The crystal structure of the title basic copper(II) sulfate, {(C5H7N2)[Cu2(OH)(SO4)2(H2O)2]}n, shows an unprecedented structural arrangement of two distinct copper centres. CuO6 and CuO5 polyhedra are linked through bridging hydroxide and sulfate anions to form negatively charged infinite chains propagated along the a axis. The negative charge is balanced by 3-aminopyridinium cations that are held in the structure by extensive hydrogen bonding to the inorganic chains. Additionally, the cationic arrangement features π–π stacking.
Supporting information
CCDC reference: 649077
CuSO4·5H2O (0.10 g, 0.4 mmol) and suberic acid (0.07 g, 0.4 mmol) were
combined in water (15 ml). The mixture was stirred and heated to boiling. The
addition of 3-aminopyridine (0.19 g, 2.0 mmol) resulted in a green solution.
Upon cooling to room temperature, a turquoise precipitate of unknown
composition was formed. On standing at ambient temperature, orange–green
single crystals of (I) appeared within three weeks. The crystals are extremely
sensitive and decompose rapidly when taken from the solution.
Aromatic H atoms and amino group H atoms of the 3-apyH cation were placed in
geometrically calculated positions and refined using a riding model, with
C—H = 0.93 Å and N—H = 0.86 Å, and with Uiso(H) =
1.2Ueq(C,N) [Please check added text]. All other H
atoms were found in a difference Fourier map and were refined freely, with
O—H distances ranging from 0.71 (3) [0.67 (3) is lowest value in CIF]
to 0.81 (3) Å and an N—H distance of 0.76 (3) Å.
Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO AND SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PLATON (Spek, 2003).
poly[3-aminopyridinium
µ
3-hydroxido-di-µ
3-sulfato-bis[aquasulfatocopper(II)]]
top
Crystal data top
(C5H7N2)[Cu2(OH)(SO4)2(H2O)2] | F(000) = 936 |
Mr = 467.41 | Dx = 2.366 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 3076 reflections |
a = 7.4094 (2) Å | θ = 1.0–27.5° |
b = 12.6262 (5) Å | µ = 3.62 mm−1 |
c = 14.0648 (5) Å | T = 150 K |
β = 94.260 (1)° | Prismatic, orange green |
V = 1312.16 (8) Å3 | 0.12 × 0.12 × 0.10 mm |
Z = 4 | |
Data collection top
Nonius KappaCCD area-detector diffractometer | 2897 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.011 |
Graphite monochromator | θmax = 27.5°, θmin = 3.2° |
ω scans | h = −9→9 |
5582 measured reflections | k = −16→16 |
2976 independent reflections | l = −18→18 |
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)] = 0.020 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.07 | w = 1/[σ2(Fo2) + (0.0192P)2 + 1.7359P] where P = (Fo2 + 2Fc2)/3 |
2976 reflections | (Δ/σ)max = 0.002 |
223 parameters | Δρmax = 0.49 e Å−3 |
0 restraints | Δρmin = −0.53 e Å−3 |
Crystal data top
