4-(4,4-Difluoro-1,3,5,7-tetra­methyl-3a-aza-4a-azonia-4-borata-s-indacen-8-yl)benzonitrile

Chen, Y.; Jiang, J.

doi:10.1107/S1600536811009457

organic compounds

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ISSN: 2056-9890

Volume 67| Part 4| April 2011| Page o908

doi:10.1107/S1600536811009457

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4-(4,4-Difluoro-1,3,5,7-tetramethyl-3a-aza-4a-azonia-4-borata-s-indacen-8-yl)benzonitrile

Yuting Chen ^a,^b and Jianzhuang Jiang ^a ^*

^aDepartment of Chemistry, Shandong University, Jinan 250100, People's Republic of China, and ^bDepartment of Chemistry, Dezhou University, Dezhou 253023, People's Republic of China
^*Correspondence e-mail: jianzhuang@ustb.edu.cn

(Received 23 February 2011; accepted 12 March 2011; online 19 March 2011)

The title compound, C₂₀H₁₈BF₂N₃, contains one C₉BN₂ (Bodipy) framework and one cyanobenzyl group. The Bodipy framework is essentially planar with a maximum deviation of 0.041 (2) Å. The introduction of two methyl groups at positions 1 and 7 of s-indacene in the Bodipy unit results in almost orthogonal configuration between the mean plane of the Bodipy unit and the cyanobenzyl group [dihedral angle = 89.78 (4)°].

Related literature

For the structures and optical properties of Bodipy dyes, see: Loudet & Burgess (2007 ) and Feng et al. (2008 ), respectively. For the relation between the crystal structures and optical properties of Bodipy compounds, see: Cui et al. (2007 ); Broring et al.(2008 ).

Experimental

Crystal data

C₂₀H₁₈BF₂N₃
M_r = 349.18
Monoclinic, P 2₁ /c
a = 7.6498 (3) Å
b = 11.3715 (5) Å
c = 21.555 (1) Å
β = 92.008 (4)°
V = 1873.91 (14) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 293 K
0.20 × 0.18 × 0.16 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.983, T_max = 0.986
7304 measured reflections
3286 independent reflections
2240 reflections with I > 2σ(I)
R_int = 0.028

Refinement

R[F² > 2σ(F²)] = 0.065
wR(F²) = 0.195
S = 1.07
3286 reflections
235 parameters
H-atom parameters constrained
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Table 1
Selected bond lengths (Å)

F2—B1	1.382 (4)
N1—C5	1.350 (3)
N1—C9	1.400 (3)
N1—B1	1.535 (4)
F1—B1	1.384 (3)
N2—C3	1.346 (3)
N2—C10	1.408 (3)
N2—B1	1.545 (4)
C8—C10	1.390 (3)
C8—C9	1.398 (3)
C10—C1	1.429 (4)
C9—C7	1.426 (4)

Data collection: SMART (Bruker, 1996 ); cell refinement: SAINT (Bruker, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811009457/aa2003sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811009457/aa2003Isup2.hkl

checkCIF report

Comment top

Fluorescent dyes, especially 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (Bodipy), have been extensively studied due to their advantageous photospectral properties including high photostability, sharp absorption and emission bands, relatively high absorption coefficient, high fluorescence quantum yields, and the extraordinary feature of excitation/emission wavelengths in the visible region (Loudet et al., 2007; Feng et al. 2008). Single crystal structural studies of these compounds have become increasingly important in revealing precisely the relation between their optical properties and molecular structures (Cui et al., 2007). As an extension of our work on the structural characterization of this field, the title compound, (I), is synthesized and characterized by x-ray diffraction, as shown in Fig. 1.

The compound (I) crystallizes in the monoclinic system with only one molecule per unit cell, and contains mainly one C₉BN₂ (Bodipy) framework and one cyanobenzyl unit. The C₉BN₂ (Bodipy) framework consisting of one central six-membered and two adjacent five-membered rings is essentially flat, with the maximum deviation from the least-squares mean plane being 0.041 Å. As shown in Table 1, the C—C and C—N bond lengths within C₉BN₂ (Bodipy) framework, without any clear distinction between single and double bonds, indicate the strongly delocalized π-system nature of the Bodipy framework. However, this π-electron delocalization is interrupted between the two B—N bonds (Broring et al. 2008). More interestingly, the introduction of two methyl groups onto C-1 and C-7 atoms in Bodipy moiety results in almostly orthogonal configuration between the mean plane of Bodipy moiety and cyanobenzyl unit with the dihedral angle of 89.78 (4)°, indicating the almost non-electronic coupling nature between these moieties. (Loudet et al., 2007).

