The title compound, [Cu(C
9H
5N
2O
3)
2(C
2H
6OS)
2], consists of octahedrally coordinated Cu
II ions, with the 3-oxo-3,4-dihydroquinoxaline-2-carboxylate ligands acting in a bidentate manner [Cu—O = 1.9116 (14) Å and Cu—N = 2.1191 (16) Å] and a dimethyl sulfoxide (DMSO) molecule coordinated axially
via the O atom [Cu—O = 2.336 (5) and 2.418 (7) Å for the major and minor disorder components, respectively]. The whole DMSO molecule exhibits positional disorder [0.62 (1):0.38 (1)]. The octahedron around the Cu
II atom, which lies on an inversion centre, is elongated in the axial direction, exhibiting a Jahn–Teller effect. The ligand exhibits tautomerization by H-atom transfer from the hydroxyl group at position 3 to the N atom at position 4 of the quinoxaline ring of the ligand. The complex molecules are linked through an intermolecular N—H
O hydrogen bond [N
O = 2.838 (2) Å] formed between the quinoxaline NH group and a carboxylate O atom, and by a weak intermolecular C—H
O hydrogen bond [3.392 (11) Å] formed between a carboxylate O atom and a methyl C atom of the DMSO ligand. There is a weak intramolecular C—H
O hydrogen bond [3.065 (3) Å] formed between a benzene CH group and a carboxylate O atom.
Supporting information
CCDC reference: 649062
A suspension of copper(II) hydroxide (0.03 g, 0.31 mmol) and
3-hydroxy-2-quinoxalinecarboxylic acid (0.12 g, 0.63 mmol) in dimethyl
sulfoxide (20 ml) (molar ratio 1:2) was refluxed for 4 h to give a dark-red
solution. Slow evaporation of this solution at room temperature yielded brown
crystals of the title compound suitable for X-ray analysis.
The DMSO molecule exhibits positional disorder, which was easily resolved as
0.62(s.u.?):0.38(s.u.?) beginning with the electron density found in
difference Fourier maps and refined using SHELXL97 instructions FVAR
and PART (Sheldrick, 1997). The S—Cmethyl bond distances were
restrained using the SHELXL97 DFIX instruction to the average values of
1.782 (2) and 1.786 (2) Å for the S—C11 and S—C10 bonds, respectively
(Table 1). Atoms C10A and C10B were refined anisotropically in
order to model as faithfully as possible the electron density in the
disordered region, but these displacement parameters should not be taken as
faithful representations of atomic displacement for these atoms. The H atom
belonging to the quinoxaline N atom was found in a difference Fourier map at
the final stages of refinement as a small electron density (approximately 0.5 e Å-3) and refined freely (Table 2). H atoms bonded to C atoms were
introduced in calculated positions and refined using a riding model, with
C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C) for phenyl H, and
with C—H = 0.96 Å and 1.5Ueq(C) for methyl H. Due to the
absorption coefficient and crystal dimensions, the absorption effect was
minimized using the multi-scan technique.
Data collection: CrysAlis CCD (Oxford Diffraction, 2004); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON98 (Spek, 1998); software used to prepare material for publication: SHELXL97.
