4,7-Phenanthroline

The structure of 4,7-phenanthroline, C₁₂H₈N₂, has been determined at 180 K. The molecular unit possesses pseudo-C_2v point symmetry but does not possess crystallographic mirror symmetry. The mol­ecules form stacks approximately along the b direction, with mol­ecules in adjacent stacks forming an interplane angle of ca 54°.

Key indicators

• Single-crystal X-ray study
• T = 180 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.063
• wR factor = 0.161
• Data-to-parameter ratio = 8.7

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



STRVAL_01
         From the CIF: _refine_ls_abs_structure_Flack   -3.000
         From the CIF: _refine_ls_abs_structure_Flack_su    8.000
           Alert C Flack parameter is too small

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           25.05
         From the CIF: _reflns_number_total               1099
         Count of symmetry unique reflns          799
         Completeness (_total/calc)            137.55%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured       300
         Fraction of Friedel pairs measured     0.375
         Are heavy atom types Z>Si present           no
          ALERT: MoKa measured Friedel data cannot be used to
                 determine absolute structure in a light-atom
                 study EXCEPT under VERY special conditions.
                 It is preferred that Friedel data is merged in such cases.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

As part of a continuing study of cocrystal formation between organic acids and N-containing organic bases, we have determined the structure of 4,7-phenanthroline, (I), at 180 K. The molecular unit possesses pseudo-C2v point symmetry, but does not exhibit crystallographic mirror symmetry. Similar observations have been made for the isomeric 1,10-phenanthroline (OPENAN; Nishigaki et al., 1978). In the crystal structure, 4,7-phenanthroline forms planar stacks approximately along the b direction with molecules in adjacent stacks forming an interplane angle of ca 54° (Fig. 2); this contrasts with the observation of two approximately perpendicular layers in 1,10-phenanthroline. There is no conclusive evidence for directional C—H···N contacts in 4,7-phenanthroline, with the shortest H···N contacts, H1···N7ⁱ = 2.72, H8···N4ⁱⁱ = 3.00 and H10···N7ⁱⁱⁱ = 3.00 Å, exhibiting C—H···N angles of 153.6, 128.6 and 119.5°, respectively [symmetry codes: (i) 3/2 - x, -1 + y, 1/2 + z; (ii) 1/2 + x, 1 - y, z; (iii) 3/2 - x, y, 1/2 + z].

S2. Experimental

4,7-Phenanthroline was obtained from Aldrich and recrystallized from ethanol.

S3. Refinement

The absolute structure was not determined. Friedel opposites merged prior to merging of data in Pca2₁. H atoms were placed geometrically and allowed to ride during subsequent refinement with an isotropic displacement parameter fixed at 1.2 times U_iso for the C atom to which they are attached.

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Sheldrick, 1993); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular unit of the title compound showing displacement ellipsoids at the 50% probability level.
	Fig. 2. Projection onto (100) showing molecular stacks tilted with respect to each other with molecules in adjacent stacks forming an interplane angle of ca 54°.

4,7-phenanthroline

Crystal data

C12H8N2	Dx = 1.408 Mg m^−3
Mr = 180.20	Melting point = 445–447 K
Orthorhombic, Pca21	Mo Kα radiation, λ = 0.71073 Å
a = 19.141 (4) Å	Cell parameters from 6723 reflections
b = 3.8417 (4) Å	θ = 1.0–25.0°
c = 11.564 (2) Å	µ = 0.09 mm^−1
V = 850.4 (3) Å^3	T = 180 K
Z = 4	Plate, colourless
F(000) = 376	0.30 × 0.09 × 0.05 mm

Data collection

Nonius KappaCCD diffractometer	1099 independent reflections
Radiation source: fine-focus sealed tube	812 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.080
Thin slice ω and ϕ scans	θmax = 25.1°, θmin = 3.5°
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	h = −22→17
Tmin = 0.975, Tmax = 0.996	k = −4→3
2186 measured reflections	l = −13→10

