering the entire UV, visible and NIR
region. Kurtz and Perry powder method was employed to check the
In order to study the crystal structure of
b-AZC, the X-ray
diffraction intensity data for
a perfect crystal (0.22 mm
ꢂ 0.16 mm ꢂ 0.16 mm) was measured at 293 K on a Bruker AXS
˚
Kappa Apex II diffractometer with Mo K
a
radiation
l
= 0.71073 A.
SHG efficiency of b-AZC crystal. Vickers microhardness of the
The
v
: 2
u
scan technique was employed to measure 11281
= 37.438 out of which 3172 reflections were
material was measured by using the REICHERT MD 4000 E Ultra
microhardness tester fitted with a Vickers diamond pyramidal
indenter attached to a REICHERT POLYVAR 2 MET microscope.
reflections up to
u
unique. The data were corrected for absorption employing a semi-
empirical correction. The crystal structure was solved by direct
methods and refined by a Full-matrix least-squares procedure based
on F(0 0 0) employing 3172 reflections. SHELXS-97 and SHELXL-97
were applied [14,15]. The refinement was continued until the final
deviationfactors, Rand wR were0.0616and 0.2095respectively. The
TGA–DTA and DSC for b-AZC have been recorded using a SDT Q 600
V8.2 BUILD 100. The analysis was carried out in an atmosphere of
nitrogen at a heating rate of 20 8C/min for the temperature range of
30–1000 8C.
b-AZC single crystal was subjected to powder X-ray diffraction
3. Results and discussion
studies with a high resolution PANalytical X’ Pert PRO. Finely ground
powder of the crystals was subjected to intense X-rays of
˚
3.1. Single crystal and powder X-ray diffraction analysis
From the single crystal X-ray diffraction analysis, it is found that
wavelength
l = 1.5406 A with a scan speed of 0.048 per second.
The sample was scanned over the range of (2u) 10–808.
The percentage of zinc in the grown crystal was determined by
GBC Avanta Atomic Absorption Spectrophotometer. CHN analyses
were carried out using Vario EL III analyzer. To understand the
chemical bonding and molecular structure of the compound, FTIR
and FT Raman spectra were recorded. FTIR spectrum was recorded
by using PERKIN ELMER SPECTRUM I Spectrophotometer in the
the
b-AZC crystallizes under orthorhombic system with lattice
˚
˚
˚
parameters a = 6.9371 A, b = 12.918 A, c = 7.9596 A,
and volume of the unit cell V = 713.3 A . The space group is Pna2
Density of the
a
=
b
=
g
= 908
3
˚
1
.
3
b-AZC is 2.099 g/cm and Z = 4. A summary of the
crystallographic data is given in Table 1. The molecular structure of
b
-AZC is represented in Fig. 2. The projection of crystal structure of
ꢀ1
region of 4000–400 cm
employing KBr pellet technique. FT
b
-AZC crystal (along the a-axis) is shown in Fig. 3. The selected
Raman spectrum has been recorded using Thermo electron
corporation USA Nexus 670 spectrometer in the range 3701–
bond distance and bond angles are listed in Table 2. The data
related to the hydrogen bonds of -AZC are presented in Table 3.
b

M. Anbuchezhiyan et al. / Materials Research Bulletin 45 (2010) 897–904
899
Table 1
Crystal data and structure refinement for
b
-AZC.
Cl NO
225.37
293(2) K
Empirical formula
Formula weight
C
3
H
7
2
2
Zn
Temperature
´
Wavelength
0.71073 A˚
Orthorhombic, Pna2
a = 6.9371(14) A˚ ;
Crystal system, space group
Unit cell dimensions
1
´
a
b
g
= 908
=908
= 908
´
b = 12.918(3) A˚ ;
c = 7.9596(16) A˚ ;
´
´
3
Volume
713.3(2) A˚
4, 2.099 g/cm
3
Z, calculated density
Absorption coefficient
F(0 0 0)
ꢀ
1
4.116 mm
448
Crystal size
0.22 mm ꢂ 0.16 mm ꢂ 0.16 mm
3.01–37.438
ꢀ11 ꢃ h ꢃ 10, ꢀ22 ꢃ k ꢃ 22, ꢀ10 ꢃ l ꢃ 13
11281/3172 [R(int) = 0.0275]
95.7%
Theta range for data collection
Limiting indices
Reflections collected/unique
Completeness to theta = 37.43
Max. and min. transmission
Refinement method
Data/restraints/parameters
Fig. 2. Molecular structure of
b-AZC.
