9,9-Bis(4-methoxy­phen­yl)-9H-cyclo­penta­[2,1-b:3,4-b']dipyridine

The title compound, C₂₅H₂₀N₂O₂, was synthesized by the Friedel-Crafts reaction of 4,5-diaza­fluoren-9-one with anisole in the presence of H₂SO₄. The mol­ecule is located on a twofold rotation axis. The 4,5-diaza­fluorene (cyclo­penta­[2,1-b:3,4-b']dipyridine) ring system is planar. The mol­ecular packing is characterized by a columnar structure along the c axis. The methoxy­phenyl groups overlap each other in the column. The inter­planar distance and the centroid-centroid distances between the benzene rings are 3.87 (1) and 4.07 (1) Å, respectively. The 4,5-diaza­fluorene units form a coil-like structure.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.091
• wR factor = 0.147
• Data-to-parameter ratio = 9.8

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         C8
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          6

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.48
           From the CIF: _reflns_number_total               1302
           Count of symmetry unique reflns         1309
           Completeness (_total/calc)             99.47%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

The title compound, (I), was prepared and investigated for electron-transporting layers in the study of organic electroluminescent (EL) devices (Ono et al., 2004). Phosphorescent EL devices fabricated by (I) and Ir(ppy)₃ demonstrated high external quantum efficiencies due to the high hole-blocking ability of (I). One of the phosphorescent EL devices exhibited a maximum external quantum efficiency of 18%. This value is close to the theoretical limit about 20% from simple classical optics. With regard to the electron-transporting and hole-blocking abilities, the molecular arrangement of (I) has attracted considerable attention. In this paper, we report the crystal structure of (I).

The compound, (I), crystallizes in the P4₁2₁2 space group and is located on a twofold rotation axis. The molecular structure is shown in Fig. 1. The bond lengths and angles are all within the expected ranges. The 4,5-diazafluorene (cyclopenta[2,1-b:3,4-b']dipyridine) ring system and the two methoxyphenyl groups are planar. The crystal structure is characterized by a columnar structure along the c axis, as shown in Fig. 2. The methoxyphenyl groups overlap each other in the column. The interplanar distance and the centroid-centroid distance between the benzene rings (C7—C12) at (x, y, z) and (–y, –x, –z + 3/2) are 3.87 (1) and 4.07 (1) Å, respectively. The diazafluorene moieties are arranged to form a coil-like structure.

Related literature

The title compound was reported as an electron-transporting and hole-blocking material in the study of electroluminescent (EL) devices (Ono et al., 2004). For related literature on molecular structures including the 4,5-diazafluorene ring system, see: Ono et al. (2007); Riklin et al. (1999); Fun et al. (1995); Lu et al. (1995, 2000).

S2. Experimental

The title compound (I) was prepared as follows: Concentrated sulfuric acid (1.37 g, 14.0 mmol) was added dropwise to a mixture of 4,5-diazafluoren-9-one (0.50 g, 2.8 mmol) and anisole (1.19 g, 11.0 mmol). The mixture was stirred at 65 °C for 5 h. The red mixture was poured into water (50 ml). The aqueous solution was neutralized with aqueous NaOH and was extracted with dichloromethane (50 ml × 3). The organic solution was dried over Na₂SO₄ and concentrated. The residue was treated with active carbon and recrystallized from toluene to afford the compound of (I) (0.99 g, 95%) as colorless needles. Physical data for (I): m.p. 548–549 K; IR (KBr, cm^-1): 2949, 2830, 1562, 1507, 1402, 1250, 1179, 1040, 814, 747, 592, 513; ¹H NMR (CDCl₃, δ p.p.m.): 3.76 (s, 6H), 6.77 (d, J = 8.8 Hz, 4H), 7.08 (d, J = 8.8 Hz, 4H), 7.27 (dd, J = 7.8, 4.7 Hz, 2H), 7.74 (d, J = 7.8, 1.4 Hz, 2H), 8.72 (d, J = 4.7, 1.4 Hz, 2H); ¹³C NMR (CDCl₃, δ p.p.m.): 55.2, 60.2, 113.9, 123.4, 128.9, 133.5, 135.7, 146.2, 150.0, 157.4, 158.7; MS (EI): m/z 380 (M⁺), 365, 273. Anal. Calcd for C₂₅H₂₀N₂O₂: C, 78.93; H, 5.30; N, 7.36. Found: C, 78.72; H, 5.27; N, 7.16. Colorless crystals of (I) suitable for X-ray analysis were grown from a toluene solution.

