organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

Piperazine-2,5-dione–oxalic acid–water (1/1/2) and a redetermination of piperazine-2,5-dione, both at 120 K: hydrogen-bonded sheets containing multiple ring types

aSchool of Chemical and Biotechnology, Shanmugha Arts, Science, Technology and Research Academy (SASTRA), Tirumalaisamudram, Thanjavur 623 106, India, bDepartment of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, India, cDepartment of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and dSchool of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland
*Correspondence e-mail: cg@st-andrews.ac.uk

(Received 20 December 2004; accepted 21 December 2004; online 31 January 2005)

In piperazine-2,5-dione–oxalic acid–water (1/1/2), C4H6N2O2·C2H2O4·2H2O, both organic components lie across inversion centres in space group [P\overline{1}]. The molecules are linked by N—H⋯O and by both two-centre O—H⋯O and three-centre O—H⋯(O)2 hydrogen bonds into sheets built from [R_{1}^{2}](5), [R_{2}^{2}](8), [R_{4}^{4}](8) and [R_{5}^{4}](15) rings. In piperazine-2,5-dione, C4H6N2O2, where the molecules lie across centres of inversion in space group P21/c, the molecules are linked by paired N—H⋯O hydrogen bonds into ribbons of centrosymmetric [R_{2}^{2}](8) rings, which are further linked into sheets by C—H⋯O hydrogen bonds, generating [R_{4}^{3}](14) rings between the ribbons.

Comment

Hydrogen-bonded adducts formed between piperazine-2,5-dione (diketopiperazine, DKP) and carboxylic acids are often characterized by the formation of ribbons of piperazine-2,5-dione molecules; these can be linked into sheets by carboxylic acids, while monocarboxylic acids can simply be pendent from these ribbons (Kartha et al., 1981[Kartha, G., Varughese, K. I. & Lu, C. T. (1981). Acta Cryst. B37, 1798-1800.]; Luo & Palmore, 2002[Luo, T. J. M. & Palmore, G. T. R. (2002). Cryst. Growth Des. 2, 337-350.]). A striking exception is found in the 1:2 adduct of piperazine-2,5-dione with 2-hydroxy­benzoic acid, where a finite three-component aggregate is formed (Varughese & Kartha, 1982[Varughese, K. I. & Kartha, G. (1982). Acta Cryst. B38, 301-302.]). As part of a wider study of the supramolecular structures of systems containing piperazine-2,5-dione, which includes the study both of hydrogen-bonded systems and of metal coordination complexes, we report here the structure of piperazine-2,5-dione–oxalic acid–water (1/1/2), (I)[link], together with a redetermination at 120 K of piperazine-2,5-dione itself, (II)[link].

The organic components in (I) both lie across inversion centres in space group P[\overline{1}] and the water molecule lies in a general position. While the selection of the asymmetric unit in a three-component adduct such as this provides some degree of flexibility and choice, for compound (I) it is possible to select a compact and connected asymmetric unit such that the heterocyclic and acidic components lie across the inversion centres at ([{1\over 2}], 0, [{1\over 2}]) and (0, 1, 0), respectively (Fig. 1[link]).

[Scheme 1]

The H atoms are fully ordered and the location of the unique H atom in the acid, as deduced from a difference map, is fully consistent with the independent C—O bond distances in this component (Table 1[link]). The bond distances in the dione are all typical of their types, but the long C—C bond in the acid is consistent with such values in simple derivatives of oxalic acid (Allen et al., 1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-19.]).

The independent components are linked into sheets by a combination of one two-centre N—H⋯O hydrogen bond, two two-centre O—H⋯O hydrogen bonds and one almost planar, but asymmetric, three-centre O—H⋯(O)2 hydrogen bond (Table 2[link]). The formation of the sheet structure, which contains four distinct types of hydrogen-bonded ring, is readily analysed in terms of two one-dimensional substructures generated, respectively, by the piperazinedione component on the one hand and by the acid and water molecules on the other; the linking of these substructures generates the sheet.

