Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106042624/sq3043sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106042624/sq3043Isup2.hkl |
CCDC reference: 632917
The ligand H2dmoxpn was prepared by using the reported method (Ojima & Yamada, 1970). An ethanol solution (5 ml) of copper(II) perchlorate hexahydrate (0.2 mmol, 0.0741 g) was added slowly to an ethanol solution (5 ml) containing H2dmoxpn (0.1 mmol, 0.0258 g) and piperidine (0.2 mmol, 0.017 g). The mixture was stirred quickly for 30 minutes, then a methanol solution (5 ml) of imidazole (0.2 mmol, 0.0136 g) was added dropwise to the mixture. The reaction solution was heated at 333 K with stirring for 6 h. The resulting solution was filtered and concentrated by slow evaporation at room temperature for several days, and then dark-blue crystals (yield 0.0477 g, 61%) of the compound suitable for X-ray analysis were obtained from the solution.
The hydroxy H atoms of the methanol molecules were located in a difference Fouier map and refined in a riding model (O—H = 0.98 Å) [Uiso treatment for this atom?]. The other H atoms were positioned geometrically, with an N—H distance of 0.86 Å and C—H distances of 0.93 Å (Csp2—H), 0.97 Å (CH2) and 0.96 Å (CH3), and were then treated as riding with Uiso(H) values of 1.2Ueq(C,N) and 1.5Ueq(methyl C).
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: WinGX (Farrugia, 1999).
[Cu2(C12H24N4O2)(C3H4N2)2(CH4O)2](ClO4)2 | F(000) = 808 |
Mr = 782.60 | Dx = 1.647 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 2584 reflections |
a = 10.023 (3) Å | θ = 2.6–27.8° |
b = 13.084 (3) Å | µ = 1.59 mm−1 |
c = 12.317 (3) Å | T = 298 K |
β = 102.328 (4)° | Block, dark blue |
V = 1578.0 (7) Å3 | 0.50 × 0.14 × 0.09 mm |
Z = 2 |
Bruker APEX area-detector diffractometer | 3121 independent reflections |
Radiation source: fine-focus sealed tube | 2201 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.042 |
ϕ and ω scans | θmax = 26.1°, θmin = 2.3° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −12→12 |
Tmin = 0.504, Tmax = 0.870 | k = −15→16 |
8761 measured reflections | l = −9→15 |
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)] = 0.045 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0512P)2 + 1.6075P] where P = (Fo2 + 2Fc2)/3 |
3121 reflections | (Δ/σ)max < 0.001 |
203 parameters | Δρmax = 0.54 e Å−3 |
0 restraints | Δρmin = −0.33 e Å−3 |
[Cu2(C12H24N4O2)(C3H4N2)2(CH4O)2](ClO4)2 | V = 1578.0 (7) Å3 |
Mr = 782.60 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.023 (3) Å | µ = 1.59 mm−1 |
b = 13.084 (3) Å | T = 298 K |
c = 12.317 (3) Å | 0.50 × 0.14 × 0.09 mm |
β = 102.328 (4)° |
Bruker APEX area-detector diffractometer | 3121 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 2201 reflections with I > 2σ(I) |
Tmin = 0.504, Tmax = 0.870 | Rint = 0.042 |
8761 measured reflections |