(C5H7N2)[Cu2(OH)(SO4)2(H2O)2] | V = 1312.16 (8) Å3 |
Mr = 467.41 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.4094 (2) Å | µ = 3.62 mm−1 |
b = 12.6262 (5) Å | T = 150 K |
c = 14.0648 (5) Å | 0.12 × 0.12 × 0.10 mm |
β = 94.260 (1)° | |
Data collection top
Nonius KappaCCD area-detector diffractometer | 2897 reflections with I > 2σ(I) |
5582 measured reflections | Rint = 0.011 |
2976 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.020 | 0 restraints |
wR(F2) = 0.053 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.07 | Δρmax = 0.49 e Å−3 |
2976 reflections | Δρmin = −0.53 e Å−3 |
223 parameters | |
Special details top
Experimental. no |
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 (Å2) top | x | y | z | Uiso*/Ueq | |
Cu1 | 0.35817 (3) | 0.610067 (19) | 0.598745 (17) | 0.01544 (7) | |
Cu2 | 0.06515 (3) | 0.412756 (16) | 0.566423 (14) | 0.00766 (7) | |
S1 | 0.48497 (6) | 0.36798 (3) | 0.61096 (3) | 0.01021 (9) | |
O11 | 0.53456 (17) | 0.48180 (10) | 0.61639 (9) | 0.0130 (3) | |
O12 | 0.29820 (17) | 0.35241 (11) | 0.63871 (9) | 0.0146 (3) | |
O13 | 0.61011 (17) | 0.30834 (11) | 0.67745 (10) | 0.0171 (3) | |
O14 | 0.50067 (18) | 0.32825 (10) | 0.51344 (9) | 0.0137 (3) | |
S2 | −0.02231 (6) | 0.63774 (4) | 0.66167 (3) | 0.01160 (10) | |
O21 | 0.16711 (17) | 0.67886 (11) | 0.66790 (10) | 0.0187 (3) | |
O22 | −0.11303 (18) | 0.66678 (10) | 0.56838 (10) | 0.0158 (3) | |
O23 | −0.12076 (18) | 0.68802 (13) | 0.73675 (11) | 0.0241 (3) | |
O24 | −0.02038 (18) | 0.52238 (11) | 0.67483 (9) | 0.0158 (3) | |
O1 | 0.18655 (17) | 0.53348 (10) | 0.51320 (9) | 0.0106 (2) | |
OW2 | 0.5155 (2) | 0.69380 (18) | 0.68523 (15) | 0.0432 (6) | |
OW3 | −0.05529 (19) | 0.29428 (10) | 0.62080 (10) | 0.0123 (2) | |
N1 | 0.2423 (3) | 1.12649 (15) | 0.45813 (15) | 0.0266 (4) | |
C2 | 0.2267 (3) | 1.08908 (17) | 0.54591 (16) | 0.0245 (4) | |
H2 | 0.2081 | 1.1355 | 0.5956 | 0.029* | |
C3 | 0.2383 (3) | 0.98030 (16) | 0.56324 (15) | 0.0209 (4) | |
C4 | 0.2727 (3) | 0.91577 (16) | 0.48526 (16) | 0.0229 (4) | |
H4 | 0.2859 | 0.8431 | 0.4940 | 0.027* | |
C5 | 0.2870 (3) | 0.95847 (17) | 0.39623 (16) | 0.0267 (5) | |
H5 | 0.3077 | 0.9146 | 0.3451 | 0.032* | |
C6 | 0.2709 (3) | 1.06677 (18) | 0.38265 (16) | 0.0272 (5) | |
H6 | 0.2797 | 1.0968 | 0.3228 | 0.033* | |
N11 | 0.2188 (3) | 0.93968 (18) | 0.65064 (15) | 0.0389 (5) | |
H11A | 0.1987 | 0.9811 | 0.6973 | 0.047* | |
H11B | 0.2264 | 0.8724 | 0.6597 | 0.047* | |
H1N | 0.233 (4) | 1.186 (3) | 0.452 (2) | 0.041 (9)* | |
H1A | 0.001 (4) | 0.267 (2) | 0.663 (2) | 0.030 (7)* | |
H1 | 0.239 (3) | 0.512 (2) | 0.4775 (19) | 0.021 (7)* | |
H1B | −0.150 (4) | 0.307 (3) | 0.639 (2) | 0.039 (9)* | |
H2A | 0.475 (4) | 0.726 (3) | 0.728 (2) | 0.044 (9)* | |
