2-(4-Bromo­phen­yl)-5-fluoro-3-phenyl­sulfinyl-1-benzofuran

Choi, H.D.; Seo, P.J.; Son, B.W.; Lee, U.

doi:10.1107/S1600536810029958

2-(4-Bromophenyl)-5-fluoro-3-phenylsulfinyl-1-benzofuran

H. D. Choi, P. J. Seo, B. W. Son and U. Lee

In the title compound, C₂₀H₁₂BrFO₂S, the O atom and the phenyl group of the phenylsulfinyl substituent lie on opposite sides of the plane through the benzofuran fragment; the phenyl ring is nearly perpendicular to this plane [dihedral angle = 86.98 (6)°]. The 4-bromophenyl ring is rotated slightly out of the benzofuran plane, making a dihedral angle of 1.56 (8)°. The crystal structure features aromatic π–π interactions between the furan and phenyl rings of neighbouring molecules [centroid–centroid distance = 3.506 (3) Å], and an intermolecular C—H

π interaction. The crystal structure also exhibits a short intermolecular S

S contact [3.2635 (8) Å].

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536810029958/pk2256sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536810029958/pk2256Isup2.hkl Contains datablock I

CCDC reference: 788518

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Key indicators

Single-crystal X-ray study
T = 173 K
Mean (C-C) = 0.003 Å
R factor = 0.030
wR factor = 0.104
Data-to-parameter ratio = 17.0

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No syntax errors found



Alert level C
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600          8

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

Comment top

Many compounds containing a benzofuran moiety have attracted considerable interest in view of their pharmacological properties such as antifungal, antitumor and antiviral, antimicrobial activities (Aslam et al., 2006, Galal et al., 2009, Khan et al., 2005). These compounds occur widely in nature (Akgul & Anil, 2003; Soekamto et al., 2003). As a part of our continuing studies of the substituent effect on the solid state structures of 5-halo-2-phenyl-3-phenylsulfinyl-1-benzofuran analogues (Choi et al., 2009a,b,c), we report the crystal structure of the title compound (Fig. 1).

The benzofuran unit is essentially planar, with a mean deviation of 0.063 (1) Å from the least-squares plane defined by the nine constituent atoms. The dihedral angle formed by the benzofuran plane and the phenyl ring is 86.98 (6)°, and the 4-bromophenyl ring with 1.56 (8)° lies toward the benzofuran plane. The crystal packing (Fig. 2) is stabilized by aromatic π–π interactions between the furan and benzene rings of the adjacent molecules, with a Cg1···Cg2ⁱⁱ distance of 3.506 (3) Å (Cg1 and Cg2 are the centroids of the C1/C2/C7/O1/C8 furan ring and the C2–C7 benzene ring, respectively). The molecular packing (Fig. 2) is further stabilized by an intermolecular C—H···π interaction between the benzene H atom and the phenyl ring of a neighbouring molecule, with a C5—H5···Cg3ⁱ (Table 1; Cg3 is the centroid of the C15–C20 phenyl ring). The crystal structure also exhibits a short intermolecular S···S contact (Munshi & Guru Row, 2004), with a S···S^iv distance of 3.2635 (8) Å

Related literature top

For the pharmacological activity of benzofuran compounds, see: Aslam et al. (2006); Galal et al. (2009); Khan et al. (2005). For natural products with benzofuran rings, see: Akgul & Anil (2003); Soekamto et al. (2003). For the structures of related 5-halo-2-phenyl-3-phenylsulfinyl-1-benzofuran derivatives, see: Choi et al. (2009a,b,c). For short S···S interactions, see: Munshi & Guru Row (2004).

Experimental top

77% 3-chloroperoxybenzoic acid (247 mg, 1.1 mmol) was added in small portions to a stirred solution of 2-(4-bromophenyl)-5-fluoro-3-phenylsulfanyl-1-benzofuran (439 mg, 0.8 mmol) in dichloromethane (40 mL) at 273 K. After being stirred at room temperature for 6h, the mixture was washed with saturated sodium bicarbonate solution and the organic layer was separated, dried over magnesium sulfate, filtered and concentrated at reduced pressure. The residue was purified by column chromatography (hexane-ethyl acetate, 4:1 v/v) to afford the title compound as a colorless solid [yield 68%, m.p. 465–466 K; R_f = 0.75 (hexane–ethyl acetate, 4:1 v/v)]. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in benzene at room temperature.