R[F2 > 2σ(F2)] = 0.045 | 0 restraints |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.54 e Å−3 |
3121 reflections | Δρmin = −0.33 e Å−3 |
203 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.2616 (6) | 0.3469 (4) | −0.0329 (5) | 0.0623 (14) | |
H1A | 0.2697 | 0.4193 | −0.0209 | 0.093* | |
H1B | 0.2044 | 0.3336 | −0.1045 | 0.093* | |
H1C | 0.3504 | 0.3180 | −0.0296 | 0.093* | |
C2 | 0.2874 (5) | 0.3248 (4) | 0.1634 (4) | 0.0590 (13) | |
H2A | 0.3799 | 0.3052 | 0.1643 | 0.089* | |
H2B | 0.2552 | 0.2882 | 0.2204 | 0.089* | |
H2C | 0.2836 | 0.3969 | 0.1767 | 0.089* | |
C3 | 0.0653 (5) | 0.3491 (3) | 0.0559 (5) | 0.0568 (13) | |
H3A | 0.0424 | 0.3341 | 0.1268 | 0.068* | |
H3B | 0.0757 | 0.4227 | 0.0516 | 0.068* | |
C4 | −0.0506 (5) | 0.3170 (4) | −0.0339 (5) | 0.0588 (14) | |
H4A | −0.0194 | 0.3140 | −0.1032 | 0.071* | |
H4B | −0.1214 | 0.3687 | −0.0422 | 0.071* | |
C5 | −0.1120 (4) | 0.2155 (3) | −0.0152 (4) | 0.0388 (10) | |
H5A | −0.1481 | 0.2187 | 0.0518 | 0.047* | |
H5B | −0.1871 | 0.2006 | −0.0771 | 0.047* | |
C6 | −0.0540 (3) | 0.0401 (3) | −0.0059 (3) | 0.0279 (8) | |
C7 | 0.1968 (6) | 0.1677 (5) | −0.2865 (5) | 0.0837 (19) | |
H7A | 0.1378 | 0.2249 | −0.3102 | 0.126* | |
H7B | 0.1777 | 0.1146 | −0.3414 | 0.126* | |
H7C | 0.2902 | 0.1888 | −0.2775 | 0.126* | |
C8 | 0.4833 (4) | 0.1298 (3) | 0.0125 (4) | 0.0410 (10) | |
H8 | 0.4697 | 0.1572 | −0.0587 | 0.049* | |
C9 | 0.5817 (4) | 0.0574 (4) | 0.1675 (4) | 0.0498 (12) | |
H9 | 0.6465 | 0.0264 | 0.2230 | 0.060* | |
C10 | 0.4510 (4) | 0.0777 (3) | 0.1705 (4) | 0.0438 (10) | |
H10 | 0.4094 | 0.0628 | 0.2292 | 0.053* | |
N1 | 0.2003 (3) | 0.3002 (3) | 0.0540 (3) | 0.0408 (9) | |
N2 | −0.0104 (3) | 0.1337 (2) | −0.0044 (3) | 0.0301 (7) | |
N3 | 0.3891 (3) | 0.1240 (2) | 0.0729 (3) | 0.0357 (8) | |
N4 | 0.6003 (3) | 0.0906 (3) | 0.0685 (3) | 0.0486 (10) | |
H4 | 0.6752 | 0.0872 | 0.0453 | 0.058* | |
O1 | −0.1776 (2) | 0.00981 (19) | −0.0161 (2) | 0.0338 (6) | |
O2 | 0.1744 (4) | 0.1308 (3) | −0.1849 (3) | 0.0718 (11) | |
H2 | 0.1020 | 0.0814 | −0.2122 | 0.09 (2)* | |
O3 | 0.1643 (4) | 0.0997 (3) | 0.2507 (3) | 0.0724 (11) | |
O4 | 0.0299 (5) | 0.2255 (3) | 0.3026 (4) | 0.0907 (13) | |
O5 | 0.0946 (5) | 0.0904 (4) | 0.4181 (3) | 0.1060 (16) | |
O6 | −0.0636 (4) | 0.0703 (4) | 0.2521 (4) | 0.1058 (16) | |
Cl1 | 0.05644 (11) | 0.12021 (8) | 0.30697 (9) | 0.0456 (3) | |
Cu1 | 0.18881 (4) | 0.14413 (3) | 0.02921 (4) | 0.03355 (17) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.075 (3) | 0.044 (3) | 0.076 (4) | −0.006 (2) | 0.034 (3) | 0.009 (3) |
C2 | 0.058 (3) | 0.048 (3) | 0.070 (4) | −0.007 (2) | 0.012 (3) | −0.009 (2) |
C3 | 0.047 (3) | 0.034 (2) | 0.090 (4) | 0.004 (2) | 0.017 (3) | −0.003 (2) |
C4 | 0.043 (3) | 0.038 (3) | 0.093 (4) | 0.005 (2) | 0.009 (3) | 0.010 (3) |
C5 | 0.026 (2) | 0.038 (2) | 0.053 (3) | 0.0053 (17) | 0.0111 (18) | −0.0005 (19) |
C6 | 0.0199 (17) | 0.034 (2) | 0.032 (2) | −0.0003 (15) | 0.0100 (15) | −0.0002 (16) |