S3. Refinement

All the H atoms were placed in geometrically calculated positions [C—H = 0.93 (aromatic) or 0.96 (methyl) Å] and refined using a riding model, with U_iso(H) = 1.2U_eq(C) (aromatic) or 1.5U_eq(C) (methyl).

Computing details

Data collection: CrystalClear (Rigaku/MSC, 2001); cell refinement: CrystalClear (Rigaku/MSC, 2001); data reduction: CrystalClear (Rigaku/MSC, 2001); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms and H atoms are shown as small spheres of arbitrary radii [symmetry code: (i) y, x, –z + 1].
	Fig. 2. The packing diagram of (I) stacked along the c axis.

9,9-Bis(4-methoxyphenyl)-9H-cyclopenta[2,1 - b:3,4 - b']dipyridine

Crystal data

C25H20N2O2	Dx = 1.33 Mg m^−3
Mr = 380.45	Melting point: 548 K
Tetragonal, P41212	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 4abw 2nw	Cell parameters from 4891 reflections
a = 11.607 (3) Å	θ = 3.4–27.5°
c = 14.101 (4) Å	µ = 0.09 mm^−1
V = 1899.7 (8) Å^3	T = 296 K
Z = 4	Block, colorless
F(000) = 800	0.45 × 0.15 × 0.15 mm

Data collection

Rigaku/MSC Mercury CCD diffractometer	1241 reflections with I > 2σ(I)
Radiation source: Rotating Anode	Rint = 0.075
Graphite Monochromator monochromator	θmax = 27.5°, θmin = 3.4°
Detector resolution: 14.6199 pixels mm^-1	h = −13→15
ϕ & ω scans	k = −12→15
19259 measured reflections	l = −17→18
1302 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.091	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.147	H-atom parameters constrained
S = 1.44	w = 1/[σ^2(Fo^2) + (0.0183P)^2 + 1.2171P] where P = (Fo^2 + 2Fc^2)/3
1302 reflections	(Δ/σ)max < 0.001
133 parameters	Δρmax = 0.16 e Å^−3
0 restraints	Δρmin = −0.15 e Å^−3

Special details

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.

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 (Ų)