H2B | 0.604 (5) | 0.683 (3) | 0.693 (2) | 0.040 (9)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cu1 | 0.00865 (12) | 0.02059 (13) | 0.01743 (13) | −0.00325 (8) | 0.00325 (9) | −0.01329 (9) |
Cu2 | 0.00764 (11) | 0.00702 (11) | 0.00845 (11) | −0.00039 (7) | 0.00144 (7) | 0.00101 (7) |
S1 | 0.00782 (19) | 0.0112 (2) | 0.0119 (2) | 0.00057 (15) | 0.00290 (15) | 0.00494 (15) |
O11 | 0.0117 (6) | 0.0104 (6) | 0.0172 (6) | −0.0002 (5) | 0.0031 (5) | 0.0004 (5) |
O12 | 0.0094 (6) | 0.0183 (7) | 0.0167 (6) | −0.0003 (5) | 0.0051 (5) | 0.0066 (5) |
O13 | 0.0113 (6) | 0.0211 (7) | 0.0189 (7) | 0.0020 (5) | 0.0017 (5) | 0.0123 (5) |
O14 | 0.0153 (6) | 0.0130 (6) | 0.0133 (6) | −0.0033 (5) | 0.0053 (5) | 0.0003 (5) |
S2 | 0.00673 (19) | 0.0149 (2) | 0.0131 (2) | 0.00054 (15) | 0.00024 (15) | −0.00647 (16) |
O21 | 0.0073 (6) | 0.0247 (7) | 0.0244 (7) | −0.0028 (5) | 0.0026 (5) | −0.0162 (6) |
O22 | 0.0165 (6) | 0.0120 (6) | 0.0181 (7) | 0.0050 (5) | −0.0037 (5) | −0.0027 (5) |
O23 | 0.0089 (6) | 0.0386 (9) | 0.0251 (8) | −0.0002 (6) | 0.0037 (5) | −0.0211 (7) |
O24 | 0.0173 (6) | 0.0170 (7) | 0.0134 (6) | 0.0015 (5) | 0.0037 (5) | 0.0018 (5) |
O1 | 0.0114 (6) | 0.0104 (6) | 0.0107 (6) | −0.0029 (5) | 0.0055 (5) | −0.0037 (5) |
OW2 | 0.0071 (7) | 0.0692 (14) | 0.0532 (12) | 0.0001 (8) | 0.0014 (7) | −0.0532 (11) |
OW3 | 0.0092 (6) | 0.0126 (6) | 0.0149 (6) | 0.0005 (5) | 0.0010 (5) | 0.0052 (5) |
N1 | 0.0369 (11) | 0.0114 (9) | 0.0313 (10) | 0.0054 (8) | 0.0024 (8) | 0.0020 (7) |
C2 | 0.0321 (12) | 0.0172 (10) | 0.0243 (11) | 0.0071 (8) | 0.0026 (9) | −0.0048 (8) |
C3 | 0.0210 (10) | 0.0205 (10) | 0.0211 (10) | 0.0049 (8) | 0.0010 (8) | −0.0002 (8) |
C4 | 0.0302 (11) | 0.0111 (9) | 0.0274 (11) | 0.0032 (8) | 0.0024 (9) | −0.0027 (8) |
C5 | 0.0385 (12) | 0.0186 (10) | 0.0230 (10) | 0.0027 (9) | 0.0030 (9) | −0.0057 (8) |
C6 | 0.0381 (13) | 0.0227 (11) | 0.0208 (10) | 0.0026 (9) | 0.0014 (9) | 0.0023 (8) |
N11 | 0.0664 (16) | 0.0280 (11) | 0.0238 (10) | 0.0124 (10) | 0.0132 (10) | 0.0038 (8) |
Geometric parameters (Å, º) top
Cu1—OW2 | 1.9355 (16) | O1—Cu2ii | 2.2097 (13) |
Cu1—O1 | 1.9422 (13) | O1—H1 | 0.71 (3) |
Cu1—O21 | 1.9771 (13) | OW2—H2A | 0.81 (3) |
Cu1—O11 | 2.0843 (13) | OW2—H2B | 0.67 (3) |
Cu1—O14i | 2.1061 (13) | OW3—H1A | 0.78 (3) |
Cu2—OW3 | 1.9288 (13) | OW3—H1B | 0.78 (3) |
Cu2—O1 | 1.9475 (13) | N1—C6 | 1.332 (3) |
Cu2—O12 | 2.0821 (13) | N1—C2 | 1.335 (3) |
Cu2—O24 | 2.1877 (13) | N1—H1N | 0.76 (3) |
Cu2—O22ii | 2.1975 (13) | C2—C3 | 1.396 (3) |
Cu2—O1ii | 2.2097 (13) | C2—H2 | 0.9300 |
Cu2—Cu2ii | 3.0015 (4) | C3—N11 | 1.350 (3) |
S1—O14 | 1.4731 (13) | C3—C4 | 1.405 (3) |
S1—O13 | 1.4740 (13) | C4—C5 | 1.375 (3) |
S1—O12 | 1.4786 (13) | C4—H4 | 0.9300 |
S1—O11 | 1.4839 (13) | C5—C6 | 1.385 (3) |
O14—Cu1i | 2.1061 (13) | C5—H5 | 0.9300 |
