5,5′-Bis[(2,2,2-trifluoro­eth­oxy)meth­yl]-2,2′-bipyridine

Lu, N.; Tu, W.-H.; Chang, W.-H.; Wu, Z.-W.; Su, H.-C.

doi:10.1107/S1600536811000730

organic compounds

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ISSN: 2056-9890

Volume 67| Part 2| February 2011| Pages o355-o356

doi:10.1107/S1600536811000730

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5,5′-Bis[(2,2,2-trifluoroethoxy)methyl]-2,2′-bipyridine

Norman Lu,^a ^* Wen-Han Tu,^a Wei-Hsuan Chang,^a Zong-Wei Wu ^a and Han-Chang Su ^a

^aInstitute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan
^*Correspondence e-mail: normanlu@ntut.edu.tw

(Received 6 November 2010; accepted 6 January 2011; online 12 January 2011)

The complete molecule of the title compound, C₁₆H₁₄F₆N₂O₂, is generated by crystallographic inversion symmetry, which results in two short intramolecular C—H⋯N hydrogen-bond contacts per molecule. In the crystal, aromatic π–π stacking [centroid–centroid distance = 3.457 (2) Å] and weak C—H⋯π interactions occur. A short H⋯H [2.32 (3) Å] contact is present.

Related literature

For related structures and background to the anti-planar geometry of bpy, see: Lu, Tu, Wu et al. (2010 ); Iyer et al. (2005 ); Heirtzler et al. (2002 ); Maury et al. (2001 ); Vogtle et al. (1990 ). For background to the bipyridine (bpy) ligand, see: Bain et al. (1989 ); Chambron & Sauvage (1986 , 1987 ); Grätzel (2001 ); Haga et al. (2000 ); Lu, Tu, Hou et al. (2010 ); Lu, Tu, Wen et al. (2010 ); Lu et al. (2007 ). For C—H⋯H—C interactions, see: Wolstenholme & Cameron (2006 ).

Experimental

Crystal data

C₁₆H₁₄F₆N₂O₂
M_r = 380.29
Triclinic, $[P \overline 1]$
a = 4.6573 (2) Å
b = 5.6842 (3) Å
c = 15.7273 (8) Å
α = 94.298 (3)°
β = 98.473 (3)°
γ = 105.689 (4)°
V = 393.57 (3) Å³
Z = 1
Mo Kα radiation
μ = 0.15 mm⁻¹
T = 100 K
0.2 × 0.14 × 0.12 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.664, T_max = 0.746
6627 measured reflections
1577 independent reflections
1348 reflections with I > 2σ(I)
R_int = 0.024

Refinement

R[F² > 2σ(F²)] = 0.031
wR(F²) = 0.104
S = 1.12
1577 reflections
146 parameters
All H-atom parameters refined
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

Cg is the centroid of the N,C1–C5 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯Nⁱ	0.925 (17)	2.464 (18)	2.809 (2)	102.3 (12)
C6—H6A⋯Cgⁱⁱ	0.990 (19)	2.59	3.5089 (16)	155
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) x+1, y, z.

Data collection: APEX2 (Bruker, 2010 ); cell refinement: SAINT (Bruker, 2009 ); data reduction: SAINT; 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/S1600536811000730/fk2030sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811000730/fk2030Isup2.hkl

checkCIF report

Comment top

Bipyridine (bpy) ligand is among the most versatile ligands in organometallics. It has been extensively used to prepare various chelating compounds with different metal ions (Haga et al., 2000; Bain et al., 1989; Grätzel, 2001; Chambron & Sauvage, 1987, 1986). Structures with the motif {[4,4'-bis(R_fCH₂OCH₂) -2,2'-bpy]MCl₂, M = Pd or Pt} are interesting and reveal the blue shifting C–H···F–C hydrogen bonding (Lu, Tu, Hou et al., 2010; Lu, Tu, Wen et al., 2010; Lu, et al., 2007). However, the X-ray crystal structure of poly-fluorinated bpy ligands still remains elusive until recent elucidation of the structure on simplest 4,4'-bis(CF₃CH₂OCH₂)-2,2'-bpy (Lu, Tu, Wu et al., 2010). Reported here is the significantly different crystal structure on its 5,5'-isomer. They vary only on the positions of two identical substituents, yet features of packing in the solid state show little in similarity.

