Crystal structure of cyclo-tris­(μ-3,4,5,6-tetra­fluoro-o-phenyl­ene-κ2C1:C2)trimercury–tetra­cyano­ethyl­ene (1/1)

Castañeda, R.; Timofeeva, T.V.; Khrustalev, V.N.

doi:10.1107/S2056989015019350

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Volume 71| Part 11| November 2015| Pages 1375-1378

https://doi.org/10.1107/S2056989015019350

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Crystal structure of cyclo-tris(μ-3,4,5,6-tetrafluoro-o-phenylene-κ²C¹:C²)trimercury–tetracyanoethylene (1/1)

Raúl Castañeda,^a Tatiana V. Timofeeva ^a ^* and Victor N. Khrustalev ^a,^b

^aDepartment of Chemistry & Biology, New Mexico Highlands University, 803 University Ave., Las Vegas, NM 87701, USA, and ^bInorganic Chemistry Department, Peoples' Friendship University of Russia, 6 Miklukho-Maklay St, Moscow, 117198, Russian Federation
^*Correspondence e-mail: tvtimofeeva@nmhu.edu

Edited by P. Roussel, ENSCL, France (Received 8 August 2015; accepted 13 October 2015; online 24 October 2015)

The title compound, [Hg₃(C₆F₄)₃]·C₆N₄, contains one molecule of tetracyanoethylene B per one molecule of mercury macrocycle A, i.e., A•B, and crystallizes in the monoclinic space group C2/c. Macrocycle A and molecule B both occupy special positions on a twofold rotation axis and the inversion centre, respectively. The supramolecular unit [A•B] is built by the simultaneous coordination of one of the nitrile N atoms of B to the three mercury atoms of the macrocycle A. The Hg⋯N distances range from 2.990 (4) to 3.030 (4) Å and are very close to those observed in the related adducts of the macrocycle A with other nitrile derivatives. The molecule of B is almost perpendicular to the mean plane of the macrocycle A at the dihedral angle of 88.20 (5)°. The donor–acceptor Hg⋯N interactions do not affect the C≡N bond lengths [1.136 (6) and 1.140 (6) Å]. The trans nitrile group of B coordinates to another macrocycle A, forming an infinite mixed-stack [A•B]_∞ architecture toward [101]. The remaining N atoms of two nitrile groups of B are not engaged in any donor–acceptor interactions. In the crystal, the mixed stacks are held together by intermolecular C—F⋯C≡N secondary interactions [2.846 (5)–2.925 (5) Å].

Keywords: crystal structure; trimeric perfluoro-o-phenylene mercury; tetracyanoethylene; complexation; X-ray diffraction; TGA.

CCDC reference: 1430883

1. Chemical context

Trimeric perfluoro-o-phenylene mercury (A) is a versatile Lewis acid that is applied for complexation with different substrates, in particular, for the obtaining of charge-transfer complexes based on donor–acceptor intermolecular interactions (Hasegawa et al., 2004 ). Importantly, some physical properties of the guest substrates can change upon complexation. For example, unusual optical properties of the organic molecules in supramolecular complexes with macrocycle A have previously been observed (Haneline et al., 2002 ; Elbjeirami et al., 2007 ; Filatov et al., 2009 , 2011 ). Moreover, using complexation with A, the stabilization of different organic (diphenylpolyynes; Taylor & Gabbaï, 2006 ; Taylor et al., 2008 ) and metal-organic (nickelocene; Haneline & Gabbaï, 2004a ) molecules was achieved under ambient conditions. In this paper, a complex of A with tetracyanoethylene (B) – an unstable dienophilic (σ-electron donor and π-electron acceptor) compound – [Hg₃(C₆F₄)₃]·C₆N₄, (I), was prepared and studied by X-ray diffraction analysis to get a deeper understanding of the complexation process.

2. Structural commentary

Complex (I) contains one molecule of tetracyanoethylene B per one molecule of the mercury macrocycle A, i.e., C₁₈F₁₂Hg₃·C₆N₄ (A•B), and crystallizes in the monoclinic space group C2/c. Both macrocycle A and the molecule of B occupy special positions on a twofold rotation axis and inversion centre, respectively. The supramolecular unit of (I) is built by the simultaneous coordination of the nitrile N1 nitrogen atom of B to the three mercury atoms of the macrocycle A (Fig. 1). The Hg⋯N distances range from 2.990 (4) to 3.030 (4) Å and are very close to those observed in related adducts of macrocycle A with other nitrile derivatives: acetonitrile [2.93 (1)–2.99 (1) Å], acrylonitrile [2.87 (1)–2.96 (1) Å] and benzonitrile [2.97 (1)–3.13 (1) Å] (Tikhonova et al., 2000 ) and 7,7,8,8-tetracyanoquinodimethane (II) [3.102 (11)–3.134 (11) Å] (Haneline & Gabbaï, 2004b ). Thus, the N1 nitrogen atom is essentially equidistant to the three Lewis acidic sites of the macrocycle A. The molecule of B is almost perpendicular to the mean plane of macrocycle A, making a dihedral angle of 88.20 (5)°. It is very important to point out that the donor–acceptor Hg⋯N interactions do not affect the C≡N bond lengths [1.136 (6) and 1.140 (6) Å].