Related literature top

For the structures and optical properties of Bodipy dyes, see: Loudet et al. (2007) and Feng et al. (2008), respectively. For the relation between the crystal structures and optical properties of Bodipy compounds, see: Cui et al. (2007); Broring et al.(2008).

Experimental top

To the mixture of 4-cyanobenzaldehyde (131 mg, 1 mmol) and 2,4-dimethylpyrrole (190 mg, 2.00 mmol) dissolved in CH₂Cl₂ (100 ml), one drop of TFAwas added. The resulting mixture was then stirred at room temperature under N₂ atmosphere. When thin-layer chromatography (TLC) monitoring indicated the complete consumption of the aldehyde, a solution of DDQ (227 mg, 1 mmol) in CH₂Cl₂ (40 ml) was added and the reaction mixture was further stirred for another 15 min. After the addition of N, N-diisopropylethylamine (DIEA) (2 ml) into the mixture for 15 min, the BF₃—OEt₂ (2.0 ml) was added into the reaction mixture and stirring was continued for another 30 min. The resulting mixture was evaporated, and the residue was chromatographed on a silica gel column using CH₂Cl₂/hexane (1:1) as eluent. Repeated chromatography followed by recrystallization from CH₂Cl₂ and hexane gave the target compound as black-red crystals. Yield: 104 mg, 15%. Anal. for C₂₀H₁₈BF₂N₃: Calc. C, 68.79; H, 5.20; N, 12.03; Found: C, 68.10; H, 5.17; N, 12.81%. The No. of CCDC: 814146.

Computing details top

Data collection: SMART (Bruker, 1996); cell refinement: SAINT (Bruker, 1996); data reduction: SAINT (Bruker, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at 30% probability level.

4-(4,4-Difluoro-1,3,5,7-tetramethyl-3a-aza-4a-azonia-4-borata-s- indacen-8-yl)benzonitrile top

Crystal data top

C₂₀H₁₈BF₂N₃	F(000) = 728
M_r = 349.18	D_x = 1.238 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3286 reflections
a = 7.6498 (3) Å	θ = 2.3–25.0°
b = 11.3715 (5) Å	µ = 0.09 mm⁻¹
c = 21.555 (1) Å	T = 293 K
β = 92.008 (4)°	Block, red
V = 1873.91 (14) Å³	0.20 × 0.18 × 0.16 mm
Z = 4

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	3286 independent reflections
Radiation source: fine-focus sealed tube	2240 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.028
ϕ and ω scans	θ_max = 25.0°, θ_min = 3.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→8
T_min = 0.983, T_max = 0.986	k = −13→13
7304 measured reflections	l = −25→16

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)] = 0.065	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.195	H-atom parameters constrained
S = 1.07	w = 1/[σ²(F_o²) + (0.1059P)² + 0.276P] where P = (F_o² + 2F_c²)/3
3286 reflections	(Δ/σ)_max < 0.001
235 parameters	Δρ_max = 0.30 e Å⁻³
0 restraints	Δρ_min = −0.25 e Å⁻³

Crystal data top

C₂₀H₁₈BF₂N₃	V = 1873.91 (14) Å³
M_r = 349.18	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 7.6498 (3) Å	µ = 0.09 mm⁻¹
b = 11.3715 (5) Å	T = 293 K
c = 21.555 (1) Å	0.20 × 0.18 × 0.16 mm
β = 92.008 (4)°

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	3286 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	2240 reflections with I > 2σ(I)
T_min = 0.983, T_max = 0.986	R_int = 0.028
7304 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.065	0 restraints
wR(F²) = 0.195	H-atom parameters constrained
S = 1.07	Δρ_max = 0.30 e Å⁻³
3286 reflections	Δρ_min = −0.25 e Å⁻³
235 parameters

Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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
F2	0.6736 (2)	1.18071 (15)	0.82647 (9)	0.0706 (6)
N1	0.7514 (3)	0.97876 (19)	0.81048 (9)	0.0409 (6)
F1	0.8040 (3)	1.13260 (16)	0.73783 (8)	0.0750 (6)
N2	0.9776 (3)	1.13074 (18)	0.83306 (9)	0.0384 (5)
C17	1.2845 (4)	0.6972 (2)	0.99641 (13)	0.0491 (7)
C8	1.0075 (3)	0.9342 (2)	0.87582 (11)	0.0376 (6)
C14	1.1043 (3)	0.8502 (2)	0.91690 (12)	0.0391 (6)
C10	1.0737 (3)	1.0468 (2)	0.86812 (11)	0.0388 (6)
C9	0.8499 (3)	0.8989 (2)	0.84668 (11)	0.0405 (6)
C20	1.3795 (5)	0.6205 (3)	1.03874 (14)	0.0619 (9)
C18	1.1552 (4)	0.7687 (3)	1.01831 (13)	0.0623 (9)
H18	1.1293	0.7667	1.0601	0.075*
C16	1.3223 (4)	0.7006 (3)	0.93441 (14)	0.0593 (8)
H16	1.4078	0.6513	0.9191	0.071*
C15	1.2329 (4)	0.7774 (3)	0.89494 (13)	0.0555 (8)
H15	1.2595	0.7801	0.8532	0.067*
C2	1.2232 (4)	1.2167 (3)	0.86865 (14)	0.0548 (8)
H2	1.3084	1.2739	0.8758	0.066*
C5	0.6123 (3)	0.9205 (3)	0.78539 (13)	0.0495 (7)
C19	1.0646 (4)	0.8426 (3)	0.97863 (13)	0.0579 (8)
H19	0.9748	0.8885	0.9936	0.069*
C4	0.9998 (4)	1.3421 (3)	0.80490 (16)	0.0627 (9)
H4A	0.8893	1.3266	0.7840	0.094*
H4B	1.0814	1.3701	0.7754	0.094*
H4C	0.9849	1.4008	0.8363	0.094*
C1	1.2306 (3)	1.1032 (3)	0.89043 (13)	0.0484 (7)
C7	0.7648 (4)	0.7874 (2)	0.84295 (14)	0.0510 (7)
C6	0.6190 (4)	0.8041 (3)	0.80502 (15)	0.0588 (8)
H3	0.5373	0.7465	0.7942	0.071*
C3	1.0675 (4)	1.2325 (2)	0.83408 (12)	0.0461 (7)
B1	0.7971 (4)	1.1087 (3)	0.80066 (14)	0.0441 (8)
C11	0.8200 (5)	0.6725 (3)	0.87155 (19)	0.0788 (11)
H5A	0.9251	0.6836	0.8965	0.118*
H5B	0.8411	0.6164	0.8393	0.118*
H5C	0.7290	0.6438	0.8971	0.118*
C13	1.3786 (4)	1.0532 (3)	0.92990 (17)	0.0722 (10)
H13A	1.3544	0.9724	0.9392	0.108*
H13B	1.3907	1.0971	0.9679	0.108*
H13C	1.4852	1.0582	0.9078	0.108*
C12	0.4752 (4)	0.9784 (3)	0.74490 (17)	0.0751 (10)
H1A	0.5045	1.0598	0.7395	0.113*
H1B	0.3640	0.9725	0.7640	0.113*
H1C	0.4690	0.9402	0.7052	0.113*
N3	1.4528 (4)	0.5619 (3)	1.07363 (14)	0.0836 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
F2	0.0473 (9)	0.0506 (10)	0.1138 (16)	0.0101 (8)	0.0003 (10)	−0.0057 (10)
N1	0.0394 (11)	0.0438 (13)	0.0393 (12)	−0.0006 (10)	−0.0026 (9)	0.0010 (10)
F1	0.0938 (14)	0.0822 (13)	0.0473 (11)	−0.0220 (11)	−0.0203 (9)	0.0224 (9)
N2	0.0407 (11)	0.0357 (12)	0.0388 (12)	0.0002 (9)	0.0007 (9)	0.0048 (10)
C17	0.0574 (17)	0.0432 (16)	0.0460 (17)	0.0028 (13)	−0.0073 (13)	0.0088 (13)
C8	0.0411 (13)	0.0378 (15)	0.0342 (13)	0.0026 (11)	0.0065 (11)	−0.0002 (11)
C14	0.0407 (13)	0.0374 (14)	0.0390 (15)	0.0019 (11)	−0.0008 (11)	0.0004 (12)
C10	0.0366 (12)	0.0439 (15)	0.0358 (14)	0.0035 (11)	0.0004 (10)	0.0011 (12)
C9	0.0402 (13)	0.0401 (15)	0.0412 (14)	0.0019 (11)	0.0003 (11)	0.0005 (12)
C20	0.084 (2)	0.0478 (18)	0.0534 (19)	0.0053 (17)	−0.0091 (17)	0.0070 (16)
C18	0.093 (2)	0.0577 (19)	0.0371 (16)	0.0218 (18)	0.0102 (16)	0.0069 (15)
C16	0.0633 (18)	0.064 (2)	0.0510 (18)	0.0255 (16)	0.0034 (14)	0.0056 (15)
C15	0.0631 (18)	0.065 (2)	0.0383 (15)	0.0189 (16)	0.0066 (13)	0.0074 (14)
C2	0.0499 (16)	0.0527 (19)	0.0617 (19)	−0.0188 (14)	−0.0007 (14)	0.0050 (15)
C5	0.0418 (14)	0.0539 (18)	0.0522 (16)	−0.0050 (13)	−0.0060 (13)	−0.0024 (14)
C19	0.078 (2)	0.0560 (19)	0.0410 (16)	0.0208 (16)	0.0178 (15)	0.0044 (14)
C4	0.068 (2)	0.0479 (18)	0.072 (2)	−0.0081 (16)	0.0016 (17)	0.0148 (16)
C1	0.0425 (14)	0.0533 (18)	0.0489 (16)	−0.0033 (13)	−0.0048 (12)	0.0027 (14)
C7	0.0492 (15)	0.0412 (16)	0.0626 (19)	−0.0040 (13)	−0.0011 (14)	−0.0014 (14)
C6	0.0496 (16)	0.0511 (19)	0.075 (2)	−0.0158 (14)	−0.0031 (15)	−0.0054 (16)
C3	0.0501 (15)	0.0439 (16)	0.0444 (16)	−0.0074 (13)	0.0052 (12)	0.0043 (13)
B1	0.0478 (17)	0.0419 (18)	0.0421 (17)	0.0003 (14)	−0.0056 (14)	0.0069 (15)
C11	0.079 (2)	0.0441 (19)	0.112 (3)	−0.0110 (17)	−0.013 (2)	0.0184 (19)
C13	0.0506 (17)	0.078 (2)	0.086 (2)	−0.0111 (16)	−0.0224 (17)	0.0132 (19)
C12	0.0591 (19)	0.077 (2)	0.086 (2)	−0.0084 (18)	−0.0288 (18)	0.0025 (19)
N3	0.111 (2)	0.0673 (19)	0.0713 (19)	0.0198 (18)	−0.0186 (17)	0.0168 (16)

