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ISSN: 2056-9890

A second monoclinic polymorph of 2,9-di­methyl-1,10-phenanthroline dihydrate

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aDepartment of Physics, Faculty of Arts and Sciences, University of Ondokuz Mayıs, Kurupelit 55139, Samsun, Turkey, and bSchool of Natural Sciences (Chemistry), Bedson Building, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, England
*Correspondence e-mail: w.clegg@ncl.ac.uk

(Received 12 October 2005; accepted 14 October 2005; online 19 October 2005)

A second monoclinic polymorph of the title compound, neocuproine dihydrate, C14H12N2·2H2O, is reported. Unlike the first polymorph [Baggio, Baggio & Mombrú (1998[Baggio, S., Baggio, R. & Mombrú, A. W. (1998). Acta Cryst. C54, 1900-1902.]). Acta Cryst. C54, 1900–1902], in which the phenanthroline ring system was constrained to lie in a crystallographic mirror plane, here there is no such imposed symmetry. Consequently, the mol­ecule shows small deviations from planarity, the outer rings being twisted slightly in opposite directions from the plane of the central ring. The hydrogen-bonding motifs remain essentially the same as in the first polymorph, involving small rings of four water mol­ecules and large rings containing four water mol­ecules and two neocuproine mol­ecules, but with no H-atom disorder for the water mol­ecules in this case. There are also aromatic ππ stacking inter­actions.

Comment

In our ongoing research on squaric acid, we have synthesized some mixed-ligand metal complexes of squaric acid and their structures have been reported (Uçar et al., 2004[Uçar, I., Yeşilel, O. Z., Bulut, A., Ölmez, H. & Büyükgüngör, O. (2004). Acta Cryst. E60, m1025-m1027.], 2005[Uçar, I., Bulut, A. & Büyükgüngör, O. (2005). Acta Cryst. C61, m218-m220.]; Bulut et al., 2004[Bulut, A., Uçar, I., Yeşilel, O. Z., Içbudak, H., Ölmez, H. & Büyükgüngör, O. (2004). Acta Cryst. C60, m526-m528.]). We have used such co-ligands as isonicotinamide and 2,9-dimethyl-1,10-phenanthrolione (neocuproine) in our research and, while synthesizing an iron complex of squaric acid and neocuproine, we obtained crystals of neocuproine dihydrate, (I)[link], as a side product. A unit cell search of the Cambridge Structural Database (CSD, Version 5.26 plus three updates; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]) did not find a match, and it was only by carrying out a structure-based search that we found that a structure of the same compound, also as a dihydrate, had previously been reported (Baggio et al., 1998[Baggio, S., Baggio, R. & Mombrú, A. W. (1998). Acta Cryst. C54, 1900-1902.]). The crystal structure of a hemihydrate has also been determined (Britton et al., 1991[Britton, D., Thompson, L. C. & Holz, R. C. (1991). Acta Cryst. C47, 1101-1103.]). A unit-cell determination with our sample at 298 K gave essentially the same parameters as were determined at 150 K, with the expected slight expansion, and so we are confident that we are reporting the crystal structure of a second monoclinic polymorph of (I)[link], and not the result of a phase transition at low temperature.

[Scheme 1]

This second monoclinic polymorph of (I)[link], shown in Fig. 1[link], crystallizes in space group C2/c with all atoms lying in general positions. Britton et al. (1991[Britton, D., Thompson, L. C. & Holz, R. C. (1991). Acta Cryst. C47, 1101-1103.]) reported some slight tilting of the individual six-membered rings with respect to one another within the phenanthroline system in the hemihydrate. Baggio et al. (1998[Baggio, S., Baggio, R. & Mombrú, A. W. (1998). Acta Cryst. C54, 1900-1902.]) reported that the mol­ecule was exactly planar in the first polymorph of the dihydrate, as a consequence of crystallographic mirror symmetry. A least-squares plane fitted through all non-H atoms of the phenathroline skeleton of (I)[link] has an r.m.s. deviation of 0.024 Å, and the dihedral angle between two mean planes fitted through the outermost rings is 2.37 (2)°, indicating a small deviation of the mol­ecule from planarity. This distortion consists mainly of a twist of the outer rings in opposite directions out of the plane of the central ring, as indicated by the N1—C12—C11—N2 torsion angle of −2.8 (3)°, almost the same as the above dihedral angle.