Figure 1
The supramolecular unit of complex (I) (A•B). Displacement ellipsoids are drawn at the 50% probability level. Dashed lines indicate the intermolecular secondary Hg⋯N interactions. [Symmetry codes: (i) 1 − x, y, $[{1\over 2}]$ − z; (ii) $[{3\over 2}]$ − x, $[{3\over 2}]$ − y, 1 − z.]

Taking into account the intrinsic C_i symmetry of B, the trans nitrile group of this molecule coordinates to another macrocycle A, forming an infinite mixed-stack [A•B]_∞ architecture (Fig. 2). The remaining nitrogen atoms of the two nitrile groups of B are not engaged in any donor–acceptor interactions.

Figure 2
The infinite mixed-stack [A•B]_∞ architecture of (I). Dashed lines indicate the intermolecular secondary Hg⋯N interactions.

3. Supramolecular features

In the crystal, the mixed stacks toward [101] are held together by intermolecular C—F⋯C≡N secondary interactions [F2⋯C11ⁱⁱⁱ 2.864 (5), F5⋯C12^iv 2.846 (5) and F6⋯C11^v 2.925 (5) Å; symmetry codes: (iii) − $[{1\over 2}]$ + x, $[{1\over 2}]$ + y, z; (iv) 1 − x, 1 − y, 1 − z; (v) − $[{1\over 2}]$ + x, − $[{1\over 2}]$ + y, z] (Fig. 3).

Figure 3
Crystal packing of complex (I) along the b axis, showing the infinite mixed stacks toward [101]. Dashed lines indicate the intermolecular secondary Hg⋯N and F⋯C interactions.

4. Comparison with compound (II)

It is interesting to note that the crystal structures of (I) and (II) are very similar. In both complexes, the guest molecules of tetracyanoethylene B and tetracyanoquinodimethane C are arranged perpendicularly to macrocycle A, with the same coordination mode of the trans nitrile groups to the three mercury atoms (Fig. 4). However, the supramolecular unit in (I) is A•B (a 1:1 ratio), whereas that in (II) is A•C•A (a 2:1 ratio) (Fig. 4). Beside the molecules of C, complex (II) includes the additional solvate CS₂ (D) molecules. The molecules of D participate in the construction of the supramolecular architecture of (II), resulting in infinite mixed stacks [A•C•A•1.5D]_∞ (Fig. 4). Remarkably, the total number of donor–acceptor intermolecular interactions within the infinite mixed stacks of (I) and (II) is equal ([12 Hg⋯N]_∞ and [6 Hg⋯N + 6 Hg⋯S]_∞, respectively).

Figure 4
The supramolecular structure of complex (II) ([A•C•A•1.5D]_∞). Dashed lines indicate the intermolecular secondary Hg⋯N interactions.

5. TGA analysis

Despite complexes (I) and (II) being structural analogs, they are substantially different in their chemical stability. The crystalline complex (II) decomposes over a few days, while complex (I) is stable in the solid state for several months under ambient conditions. As free B decomposes rapidly upon reaction with moisture to produce toxic hydrogen cyanide, the high chemical stability of complex (I) is surprising. Moreover, the thermal stability of complex (I) has been studied by thermogravimetric analysis (TGA) which revealed that, upon complexation, tetracyanoethylene is stable to higher temperatures (Fig. 5). So, the free compound B starts to decompose at 363 K, but, being incorporated into the supramolecular complex (I), B is stable up to 393 K. Complex (I) decomposes in two different steps. The first step of a 18.3% weight loss is attributed to molecule B because the much lower decomposition temperature of this molecule compared to macrocycle A. Consequently, the second weight loss of 81.7% is attributed to decomposition of macrocycle A. The complete decomposition of the free B is complete at 445 K; however, its final decomposition temperature is equal to 467 K within the supramolecular complex (I). Final decomposition of complex (I) occurs at 573 K, and is likely due decomposition of macrocycle A.

Figure 5
TGA diagram of free B (in red) and complex (I) (in blue).

