5,6-Dichloro-2-(3-methoxy­phen­yl)isoindoline-1,3-dione

Büyükgüngör, O.; Odabaşoğlu, M.

doi:10.1107/S1600536808010659

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 64| Part 5| May 2008| Page o881

doi:10.1107/S1600536808010659

Open

access

5,6-Dichloro-2-(3-methoxyphenyl)isoindoline-1,3-dione

Orhan Büyükgüngör ^a ^* and Mustafa Odabaşoğlu ^b

^aDepartment of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, TR-55139 Kurupelit Samsun, Turkey, and ^bDepartment of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayıs University, TR-55139 Kurupelit Samsun, Turkey
^*Correspondence e-mail: orhanb@omu.edu.tr

(Received 4 April 2008; accepted 17 April 2008; online 23 April 2008)

The title compound, C₁₅H₉Cl₂NO₃, crystallizes as an inversion twin, the ratio of the twin components being 0.43 (13):0.57 (13). The isoindoline group is planar and inclined by 77.63 (3)° to the aromatic ring substituent. The crystal structure is stabilized by aromatic π–π stacking interactions involving the benzene rings of adjacent isoindoline groups, with a centroid–centroid distance of 3.664 (7) Å and an interplanar separation of 3.409 Å.

Related literature

For general background, see: Chapman et al. (1979 ); Hall et al., (1983 ; 1987 ); Srivastava et al. (2001 ); Abdel-Hafez (2004 ); Sena et al. (2007 ).

Experimental

Crystal data

C₁₅H₉Cl₂NO₃
M_r = 322.13
Orthorhombic, P 2₁ 2₁ 2₁
a = 6.8689 (5) Å
b = 9.7362 (10) Å
c = 20.4271 (14) Å
V = 1366.1 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.48 mm⁻¹
T = 296 K
0.65 × 0.51 × 0.23 mm

Data collection

Stoe IPDSII diffractometer
Absorption correction: integration (X-RED32; Stoe & Cie, 2002 ) T_min = 0.685, T_max = 0.888
6123 measured reflections
2687 independent reflections
2076 reflections with I > 2σ(I)
R_int = 0.117

Refinement

R[F² > 2σ(F²)] = 0.071
wR(F²) = 0.169
S = 1.00
2687 reflections
192 parameters
H-atom parameters constrained
Δρ_max = 0.63 e Å⁻³
Δρ_min = −0.57 e Å⁻³
Absolute structure: Flack (1983 ), 1114 Friedel pairs
Flack parameter: 0.43 (13)

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808010659/rz2205sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808010659/rz2205Isup2.hkl

checkCIF report

Comment top

The present work is part of a structural study of derivatives of N-arylphthalimides (Abdel-Hafez, 2004; Chapman et al., 1979; Hall et al., 1983; Hall et al., 1987; Sena et al., 2007; Srivastava et al., 2001). We report here the crystal structure of 5,6-dichloro-2-(3-methoxyphenyl)isoindoline-1,3-dione.

The molecule of the title compound consist of a 5,6-dichlorophthalimide unit connected to a m-methoxyphenyl group through the nitrogen atom (Fig. 1). The isoindoline ring (atoms N1/C1–C8) is almost planar, the largest deviation from the mean plane being 0.051 (3) Å for atom C5. The dihedral angle between the methoxyphenyl ring and the mean plane of the isoindoline group is 77.63 (3)°. The crystal packing is stabilized by aromatic π···π stacking interactions (Fig. 2) occurring between the aromatic rings of isoindoline groups at (x, y, z) and (-1/2+x; 3/2 - y; 1-z), with a centroid-centroid distance of 3.664 (7) Å and a plane-plane separations of 3.409 Å.

Related literature top

For general background, see: Chapman et al. (1979); Hall et al., (1983; 1987); Srivastava et al. (2001); Abdel-Hafez (2004); Sena et al. (2007).

Experimental top

A mixture of 4,5-dichlorophthalic acid (1.175 g, 0.005 mol) and 2-aminophenol (0.545 g, 0.02 mol) in DMF (1.5 ml) was heated at boiling temperature for 15 min, then ethanol (95%, 50 ml) was added. Crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation of this mixture at room temperature (yield 80%; mp. 546–548 K).