trans-Bis(dimethyl
sulfoxide-
κO)bis(3-oxoquinoxaline-2-carboxylato-
κ2N1,
O2)copper(II)
top
Crystal data top
[Cu(C9H5N2O3)2(C2H6OS)2] | F(000) = 614 |
Mr = 598.13 | Dx = 1.637 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 4736 reflections |
a = 9.4426 (1) Å | θ = 15.5–20.5° |
b = 8.3584 (1) Å | µ = 1.13 mm−1 |
c = 15.7881 (3) Å | T = 296 K |
β = 103.213 (2)° | Prism, brown |
V = 1213.09 (3) Å3 | 0.43 × 0.43 × 0.10 mm |
Z = 2 | |
Data collection top
Oxford Xcalibur2 diffractometer with a Sapphire-3 CCD area-detector | 2625 independent reflections |
Radiation source: fine-focus sealed tube | 2280 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.021 |
ω scans | θmax = 27.0°, θmin = 3.9° |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | h = −12→12 |
Tmin = 0.810, Tmax = 1.000 | k = −10→10 |
15817 measured reflections | l = −20→20 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.035 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.11 | w = 1/[σ2(Fo2) + (0.0393P)2 + 0.6834P] where P = (Fo2 + 2Fc2)/3 |
2624 reflections | (Δ/σ)max = 0.001 |
214 parameters | Δρmax = 0.39 e Å−3 |
4 restraints | Δρmin = −0.31 e Å−3 |
Crystal data top
[Cu(C9H5N2O3)2(C2H6OS)2] | V = 1213.09 (3) Å3 |
Mr = 598.13 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 9.4426 (1) Å | µ = 1.13 mm−1 |
b = 8.3584 (1) Å | T = 296 K |
c = 15.7881 (3) Å | 0.43 × 0.43 × 0.10 mm |
β = 103.213 (2)° | |
Data collection top
Oxford Xcalibur2 diffractometer with a Sapphire-3 CCD area-detector | 2625 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | 2280 reflections with I > 2σ(I) |
Tmin = 0.810, Tmax = 1.000 | Rint = 0.021 |
15817 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.035 | 4 restraints |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.11 | Δρmax = 0.39 e Å−3 |
2624 reflections | Δρmin = −0.31 e Å−3 |
214 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Cu1 | 0.0000 | 0.0000 | 0.0000 | 0.03484 (13) | |
O1 | 0.04486 (17) | −0.15477 (19) | 0.09136 (10) | 0.0439 (4) | |
O2 | −0.01249 (17) | −0.23633 (19) | 0.21228 (10) | 0.0429 (4) | |
O3 | −0.1942 (2) | −0.0171 (2) | 0.27400 (10) | 0.0545 (5) | |
N1 | −0.18881 (18) | 0.02291 (19) | 0.05023 (10) | 0.0318 (4) | |
C1 | −0.1558 (2) | −0.0312 (2) | 0.12928 (12) | 0.0282 (4) | |
C2 | −0.2315 (2) | 0.0207 (2) | 0.19746 (13) | 0.0349 (4) | |
