1-(2-Methyl-6-nitro-4-phenyl-3-quinol­yl)ethanone

Loh, W.-S.; Fun, H.-K.; Kiran, K.; Sarveswari, S.; Vijayakumar, V.

doi:10.1107/S1600536810015473

organic compounds

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ISSN: 2056-9890

Volume 66| Part 5| May 2010| Page o1237

https://doi.org/10.1107/S1600536810015473

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1-(2-Methyl-6-nitro-4-phenyl-3-quinolyl)ethanone

Wan-Sin Loh,^a ‡ Hoong-Kun Fun,^a ^*§ K. Kiran,^b S. Sarveswari ^b and V. Vijayakumar ^b

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and ^bOrganic Chemistry Division, School of Advanced Sciences, VIT University, Vellore 632 014, India
^*Correspondence e-mail: hkfun@usm.my

(Received 6 April 2010; accepted 27 April 2010; online 30 April 2010)

In the title compound, C₁₈H₁₄N₂O₃, the quinoline ring system is almost planar [maximum deviation = 0.013 (2) Å] and forms a dihedral angle of 60.36 (7)° with the benzene ring. The nitro group is slightly twisted from the attached quinoline ring system, forming a dihedral angle of 9.06 (19)°. In the crystal packing, intermolecular C—H⋯O hydrogen bonds link the molecules into chains propagating in [010].

Related literature

For related structures, see: Fun et al. (2009 ); Loh et al. (2009 ). For bond-length data, see: Allen et al. (1987 ). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₁₈H₁₄N₂O₃
M_r = 306.31
Monoclinic, P 2₁ /c
a = 13.297 (2) Å
b = 7.7689 (12) Å
c = 17.9430 (19) Å
β = 129.099 (7)°
V = 1438.5 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 100 K
0.48 × 0.33 × 0.24 mm

Data collection

Bruker APEXII DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.954, T_max = 0.977
14926 measured reflections
4148 independent reflections
3310 reflections with I > 2σ(I)
R_int = 0.035

Refinement

R[F² > 2σ(F²)] = 0.061
wR(F²) = 0.232
S = 1.13
4148 reflections
211 parameters
H-atom parameters constrained
Δρ_max = 0.86 e Å⁻³
Δρ_min = −0.78 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3A⋯O2ⁱ	0.93	2.56	3.208 (3)	127
Symmetry code: (i) $[-x, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

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 and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810015473/hb5399sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810015473/hb5399Isup2.hkl

checkCIF report

Comment top

In continuation of our interest in the synthesis and structures of quinolines (Fun et al., 2009; Loh et al., 2009), we now report the title compound, (I).

In the title compound (Fig. 1), the quinoline ring system (C1/N1/C2–C9) is approximately planar with a maximum deviation of 0.013 (2) Å at atom C5. This mean plane of the quinoline ring forms a dihedral angle of 60.36 (7)° with the benzene ring (C10–C15). The nitro group (N2/O2/O3) is slightly twisted from the attached quinoline ring system, forming a dihedral angle of 9.06 (19)°. Bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable to closely related structures (Fun et al., 2009; Loh et al., 2009).

In the crystal packing (Fig. 2), intermolecular C3—H3A···O2 hydrogen bonds (Table 1) linked the molecules into chains linking down the b axis.

Related literature top

For related structures, see: Fun et al. (2009); Loh et al. (2009). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

Experimental top

A mixture of 5-nitro-2-amino-benzophenone (0.01 M) acetylacetone (0.01 M) and 0.15 ml of concentrated HCl was irradiated under microwave for about 8 min at 240 W. The resultant solid was filtered, dried and purified by column chromatography using 1:1 mixture of ethyl acetate and petroleum ether. M.P.: 403 K. Yield: 60%. Yellow blocks of (I) were recrystallised from chloroform.

Structure description top

In continuation of our interest in the synthesis and structures of quinolines (Fun et al., 2009; Loh et al., 2009), we now report the title compound, (I).

In the crystal packing (Fig. 2), intermolecular C3—H3A···O2 hydrogen bonds (Table 1) linked the molecules into chains linking down the b axis.

