(2E)-1-[2,3-Dichloro-6-methyl-5-(trifluoro­meth­yl)phen­yl]-2-(1-phenyl­ethyl­idene)hydrazine

Fun, H.-K.; Loh, W.-S.; Bhat, M.; Arulmoli, T.; Nagaraja, G.K.

doi:10.1107/S1600536812042419

organic compounds

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ISSN: 2056-9890

Volume 68| Part 11| November 2012| Page o3189

doi:10.1107/S1600536812042419

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(2E)-1-[2,3-Dichloro-6-methyl-5-(trifluoromethyl)phenyl]-2-(1-phenylethylidene)hydrazine

Hoong-Kun Fun,^a,^b ^*‡ Wan-Sin Loh,^a § Manjunath Bhat,^c,^d T. Arulmoli ^c and G. K. Nagaraja ^d

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, ^bDepartment of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, PO Box 2457, Riyadh 11451, Saudi Arabia, ^cSequent Scientific Limited, Baikampady, Karnataka, India, and ^dDepartment of Chemistry, Mangalore University, Mangalagangothri, Mangalore 574 199, India
^*Correspondence e-mail: hkfun@usm.my

(Received 28 September 2012; accepted 10 October 2012; online 20 October 2012)

The title compound, C₁₆H₁₃Cl₂F₃N₂, exists in an E conformation with respect to the C=N bond [1.2952 (11) Å] and the C—N—N=C torsion angle is 175.65 (8)°. The dihedral angle between the benzene rings is 42.09 (4)°. An intramolecular C—H⋯F hydrogen bond generates an S(6) ring. In the crystal, the molecules are linked into [101] chains by C—H⋯F hydrogen bonds.

Related literature

For background to the properties and applications of hydrazones, see: Barbazan et al. (2008 ); Banerjee et al. (2009 ); Ghavtadze et al. (2008 ). For related structures, see: Fun et al. (2011a ,b ). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₁₆H₁₃Cl₂F₃N₂
M_r = 361.18
Monoclinic, P 2₁ /c
a = 11.2600 (16) Å
b = 11.4025 (17) Å
c = 14.8398 (16) Å
β = 123.773 (7)°
V = 1583.8 (4) Å³
Z = 4
Mo Kα radiation
μ = 0.44 mm⁻¹
T = 100 K
0.32 × 0.26 × 0.22 mm

Data collection

Bruker SMART APEXII Duo CCD diffractometer
Absorption correction: multi-scan (SADABS); Bruker, 2009 ) T_min = 0.872, T_max = 0.911
22269 measured reflections
5714 independent reflections
5043 reflections with I > 2σ(I)
R_int = 0.023

Refinement

R[F² > 2σ(F²)] = 0.029
wR(F²) = 0.090
S = 1.02
5714 reflections
210 parameters
H-atom parameters constrained
Δρ_max = 0.49 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1A⋯F1ⁱ	0.95	2.39	3.1652 (14)	139
C15—H15A⋯F2	0.98	2.38	3.1018 (13)	130
Symmetry code: (i) x-1, y, z-1.

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536812042419/hb6964sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812042419/hb6964Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536812042419/hb6964Isup3.cml

checkCIF report

Comment top

Hydrazones are important compounds for drug design, as possible ligands for metal complexes, organocatalysis and also for the syntheses of heterocyclic compounds (e.g. Barbazan et al., 2008; Banerjee et al., 2009; Ghavtadze et al., 2008). As part of our ongoing studies in this area (Fun et al., 2011a,b), we now describe the structure of the title compound, (I).

The title compound, as shown in Fig. 1, exists in trans conformation with respect to the C7═N1 bond [C7═N1 = 1.2952 (11) Å]. An S(6) ring is formed via an intramolecular C15—H15A···F2 hydrogen bond (Table 1). The dihedral angle between the benzene rings (C1–C6 & C8–C13) is 42.09 (4)°.

In the crystal, Fig. 2, the molecules are linked into chains along [101] by C1—H1A···F1 hydrogen bonds (Table 1).

