Bis(2-amino­pyridinium) diaqua­bis(malonato-κ²O,O′)cuprate(II)

The Cu^II ion in the title compound, (C₅H₇N₂)₂[Cu(C₃H₂O₄)₂(H₂O)₂], is located on an inversion centre and coordinated by four O atoms from two bidentate malonate (mal) ligands in the equatorial plane and two O atoms from two coordinated water mol­ecules in the axial positions, forming an elongated octa­hedral geometry. Each [Cu(mal)₂(H₂O)₂]²⁻ anion bridges two 2-amino­pyridinium cations via N—H...O hydrogen bonds and symmetry-related anions via O—H...O hydrogen bonds, to form an infinite one-dimensional chain. Additional O—H...O and C—H...O hydrogen bonds generate two-dimensional sheets that are joined into a three-dimensional network via N—H...O, C—H...O and inter­layer π–π inter­actions between amino­pyridinium cations (symmetry code: ).

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.027
• wR factor = 0.075
• Data-to-parameter ratio = 11.1

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Author Response: We specify the role of each of the co-authors in this paper below.

 1. Somnath Ray Choudhury, Synthesis of the compound, purification, analyses
 of the results and drawing of the figures(Fig. 2-5)

 2. Jhimli Bhattacharyya, Synthesis of the compound and purification

 3. Suranjana Das, Synthesis of the compound and purification

 4. Biswajit Dey, literature searching and related matters

 5. Subrata Mukhopadhyay, manuscript composition and related matters like
 interpretation of results

 6. Li-Ping Lu, X-ray diffracting data, drawing of the fig.1 and Scheme

 7. Miao-li Zhu, Structural solution



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S1. Comment

The title complex, (I), (C₅H₅N₂H)₂[Cu(mal)₂(H₂O)₂] (Fig. 1), was synthesized from purely aqueous media by mixing the reactants in stoichiometric

ratio and adjusting the pH of the mixture with dilute NaOH. Selected geometric data are listed in Table 1.

The asymmetric unit of (I) consists of one diaquabis(malonato)cuprate(II) anion

and two protonated 2-aminopyridine cations. The coordination around Cu in the mononuclear unit is elongated octahedral, forming a CuO₆ chromophore. Four carboxylate O atoms from two bidentate malonate anions build the equatorial plane, with Cu—O bonds nearly identical [1.929 (15) and 1.933 (15) Å for Cu1—O3 and Cu1—O1, respectively], whereas two water molecules occupy the axial sites [2.665 (2) Å for Cu1—O5]. The values of the Cu—O(malonate) bonds and bond angles around Cu1 agree well with those previously reported for other malonate-containing Cu^II complexes. The axial Cu1—O5 bond is somewhat longer than that in the similar unit reported by other authors, e.g. [Cu(H₂O)₄][Cu(mal)₂(H₂O)₂] (Chattopadhyay et al., 1993), {[Cu(H₂O)₄]₂[Cu(mal)₂(H₂O)₂]} (Reference?), [Cu(mal)₂(H₂O)₂]{[Cu(H₂O)₄][Cu(mal)₂(H₂O)₂]} (Ruiz-Pérez et al. 2000) and [M^II(H₂O)₆][Cu^II(mal)₂(H₂O)₂] (Rodríguez-Martin et al. 2002).

Compound (I) is in form of a dianion. A comparison of the geometry of the current anion with that of the related neutral complex [Cu(Hmal)₂(H₂O)₂] (Lenstra & Kataeva, 2001) indicates shorter Cu—O bonds in the equatorial plane and longer axial bonds in (I), consistent with a Jahn–Teller effect. The

malonate ligands show a twist–boat conformation, with the methylene C atom out

of the chelate ring plane.

The supramolecular interactions in (I) are listed in Table 2. The monomeric anionic units link to one another via strong complementary O5—H5A···O2 hydrogen bonds generating an R₂²(12) (Bernstein et al., 1995) hydrogen-bonded supramolecular synthon, to give an infinite one-dimensional tape along the a axis (Fig. 2). Each monomeric unit also binds two 2-aminopyridine ligands via N2—H2C···O2 and N1—H1···O1 hydrogen bonds through the formation of an R₂²(8) hydrogen-bonding synthon (Fig. 2). Each such layer links adjacent layers along the b axis via O5—H5B···O4 hydrogen bonds, generating an R₂²(12) cyclic motif (Fig. 3). The aminopyridine unit from one layer also participates in hydrogen bonding via a C7—H7···O2 hydrogen bond with the adjacent layer to give a two-dimensional sheet. It is interesting to note that one H atom (H5A) of the coordinated water molecule helps the monomeric unit to grow one-dimensionally and the other H atom (H5B) helps the one-dimensional chains to grow two-dimensionally. These two-dimensional sheets propagate along the c axis direction through interlayer N2—H2D···O4 and C5—H5···O3 hydrogen bonds. Interlayer π–π (Fig. 4) stacking between aminopyridine moieties also provides additional stabilization of the ultimate three-dimensional structure (Fig. 5).