Geometric parameters (Å, º) top

F2—B1	1.382 (4)	C2—C1	1.374 (4)
N1—C5	1.350 (3)	C2—C3	1.394 (4)
N1—C9	1.400 (3)	C2—H2	0.9300
N1—B1	1.535 (4)	C5—C6	1.390 (4)
F1—B1	1.384 (3)	C5—C12	1.494 (4)
N2—C3	1.346 (3)	C19—H19	0.9300
N2—C10	1.408 (3)	C4—C3	1.482 (4)
N2—B1	1.545 (4)	C4—H4A	0.9600
C17—C18	1.376 (4)	C4—H4B	0.9600
C17—C16	1.378 (4)	C4—H4C	0.9600
C17—C20	1.440 (4)	C1—C13	1.504 (4)
C8—C10	1.390 (3)	C7—C6	1.373 (4)
C8—C9	1.398 (3)	C7—C11	1.500 (4)
C8—C14	1.483 (3)	C6—H3	0.9300
C14—C19	1.378 (4)	C11—H5A	0.9600
C14—C15	1.382 (4)	C11—H5B	0.9600
C10—C1	1.429 (4)	C11—H5C	0.9600
C9—C7	1.426 (4)	C13—H13A	0.9600
C20—N3	1.138 (4)	C13—H13B	0.9600
C18—C19	1.371 (4)	C13—H13C	0.9600
C18—H18	0.9300	C12—H1A	0.9600
C16—C15	1.384 (4)	C12—H1B	0.9600
C16—H16	0.9300	C12—H1C	0.9600
C15—H15	0.9300