0.5588 and 0.4646
2
Full-matrix least-squares on F
distances N. . .Cl1, N. . .Cl2, N. . .O1 and N. . .O2 indicate the
presence of hydrogen bonding.
3172/1/84
2
Goodness-of-fit on F
1.115
Final R indices [I > 2 sigma (I)]
R indices (all data)
R1 = 0.0616, wR2 ¼ 0:2095
R1 = 0.0649, wR2 ¼ 0:2172
0.51(5)
All the H-atoms were placed in calculated positions and were
˚
allowed to ride on their respective parent atoms with N–H = 0.89 A
Absolute structure parameter
Extinction coefficient
˚
and C–H = 0.97 A. The C–O–Zn bond angle values are 114.2(5)8 and
0.139(12)
3.308 and ꢀ2.540e. A˚ ꢀ3
153.7(6)8. The O–C–O bond angle value of 124.0(5)8 is practically
Largest diff. peak and hole
identical to the non-protonated carboxyl group of pure
24.58. All the bond lengths and bond angles of -alanine in the
AZC crystal are similar to those in other -alanine complexes
b-alanine
1
b
b-
The molecular structure shows that the carboxylic acid group of
b
+
3
b
-alanine protonate the amino group to NH
. The zinc atoms bind
[12,13]. The O–C bond lengths being within the range of 1.248(7)–
˚
1.258(9) A, agree well with the corresponding values found in b-
ꢀ
to four chlorine atoms and two oxygen atoms from the COO of the
+
b
-alanine molecules in a distorted octahedral environment. Four
alanine [16] and other alanine complexes [12,13]. NH
3
groups of
Cl atoms coordinate to a Zn atom, forming a square plane. It is not a
perfect square as seen from Cl–Zn–Cl bond angles which are not
the -alanine act as proton donor forming three N–H. . .O hydrogen
b
˚
bond with N. . .O distances in the range of 2.719(10)–3.30(2) A and
two N–H. . .Cl hydrogen bonds with distances in the range of
9
08 expected for a perfect square. These square planes extend
infinitely along the shortest axis ‘a’. These square planes are shared
by the carboxyl atoms, which complete the octahedral
coordination around the Zn atom. The octahedran is shared by
the carboxyl group of the -alanine molecule and fuses directly by
˚
3.161–3.234 A. The Zn–Cl bond lengths are within the range of
˚
O
2.601–2.638 A. The Zn–O bond lengths are in the range of 2.268–
˚
2.333 A and matches well with the other alanine complexes [17].
b
From the structural study it is clear that all the Zn atoms are in a
distorted octahedral environment.
sharing Cl–Cl edges to form one dimensional chains in the [1 0 0]
direction. The metal–ligand coordination observed in Fig. 2 is
remarkably similar to those observed in the crystal structures of
The powder XRD data have been indexed using CELREF program
˚
and the lattice parameters are evaluated as: a = 6.9364 A,
3
˚
˚
˚
CdCl
2
with
L
-alanine and CdCl
2
with
b
-alanine [12]. The interchain
b = 12.9251 A, c = 7.9581 A, a = b = g = 908 and V = 713.4 A . The
Fig. 3. Projection crystal structure of
b-AZC crystal.

9
00
M. Anbuchezhiyan et al. / Materials Research Bulletin 45 (2010) 897–904
Table 2
Bond lengths [ A˚ ] and angles (degree) for
b-AZC crystal.