In the first substructure, amide atoms N1 at (x, y, z) and (1 − x, −y, 1 − z) are both components of the reference piperazinedione molecule centred at ([{1\over 2}], 0, [{1\over 2}]); these atoms act as hydrogen-bond donors to amide atoms O2 at (2 − x, −y, 1 − z) and (−1 + x, y, z), respectively, which are themselves components of the dione molecules centred at ([{3\over 2}], 0, [1\over2]) and (−[{1\over 2}], 0, [{1\over 2}]). Propagation by inversion of this hydrogen bond then generates a C(6)[[R_{2}^{2}](8)] chain of rings (Bernstein et al., 1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]) running parallel to the [100] direction, in which dione mol­ecules centred at (n + [{1\over 2}], 0, [{1\over 2}]) (n = zero or integer) alternate with [R_{2}^{2}](8) rings centred at (n, 0, [{1\over 2}]) (n = zero or integer) (Fig. 2[link]).

In the second substructure, carboxyl atom O11 at (x, y, z), which forms part of the acid molecule centred across (0, 1, 0), acts as a hydrogen-bond donor to water atom O1, also at (x, y, z). This water atom in turn acts as a donor, via H1B, to carbonyl atom O12 at (1 + x, y, z) and to carboxyl atom O11 at (1 − x, 2 − y, −z), both of which lie in the acid molecule centred across (1, 1, 0). Although the three-centre hydrogen bond involving H1B is asymmetric (Table 2[link]), the sum of the angles at H1B is 358°; while the longer, weaker, component may be an adventitious consequence of the other, shorter, O—H⋯O interactions in the structure, its presence or absence does not affect the overall supramolecular structure, only the details of the hydrogen-bonded ring systems. Propagation of these two hydrogen-bonding interactions generates a chain of edge-fused [R_{1}^{2}](5) and [R_{4}^{4}](8) rings running parallel to the [100] direction, in which acid molecules centred at (n, 1, 0) (n = zero or integer) alternate with [R_{4}^{4}](8) rings centred at (n + [{1\over 2}], 1, 0) (n = zero or integer) (Fig. 3[link]).

The final O—H⋯O hydrogen bond links the two types of [100] chain into a sheet. The water molecule at (x, y, z), which lies in the acid–water chain along (x, 1, 0), acts as a hydrogen-bond donor, via H1A, to amide atom O2, also at (x, y, z), which lies in the piperazinedione chain along (x, 0, [1\over2]). Propagation by inversion of this final hydrogen bond then links the chains into a (012) sheet in which piperazinedione chains alternate with acid–water chains (Fig. 4[link]). The hydrogen-bonded rings that link the two types of chain are of [R_{5}^{4}](15) type so that there are, in fact, four types of ring embedded within the sheet, of [R_{1}^{2}](5), [R_{2}^{2}](8), [R_{4}^{4}](8) and [R_{5}^{4}](15) types. There are no direction-specific interactions between adjacent sheets.

The two substructures observed in the structure of (I) may usefully be compared with the hydrogen-bonded structures of piperazine-2,5-dione and oxalic acid dihydrate. Two polymorphs of oxalic acid dihydrate have been reported (Iwasaki et al., 1967[Iwasaki, F. F., Iwasaki, H. & Saito, Y. (1967). Acta Cryst. 23, 64-70.]; Delaplane & Ibers, 1969[Delaplane, R. G. & Ibers, J. A. (1969). Acta Cryst. B25, 2423-2437.]); in each form, the oxalic acid molecules lie across centres of inversion, but the hydrogen-bonded network is three-dimensional in each polymorph, as opposed to the two-dimensional acid–water substructure found in (I). The structure of piperazine-2,5-dione, (II), was reported many years ago (Degeilh & Marsh, 1959[Degeilh, R. & Marsh, R. E. (1959). Acta Cryst. 12, 1007-1014.]) to consist of hydrogen-bonded ribbons of centrosymmetric molecules. We have now reinvestigated this structure at 120 K (Fig. 5[link]) and we find that these [101] ribbons are in fact linked by a C—H⋯O hydrogen bond (Table 3[link]) into (11[\overline1]) sheets containing both [R_{2}^{2}](8) and [R_{4}^{3}](14) rings (Fig. 6[link]). In the formation of adduct (I), the C—H⋯O hydrogen bonds in (II) have been displaced by much stronger O—H⋯O hydrogen bonds, while the N—H⋯O hydrogen bonds are all preserved.

