Crystal structure of 4-(benzo[d]thia­zol-2-yl)-1,2-dimethyl-1H-pyrazol-3(2H)-one

Elboshi, H.A.; Azzam, R.A.; Elgemeie, G.H.; Jones, P.G.

doi:10.1107/S2056989024001257

research communications

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ISSN: 2056-9890

Volume 80| Part 3| March 2024| Pages 289-291

https://doi.org/10.1107/S2056989024001257

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Crystal structure of 4-(benzo[d]thiazol-2-yl)-1,2-dimethyl-1H-pyrazol-3(2H)-one

Heba A. Elboshi,^a Rasha A. Azzam,^a Galal H. Elgemeie ^a and Peter G. Jones ^b ^*

^aChemistry Department, Faculty of Science, Helwan University, Cairo, Egypt, and ^bInstitut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany
^*Correspondence e-mail: p.jones@tu-braunschweig.de

Edited by C. Schulzke, Universität Greifswald, Germany (Received 22 January 2024; accepted 7 February 2024; online 16 February 2024)

In the title compound, C₁₂H₁₁N₃OS, the interplanar angle between the pyrazole and benzothiazole rings is 3.31 (7)°. In the three-dimensional molecular packing, the carbonyl oxygen acts as acceptor to four C—H donors (with one H⋯O as short as 2.25 Å), while one methyl hydrogen is part of the three-centre system H⋯(S, O). A double layer structure parallel to ( $[\overline{1}]$ 01) can be recognized as a subsection of the packing.

Keywords: crystal structure; benzothiazole; pyrazolone; weak hydrogen bonds.

CCDC reference: 2331586

1. Chemical context

Many natural heterocyclic compounds and pharmaceuticals involve benzothiazole moieties and derivatives thereof, which are among the most significant heterocyclic compounds utilized in medicinal chemistry (Bonde et al., 2015 ). In the search for novel and significant therapeutic drugs, benzothiazoles have a wide range of established pharmacological properties (Wang et al., 2009 ), and their derivatives include several structural variants (Rana et al., 2008 ). The application of benzothiazole derivatives in current research and related discoveries is a well-appreciated and quickly growing area of medicinal chemistry (Abdallah et al., 2023 ). As an example, several drugs based on benzothiazole derivatives have been widely utilized in clinical practice to treat a variety of disorders, with a marked therapeutic efficacy (Huang et al., 2009 ).

In the course of our studies, intended to develop syntheses of benzothiazole-based heterocycles for use as pharmaceuticals and pigments (Ahmed et al., 2022 , 2023 ), a variety of 2-pyrimidyl-, 2-pyridyl- and 2-thienyl-benzothiazole compounds with encouraging cytotoxic action have recently been synthesized and their biological activity reported (Azzam et al., 2017 , 2019 , 2022 ).

In line with these findings and our prior research (Metwally et al., 2022a ,b ), the aim of the current investigation was to design and create benzothiazolyl-pyrazole hybrids. The reaction of 2-benzothiazolyl acetohydrazide 1 with N,N-dimethylformamide dimethyl acetal 2 at room temperature led to the synthesis of the unexpected benzothiazole-2-pyrazole derivative 3 in good yield (Fig. 1). The mechanism for the formation of 3 is currently under investigation. In order to establish the structure of the product unambiguously, its crystal structure was determined and is reported here.

Figure 1
The synthesis of the title compound 3.

2. Structural commentary

The structure of compound 3 is shown in Fig. 2, with selected molecular dimensions in Table 1. These may be regarded as normal, within the constraints of linked five-membered rings that necessarily lead to narrow angles within the rings and wide exocyclic angles [up to 127.48 (11)° for C10—C8—C2]. The molecule is essentially planar (except for the methyl hydrogens); the least-squares plane through all non-H atoms has an r.m.s.d. of only 0.037 Å. If the ring systems are regarded separately, the pyrazole and benzothiazole rings have r.m.s.d. values of 0.006 and 0.017 Å, respectively, and an interplanar angle of 3.31 (7)°. The coplanarity leads to a short intramolecular contact S1⋯O1 = 2.9797 (10) Å.