The overall crystal packing of (I)[link] is similar to that in the first monoclinic polymorph, albeit without the perfectly planar sheets achieved by imposed mirror symmetry. In the first polymorph, H-atom disorder in the water mol­ecules means there is more than one possible orientation of each water mol­ecule and hence some uncertainty about the hydrogen-bonding arrangement. In (I)[link], all H atoms were easily and convincingly located in a difference map and water H atoms were freely refined. The hydrogen-bonding arrangement is shown in Fig. 2[link]. The water mol­ecules form hydrogen bonds around an inversion centre to generate a square R44(8) motif (Bernstein et al., 1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]). A second large R66(18) motif links two neocuproine mol­ecules together via the water mol­ecules.

Unlike the first polymorph, we find no evidence of weak C—H⋯O hydrogen bonding here. However, the separations between parallel neocuproine mol­ecules stacked along the b axis are alternately 3.32 and 3.39 Å, and each mol­ecule has approximately a half-ring overlap with the next mol­ecule in the stack, characteristic of aromatic ππ inter­actions.

[Figure 1]
Figure 1
The asymmetric unit of compound (I)[link], with displacement ellipsoids drawn at the 50% probability level.
[Figure 2]
Figure 2
The hydrogen-bonding motifs in (I)[link]. Dashed lines indicate the hydrogen bonds.

Experimental

Squaric acid, H2Sq (0.57 g, 5 mmol) dissolved in water (25 ml) was neutralized with NaOH (0.40 g, 10 mmol) and the mixture was added to a hot solution of FeCl2·6H2O (1.17 g, 5 mmol) dissolved in water (50 ml). The mixture was stirred at 333 K for 12 h and then cooled to room temperature. The brown crystals that formed were filtered off, washed with water and ethanol, and dried in vacuo. A solution of 2,9-dimethyl-1,10-phenanthroline (0.435 g, 2 mmol) in methanol (50 ml) was added dropwise with stirring to a suspension of FeSq·2H2O (0.21 g, 1 mmol) in water (50 ml). The brown solution was refluxed for about 2 h and then cooled to room temperature. A few days later, brown crystals of the desired Fe complex had formed, along with some well formed colourless crystals of (I)[link] as a side-product.

Crystal data
  • C14H12N2·2H2O

  • Mr = 244.29

  • Monoclinic, C 2/c

  • a = 22.942 (2) Å

  • b = 6.7388 (7) Å

  • c = 17.9594 (18) Å

  • β = 116.019 (2)°

  • V = 2495.2 (4) Å3

  • Z = 8

  • Dx = 1.301 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 6879 reflections

  • θ = 2.4–28.8°

  • μ = 0.09 mm−1

  • T = 150 (2) K

  • Block, colourless

  • 0.61 × 0.38 × 0.21 mm

Data collection
  • Bruker SMART 1K CCD area-detector diffractometer

  • Thin–slice ω scans

  • Absorption correction: multi-scan(SADABS; Sheldrick, 2003[Sheldrick, G. M. (2003). SADABS. University of Göttingen, Germany.])Tmin = 0.928, Tmax = 0.982

  • 8619 measured reflections

  • 2191 independent reflections

  • 1781 reflections with I > 2σ(I)

  • Rint = 0.029

  • θmax = 25.0°

  • h = −27 → 27

  • k = −7 → 8

  • l = −21 → 21

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.062

  • wR(F2) = 0.154

  • S = 1.22

  • 2191 reflections

  • 181 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • w = 1/[σ2(Fo2) + (0.0516P)2 + 4.5458P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.27 e Å−3

  • Δρmin = −0.26 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1O⋯N2 0.84 (4) 2.31 (4) 3.105 (3) 157 (3)
O1—H2O⋯O2 0.87 (5) 1.95 (5) 2.805 (3) 167 (4)
O2—H3O⋯N1i 0.88 (4) 2.15 (4) 3.005 (3) 164 (3)
O2—H4O⋯O1ii 0.89 (3) 1.97 (3) 2.810 (3) 158 (3)
Symmetry codes: (i) x, y-1, z; (ii) [-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z].