Related literature

For related literature, see: Chattopadhyay et al. (1993); Lenstra & Kataeva (2001); Rodríguez-Martin et al. (2002); Ruiz-Pérez et al. (2000); Bernstein et al. (1995).

S2. Experimental

Copper(II) acetate monohydrate (0.199 g, 1 mmol) was dissolved in water (20 ml) and allowed to react with malonic acid (0.208 g, 2 mmol) in water (10 ml) to give a clear blue solution. A warm aqueous solution (10 ml) of 2-aminopyridine (0.188 g, 2 mmol) was added dropwise to the above blue solution with continuous

stirring. The pH of this solution was adjusted to 5.20 by dropwise addition of dilute NaOH. This solution was heated at 323 K for 1 h with continuous stirring

and then filtered and kept for crystallization. Flat blue single crystals of (I) suitable for X-ray analysis were separated after several weeks from the mother liquor by slow evaporation at room temperature. The crystals were filtered off, washed with cold water and dried on filter paper (yield 0.24 g, 48%). Analysis, calculated for C₁₆H₂₂N₄O₁₀Cu: C 38.91, H 4.49, N 11.34%; found: C 38.22, H 3.89, N 10.91%.

S3. Refinement

H atoms attached to C and N atoms were placed in geometrically idealized positions, with Csp²—H = 0.93, Csp³—H = 0.97 and Nsp²—H = 0.86 Å, and constrained to ride on their parent atoms, with U_iso(H) = 1.2U_eq(C,N). H atoms attached to O (water) were located in a difference Fourier map and refined freely.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1999); software used to prepare material for publication: SHELXTL/PC.

Figures

	Fig. 1. The structure of (I), with displacement ellipsoids drawn at the 30% probability level. Dotted lines indicate hydrogen bonds. Unlabelled atoms are generated by the inversion operation (1 - x, 1 - y, 1 - z).
	Fig. 2. The one-dimensional assembly of monomeric units along the a axis with 2-aminopyridinium. Dashed lines indicate hydrogen bonds.
	Fig. 3. The two-dimensional assembly of monomeric units. Aminopyridinium ligands have been omitted for clarity. Dashed lines indicate hydrogen bonds.
	Fig. 4. The π–π stacking (blue dotted line) between aminopyridine units. N2—H2D···O4 and C5—H5···O3 hydrogen bonds (dashed lines) help to grow the structure along c axis.
	Fig. 5. The packing of complex (I), resulting in the three-dimensional assembly. Dotted lines indicate hydrogen bonds.

Bis(2-aminopyridinium) diaquabis(malonato-κ²O,O')cuprate(II)

Crystal data

(C5H7N2)2[Cu(C3H2O4)2(H2O)2]	Z = 1
Mr = 493.92	F(000) = 255
Triclinic, P1	Dx = 1.694 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.0433 (13) Å	Cell parameters from 1903 reflections
b = 7.9116 (15) Å	θ = 3.2–26.9°
c = 9.5767 (18) Å	µ = 1.19 mm^−1
α = 96.096 (2)°	T = 298 K
β = 107.865 (2)°	Block, blue
γ = 103.743 (2)°	0.50 × 0.40 × 0.30 mm
V = 484.03 (16) Å^3

Data collection

Bruker SMART 1K CCD area-detector diffractometer	1659 independent reflections
Radiation source: fine-focus sealed tube	1616 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.013
ω scans	θmax = 25.0°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	h = −8→8
Tmin = 0.587, Tmax = 0.716	k = −7→9
1987 measured reflections	l = −11→10