N2 | −0.3424 (2) | 0.1245 (2) | 0.16708 (12) | 0.0388 (4) | |
H1N2 | −0.378 (3) | 0.165 (3) | 0.1999 (17) | 0.051 (8)* | |
C3 | −0.3900 (2) | 0.1696 (2) | 0.08175 (13) | 0.0344 (4) | |
C4 | −0.5127 (3) | 0.2654 (3) | 0.05343 (17) | 0.0499 (6) | |
H4 | −0.5653 | 0.3015 | 0.0928 | 0.060* | |
C5 | −0.5552 (3) | 0.3061 (3) | −0.03248 (19) | 0.0543 (6) | |
H5 | −0.6370 | 0.3701 | −0.0512 | 0.065* | |
C6 | −0.4783 (3) | 0.2533 (3) | −0.09236 (17) | 0.0520 (6) | |
H6 | −0.5091 | 0.2817 | −0.1506 | 0.062* | |
C7 | −0.3571 (3) | 0.1594 (3) | −0.06597 (15) | 0.0450 (5) | |
H7 | −0.3057 | 0.1240 | −0.1061 | 0.054* | |
C8 | −0.3112 (2) | 0.1172 (2) | 0.02193 (13) | 0.0330 (4) | |
C9 | −0.0312 (2) | −0.1496 (2) | 0.14881 (13) | 0.0321 (4) | |
S1 | 0.10998 (11) | 0.35069 (12) | 0.10119 (7) | 0.0498 (4) | 0.623 (3) |
O4A | 0.1019 (5) | 0.1718 (5) | 0.1144 (3) | 0.0562 (10) | 0.623 (3) |
C10A | −0.0687 (5) | 0.4275 (10) | 0.0948 (7) | 0.094 (4) | 0.623 (3) |
H10A | −0.1363 | 0.3746 | 0.0486 | 0.141* | 0.623 (3) |
H10B | −0.0698 | 0.5403 | 0.0834 | 0.141* | 0.623 (3) |
H10C | −0.0960 | 0.4087 | 0.1489 | 0.141* | 0.623 (3) |
C11A | 0.1822 (12) | 0.4314 (15) | 0.2067 (4) | 0.090 (3) | 0.623 (3) |
H11A | 0.1194 | 0.4042 | 0.2445 | 0.134* | 0.623 (3) |
H11B | 0.1887 | 0.5457 | 0.2028 | 0.134* | 0.623 (3) |
H11C | 0.2773 | 0.3878 | 0.2296 | 0.134* | 0.623 (3) |
S2 | 0.0882 (3) | 0.3056 (2) | 0.16041 (16) | 0.0790 (9) | 0.377 (3) |
O4B | 0.1240 (9) | 0.2208 (9) | 0.0847 (6) | 0.068 (2) | 0.377 (3) |
C10B | −0.0549 (15) | 0.416 (2) | 0.0918 (8) | 0.102 (7) | 0.377 (3) |
H10D | −0.1371 | 0.4211 | 0.1180 | 0.153* | 0.377 (3) |
H10E | −0.0828 | 0.3648 | 0.0362 | 0.153* | 0.377 (3) |
H10F | −0.0218 | 0.5230 | 0.0843 | 0.153* | 0.377 (3) |
C11B | 0.2192 (19) | 0.463 (2) | 0.1806 (10) | 0.076 (4) | 0.377 (3) |
H11D | 0.3141 | 0.4183 | 0.2030 | 0.114* | 0.377 (3) |
H11E | 0.1960 | 0.5358 | 0.2223 | 0.114* | 0.377 (3) |
H11F | 0.2180 | 0.5185 | 0.1273 | 0.114* | 0.377 (3) |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cu1 | 0.0412 (2) | 0.0386 (2) | 0.03110 (19) | 0.01296 (15) | 0.02150 (15) | 0.00751 (14) |
O1 | 0.0452 (9) | 0.0506 (9) | 0.0437 (8) | 0.0179 (7) | 0.0263 (7) | 0.0168 (7) |
O2 | 0.0476 (9) | 0.0450 (8) | 0.0411 (8) | 0.0077 (7) | 0.0208 (7) | 0.0158 (7) |