All H atoms were located in a difference Fourier map. Water H atoms were freely refined, giving O—H distances shown in Table 1[link]. Other H atoms were treated as riding, with Uiso(H) = 1.2Ueq(C) and C—H = 0.95 Å for aromatic, and Uiso(H) = 1.5Ueq(C) and C—H = 0.98 Å for methyl groups.

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2001[Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2001[Sheldrick, G. M. (2001). SHELXTL. Version 6. Bruker AXS Inc., Madison, Wisconsin, USA.]); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg & Putz, 2004[Brandenburg, K. & Putz, H. (2004). DIAMOND. Version 3. University of Bonn, Germany.]); software used to prepare material for publication: SHELXTL and local programs.

Supporting information


Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg & Putz, 2004); software used to prepare material for publication: SHELXTL and local programs.

2,9-dimethyl-l,10-phenanthroline dihydrate top
Crystal data top
C14H12N2·2H2OF(000) = 1040
Mr = 244.29Dx = 1.301 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 6879 reflections
a = 22.942 (2) Åθ = 2.4–28.8°
b = 6.7388 (7) ŵ = 0.09 mm1
c = 17.9594 (18) ÅT = 150 K
β = 116.019 (2)°Block, colourless
V = 2495.2 (4) Å30.61 × 0.38 × 0.21 mm
Z = 8
Data collection top
Bruker SMART 1K CCD area-detector
diffractometer
2191 independent reflections
Radiation source: sealed tube1781 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.029
Thin–slice ω scansθmax = 25.0°, θmin = 2.0°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
h = 2727
Tmin = 0.928, Tmax = 0.982k = 78
8619 measured reflectionsl = 2121
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)] = 0.062Hydrogen site location: difference Fourier map
wR(F2) = 0.154H atoms treated by a mixture of independent and constrained refinement
S = 1.22 w = 1/[σ2(Fo2) + (0.0516P)2 + 4.5458P]
where P = (Fo2 + 2Fc2)/3
2191 reflections(Δ/σ)max < 0.001
181 parametersΔρmax = 0.27 e Å3
0 restraintsΔρmin = 0.26 e Å3
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
O10.19573 (11)0.4772 (4)0.01527 (15)0.0406 (6)
H1O0.1883 (16)0.553 (6)0.017 (2)0.055 (11)*
H2O0.1861 (18)0.355 (7)0.009 (2)0.073 (13)*
O20.17540 (10)0.0684 (3)0.00899 (12)0.0335 (5)
H3O0.1572 (17)0.035 (6)0.002 (2)0.055 (11)*
H4O0.2143 (16)0.022 (5)0.0011 (18)0.038 (9)*
N10.08861 (9)0.7549 (3)0.00743 (12)0.0206 (5)
N20.20798 (9)0.7166 (3)0.13865 (12)0.0190 (5)
