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The title compound, C18H26N4, contains two almost identical independent mol­ecules that lie about inversion centres. Each mol­ecule has a planar bi­pyridine nucleus and two terminal diethyl­amine groups oriented at almost right angles to the core. These diethyl­amine branches act as spacers, producing a very open structure with one of the lowest densities reported among related compounds. The most important intermolecular interactions are of the C—H...π type, which connect non-equivalent moieties.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104025077/fg1772sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104025077/fg1772Isup2.hkl
Contains datablock I

CCDC reference: 259031

Comment top

Bipyridine ligands have been used extensively to prepare coordination compounds with different metals. Ruthenium polypyridine complexes have been of particular interest because of their photophysical properties (Juris et al., 1988; Kalyanasundaram, 1992). The systematic variation of sustituents on different positions of the aromatic ring has allowed control over the redox and spin properties of these complexes. This possibility makes them attractive for use in applications such as molecular electronics, solar energy conversion and catalysis. In particular, the title compound, 4,4'-bis(diethylamino)-2,2'-bipyridine, (I), has been used to increase the electron density on the metal, lowering its redox potential (Slattery et al., 1994; Curtright et al., 1999)

Compound (I) crystallizes in space group P21/c, with two independent almost identical molecules, A and B, which lie about inversion centres (Fig. 1). In many free bipyridine ligands described in the literature [Cambridge Structural Database (CSD; Allen, 2002) refcodes EDOXAW, EDOXEA, KIDNAP, MILZUC, NAMKAN, NAMKAN01, NAMKAN02, NOFZUD, UHIBAO, VEXQAQ, VEXQAQ01 and VOLLAJ], the individual molecules appear bisected by a symmetry centre, a fact that defines their two most distinctive features, viz. the planarity of the aromatic kernel and the transoid arrangement of the substituents. The planar character of the bipyridyl C10N2 groups about the inversion centres in molecules A and B is almost perfect, with maximum deviations of 0.006 (1) and 0.004 (1) Å for the moieties in A and B, respectively; the bipyridyl planes of molecules A and B are almost perpendicular to one another, subtending an interplanar angle of 89 (1)%. No pseudo-symmetry relating the two moieties could be detected.

The terminal diethylamine ends deviate significantly from the mean plane of the molecular core; this departure is due in part to the slight rotation of the CNC2 groups around the C—N bonds [by 7.1 (1) and 2.1 (1)° for A and B, respectively] and, more importantly, to the orientation of the terminal ethylene moieties almost at right angles out of the bipyridine nucleus. The appearance of the CN(CH2CH3)2 groups suggests approximate? twofold pseudo-symmetry along the C—N bonds, with very similar C—N—C—C torsion angles for each branch [C4A—N7A—C8C—C10A = −91.5 (1)°, C4A—N7A—C9C—C11A = −88.4 (1)°, C4B—N7B—C8C—C10B = −89.5 (1)° and C4B—N7B—C9C—C11B = −96.3 (1)°] As a result, the two independent molecules are almost superposable as assesed by a least-squares fit of the two units, with a mean deviation of 0.10 (1) Å and a maximum deviation of 0.21 (1) Å for to atom C10 (Fig. 2).

As a result of the out-of-plane orientation, the terminal methyl arms act as effective spacers between molecules, precluding any approach between planar groups and consequently any π-π contact, perhaps the most common interaction among unsubstituted aromatic ligands. There are instead some C—H···π close contacts connecting molecules A and B, at almost right angles to one another (Table 3 and Fig. 3). However, these interactions do not seem to provide strong cohesion, as they result in lose packing and an extremely light structure with a calculated density of 1.145 Mg m−3, lower than that of any of the similarly substituted bipyridyl molecules so far reported; the average density of the 12 comparable compounds found in the CSD is 1.26 (8) Mg m−3, with a range of 1.175–1.426 Mg m−3.

Distances and angles in the molecule are unexceptional and match those found in similar ligands.