For related structures, see: Fun et al. (2009); Loh et al. (2009). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

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) and PLATON (Spek, 2009).

Figures top

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

1-(2-Methyl-6-nitro-4-phenyl-3-quinolyl)ethanone top

Crystal data top

C₁₈H₁₄N₂O₃	F(000) = 640
M_r = 306.31	D_x = 1.414 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5914 reflections
a = 13.297 (2) Å	θ = 3.0–32.9°
b = 7.7689 (12) Å	µ = 0.10 mm⁻¹
c = 17.9430 (19) Å	T = 100 K
β = 129.099 (7)°	Block, yellow
V = 1438.5 (3) Å³	0.48 × 0.33 × 0.24 mm
Z = 4

Data collection top

Bruker APEXII DUO CCD area-detector diffractometer	4148 independent reflections
Radiation source: fine-focus sealed tube	3310 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.035
φ and ω scans	θ_max = 30.0°, θ_min = 3.0°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −18→18
T_min = 0.954, T_max = 0.977	k = −10→10
14926 measured reflections	l = −25→24

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)] = 0.061	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.232	H-atom parameters constrained
S = 1.13	w = 1/[σ²(F_o²) + (0.1525P)² + 0.4637P] where P = (F_o² + 2F_c²)/3
4148 reflections	(Δ/σ)_max < 0.001
211 parameters	Δρ_max = 0.86 e Å⁻³
0 restraints	Δρ_min = −0.78 e Å⁻³

Crystal data top

C₁₈H₁₄N₂O₃	V = 1438.5 (3) Å³
M_r = 306.31	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 13.297 (2) Å	µ = 0.10 mm⁻¹
b = 7.7689 (12) Å	T = 100 K
c = 17.9430 (19) Å	0.48 × 0.33 × 0.24 mm
β = 129.099 (7)°