C10.03091 (11)0.7632 (4)0.05702 (15)0.0239 (6)
C20.02721 (12)0.7565 (4)0.04881 (16)0.0299 (6)
H20.06780.76090.09660.036*
C30.02506 (12)0.7436 (4)0.02798 (16)0.0283 (6)
H30.06400.74200.03440.034*
C40.03580 (11)0.7325 (4)0.09819 (16)0.0243 (6)
C50.04243 (12)0.7185 (4)0.18106 (16)0.0301 (6)
H50.00460.71600.19010.036*
C60.10114 (13)0.7087 (4)0.24644 (16)0.0301 (6)
H60.10420.70120.30090.036*
C70.15925 (12)0.7094 (4)0.23481 (15)0.0225 (6)
C80.22152 (12)0.6992 (4)0.30111 (15)0.0256 (6)
H80.22680.69180.35650.031*
C90.27443 (12)0.6998 (4)0.28505 (16)0.0254 (6)
H90.31680.69530.32950.030*
C100.26627 (11)0.7072 (3)0.20277 (15)0.0204 (5)
C110.15525 (11)0.7208 (3)0.15433 (14)0.0191 (5)
C120.09161 (11)0.7366 (3)0.08391 (14)0.0200 (5)
C130.03040 (12)0.7823 (5)0.14102 (15)0.0337 (7)
H13A0.05610.89820.14140.051*
H13B0.01430.79860.18350.051*
H13C0.04910.66250.15280.051*
C140.32325 (11)0.7054 (4)0.18304 (16)0.0272 (6)
H14A0.32460.57860.15710.041*
H14B0.36330.72210.23420.041*
H14C0.31910.81420.14480.041*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0556 (14)0.0307 (12)0.0565 (14)0.0088 (10)0.0440 (12)0.0049 (11)
O20.0324 (11)0.0283 (11)0.0437 (12)0.0050 (9)0.0204 (10)0.0016 (9)
N10.0164 (10)0.0252 (12)0.0200 (10)0.0002 (8)0.0077 (8)0.0009 (9)
N20.0163 (10)0.0201 (10)0.0213 (10)0.0004 (8)0.0089 (8)0.0001 (8)
C10.0195 (12)0.0268 (14)0.0220 (13)0.0010 (10)0.0060 (10)0.0026 (11)
C20.0177 (12)0.0373 (16)0.0288 (14)0.0011 (11)0.0049 (11)0.0027 (12)
C30.0150 (12)0.0370 (16)0.0348 (15)0.0011 (11)0.0125 (11)0.0017 (12)
C40.0183 (12)0.0257 (14)0.0306 (14)0.0015 (10)0.0121 (11)0.0009 (11)
C50.0234 (13)0.0441 (16)0.0309 (14)0.0015 (12)0.0192 (12)0.0031 (13)
C60.0317 (14)0.0395 (16)0.0239 (13)0.0008 (12)0.0166 (12)0.0041 (12)
C70.0248 (13)0.0202 (13)0.0224 (13)0.0009 (10)0.0103 (10)0.0014 (10)
C80.0299 (14)0.0262 (14)0.0169 (12)0.0012 (11)0.0068 (11)0.0001 (10)
C90.0199 (12)0.0245 (13)0.0247 (13)0.0003 (10)0.0032 (10)0.0008 (11)
C100.0154 (12)0.0173 (12)0.0234 (13)0.0000 (9)0.0039 (10)0.0002 (10)
C110.0187 (12)0.0163 (12)0.0219 (12)0.0003 (10)0.0085 (10)0.0005 (10)
C120.0199 (12)0.0188 (12)0.0222 (12)0.0008 (10)0.0100 (10)0.0007 (10)
C130.0242 (13)0.0524 (18)0.0207 (13)0.0001 (13)0.0064 (11)0.0009 (13)
C140.0166 (12)0.0334 (15)0.0279 (14)0.0022 (11)0.0064 (11)0.0012 (12)
Geometric parameters (Å, º) top
O1—H1O0.84 (4)C5—C61.345 (4)
O1—H2O0.87 (5)C6—H60.950
O2—H3O0.88 (4)C6—C71.437 (3)
O2—H4O0.89 (3)C7—C81.404 (3)