C7 | 0.074 (4) | 0.082 (4) | 0.100 (5) | 0.008 (3) | 0.032 (3) | 0.040 (4) |
C8 | 0.034 (2) | 0.040 (2) | 0.055 (3) | −0.0084 (18) | 0.0224 (19) | −0.006 (2) |
C9 | 0.035 (2) | 0.057 (3) | 0.055 (3) | 0.010 (2) | 0.002 (2) | −0.009 (2) |
C10 | 0.037 (2) | 0.053 (3) | 0.043 (3) | 0.004 (2) | 0.0119 (19) | −0.007 (2) |
N1 | 0.0342 (18) | 0.0344 (19) | 0.056 (2) | −0.0044 (14) | 0.0143 (17) | 0.0009 (16) |
N2 | 0.0202 (14) | 0.0300 (17) | 0.0423 (19) | 0.0032 (12) | 0.0113 (13) | 0.0014 (14) |
N3 | 0.0217 (15) | 0.0376 (19) | 0.050 (2) | −0.0028 (13) | 0.0112 (14) | −0.0080 (16) |
N4 | 0.0227 (17) | 0.048 (2) | 0.079 (3) | −0.0054 (15) | 0.0206 (18) | −0.020 (2) |
O1 | 0.0204 (13) | 0.0320 (14) | 0.0509 (18) | −0.0022 (10) | 0.0122 (11) | −0.0019 (12) |
O2 | 0.084 (3) | 0.074 (3) | 0.064 (2) | −0.020 (2) | 0.031 (2) | −0.0002 (19) |
O3 | 0.057 (2) | 0.099 (3) | 0.071 (2) | 0.020 (2) | 0.0356 (18) | −0.002 (2) |
O4 | 0.111 (3) | 0.060 (2) | 0.118 (4) | 0.017 (2) | 0.063 (3) | −0.001 (2) |
O5 | 0.104 (3) | 0.157 (5) | 0.064 (3) | 0.043 (3) | 0.032 (2) | 0.038 (3) |
O6 | 0.071 (3) | 0.128 (4) | 0.123 (4) | −0.044 (3) | 0.030 (3) | −0.039 (3) |
Cl1 | 0.0407 (6) | 0.0505 (7) | 0.0487 (7) | 0.0033 (5) | 0.0160 (5) | 0.0001 (5) |
Cu1 | 0.0206 (2) | 0.0305 (3) | 0.0514 (3) | −0.00154 (19) | 0.01192 (19) | −0.0026 (2) |
Cu1—N1 | 2.064 (3) | C6—N2 | 1.299 (5) |
Cu1—N2 | 1.955 (3) | C6—O1 | 1.282 (4) |
Cu1—N3 | 1.982 (3) | C6—C6i | 1.492 (7) |
Cu1—O1i | 2.022 (3) | C7—O2 | 1.403 (7) |
C1—N1 | 1.475 (6) | C7—H7A | 0.9600 |
C1—H1A | 0.9600 | C7—H7B | 0.9600 |
C1—H1B | 0.9600 | C7—H7C | 0.9600 |
C1—H1C | 0.9600 | C8—N3 | 1.323 (5) |
C2—N1 | 1.477 (6) | C8—N4 | 1.329 (5) |
C2—H2A | 0.9600 | C8—H8 | 0.9300 |
C2—H2B | 0.9600 | C9—C10 | 1.344 (6) |
C2—H2C | 0.9600 | C9—N4 | 1.345 (6) |
C3—C4 | 1.484 (7) | C9—H9 | 0.9300 |
C3—N1 | 1.501 (5) | C10—N3 | 1.371 (5) |
C3—H3A | 0.9700 | C10—H10 | 0.9300 |
C3—H3B | 0.9700 | N4—H4 | 0.8600 |
C4—C5 | 1.502 (6) | O2—H2 | 0.9767 |
C4—H4A | 0.9700 | O3—Cl1 | 1.429 (3) |
C4—H4B | 0.9700 | O4—Cl1 | 1.402 (4) |
C5—N2 | 1.463 (5) | O5—Cl1 | 1.396 (4) |
C5—H5A | 0.9700 | O6—Cl1 | 1.408 (4) |
C5—H5B | 0.9700 | ||
N1—Cu1—N2 | 97.01 (12) | C3—C4—C5 | 114.7 (4) |
N1—Cu1—N3 | 94.04 (13) | C3—C4—H4A | 108.6 |
N1—Cu1—O1i | 176.09 (13) | C3—C4—H4B | 108.6 |
N2—Cu1—N3 | 167.84 (13) | C5—C4—H4A | 108.6 |
N2—Cu1—O1i | 82.95 (11) | C5—C4—H4B | 108.6 |
N3—Cu1—O1i | 85.68 (11) | H4A—C4—H4B | 107.6 |
C1—N1—C2 | 108.4 (4) | N2—C5—C4 | 111.1 (3) |
C1—N1—C3 | 110.5 (4) | N2—C5—H5A | 109.4 |
C1—N1—Cu1 | 108.7 (3) | N2—C5—H5B | 109.4 |
C2—N1—C3 | 104.5 (4) | C4—C5—H5A | 109.4 |
C2—N1—Cu1 | 110.7 (3) | C4—C5—H5B | 109.4 |
C3—N1—Cu1 | 113.8 (2) | H5A—C5—H5B | 108.0 |
C5—N2—C6 | 117.6 (3) | N2—C6—C6i | 115.3 (4) |
C5—N2—Cu1 | 128.9 (2) | N2—C6—O1 | 127.4 (3) |
C6—N2—Cu1 | 113.2 (2) | O1—C6—C6i | 117.2 (4) |
C8—N3—C10 | 105.9 (3) | O2—C7—H7A | 109.5 |