The title compound I is centro-symmetric and crystallizes in the space group of P-1, one half of the molecule being crystallographically independent. Two structural features of the title compound I are the planarity and the anti conformation of connected pyridyl units. The bpy exhibits a planar core and the N–C3–C3ⁱ–Nⁱ torsion angle is 180°, similar to the values in its 4,4'-isomer (Lu, Tu, Wu et al., 2010). Also noticed is the intramolecular weak hydrogen bonding interaction on C4–H4···Nⁱ, as suggested by the short H4···Nⁱ distance of 2.46 (2) Å and the C4–H4···Nⁱ angle of 102 (1)° (see Fig. 1).

Although both the title compound and its 4,4'-isomer (Lu, Tu, Wu et al., 2010) have the same molecular formula and their bpy cores are similarly planar, their identical side chains, positioned differently, show very different intermolecular interactions and packing methods. The intramolecular C–H···O and intermolecular C–H···N and C–H···F interactions, which were observed in 4,4'-bis(2,2,2-trifluoroethoxymethyl)-2,2'-bipyridine (Lu, Tu, Wu et al., 2010), are missing in I. There is almost no intramolecular C–H···O interaction in I, judged from the C5–C1–C6–O torsion angle of 41.5 (2)°, which deviates significantly from that reported for such a hydrogen-bonding system. In its 4,4'-isomer, the corresponding H3···O8 distance is 2.52 (1) Å and the C3–C4–C7–O8 torsion angle measures -21.9 (1)°.

Instead of intermolecular C–H···N and C–H···F interactions, stabilization of the structure of I is likely due to effective intermolecular C–H..π and F···F interactions. The π-π stacking is the driving force towards crystallization, with two adjacent bpy layers at a distance of 3.512 (2) Å. On top of this, the C6–H6A..π hydrogen bonding interaction has been observed between the methylene H atom and one of the adjacent bpy rings on the a-translation related direction. As shown in Table 1, the distance of H6A to bpy plane is 2.57 (2) Å, making less than 10° with the vector of H6A to centroid of the bpy ring. The terminal CF₃ groups shown in Fig. 2 are then fixed in crystalline state by the F···F interaction between two adjacent stacking layers. The F1···F3' distance is 2.857 (2) Å, the C8–F1···F3' angle 101.4 (1)°, and the C8–F3···F1" angle 166.0 (1)°.

In particular, the weak C4–H4···H4'–C4' (Wolstenholme et al., 2006) interaction shown in Fig. 2 has also been identified with H4···H4' distance of 2.32 (3) Å and the C4–H4···H4' angle of 113 (2)°. The C4–H4···H4'–C4' interaction connects two neighboring π stacking piles. Inside one π stacking pile, the π..π stacking distance between consecutive layers is 3.512 (2) Å, whereas the shifting step between two neighboring π stacking piles is 1.448 (2) Å. It is believed that this rare C–H···H–C supramolecular interaction seems to be derived from the dipole-induced interactions, defined by Wolstenholme, on the symmetry-related hydrogen atoms.

Related literature top

For related structures and background [to what?], see: Lu, Tu, Wu et al. (2010); Iyer et al. (2005); Heirtzler et al. (2002); Maury et al. (2001); Vogtle et al. (1990). For background to the bipyridine (bpy) ligand, see: Bain et al. (1989); Chambron & Sauvage (1986, 1987); Grätzel (2001); Haga et al. (2000); Lu, Tu, Hou et al. (2010); Lu, Tu, Wen et al. (2010); Lu et al. (2007). For C—H···H—C interactions, see: Wolstenholme & Cameron (2006).

Experimental top

5,5'-bis(CF₃CH₂OCH₂)-2,2'-bpy, (I), was prepared according to the general procedure described in Lu et al., (2007). The crude product was further purified by vacuum sublimation or chromatography to obtain the title compound as a colorless solid. Full characterization data are listed below.