It is known that tetracyanoethylene is used not only as a component of charge-transfer complexes for organic electronics, but also in the preparation of organic magnets (Kao et al., 2012 ). Consequently, the increase of its thermal stability attracts special attention in the manufacturing of organic materials. The complexation method described here could help to solve this problem.

6. Synthesis and crystallization

Trimeric perfluoro-o-phenylene mercury was synthesized according to the procedure described previously (Sartori & Golloch, 1968 ), and purified by recrystallization in dichloromethane (Filatov et al., 2009). Tetracyanoethylene was acquired from TCI America. All solvents were HPLC grade and used without any further purification. Thermogravimetric analysis was performed with a Hitachi STA7200 SII NanoTechnology instrument (an aluminum crucible (45 mL) was used; heating rate was 10 K min⁻¹).

Stoichiometric amounts of trimeric perfluoro-o-phenylene mercury (63.8 mg, 59.6 mmol) and tetracyanoethylene (7.7 mg, 59.6 mmol) were dissolved in dichloromethane in separate tubes using ultrasonication. The contents of the tubes were mixed carefully, and then left for slow evaporation of the solvents. Complex (I) was obtained as yellow prismatic crystals, m.p. = 499–500 K.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. There is a high positive residual density of 1.19–1.78 e Å⁻³ near the Hg1 and Hg2 atoms due to considerable absorption effects which could not be completely corrected.

Table 1
Experimental details

Crystal data
Chemical formula	[Hg₃(C₆F₄)₃]·C₆N₄
M_r	1174.05
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	100
a, b, c (Å)	10.5658 (11), 13.8297 (15), 16.7166 (18)
β (°)	90.575 (1)
V (Å³)	2442.5 (5)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	18.93
Crystal size (mm)	0.15 × 0.15 × 0.10

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2003 )
T_min, T_max	0.150, 0.250
No. of measured, independent and observed [I > 2σ(I)] reflections	13813, 3560, 3404
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.055, 1.06
No. of reflections	3560
No. of parameters	195
Δρ_max, Δρ_min (e Å⁻³)	1.78, −1.70
Computer programs: APEX2 (Bruker, 2005 ), SAINT (Bruker, 2001 ), SHELXTL (Sheldrick, 2008 ) and SHELXL2014 (Sheldrick, 2015 ).

Supporting information

CCDC reference: 1430883

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S2056989015019350/ru2064sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989015019350/ru2064Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

cyclo-Tris(µ-3,4,5,6-tetrafluoro-o-phenylene-κ²C¹:C²)trimercury–tetracyanoethylene (1/1) top

Crystal data top

[Hg₃(C₆F₄)₃]·C₆N₄	F(000) = 2080
M_r = 1174.05	D_x = 3.193 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.5658 (11) Å	Cell parameters from 9624 reflections
b = 13.8297 (15) Å	θ = 4.4–32.7°
c = 16.7166 (18) Å	µ = 18.93 mm⁻¹
β = 90.575 (1)°	T = 100 K
V = 2442.5 (5) Å³	Prism, light-yellow
Z = 4	0.15 × 0.15 × 0.10 mm

Data collection top

Bruker APEXII CCD diffractometer	3404 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.036
φ and ω scans	θ_max = 30.0°, θ_min = 4.4°
Absorption correction: multi-scan (SADABS; Bruker, 2003)	h = −14→14
T_min = 0.150, T_max = 0.250	k = −19→19
13813 measured reflections	l = −23→23
3560 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.023	Secondary atom site location: difference Fourier map
wR(F²) = 0.055	w = 1/[σ²(F_o²) + (0.0191P)² + 19.1P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max = 0.002
3560 reflections	Δρ_max = 1.78 e Å⁻³
195 parameters	Δρ_min = −1.70 e Å⁻³

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.