Structure description top

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as a small spheres of arbitrary radius.
	Fig. 2. π–π, C—H···π and S···S interactions (dotted lines) in the crystal structure of the title compound. Cg denotes the ring centroids. [Symmetry codes: (i) x, y + 1, z; (ii) - x + 1, - y + 1, - z + 1; (iii) x, y - 1, z; (iv) - x + 1, - y, - z + 1.]

2-(4-Bromophenyl)-5-fluoro-3-phenylsulfinyl-1-benzofuran top

Crystal data top

C₂₀H₁₂BrFO₂S	Z = 2
M_r = 415.27	F(000) = 416
Triclinic, P1	D_x = 1.662 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.1361 (4) Å	Cell parameters from 8238 reflections
b = 9.8237 (5) Å	θ = 2.7–27.5°
c = 11.4093 (5) Å	µ = 2.62 mm⁻¹
α = 82.866 (3)°	T = 173 K
β = 77.123 (3)°	Block, colourless
γ = 69.155 (2)°	0.29 × 0.26 × 0.21 mm
V = 829.78 (7) Å³

Data collection top

Bruker SMART APEXII CCD diffractometer	3833 independent reflections
Radiation source: rotating anode	3452 reflections with I > 2σ(I)
Graphite multilayer monochromator	R_int = 0.033
Detector resolution: 10.0 pixels mm^-1	θ_max = 27.6°, θ_min = 1.8°
φ and ω scans	h = −10→10
Absorption correction: multi-scan (SADABS; Bruker, 2009)	k = −12→12
T_min = 0.664, T_max = 0.746	l = −14→14
14582 measured reflections

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)] = 0.030	Hydrogen site location: difference Fourier map
wR(F²) = 0.104	H-atom parameters constrained
S = 0.87	w = 1/[σ²(F_o²) + (0.1P)²] where P = (F_o² + 2F_c²)/3
3833 reflections	(Δ/σ)_max = 0.001
226 parameters	Δρ_max = 0.37 e Å⁻³
0 restraints	Δρ_min = −0.63 e Å⁻³

Crystal data top

C₂₀H₁₂BrFO₂S	γ = 69.155 (2)°
M_r = 415.27	V = 829.78 (7) Å³
Triclinic, P1	Z = 2
a = 8.1361 (4) Å	Mo Kα radiation
b = 9.8237 (5) Å	µ = 2.62 mm⁻¹
c = 11.4093 (5) Å	T = 173 K
α = 82.866 (3)°	0.29 × 0.26 × 0.21 mm
β = 77.123 (3)°

Data collection top

Bruker SMART APEXII CCD diffractometer	3833 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	3452 reflections with I > 2σ(I)
T_min = 0.664, T_max = 0.746	R_int = 0.033
14582 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.030	0 restraints
wR(F²) = 0.104	H-atom parameters constrained
S = 0.87	Δρ_max = 0.37 e Å⁻³
3833 reflections	Δρ_min = −0.63 e Å⁻³
226 parameters