Data collection top

Bruker APEXII DUO CCD area-detector diffractometer	4148 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	3310 reflections with I > 2σ(I)
T_min = 0.954, T_max = 0.977	R_int = 0.035
14926 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.061	0 restraints
wR(F²) = 0.232	H-atom parameters constrained
S = 1.13	Δρ_max = 0.86 e Å⁻³
4148 reflections	Δρ_min = −0.78 e Å⁻³
211 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 esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
O1	0.22581 (15)	0.7458 (2)	0.39046 (10)	0.0262 (3)
O2	0.17169 (14)	1.20721 (18)	0.84191 (10)	0.0238 (3)
O3	0.35548 (14)	1.19938 (18)	0.86969 (10)	0.0229 (3)
N1	0.00896 (15)	0.73719 (17)	0.49922 (11)	0.0144 (3)
N2	0.24139 (16)	1.16058 (19)	0.82228 (11)	0.0169 (3)
C1	0.07078 (17)	0.6966 (2)	0.46604 (12)	0.0142 (3)
C2	0.07093 (16)	0.8420 (2)	0.57827 (12)	0.0133 (3)
C3	0.00244 (17)	0.8836 (2)	0.61256 (13)	0.0155 (3)
H3A	−0.0807	0.8404	0.5809	0.019*
C4	0.05691 (18)	0.9862 (2)	0.69126 (13)	0.0165 (3)
H4A	0.0124	1.0125	0.7140	0.020*
C5	0.18211 (17)	1.0511 (2)	0.73696 (12)	0.0149 (3)
C6	0.25169 (17)	1.0187 (2)	0.70594 (12)	0.0142 (3)
H6A	0.3334	1.0667	0.7374	0.017*
C7	0.19679 (16)	0.9106 (2)	0.62512 (12)	0.0132 (3)
C8	0.26215 (16)	0.8663 (2)	0.58772 (12)	0.0130 (3)
C9	0.19839 (17)	0.7586 (2)	0.50918 (12)	0.0141 (3)
C10	0.39210 (17)	0.9385 (2)	0.62955 (12)	0.0144 (3)
C11	0.50170 (17)	0.9063 (2)	0.72397 (13)	0.0165 (3)
H11A	0.4945	0.8404	0.7637	0.020*
C12	0.62200 (18)	0.9721 (2)	0.75941 (13)	0.0189 (4)
H12A	0.6946	0.9497	0.8225	0.023*
C13	0.63368 (18)	1.0716 (2)	0.70039 (14)	0.0190 (4)
H13A	0.7140	1.1152	0.7240	0.023*
C14	0.52518 (18)	1.1051 (2)	0.60658 (14)	0.0187 (4)
H14A	0.5328	1.1721	0.5674	0.022*
C15	0.40435 (18)	1.0389 (2)	0.57040 (13)	0.0173 (4)
H15A	0.3320	1.0612	0.5072	0.021*
C16	0.26170 (18)	0.6954 (2)	0.46785 (13)	0.0180 (4)
C17	0.3644 (2)	0.5611 (3)	0.52599 (15)	0.0257 (4)
H17A	0.4068	0.5403	0.4990	0.039*
H17B	0.3255	0.4564	0.5252	0.039*
H17C	0.4269	0.6005	0.5910	0.039*
C18	0.00164 (17)	0.5814 (2)	0.37966 (13)	0.0171 (3)
H18A	−0.0812	0.5498	0.3610	0.026*
H18B	0.0523	0.4796	0.3950	0.026*
H18C	−0.0104	0.6411	0.3277	0.026*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0330 (8)	0.0330 (8)	0.0241 (7)	−0.0058 (6)	0.0234 (7)	−0.0039 (6)
O2	0.0298 (8)	0.0284 (7)	0.0265 (7)	0.0043 (6)	0.0240 (7)	−0.0017 (5)
O3	0.0266 (7)	0.0256 (7)	0.0232 (7)	−0.0056 (5)	0.0189 (6)	−0.0054 (5)
N1	0.0177 (7)	0.0126 (6)	0.0182 (7)	0.0002 (5)	0.0139 (6)	0.0014 (5)
N2	0.0234 (8)	0.0166 (7)	0.0188 (7)	0.0026 (5)	0.0172 (6)	0.0017 (5)
C1	0.0183 (8)	0.0125 (7)	0.0168 (8)	−0.0002 (6)	0.0135 (7)	0.0006 (5)
C2	0.0163 (8)	0.0127 (7)	0.0165 (7)	0.0017 (5)	0.0131 (7)	0.0031 (5)
C3	0.0196 (8)	0.0139 (7)	0.0220 (8)	0.0009 (6)	0.0174 (7)	0.0025 (6)
C4	0.0237 (9)	0.0146 (7)	0.0227 (8)	0.0031 (6)	0.0202 (7)	0.0032 (6)
C5	0.0205 (8)	0.0138 (7)	0.0168 (8)	0.0019 (6)	0.0149 (7)	0.0014 (6)
C6	0.0176 (8)	0.0135 (7)	0.0182 (8)	0.0018 (6)	0.0144 (7)	0.0018 (6)
C7	0.0174 (8)	0.0126 (7)	0.0163 (8)	0.0019 (6)	0.0137 (7)	0.0023 (5)
C8	0.0144 (7)	0.0136 (7)	0.0160 (7)	0.0012 (5)	0.0120 (6)	0.0019 (5)
C9	0.0180 (8)	0.0140 (7)	0.0175 (8)	0.0004 (6)	0.0145 (7)	0.0006 (6)
C10	0.0177 (8)	0.0141 (7)	0.0191 (8)	−0.0014 (6)	0.0153 (7)	−0.0026 (6)
C11	0.0198 (8)	0.0175 (7)	0.0184 (8)	0.0002 (6)	0.0151 (7)	−0.0010 (6)
C12	0.0191 (8)	0.0208 (8)	0.0197 (8)	−0.0003 (6)	0.0136 (7)	−0.0020 (6)
C13	0.0191 (8)	0.0188 (8)	0.0280 (9)	−0.0033 (6)	0.0191 (8)	−0.0048 (6)
C14	0.0235 (9)	0.0173 (7)	0.0263 (9)	−0.0019 (6)	0.0209 (8)	−0.0011 (6)
C15	0.0212 (9)	0.0176 (7)	0.0198 (8)	0.0001 (6)	0.0161 (7)	0.0001 (6)
C16	0.0197 (8)	0.0207 (8)	0.0218 (9)	−0.0063 (6)	0.0170 (7)	−0.0076 (6)
C17	0.0224 (9)	0.0314 (10)	0.0269 (10)	0.0037 (7)	0.0173 (8)	−0.0067 (8)
C18	0.0199 (8)	0.0155 (7)	0.0200 (8)	−0.0020 (6)	0.0145 (7)	−0.0024 (6)