N1—C11.323 (3)C7—C111.410 (3)
N1—C121.350 (3)C8—H80.950
N2—C101.329 (3)C8—C91.365 (4)
N2—C111.357 (3)C9—H90.950
C1—C21.405 (4)C9—C101.407 (3)
C1—C131.509 (3)C10—C141.497 (3)
C2—H20.950C11—C121.457 (3)
C2—C31.361 (4)C13—H13A0.980
C3—H30.950C13—H13B0.980
C3—C41.414 (3)C13—H13C0.980
C4—C51.431 (4)C14—H14A0.980
C4—C121.412 (3)C14—H14B0.980
C5—H50.950C14—H14C0.980
H1O—O1—H2O110 (3)C7—C8—C9119.3 (2)
H3O—O2—H4O102 (3)H8—C8—C9120.4
C1—N1—C12118.6 (2)C8—C9—H9120.0
C10—N2—C11118.1 (2)C8—C9—C10120.1 (2)
N1—C1—C2122.5 (2)H9—C9—C10120.0
N1—C1—C13116.4 (2)N2—C10—C9122.1 (2)
C2—C1—C13121.1 (2)N2—C10—C14116.5 (2)
C1—C2—H2120.2C9—C10—C14121.4 (2)
C1—C2—C3119.6 (2)N2—C11—C7123.3 (2)
H2—C2—C3120.2N2—C11—C12117.8 (2)
C2—C3—H3120.3C7—C11—C12118.9 (2)
C2—C3—C4119.3 (2)N1—C12—C4122.7 (2)
H3—C3—C4120.3N1—C12—C11118.3 (2)
C3—C4—C5122.9 (2)C4—C12—C11119.0 (2)
C3—C4—C12117.1 (2)C1—C13—H13A109.5
C5—C4—C12119.9 (2)C1—C13—H13B109.5
C4—C5—H5119.3C1—C13—H13C109.5
C4—C5—C6121.3 (2)H13A—C13—H13B109.5
H5—C5—C6119.3H13A—C13—H13C109.5
C5—C6—H6119.6H13B—C13—H13C109.5
C5—C6—C7120.7 (2)C10—C14—H14A109.5
H6—C6—C7119.6C10—C14—H14B109.5
C6—C7—C8122.7 (2)C10—C14—H14C109.5
C6—C7—C11120.1 (2)H14A—C14—H14B109.5
C8—C7—C11117.2 (2)H14A—C14—H14C109.5
C7—C8—H8120.4H14B—C14—H14C109.5
C12—N1—C1—C20.9 (4)C8—C9—C10—C14179.2 (2)
C12—N1—C1—C13179.6 (2)C10—N2—C11—C72.0 (3)
N1—C1—C2—C30.9 (4)C10—N2—C11—C12178.3 (2)
C13—C1—C2—C3178.6 (3)C6—C7—C11—N2178.1 (2)
C1—C2—C3—C41.4 (4)C6—C7—C11—C121.5 (3)
C2—C3—C4—C5179.9 (3)C8—C7—C11—N21.9 (4)
C2—C3—C4—C120.3 (4)C8—C7—C11—C12178.5 (2)
C3—C4—C5—C6179.8 (3)C1—N1—C12—C42.1 (3)
C12—C4—C5—C60.1 (4)C1—N1—C12—C11178.0 (2)
C4—C5—C6—C70.8 (4)C3—C4—C12—N11.5 (4)
C5—C6—C7—C8179.9 (3)C3—C4—C12—C11178.5 (2)
C5—C6—C7—C110.1 (4)C5—C4—C12—N1178.2 (2)
C6—C7—C8—C9179.7 (2)C5—C4—C12—C111.7 (4)
C11—C7—C8—C90.3 (4)N2—C11—C12—N12.8 (3)
C7—C8—C9—C101.1 (4)N2—C11—C12—C4177.3 (2)
C11—N2—C10—C90.6 (3)C7—C11—C12—N1177.6 (2)
C11—N2—C10—C14179.3 (2)C7—C11—C12—C42.4 (3)
C8—C9—C10—N21.0 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1O···N20.84 (4)2.31 (4)3.105 (3)157 (3)
O1—H2O···O20.87 (5)1.95 (5)2.805 (3)167 (4)
O2—H3O···N1i0.88 (4)2.15 (4)3.005 (3)164 (3)
O2—H4O···O1ii0.89 (3)1.97 (3)2.810 (3)158 (3)
Symmetry codes: (i) x, y1, z; (ii) x+1/2, y+1/2, z.
 

Acknowledgements

The authors thank the EPSRC for equipment and partial studentship funding.

References

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