[Figure 1]
Figure 1
The independent molecular components of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level, and atoms labelled with the suffixes A and B are at the symmetry positions (1 − x, −y, 1 − z) and (−x, 2 − y, −z), respectively.
[Figure 2]
Figure 2
Part of the crystal structure of (I), showing the formation of a [100] chain of rings built from piperazinedione molecules only. For clarity, H atoms bonded to C atoms have been omitted. Atoms marked with an asterisk (*), a hash (#) or a dollar sign ($) are at the symmetry positions (2 − x, −y, 1 − z), (1 − x, −y, 1 − z) and (−1 + x, y, z), respectively.
[Figure 3]
Figure 3
Part of the crystal structure of (I), showing the formation of a [100] chain of edge-fused rings built from acid and water molecules only. Atoms marked with an asterisk (*), a hash (#) or a dollar sign ($) are at the symmetry positions (1 − x, 2 − y, −z), (−x, 2 − y, −z) and (1 + x, y, z), respectively.
[Figure 4]
Figure 4
A stereoview of part of the crystal structure of (I), showing the formation of a (012) sheet containing [R_{1}^{2}](5), [R_{2}^{2}](8), [R_{4}^{4}](8) and [R_{5}^{4}](15) rings. For clarity, H atoms bonded to C atoms have been omitted.
[Figure 5]
Figure 5
The molecule of (II), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and atoms labelled with the suffix A are at the symmetry position (2 − x, 1 − y, 2 − z).
[Figure 6]
Figure 6
A stereoview of part of the crystal structure of (II), showing the formation of a (11[\overline1]) sheet of [R_{2}^{2}](8) and [R_{4}^{3}](14) rings.

Experimental

Oxalic acid (0.5 g, 3.96 mmol) was dissolved in hot water. To the resulting clear solution was added a solution of piperazine-2,5-dione (0.45 g, 3.96 mmol) in hot water. The mixture was heated over a water bath for 5 h to obtain a clear solution. This solution was allowed to cool to room temperature and crystals of (I) suitable for single-crystal X-ray diffraction were obtained after 2 d [m.p. 473 K; IR: 1681 cm−1 (C=O)]. Crystals of (II) were also obtained from aqueous solution [IR: 1702 cm−1 (C=O)].

Compound (I)

Crystal data
  • C4H6N2O2·C2H2O4·2H2O

  • Mr = 240.18

  • Triclinic, P[\bar{1}]

  • a = 6.1494 (7) Å

  • b = 6.1984 (8) Å

  • c = 7.3642 (9) Å

  • α = 83.486 (6)°

  • β = 82.580 (8)°

  • γ = 65.067 (7)°

  • V = 251.86 (6) Å3

  • Z = 1

  • Dx = 1.583 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 1073 reflections

  • θ = 3.0–27.5°

  • μ = 0.15 mm−1

  • T = 120 (2) K

  • Plate, colourless

  • 0.42 × 0.18 × 0.08 mm

Data collection
  • Nonius KappaCCD diffractometer

  • φ and ω scans

  • Absorption correction: multi-scan(SADABS; Sheldrick, 2003[Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.])Tmin = 0.931, Tmax = 0.988

  • 4586 measured reflections

  • 1143 independent reflections

  • 1043 reflections with I > 2σ(I)

  • Rint = 0.048

  • θmax = 27.6°

  • h = −7 → 7

  • k = −8 → 8

  • l = −9 → 9

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.042

  • wR(F2) = 0.136

  • S = 1.20

  • 1143 reflections

  • 74 parameters

  • H-atom parameters constrained

  • w = 1/[σ2(Fo2) + (0.0795P)2 + 0.0483P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.41 e Å−3

  • Δρmin = −0.32 e Å−3

Table 1
Selected geometric parameters (Å) for (I)

N1—C2 1.3192 (18)
N1—C3i 1.4510 (19)
C2—O2 1.2497 (17)
C2—C3 1.5042 (19)
C11—O11 1.2982 (16)
C11—O12 1.2107 (17)
C11—C11ii 1.545 (3)
Symmetry codes: (i) -x+1, -y, -z+1; (ii) -x, -y+2, -z.

Table 2
Hydrogen-bond geometry (Å, °) for (I)

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1A⋯O2 0.91 1.80 2.6971 (14) 168
O1—H1B⋯O12iii 0.85 1.99 2.8208 (15) 167
O1—H1B⋯O11iv 0.85 2.46 2.9565 (15) 118
O11—H11⋯O1 0.84 1.69 2.5040 (14) 164
N1—H1⋯O2v 0.88 2.01 2.8807 (16) 170
Symmetry codes: (iii) x+1, y, z; (iv) -x+1, -y+2, -z; (v) -x+2, -y, -z+1.