C8—N3—Cu1 | 130.0 (3) | O2—C7—H7B | 109.5 |
C10—N3—Cu1 | 122.6 (3) | O2—C7—H7C | 109.5 |
C8—N4—C9 | 108.5 (3) | H7A—C7—H7B | 109.5 |
C8—N4—H4 | 125.7 | H7A—C7—H7C | 109.5 |
C9—N4—H4 | 125.7 | H7B—C7—H7C | 109.5 |
N1—C1—H1A | 109.5 | N3—C8—N4 | 110.0 (4) |
N1—C1—H1B | 109.5 | N3—C8—H8 | 125.0 |
N1—C1—H1C | 109.5 | N4—C8—H8 | 125.0 |
H1A—C1—H1B | 109.5 | N4—C9—C10 | 106.6 (4) |
H1A—C1—H1C | 109.5 | N4—C9—H9 | 126.7 |
H1B—C1—H1C | 109.5 | C10—C9—H9 | 126.7 |
N1—C2—H2A | 109.5 | N3—C10—C9 | 108.9 (4) |
N1—C2—H2B | 109.5 | N3—C10—H10 | 125.5 |
N1—C2—H2C | 109.5 | C9—C10—H10 | 125.5 |
H2A—C2—H2B | 109.5 | C6—O1—Cu1i | 110.6 (2) |
H2A—C2—H2C | 109.5 | C7—O2—H2 | 99.8 |
H2B—C2—H2C | 109.5 | O3—Cl1—O4 | 108.9 (2) |
N1—C3—H3A | 108.4 | O3—Cl1—O5 | 110.2 (2) |
N1—C3—H3B | 108.4 | O3—Cl1—O6 | 109.7 (3) |
N1—C3—C4 | 115.6 (4) | O4—Cl1—O5 | 108.8 (3) |
C4—C3—H3A | 108.4 | O4—Cl1—O6 | 107.5 (3) |
C4—C3—H3B | 108.4 | O5—Cl1—O6 | 111.6 (3) |
H3A—C3—H3B | 107.5 | ||
N1—C3—C4—C5 | 79.1 (6) | C6i—C6—O1—Cu1i | −6.0 (5) |
C3—C4—C5—N2 | −59.5 (6) | C6—N2—Cu1—N3 | −13.5 (8) |
N3—C8—N4—C9 | 0.7 (5) | C5—N2—Cu1—N3 | 159.2 (6) |
C8—N4—C9—C10 | −0.3 (5) | C6—N2—Cu1—O1i | 7.4 (3) |
N4—C9—C10—N3 | −0.2 (5) | C5—N2—Cu1—O1i | −180.0 (3) |
C4—C3—N1—C1 | 76.8 (5) | C6—N2—Cu1—N1 | −168.7 (3) |
C4—C3—N1—C2 | −166.8 (4) | C5—N2—Cu1—N1 | 4.0 (3) |
C4—C3—N1—Cu1 | −45.9 (5) | C8—N3—Cu1—N2 | 117.9 (7) |
O1—C6—N2—C5 | 0.2 (6) | C10—N3—Cu1—N2 | −46.6 (8) |
C6i—C6—N2—C5 | −179.8 (4) | C8—N3—Cu1—O1i | 97.1 (3) |
O1—C6—N2—Cu1 | 173.7 (3) | C10—N3—Cu1—O1i | −67.4 (3) |
C6i—C6—N2—Cu1 | −6.3 (5) | C8—N3—Cu1—N1 | −86.8 (3) |
C4—C5—N2—C6 | −169.1 (4) | C10—N3—Cu1—N1 | 108.7 (3) |
C4—C5—N2—Cu1 | 18.5 (5) | C1—N1—Cu1—N2 | −115.2 (3) |
N4—C8—N3—C10 | −0.8 (4) | C2—N1—Cu1—N2 | 125.8 (3) |
N4—C8—N3—Cu1 | −167.3 (3) | C3—N1—Cu1—N2 | 8.4 (3) |
C9—C10—N3—C8 | 0.6 (5) | C1—N1—Cu1—N3 | 69.8 (3) |
C9—C10—N3—Cu1 | 168.3 (3) | C2—N1—Cu1—N3 | −49.1 (3) |
N2—C6—O1—Cu1i | 174.0 (3) | C3—N1—Cu1—N3 | −166.5 (3) |
Symmetry code: (i) −x, −y, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O6i | 0.98 | 2.06 | 2.907 (6) | 144 |
N4—H4···O1ii | 0.86 | 2.06 | 2.855 (4) | 153 |
C8—H8···O4iii | 0.93 | 2.47 | 3.317 (6) | 152 |
Symmetry codes: (i) −x, −y, −z; (ii) x+1, y, z; (iii) x+1/2, −y+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | [Cu2(C12H24N4O2)(C3H4N2)2(CH4O)2](ClO4)2 |
Mr | 782.60 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 298 |
a, b, c (Å) | 10.023 (3), 13.084 (3), 12.317 (3) |
β (°) | 102.328 (4) |
V (Å3) | 1578.0 (7) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 1.59 |
Crystal size (mm) | 0.50 × 0.14 × 0.09 |
Data collection | |
Diffractometer | Bruker APEX area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.504, 0.870 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8761, 3121, 2201 |
Rint | 0.042 |
(sin θ/λ)max (Å−1) | 0.620 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.117, 1.04 |