	x	y	z	Uiso*/Ueq
C1	0.3328 (4)	0.1272 (4)	0.6615 (3)	0.0523 (12)
C2	0.2771 (4)	0.0298 (4)	0.6906 (3)	0.0546 (12)
C3	0.1809 (4)	−0.0082 (4)	0.6424 (3)	0.0508 (11)
C4	0.1441 (4)	0.0559 (3)	0.5655 (3)	0.0385 (9)
C5	0.2069 (3)	0.1531 (4)	0.5412 (3)	0.0385 (9)
C6	0.0393 (3)	0.0393 (3)	0.5000	0.0425 (13)
C7	−0.0704 (3)	0.0456 (4)	0.5597 (3)	0.0420 (10)
C8	−0.1053 (5)	−0.0487 (4)	0.6134 (4)	0.0706 (16)
C9	−0.1985 (4)	−0.0430 (4)	0.6750 (4)	0.0669 (15)
C10	−0.2601 (4)	0.0560 (4)	0.6819 (3)	0.0456 (10)
C11	−0.2274 (4)	0.1509 (4)	0.6310 (3)	0.0525 (12)
C12	−0.1330 (4)	0.1456 (4)	0.5712 (3)	0.0471 (10)
C13	−0.3879 (4)	−0.0191 (5)	0.7990 (3)	0.0688 (15)
N1	0.3003 (3)	0.1914 (3)	0.5868 (2)	0.0472 (9)
O1	−0.3561 (3)	0.0714 (3)	0.7388 (2)	0.0615 (9)
H1	0.3973	0.1507	0.6955	0.063*
H2	0.3041	−0.0110	0.7428	0.066*
H3	0.1421	−0.0746	0.6609	0.061*
H8	−0.0650	−0.1176	0.6079	0.085*
H9	−0.2185	−0.1067	0.7114	0.080*
H11	−0.2688	0.2191	0.6366	0.063*
H12	−0.1111	0.2113	0.5380	0.056*
H13A	−0.4144	−0.0831	0.7618	0.103*
H13B	−0.4486	0.0061	0.8404	0.103*
H13C	−0.3227	−0.0424	0.8362	0.103*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.049 (3)	0.062 (3)	0.046 (2)	0.006 (2)	−0.007 (2)	−0.008 (2)
C2	0.069 (3)	0.054 (3)	0.041 (2)	0.015 (3)	−0.004 (2)	0.001 (2)
C3	0.064 (3)	0.040 (2)	0.049 (2)	−0.002 (2)	0.006 (2)	0.001 (2)
C4	0.045 (2)	0.033 (2)	0.0371 (19)	0.0025 (18)	0.0056 (18)	−0.0065 (17)
C5	0.038 (2)	0.039 (2)	0.0389 (18)	0.0002 (19)	0.0024 (17)	−0.0075 (18)
C6	0.0374 (19)	0.0374 (19)	0.053 (3)	−0.005 (3)	0.004 (2)	−0.004 (2)
C7	0.041 (2)	0.039 (2)	0.046 (2)	−0.0097 (18)	0.0084 (19)	−0.0049 (19)
C8	0.074 (4)	0.034 (3)	0.104 (4)	0.002 (2)	0.043 (3)	−0.012 (3)
C9	0.070 (3)	0.042 (3)	0.088 (4)	−0.012 (3)	0.036 (3)	−0.004 (3)
C10	0.041 (2)	0.050 (3)	0.046 (2)	−0.003 (2)	0.0061 (19)	−0.010 (2)
C11	0.053 (3)	0.048 (3)	0.056 (2)	0.014 (2)	0.009 (2)	0.006 (2)
C12	0.047 (3)	0.046 (2)	0.048 (2)	0.008 (2)	0.009 (2)	0.009 (2)
C13	0.069 (4)	0.076 (4)	0.061 (3)	−0.009 (3)	0.022 (3)	−0.005 (3)
N1	0.045 (2)	0.047 (2)	0.0491 (19)	−0.0044 (17)	−0.0041 (17)	−0.0074 (18)
O1	0.054 (2)	0.063 (2)	0.0671 (19)	0.0007 (18)	0.0269 (18)	0.0025 (18)

Geometric parameters (Å, º)