Computing details top

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA (Stoe & Cie, 2002); data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. A partial packing diagram of the title compound, showing the formation of π···π stacking interactions. H atoms are omitted for clarity. Cg1 and Cg1ⁱ are the centroids of the benzene rings of the isoindoline groups. [Symmetry code: (i) -1/2+x, 3/2-y, 1-z].

5,6-Dichloro-2-(3-methoxyphenyl)isoindoline-1,3-dione top

Crystal data top

C₁₅H₉Cl₂NO₃	F(000) = 656
M_r = 322.13	D_x = 1.566 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 6123 reflections
a = 6.8689 (5) Å	θ = 2.0–27.3°
b = 9.7362 (10) Å	µ = 0.48 mm⁻¹
c = 20.4271 (14) Å	T = 296 K
V = 1366.1 (2) Å³	Prism, colourless
Z = 4	0.65 × 0.51 × 0.23 mm

Data collection top

Stoe IPDSII diffractometer	2687 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	2076 reflections with I > 2σ(I)
Plane graphite monochromator	R_int = 0.117
Detector resolution: 6.67 pixels mm^-1	θ_max = 26.0°, θ_min = 2.0°
ω scan rotation method	h = −8→8
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	k = −12→10
T_min = 0.685, T_max = 0.888	l = −23→25
6123 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.071	w = 1/[σ²(F_o²) + (0.1011P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.169	(Δ/σ)_max = 0.001
S = 1.01	Δρ_max = 0.63 e Å⁻³
2687 reflections	Δρ_min = −0.57 e Å⁻³
192 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.054 (7)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 1114 Friedel pairs
Secondary atom site location: difference Fourier map	Absolute structure parameter: 0.43 (13)

Crystal data top

C₁₅H₉Cl₂NO₃	V = 1366.1 (2) Å³
M_r = 322.13	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 6.8689 (5) Å	µ = 0.48 mm⁻¹
b = 9.7362 (10) Å	T = 296 K
c = 20.4271 (14) Å	0.65 × 0.51 × 0.23 mm

Data collection top

Stoe IPDSII diffractometer	2687 independent reflections
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	2076 reflections with I > 2σ(I)
T_min = 0.685, T_max = 0.888	R_int = 0.117
6123 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.071	H-atom parameters constrained
wR(F²) = 0.169	Δρ_max = 0.63 e Å⁻³
S = 1.01	Δρ_min = −0.57 e Å⁻³
2687 reflections	Absolute structure: Flack (1983), 1114 Friedel pairs
192 parameters	Absolute structure parameter: 0.43 (13)
0 restraints