C5—N1—C9	107.8 (2)	C3—C4—H4B	109.5
C5—N1—B1	126.7 (2)	H4A—C4—H4B	109.5
C9—N1—B1	125.5 (2)	C3—C4—H4C	109.5
C3—N2—C10	108.5 (2)	H4A—C4—H4C	109.5
C3—N2—B1	126.5 (2)	H4B—C4—H4C	109.5
C10—N2—B1	125.0 (2)	C2—C1—C10	106.4 (2)
C18—C17—C16	119.6 (2)	C2—C1—C13	124.7 (3)
C18—C17—C20	119.5 (3)	C10—C1—C13	128.8 (3)
C16—C17—C20	120.9 (3)	C6—C7—C9	105.7 (2)
C10—C8—C9	121.5 (2)	C6—C7—C11	125.2 (3)
C10—C8—C14	119.2 (2)	C9—C7—C11	129.1 (3)
C9—C8—C14	119.2 (2)	C7—C6—C5	109.5 (2)
C19—C14—C15	118.5 (2)	C7—C6—H3	125.3
C19—C14—C8	119.6 (2)	C5—C6—H3	125.3
C15—C14—C8	121.9 (2)	N2—C3—C2	108.9 (2)
C8—C10—N2	120.2 (2)	N2—C3—C4	123.1 (3)
C8—C10—C1	132.8 (2)	C2—C3—C4	127.9 (3)
N2—C10—C1	107.0 (2)	F2—B1—F1	109.1 (2)
C8—C9—N1	120.2 (2)	F2—B1—N1	110.6 (2)
C8—C9—C7	131.7 (2)	F1—B1—N1	109.9 (2)
N1—C9—C7	108.0 (2)	F2—B1—N2	109.5 (2)
N3—C20—C17	177.9 (4)	F1—B1—N2	110.3 (2)
C19—C18—C17	120.1 (3)	N1—B1—N2	107.3 (2)
C19—C18—H18	119.9	C7—C11—H5A	109.5
C17—C18—H18	119.9	C7—C11—H5B	109.5
C17—C16—C15	119.9 (3)	H5A—C11—H5B	109.5
C17—C16—H16	120.1	C7—C11—H5C	109.5
C15—C16—H16	120.1	H5A—C11—H5C	109.5
C14—C15—C16	120.7 (3)	H5B—C11—H5C	109.5
C14—C15—H15	119.7	C1—C13—H13A	109.5
C16—C15—H15	119.7	C1—C13—H13B	109.5
C1—C2—C3	109.1 (2)	H13A—C13—H13B	109.5
C1—C2—H2	125.4	C1—C13—H13C	109.5
C3—C2—H2	125.4	H13A—C13—H13C	109.5
N1—C5—C6	109.0 (2)	H13B—C13—H13C	109.5
N1—C5—C12	123.0 (3)	C5—C12—H1A	109.5
C6—C5—C12	128.0 (3)	C5—C12—H1B	109.5
C18—C19—C14	121.1 (3)	H1A—C12—H1B	109.5
C18—C19—H19	119.4	C5—C12—H1C	109.5
C14—C19—H19	119.4	H1A—C12—H1C	109.5
C3—C4—H4A	109.5	H1B—C12—H1C	109.5

Experimental details

Crystal data
Chemical formula	C₂₀H₁₈BF₂N₃
M_r	349.18
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	7.6498 (3), 11.3715 (5), 21.555 (1)
β (°)	92.008 (4)
V (Å³)	1873.91 (14)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.20 × 0.18 × 0.16

Data collection
Diffractometer	Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.983, 0.986
No. of measured, independent and observed [I > 2σ(I)] reflections	7304, 3286, 2240
R_int	0.028
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.065, 0.195, 1.07
No. of reflections	3286
No. of parameters	235
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.30, −0.25

Computer programs: SMART (Bruker, 1996), SAINT (Bruker, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected bond lengths (Å) top

F2—B1	1.382 (4)	N2—C10	1.408 (3)
N1—C5	1.350 (3)	N2—B1	1.545 (4)
N1—C9	1.400 (3)	C8—C10	1.390 (3)
N1—B1	1.535 (4)	C8—C9	1.398 (3)
F1—B1	1.384 (3)	C10—C1	1.429 (4)
N2—C3	1.346 (3)	C9—C7	1.426 (4)

References

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