O3 | 0.0697 (12) | 0.0697 (12) | 0.0294 (8) | 0.0179 (9) | 0.0222 (8) | 0.0040 (7) |
N1 | 0.0362 (8) | 0.0338 (9) | 0.0274 (8) | 0.0029 (7) | 0.0116 (7) | −0.0019 (6) |
C1 | 0.0300 (9) | 0.0300 (9) | 0.0274 (9) | −0.0021 (7) | 0.0123 (7) | −0.0013 (7) |
C2 | 0.0391 (10) | 0.0393 (11) | 0.0301 (10) | −0.0002 (8) | 0.0157 (8) | −0.0050 (8) |
N2 | 0.0416 (10) | 0.0439 (10) | 0.0361 (9) | 0.0053 (8) | 0.0198 (8) | −0.0070 (8) |
C3 | 0.0335 (10) | 0.0332 (10) | 0.0382 (11) | −0.0004 (8) | 0.0115 (8) | −0.0043 (8) |
C4 | 0.0427 (12) | 0.0495 (13) | 0.0610 (15) | 0.0113 (10) | 0.0191 (11) | −0.0023 (12) |
C5 | 0.0390 (12) | 0.0493 (14) | 0.0710 (17) | 0.0114 (10) | 0.0051 (12) | 0.0070 (12) |
C6 | 0.0446 (13) | 0.0589 (15) | 0.0474 (13) | 0.0058 (11) | −0.0001 (10) | 0.0098 (12) |
C7 | 0.0442 (12) | 0.0549 (14) | 0.0358 (11) | 0.0058 (10) | 0.0087 (9) | 0.0028 (10) |
C8 | 0.0314 (9) | 0.0347 (10) | 0.0336 (10) | 0.0009 (8) | 0.0088 (8) | −0.0018 (8) |
C9 | 0.0329 (10) | 0.0339 (10) | 0.0316 (10) | −0.0006 (8) | 0.0119 (8) | 0.0025 (8) |
S1 | 0.0504 (6) | 0.0465 (6) | 0.0541 (7) | −0.0003 (4) | 0.0152 (5) | −0.0048 (5) |
O4A | 0.074 (3) | 0.037 (2) | 0.058 (2) | 0.0012 (17) | 0.0156 (18) | −0.0014 (15) |
C10A | 0.025 (2) | 0.050 (4) | 0.207 (11) | 0.005 (2) | 0.028 (4) | −0.033 (5) |
C11A | 0.086 (7) | 0.087 (6) | 0.074 (5) | 0.026 (4) | −0.027 (4) | −0.036 (5) |
S2 | 0.140 (2) | 0.0448 (11) | 0.0718 (15) | 0.0067 (11) | 0.0638 (15) | 0.0058 (9) |
O4B | 0.076 (4) | 0.048 (4) | 0.095 (6) | −0.011 (3) | 0.048 (4) | −0.034 (4) |
C10B | 0.151 (15) | 0.092 (12) | 0.055 (6) | −0.025 (10) | 0.006 (8) | −0.010 (7) |
C11B | 0.074 (8) | 0.065 (8) | 0.081 (7) | 0.018 (5) | 0.005 (6) | −0.025 (7) |
Geometric parameters (Å, º) top
Cu1—O1 | 1.9116 (14) | C6—H6 | 0.9300 |
Cu1—N1 | 2.1191 (16) | C7—C8 | 1.401 (3) |
Cu1—O4A | 2.336 (5) | C7—H7 | 0.9300 |
Cu1—O4B | 2.418 (7) | S1—O4A | 1.514 (4) |
O1—C9 | 1.280 (2) | S1—C11A | 1.782 (2) |
O2—C9 | 1.217 (2) | S1—C10A | 1.786 (2) |
O3—C2 | 1.220 (3) | C10A—H10A | 0.9600 |
N1—C1 | 1.297 (2) | C10A—H10B | 0.9600 |
N1—C8 | 1.386 (3) | C10A—H10C | 0.9600 |
C1—C2 | 1.486 (3) | C11A—H11A | 0.9600 |
C1—C9 | 1.514 (3) | C11A—H11B | 0.9600 |
C2—N2 | 1.360 (3) | C11A—H11C | 0.9600 |
N2—C3 | 1.372 (3) | S2—O4B | 1.494 (7) |
N2—H1N2 | 0.76 (3) | S2—C11B | 1.782 (2) |