Analytical data of (I): Yield 76 %, m.p. = 393 K. ¹H NMR (500 MHz, d-DMSO, room temperature), δ(ppm) Pyridine ring H: 8.66 s, H6, 2H), 8.39 (d, H4, ³J_HH=8.24 Hz, 2H), 7.92 (d, H3, ³J_HH=8.24 Hz, 2H), 4.77 (s, bpy-CH₂, 4H), 4.17 (q, -OCH₂CF₃, ³J_HF=9.34 Hz, 4H); ¹⁹F NMR (470.5 MHz, d-DMSO, room temperature), δ (ppm) -73.1 (t, -CH₂CF₃, ³J_HF = 9.7 Hz, 6F); ¹³C NMR (126 MHz,d-DMSO, room temperature) δ (ppm) 120.3, 133.1, 136.9, 148.7, 154.7 (s, bpy, 10C), 121.1-127.8 (q, -CF₃, ¹J_CF = 279.6 Hz, 2C), 70.6 (s, bpy-CH₂, 2C), 66.8 (q, -CH₂CF₃, ²J_CF = 33.2 Hz, 2C).

GC/MS (M/e) : M⁺ = 380, (M-C₂H₃F₃O)⁺ = 281, [M-(C₂H₃F₃O)₂]⁺= 182, (C₆H₅N)⁺ = 91.

FT-IR (cm^-1): 1601.5, 1553.8, 1469.4, 1360.1 (bpy-ring, m), 1155.8, 1122.6 (CF₂ stretch, s).

Recrystallization proceeded with dissolution of I in DMSO to form a saturated solution, to which the water overlayer (5 cm³) was added. Solvent diffusion over a period of ten days at 298 K afforded needle shaped crystals.

Computing details top

Data collection: APEX2 (Bruker, 2010); 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 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. Molecular structure of I with displacement ellipsoids at the 50% probability level. [Symmetry code: (i) 1-x, 1-y, 1-z.]
	Fig. 2. The rare C4–H4···H4'–C4' interaction on inversion related molecules; the H4···H4' distance and C4–H4···H4' angle are 2.32 (3) Å and 113 (2) °. [Symmetry code: (ii) 2-x, 1-y, 1-z.]

5,5'-Bis[(2,2,2-trifluoroethoxy)methyl]-2,2'-bipyridine top

Crystal data top

C₁₆H₁₄F₆N₂O₂	Z = 1
M_r = 380.29	F(000) = 194
Triclinic, P1	D_x = 1.605 Mg m⁻³ D_m = 1.53 Mg m⁻³ D_m measured by w/v
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 4.6573 (2) Å	Cell parameters from 3201 reflections
b = 5.6842 (3) Å	θ = 2.6–27.1°
c = 15.7273 (8) Å	µ = 0.15 mm⁻¹
α = 94.298 (3)°	T = 100 K
β = 98.473 (3)°	Prism, colourless
γ = 105.689 (4)°	0.2 × 0.14 × 0.12 mm
V = 393.57 (3) Å³

Data collection top

Bruker APEXII CCD area-detector diffractometer	1348 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.024
ϕ and ω scans	θ_max = 26.4°, θ_min = 1.3°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −5→5
T_min = 0.664, T_max = 0.746	k = −7→7
6627 measured reflections	l = −19→19
1577 independent 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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.104	All H-atom parameters refined
S = 1.12	w = 1/[σ²(F_o²) + (0.0595P)² + 0.094P] where P = (F_o² + 2F_c²)/3
1577 reflections	(Δ/σ)_max < 0.001
146 parameters	Δρ_max = 0.29 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₁₆H₁₄F₆N₂O₂	γ = 105.689 (4)°
M_r = 380.29	V = 393.57 (3) Å³
Triclinic, P1	Z = 1
a = 4.6573 (2) Å	Mo Kα radiation
b = 5.6842 (3) Å	µ = 0.15 mm⁻¹
c = 15.7273 (8) Å	T = 100 K
α = 94.298 (3)°	0.2 × 0.14 × 0.12 mm
β = 98.473 (3)°