Special details top

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 > 2sigma(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
Br	−0.21990 (3)	0.22528 (2)	0.998902 (16)	0.03781 (11)
S	0.47916 (5)	0.16534 (4)	0.44461 (4)	0.02033 (12)
F	0.64982 (17)	0.61956 (15)	0.12311 (11)	0.0381 (3)
O1	0.17961 (16)	0.57103 (13)	0.53100 (11)	0.0210 (3)
O2	0.66591 (17)	0.14226 (15)	0.37795 (13)	0.0302 (3)
C1	0.3705 (2)	0.35537 (18)	0.46114 (14)	0.0193 (3)
C2	0.4126 (2)	0.46848 (19)	0.37985 (15)	0.0196 (3)
C3	0.5388 (2)	0.4728 (2)	0.27522 (16)	0.0238 (4)
H3	0.6234	0.3885	0.2413	0.029*
C4	0.5298 (2)	0.6096 (2)	0.22567 (16)	0.0264 (4)
C5	0.4074 (3)	0.7387 (2)	0.27342 (17)	0.0280 (4)
H5	0.4087	0.8278	0.2353	0.034*
C6	0.2835 (2)	0.7350 (2)	0.37772 (16)	0.0245 (4)
H6	0.2004	0.8197	0.4121	0.029*
C7	0.2906 (2)	0.59795 (19)	0.42783 (15)	0.0201 (3)
C8	0.2314 (2)	0.42188 (17)	0.55135 (15)	0.0191 (3)
C9	0.1288 (2)	0.37299 (19)	0.65891 (15)	0.0203 (3)
C10	−0.0123 (3)	0.4752 (2)	0.73078 (17)	0.0273 (4)
H10	−0.0387	0.5740	0.7092	0.033*
C11	−0.1131 (3)	0.4322 (2)	0.83305 (18)	0.0307 (4)
H11	−0.2057	0.5011	0.8804	0.037*
C12	−0.0740 (2)	0.2854 (2)	0.86369 (16)	0.0256 (4)
C13	0.0653 (3)	0.1814 (2)	0.79636 (17)	0.0293 (4)
H13	0.0911	0.0830	0.8194	0.035*
C14	0.1662 (3)	0.2245 (2)	0.69446 (17)	0.0275 (4)
H14	0.2600	0.1546	0.6488	0.033*
C15	0.3563 (2)	0.14738 (19)	0.33775 (17)	0.0217 (3)
C16	0.1896 (2)	0.1320 (2)	0.37783 (19)	0.0289 (4)
H16	0.1418	0.1280	0.4597	0.035*
C17	0.0958 (3)	0.1228 (2)	0.2932 (2)	0.0396 (5)
H17	−0.0171	0.1142	0.3183	0.047*
C18	0.1684 (3)	0.1263 (2)	0.1723 (2)	0.0432 (6)
H18	0.1041	0.1204	0.1164	0.052*
C19	0.3370 (4)	0.1387 (3)	0.1332 (2)	0.0461 (6)
H19	0.3856	0.1406	0.0514	0.055*
C20	0.4327 (3)	0.1481 (2)	0.21686 (18)	0.0347 (5)
H20	0.5465	0.1549	0.1918	0.042*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br	0.03745 (16)	0.05065 (18)	0.02458 (14)	−0.02139 (12)	0.00266 (9)	0.00468 (10)
S	0.0185 (2)	0.0151 (2)	0.0247 (2)	−0.00334 (16)	−0.00247 (16)	−0.00170 (16)
F	0.0399 (7)	0.0428 (7)	0.0292 (6)	−0.0205 (6)	0.0043 (5)	0.0072 (5)
O1	0.0219 (6)	0.0140 (6)	0.0237 (6)	−0.0041 (5)	−0.0017 (5)	0.0004 (4)
O2	0.0171 (6)	0.0280 (7)	0.0422 (8)	−0.0040 (5)	−0.0009 (5)	−0.0096 (6)
C1	0.0199 (8)	0.0158 (8)	0.0213 (8)	−0.0059 (6)	−0.0031 (6)	0.0000 (6)
C2	0.0205 (8)	0.0188 (8)	0.0211 (8)	−0.0085 (7)	−0.0054 (6)	0.0007 (6)
C3	0.0226 (8)	0.0260 (9)	0.0225 (8)	−0.0097 (7)	−0.0014 (7)	−0.0012 (7)
C4	0.0268 (9)	0.0325 (10)	0.0226 (8)	−0.0159 (8)	−0.0036 (7)	0.0044 (7)
C5	0.0328 (10)	0.0262 (10)	0.0292 (9)	−0.0154 (8)	−0.0113 (8)	0.0095 (7)
C6	0.0265 (9)	0.0177 (8)	0.0290 (9)	−0.0069 (7)	−0.0079 (7)	0.0025 (7)
C7	0.0202 (8)	0.0198 (8)	0.0205 (8)	−0.0074 (7)	−0.0045 (6)	0.0008 (6)
C8	0.0201 (8)	0.0133 (8)	0.0235 (8)	−0.0047 (6)	−0.0058 (6)	0.0002 (6)
C9	0.0198 (8)	0.0192 (8)	0.0221 (8)	−0.0072 (7)	−0.0037 (6)	−0.0007 (6)
C10	0.0278 (9)	0.0198 (9)	0.0285 (9)	−0.0040 (7)	−0.0009 (7)	−0.0012 (7)
C11	0.0274 (9)	0.0302 (10)	0.0283 (9)	−0.0060 (8)	0.0027 (7)	−0.0054 (8)
C12	0.0261 (8)	0.0323 (10)	0.0191 (8)	−0.0131 (8)	−0.0015 (7)	0.0015 (7)
C13	0.0345 (10)	0.0234 (9)	0.0283 (9)	−0.0114 (8)	−0.0029 (8)	0.0040 (7)
C14	0.0279 (9)	0.0197 (9)	0.0291 (9)	−0.0061 (7)	0.0024 (7)	−0.0010 (7)
C15	0.0215 (8)	0.0150 (8)	0.0283 (9)	−0.0054 (7)	−0.0053 (7)	−0.0012 (6)
C16	0.0215 (9)	0.0227 (9)	0.0403 (11)	−0.0065 (7)	−0.0011 (8)	−0.0057 (8)
C17	0.0263 (9)	0.0240 (10)	0.0699 (15)	−0.0047 (8)	−0.0149 (10)	−0.0091 (10)
C18	0.0558 (14)	0.0281 (11)	0.0552 (14)	−0.0124 (10)	−0.0337 (12)	−0.0003 (10)
C19	0.0761 (17)	0.0456 (14)	0.0295 (11)	−0.0333 (13)	−0.0178 (11)	0.0040 (10)
C20	0.0426 (12)	0.0387 (12)	0.0288 (10)	−0.0246 (10)	−0.0018 (9)	−0.0005 (8)