C1—N1	1.344 (6)	C7—C8	1.391 (6)
C1—C2	1.366 (7)	C8—C9	1.389 (6)
C1—H1	0.9300	C8—H8	0.9300
C2—C3	1.380 (6)	C9—C10	1.357 (6)
C2—H2	0.9300	C9—H9	0.9300
C3—C4	1.381 (6)	C10—C11	1.368 (6)
C3—H3	0.9300	C10—O1	1.384 (5)
C4—C5	1.386 (6)	C11—C12	1.384 (6)
C4—C6	1.540 (5)	C11—H11	0.9300
C5—N1	1.336 (5)	C12—H12	0.9300
C5—C5^i	1.458 (8)	C13—O1	1.401 (5)
C6—C7	1.528 (5)	C13—H13A	0.9600
C6—C7^i	1.528 (5)	C13—H13B	0.9600
C6—C4^i	1.540 (5)	C13—H13C	0.9600
C7—C12	1.379 (5)
N1—C1—C2	124.1 (4)	C9—C8—C7	121.9 (5)
N1—C1—H1	118.0	C9—C8—H8	119.0
C2—C1—H1	118.0	C7—C8—H8	119.0
C1—C2—C3	120.0 (4)	C10—C9—C8	119.7 (5)
C1—C2—H2	120.0	C10—C9—H9	120.1
C3—C2—H2	120.0	C8—C9—H9	120.1
C2—C3—C4	117.7 (4)	C9—C10—C11	119.8 (4)
C2—C3—H3	121.2	C9—C10—O1	125.1 (4)
C4—C3—H3	121.2	C11—C10—O1	115.1 (4)
C3—C4—C5	118.1 (4)	C10—C11—C12	120.3 (4)
C3—C4—C6	130.3 (4)	C10—C11—H11	119.9
C5—C4—C6	111.6 (3)	C12—C11—H11	119.9
N1—C5—C4	125.3 (4)	C7—C12—C11	121.7 (4)
N1—C5—C5^i	126.0 (2)	C7—C12—H12	119.1
C4—C5—C5^i	108.7 (2)	C11—C12—H12	119.1
C7—C6—C7^i	112.5 (5)	O1—C13—H13A	109.5
C7—C6—C4^i	113.4 (2)	O1—C13—H13B	109.5
C7^i—C6—C4^i	108.8 (2)	H13A—C13—H13B	109.5
C7—C6—C4	108.8 (2)	O1—C13—H13C	109.5
C7^i—C6—C4	113.4 (2)	H13A—C13—H13C	109.5
C4^i—C6—C4	99.3 (4)	H13B—C13—H13C	109.5
C12—C7—C8	116.5 (4)	C5—N1—C1	114.9 (4)
C12—C7—C6	122.9 (4)	C10—O1—C13	117.9 (4)
C8—C7—C6	120.3 (4)
N1—C1—C2—C3	−0.2 (7)	C4^i—C6—C7—C8	171.8 (4)
C1—C2—C3—C4	−0.3 (6)	C4—C6—C7—C8	−78.7 (5)
C2—C3—C4—C5	0.8 (6)	C12—C7—C8—C9	0.3 (8)
C2—C3—C4—C6	−177.8 (4)	C6—C7—C8—C9	174.1 (4)
C3—C4—C5—N1	−0.8 (6)	C7—C8—C9—C10	1.8 (8)
C6—C4—C5—N1	178.0 (3)	C8—C9—C10—C11	−2.5 (8)
C3—C4—C5—C5^i	−180.0 (4)	C8—C9—C10—O1	178.3 (4)
C6—C4—C5—C5^i	−1.2 (5)	C9—C10—C11—C12	1.2 (7)
C3—C4—C6—C7	60.3 (5)	O1—C10—C11—C12	−179.6 (4)
C5—C4—C6—C7	−118.3 (4)	C8—C7—C12—C11	−1.8 (7)
C3—C4—C6—C7^i	−65.7 (5)	C6—C7—C12—C11	−175.4 (4)
C5—C4—C6—C7^i	115.7 (4)	C10—C11—C12—C7	1.1 (7)
C3—C4—C6—C4^i	179.1 (5)	C4—C5—N1—C1	0.3 (6)
C5—C4—C6—C4^i	0.5 (2)	C5^i—C5—N1—C1	179.4 (5)
C7^i—C6—C7—C12	−138.8 (5)	C2—C1—N1—C5	0.2 (6)
C4^i—C6—C7—C12	−14.8 (6)	C9—C10—O1—C13	4.7 (7)
C4—C6—C7—C12	94.7 (4)	C11—C10—O1—C13	−174.5 (4)
C7^i—C6—C7—C8	47.8 (4)

Symmetry code: (i) y, x, −z+1.