Related literature top

For background to the properties and applications of hydrazones, see: Barbazan et al. (2008); Banerjee et al. (2009); Ghavtadze et al. (2008). For related structures, see: Fun et al. (2011a,b). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

Experimental top

Equimolar amount of [2,3-dichloro-6-methyl-5-(trifluoromethyl)phenyl]hydrazine and acetophenone were dissolved in a minimum amount of ethanol, then followed by the addition of 0.5 ml concentrated sulfuric acid. The solution was refluxed for 8 h then cooled to room temperature and poured into ice cold water. The solid product was collected through filtration and then dried using a drying oven at 80°C. The product was redissolved in ethanol for recrystalliziation to give yellow blocks of (I). Melting point: 368 K.

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids.
	Fig. 2. The crystal packing of the title compound, viewed along the a axis, showing the chains along [101]. H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity.

(2E)-1-[2,3-Dichloro-6-methyl-5-(trifluoromethyl)phenyl]-2- (1-phenylethylidene)hydrazine top

Crystal data top

C₁₆H₁₃Cl₂F₃N₂	F(000) = 736
M_r = 361.18	D_x = 1.515 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 9943 reflections
a = 11.2600 (16) Å	θ = 2.4–32.6°
b = 11.4025 (17) Å	µ = 0.44 mm⁻¹
c = 14.8398 (16) Å	T = 100 K
β = 123.773 (7)°	Block, yellow
V = 1583.8 (4) Å³	0.32 × 0.26 × 0.22 mm
Z = 4

Data collection top

Bruker SMART APEXII Duo CCD diffractometer	5714 independent reflections
Radiation source: fine-focus sealed tube	5043 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.023
ϕ and ω scans	θ_max = 32.6°, θ_min = 2.4°
Absorption correction: multi-scan (SADABS); Bruker, 2009)	h = −17→17
T_min = 0.872, T_max = 0.911	k = −17→16
22269 measured reflections	l = −22→22

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.090	H-atom parameters constrained
S = 1.02	w = 1/[σ²(F_o²) + (0.0515P)² + 0.4114P] where P = (F_o² + 2F_c²)/3
5714 reflections	(Δ/σ)_max = 0.001
210 parameters	Δρ_max = 0.49 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₁₆H₁₃Cl₂F₃N₂	V = 1583.8 (4) Å³
M_r = 361.18	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.2600 (16) Å	µ = 0.44 mm⁻¹
b = 11.4025 (17) Å	T = 100 K
c = 14.8398 (16) Å	0.32 × 0.26 × 0.22 mm
β = 123.773 (7)°

Data collection top

Bruker SMART APEXII Duo CCD diffractometer	5714 independent reflections
Absorption correction: multi-scan (SADABS); Bruker, 2009)	5043 reflections with I > 2σ(I)
T_min = 0.872, T_max = 0.911	R_int = 0.023
22269 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.029	0 restraints
wR(F²) = 0.090	H-atom parameters constrained
S = 1.02	Δρ_max = 0.49 e Å⁻³
5714 reflections	Δρ_min = −0.27 e Å⁻³
210 parameters

Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cl1	0.07133 (2)	0.57463 (2)	0.919947 (18)	0.02243 (6)
Cl2	0.27412 (3)	0.51560 (3)	1.16881 (2)	0.03137 (7)
F1	0.76376 (7)	0.64100 (7)	1.26985 (6)	0.04073 (19)
F2	0.72355 (7)	0.79611 (5)	1.17471 (5)	0.02773 (13)
F3	0.76971 (7)	0.63239 (6)	1.12760 (7)	0.03906 (18)
N1	0.24945 (8)	0.64196 (7)	0.75151 (6)	0.01758 (13)
N2	0.21577 (8)	0.68019 (7)	0.82355 (6)	0.01970 (14)
H1	0.1231	0.6830	0.7982	0.024*
C1	0.08557 (10)	0.60301 (8)	0.46427 (7)	0.02097 (16)
H1A	−0.0116	0.6165	0.4387	0.025*
C2	0.11987 (11)	0.56352 (9)	0.39242 (8)	0.02343 (17)
H2A	0.0464	0.5506	0.3184	0.028*
C3	0.26177 (11)	0.54303 (8)	0.42924 (8)	0.02305 (17)
H3A	0.2855	0.5160	0.3806	0.028*
C4	0.36909 (10)	0.56246 (8)	0.53808 (8)	0.02125 (16)
H4A	0.4660	0.5484	0.5634	0.026*
C5	0.33508 (9)	0.60236 (7)	0.60973 (7)	0.01782 (15)
H5A	0.4090	0.6157	0.6836	0.021*
C6	0.19245 (9)	0.62302 (7)	0.57366 (7)	0.01647 (14)
C7	0.15569 (9)	0.66423 (7)	0.65008 (7)	0.01714 (14)
C8	0.30910 (9)	0.65100 (7)	0.93301 (7)	0.01651 (14)
C9	0.45661 (9)	0.67664 (7)	0.98943 (7)	0.01764 (15)
C10	0.54176 (9)	0.65007 (7)	1.10045 (7)	0.01872 (15)
C11	0.48613 (10)	0.60149 (8)	1.15569 (7)	0.02078 (16)
H11A	0.5468	0.5845	1.2309	0.025*
C12	0.34106 (10)	0.57840 (8)	1.09936 (7)	0.01957 (15)
C13	0.25253 (9)	0.60334 (8)	0.98898 (7)	0.01731 (14)
C14	0.01767 (10)	0.72840 (9)	0.60945 (8)	0.02298 (17)
H14A	0.0361	0.7958	0.6565	0.034*
H14B	−0.0503	0.6753	0.6102	0.034*
H14C	−0.0225	0.7558	0.5353	0.034*
C15	0.51547 (11)	0.73642 (9)	0.93086 (8)	0.02373 (17)
H15A	0.6001	0.7824	0.9828	0.036*
H15B	0.4426	0.7885	0.8747	0.036*
H15C	0.5418	0.6770	0.8972	0.036*
C16	0.69874 (10)	0.67904 (8)	1.16736 (8)	0.02398 (18)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.01517 (9)	0.02920 (11)	0.02257 (11)	−0.00304 (7)	0.01028 (8)	−0.00384 (7)
Cl2	0.02648 (12)	0.04378 (15)	0.02537 (12)	−0.00394 (10)	0.01537 (10)	0.00792 (10)
F1	0.0198 (3)	0.0430 (4)	0.0341 (4)	−0.0034 (3)	−0.0007 (3)	0.0151 (3)
F2	0.0243 (3)	0.0190 (3)	0.0311 (3)	−0.0060 (2)	0.0099 (2)	−0.0040 (2)
F3	0.0199 (3)	0.0342 (3)	0.0623 (5)	−0.0027 (2)	0.0223 (3)	−0.0143 (3)
N1	0.0180 (3)	0.0189 (3)	0.0170 (3)	0.0008 (2)	0.0105 (3)	−0.0012 (2)
N2	0.0173 (3)	0.0259 (4)	0.0161 (3)	0.0032 (3)	0.0094 (3)	−0.0008 (3)
C1	0.0184 (4)	0.0250 (4)	0.0172 (4)	−0.0010 (3)	0.0084 (3)	−0.0001 (3)
C2	0.0270 (4)	0.0244 (4)	0.0171 (4)	−0.0028 (3)	0.0111 (3)	−0.0015 (3)
C3	0.0314 (5)	0.0200 (4)	0.0232 (4)	0.0004 (3)	0.0185 (4)	−0.0007 (3)
C4	0.0228 (4)	0.0206 (4)	0.0244 (4)	0.0031 (3)	0.0157 (4)	0.0015 (3)
C5	0.0176 (3)	0.0176 (3)	0.0181 (3)	0.0016 (3)	0.0099 (3)	0.0014 (3)
C6	0.0168 (3)	0.0161 (3)	0.0162 (3)	0.0004 (3)	0.0090 (3)	0.0011 (3)
C7	0.0163 (3)	0.0177 (3)	0.0179 (3)	0.0009 (3)	0.0098 (3)	0.0005 (3)
C8	0.0161 (3)	0.0164 (3)	0.0171 (3)	0.0004 (3)	0.0092 (3)	−0.0019 (3)
C9	0.0168 (3)	0.0158 (3)	0.0209 (4)	−0.0007 (3)	0.0109 (3)	−0.0021 (3)
C10	0.0144 (3)	0.0156 (3)	0.0222 (4)	0.0002 (3)	0.0077 (3)	−0.0005 (3)
C11	0.0181 (4)	0.0196 (4)	0.0195 (4)	0.0005 (3)	0.0072 (3)	0.0025 (3)
C12	0.0185 (4)	0.0203 (4)	0.0199 (4)	−0.0006 (3)	0.0106 (3)	0.0016 (3)
C13	0.0144 (3)	0.0185 (3)	0.0183 (4)	−0.0005 (3)	0.0086 (3)	−0.0019 (3)
C14	0.0196 (4)	0.0267 (4)	0.0234 (4)	0.0066 (3)	0.0125 (3)	0.0042 (3)
C15	0.0228 (4)	0.0257 (4)	0.0258 (4)	−0.0059 (3)	0.0155 (4)	−0.0041 (3)
C16	0.0165 (4)	0.0191 (4)	0.0288 (4)	−0.0009 (3)	0.0079 (3)	0.0006 (3)