Experimental top

The compound was prepared according to reported procedures (Maerker & Case, 1958; Slattery et al., 1994)

Refinement top

In spite of having a good external appearance, the crystals were of an extremely poorly diffracting power, as assessed by the low Nobs/Nuniq ratio. All H atoms were included at idealized positions and allowed to ride on their parent atoms, with C—H distances of 0.93–0.97 Å and Uiso(H) values of 1.2–1.5 times Ueq(C). The H atoms of terminal methyl groups were allowed to rotate about the C—C bonds.

Computing details top

Data collection: SMART-NT (Bruker, 2001); cell refinement: SMART-NT; data reduction: SAINT-NT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL/PC (Sheldrick, 1994); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. : An XP (Sheldrick, 1994) view of (I). Displacement ellipsoids are drawn at the 40% probability level. The independent part of each molecule is shown in bold, with the atom-numbering scheme.
[Figure 2] Fig. 2. : A schematic superposition diagram (XP; Sheldrick,G., 1994) of molecules A and B.
[Figure 3] Fig. 3. : A view of the intermolecular interactions, showing C—H···π contacts. Light lines: molecules derived from A; heavy lines: those derived from B. Aromatic H atoms not involved in intermolecular interactions have been omitted for clarity. [Symmetry codes: () 1 − x, 0.5 + y, 0.5 − z; () 1 − x, 1 − y, −z.].
4,4'-Bis(N,N-diethylamino)-2,2'-bipyridine top
Crystal data top
C18H26N4F(000) = 648
Mr = 298.43Dx = 1.143 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 274 reflections
a = 11.0642 (12) Åθ = 3.1–23.4°
b = 11.0554 (12) ŵ = 0.07 mm1
c = 14.3447 (15) ÅT = 293 K
β = 98.754 (2)°Blocks, colorless
V = 1734.2 (3) Å30.22 × 0.20 × 0.20 mm
Z = 4
Data collection top
Bruker SMART CCD area-detector
diffractometer
1646 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.072
Graphite monochromatorθmax = 25.0°, θmin = 1.9°
ϕ and ω scansh = 1313
3053 measured reflectionsk = 013
3053 independent reflectionsl = 017
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.068Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.173H-atom parameters constrained
S = 0.88 w = 1/[σ2(Fo2) + (0.0572P)2 + 1.468P]
where P = (Fo2 + 2Fc2)/3
3053 reflections(Δ/σ)max = 0.002
209 parametersΔρmax = 0.22 e Å3
16 restraintsΔρmin = 0.10 e Å3
Crystal data top
C18H26N4V = 1734.2 (3) Å3
Mr = 298.43Z = 4
Monoclinic, P21/cMo Kα radiation
a = 11.0642 (12) ŵ = 0.07 mm1
b = 11.0554 (12) ÅT = 293 K
c = 14.3447 (15) Å0.22 × 0.20 × 0.20 mm
β = 98.754 (2)°
Data collection top
Bruker SMART CCD area-detector
diffractometer
1646 reflections with I > 2σ(I)
3053 measured reflectionsRint = 0.072
3053 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.06816 restraints
wR(F2) = 0.173H-atom parameters constrained
S = 0.88Δρmax = 0.22 e Å3
3053 reflectionsΔρmin = 0.10 e Å3