S2—O24 | 1.4682 (14) | C6—H6 | 0.9300 |
S2—O23 | 1.4713 (14) | N11—H11A | 0.8600 |
S2—O22 | 1.4754 (14) | N11—H11B | 0.8600 |
S2—O21 | 1.4929 (13) | | |
| | | |
OW2—Cu1—O1 | 175.86 (7) | O24—S2—O22 | 110.99 (8) |
OW2—Cu1—O21 | 82.58 (6) | O23—S2—O22 | 108.28 (8) |
O1—Cu1—O21 | 93.65 (6) | O24—S2—O21 | 109.71 (8) |
OW2—Cu1—O11 | 90.37 (7) | O23—S2—O21 | 108.78 (8) |
O1—Cu1—O11 | 93.60 (5) | O22—S2—O21 | 109.27 (9) |
O21—Cu1—O11 | 138.45 (6) | S2—O21—Cu1 | 121.51 (8) |
OW2—Cu1—O14i | 87.67 (8) | S2—O22—Cu2ii | 124.17 (8) |
O1—Cu1—O14i | 93.37 (5) | S2—O24—Cu2 | 122.71 (8) |
O21—Cu1—O14i | 128.29 (6) | Cu1—O1—Cu2 | 116.84 (7) |
O11—Cu1—O14i | 91.98 (5) | Cu1—O1—Cu2ii | 130.55 (7) |
OW3—Cu2—O1 | 179.19 (6) | Cu2—O1—Cu2ii | 92.22 (5) |
OW3—Cu2—O12 | 85.06 (6) | Cu1—O1—H1 | 105 (2) |
O1—Cu2—O12 | 94.83 (5) | Cu2—O1—H1 | 105 (2) |
OW3—Cu2—O24 | 92.74 (5) | Cu2ii—O1—H1 | 104 (2) |
O1—Cu2—O24 | 86.48 (5) | Cu1—OW2—H2A | 121 (2) |
O12—Cu2—O24 | 99.43 (5) | Cu1—OW2—H2B | 122 (3) |
OW3—Cu2—O22ii | 95.55 (5) | H2A—OW2—H2B | 113 (4) |
O1—Cu2—O22ii | 85.26 (5) | Cu2—OW3—H1A | 114 (2) |
O12—Cu2—O22ii | 94.18 (5) | Cu2—OW3—H1B | 115 (2) |
O24—Cu2—O22ii | 164.62 (5) | H1A—OW3—H1B | 106 (3) |
OW3—Cu2—O1ii | 92.36 (5) | C6—N1—C2 | 124.5 (2) |
O1—Cu2—O1ii | 87.78 (5) | C6—N1—H1N | 119 (2) |
O12—Cu2—O1ii | 176.39 (5) | C2—N1—H1N | 116 (2) |
O24—Cu2—O1ii | 83.20 (5) | N1—C2—C3 | 120.1 (2) |
O22ii—Cu2—O1ii | 83.53 (5) | N1—C2—H2 | 120.0 |
OW3—Cu2—Cu2ii | 132.78 (4) | C3—C2—H2 | 120.0 |
O1—Cu2—Cu2ii | 47.36 (4) | N11—C3—C2 | 121.6 (2) |
O12—Cu2—Cu2ii | 142.12 (4) | N11—C3—C4 | 121.9 (2) |
O24—Cu2—Cu2ii | 82.71 (4) | C2—C3—C4 | 116.53 (19) |
O22ii—Cu2—Cu2ii | 82.15 (4) | C5—C4—C3 | 120.97 (19) |
O1ii—Cu2—Cu2ii | 40.42 (3) | C5—C4—H4 | 119.5 |
O14—S1—O13 | 109.10 (8) | C3—C4—H4 | 119.5 |
O14—S1—O12 | 109.92 (8) | C4—C5—C6 | 120.1 (2) |
O13—S1—O12 | 108.76 (8) | C4—C5—H5 | 120.0 |
O14—S1—O11 | 109.96 (7) | C6—C5—H5 | 120.0 |
O13—S1—O11 | 108.69 (8) | N1—C6—C5 | 117.8 (2) |
O12—S1—O11 | 110.38 (8) | N1—C6—H6 | 121.1 |
S1—O11—Cu1 | 126.56 (8) | C5—C6—H6 | 121.1 |
S1—O12—Cu2 | 125.51 (8) | C3—N11—H11A | 120.0 |
S1—O14—Cu1i | 130.51 (8) | C3—N11—H11B | 120.0 |
O24—S2—O23 | 109.77 (9) | H11A—N11—H11B | 120.0 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11A···O24iii | 0.86 | 2.37 | 3.132 (2) | 148 |
N11—H11B···O21 | 0.86 | 2.49 | 3.326 (3) | 165 |
N11—H11B···O13iv | 0.86 | 2.64 | 3.122 (3) | 117 |
N1—H1N···O22v | 0.76 (3) | 2.07 (3) | 2.796 (2) | 160 (3) |
OW3—H1A···O23vi | 0.78 (3) | 1.90 (3) | 2.6697 (19) | 174 (3) |
O1—H1···O11i | 0.71 (3) | 2.22 (3) | 2.8616 (18) | 152 (3) |
OW3—H1B···O13vii | 0.78 (3) | 1.90 (3) | 2.6657 (19) | 168 (3) |
OW2—H2A···O13iv | 0.81 (3) | 1.83 (4) | 2.637 (2) | 176 (3) |