Geometric parameters (Å, º) top

Cl1—C13	1.7309 (9)	C5—H5A	0.9500
Cl2—C12	1.7340 (10)	C6—C7	1.4833 (12)
F1—C16	1.3414 (12)	C7—C14	1.5075 (12)
F2—C16	1.3558 (11)	C8—C13	1.4069 (12)
F3—C16	1.3394 (13)	C8—C9	1.4139 (12)
N1—C7	1.2952 (11)	C9—C10	1.4032 (13)
N1—N2	1.3884 (10)	C9—C15	1.5165 (13)
N2—C8	1.3985 (11)	C10—C11	1.3936 (13)
N2—H1	0.8915	C10—C16	1.5060 (13)
C1—C2	1.3951 (13)	C11—C12	1.3850 (13)
C1—C6	1.4013 (12)	C11—H11A	0.9500
C1—H1A	0.9500	C12—C13	1.3936 (12)
C2—C3	1.3912 (15)	C14—H14A	0.9800
C2—H2A	0.9500	C14—H14B	0.9800
C3—C4	1.3958 (14)	C14—H14C	0.9800
C3—H3A	0.9500	C15—H15A	0.9800
C4—C5	1.3916 (12)	C15—H15B	0.9800
C4—H4A	0.9500	C15—H15C	0.9800
C5—C6	1.4020 (12)

C7—N1—N2	115.99 (7)	C11—C10—C9	122.64 (8)
N1—N2—C8	117.97 (7)	C11—C10—C16	116.48 (8)
N1—N2—H1	116.3	C9—C10—C16	120.81 (8)
C8—N2—H1	116.5	C12—C11—C10	119.05 (8)
C2—C1—C6	120.91 (8)	C12—C11—H11A	120.5
C2—C1—H1A	119.5	C10—C11—H11A	120.5
C6—C1—H1A	119.5	C11—C12—C13	120.24 (8)
C3—C2—C1	119.96 (9)	C11—C12—Cl2	118.45 (7)
C3—C2—H2A	120.0	C13—C12—Cl2	121.31 (7)
C1—C2—H2A	120.0	C12—C13—C8	120.66 (8)
C2—C3—C4	119.63 (9)	C12—C13—Cl1	119.65 (7)
C2—C3—H3A	120.2	C8—C13—Cl1	119.69 (7)
C4—C3—H3A	120.2	C7—C14—H14A	109.5
C5—C4—C3	120.47 (9)	C7—C14—H14B	109.5
C5—C4—H4A	119.8	H14A—C14—H14B	109.5
C3—C4—H4A	119.8	C7—C14—H14C	109.5
C4—C5—C6	120.44 (8)	H14A—C14—H14C	109.5
C4—C5—H5A	119.8	H14B—C14—H14C	109.5
C6—C5—H5A	119.8	C9—C15—H15A	109.5
C1—C6—C5	118.60 (8)	C9—C15—H15B	109.5
C1—C6—C7	120.82 (8)	H15A—C15—H15B	109.5
C5—C6—C7	120.57 (7)	C9—C15—H15C	109.5
N1—C7—C6	115.64 (7)	H15A—C15—H15C	109.5
N1—C7—C14	123.57 (8)	H15B—C15—H15C	109.5
C6—C7—C14	120.78 (7)	F3—C16—F1	106.72 (9)
N2—C8—C13	118.89 (8)	F3—C16—F2	106.25 (8)
N2—C8—C9	121.03 (8)	F1—C16—F2	105.61 (8)
C13—C8—C9	119.91 (8)	F3—C16—C10	113.04 (8)
C10—C9—C8	117.49 (8)	F1—C16—C10	112.18 (8)
C10—C9—C15	122.61 (8)	F2—C16—C10	112.51 (8)
C8—C9—C15	119.82 (8)