Compound (II)

Crystal data
  • C4H6N2O2

  • Mr = 114.11

  • Monoclinic, P21/c

  • a = 3.8967 (10) Å

  • b = 11.527 (3) Å

  • c = 5.159 (2) Å

  • β = 96.46 (2)°

  • V = 230.26 (12) Å3

  • Z = 2

  • Dx = 1.646 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 508 reflections

  • θ = 4.4–27.5°

  • μ = 0.13 mm−1

  • T = 120 (2) K

  • Plate, colourless

  • 0.58 × 0.26 × 0.06 mm

Data collection
  • Nonius KappaCCD diffractometer

  • φ scans, and ω scans with κ offsets

  • Absorption correction: multi-scan(SORTAV; Blessing, 1995[Blessing, R. H. (1995). Acta Cryst. A51, 33-37.], 1997[Blessing, R. H. (1997). J. Appl. Cryst. 30, 421-426.])Tmin = 0.935, Tmax = 0.992

  • 2525 measured reflections

  • 508 independent reflections

  • 490 reflections with I > 2σ(I)

  • Rint = 0.105

  • θmax = 27.5°

  • h = −4 → 4

  • k = −14 → 14

  • l = −6 → 6

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.067

  • wR(F2) = 0.206

  • S = 1.25

  • 508 reflections

  • 37 parameters

  • H-atom parameters constrained

  • w = 1/[σ2(Fo2) + (0.1311P)2 + 0.0775P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.48 e Å−3

  • Δρmin = −0.49 e Å−3

Table 3
Hydrogen-bond geometry (Å, °) for (II)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1⋯O2vi 0.88 1.96 2.840 (2) 176
C3—H3B⋯O2vii 0.99 2.51 3.266 (3) 133
Symmetry codes: (vi) -x+1, -y+1, -z+1; (vii) [x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}].

Crystals of (I) are triclinic; space group [P\overline 1] was selected and confirmed by the subsequent analysis. For (II), the space group P21/c was uniquely assigned from the systematic absences. All H atoms were located from difference maps. H atoms in the organic components were subsequently treated as riding atoms, with C—H distances of 0.99 Å, N—H distances of 0.88 Å and an O—H distance of 0.84 Å, and with Uiso(H) values of 1.2Ueq(C,N) or 1.5Ueq(O). H atoms in the water molecule were permitted to ride at the distances found from the difference maps (O—H = 0.85 and 0.91 Å), with Uiso(H) values of 1.5Ueq(O). For both structures, several very intense low-angle reflections were rejected during the data processing because of incomplete profiles and/or detector saturation.

For (I), data collection: COLLECT (Hooft, 1999[Hooft, R. W. W. (1999). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) and COLLECT; data reduction: DENZO and COLLECT. For (II), data collection: KappaCCD Server Software (Nonius, 1997[Nonius (1997). KappaCCD Server Software. Windows 3.11 Version. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO–SMN (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO–SMN. For both compounds, structure solution: OSCAIL (McArdle, 2003[McArdle, P. (2003). OSCAIL for Windows. Version 10. Crystallography Centre, Chemistry Department, NUI Galway, Ireland.]) and SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); structure refinement: OSCAIL and SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: PLATON (Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]); publication software: SHELXL97 and PRPKAPPA (Ferguson, 1999[Ferguson, G. (1999). PRPKAPPA. University of Guelph, Canada.]).

Supporting information


Comment top

Hydrogen-bonded adducts formed between 2,5-piperazinedione (diketopiperazine, DKP, C4H6N2O2) and carboxylic acids are often characterized by the formation of ribbons of 2,5-piperazinedione molecules; these can be linked into sheets by carboxylic acids, while monocarboxylic acids can simply be pendent from these ribbons (Kartha et al., 1981; Luo & Palmore, 2002). A striking exception is found in the 1:2 adduct of 2,5-piperazinedione with 2-hydroxybenzoic acid, where a finite three-component aggregate is formed (Varughese & Kartha, 1982). As part of a wider study of the supramolecular structures of systems containing 2,5-piperazinedione, which includes the study both of hydrogen-bonded systems and of metal coordination complexes, we report here the structure of 2,5-piperazinedione–oxalic acid–water (1/1/2), (I), together with a redetermination at 120 K of 2,5-piperazinedione itself, (II).