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.063	H-atom parameters constrained
wR(F^2) = 0.161	w = 1/[σ^2(Fo^2) + (0.078P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max = 0.002
1099 reflections	Δρmax = 0.30 e Å^−3
127 parameters	Δρmin = −0.27 e Å^−3
1 restraint	Absolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −3 (8)

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	0.6207 (3)	0.1033 (11)	0.5044 (4)	0.0310 (11)
H1	0.6586	0.0434	0.5535	0.037*
C2	0.5535 (3)	0.0311 (12)	0.5378 (5)	0.0375 (13)
H2	0.5440	−0.0760	0.6102	0.045*
C3	0.4995 (3)	0.1194 (12)	0.4625 (5)	0.0387 (13)
H3	0.4531	0.0682	0.4860	0.046*
N4	0.5083 (2)	0.2693 (10)	0.3606 (4)	0.0373 (11)
C5	0.5853 (3)	0.5139 (12)	0.2191 (4)	0.0350 (13)
H5	0.5459	0.5658	0.1724	0.042*
C6	0.6492 (3)	0.5988 (12)	0.1814 (4)	0.0329 (12)
H6	0.6543	0.7110	0.1086	0.039*
N7	0.7727 (2)	0.6174 (10)	0.2027 (4)	0.0390 (12)
C8	0.8289 (3)	0.5474 (13)	0.2656 (5)	0.0390 (14)
H8	0.8732	0.6078	0.2346	0.047*
C9	0.8271 (3)	0.3908 (11)	0.3745 (5)	0.0382 (13)
H9	0.8692	0.3517	0.4162	0.046*
C10	0.7644 (2)	0.2944 (11)	0.4206 (4)	0.0312 (11)
H10	0.7622	0.1868	0.4945	0.037*
C11	0.7030 (3)	0.3573 (11)	0.3568 (4)	0.0298 (11)
C12	0.6336 (2)	0.2649 (12)	0.3981 (4)	0.0268 (11)
C13	0.5751 (2)	0.3463 (11)	0.3286 (4)	0.0307 (12)
C14	0.7098 (3)	0.5227 (12)	0.2492 (4)	0.0316 (12)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.035 (3)	0.030 (3)	0.028 (3)	0.003 (2)	−0.005 (2)	−0.002 (2)
C2	0.038 (3)	0.035 (3)	0.040 (3)	0.005 (2)	0.006 (3)	−0.004 (2)
C3	0.033 (3)	0.035 (3)	0.048 (3)	−0.006 (2)	0.007 (3)	−0.006 (2)
N4	0.032 (3)	0.038 (2)	0.041 (2)	0.0010 (18)	0.000 (2)	−0.006 (2)
C5	0.040 (3)	0.035 (3)	0.030 (3)	0.004 (2)	−0.011 (3)	−0.005 (2)
C6	0.046 (3)	0.029 (3)	0.024 (3)	0.003 (2)	−0.003 (2)	0.000 (2)
N7	0.044 (3)	0.038 (2)	0.035 (3)	−0.0064 (18)	0.009 (2)	−0.0063 (19)
C8	0.030 (3)	0.043 (3)	0.044 (3)	−0.003 (2)	0.006 (3)	−0.007 (2)
C9	0.035 (3)	0.040 (3)	0.039 (3)	0.002 (2)	−0.009 (3)	−0.006 (3)
C10	0.030 (3)	0.033 (2)	0.031 (3)	0.002 (2)	−0.002 (2)	−0.001 (2)
C11	0.033 (3)	0.024 (2)	0.032 (3)	0.0033 (19)	0.002 (2)	−0.005 (2)
C12	0.032 (3)	0.021 (2)	0.027 (2)	0.0007 (18)	−0.004 (2)	−0.0080 (18)
C13	0.031 (3)	0.028 (3)	0.034 (3)	0.0007 (19)	−0.002 (2)	−0.010 (2)
C14	0.035 (3)	0.028 (3)	0.032 (3)	0.001 (2)	0.003 (2)	−0.006 (2)