Table 1
Selected geometric parameters (Å, °)

S1—C7A	1.7374 (13)	N2—C10	1.3326 (16)
S1—C2	1.7673 (12)	N3—C2	1.3051 (16)
O1—C9	1.2468 (15)	N3—C3A	1.3879 (16)
N1—N2	1.3766 (14)	C2—C8	1.4348 (17)
N1—C9	1.3772 (16)	C3A—C7A	1.4058 (18)

C7A—S1—C2	88.85 (6)	C7—C7A—S1	128.77 (11)
N2—N1—C9	109.59 (10)	C3A—C7A—S1	109.37 (9)
C10—N2—N1	108.87 (10)	C10—C8—C2	127.48 (11)
C2—N3—C3A	110.45 (11)	C10—C8—C9	107.06 (11)
N3—C2—C8	124.55 (11)	C2—C8—C9	125.46 (11)
N3—C2—S1	115.65 (9)	O1—C9—N1	123.88 (11)
C8—C2—S1	119.80 (9)	O1—C9—C8	130.92 (12)
N3—C3A—C4	125.04 (12)	N1—C9—C8	105.19 (10)
N3—C3A—C7A	115.66 (11)	N2—C10—C8	109.28 (11)

Figure 2
The structure of compound 3 in the crystal. Ellipsoids correspond to 50% probability levels.

3. Supramolecular features

The molecular packing involves five short contacts, four C—H⋯O1 and one C—H⋯S1, that are acceptably linear and may be regarded as `weak' hydrogen bonds (Table 2). The donor atom H12B is part of a three-centre system with acceptors O1 and S1. The contact H12C⋯O1 is remarkably short at 2.25 Å. Additionally, there is a short contact S1⋯N1(x, $[{3\over 2}]$ − y, $[{1\over 2}]$ + z) = 3.4078 (11) Å. A section of the packing is shown in Fig. 3; a ribbon parallel to the b axis and its antiparallel counterpart are shown, which form a double layer parallel to ( $[\overline{1}]$ 01). However, the molecules are further linked parallel to the view direction to give a three-dimensional pattern. There are no Cent–Cent contacts shorter than 3.75 Å and no H⋯Cent contacts shorter than 2.99 Å (Cent = ring centroids).

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C10—H10⋯O1ⁱ	0.95	2.38	3.2055 (15)	145
C11—H11A⋯O1ⁱⁱ	0.98	2.51	3.4368 (16)	158
C12—H12B⋯S1ⁱ	0.98	2.86	3.7142 (13)	146
C12—H12B⋯O1ⁱ	0.98	2.60	3.4696 (16)	148
C12—H12C⋯O1ⁱⁱ	0.98	2.25	3.1966 (16)	163
Symmetry codes: (i) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[x, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ .

Figure 3
A section of the three-dimensional packing of compound 3: two antiparallel ribbons viewed perpendicular to ( $[\overline{1}]$ 01). Contacts to O1 are shown as thick dashed lines and those to S1 as thin dashed lines. Hydrogen atoms not involved in hydrogen bonding are omitted. The atom labels indicate the asymmetric unit.

4. Database survey

The search employed the routine ConQuest (Bruno et al., 2002 ), part of Version 2023.3.0 of the Cambridge Structural Database (Groom et al., 2016 ).

A search for other structures containing a linked pyrazolone/benzothiazole unit as in 3 led to three hits: AZUPIV, with 1-Me, 2-Ph and 5-Me substituents on the pyrazolone ring (Chakib et al., 2011 ), VABFIP (1-allyl, 2-Ph, 5-Me; Chakib et al., 2010a ) and VABFOV (1-propynyl, 2-Ph, 5-Me; Chakib et al., 2010b ). The interplanar angles in these compounds are 6.1 (1), 7.9 (2) and 4.7 (1)°, respectively.

5. Synthesis and crystallization

A mixture of 2-benzothiazolyl acetohydrazide 1 (0.01 mol) and N,N-dimethylformamide dimethyl acetal 2 (0.02 mol) was stirred at room temperature for 1 h. The excess acetal was distilled off under reduced pressure; the solid product was washed with a mixture of petroleum ether and diethyl ether (1:1) and then crystallized from ethanol.

Yellow solid; yield 85%; m.p. 414 K; IR (KBr, cm⁻¹): ν 3068 (aromatic CH), 2930 (methyl CH), 1620 (C=O), 1598 (C=N); ¹H NMR (400 MHz, DMSO-d₆): δ 3.80 (s, 3H, CH₃), 4.01 (s, 3H, CH₃), 7.34 (t, J = 7.2 Hz, 1H, benzothiazole H), 7.46 (t, J = 7.2 Hz, 1H, benzothiazole H), 7.89 (d, J = 7.6 Hz, 1H, benzothiazole H), 8.03 (d, J = 8.0 Hz, 1H, benzothiazole H), 8.35 (s, 1H, pyrazolone H). Analysis calculated for C₁₂H₁₁N₃OS (245.30): C 58.76, H 4.52, N 17.13, S 13.07. Found C 58.66, H 4.40, N 17.08, S 13.14%.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The methyl groups were included as idealized rigid groups (C—H 0.98 Å, H—C—H 109.5°) allowed to rotate but not tip (command ‘AFIX 137’). Other hydrogen atoms were included using a riding model starting from calculated positions (C—H = 0.95 Å). The U_iso(H) values were fixed at 1.5 × U_eq of the parent carbon atoms for the methyl group and 1.2 × U_eq for other hydrogens. One reflection clearly in error (F_o² >> F_c²) was omitted from the refinement.