Geometric parameters (Å, º) top

Br—C12	1.8961 (18)	C9—C14	1.406 (2)
S—Sⁱ	3.2635 (8)	C10—C11	1.382 (3)
S—O2	1.4903 (13)	C10—H10	0.9300
S—C1	1.7721 (17)	C11—C12	1.378 (3)
S—C15	1.7996 (18)	C11—H11	0.9300
F—C4	1.365 (2)	C12—C13	1.379 (3)
O1—C7	1.375 (2)	C13—C14	1.380 (3)
O1—C8	1.3776 (19)	C13—H13	0.9300
C1—C8	1.374 (2)	C14—H14	0.9300
C1—C2	1.444 (2)	C15—C20	1.381 (3)
C2—C7	1.391 (2)	C15—C16	1.387 (2)
C2—C3	1.397 (2)	C16—C17	1.387 (3)
C3—C4	1.376 (3)	C16—H16	0.9300
C3—H3	0.9300	C17—C18	1.375 (4)
C4—C5	1.389 (3)	C17—H17	0.9300
C5—C6	1.384 (3)	C18—C19	1.388 (4)
C5—H5	0.9300	C18—H18	0.9300
C6—C7	1.382 (2)	C19—C20	1.390 (3)
C6—H6	0.9300	C19—H19	0.9300
C8—C9	1.455 (2)	C20—H20	0.9300
C9—C10	1.401 (2)

O2—S—C1	107.56 (8)	C11—C10—H10	119.3
O2—S—C15	106.43 (8)	C9—C10—H10	119.3
C1—S—C15	96.72 (8)	C12—C11—C10	118.90 (18)
C7—O1—C8	106.98 (13)	C12—C11—H11	120.5
C8—C1—C2	107.73 (15)	C10—C11—H11	120.5
C8—C1—S	126.85 (13)	C11—C12—C13	121.57 (17)
C2—C1—S	125.42 (13)	C11—C12—Br	119.10 (14)
C7—C2—C3	119.78 (16)	C13—C12—Br	119.30 (14)
C7—C2—C1	104.55 (14)	C12—C13—C14	119.45 (18)
C3—C2—C1	135.66 (16)	C12—C13—H13	120.3
C4—C3—C2	115.72 (17)	C14—C13—H13	120.3
C4—C3—H3	122.1	C13—C14—C9	120.77 (18)
C2—C3—H3	122.1	C13—C14—H14	119.6
F—C4—C3	117.95 (18)	C9—C14—H14	119.6
F—C4—C5	117.67 (17)	C20—C15—C16	121.65 (18)
C3—C4—C5	124.38 (17)	C20—C15—S	118.49 (14)
C6—C5—C4	120.07 (17)	C16—C15—S	119.87 (15)
C6—C5—H5	120.0	C17—C16—C15	118.6 (2)
C4—C5—H5	120.0	C17—C16—H16	120.7
C7—C6—C5	116.00 (17)	C15—C16—H16	120.7
C7—C6—H6	122.0	C18—C17—C16	120.5 (2)
C5—C6—H6	122.0	C18—C17—H17	119.8
O1—C7—C6	124.94 (16)	C16—C17—H17	119.8
O1—C7—C2	111.03 (14)	C17—C18—C19	120.6 (2)
C6—C7—C2	124.03 (16)	C17—C18—H18	119.7
C1—C8—O1	109.69 (14)	C19—C18—H18	119.7
C1—C8—C9	135.70 (15)	C18—C19—C20	119.7 (2)
O1—C8—C9	114.61 (14)	C18—C19—H19	120.2
C10—C9—C14	117.93 (16)	C20—C19—H19	120.2
C10—C9—C8	119.97 (16)	C15—C20—C19	119.0 (2)
C14—C9—C8	122.10 (16)	C15—C20—H20	120.5
C11—C10—C9	121.35 (17)	C19—C20—H20	120.5