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

	x	y	z	U_iso*/U_eq
Hg1	0.5000	0.83281 (2)	0.2500	0.01573 (6)
Hg2	0.36631 (2)	0.60249 (2)	0.31557 (2)	0.01493 (5)
F1	0.3423 (3)	0.9966 (2)	0.33993 (17)	0.0259 (6)
F2	0.1469 (3)	0.98904 (19)	0.44275 (17)	0.0267 (6)
F3	0.0409 (3)	0.8182 (2)	0.48130 (17)	0.0253 (5)
F4	0.1388 (3)	0.65100 (19)	0.42523 (17)	0.0247 (5)
F5	0.3016 (3)	0.38265 (19)	0.35217 (16)	0.0240 (5)
F6	0.4034 (3)	0.21483 (18)	0.30301 (17)	0.0238 (5)
C1	0.3490 (4)	0.8248 (3)	0.3293 (3)	0.0186 (7)
C2	0.2968 (4)	0.9087 (3)	0.3601 (3)	0.0198 (8)
C3	0.1952 (4)	0.9069 (3)	0.4121 (3)	0.0199 (8)
C4	0.1415 (4)	0.8193 (3)	0.4332 (3)	0.0191 (8)
C5	0.1927 (4)	0.7350 (3)	0.4030 (2)	0.0177 (7)
C6	0.2958 (4)	0.7350 (3)	0.3517 (2)	0.0153 (7)
C7	0.4474 (4)	0.4743 (3)	0.2765 (2)	0.0161 (7)
C8	0.4008 (4)	0.3863 (3)	0.3008 (2)	0.0173 (7)
C9	0.4501 (4)	0.2987 (3)	0.2762 (3)	0.0189 (8)
N1	0.6254 (4)	0.6785 (3)	0.3521 (2)	0.0213 (7)
N2	0.9176 (4)	0.5836 (3)	0.5355 (3)	0.0289 (8)
C10	0.7588 (4)	0.7081 (3)	0.4799 (2)	0.0165 (7)
C11	0.6861 (4)	0.6895 (3)	0.4081 (2)	0.0174 (7)
C12	0.8478 (4)	0.6369 (3)	0.5080 (2)	0.0198 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.01452 (9)	0.01481 (10)	0.01793 (10)	0.000	0.00398 (7)	0.000
Hg2	0.01430 (7)	0.01349 (8)	0.01709 (8)	0.00109 (4)	0.00400 (5)	0.00000 (5)
F1	0.0273 (13)	0.0178 (12)	0.0327 (14)	−0.0010 (10)	0.0092 (11)	0.0003 (10)
F2	0.0296 (14)	0.0186 (13)	0.0321 (14)	0.0050 (10)	0.0088 (11)	−0.0055 (10)
F3	0.0209 (12)	0.0275 (14)	0.0277 (13)	0.0033 (10)	0.0111 (10)	−0.0001 (11)
F4	0.0243 (13)	0.0192 (12)	0.0308 (14)	−0.0003 (10)	0.0110 (10)	0.0012 (10)
F5	0.0237 (13)	0.0204 (13)	0.0281 (13)	−0.0003 (10)	0.0139 (10)	0.0032 (10)
F6	0.0251 (13)	0.0132 (12)	0.0333 (14)	−0.0026 (9)	0.0073 (11)	0.0029 (10)
C1	0.0174 (18)	0.0188 (19)	0.0195 (18)	0.0010 (14)	0.0016 (14)	0.0010 (14)
C2	0.0200 (19)	0.0171 (19)	0.0225 (19)	0.0003 (14)	0.0045 (15)	−0.0001 (15)
C3	0.0190 (18)	0.0184 (19)	0.0223 (19)	0.0091 (14)	0.0018 (15)	−0.0041 (15)
C4	0.0142 (17)	0.023 (2)	0.0206 (18)	0.0024 (14)	0.0054 (14)	−0.0003 (15)
C5	0.0181 (18)	0.0180 (18)	0.0171 (17)	0.0014 (14)	0.0023 (14)	0.0010 (14)
C6	0.0142 (16)	0.0158 (18)	0.0161 (17)	0.0034 (13)	0.0031 (13)	−0.0007 (13)
C7	0.0148 (17)	0.0149 (17)	0.0186 (17)	0.0038 (13)	0.0053 (14)	0.0002 (14)
C8	0.0159 (17)	0.0188 (19)	0.0173 (17)	0.0026 (14)	0.0035 (14)	0.0019 (14)
C9	0.0177 (18)	0.0161 (18)	0.0228 (19)	−0.0020 (14)	0.0001 (15)	0.0018 (15)
N1	0.0216 (17)	0.0193 (17)	0.0231 (17)	−0.0011 (13)	0.0044 (13)	0.0001 (13)
N2	0.028 (2)	0.028 (2)	0.031 (2)	0.0051 (16)	0.0072 (16)	0.0016 (16)
C10	0.0143 (16)	0.0169 (18)	0.0184 (17)	−0.0012 (13)	0.0030 (13)	0.0010 (14)
C11	0.0182 (18)	0.0166 (18)	0.0174 (17)	−0.0001 (14)	0.0036 (14)	−0.0011 (14)
C12	0.0196 (18)	0.0195 (19)	0.0205 (18)	0.0001 (15)	0.0030 (14)	−0.0006 (15)