Geometric parameters (Å, º) top

O1—C16	1.214 (2)	C9—C16	1.512 (2)
O2—N2	1.2352 (19)	C10—C11	1.394 (3)
O3—N2	1.220 (2)	C10—C15	1.407 (2)
N1—C1	1.322 (2)	C11—C12	1.393 (2)
N1—C2	1.371 (2)	C11—H11A	0.9300
N2—C5	1.472 (2)	C12—C13	1.397 (3)
C1—C9	1.433 (2)	C12—H12A	0.9300
C1—C18	1.500 (2)	C13—C14	1.386 (3)
C2—C7	1.420 (2)	C13—H13A	0.9300
C2—C3	1.421 (2)	C14—C15	1.397 (2)
C3—C4	1.365 (2)	C14—H14A	0.9300
C3—H3A	0.9300	C15—H15A	0.9300
C4—C5	1.406 (2)	C16—C17	1.499 (3)
C4—H4A	0.9300	C17—H17A	0.9600
C5—C6	1.371 (2)	C17—H17B	0.9600
C6—C7	1.416 (2)	C17—H17C	0.9600
C6—H6A	0.9300	C18—H18A	0.9600
C7—C8	1.435 (2)	C18—H18B	0.9600
C8—C9	1.378 (2)	C18—H18C	0.9600
C8—C10	1.493 (2)

C1—N1—C2	117.97 (14)	C11—C10—C8	122.36 (15)
O3—N2—O2	123.74 (15)	C15—C10—C8	118.50 (15)
O3—N2—C5	118.87 (13)	C12—C11—C10	120.56 (16)
O2—N2—C5	117.39 (15)	C12—C11—H11A	119.7
N1—C1—C9	122.51 (15)	C10—C11—H11A	119.7
N1—C1—C18	117.24 (15)	C11—C12—C13	120.11 (17)
C9—C1—C18	120.25 (14)	C11—C12—H12A	119.9
N1—C2—C7	123.38 (14)	C13—C12—H12A	119.9
N1—C2—C3	116.87 (15)	C14—C13—C12	119.78 (17)
C7—C2—C3	119.74 (15)	C14—C13—H13A	120.1
C4—C3—C2	120.92 (16)	C12—C13—H13A	120.1
C4—C3—H3A	119.5	C13—C14—C15	120.43 (16)
C2—C3—H3A	119.5	C13—C14—H14A	119.8
C3—C4—C5	118.26 (14)	C15—C14—H14A	119.8
C3—C4—H4A	120.9	C14—C15—C10	120.00 (17)
C5—C4—H4A	120.9	C14—C15—H15A	120.0
C6—C5—C4	123.46 (16)	C10—C15—H15A	120.0
C6—C5—N2	118.22 (15)	O1—C16—C17	123.29 (16)
C4—C5—N2	118.32 (14)	O1—C16—C9	121.18 (17)
C5—C6—C7	118.74 (16)	C17—C16—C9	115.44 (15)
C5—C6—H6A	120.6	C16—C17—H17A	109.5
C7—C6—H6A	120.6	C16—C17—H17B	109.5
C6—C7—C2	118.85 (14)	H17A—C17—H17B	109.5
C6—C7—C8	123.23 (15)	C16—C17—H17C	109.5
C2—C7—C8	117.91 (15)	H17A—C17—H17C	109.5
C9—C8—C7	117.43 (15)	H17B—C17—H17C	109.5
C9—C8—C10	120.86 (14)	C1—C18—H18A	109.5
C7—C8—C10	121.67 (14)	C1—C18—H18B	109.5
C8—C9—C1	120.78 (14)	H18A—C18—H18B	109.5
C8—C9—C16	121.66 (15)	C1—C18—H18C	109.5
C1—C9—C16	117.51 (14)	H18A—C18—H18C	109.5
C11—C10—C15	119.12 (16)	H18B—C18—H18C	109.5