Table 3
Experimental details

Crystal data
Chemical formula	C₁₂H₁₁N₃OS
M_r	245.30
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	8.78308 (12), 11.66215 (16), 11.00169 (15)
β (°)	97.9460 (12)
V (Å³)	1116.08 (3)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	2.47
Crystal size (mm)	0.15 × 0.10 × 0.03

Data collection
Diffractometer	XtaLAB Synergy
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2021 $[Rigaku OD (2021). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ )
T_min, T_max	0.731, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	46018, 2367, 2280
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.634

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.081, 1.07
No. of reflections	2367
No. of parameters	156
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.36
Computer programs: CrysAlis PRO (Rigaku OD, 2021 $[Rigaku OD (2021). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ ), SHELXT (Sheldrick, 2015a ), SHELXL2019/3 (Sheldrick, 2015b ) and XP (Bruker, 1998 ).

Supporting information

CCDC reference: 2331586

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989024001257/yz2050sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989024001257/yz2050Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989024001257/yz2050Isup3.cml

checkCIF report

Computing details top

4-(Benzo[d]thiazol-2-yl)-1,2-dimethyl-1H-pyrazol-3(2H)-one top

Crystal data top

C₁₂H₁₁N₃OS	F(000) = 512
M_r = 245.30	D_x = 1.460 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54184 Å
a = 8.78308 (12) Å	Cell parameters from 32695 reflections
b = 11.66215 (16) Å	θ = 5.1–77.4°
c = 11.00169 (15) Å	µ = 2.47 mm⁻¹
β = 97.9460 (12)°	T = 100 K
V = 1116.08 (3) Å³	Plate, pale yellow
Z = 4	0.15 × 0.10 × 0.03 mm

Data collection top

XtaLAB Synergy diffractometer	2367 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Cu) X-ray Source	2280 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.037
Detector resolution: 10.0000 pixels mm^-1	θ_max = 77.6°, θ_min = 5.1°
ω scans	h = −11→11
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2021)	k = −14→14
T_min = 0.731, T_max = 1.000	l = −13→13
46018 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.030	H-atom parameters constrained
wR(F²) = 0.081	w = 1/[σ²(F_o²) + (0.0434P)² + 0.4017P] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max = 0.001
2367 reflections	Δρ_max = 0.28 e Å⁻³
156 parameters	Δρ_min = −0.36 e Å⁻³
0 restraints

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.