No. of reflections | 3121 |
No. of parameters | 203 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.54, −0.33 |
Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1994), WinGX (Farrugia, 1999).
Cu1—N1 | 2.064 (3) | C5—N2 | 1.463 (5) |
Cu1—N2 | 1.955 (3) | C6—N2 | 1.299 (5) |
Cu1—N3 | 1.982 (3) | C6—O1 | 1.282 (4) |
Cu1—O1i | 2.022 (3) | C6—C6i | 1.492 (7) |
N1—Cu1—N2 | 97.01 (12) | N3—Cu1—O1i | 85.68 (11) |
N1—Cu1—N3 | 94.04 (13) | C5—N2—C6 | 117.6 (3) |
N1—Cu1—O1i | 176.09 (13) | C5—N2—Cu1 | 128.9 (2) |
N2—Cu1—N3 | 167.84 (13) | C6—N2—Cu1 | 113.2 (2) |
N2—Cu1—O1i | 82.95 (11) | C6—O1—Cu1i | 110.6 (2) |
Symmetry code: (i) −x, −y, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O6i | 0.98 | 2.06 | 2.907 (6) | 143.8 |
N4—H4···O1ii | 0.86 | 2.06 | 2.855 (4) | 153.1 |
C8—H8···O4iii | 0.93 | 2.47 | 3.317 (6) | 152.3 |
Symmetry codes: (i) −x, −y, −z; (ii) x+1, y, z; (iii) x+1/2, −y+1/2, z−1/2. |
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Many studies have been devoted to the development of synthetic strategies for the architecture of coordination metal supramolecules (Hoskins & Robson, 1990; Black et al., 1996; Funeriu et al., 1997). A successful strategy leading to three-dimensional supramolecular systems is to utilize the π–π stacking of aromatic groups and/or the hydrogen bonding of coordinated ligands in addition to their coordination capability to interlink zero-, one- or two-dimensional coordination molecules (Chen et al., 1998; Yi et al., 2004). As is well known, N,N'-disubstituted oxamidate has proven to give rise to three-dimensional supramolecular structures because of the easy cis–trans conformational change, the flexible binding mode, and the ability to form hydrogen bonds (Chen et al., 1998). On the other hand, imidazole is a suitable ligand in the construction of supramolecular frameworks owing to the strong tendency to form π–π stacking and hydrogen bonds (Chen et al., 1994; Zhang et al., 1999). To our knowledge, only three crystal structures of oxamidate-bridged binuclear metal complexes containing an imidazole ligand have been characterized, viz. Cu2(oxpn)(HIm)2(NO3)2, A (Zhang et al., 1999), [Cu2(oxpn)(HIm)2(H2O)2](ClO4)2, B (Chen et al., 1994), and Cu2(oxen)(HIm)2, C (Li et al., 2004), where oxpn is deprotonated N,N'-bis(3-aminopropyl)oxamide and oxen is deprotonated N,N'-bis(3-aminoethyl)oxamide. However, the hydrogen bonds in these complexes were not discussed in detail and the π–π stacking of the imidazole groups was not studied at all. In order to obtain more information on supramolecular architecture constructed by hydrogen bonds and π-π stacking interactions in this kind of complex, we chose N,N'-bis[3-(dimethylamino)propyl]oxamide (H2dmoxpn) as the bridging ligand and imidazole as a terminal ligand to synthesize a binuclear copper(II) complex formulated as Cu2(dmoxpn)(HIm)2(CH3OH)2(ClO4)2 (I).
