{2-[(3,5-Dimethyl-2H-pyrrol-2-yl­idene-κN)(4-nitro­phen­yl)meth­yl]-3,5-dimethyl-1H-pyrrol-1-ido-κN}difluoridoboron

Ai-Jun Cui; Jie An; Fu-An Sun; Meng Hu; Jing Qin

doi:10.1107/S1600536811052196

. 2011 Dec 10;68(Pt 1):o63. doi: 10.1107/S1600536811052196

{2-[(3,5-Dimethyl-2H-pyrrol-2-ylidene-κN)(4-nitrophenyl)methyl]-3,5-dimethyl-1H-pyrrol-1-ido-κN}difluoridoboron

Ai-Jun Cui ^a,^*, Jie An ^a, Fu-An Sun ^a, Meng Hu ^a, Jing Qin ^a

PMCID: PMC3254419 PMID: 22259564

Abstract

In an effort to discover novel and potential boron–dipyrromethene (BODIPY) dyes, the title compound, C₁₉H₁₈BF₂N₃O₂, was prepared from 2,4-dimethylpyrrole, 4-nitrobenzaldehyde and BF₃·Et₂O in a one-pot reaction. There are two independent molecules, A and B, in the asymmetric unit in which the dihedral angles between the benzene ring and boron–dipyrromethene mean plane have significantly different values [82.71 (8)° for molecule A and 73.16 (8)° for molecule B]. Intermolecular C—H⋯π interactions help to stabilize the crystal structure.

Related literature

For the use of related compounds in fluorescence analysis, see: Weiner et al. (2001 ▶); Gabe et al. (2004 ▶). For related structures, see: Euler et al. (2002a ▶,b ▶); Cui et al. (2006 ▶). For the synthetic procedure, see: Kollmannsberger et al. (1998 ▶).

Experimental

Crystal data

C₁₉H₁₈BF₂N₃O₂
M _r = 369.17
Monoclinic,
a = 30.5729 (6) Å
b = 11.8625 (2) Å
c = 19.8975 (5) Å
β = 96.732 (1)°
V = 7166.5 (3) Å³
Z = 16
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 295 K
0.60 × 0.31 × 0.12 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.961, T _max = 0.989
10802 measured reflections
6278 independent reflections
4790 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.083
wR(F ²) = 0.193
S = 1.26
6278 reflections
492 parameters
H-atom parameters constrained
Δρ_max = 0.27 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: APEX2 and SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811052196/im2338sup1.cif

e-68-00o63-sup1.cif^{(32.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811052196/im2338Isup2.hkl

e-68-00o63-Isup2.hkl^{(307.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg1 and Cg2 are the centroids of the N4/C26/C28/C29/C31 and N5/C21–C23/C25 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C18—H18A⋯Cg1	0.93	2.93	3.784 (4)	154
C35—H35A⋯Cg2ⁱ	0.93	2.90	3.648 (5)	139

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Symmetry code: (i) Inline graphic .

Acknowledgments

We gratefully acknowledge financial support from the Open Foundation of Jiangsu Province Key Laboratory of Fine Petrochemical Technology (KF1005) and the Analysis Center of Changzhou University.

supplementary crystallographic information

Comment

In the past few years, many novel boron-dipyrromethene (BODIPY) dyes were developed for fluorescence analysis (Weiner et al., 2001; Gabe et al., 2004) and their crystal structures were investigated at the same time (Euler et al., 2002a,b). As part of our ongoing studies of the substituent effect on the solid-state structures of BODIPY derivatives (Cui et al., 2006), we report herein the crystal strcuture of the title compound, 4,4-difluoro- 1,3,5,7-tetramethyl-8-(4'-nitrophenyl)-4-bora-3a,4a-diaza-s-indacene, (I).

The asymmetric unit of the title compound is shown in Fig. 1. There are two independent unique molecules [lablled A and B], in which the dihedral angles between the benzene ring and boron-dipyrromethene mean plane have significantly different values [82.71 (8)° for molecule A, 73.16 (8)° for molecule B]. In the crystal structure, there also exist intermolecular weak edge-to-face C—H···π [C18-H18A···Cg1ⁱ (Cg1 = N4, C26, C28, C29, C31): H18A···Cg1, 2.93 Å, C18···Cg1, 3.784 (4) Å, i = x, y, z; and C35-H35A···Cg2ⁱⁱ (Cg2 = N5, C21-C23, C25): H35A···Cg2, 2.90 Å, C35···Cg2, 3.648 (5) Å, i = -x + 3/2, y + 1/2, -z + 1/2 ] interactions, which help to reinforce the packing lattice.

Experimental

Compound (I) was prepared from 2,4-dimethylpyrrole and p-nitrobenzaldehyde in a one-pot reaction (Kollmannsberger et al., 1998). General procedure: 4.5 mmol of 2,4-dimethylpyrrole and 2 mmol of the aldehyde were dissolved in 150 ml of absolute dichloromethane under nitrogen atmosphere. One drop of trifluoroacetic acid was added and the solution was stirred at room temperature until TLC-control showed complete consumption of the aldehyde. At this point, 2 mmol dichlorodicyanobenzoquinone (DDQ) was added, and stirring was continued for 10 min followed by addition of 4 ml of triethylamine and 4 ml of boron trifluoride etherate quickly. After stirring for another 2 h, the reaction mixture was washed with water and dried, and the solvent was evaporated. The residue was chromatographed twice on a silica column (the mixture of dichloromethane and hexane as eluted solvent). Total yield: 48%. Orange crystals. ¹H NMR (CDCl₃): δ 1.36 (s, 6H, CH₃), 2.57 (s, 6H, CH₃), 6.02 (s, 2H, CH), 7.55 (d, 2H, CH, J = 21 Hz), 8.40 (d, 2H, CH, J = 22 Hz). MS (ESI), m/z: 368.2 [M—H]^-. HRMS: [M—H]^- calculated: 368.1496, measured: 368.1472.

Red single crystals suitable for X-ray analysis were obtained by dissolving (I) (0.2 g) in a hexane/dichloromethane (15 ml, v:v: 1:3) mixture and slowly evaporating the solvent at room temperature for a period of about two weeks.