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

	x	y	z	U_iso*/U_eq
S1	0.63680 (4)	0.71933 (2)	0.56971 (3)	0.02849 (11)
O1	0.40109 (11)	0.79924 (7)	0.36636 (8)	0.0311 (2)
N1	0.33946 (12)	0.67380 (9)	0.20375 (9)	0.0266 (2)
N2	0.39212 (12)	0.56914 (8)	0.16939 (9)	0.0268 (2)
N3	0.73240 (12)	0.52608 (9)	0.48701 (10)	0.0288 (2)
C2	0.63324 (14)	0.60863 (10)	0.45966 (11)	0.0259 (2)
C3A	0.82145 (14)	0.54730 (11)	0.59907 (12)	0.0286 (3)
C4	0.94097 (16)	0.47710 (12)	0.65366 (13)	0.0350 (3)
H4	0.964387	0.407342	0.615676	0.042*
C5	1.02447 (16)	0.51076 (13)	0.76368 (13)	0.0382 (3)
H5	1.106443	0.463964	0.800905	0.046*
C6	0.98995 (16)	0.61274 (13)	0.82092 (13)	0.0378 (3)
H6	1.049479	0.634461	0.896126	0.045*
C7	0.87033 (16)	0.68266 (12)	0.76977 (12)	0.0339 (3)
H7	0.845688	0.751223	0.809420	0.041*
C7A	0.78751 (14)	0.64905 (11)	0.65836 (11)	0.0284 (3)
C8	0.52570 (14)	0.61387 (10)	0.34907 (11)	0.0258 (2)
C9	0.42066 (14)	0.70641 (10)	0.31446 (11)	0.0258 (2)
C10	0.50225 (14)	0.53273 (10)	0.25637 (11)	0.0267 (3)
H10	0.556198	0.462239	0.255040	0.032*
C11	0.22779 (15)	0.74119 (11)	0.12468 (12)	0.0313 (3)
H11A	0.260232	0.747813	0.043243	0.047*
H11B	0.220412	0.817829	0.159925	0.047*
H11C	0.127222	0.703488	0.117398	0.047*
C12	0.32435 (15)	0.51086 (11)	0.05843 (12)	0.0301 (3)
H12A	0.214516	0.498538	0.061218	0.045*
H12B	0.375258	0.436717	0.052279	0.045*
H12C	0.337515	0.557948	−0.013158	0.045*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.03690 (19)	0.02172 (17)	0.02606 (17)	0.00157 (11)	0.00148 (12)	−0.00057 (10)
O1	0.0411 (5)	0.0228 (4)	0.0290 (4)	0.0033 (4)	0.0038 (4)	−0.0025 (3)
N1	0.0317 (5)	0.0205 (5)	0.0273 (5)	0.0015 (4)	0.0028 (4)	−0.0008 (4)
N2	0.0334 (5)	0.0198 (5)	0.0267 (5)	0.0006 (4)	0.0030 (4)	−0.0013 (4)
N3	0.0314 (5)	0.0253 (5)	0.0295 (5)	0.0014 (4)	0.0038 (4)	0.0007 (4)
C2	0.0308 (6)	0.0210 (5)	0.0265 (6)	−0.0019 (4)	0.0062 (5)	0.0007 (4)
C3A	0.0287 (6)	0.0278 (6)	0.0294 (6)	−0.0021 (5)	0.0044 (5)	0.0023 (5)
C4	0.0338 (6)	0.0336 (7)	0.0371 (7)	0.0045 (5)	0.0033 (5)	0.0025 (5)
C5	0.0315 (7)	0.0431 (8)	0.0386 (7)	0.0022 (6)	−0.0002 (5)	0.0073 (6)
C6	0.0355 (7)	0.0437 (8)	0.0321 (7)	−0.0076 (6)	−0.0025 (5)	0.0034 (6)
C7	0.0380 (7)	0.0318 (7)	0.0312 (6)	−0.0065 (5)	0.0025 (5)	0.0005 (5)
C7A	0.0309 (6)	0.0258 (6)	0.0286 (6)	−0.0034 (5)	0.0046 (5)	0.0037 (5)
C8	0.0316 (6)	0.0204 (5)	0.0258 (6)	−0.0008 (4)	0.0051 (5)	0.0010 (4)
C9	0.0305 (6)	0.0228 (6)	0.0247 (6)	−0.0013 (4)	0.0054 (5)	0.0015 (4)
C10	0.0324 (6)	0.0206 (6)	0.0273 (6)	0.0003 (5)	0.0045 (5)	0.0017 (5)
C11	0.0353 (7)	0.0270 (6)	0.0303 (6)	0.0049 (5)	0.0000 (5)	−0.0002 (5)
C12	0.0374 (7)	0.0239 (6)	0.0281 (6)	−0.0029 (5)	0.0014 (5)	−0.0023 (5)

Geometric parameters (Å, º) top

S1—C7A	1.7374 (13)	C5—C6	1.398 (2)
S1—C2	1.7673 (12)	C5—H5	0.9500
O1—C9	1.2468 (15)	C6—C7	1.386 (2)
N1—N2	1.3766 (14)	C6—H6	0.9500
N1—C9	1.3772 (16)	C7—C7A	1.3923 (18)
N1—C11	1.4493 (16)	C7—H7	0.9500
N2—C10	1.3326 (16)	C8—C10	1.3856 (17)
N2—C12	1.4511 (15)	C8—C9	1.4365 (17)
N3—C2	1.3051 (16)	C10—H10	0.9500
N3—C3A	1.3879 (16)	C11—H11A	0.9800
C2—C8	1.4348 (17)	C11—H11B	0.9800
C3A—C4	1.3995 (18)	C11—H11C	0.9800
C3A—C7A	1.4058 (18)	C12—H12A	0.9800
C4—C5	1.383 (2)	C12—H12B	0.9800
C4—H4	0.9500	C12—H12C	0.9800