OW2—H2B···O23viii | 0.67 (3) | 2.09 (3) | 2.739 (2) | 165 (4) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (iii) −x, y+1/2, −z+3/2; (iv) −x+1, y+1/2, −z+3/2; (v) −x, −y+2, −z+1; (vi) −x, y−1/2, −z+3/2; (vii) x−1, y, z; (viii) x+1, y, z. |
Experimental details
Crystal data |
Chemical formula | (C5H7N2)[Cu2(OH)(SO4)2(H2O)2] |
Mr | 467.41 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 150 |
a, b, c (Å) | 7.4094 (2), 12.6262 (5), 14.0648 (5) |
β (°) | 94.260 (1) |
V (Å3) | 1312.16 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 3.62 |
Crystal size (mm) | 0.12 × 0.12 × 0.10 |
|
Data collection |
Diffractometer | Nonius KappaCCD area-detector diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5582, 2976, 2897 |
Rint | 0.011 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.020, 0.053, 1.07 |
No. of reflections | 2976 |
No. of parameters | 223 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.49, −0.53 |
Selected bond lengths (Å) topCu1—OW2 | 1.9355 (16) | Cu2—O1 | 1.9475 (13) |
Cu1—O1 | 1.9422 (13) | Cu2—O12 | 2.0821 (13) |
Cu1—O21 | 1.9771 (13) | Cu2—O24 | 2.1877 (13) |
Cu1—O11 | 2.0843 (13) | Cu2—O22ii | 2.1975 (13) |
Cu1—O14i | 2.1061 (13) | Cu2—O1ii | 2.2097 (13) |
Cu2—OW3 | 1.9288 (13) | Cu2—Cu2ii | 3.0015 (4) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11A···O24iii | 0.86 | 2.37 | 3.132 (2) | 148.3 |
N11—H11B···O21 | 0.86 | 2.49 | 3.326 (3) | 165.3 |
N11—H11B···O13iv | 0.86 | 2.64 | 3.122 (3) | 116.9 |
N1—H1N···O22v | 0.76 (3) | 2.07 (3) | 2.796 (2) | 160 (3) |
OW3—H1A···O23vi | 0.78 (3) | 1.90 (3) | 2.6697 (19) | 174 (3) |
O1—H1···O11i | 0.71 (3) | 2.22 (3) | 2.8616 (18) | 152 (3) |
OW3—H1B···O13vii | 0.78 (3) | 1.90 (3) | 2.6657 (19) | 168 (3) |
OW2—H2A···O13iv | 0.81 (3) | 1.83 (4) | 2.637 (2) | 176 (3) |
OW2—H2B···O23viii | 0.67 (3) | 2.09 (3) | 2.739 (2) | 165 (4) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (iii) −x, y+1/2, −z+3/2; (iv) −x+1, y+1/2, −z+3/2; (v) −x, −y+2, −z+1; (vi) −x, y−1/2, −z+3/2; (vii) x−1, y, z; (viii) x+1, y, z. |
In the course of our studies of copper carboxylates with organic amines, we have investigated the CuSO4/suberic acid/3-aminopyridine system. Attempts to prepare a new polymeric copper(II) dicarboxylate failed. Instead, the synthesis yielded prismatic orange–green crystals which proved to be the title new CuII basic sulfate species, L+Cu2(OH)(SO4)2(H2O)2, (I) (L+ is the 3-aminopyridinium cation). At first glance, the stoichiometry is reminiscent of that of the mineral natrochalcite, Na+Cu2(OH)(SO4)(H2O), from the tsumcorite group minerals, but detailed structural analysis reveals a novel structural arrangement that cannot be related to any of the known minerals containing tetrahedral XO42- anions (X = S, Se, Mo, As, P etc.).