C2—N1—C1—C9	−0.4 (2)	C7—C8—C9—C1	1.1 (2)
C2—N1—C1—C18	179.85 (14)	C10—C8—C9—C1	−176.71 (15)
C1—N1—C2—C7	0.9 (2)	C7—C8—C9—C16	−176.30 (15)
C1—N1—C2—C3	−179.96 (14)	C10—C8—C9—C16	5.9 (2)
N1—C2—C3—C4	179.55 (15)	N1—C1—C9—C8	−0.7 (3)
C7—C2—C3—C4	−1.3 (2)	C18—C1—C9—C8	179.11 (15)
C2—C3—C4—C5	0.6 (2)	N1—C1—C9—C16	176.82 (15)
C3—C4—C5—C6	0.9 (3)	C18—C1—C9—C16	−3.4 (2)
C3—C4—C5—N2	−179.50 (15)	C9—C8—C10—C11	−119.51 (18)
O3—N2—C5—C6	−9.7 (2)	C7—C8—C10—C11	62.8 (2)
O2—N2—C5—C6	170.71 (15)	C9—C8—C10—C15	58.8 (2)
O3—N2—C5—C4	170.68 (15)	C7—C8—C10—C15	−118.90 (17)
O2—N2—C5—C4	−8.9 (2)	C15—C10—C11—C12	−0.2 (2)
C4—C5—C6—C7	−1.7 (3)	C8—C10—C11—C12	178.13 (15)
N2—C5—C6—C7	178.71 (14)	C10—C11—C12—C13	0.1 (3)
C5—C6—C7—C2	0.9 (2)	C11—C12—C13—C14	0.2 (3)
C5—C6—C7—C8	−179.01 (15)	C12—C13—C14—C15	−0.5 (3)
N1—C2—C7—C6	179.57 (15)	C13—C14—C15—C10	0.5 (3)
C3—C2—C7—C6	0.5 (2)	C11—C10—C15—C14	−0.1 (2)
N1—C2—C7—C8	−0.5 (2)	C8—C10—C15—C14	−178.50 (15)
C3—C2—C7—C8	−179.57 (14)	C8—C9—C16—O1	−109.8 (2)
C6—C7—C8—C9	179.40 (15)	C1—C9—C16—O1	72.7 (2)
C2—C7—C8—C9	−0.6 (2)	C8—C9—C16—C17	73.6 (2)
C6—C7—C8—C10	−2.8 (2)	C1—C9—C16—C17	−103.90 (19)
C2—C7—C8—C10	177.24 (14)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3A···O2ⁱ	0.93	2.56	3.208 (3)	127

Symmetry code: (i) −x, y−1/2, −z+3/2.

Experimental details

Crystal data
Chemical formula	C₁₈H₁₄N₂O₃
M_r	306.31
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	13.297 (2), 7.7689 (12), 17.9430 (19)
β (°)	129.099 (7)
V (Å³)	1438.5 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.48 × 0.33 × 0.24

Data collection
Diffractometer	Bruker APEXII DUO CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.954, 0.977
No. of measured, independent and observed [I > 2σ(I)] reflections	14926, 4148, 3310
R_int	0.035
(sin θ/λ)_max (Å⁻¹)	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.061, 0.232, 1.13
No. of reflections	4148
No. of parameters	211
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.86, −0.78

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3A···O2ⁱ	0.93	2.56	3.208 (3)	127

Symmetry code: (i) −x, y−1/2, −z+3/2.

Footnotes

‡Thomson Reuters ResearcherID: C-7581-2009.

§Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

HKF and WSL thank Universiti Sains Malaysia (USM) for the Research University Golden Goose Grant (1001/PFIZIK/811012). WSL thanks the Malaysian Government and USM for the award of a Research Fellowship. VV is grateful to DST-India for funding through the Young Scientist Scheme (Fast Track Proposal).

References

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