C3—C4 | 1.396 (3) | S2—C10B | 1.786 (2) |
C3—C8 | 1.400 (3) | C10B—H10D | 0.9600 |
C4—C5 | 1.366 (4) | C10B—H10E | 0.9600 |
C4—H4 | 0.9300 | C10B—H10F | 0.9600 |
C5—C6 | 1.390 (4) | C11B—H11D | 0.9600 |
C5—H5 | 0.9300 | C11B—H11E | 0.9600 |
C6—C7 | 1.371 (3) | C11B—H11F | 0.9600 |
| | | |
O1—Cu1—N1 | 80.74 (6) | C7—C6—C5 | 120.3 (2) |
O1i—Cu1—N1 | 99.26 (6) | C7—C6—H6 | 119.8 |
O1—Cu1—O4A | 81.46 (11) | C5—C6—H6 | 119.8 |
O1i—Cu1—O4A | 98.54 (11) | C6—C7—C8 | 119.5 (2) |
N1—Cu1—O4A | 83.58 (12) | C6—C7—H7 | 120.2 |
N1i—Cu1—O4A | 96.42 (12) | C8—C7—H7 | 120.2 |
O1—Cu1—O4Bi | 84.1 (2) | N1—C8—C3 | 119.55 (18) |
N1—Cu1—O4Bi | 86.18 (17) | N1—C8—C7 | 120.59 (18) |
O4A—Cu1—O4Bi | 163.43 (17) | C3—C8—C7 | 119.86 (19) |
O1—Cu1—O4B | 95.9 (2) | O2—C9—O1 | 124.31 (19) |
N1—Cu1—O4B | 93.82 (17) | O2—C9—C1 | 121.15 (17) |
C9—O1—Cu1 | 116.63 (13) | O1—C9—C1 | 114.44 (16) |
C1—N1—C8 | 120.52 (17) | O4A—S1—C11A | 105.4 (5) |
C1—N1—Cu1 | 106.93 (12) | O4A—S1—C10A | 106.6 (4) |
C8—N1—Cu1 | 129.92 (13) | C11A—S1—C10A | 94.1 (6) |
N1—C1—C2 | 123.08 (17) | S1—O4A—Cu1 | 121.7 (2) |
N1—C1—C9 | 115.37 (16) | O4B—S2—C11B | 102.6 (6) |
C2—C1—C9 | 121.54 (17) | O4B—S2—C10B | 92.2 (6) |
O3—C2—N2 | 122.62 (19) | C11B—S2—C10B | 97.1 (10) |
O3—C2—C1 | 124.31 (19) | S2—O4B—Cu1 | 129.4 (4) |
N2—C2—C1 | 112.94 (18) | S2—C10B—H10D | 109.5 |
C2—N2—C3 | 125.05 (18) | S2—C10B—H10E | 109.5 |
C2—N2—H1N2 | 118 (2) | H10D—C10B—H10E | 109.5 |
C3—N2—H1N2 | 117 (2) | S2—C10B—H10F | 109.5 |
N2—C3—C4 | 122.3 (2) | H10D—C10B—H10F | 109.5 |
N2—C3—C8 | 118.14 (18) | H10E—C10B—H10F | 109.5 |
C4—C3—C8 | 119.6 (2) | S2—C11B—H11D | 109.5 |
C5—C4—C3 | 119.7 (2) | S2—C11B—H11E | 109.5 |
C5—C4—H4 | 120.2 | H11D—C11B—H11E | 109.5 |
C3—C4—H4 | 120.2 | S2—C11B—H11F | 109.5 |
C4—C5—C6 | 121.0 (2) | H11D—C11B—H11F | 109.5 |
C4—C5—H5 | 119.5 | H11E—C11B—H11F | 109.5 |
C6—C5—H5 | 119.5 | | |
| | | |
N1—Cu1—O1—C9 | −14.91 (15) | C5—C6—C7—C8 | −0.1 (4) |
N1i—Cu1—O1—C9 | 165.09 (15) | C1—N1—C8—C3 | 7.5 (3) |
O4A—Cu1—O1—C9 | 69.92 (19) | Cu1—N1—C8—C3 | −151.60 (15) |
O4Ai—Cu1—O1—C9 | −110.08 (19) | C1—N1—C8—C7 | −172.10 (19) |
O4Bi—Cu1—O1—C9 | −102.0 (2) | Cu1—N1—C8—C7 | 28.8 (3) |
O4B—Cu1—O1—C9 | 78.0 (2) | N2—C3—C8—N1 | −0.2 (3) |
O1—Cu1—N1—C1 | 21.50 (13) | C4—C3—C8—N1 | 179.6 (2) |
O1i—Cu1—N1—C1 | −158.50 (13) | N2—C3—C8—C7 | 179.4 (2) |