C7A—S1—C2	88.85 (6)	C7A—C7—H7	121.1
N2—N1—C9	109.59 (10)	C7—C7A—C3A	121.85 (12)
N2—N1—C11	122.76 (10)	C7—C7A—S1	128.77 (11)
C9—N1—C11	127.29 (10)	C3A—C7A—S1	109.37 (9)
C10—N2—N1	108.87 (10)	C10—C8—C2	127.48 (11)
C10—N2—C12	128.87 (10)	C10—C8—C9	107.06 (11)
N1—N2—C12	122.15 (10)	C2—C8—C9	125.46 (11)
C2—N3—C3A	110.45 (11)	O1—C9—N1	123.88 (11)
N3—C2—C8	124.55 (11)	O1—C9—C8	130.92 (12)
N3—C2—S1	115.65 (9)	N1—C9—C8	105.19 (10)
C8—C2—S1	119.80 (9)	N2—C10—C8	109.28 (11)
N3—C3A—C4	125.04 (12)	N2—C10—H10	125.4
N3—C3A—C7A	115.66 (11)	C8—C10—H10	125.4
C4—C3A—C7A	119.29 (12)	N1—C11—H11A	109.5
C5—C4—C3A	119.03 (13)	N1—C11—H11B	109.5
C5—C4—H4	120.5	H11A—C11—H11B	109.5
C3A—C4—H4	120.5	N1—C11—H11C	109.5
C4—C5—C6	120.93 (13)	H11A—C11—H11C	109.5
C4—C5—H5	119.5	H11B—C11—H11C	109.5
C6—C5—H5	119.5	N2—C12—H12A	109.5
C7—C6—C5	121.11 (13)	N2—C12—H12B	109.5
C7—C6—H6	119.4	H12A—C12—H12B	109.5
C5—C6—H6	119.4	N2—C12—H12C	109.5
C6—C7—C7A	117.78 (13)	H12A—C12—H12C	109.5
C6—C7—H7	121.1	H12B—C12—H12C	109.5

C9—N1—N2—C10	1.41 (13)	C4—C3A—C7A—S1	179.30 (10)
C11—N1—N2—C10	174.94 (11)	C2—S1—C7A—C7	177.82 (13)
C9—N1—N2—C12	177.72 (11)	C2—S1—C7A—C3A	−0.88 (9)
C11—N1—N2—C12	−8.75 (17)	N3—C2—C8—C10	3.3 (2)
C3A—N3—C2—C8	178.92 (11)	S1—C2—C8—C10	−176.73 (10)
C3A—N3—C2—S1	−1.06 (13)	N3—C2—C8—C9	−176.88 (11)
C7A—S1—C2—N3	1.17 (10)	S1—C2—C8—C9	3.10 (17)
C7A—S1—C2—C8	−178.81 (10)	N2—N1—C9—O1	177.75 (11)
C2—N3—C3A—C4	−178.36 (12)	C11—N1—C9—O1	4.6 (2)
C2—N3—C3A—C7A	0.34 (15)	N2—N1—C9—C8	−1.34 (13)
N3—C3A—C4—C5	177.54 (13)	C11—N1—C9—C8	−174.50 (11)
C7A—C3A—C4—C5	−1.12 (19)	C10—C8—C9—O1	−178.19 (13)
C3A—C4—C5—C6	0.6 (2)	C2—C8—C9—O1	1.9 (2)
C4—C5—C6—C7	0.5 (2)	C10—C8—C9—N1	0.80 (13)
C5—C6—C7—C7A	−1.2 (2)	C2—C8—C9—N1	−179.06 (11)
C6—C7—C7A—C3A	0.65 (19)	N1—N2—C10—C8	−0.86 (13)
C6—C7—C7A—S1	−177.91 (10)	C12—N2—C10—C8	−176.86 (12)
N3—C3A—C7A—C7	−178.29 (11)	C2—C8—C10—N2	179.88 (12)
C4—C3A—C7A—C7	0.49 (19)	C9—C8—C10—N2	0.03 (14)
N3—C3A—C7A—S1	0.52 (14)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C10—H10···O1ⁱ	0.95	2.38	3.2055 (15)	145
C11—H11A···O1ⁱⁱ	0.98	2.51	3.4368 (16)	158
C12—H12B···S1ⁱ	0.98	2.86	3.7142 (13)	146
C12—H12B···O1ⁱ	0.98	2.60	3.4696 (16)	148
C12—H12C···O1ⁱⁱ	0.98	2.25	3.1966 (16)	163

Symmetry codes: (i) −x+1, y−1/2, −z+1/2; (ii) x, −y+3/2, z−1/2.

Acknowledgements

The authors acknowledge support by the Open Access Publication Funds of the Technical University of Braunschweig.

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