Geometric parameters (Å, º)

C1—C2	1.371 (7)	C6—H6	0.9500
C1—C12	1.398 (7)	N7—C8	1.327 (6)
C1—H1	0.9500	N7—C14	1.367 (6)
C2—C3	1.394 (7)	C8—C9	1.396 (7)
C2—H2	0.9500	C8—H8	0.9500
C3—N4	1.322 (7)	C9—C10	1.364 (7)
C3—H3	0.9500	C9—H9	0.9500
N4—C13	1.364 (6)	C10—C11	1.410 (7)
C5—C6	1.338 (7)	C10—H10	0.9500
C5—C13	1.434 (7)	C11—C14	1.403 (6)
C5—H5	0.9500	C11—C12	1.455 (6)
C6—C14	1.431 (7)	C12—C13	1.414 (6)
C2—C1—C12	120.3 (5)	C9—C8—H8	117.9
C2—C1—H1	119.9	C10—C9—C8	119.4 (5)
C12—C1—H1	119.9	C10—C9—H9	120.3
C1—C2—C3	118.0 (6)	C8—C9—H9	120.3
C1—C2—H2	121.0	C9—C10—C11	118.9 (5)
C3—C2—H2	121.0	C9—C10—H10	120.6
N4—C3—C2	124.6 (5)	C11—C10—H10	120.6
N4—C3—H3	117.7	C14—C11—C10	117.7 (4)
C2—C3—H3	117.7	C14—C11—C12	119.2 (4)
C3—N4—C13	117.1 (5)	C10—C11—C12	123.2 (4)
C6—C5—C13	121.5 (5)	C1—C12—C13	117.2 (4)
C6—C5—H5	119.3	C1—C12—C11	124.0 (4)
C13—C5—H5	119.3	C13—C12—C11	118.8 (4)
C5—C6—C14	120.8 (5)	N4—C13—C12	122.8 (4)
C5—C6—H6	119.6	N4—C13—C5	117.7 (4)
C14—C6—H6	119.6	C12—C13—C5	119.6 (4)
C8—N7—C14	116.4 (4)	N7—C14—C11	123.4 (4)
N7—C8—C9	124.2 (5)	N7—C14—C6	116.4 (5)
N7—C8—H8	117.9	C11—C14—C6	120.2 (4)
C12—C1—C2—C3	0.8 (6)	C3—N4—C13—C5	−179.1 (4)
C1—C2—C3—N4	−0.1 (7)	C1—C12—C13—N4	−1.0 (6)
C2—C3—N4—C13	−1.0 (6)	C11—C12—C13—N4	180.0 (4)
C13—C5—C6—C14	0.4 (7)	C1—C12—C13—C5	179.7 (4)
C14—N7—C8—C9	−0.9 (6)	C11—C12—C13—C5	0.6 (6)
N7—C8—C9—C10	1.3 (7)	C6—C5—C13—N4	179.9 (4)
C8—C9—C10—C11	−0.2 (6)	C6—C5—C13—C12	−0.7 (6)
C9—C10—C11—C14	−1.1 (6)	C8—N7—C14—C11	−0.5 (6)
C9—C10—C11—C12	−179.9 (4)	C8—N7—C14—C6	179.9 (4)
C2—C1—C12—C13	−0.2 (6)	C10—C11—C14—N7	1.5 (6)
C2—C1—C12—C11	178.7 (4)	C12—C11—C14—N7	−179.6 (4)
C14—C11—C12—C1	−179.3 (4)	C10—C11—C14—C6	−178.9 (4)
C10—C11—C12—C1	−0.4 (6)	C12—C11—C14—C6	0.0 (6)
C14—C11—C12—C13	−0.3 (6)	C5—C6—C14—N7	179.5 (4)
C10—C11—C12—C13	178.6 (4)	C5—C6—C14—C11	0.0 (7)
C3—N4—C13—C12	1.6 (6)