209 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N1A0.9061 (2)0.5783 (3)0.57226 (19)0.0668 (8)
C2A0.9370 (3)0.5262 (3)0.4958 (2)0.0505 (8)
C3A0.8604 (3)0.5185 (3)0.4114 (2)0.0601 (9)
H3AA0.88700.47990.36060.072*
C4A0.7423 (3)0.5681 (3)0.4006 (2)0.0663 (10)
C5A0.7113 (3)0.6237 (3)0.4809 (3)0.0698 (10)
H5AA0.63490.65950.47950.084*
C6A0.7939 (3)0.6251 (3)0.5611 (3)0.0746 (11)
H6AA0.76990.66240.61340.090*
N7A0.6645 (3)0.5641 (4)0.3176 (2)0.1031 (13)
C8A0.6929 (4)0.4874 (5)0.2374 (3)0.1118 (16)
H8AA0.74220.41830.26090.134*
H8AB0.61810.45860.19980.134*
C9A0.5418 (4)0.6212 (5)0.3056 (3)0.1140 (18)
H9AA0.54350.69240.34530.137*
H9AB0.51790.64580.24050.137*
C10A0.7583 (5)0.5635 (6)0.1827 (4)0.161 (3)
H10A0.77890.51880.12990.241*
H10B0.83180.59130.22090.241*
H10C0.70840.63160.16030.241*
C11A0.4557 (5)0.5344 (6)0.3316 (4)0.152 (2)
H11A0.37550.56980.32370.228*
H11B0.47930.51140.39640.228*
H11C0.45480.46420.29220.228*
N1B0.4723 (3)0.6601 (3)0.0042 (2)0.0728 (9)
C2B0.4558 (3)0.5437 (3)0.0154 (2)0.0508 (8)
C3B0.3611 (3)0.5043 (3)0.0598 (2)0.0573 (9)
H3BA0.35320.42220.07140.069*
C4B0.2770 (3)0.5851 (3)0.0879 (2)0.0611 (9)
C5B0.2959 (3)0.7063 (3)0.0673 (3)0.0749 (11)
H5BA0.24390.76580.08420.090*
C6B0.3915 (3)0.7367 (3)0.0221 (3)0.0830 (12)
H6BA0.40090.81810.00840.100*
N7B0.1841 (3)0.5505 (3)0.1343 (2)0.0826 (10)
C8B0.1640 (4)0.4224 (4)0.1584 (3)0.0871 (12)
H8BA0.24190.38040.16960.105*
H8BB0.12770.41850.21570.105*
C9B0.0929 (4)0.6359 (4)0.1596 (3)0.0977 (14)
H9BA0.01380.59620.15150.117*
H9BB0.08710.70380.11640.117*
C10B0.0838 (4)0.3636 (4)0.0818 (3)0.1141 (16)
H10E0.07150.28080.09820.171*
H10F0.12040.36660.02530.171*
H10G0.00640.40470.07130.171*
C11B0.1201 (5)0.6819 (5)0.2566 (4)0.134 (2)
H11E0.05680.73680.26820.201*
H11F0.19710.72350.26490.201*
H11G0.12400.61550.30010.201*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N1A0.0549 (17)0.085 (2)0.0584 (18)0.0175 (16)0.0028 (14)0.0068 (16)
C2A0.0498 (18)0.0460 (18)0.0545 (19)0.0023 (14)0.0040 (17)0.0007 (15)
C3A0.051 (2)0.067 (2)0.061 (2)0.0073 (17)0.0034 (17)0.0123 (17)
C4A0.050 (2)0.081 (3)0.066 (2)0.0119 (18)0.0023 (18)0.001 (2)
C5A0.050 (2)0.086 (3)0.072 (2)0.0172 (18)0.006 (2)0.006 (2)
C6A0.068 (2)0.093 (3)0.063 (2)0.017 (2)0.010 (2)0.015 (2)
N7A0.060 (2)0.168 (4)0.074 (2)0.036 (2)0.0100 (18)0.016 (2)
C8A0.073 (3)0.176 (5)0.079 (3)0.015 (3)0.012 (2)0.010 (3)
C9A0.060 (3)0.187 (5)0.090 (3)0.007 (3)0.004 (2)0.026 (3)
C10A0.099 (4)0.271 (8)0.108 (4)0.033 (5)0.001 (3)0.010 (5)
C11A0.105 (4)0.204 (7)0.139 (5)0.015 (4)0.007 (4)0.018 (5)
N1B0.0671 (19)0.0565 (19)0.102 (2)0.0050 (15)0.0366 (17)0.0024 (17)
C2B0.0464 (18)0.053 (2)0.0532 (19)0.0098 (15)0.0092 (15)0.0062 (15)
C3B0.056 (2)0.056 (2)0.060 (2)0.0029 (16)0.0126 (17)0.0009 (16)
C4B0.053 (2)0.069 (2)0.063 (2)0.0043 (18)0.0149 (17)0.0053 (18)
C5B0.068 (2)0.062 (2)0.102 (3)0.0047 (19)0.036 (2)0.012 (2)