Bond lengths [ A˚ ]
Zn(1)–O(1)
Zn(1)–O(2)
Zn(1)–Cl(2)
Zn(1)–Cl(1)
Zn(1)–Cl(2)#1
Zn(1)–Cl(1)#1
Cl(1)–Zn(1)#2
Cl(2)–Zn(1)#2
O(1)–C(1)
2.268(5)
2.333(5)
2.601(2)
2.616(3)
2.625(3)
2.638(3)
2.638(3)
2.625(3)
1.258(9)
1.248(7)
1.540(14)
1.248(7)
1.519(7)
1.561(11)
O(2)–C(1)#2
N(1)–C(3)
Fig. 4. Indexed powder XRD pattern for
b-AZC.
C(1)–O(2)#1
C(1)–C(2)
C(2)–C(3)
3.3. FTIR and FT Raman spectral analysis
Bond angles (degree)
O(1)–Zn(1)–O(2)
171.2(2)
85.7(4)
To understand the chemical bonding and material confirmation
O(1)–Zn(1)–Cl(2)
O(2)–Zn(1)–Cl(2)
O(1)–Zn(1)–Cl(1)
O(2)–Zn(1)–Cl(1)
Cl(2)–Zn(1)–Cl(1)
O(1)–Zn(1)–Cl(2)#1
O(2)–Zn(1)–Cl(2)#1
Cl(2)–Zn(1)–Cl(2)#1
Cl(1)–Zn(1)–Cl(2)#1
O(1)–Zn(1)–Cl(1)#1
O(2)–Zn(1)–Cl(1)#1
Cl(2)–Zn(1)–Cl(1)#1
Cl(1)–Zn(1)–Cl(1)#1
Cl(2)#1–Zn(1)–Cl(1)#1
Zn(1)–Cl(1)–Zn(1)#2
Zn(1)–Cl(2)–Zn(1)#2
C(1)–O(1)–Zn(1)
of the compound, FTIR and FT Raman spectra have been recorded.
The structure of the above compound expected is as shown below.
87.3(3)
91.8(3)
82.4(4)
þꢀCH
ꢀ
NH
3
2
ꢀCH
2
ꢀCOO ZnCl
2
86.57(6)
101.0(3)
84.7(4)
The FTIR and FT Raman spectra are presented in Fig. 5(a) and (b)
respectively. Vibrational band assignment of -AZC was based on
92.67(10)
167.17(12)
107.3(4)
79.6(3)
b
the results of a previous study on interpretation of the vibrational
spectra of alanine and its complexes [18–23]. The vibrational
frequency of various functional groups of
b-AZC and the tentative
166.93(12)
92.19(14)
85.65(6)
83.91(8)
84.46(8)
114.2(5)
153.7(6)
124.0(5)
115.3(5)
120.7(5)
112.0(6)
107.0(7)
frequency assignment are presented in Table 5. On examining the
b
-
ꢀ1
ꢀ1
AZCspectra,itisobservedthata1609 cm inFTIRand1607 cm in
ꢀ
FT Raman are due to COO asymmetric stretching. The presence of
+
ꢀ1
torsion oscillation of NH
medium intensity band observed at 1130 cm and strong band at
3
is evident from the peak at 527 cm . The
ꢀ1
C(1)#2–O(2)–Zn(1)
O(2)#1–C(1)–O(1)
O(2)#1–C(1)–C(2)
O(1)–C(1)–C(2)
ꢀ1
+
1258 cm in the FTIR spectrum could be assigned to NH
3
rocking
vibration. The same vibration appears in the FT Raman spectrum at
ꢀ1
ꢀ1
with very weak intensity. The CH
1133 cm
and 1260 cm
2
C(1)–C(2)–C(3)
symmetric stretching vibrations are observed in and around
N(1)–C(3)–C(2)
ꢀ
1
ꢀ1
2
932 cm in the FTIR and 2933 cm in the FT Raman spectrum.
Symmetry transformations used to generate equivalent atoms: #1 x ꢀ 1/2,ꢀy + 3/
,z; #2 x + 1/2,ꢀy + 3/2,z.