O4A—Cu1—N1—C1 | −60.86 (15) | C4—C3—C8—C7 | −0.9 (3) |
O4Ai—Cu1—N1—C1 | 119.14 (15) | C6—C7—C8—N1 | −179.8 (2) |
O4Bi—Cu1—N1—C1 | 106.1 (2) | C6—C7—C8—C3 | 0.6 (3) |
O4B—Cu1—N1—C1 | −73.9 (2) | Cu1—O1—C9—O2 | −177.43 (17) |
O1—Cu1—N1—C8 | −177.26 (18) | Cu1—O1—C9—C1 | 6.1 (2) |
O1i—Cu1—N1—C8 | 2.74 (18) | N1—C1—C9—O2 | −162.31 (19) |
O4A—Cu1—N1—C8 | 100.38 (19) | C2—C1—C9—O2 | 19.1 (3) |
O4Ai—Cu1—N1—C8 | −79.62 (19) | N1—C1—C9—O1 | 14.3 (3) |
O4Bi—Cu1—N1—C8 | −92.7 (3) | C2—C1—C9—O1 | −164.37 (18) |
O4B—Cu1—N1—C8 | 87.3 (3) | C11A—S1—O4A—Cu1 | 175.7 (4) |
C8—N1—C1—C2 | −8.9 (3) | C10A—S1—O4A—Cu1 | 76.5 (5) |
Cu1—N1—C1—C2 | 154.46 (15) | O1—Cu1—O4A—S1 | −177.9 (3) |
C8—N1—C1—C9 | 172.49 (17) | O1i—Cu1—O4A—S1 | 2.1 (3) |
Cu1—N1—C1—C9 | −24.15 (19) | N1—Cu1—O4A—S1 | −96.4 (3) |
N1—C1—C2—O3 | −173.1 (2) | N1i—Cu1—O4A—S1 | 83.6 (3) |
C9—C1—C2—O3 | 5.5 (3) | O4Bi—Cu1—O4A—S1 | −148.6 (8) |
N1—C1—C2—N2 | 2.9 (3) | O4B—Cu1—O4A—S1 | 31.4 (8) |
C9—C1—C2—N2 | −178.61 (17) | C11B—S2—O4B—Cu1 | −175.3 (9) |
O3—C2—N2—C3 | −179.2 (2) | C10B—S2—O4B—Cu1 | −77.4 (9) |
C1—C2—N2—C3 | 4.8 (3) | O1—Cu1—O4B—S2 | −67.3 (7) |
C2—N2—C3—C4 | 174.1 (2) | O1i—Cu1—O4B—S2 | 112.7 (7) |
C2—N2—C3—C8 | −6.1 (3) | N1—Cu1—O4B—S2 | 13.8 (7) |
N2—C3—C4—C5 | −179.8 (2) | N1i—Cu1—O4B—S2 | −166.2 (7) |
C8—C3—C4—C5 | 0.5 (3) | O4A—Cu1—O4B—S2 | −38.1 (6) |
C3—C4—C5—C6 | 0.1 (4) | O4Ai—Cu1—O4B—S2 | 141.9 (6) |
C4—C5—C6—C7 | −0.3 (4) | | |
Symmetry code: (i) −x, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H1N2···O2ii | 0.76 (3) | 2.08 (3) | 2.838 (2) | 176 (3) |
C7—H7···O1i | 0.93 | 2.43 | 3.065 (3) | 125 |
C11A—H11C···O2iii | 0.96 | 2.43 | 3.392 (11) | 177 |
Symmetry codes: (i) −x, −y, −z; (ii) −x−1/2, y+1/2, −z+1/2; (iii) −x+1/2, y+1/2, −z+1/2. |
Experimental details
Crystal data |
Chemical formula | [Cu(C9H5N2O3)2(C2H6OS)2] |
Mr | 598.13 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 296 |
a, b, c (Å) | 9.4426 (1), 8.3584 (1), 15.7881 (3) |
β (°) | 103.213 (2) |
V (Å3) | 1213.09 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 1.13 |
Crystal size (mm) | 0.43 × 0.43 × 0.10 |
|
Data collection |
Diffractometer | Oxford Xcalibur2 diffractometer with a Sapphire-3 CCD area-detector |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2006) |