C6B0.091 (3)0.052 (2)0.113 (3)0.002 (2)0.038 (3)0.001 (2)
N7B0.068 (2)0.0768 (19)0.114 (3)0.0030 (17)0.0490 (19)0.0003 (19)
C8B0.078 (3)0.094 (2)0.099 (3)0.000 (2)0.043 (2)0.006 (3)
C9B0.079 (3)0.092 (3)0.135 (4)0.006 (2)0.058 (3)0.001 (3)
C10B0.110 (4)0.111 (4)0.125 (4)0.002 (3)0.029 (3)0.007 (3)
C11B0.171 (5)0.117 (4)0.132 (4)0.008 (4)0.080 (4)0.021 (3)
Geometric parameters (Å, º) top
N1A—C2A1.329 (4)N1B—C6B1.326 (4)
N1A—C6A1.331 (4)N1B—C2B1.335 (4)
C2A—C3A1.371 (4)C2B—C3B1.376 (4)
C2A—C2Ai1.498 (6)C2B—C2Bii1.490 (6)
C3A—C4A1.403 (4)C3B—C4B1.392 (4)
C3A—H3AA0.93C3B—H3BA0.93
C4A—N7A1.359 (4)C4B—N7B1.363 (4)
C4A—C5A1.395 (4)C4B—C5B1.395 (4)
C5A—C6A1.357 (4)C5B—C6B1.364 (4)
C5A—H5AA0.93C5B—H5BA0.93
C6A—H6AA0.93C6B—H6BA0.93
N7A—C9A1.483 (5)N7B—C9B1.467 (4)
N7A—C8A1.501 (5)N7B—C8B1.483 (4)
C8A—C10A1.421 (6)C8B—C10B1.457 (5)
C8A—H8AA0.97C8B—H8BA0.97
C8A—H8AB0.97C8B—H8BB0.97
C9A—C11A1.441 (6)C9B—C11B1.469 (5)
C9A—H9AA0.97C9B—H9BA0.97
C9A—H9AB0.97C9B—H9BB0.97
C10A—H10A0.96C10B—H10E0.96
C10A—H10B0.96C10B—H10F0.96
C10A—H10C0.96C10B—H10G0.96
C11A—H11A0.96C11B—H11E0.96
C11A—H11B0.96C11B—H11F0.96
C11A—H11C0.96C11B—H11G0.96
C2A—N1A—C6A114.9 (3)C6B—N1B—C2B115.8 (3)
N1A—C2A—C3A123.6 (3)N1B—C2B—C3B122.7 (3)
N1A—C2A—C2Ai117.1 (3)N1B—C2B—C2Bii116.5 (3)
C3A—C2A—C2Ai119.3 (4)C3B—C2B—C2Bii120.8 (3)
C2A—C3A—C4A120.9 (3)C2B—C3B—C4B121.3 (3)
C2A—C3A—H3AA119.5C2B—C3B—H3BA119.3
C4A—C3A—H3AA119.5C4B—C3B—H3BA119.3
N7A—C4A—C5A122.3 (3)N7B—C4B—C3B123.3 (3)
N7A—C4A—C3A122.6 (3)N7B—C4B—C5B121.4 (3)
C5A—C4A—C3A115.0 (3)C3B—C4B—C5B115.2 (3)
C6A—C5A—C4A119.1 (3)C6B—C5B—C4B119.3 (3)
C6A—C5A—H5AA120.4C6B—C5B—H5BA120.4
C4A—C5A—H5AA120.4C4B—C5B—H5BA120.4
N1A—C6A—C5A126.4 (3)N1B—C6B—C5B125.6 (3)
N1A—C6A—H6AA116.8N1B—C6B—H6BA117.2
C5A—C6A—H6AA116.8C5B—C6B—H6BA117.2
C4A—N7A—C9A122.3 (3)C4B—N7B—C9B122.6 (3)
C4A—N7A—C8A120.7 (3)C4B—N7B—C8B122.2 (3)
C9A—N7A—C8A116.5 (3)C9B—N7B—C8B115.1 (3)
C10A—C8A—N7A105.9 (5)C10B—C8B—N7B110.3 (4)
C10A—C8A—H8AA110.6C10B—C8B—H8BA109.6
N7A—C8A—H8AA110.6N7B—C8B—H8BA109.6
C10A—C8A—H8AB110.6C10B—C8B—H8BB109.6
N7A—C8A—H8AB110.6N7B—C8B—H8BB109.6
H8AA—C8A—H8AB108.7H8BA—C8B—H8BB108.1
C11A—C9A—N7A108.4 (5)N7B—C9B—C11B114.1 (4)
C11A—C9A—H9AA110.0N7B—C9B—H9BA108.7
N7A—C9A—H9AA110.0C11B—C9B—H9BA108.7
C11A—C9A—H9AB110.0N7B—C9B—H9BB108.7
N7A—C9A—H9AB110.0C11B—C9B—H9BB108.7
H9AA—C9A—H9AB108.4H9BA—C9B—H9BB107.6
C8A—C10A—H10A109.5C8B—C10B—H10E109.5
C8A—C10A—H10B109.5C8B—C10B—H10F109.5
H10A—C10A—H10B109.5H10E—C10B—H10F109.5
C8A—C10A—H10C109.5C8B—C10B—H10G109.5
H10A—C10A—H10C109.5H10E—C10B—H10G109.5
H10B—C10A—H10C109.5H10F—C10B—H10G109.5
C9A—C11A—H11A109.5C9B—C11B—H11E109.5
C9A—C11A—H11B109.5C9B—C11B—H11F109.5
H11A—C11A—H11B109.5H11E—C11B—H11F109.5
C9A—C11A—H11C109.5C9B—C11B—H11G109.5
H11A—C11A—H11C109.5H11E—C11B—H11G109.5
H11B—C11A—H11C109.5H11F—C11B—H11G109.5
Symmetry codes: (i) x+2, y+1, z+1; (ii) x+1, y+1, z.