ꢀ1
The asymmetric stretching of CH
2
is observed at 2994 cm in the FT
2
Ramanspectrum. SeveralmethylenevibrationsobservedinFTIR and
ꢀ
1
ꢀ1
ꢀ1
FT Raman are: 1442 cm and 1457 cm (scissoring), 1330 cm
ꢀ ꢀ1 ꢀ1
1
calculated lattice parameters from the powder XRD analysis are in
good agreement with the single crystal X-ray analysis. The indexed
powder XRD pattern is shown in Fig. 4 and indexed powder XRD
data are presented in Table 4.
and 1335 cm (wagging), and 1303 cm and 1305 cm (twist-
ꢀ1
ꢀ1
ing). The band observed at 1044 cm and 1080 cm are attributed
to CN symmetric and antisymmetric stretching respectively. The
ꢀ
1
ꢀ1
strong absorption bands at 3199 cm
and 3073 cm
asymmetric and symmetric
stretching respectively. In the FT Raman the very weak band at
in FTIR
+
3
spectrum indicate the presence of NH
3
.2. CHN analysis
ꢀ1
+
3
3
175 cm is also assigned to NH asymmetric stretching. The Zn–
Cl stretching vibrational frequency is assigned to 296 cm from FT
Raman spectrum. This is in consistent with Zn–Cl stretching mode
at290 cm reportedbyBalakrishnanand Ramamurthy [24]. A band
at 219 cm in FT Raman is assigned to stretching vibration of the
Zn–O bond.
ꢀ
1
Thepercentageofcarbon,hydrogenandnitrogenwasdetermined
by CHN analyzer. The observed data are carbon, 16.0%; hydrogen,
.077%; nitrogen, 6.181%. The calculated values are carbon, 15.98%;
hydrogen, 3.13%; nitrogen, 6.21%. They are in good agreement with
each other indicating the formation of the titled compound.
ꢀ
1
3
ꢀ1
Table 3
3.4. FT NMR Studies
Hydrogen bonding parameters for
b-AZC crystal.
1
13
D–H. . .A
D–H ( A˚ )
H. . .A ( A˚ )
D. . .A ( A˚ )
D–H. . .A
degree)
The H NMR and C NMR spectralanalysis are the two important
modern analytical techniques used for the study of the structure of
organic compounds. The spectra are presented in Fig. 6(a) and (b)
respectively. In the adduct formed between 3-amino propionic acid
(
a
N1
N1
N1
N1
N1
C3
H1A
H1B
H1B
H1C
H1C
H3A
O1
0.8900
0.8900
0.8900
0.8900
0.8900
0.9700
2.4500
2.6400
2.4800
2.4900
2.0700
2.6800
3.187(10)
3.161(10)
3.30(2)
141.00
119.00
152.00
141.00
128.00
131.00
b
a
d
Cl2
b
1
O1
and zinc chloride, there are two pairs of methylene protons in the H
NMR spectrum. One methylene carbon is directly bonded to
carboxyl group and the other to the amino group. In this compound,
the amino group gets protonated to give ammonium group (–NH
This appears as a three proton singlet downfield at 4.643 ppm. There
are two triplets at 3.0178 ppm and 2.431 ppm. The downfield signal
isduetothehydrogenatomsofthemethylenedirectlybondedtothe
Cl1
3.234(10)
2.719(10)
3.402(11)
c
O2
Cl1
+
3
).
a
1
1
+ x,y,z.
ꢀ x,ꢀy,ꢀ1/2 + z.
b
c
1
/2 + x,1/2 ꢀ y,z.
d
1
/2 ꢀ x,ꢀ1/2 + y,1/2 + z.

M. Anbuchezhiyan et al. / Materials Research Bulletin 45 (2010) 897–904
901
Table 4
Indexed powder XRD data for
b-AZC crystal.