Special details top

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
C1	0.2767 (6)	0.3976 (4)	0.4834 (2)	0.0408 (9)
C2	0.2607 (6)	0.5458 (4)	0.5011 (2)	0.0380 (8)
C3	0.2552 (7)	0.6055 (4)	0.5626 (2)	0.0474 (9)
H3	0.2551	0.5526	0.6005	0.057*
C4	0.2499 (6)	0.7459 (4)	0.5652 (2)	0.0458 (9)
C5	0.2520 (6)	0.8278 (4)	0.5080 (2)	0.0444 (9)
C6	0.2545 (7)	0.7642 (4)	0.4471 (2)	0.0463 (9)
H6	0.2538	0.8157	0.4088	0.056*
C7	0.2579 (6)	0.6225 (4)	0.44509 (19)	0.0395 (8)
C8	0.2677 (6)	0.5285 (4)	0.3883 (2)	0.0438 (9)
C9	0.3137 (6)	0.2765 (5)	0.3758 (2)	0.0436 (10)
C10	0.4978 (6)	0.2535 (6)	0.3505 (3)	0.0598 (13)
H10	0.5993	0.3135	0.3599	0.072*
C11	0.5282 (7)	0.1425 (6)	0.3118 (3)	0.0624 (14)
H11	0.6517	0.1277	0.2946	0.075*
C12	0.3806 (7)	0.0500 (5)	0.2972 (2)	0.0527 (12)
H12	0.4041	−0.0263	0.2710	0.063*
C13	0.1967 (7)	0.0752 (5)	0.3229 (2)	0.0477 (11)
C14	0.1630 (6)	0.1861 (4)	0.3621 (2)	0.0466 (10)
H14	0.0397	0.2011	0.3795	0.056*
C15	0.0552 (10)	−0.1131 (6)	0.2632 (3)	0.0743 (16)
H15A	−0.0652	−0.1629	0.2605	0.112*
H15B	0.1584	−0.1749	0.2749	0.112*
H15C	0.0834	−0.0720	0.2216	0.112*
N1	0.2788 (5)	0.3963 (4)	0.41436 (16)	0.0412 (8)
O1	0.2907 (5)	0.2994 (3)	0.51795 (15)	0.0550 (8)
O2	0.2669 (6)	0.5562 (3)	0.33082 (15)	0.0616 (9)
O3	0.0389 (5)	−0.0085 (4)	0.3116 (2)	0.0749 (11)
Cl1	0.2389 (2)	0.82582 (13)	0.64049 (6)	0.0730 (4)
Cl2	0.25735 (16)	1.00342 (11)	0.51245 (6)	0.0578 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.047 (2)	0.0320 (19)	0.044 (2)	−0.0019 (18)	0.0005 (19)	0.0014 (16)
C2	0.0407 (16)	0.0300 (17)	0.043 (2)	−0.0036 (16)	−0.0006 (19)	−0.0017 (14)
C3	0.058 (2)	0.041 (2)	0.043 (2)	0.004 (2)	−0.004 (2)	−0.0045 (17)
C4	0.0455 (19)	0.044 (2)	0.047 (2)	0.003 (2)	−0.006 (2)	−0.0117 (17)
C5	0.0383 (15)	0.0338 (19)	0.061 (2)	0.0010 (17)	−0.006 (2)	−0.0052 (18)
C6	0.0487 (19)	0.037 (2)	0.053 (2)	0.006 (2)	0.001 (2)	0.0073 (17)
C7	0.0399 (17)	0.0360 (19)	0.043 (2)	−0.0027 (18)	0.001 (2)	0.0000 (15)
C8	0.049 (2)	0.041 (2)	0.042 (2)	0.004 (2)	0.0003 (18)	0.0012 (16)
C9	0.054 (2)	0.043 (2)	0.034 (2)	0.0034 (19)	0.0016 (15)	0.0006 (18)
C10	0.050 (2)	0.072 (3)	0.058 (3)	−0.006 (2)	0.007 (2)	−0.016 (3)
C11	0.057 (3)	0.069 (4)	0.061 (3)	0.007 (3)	0.010 (2)	−0.010 (3)
C12	0.075 (3)	0.043 (3)	0.040 (3)	0.012 (2)	0.002 (2)	−0.011 (2)
C13	0.066 (3)	0.035 (2)	0.042 (2)	−0.0022 (19)	−0.0012 (18)	−0.0046 (18)
C14	0.054 (2)	0.040 (2)	0.046 (2)	0.0013 (19)	0.0058 (18)	−0.001 (2)
C15	0.108 (4)	0.059 (3)	0.055 (3)	−0.021 (3)	−0.001 (3)	−0.013 (3)
N1	0.0523 (19)	0.0362 (17)	0.0351 (18)	−0.0028 (15)	0.0025 (15)	−0.0036 (13)
O1	0.087 (2)	0.0336 (15)	0.0445 (17)	0.0030 (16)	−0.0010 (15)	0.0009 (12)
O2	0.090 (2)	0.0525 (18)	0.0425 (18)	0.004 (2)	0.0015 (18)	0.0047 (14)
O3	0.081 (2)	0.067 (2)	0.076 (3)	−0.026 (2)	0.0145 (19)	−0.027 (2)
Cl1	0.1007 (9)	0.0574 (7)	0.0609 (8)	0.0176 (8)	−0.0121 (8)	−0.0238 (6)
Cl2	0.0536 (5)	0.0314 (5)	0.0883 (8)	0.0032 (5)	−0.0054 (6)	−0.0070 (5)