Tmin, Tmax | 0.810, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 15817, 2625, 2280 |
Rint | 0.021 |
(sin θ/λ)max (Å−1) | 0.639 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.035, 0.087, 1.11 |
No. of reflections | 2624 |
No. of parameters | 214 |
No. of restraints | 4 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.39, −0.31 |
Selected geometric parameters (Å, º) topCu1—O1 | 1.9116 (14) | N2—C3 | 1.372 (3) |
Cu1—N1 | 2.1191 (16) | S1—O4A | 1.514 (4) |
Cu1—O4A | 2.336 (5) | S1—C11A | 1.782 (2) |
Cu1—O4B | 2.418 (7) | S1—C10A | 1.786 (2) |
O1—C9 | 1.280 (2) | S2—O4B | 1.494 (7) |
O2—C9 | 1.217 (2) | S2—C11B | 1.782 (2) |
O3—C2 | 1.220 (3) | S2—C10B | 1.786 (2) |
C2—N2 | 1.360 (3) | | |
| | | |
O1—Cu1—N1 | 80.74 (6) | N1i—Cu1—O4A | 96.42 (12) |
O1i—Cu1—N1 | 99.26 (6) | O1—Cu1—O4Bi | 84.1 (2) |
O1—Cu1—O4A | 81.46 (11) | N1—Cu1—O4Bi | 86.18 (17) |
O1i—Cu1—O4A | 98.54 (11) | O1—Cu1—O4B | 95.9 (2) |
N1—Cu1—O4A | 83.58 (12) | N1—Cu1—O4B | 93.82 (17) |
Symmetry code: (i) −x, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H1N2···O2ii | 0.76 (3) | 2.08 (3) | 2.838 (2) | 176 (3) |
C7—H7···O1i | 0.93 | 2.434 | 3.065 (3) | 125 |
C11A—H11C···O2iii | 0.96 | 2.433 | 3.392 (11) | 177 |
Symmetry codes: (i) −x, −y, −z; (ii) −x−1/2, y+1/2, −z+1/2; (iii) −x+1/2, y+1/2, −z+1/2. |
Kynurenic acid (4-hydroxy-2-quinolinecarboxylic acid), a well known tryptophane metabolite, has neuroactivity to inhibit excitatory amino acid (EAA) receptor-mediated neurodegeneration (Jauch et al., 1993; Stone, 1993). 3-Hydroxy-2-quinoxalinecarboxylic acid (HQC), a substance which is structurally related to kynurenic acid, shows similar effects on EAA receptors. However, the above-mentioned properties of HQC exhibit some ambiguities and side effects. Therefore, it is of interest to a obtain deeper insight into the structure–function relationship, not only of the acid alone, but of its metal complexes, particularly those with metals of pharmacological importance, such as copper (Krogsgaard-Larsen et al., 2002). To the best of our knowledge, the only metal complex of HQC known so far is a nickel(II) complex of formula Ni(HQC)Cl2 (Turvey & Allan, 1996), characterized by spectroscopic, magnetic and conductivity measurements and by thermal methods. In this study, the structure of the title copper complex with HQC, (I), has been determined.