h
k
l
d (obs) ( A˚ )
d (cal) ( A˚ )
d (diff) ( A˚ )
2u
(obs) (degree)
2u
(cal) (degree)
Intensity
Relative
intensity (%)
0
0
0
0
1
0
1
2
0
2
1
0
3
0
0
1
1
0
1
3
1
0
2
1
0
0
2
1
0
1
0
3
1
4
0
2
3
4
5
0
1
2
0
3
3
4
2
2
5
3
5
3
2
0
7
6
5
4
3
9
6.77633
6.46245
3.97903
3.78870
3.65990
3.23128
3.04449
2.85283
2.58503
2.55823
2.42231
2.25885
2.09984
1.98950
1.84643
1.82745
1.78872
1.69415
1.45957
1.21995
6.77657
6.46255
3.97903
3.78876
3.65985
3.23127
3.04447
2.85283
2.58502
2.55822
2.42228
2.25886
2.09984
1.98951
1.84644
1.82745
1.78873
1.69414
1.45956
1.21995
ꢀ0.00024
ꢀ0.00010
0.00000
13.054
13.691
22.324
23.461
24.299
27.582
29.311
31.329
34.672
35.047
37.083
39.876
43.040
45.557
49.312
49.859
51.015
54.087
63.706
78.307
13.054
13.691
22.324
23.461
24.299
27.582
29.311
31.329
34.672
35.047
37.084
39.876
43.040
45.557
49.312
49.859
51.015
54.087
63.706
78.307
1929
196
193
327
163
82
100
10.18
10.01
16.99
8.46
4.27
8.16
1.47
12.53
22.27
2.31
7.06
1.38
10.13
12.07
4.74
2.50
2.06
2.41
3.93
ꢀ0.00006
0.00005
0.00001
0.00001
157
28
0.00000
0.00002
24
0.00001
429
45
0.00004
ꢀ0.00001
ꢀ0.00001
ꢀ0.00001
ꢀ0.00001
ꢀ0.00000
ꢀ0.00001
ꢀ0.00001
0.00001
136
27
195
233
91
48
40
47
ꢀ0.00001
76
+
13
–
NH
3
group. This is explained by the electron attracting power of
In C NMR spectrum, the two signals, one at 36.6 and the other
at 33.12 ppm indicate the presence of two methylene carbon
atoms. The carbon atom of the carboxyl group appears at
178.713 ppm. The carboxyl carbon is known to be much
deshielded so as to give signal at 178.713 ppm [13].
the ammonium group. The high field signal is for the proton of the
methylene attached to the carboxyl group. The signals for the two
methylene protons are in fact two sets of triplets, which can be
explained by the splitting due to the two adjacent methylene
protons.
3.5. Atomic absorption spectroscopy (AAS)
The presence of metal elements in the grown (b-AZC) crystal
was confirmed by atomic absorption spectroscopy (AAS). The
calculated and experimentally determined amounts of zinc in the
crystal are 29% and 28.7% respectively which are very close to
each other. This confirms the presence of zinc in the grown
crystal.
Table 5
Vibrational band assignments for
b-AZC crystal.
ꢀ1
Wave number (cm
FTIR
)
Band assignments
FT Raman
–
219 (vw)
296 (vs)
434 (w)
527 (w)
–
Zn–O stretch
Zn–Cl stretch
–
4
5
6
6
8
8
8
9
34 (m)
27 (m)
19 (w)
91 (m)
28 (vs)
41 (vs)
75 (m)
50 (s)
C–C–N–C bend
+
NH
3
torsion
ꢀ
COO deformation
ꢀ
–
COO deformation
828 (w)
843 (vw)
863 (m)
935 (w)
1044 (vw)
1081 (m)
1133 (vw)
1260 (m)
1305 (vw)
1335 (m)
1393 (w)
–
CC stretch
CC stretch, CN stretch
CC stretch
CN sym. stretch,
CN sym. stretch
1
1
1
1
1
1
1
1
1
1
1
2
044 (s)
080 (vs)
130 (m)
258 (s)
303 (s)
330 (vs)
393 (vs)
418 (vs)
442 (vs)
576 (vs)
609 (vs)
932 (s)
–
CN asym. stretch
+
NH
NH
3
rocking
rocking
+
3
CH
CH
CH
2
twisting
wagging
2
2
deformation
ꢀ
COO sym. stretch
1457 (m)
1578 (vw)
1607 (vw)
2933 (vs)
2974 (vs)
2
CH scissoring
+
NH
3
sym. deformation
ꢀ
COO asym. stretch
CH
CH
CH
2
2
2
sym. stretch
sym. stretch
asym. stretch
2994 (vs)
+
3
073 (vs)
199 (vs)
3026 (m)
NH
NH
3
sym. stretch
asym. stretch
+
3
3175 (vw)
3
Fig. 5. (a) FTIR Spectrum of
b-AZC. (b) FT Raman Spectrum of
b-AZC.
vw—very weak; w—weak; m—medium; s—strong; vs—very strong.