Geometric parameters (Å, º) top

C1—O1	1.192 (5)	C9—C10	1.384 (6)
C1—N1	1.410 (5)	C9—C14	1.387 (6)
C1—C2	1.491 (5)	C9—N1	1.428 (5)
C2—C7	1.367 (5)	C10—C11	1.355 (7)
C2—C3	1.384 (6)	C10—H10	0.9300
C3—C4	1.368 (6)	C11—C12	1.388 (7)
C3—H3	0.9300	C11—H11	0.9300
C4—C5	1.415 (6)	C12—C13	1.390 (6)
C4—Cl1	1.725 (4)	C12—H12	0.9300
C5—C6	1.389 (6)	C13—C14	1.364 (6)
C5—Cl2	1.713 (4)	C13—O3	1.376 (5)
C6—C7	1.381 (6)	C14—H14	0.9300
C6—H6	0.9300	C15—O3	1.424 (6)
C7—C8	1.479 (6)	C15—H15A	0.9600
C8—O2	1.205 (5)	C15—H15B	0.9600
C8—N1	1.395 (5)	C15—H15C	0.9600

O1—C1—N1	125.7 (4)	C14—C9—N1	120.2 (3)
O1—C1—C2	129.6 (4)	C11—C10—C9	119.2 (4)
N1—C1—C2	104.6 (3)	C11—C10—H10	120.4
C7—C2—C3	122.0 (4)	C9—C10—H10	120.4
C7—C2—C1	109.0 (3)	C10—C11—C12	122.0 (4)
C3—C2—C1	129.0 (4)	C10—C11—H11	119.0
C4—C3—C2	117.1 (4)	C12—C11—H11	119.0
C4—C3—H3	121.5	C11—C12—C13	117.9 (4)
C2—C3—H3	121.5	C11—C12—H12	121.1
C3—C4—C5	122.0 (4)	C13—C12—H12	121.1
C3—C4—Cl1	119.1 (3)	C14—C13—O3	115.7 (4)
C5—C4—Cl1	118.9 (3)	C14—C13—C12	121.1 (4)
C6—C5—C4	119.2 (4)	O3—C13—C12	123.2 (4)
C6—C5—Cl2	119.5 (3)	C13—C14—C9	119.6 (4)
C4—C5—Cl2	121.2 (3)	C13—C14—H14	120.2
C7—C6—C5	118.2 (4)	C9—C14—H14	120.2
C7—C6—H6	120.9	O3—C15—H15A	109.5
C5—C6—H6	120.9	O3—C15—H15B	109.5
C2—C7—C6	121.4 (4)	H15A—C15—H15B	109.5
C2—C7—C8	108.6 (3)	O3—C15—H15C	109.5
C6—C7—C8	130.0 (4)	H15A—C15—H15C	109.5
O2—C8—N1	125.4 (4)	H15B—C15—H15C	109.5
O2—C8—C7	128.7 (4)	C8—N1—C1	111.9 (3)
N1—C8—C7	105.9 (3)	C8—N1—C9	123.5 (3)
C10—C9—C14	120.3 (4)	C1—N1—C9	124.1 (3)
C10—C9—N1	119.5 (4)	C13—O3—C15	118.6 (4)