Compound (I) contains a CuII ion on a crystallographic inversion centre. The CuII ion is octahedrally coordinated by two 3-hydroxy-4-quinoxalinium-2-carboxylato-N,O ligands in the equatorial plane [Cu1—O1 1.9116 (14) Å and Cu1—N1 2.1191 (16) Å] and by two disordered dimethyl sulfoxide (DMSO) molecules in the apical positions [Cu1—O4A = 2.336 (5) Å and Cu1—O4B = 2.418 (7) Å] (Table 1, Fig. 1). The bond angles around atom Cu1 lie within the range 80–100°, with the largest angle being O1i—Cu1—N1 = 99.26 (6)° [symmetry code: (i) -x, -y, -z]. The Cu1—O1 bond is shorter than other chemically similar Cu—O bond distances (1.94–1.98 Å; References?), e.g. in the mixed-valence CuI/CuII complex with pyrazine-2-carboxylic acid [1.941 (3) Å; Liu et al., 2003]. On the other hand, Cu1—N1 is longer than analogous Cu—N bonds (1.98–2.00 Å) found in the copper(II) complex with picolinic acid (Segl'a et al., 1998) and in the two copper(II) complexes with pyrazine-2-carboxylic acid (Klein et al., 1982; Ptasiewicz-Bąk et al., 1995). It is even slightly longer than the analogous bond of 2.061 (3) Å in the coordination polymer of copper(II) with pyrazine-2,3-dicarboxylic acid (Konar et al., 2004), which is the longest found to date in the literature for copper(II) complexes containing carboxylic acid with pyrazine and/or a pyridine ring. [Two paragraphs have been merged to avoid repetition. Please check that the meaning is not affected]
The chelate ring defined by atoms Cu1/O1/C9/C1/N1 is approximately planar, with a maximum deviation out of plane of 0.11 Å for Cu1. This plane makes a significantly large angle of 20.84 (7)° with the planar quinoxaline ring (atoms N1/C1/C2/N2/C3–C8). The geometry of the quinoxaline ring corresponds to tautomeric protonation at N2 [O3═C2 = 1.220 (3) Å and C2—N2 = 1.360 (3) Å] (Allen, 2002).
The O1—C9 bond distance of the carboxylate group [1.280 (2) Å] is longer than O2—C9 [1.217 (2) Å], due to the coordination of atom O1 to CuII. This deviation of carboxylate group geometry is well known, with the longer C—O bond being in the range 1.28–1.30 Å and the shorter one in the range 1.22–1.24 Å (Segl'a et al., 1998; Klein et al., 1982; Ptasiewicz-Bąk et al., 1995; Konar et al., 2004).
The Cu1—O4A and Cu1—O4B bond distances (from DMSO) (Table 1) in (I) fall within the range 2.34–2.46 Å (Cu1—O4A is slightly shorter) found for octahedral copper(II) complexes containing DMSO in axial positions (Benali-Cherif et al., 1995; Bieller et al., 2005; Djedouani et al.,2006; Chan et al.,1996). The longest Cu—O(DMSO) bond distance in the previously reported complexes is 2.463 Å in bis[3-acetyl-6-methyl-2H-pyran-2,4(3H)-dionato]bis(dimethylsulfoxide)copper(II) (Djedouani et al., 2006), reflecting Jahn–Teller distortion. The Cu1—O4A bond (from the major DMSO component) in (I) differs slightly from the corresponding bond in hexakis(dimethylsulfoxide)copper(II) bis(hydrogensulfate) [2.34 (1) Å; Bieller et al., 2005] and from that observed in bis(2,4-diamino-6-(4-pyridyl)-1,3,5-triazine)bis(dimethylsulfoxide)copper(II) perchlorate [2.353 (9) Å; Chan et al., 1996]. In the latter compound, the S atom shows positional disorder in both DMSO ligands.
The complexes are linked by an intermolecular N—H···O hydrogen bond [2.838 (2) Å], formed between the quinoxaline N—H group and a carboxylate O atom, and by a weak intermolecular C—H···O hydrogen bond [3.392 (11) Å], which is formed between carboxylate O and methyl C atoms of a DMSO molecule. There is a weak intramolecular C—H···O hydrogen bond [3.065 (3) Å] formed between a phenyl C—H and the ligated carboxylate O donor atom (Table 2, Fig. 2).