The molecular structure of (I), as shown in Fig. 1, consists of centrosymmetric dinuclear copper(II) cations bridged by dmoxpn2− anions, each CuII atom coordinating two imidazole and two methanol molecules, and two perchlorate counter-anions. The Cu···Cu separation through the oxamido bridge is 5.2824 (13) Å. The cation has a transoid conformation and occupies a special inversion center at the middle of the C6—C6i bond [symmetry code: (i) −x, −y, −z] which is the same as in the other three examples of oxamide complexes A–C. In contrast to the ligands oxpn and oxen, the dmoxpn ligand can only adopt a trans conformation when it coordinates to metal ions owing to the steric hindrance induced by the presence of methyl substituents on the amine groups (Ruiz et al., 1999; Lloret et al., 1992). The coordination environment of the copper(II) atom in (I) is a square pyramid, with the coordinated methanol molecule and perchlorate ion in axial sites to form a [4 + 2] quasi-octahedral geometry. The CuII atom is displaced 0.0751 (17) Å out of the basal plane. The axial Cu···O distances of 2.616 (4) Å (Cu1—O2) and 2.851 (4) Å (Cu1···O3) are significantly longer than those in the equatorial plane (Table 1). The imidazole ring is nearly perpendicular to the coordination plane, with a dihedral angle of 75.67 (14)°, which is very similar to the value of 78.6° in compound B with the same [4 + 2] quasi-octahedral coordination geometry, whereas with a much elongated [4 + 1] square–pyramidal geometry, approximately parallel angles of 15.30° and 27° are found in compounds A and C, respectively.
The bis-tridentate dmoxpn ligand produces five- and six-membered chelate rings. The bite angles are 82.95 (11) and 97.01 (12)°, respectively. The five-membered ring has an envelope conformation, while the six-membered ring is intermediate between half-boat and twist-boat conformations; the corresponding puckering parameters (Cremer & Pople, 1975) are ϕ = 180 (2)°, Q = 0.096 (3) Å and θ = 121.5 (4)°, and ϕ = 341.4 (5)° and Q = 0.550 (5) Å, respectively. The oxamide bridge is planar within experimental uncertainties. The dihedral angle between the oxamide bridge and the coordination plane is 10.48 (6)°. The C6—N2 and C6—C6i distances of 1.299 (5) and 1.492 (7) Å are typical C═N and Csp2—Csp2 values, respectively. Given that the C6—O1 distance of 1.282 (4) Å is in accordance with those of (Oδb)C—O− fragments in many examples (Delgado et al., 2006; Berg et al., 2002; Nash & Schaefer, 1969), the oxamido is best described as N═C—O− rather than delocalized.
The perchlorate anions stabilize the crystal structure by hydrogen bonds with methanol and HIm ligands (Table 2). As illustrated in Fig. 2, the perchlorate anions bridge the dinuclear copper(II) cationic complexes to form a two-dimensional hydrogen-bonding network parallel to the (101) crystal plane. Owing to the substitution of the H atoms of the primary amine of oxpn by methyl groups, the dmoxpn ligand does not participate in any hydrogen bonding, which is different from the oxpn or oxen in compounds A–C. By contrast, the HIm ligand contributes to not only the hydrogen bonds but also the π–π stacking interactions. Along the a axial direction, the complexes are assembled by N4—H4···O1ii hydrogen bonds [symmetry code: (ii) 1 + x, y, z] and the stacking between the aromatic rings of HIm and HImvi [symmetry code: (vi) 1 − x, −y, −z] (Fig. 3). The nearest separation is 3.092 (6) Å (C8···C8vi). This parallel edge-edge π–π stacking is also found in compounds A (3.282 Å) and B (3.097 Å). The separations of A and B were calculated according to the data in the Cambridge Structural Database (Allen, 2002).