Data collection top

Bruker APEXII CCD area-detector diffractometer	1577 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	1348 reflections with I > 2σ(I)
T_min = 0.664, T_max = 0.746	R_int = 0.024
6627 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.031	0 restraints
wR(F²) = 0.104	All H-atom parameters refined
S = 1.12	Δρ_max = 0.29 e Å⁻³
1577 reflections	Δρ_min = −0.27 e Å⁻³
146 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
F1	1.8989 (2)	1.22574 (16)	0.98212 (6)	0.0271 (3)
F2	1.8270 (2)	1.35589 (16)	0.85765 (6)	0.0299 (3)
F3	1.4537 (2)	1.23169 (17)	0.92410 (6)	0.0294 (3)
O	1.4170 (2)	0.88799 (19)	0.79273 (7)	0.0225 (3)
N	0.6609 (3)	0.3432 (2)	0.58189 (8)	0.0173 (3)
C1	1.1096 (3)	0.6201 (3)	0.67039 (9)	0.0160 (3)
C2	0.8935 (3)	0.3918 (3)	0.64727 (10)	0.0174 (3)
C3	0.6289 (3)	0.5286 (2)	0.53652 (8)	0.0144 (3)
C4	0.8268 (3)	0.7658 (3)	0.55708 (10)	0.0181 (3)
C5	1.0718 (3)	0.8098 (3)	0.62300 (10)	0.0189 (3)
C6	1.3693 (3)	0.6554 (3)	0.74291 (10)	0.0187 (3)
C7	1.6509 (4)	0.9271 (3)	0.86434 (10)	0.0214 (4)
C8	1.7066 (3)	1.1854 (3)	0.90685 (10)	0.0204 (3)
H2	0.903 (4)	0.259 (4)	0.6804 (12)	0.025 (5)*
H4	0.789 (4)	0.887 (3)	0.5248 (11)	0.023 (4)*
H5	1.215 (4)	0.970 (4)	0.6343 (12)	0.029 (5)*
H6A	1.556 (4)	0.658 (3)	0.7197 (11)	0.021 (4)*
H6B	1.327 (4)	0.527 (3)	0.7796 (12)	0.024 (4)*
H7A	1.594 (4)	0.813 (4)	0.9065 (12)	0.026 (5)*
H7B	1.843 (4)	0.916 (3)	0.8461 (12)	0.028 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
F1	0.0318 (5)	0.0225 (5)	0.0219 (5)	0.0071 (4)	−0.0072 (4)	−0.0029 (4)
F2	0.0381 (6)	0.0217 (5)	0.0283 (5)	0.0050 (4)	0.0051 (4)	0.0072 (4)
F3	0.0266 (5)	0.0305 (5)	0.0318 (5)	0.0125 (4)	0.0036 (4)	−0.0048 (4)
O	0.0264 (6)	0.0187 (5)	0.0205 (6)	0.0106 (4)	−0.0067 (5)	−0.0044 (4)
N	0.0208 (6)	0.0119 (6)	0.0188 (6)	0.0044 (5)	0.0024 (5)	0.0025 (5)
C1	0.0161 (7)	0.0164 (7)	0.0168 (7)	0.0063 (6)	0.0046 (6)	−0.0002 (6)
C2	0.0223 (8)	0.0126 (7)	0.0182 (7)	0.0065 (6)	0.0031 (6)	0.0027 (5)
C3	0.0162 (7)	0.0125 (7)	0.0156 (7)	0.0044 (5)	0.0054 (6)	0.0023 (5)
C4	0.0208 (7)	0.0133 (7)	0.0198 (7)	0.0035 (6)	0.0026 (6)	0.0055 (6)
C5	0.0187 (7)	0.0139 (7)	0.0217 (8)	0.0006 (6)	0.0028 (6)	0.0022 (6)
C6	0.0192 (7)	0.0156 (7)	0.0210 (8)	0.0061 (6)	0.0015 (6)	−0.0002 (6)
C7	0.0236 (8)	0.0205 (8)	0.0188 (8)	0.0084 (6)	−0.0033 (7)	0.0004 (6)
C8	0.0212 (8)	0.0209 (8)	0.0183 (7)	0.0074 (6)	−0.0008 (6)	0.0015 (6)

Geometric parameters (Å, º) top

F1—C8	1.3386 (17)	C3—C4	1.396 (2)
F2—C8	1.3411 (18)	C3—C3ⁱ	1.481 (3)
F3—C8	1.3347 (18)	C4—C5	1.377 (2)
O—C7	1.4053 (18)	C4—H4	0.926 (19)
O—C6	1.4304 (17)	C5—H5	0.96 (2)
N—C2	1.3322 (19)	C6—H6A	0.990 (19)
N—C3	1.3446 (18)	C6—H6B	0.960 (19)
C1—C5	1.390 (2)	C7—C8	1.505 (2)
C1—C2	1.394 (2)	C7—H7A	0.98 (2)
C1—C6	1.494 (2)	C7—H7B	1.00 (2)
C2—H2	0.96 (2)