O1—C1—C2—C7	176.9 (5)	C14—C9—C10—C11	0.5 (8)
N1—C1—C2—C7	−1.1 (5)	N1—C9—C10—C11	−177.4 (4)
O1—C1—C2—C3	−1.1 (8)	C9—C10—C11—C12	−0.6 (9)
N1—C1—C2—C3	−179.1 (4)	C10—C11—C12—C13	0.8 (8)
C7—C2—C3—C4	−1.0 (7)	C11—C12—C13—C14	−0.9 (7)
C1—C2—C3—C4	176.7 (4)	C11—C12—C13—O3	179.7 (5)
C2—C3—C4—C5	−0.6 (8)	O3—C13—C14—C9	−179.7 (4)
C2—C3—C4—Cl1	178.9 (3)	C12—C13—C14—C9	0.9 (7)
C3—C4—C5—C6	1.7 (7)	C10—C9—C14—C13	−0.7 (7)
Cl1—C4—C5—C6	−177.9 (4)	N1—C9—C14—C13	177.2 (4)
C3—C4—C5—Cl2	−176.8 (4)	O2—C8—N1—C1	180.0 (5)
Cl1—C4—C5—Cl2	3.6 (5)	C7—C8—N1—C1	0.1 (5)
C4—C5—C6—C7	−1.0 (7)	O2—C8—N1—C9	7.6 (7)
Cl2—C5—C6—C7	177.4 (3)	C7—C8—N1—C9	−172.3 (4)
C3—C2—C7—C6	1.7 (7)	O1—C1—N1—C8	−177.5 (4)
C1—C2—C7—C6	−176.5 (4)	C2—C1—N1—C8	0.6 (5)
C3—C2—C7—C8	179.3 (4)	O1—C1—N1—C9	−5.2 (7)
C1—C2—C7—C8	1.2 (5)	C2—C1—N1—C9	172.9 (3)
C5—C6—C7—C2	−0.6 (7)	C10—C9—N1—C8	72.8 (6)
C5—C6—C7—C8	−177.7 (4)	C14—C9—N1—C8	−105.2 (5)
C2—C7—C8—O2	179.3 (5)	C10—C9—N1—C1	−98.6 (5)
C6—C7—C8—O2	−3.3 (9)	C14—C9—N1—C1	83.4 (5)
C2—C7—C8—N1	−0.8 (5)	C14—C13—O3—C15	170.2 (5)
C6—C7—C8—N1	176.6 (5)	C12—C13—O3—C15	−10.5 (8)

Experimental details

Crystal data
Chemical formula	C₁₅H₉Cl₂NO₃
M_r	322.13
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	296
a, b, c (Å)	6.8689 (5), 9.7362 (10), 20.4271 (14)
V (Å³)	1366.1 (2)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.48
Crystal size (mm)	0.65 × 0.51 × 0.23

Data collection
Diffractometer	Stoe IPDSII diffractometer
Absorption correction	Integration (X-RED32; Stoe & Cie, 2002)
T_min, T_max	0.685, 0.888
No. of measured, independent and observed [I > 2σ(I)] reflections	6123, 2687, 2076
R_int	0.117
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.071, 0.169, 1.01
No. of reflections	2687
No. of parameters	192
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.63, −0.57
Absolute structure	Flack (1983), 1114 Friedel pairs
Absolute structure parameter	0.43 (13)

Computer programs: X-AREA (Stoe & Cie, 2002), X-RED32 (Stoe & Cie, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Acknowledgements

The authors acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDSII diffractometer (purchased under grant F.279 of the University Research Fund).

References

Abdel-Hafez, A. A. M. (2004). Arch. Pharm. Res. 27, 495–501. Web of Science PubMed CAS Google Scholar
Chapman, J. M., Cocolas, G. H. & Hall, I. H. (1979). J. Med. Chem. 22, 1399–1402. CrossRef CAS PubMed Web of Science Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Flack, H. D. (1983). Acta Cryst. A39, 876–881. CrossRef CAS Web of Science IUCr Journals Google Scholar
Hall, I. H., Reynolds, D. J., Wong, O. T., Oswald, C. B. & Murthy, A. R. K. (1987). Pharm. Res. 4, 472–479. CrossRef CAS PubMed Web of Science Google Scholar
Hall, I. H., Voorstad, P. J., Chapman, J. M. & Cocolas, G. H. (1983). J. Pharm. Sci. 72, 845–851. CrossRef CAS PubMed Web of Science Google Scholar
Sena, V. L. M., Srivastava, M. R., de Simone, C. A., da Cruz Gonçalves, S. M., Silva, R. O. & Pereira, M. A. (2007). J. Braz. Chem. Soc. 18, 1224–1234. Web of Science CSD CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Srivastava, R. M., Oliveira, F. J. S., da Silva, L. P., de Freitas Filho, J. R., Oliveira, S. P. & Lima, V. L. M. (2001). Carbohydr. Res. 332, 335–340. Web of Science CrossRef PubMed CAS Google Scholar
Stoe & Cie (2002). X-AREA and X-RED32. Stoe & Cie, Darmstadt, Germany. Google Scholar