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.075	H atoms treated by a mixture of independent and constrained refinement
S = 1.14	w = 1/[σ^2(Fo^2) + (0.0298P)^2 + 0.2343P] where P = (Fo^2 + 2Fc^2)/3
1659 reflections	(Δ/σ)max = 0.001
150 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.27 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.5000	0.5000	0.5000	0.03666 (15)
O1	0.3286 (2)	0.5451 (2)	0.61517 (16)	0.0376 (3)
O2	0.1202 (3)	0.6770 (2)	0.68071 (18)	0.0439 (4)
O3	0.3648 (2)	0.6104 (2)	0.34319 (15)	0.0369 (3)
O4	0.2336 (3)	0.8215 (2)	0.26013 (18)	0.0486 (4)
O5	0.7799 (3)	0.8175 (3)	0.6047 (2)	0.0528 (5)
C1	0.2326 (3)	0.6633 (3)	0.6054 (2)	0.0303 (4)
C2	0.2668 (4)	0.7969 (3)	0.5094 (2)	0.0390 (5)
H2A	0.3917	0.8911	0.5679	0.047*
H2B	0.1517	0.8487	0.4899	0.047*
C3	0.2884 (3)	0.7385 (3)	0.3595 (2)	0.0325 (4)
C4	0.2435 (3)	0.4109 (3)	0.9537 (2)	0.0338 (4)
C5	0.2439 (3)	0.3007 (3)	1.0592 (2)	0.0403 (5)
H5	0.2326	0.3410	1.1503	0.048*
C6	0.2608 (4)	0.1344 (3)	1.0272 (3)	0.0494 (6)
H6	0.2603	0.0608	1.0967	0.059*
C7	0.2791 (4)	0.0732 (3)	0.8911 (3)	0.0497 (6)
H7	0.2896	−0.0408	0.8690	0.060*
C8	0.2810 (4)	0.1815 (3)	0.7930 (3)	0.0439 (5)
H8	0.2933	0.1425	0.7019	0.053*
N1	0.2655 (3)	0.3464 (2)	0.82503 (19)	0.0355 (4)
H1	0.2697	0.4138	0.7606	0.043*
N2	0.2258 (3)	0.5744 (2)	0.9738 (2)	0.0424 (4)
H2C	0.2285	0.6366	0.9057	0.051*
H2D	0.2117	0.6180	1.0550	0.051*
H5A	0.889 (6)	0.788 (5)	0.630 (4)	0.076 (11)*
H5B	0.803 (5)	0.908 (4)	0.651 (3)	0.056 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0490 (2)	0.0496 (3)	0.0299 (2)	0.03156 (18)	0.02295 (17)	0.01711 (16)
O1	0.0514 (9)	0.0448 (8)	0.0358 (8)	0.0291 (7)	0.0264 (7)	0.0181 (6)
O2	0.0540 (9)	0.0571 (10)	0.0429 (9)	0.0338 (8)	0.0308 (8)	0.0194 (7)
O3	0.0502 (9)	0.0432 (8)	0.0275 (7)	0.0250 (7)	0.0175 (6)	0.0102 (6)
O4	0.0646 (11)	0.0630 (11)	0.0404 (9)	0.0396 (9)	0.0268 (8)	0.0283 (8)
O5	0.0483 (11)	0.0505 (12)	0.0596 (12)	0.0219 (9)	0.0138 (9)	0.0073 (10)
C1	0.0349 (10)	0.0336 (10)	0.0250 (9)	0.0146 (9)	0.0108 (8)	0.0036 (8)
C2	0.0555 (13)	0.0354 (11)	0.0379 (11)	0.0233 (10)	0.0233 (10)	0.0116 (9)
C3	0.0341 (10)	0.0373 (11)	0.0308 (10)	0.0143 (9)	0.0133 (8)	0.0107 (8)
C4	0.0303 (10)	0.0374 (11)	0.0307 (10)	0.0056 (9)	0.0100 (8)	0.0057 (8)
C5	0.0471 (12)	0.0443 (13)	0.0305 (11)	0.0103 (10)	0.0156 (9)	0.0103 (9)
C6	0.0576 (15)	0.0451 (14)	0.0442 (13)	0.0100 (11)	0.0160 (11)	0.0183 (11)
C7	0.0602 (15)	0.0338 (12)	0.0541 (15)	0.0132 (11)	0.0196 (12)	0.0057 (10)
C8	0.0500 (13)	0.0419 (12)	0.0383 (12)	0.0106 (10)	0.0176 (10)	−0.0001 (10)
N1	0.0394 (9)	0.0397 (10)	0.0288 (9)	0.0101 (8)	0.0137 (7)	0.0093 (7)
N2	0.0559 (12)	0.0402 (10)	0.0381 (10)	0.0170 (9)	0.0229 (9)	0.0095 (8)

Geometric parameters (Å, º)