9
02
M. Anbuchezhiyan et al. / Materials Research Bulletin 45 (2010) 897–904
and UV spectral regions. The lower cut off at 200 nm combined
with very good transparency attests the usefulness of this material
for optoelectronics.
3.7. SHG studies
Kurtz [26] second harmonic generation (SHG) efficiency of the
crystalline material was determined by using Q-switched Nd-YAG
laser beam of = 1064 nm. The output from the sample was
collected by using a monochromator to collect the intensity of
32 nm component and to eliminate the fundamental. The
l
5
generation of second harmonic was focussed by a lens and
detected by the photomultiplier tube. The generation of the second
harmonic was confirmed by the emission of green light (532 nm). A
sample of potassium dihydrogen phosphate (KDP), also powdered
to the same particle size as the experimental sample, was used as
reference material in the SHG measurement. The measured
amplitude of second harmonic green light for
b-AZC is 20 mV as
against 28 mV for KDP crystal. The SHG conversion efficiency of the
title compound is found to be 0.71 times that of standard KDP
crystal. Hence
that of -alanine (0.2),
arginine formate (0.3), glycine zinc chloride (0.5) and
acetate (0.3) [27]. The laser damage threshold value of the
crystal is found to be 1.56 GW/cm . This value is higher than that of
KDP and urea [28].
b
-AZC SHG efficiency is comparatively greater than
-arginine tetrafluoroborate (0.54),
-alanine
-AZC
L
L
L-
L
b
2
3.8. Vickers microhardness test
The microhardness studies were carried out on the grown
crystals of b-AZC using Vickers microhardness tester attached with
Fig. 6. (a) Proton NMR of
b-AZC. (b) Carbon NMR of
b-AZC.
an optical microscope. Vickers microhardness number was
evaluated from the relation:
3
.6. UV–vis–NIR absorption Studies
1
:8544P
2
H
v
ðkg=mm Þ ¼
(2)
2
d
To determine the optical transmission range and hence to know
the suitability of -AZC single crystals for optical applications, the
b
where ‘H ’ is the Vickers microhardness number, ‘P’ is the applied
v
UV–vis–NIR transmittance spectrum has been recorded in the
range of 200–2500 nm covering the entire UV, visible and NIR
region. The crystal shows a good transmittance in the visible
region. The absorption at 976 nm can be attributed to vibrational
overtone [25]. The absorption above 976 nm falls in the near IR
region. It can be seen from the transmission spectrum (Fig. 7) that
the lower cut off wavelength lies at 200 nm, and there is no
significant absorption in the range of 200–920 nm. This is an
advantage of the use of amino acids where the absence of strongly
conjugated bonds leads to wider transparency ranges in the visible
load and ‘d’ is the diagonal length of the indentation impression. To
evaluate the Vickers hardness, several indentations were made on
the (1 0 0) face of the crystal. The diagonal length of the indentations
was measured using a micrometer eyepiece. Dependence of the
microhardness on the load for
shown in Fig. 8. Loads of different magnitudes (25 g, 50 g, 75 g, and
100 g) were applied on the -AZC crystal for the fixed interval of
indentation time of 5 s. Hardness is found to increase as the load is
b-AZC crystal has been evaluated and
b
Fig. 7. UV–vis–NIR transmittance spectrum of
b-AZC.
Fig. 8. Plot of load (vs.) hardness for b-AZC crystal.