O2—S—C1—C8	−152.47 (14)	C7—O1—C8—C9	179.29 (13)
C15—S—C1—C8	97.90 (16)	C1—C8—C9—C10	−178.05 (18)
O2—S—C1—C2	28.34 (17)	O1—C8—C9—C10	1.2 (2)
C15—S—C1—C2	−81.29 (15)	C1—C8—C9—C14	2.0 (3)
C8—C1—C2—C7	−0.77 (18)	O1—C8—C9—C14	−178.71 (15)
S—C1—C2—C7	178.55 (12)	C14—C9—C10—C11	−0.5 (3)
C8—C1—C2—C3	178.37 (18)	C8—C9—C10—C11	179.57 (17)
S—C1—C2—C3	−2.3 (3)	C9—C10—C11—C12	−0.6 (3)
C7—C2—C3—C4	−0.9 (2)	C10—C11—C12—C13	1.5 (3)
C1—C2—C3—C4	−179.96 (18)	C10—C11—C12—Br	−176.61 (14)
C2—C3—C4—F	−179.75 (14)	C11—C12—C13—C14	−1.3 (3)
C2—C3—C4—C5	0.6 (3)	Br—C12—C13—C14	176.79 (15)
F—C4—C5—C6	−179.58 (15)	C12—C13—C14—C9	0.2 (3)
C3—C4—C5—C6	0.0 (3)	C10—C9—C14—C13	0.7 (3)
C4—C5—C6—C7	−0.4 (2)	C8—C9—C14—C13	−179.38 (17)
C8—O1—C7—C6	−179.14 (16)	O2—S—C15—C20	−13.32 (18)
C8—O1—C7—C2	0.74 (17)	C1—S—C15—C20	97.26 (17)
C5—C6—C7—O1	179.97 (15)	O2—S—C15—C16	166.15 (15)
C5—C6—C7—C2	0.1 (2)	C1—S—C15—C16	−83.27 (16)
C3—C2—C7—O1	−179.29 (14)	C20—C15—C16—C17	−2.5 (3)
C1—C2—C7—O1	0.02 (17)	S—C15—C16—C17	178.09 (15)
C3—C2—C7—C6	0.6 (2)	C15—C16—C17—C18	1.1 (3)
C1—C2—C7—C6	179.90 (16)	C16—C17—C18—C19	0.2 (3)
C2—C1—C8—O1	1.26 (18)	C17—C18—C19—C20	−0.3 (4)
S—C1—C8—O1	−178.05 (11)	C16—C15—C20—C19	2.4 (3)
C2—C1—C8—C9	−179.43 (17)	S—C15—C20—C19	−178.13 (17)
S—C1—C8—C9	1.3 (3)	C18—C19—C20—C15	−1.0 (4)
C7—O1—C8—C1	−1.24 (17)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º) top

Cg3 is the centroid of the C15–C20 phenyl ring.

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···Cg3ⁱⁱ	0.93	2.85	3.644 (3)	145

Symmetry code: (ii) x, y+1, z.

Experimental details

Crystal data
Chemical formula	C₂₀H₁₂BrFO₂S
M_r	415.27
Crystal system, space group	Triclinic, P1
Temperature (K)	173
a, b, c (Å)	8.1361 (4), 9.8237 (5), 11.4093 (5)
α, β, γ (°)	82.866 (3), 77.123 (3), 69.155 (2)
V (Å³)	829.78 (7)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	2.62
Crystal size (mm)	0.29 × 0.26 × 0.21

Data collection
Diffractometer	Bruker SMART APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.664, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	14582, 3833, 3452
R_int	0.033
(sin θ/λ)_max (Å⁻¹)	0.651

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.104, 0.87
No. of reflections	3833
No. of parameters	226
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.37, −0.63

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 1998).