Experimental details

Crystal data
Chemical formulaC18H26N4
Mr298.43
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)11.0642 (12), 11.0554 (12), 14.3447 (15)
β (°) 98.754 (2)
V3)1734.2 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.22 × 0.20 × 0.20
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3053, 3053, 1646
Rint0.072
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.068, 0.173, 0.88
No. of reflections3053
No. of parameters209
No. of restraints16
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.22, 0.10

Computer programs: SMART-NT (Bruker, 2001), SMART-NT, SAINT-NT (Bruker, 2000), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), XP in SHELXTL/PC (Sheldrick, 1994), SHELXL97.

Selected geometric parameters (Å, º) top
N7A—C9A1.483 (5)N7B—C9B1.467 (4)
N7A—C8A1.501 (5)N7B—C8B1.483 (4)
C8A—C10A1.421 (6)C8B—C10B1.457 (5)
C9A—C11A1.441 (6)C9B—C11B1.469 (5)
C9A—N7A—C8A116.5 (3)C9B—N7B—C8B115.1 (3)
C—H···π contacts for (I) top
Group 1/Group 2hpd (Å)hcd (Å)sa (°)
C9A—H9AB
N1A—C6A3.04 (1)3.05 (1)5.2 (2)
C10Aii—H10Aii
N1B-C6B2.93 (1)3.18 (1)23.0 (2)
C10Bi—H10Ei
N1A—C6A2.88 (1)2.92 (1)9.5 (2)
Symmetry codes: (i) 1 − x, 0.5 + y, 0.5 − z; (ii) 1 − x, 1 − y, −z. Notes: hpd is the hydrogen to ring-plane distance, hcd is the hydrogen to ring-center distance and sa is the slippage angle (angle subtended by the hcd vector to the plane normal).
 

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