C7—O—C6	111.24 (11)	O—C6—H6A	108.1 (10)
C2—N—C3	117.65 (12)	C1—C6—H6A	110.2 (10)
C5—C1—C2	117.07 (14)	O—C6—H6B	109.2 (11)
C5—C1—C6	122.24 (13)	C1—C6—H6B	110.7 (11)
C2—C1—C6	120.69 (13)	H6A—C6—H6B	109.9 (14)
N—C2—C1	124.41 (13)	O—C7—C8	107.27 (12)
N—C2—H2	115.6 (11)	O—C7—H7A	111.5 (11)
C1—C2—H2	119.9 (11)	C8—C7—H7A	108.4 (11)
N—C3—C4	122.04 (13)	O—C7—H7B	111.4 (10)
N—C3—C3ⁱ	117.10 (15)	C8—C7—H7B	107.4 (11)
C4—C3—C3ⁱ	120.85 (15)	H7A—C7—H7B	110.6 (16)
C5—C4—C3	119.25 (13)	F3—C8—F1	107.01 (12)
C5—C4—H4	122.6 (11)	F3—C8—F2	106.48 (12)
C3—C4—H4	118.2 (11)	F1—C8—F2	107.15 (12)
C4—C5—C1	119.49 (14)	F3—C8—C7	112.67 (13)
C4—C5—H5	119.0 (11)	F1—C8—C7	110.74 (12)
C1—C5—H5	121.5 (11)	F2—C8—C7	112.46 (13)
O—C6—C1	108.60 (11)

C3—N—C2—C1	−1.6 (2)	C6—C1—C5—C4	−179.74 (13)
C5—C1—C2—N	1.9 (2)	C7—O—C6—C1	177.45 (12)
C6—C1—C2—N	−177.87 (13)	C5—C1—C6—O	41.49 (19)
C2—N—C3—C4	−1.1 (2)	C2—C1—C6—O	−138.72 (14)
C2—N—C3—C3ⁱ	179.43 (14)	C6—O—C7—C8	174.02 (13)
N—C3—C4—C5	3.4 (2)	O—C7—C8—F3	52.09 (17)
C3ⁱ—C3—C4—C5	−177.17 (15)	O—C7—C8—F1	171.89 (12)
C3—C4—C5—C1	−3.0 (2)	O—C7—C8—F2	−68.27 (17)
C2—C1—C5—C4	0.5 (2)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the N,C1–C5 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···Nⁱ	0.925 (17)	2.464 (18)	2.809 (2)	102.3 (12)
C6—H6A···Cgⁱⁱ	0.990 (19)	2.59	3.5089 (16)	155

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

Experimental details

Crystal data
Chemical formula	C₁₆H₁₄F₆N₂O₂
M_r	380.29
Crystal system, space group	Triclinic, P1
Temperature (K)	100
a, b, c (Å)	4.6573 (2), 5.6842 (3), 15.7273 (8)
α, β, γ (°)	94.298 (3), 98.473 (3), 105.689 (4)
V (Å³)	393.57 (3)
Z	1
Radiation type	Mo Kα
µ (mm⁻¹)	0.15
Crystal size (mm)	0.2 × 0.14 × 0.12

Data collection
Diffractometer	Bruker APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2008)
T_min, T_max	0.664, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	6627, 1577, 1348
R_int	0.024
(sin θ/λ)_max (Å⁻¹)	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.031, 0.104, 1.12
No. of reflections	1577
No. of parameters	146
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.27

Computer programs: APEX2 (Bruker, 2010), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the N,C1–C5 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···Nⁱ	0.925 (17)	2.464 (18)	2.809 (2)	102.3 (12)
C6—H6A···Cgⁱⁱ	0.990 (19)	2.59	3.5089 (16)	155

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

C—H···π contact for (I); hpd = H-atom-to-ring-plane distance, hcd = H-atom-to-ring-center distance, and sa = slippage angle (angle subtended by the hcd vector to the plane normal). top

	hpd(Å)	hcd(Å)	sa(°)
C6-H6A···πⁱⁱⁱ	2.57 (2)	2.59 (2)	6.4 (2)

Symmetry code: (iii) x-1, y, z.

Acknowledgements

NL thanks the Taiwan NSC for financial support (NSC 98-2113-M- 027-002-MY3). We also thank Mr T. S. Kuo (Department of Chemistry, National Taiwan Normal University, Taiwan) for the assistance with the structure analysis.

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Volume 67| Part 2| February 2011| Pages o355-o356

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