M. Anbuchezhiyan et al. / Materials Research Bulletin 45 (2010) 897–904
903
increased and attains the maximum value at 100 g, when it is found
tobe174.5 kg/mm . Attheloadabove100 g, crackswereinitiatedon
the crystal surface around the indenter. The better mechanical
NH
3
. The mixture of CO, C
2
H
4
, and part of ZnCl
2
also evolved in the
2
temperature range from 464 8C to 563 8C. The fourth stage of
decomposition in the range of 563 8C to 748 8C involves the
properties of
alanine and zinc. This implies that
engineering material for device fabrication.
b
-AZC are due to the strong bonding between the
evolution of CO
which may be considered to be the compounds of zinc. From the
above analysis, the melting point of the -AZC crystal is 224 8C,
which is higher than the other semi organic materials like -alanine
cadmium chloride (110 8C), -proline cadmium chloride mono-
2
. The actual residual amount of mass is 10.07%
b-AZC single crystal is a good
b
L
3.9. Thermal analyses
L
hydrate (210 8C) and dichloridodiglycine zinc dihydrate (103 8C)
The TG–DTA and DSC traces of
b
-AZC are presented in Fig. 9(a)
[29–31].
and (b). An initial mass of 1.7970 mg was used for analysis and the
final mass left out after the experiment was only 10.07% of the
initial mass at a temperature of about 1000 8C indicating the bulk
decomposition occurring in the sample.
4. Conclusions
A potential new semiorganic second order nonlinear optical
From the TG–DTA curves, it is observed that the material starts
melting and undergoes an endothermic transition without mass
change at about 224 8C till the temperature of 242 8C. At 242 8C, a
different phase appears up to 264 8C. Again another endothermic
process takes place from 264 8C to 346 8C with a mass change. The
other endothermic peaks between 464 8C and 748 8C indicate the
decomposition of the material. In the DSC curve there is a sharp
endothermic peak starting at 224 8C and going up to 242 8C, this
indicate that there is no phase transition up to 242 8C. The melting
point of the grown crystal is 224 8C. From the TG curve, the mass
loss is found to take place after the temperature of 264 8C. The mass
lost from 264 8C to 346 8C is found to be 32.67% which is the
sublimation of the Cl. There is further mass loss of 9.2% occurring in
the temperature limit of 346–464 8C which involve the evolution of
material
technique. From the structural study, it is found that the
zinc chloride crystallizes under non-centrosymmetric orthorhom-
bic system with space group Pna2 . The lattice parameters
evaluated from the powder X-ray diffraction are in good agreement
with that of the single crystal analysis. The presence of the Zinc
metal is determined using atomic absorption spectroscopy. The
b
-alanine zinc chloride was grown by slow evaporation
b
-alanine
1
presence of carbon, hydrogen, and nitrogen in
b-alanine zinc
chloride has been determined by elemental analysis. The
spectroscopic analyses confirm the functional group of the grown
b
-alanine zinc chloride. The Vickers microhardness values
measured on -alanine zinc chloride indicates high mechanical
b
strength. The ultraviolet–visible transmittance analysis shows that
the material does not absorb appreciably in the range of 200–
920 nm thus confirming the suitability of this material for second
harmonic generation applications. The powder second harmonic
generation efficiency is about 0.71 times that of potassium
dihydrogen phosphate. The thermogravimetric–differential ther-
mal analysis studies establish that the compound is stable up to its
melting point. Differential scanning calorimetry shows that the
melting point of the grown crystal is 224 8C. The thermal study has
established its suitability to withstand the high temperature
encountered in laser experiments.
5. Supplementary material
CCDC 734356 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/data_request/cif or by Emailing
data_request@ccdc.cam.ac.uk or by contacting the Cambridge
Crystallographic Data Centre 12, Union Road, Cambridge CB2 1EZ,
UK [Fax: +44 (0) 1223 336033].
Acknowledgements
The authors express their sincere thanks to Dr. S. Ganesan, Anna
University, Chennai and Dr. P.K. Das, IISc, Bangalore for SHG
studies, The Head, SAIF, IIT, Chennai, The Head, ICP section, CECRI,
Karaikudi for other characterizations and Dr. Charles C. Kanagam,
Valliammai Engineering College for useful discussions. The authors
also thank Dr. P.K. Datta, Department of Physics and Meteorology,
Indian Institute of Technology, Kharagpur 721 302, India, for the
measurement of laser damage threshold study.
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