C7—N1—N2—C8	175.65 (8)	C15—C9—C10—C11	176.09 (8)
C6—C1—C2—C3	0.26 (14)	C8—C9—C10—C16	−177.55 (8)
C1—C2—C3—C4	−0.15 (14)	C15—C9—C10—C16	−0.72 (13)
C2—C3—C4—C5	−0.14 (14)	C9—C10—C11—C12	−0.09 (14)
C3—C4—C5—C6	0.32 (13)	C16—C10—C11—C12	176.85 (8)
C2—C1—C6—C5	−0.09 (13)	C10—C11—C12—C13	0.13 (14)
C2—C1—C6—C7	−179.58 (8)	C10—C11—C12—Cl2	178.90 (7)
C4—C5—C6—C1	−0.21 (13)	C11—C12—C13—C8	0.68 (13)
C4—C5—C6—C7	179.29 (8)	Cl2—C12—C13—C8	−178.05 (7)
N2—N1—C7—C6	−179.96 (7)	C11—C12—C13—Cl1	−179.68 (7)
N2—N1—C7—C14	0.51 (13)	Cl2—C12—C13—Cl1	1.59 (11)
C1—C6—C7—N1	157.04 (8)	N2—C8—C13—C12	−176.86 (8)
C5—C6—C7—N1	−22.44 (12)	C9—C8—C13—C12	−1.53 (13)
C1—C6—C7—C14	−23.41 (12)	N2—C8—C13—Cl1	3.50 (11)
C5—C6—C7—C14	157.11 (8)	C9—C8—C13—Cl1	178.83 (6)
N1—N2—C8—C13	−131.65 (8)	C11—C10—C16—F3	127.38 (9)
N1—N2—C8—C9	53.07 (11)	C9—C10—C16—F3	−55.61 (12)
N2—C8—C9—C10	176.75 (8)	C11—C10—C16—F1	6.65 (12)
C13—C8—C9—C10	1.52 (12)	C9—C10—C16—F1	−176.35 (8)
N2—C8—C9—C15	−0.17 (12)	C11—C10—C16—F2	−112.26 (10)
C13—C8—C9—C15	−175.40 (8)	C9—C10—C16—F2	64.74 (12)
C8—C9—C10—C11	−0.74 (13)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···F1ⁱ	0.95	2.39	3.1652 (14)	139
C15—H15A···F2	0.98	2.38	3.1018 (13)	130

Symmetry code: (i) x−1, y, z−1.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₃Cl₂F₃N₂
M_r	361.18
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	11.2600 (16), 11.4025 (17), 14.8398 (16)
β (°)	123.773 (7)
V (Å³)	1583.8 (4)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.44
Crystal size (mm)	0.32 × 0.26 × 0.22

Data collection
Diffractometer	Bruker SMART APEXII Duo CCD diffractometer
Absorption correction	Multi-scan (SADABS); Bruker, 2009)
T_min, T_max	0.872, 0.911
No. of measured, independent and observed [I > 2σ(I)] reflections	22269, 5714, 5043
R_int	0.023
(sin θ/λ)_max (Å⁻¹)	0.758

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.029, 0.090, 1.02
No. of reflections	5714
No. of parameters	210
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.49, −0.27

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008), PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···F1ⁱ	0.95	2.39	3.1652 (14)	139
C15—H15A···F2	0.98	2.38	3.1018 (13)	130

Symmetry code: (i) x−1, y, z−1.

Footnotes

‡Thomson Reuters ResearcherID: A-3561-2009.

§Thomson Reuters ResearcherID: C-7581-2009.

Acknowledgements

HKF and WSL thank Universiti Sains Malaysia (USM) for the Research University Grant (1001/PFIZIK/811160). WSL also thanks the Malaysian Government and USM for the position of Research Officer under the Research University Grant (1001/PFIZIK/811160).

References

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