The basic building unit of (I) is composed of two distinct Cu centres, bridged by two bidentate sulfate groups and by the hydroxide anion (Fig. 1). Additionally, a water molecule is coordinated to each of the two independent Cu atoms. The dimeric Cu2(OH)(SO4)(H2O)2 unit bears a negative charge, which is balanced by one 3-aminopyridinium cation per dimeric unit. Two dimeric units, related by an inversion centre, are further connected by a sulfate O atom and OH- anion to form a centrosymmetric tetranuclear entity (Fig. 2a). The negatively charged linear chains of tetramers are then generated by translation along [100] (Fig. 2b). Both sulfate anions thus connect three metal centres in a µ3-O,O',O'' binding mode. The shortest contact between Cu centres is observed for the two Cu2 atoms related by an inversion centre [Cu2···Cu2(-x, -y + 1, -z + 1) = 3.0015 (4) Å].
The crystallographically independent Cu atoms have distinct coordination environments. Atom Cu2 has a typical slightly distorted octahedral geometry of six O atoms (four belonging to sulfate groups, a water O atom and a hydroxide O atom). Atom Cu1 is five-coordinated by three sulfate O atoms, a water O atom and a hydroxide O atom, thus forming a polyhedron that could be described as a distorted trigonal bipyramid rather than a distorted square pyramid [the parameter τ (Addison et al., 1984) has a value of 0.62]. A pair of octahedra, related by an inversion centre and sharing a common edge, are connected to the trigonal bipyramid through a corner common to all three polyhedra (the triply bridging OH- group) and through the corners of sulfate tetrahedra, generating linear chains propagated along the a axis (Fig. 3a).
The 3-aminopyridinium cations are arranged between the chains with the ring plane almost perpendicular to the [100] direction. The pyridine rings of neighbouring cations are alternately slipped with respect to each other, but a substantial overlap of the aromatic rings still exsists, so that the interaction can be considered as π–π stacking. The plane-to-plane distance is 3.64 Å, whereas the centroid-to-centroid distance is only slightly longer (3.98 Å). There are a number of possible hydrogen-bond donors and acceptors, as illustrated by a rather complex hydrogen-bonding pattern, the details of which are listed in Table 2.
Taking the stoichiometry into account, the reported compound is closely related to the natrochalcite-type compounds M+Cu2(OH)(SO4/SeO4)2·H2O, with the tsumcorite parent structure MIMII(XO4)2(OH,H2O)2 (Tillmanns & Gebert, 1973; Giester & Zemann, 1987; Mihajlovic & Effenberger, 2004, and references therein). However, the structures differ significantly. Natrochalcite contains six-coordinated Cu centres in a distorted octahedral environment. Pairs of octahedra are edge-connected to form chains, which are linked by sulfate tetrahedra to form [Cu2(OH)(SO4) (H2O)]- sheets, interconnected by Na+ ions and O—H···O hydrogen bonds. There are several structural variations of the members of the parent tsumcorite type of compounds, although in all the reported structures, the MII metal is six-coordinated, whereas in the structure reported here, one of the Cu atoms is five-coordinated. Trigonal–bipyramidal CuO5 coordination in minerals is rather rare. To the best of our knowledge, it has only been observed in the mineral dolerophanite, Cu2O(SO4) (Effenberger, 1989). There is an additional distinct difference: all the compounds listed above contain two-dimensional layers that are further connected by monovalent cations and hydrogen bonds, while the title compound contains linear chains of [Cu2(OH)(SO4)2(H2O)2]- composition. The organic 3-aminopyridinium cation lacks coordination ability and, through its size, apparently prevents closer contacts between the chains.