Cu1—O3^i	1.9293 (14)	C4—N2	1.328 (3)
Cu1—O3	1.9293 (14)	C4—N1	1.350 (3)
Cu1—O1	1.9336 (14)	C4—C5	1.403 (3)
Cu1—O1^i	1.9336 (14)	C5—C6	1.360 (3)
Cu1—O5	2.665 (2)	C5—H5	0.9300
O1—C1	1.273 (2)	C6—C7	1.396 (4)
O2—C1	1.238 (2)	C6—H6	0.9300
O3—C3	1.272 (2)	C7—C8	1.338 (3)
O4—C3	1.230 (3)	C7—H7	0.9300
O5—H5A	0.83 (4)	C8—N1	1.347 (3)
O5—H5B	0.76 (3)	C8—H8	0.9300
C1—C2	1.498 (3)	N1—H1	0.8600
C2—C3	1.524 (3)	N2—H2C	0.8600
C2—H2A	0.9700	N2—H2D	0.8600
C2—H2B	0.9700
O3^i—Cu1—O3	180.0	O4—C3—C2	117.50 (18)
O3^i—Cu1—O1	87.80 (6)	O3—C3—C2	119.42 (17)
O3—Cu1—O1	92.20 (6)	N2—C4—N1	118.51 (19)
O3^i—Cu1—O1^i	92.20 (6)	N2—C4—C5	124.0 (2)
O3—Cu1—O1^i	87.80 (6)	N1—C4—C5	117.5 (2)
O1—Cu1—O1^i	180.0	C6—C5—C4	119.5 (2)
O3—Cu1—O5	84.65 (6)	C6—C5—H5	120.3
O3^i—Cu1—O5	95.35 (6)	C4—C5—H5	120.3
O1^i—Cu1—O5	84.96 (7)	C5—C6—C7	120.6 (2)
O1—Cu1—O5	95.04 (7)	C5—C6—H6	119.7
C1—O1—Cu1	126.40 (13)	C7—C6—H6	119.7
C3—O3—Cu1	126.18 (13)	C8—C7—C6	118.8 (2)
H5A—O5—H5B	107 (3)	C8—C7—H7	120.6
O2—C1—O1	121.31 (18)	C6—C7—H7	120.6
O2—C1—C2	118.82 (18)	C7—C8—N1	120.5 (2)
O1—C1—C2	119.74 (17)	C7—C8—H8	119.7
C1—C2—C3	119.44 (18)	N1—C8—H8	119.7
C1—C2—H2A	107.5	C8—N1—C4	123.03 (19)
C3—C2—H2A	107.5	C8—N1—H1	118.5
C1—C2—H2B	107.5	C4—N1—H1	118.5
C3—C2—H2B	107.5	C4—N2—H2C	120.0
H2A—C2—H2B	107.0	C4—N2—H2D	120.0
O4—C3—O3	123.06 (18)	H2C—N2—H2D	120.0
O3^i—Cu1—O1—C1	157.70 (18)	C1—C2—C3—O4	151.5 (2)
O3—Cu1—O1—C1	−22.30 (18)	C1—C2—C3—O3	−29.9 (3)
O1—Cu1—O3—C3	31.54 (17)	N2—C4—C5—C6	179.4 (2)
O1^i—Cu1—O3—C3	−148.46 (17)	N1—C4—C5—C6	−1.6 (3)
Cu1—O1—C1—O2	177.25 (15)	C4—C5—C6—C7	0.4 (4)
Cu1—O1—C1—C2	−7.0 (3)	C5—C6—C7—C8	0.5 (4)
O2—C1—C2—C3	−145.0 (2)	C6—C7—C8—N1	−0.1 (4)
O1—C1—C2—C3	39.2 (3)	C7—C8—N1—C4	−1.2 (3)
Cu1—O3—C3—O4	168.22 (16)	N2—C4—N1—C8	−178.8 (2)
Cu1—O3—C3—C2	−10.4 (3)	C5—C4—N1—C8	2.0 (3)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1	0.86	1.91	2.756 (2)	168
N2—H2C···O2	0.86	2.14	2.930 (3)	152
N2—H2D···O4^ii	0.86	2.35	3.172 (3)	161
O5—H5A···O2^iii	0.83 (4)	1.99 (4)	2.807 (3)	171 (3)
O5—H5B···O4^iv	0.76 (3)	2.31 (3)	3.043 (3)	161 (3)
C5—H5···O3^ii	0.93	2.45	3.209 (3)	139
C6—H6···O4^v	0.93	2.59	3.514 (3)	172
C7—H7···O2^vi	0.93	2.49	3.278 (3)	142

Symmetry codes: (ii) x, y, z+1; (iii) x+1, y, z; (iv) −x+1, −y+2, −z+1; (v) x, y−1, z+1; (vi) x, y−1, z.