Geometric parameters (Å, º) top

Hg1—C1	2.087 (4)	C2—C3	1.389 (6)
Hg1—N1	3.030 (4)	C3—C4	1.385 (6)
Hg2—C6	2.071 (4)	C4—C5	1.382 (6)
Hg2—C7	2.077 (4)	C5—C6	1.394 (5)
Hg2—N1	2.990 (4)	C7—C8	1.375 (6)
F1—C2	1.351 (5)	C7—C7ⁱ	1.429 (7)
F2—C3	1.348 (5)	C8—C9	1.384 (6)
F3—C4	1.340 (4)	C9—C9ⁱ	1.377 (8)
F4—C5	1.347 (5)	N1—C11	1.140 (6)
F5—C8	1.363 (5)	N2—C12	1.136 (6)
F6—C9	1.339 (5)	C10—C10ⁱⁱ	1.355 (8)
C1—C2	1.387 (6)	C10—C12	1.437 (6)
C1—C6	1.415 (6)	C10—C11	1.441 (6)

C1—Hg1—C1ⁱ	173.9 (2)	C1—C6—Hg2	123.7 (3)
C6—Hg2—C7	176.24 (16)	C8—C7—C7ⁱ	117.8 (2)
C2—C1—C6	118.4 (4)	C8—C7—Hg2	120.8 (3)
C2—C1—Hg1	120.0 (3)	C7ⁱ—C7—Hg2	121.39 (11)
C6—C1—Hg1	121.6 (3)	F5—C8—C7	119.9 (3)
F1—C2—C1	121.1 (4)	F5—C8—C9	116.7 (4)
F1—C2—C3	116.8 (4)	C7—C8—C9	123.4 (4)
C1—C2—C3	122.1 (4)	F6—C9—C9ⁱ	120.0 (2)
F2—C3—C4	118.9 (4)	F6—C9—C8	121.2 (4)
F2—C3—C2	121.4 (4)	C9ⁱ—C9—C8	118.8 (2)
C4—C3—C2	119.7 (4)	C11—N1—Hg2	136.2 (3)
F3—C4—C5	121.7 (4)	C11—N1—Hg1	127.4 (3)
F3—C4—C3	119.5 (4)	Hg2—N1—Hg1	74.82 (9)
C5—C4—C3	118.9 (4)	C10ⁱⁱ—C10—C12	121.1 (5)
F4—C5—C4	117.3 (4)	C10ⁱⁱ—C10—C11	119.4 (5)
F4—C5—C6	120.3 (4)	C12—C10—C11	119.5 (4)
C4—C5—C6	122.4 (4)	N1—C11—C10	176.9 (5)
C5—C6—C1	118.6 (4)	N2—C12—C10	175.2 (5)
C5—C6—Hg2	117.7 (3)

C6—C1—C2—F1	−179.0 (4)	F4—C5—C6—C1	179.4 (4)
Hg1—C1—C2—F1	−0.2 (6)	C4—C5—C6—C1	−0.6 (6)
C6—C1—C2—C3	0.3 (6)	F4—C5—C6—Hg2	−2.5 (5)
Hg1—C1—C2—C3	179.1 (3)	C4—C5—C6—Hg2	177.5 (3)
F1—C2—C3—F2	−1.9 (6)	C2—C1—C6—C5	0.7 (6)
C1—C2—C3—F2	178.8 (4)	Hg1—C1—C6—C5	−178.1 (3)
F1—C2—C3—C4	177.9 (4)	C2—C1—C6—Hg2	−177.2 (3)
C1—C2—C3—C4	−1.4 (7)	Hg1—C1—C6—Hg2	4.0 (5)
F2—C3—C4—F3	2.0 (6)	C7ⁱ—C7—C8—F5	179.2 (4)
C2—C3—C4—F3	−177.8 (4)	Hg2—C7—C8—F5	−1.1 (5)
F2—C3—C4—C5	−178.7 (4)	C7ⁱ—C7—C8—C9	−0.4 (7)
C2—C3—C4—C5	1.5 (6)	Hg2—C7—C8—C9	179.3 (3)
F3—C4—C5—F4	−1.2 (6)	F5—C8—C9—F6	−1.2 (6)
C3—C4—C5—F4	179.5 (4)	C7—C8—C9—F6	178.4 (4)
F3—C4—C5—C6	178.8 (4)	F5—C8—C9—C9ⁱ	179.5 (5)
C3—C4—C5—C6	−0.5 (6)	C7—C8—C9—C9ⁱ	−0.8 (8)

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

Acknowledgements

Funding from the US National Science Foundation (PREM DMR-0934212 and EPSCoR IIA-1301346) is gratefully acknowledged.

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