The organic components in (I) both lie across inversion centres in space group P1 and the water molecule lies in a general position. While the selection of the asymmetric unit in a three-component adduct such as this provides some degree of flexibility and choice, for compound (I) it is possible to select a compact and connected asymmetric unit such that the heterocyclic and acidic components lie across the inversion centres at (1/2, 0,1/2) and (0, 1, 0), respectively (Fig. 1).

The H atoms are fully ordered and the location of the unique H atom in the acid, as deduced from a difference map, is fully consistent with the independent C—O bond distances in this component (Table 1). The bond distances in the dione are all typical of their types, but the long C—C bond in the acid is consistent with such values in simple derivatives of oxalic acid (Allen et al., 1987).

The independent components are linked into sheets by a combination of one two-centre N—H···O hydrogen bond, two two-centre O—H···O hydrogen bonds and one almost planar, but asymmetric three-centre O—H···(O)2 hydrogen bond (Table 2). The formation of the sheet structure, which contains four distinct types of hydrogen-bonded ring, is readily analysed in terms of two one-dimensional substructures generated, respectively, by the piperazinedione component on the one hand, and by the acid and water molecules on the other; the linking of these substructures generates the sheet.

In the first substructure, amide atoms N1 at (x, y, z) and (1 − x, −y, 1 − z) are both components of the reference piperazinedione molecule centred at (1/2, 0,1/2); these atoms act as hydrogen-bond donors to amine atoms O2 at (2 − x, −y, 1 − z) and (−1 + x, y, z), respectively, which are themselves components of the dione molecules centred at (3/2, 0,1/2) and (−1/2, 0,1/2). Propagation by inversion of this hydrogen bond then generates a C(6)[R22(8)] chain of rings (Bernstein et al., 1995) running parallel to the [100] direction, in which dione molecules centred at (n + 1/2, 0,1/2) (n = zero or integer) alternate with R22(8) rings centred at (n, 0,1/2) (n = zero or integer) (Fig. 2).

In the second substructure, carboxyl atom O11 at (x, y, z), which forms part of the acid molecule centred across (0, 1, 0), acts as a hydrogen-bond donor to water atom O1, also at (x, y, z). This water atom in turn acts as a donor, via H1B, to carbonyl atom O12 at (1 + x, y, z) and to carboxyl atom O11 at (1 − x, 2 − y, −z), both of which lie in the acid molecule centred across (1, 1, 0). Although the three-centre hydrogen bond involving H1B is asymmetric (Table 2), the sum of the angles at H1B is 358°; while the longer, weaker, component may be an adventitious consequence of the other, shorter, O—H···O interactions in the structure, its presence or absence does not affect the overall supramolecular structure, only the details of the hydrogen-bonded ring systems. Propagation of these two hydrogen-bonding interactions generates a chain of edge-fused R12(5) and R44(8) rings running parallel to the [100] direction, in which acid molecules centred at (n, 1, 0) (n = zero or integer) alternate with R44(8) rings centred at (n + 1/2, 1, 0) (n = zero or integer) (Fig. 3).

The final O—H···O hydrogen bond links the two types of [100] chain into a sheet. The water molecule at (x, y, z), which lies in the acid/water chain along (x, 1, 0), acts as a hydrogen-bond donor, via H1A, to amine atom O2, also at (x, y, z), which lies in the piperazinedione chain along (x, 0,1/2). Propagation by inversion of this final hydrogen bond then links the chains into a (012) sheet in which piperazinedione chains alternate with acid–water chains (Fig. 4). The hydrogen-bonded rings that link the two types of chain are of R54(15) type so that there are, in fact, four types of ring embedded within the sheet, of R12(5), R22(8), R44(8) and R45(15) types. There are no direction-specific interactions between adjacent sheets.

The two substructures observed in the structure of (I) may usefully be compared with the hydrogen-bonded structures of 2,5-piperazinedione and of oxalic acid dihydrate. Two polymorphs of oxalic acid dihydrate have been reprorted (Iwasaki et al., 1967; Delaplane & Ibers, 1969); in each form, the oxalic acid molecules lie across centres of inversion, but the hydrogen-bonded network is three-dimensional in each polymorph, as opposed to the two-dimensional acid–water substructure found in (I). The structure of 2,5-piperazinedione, (II), was reported many years ago (Degeilh & Marsh, 1959) to consist of hydrogen-bonded ribbons of centrosymmetric molecules. We have now reinvestigated this structure at 120 K (Fig. 5) and find that these [101] ribbons are in fact linked by a C—H···O hydrogen bond (Table 3) into (11–1) sheets containing both R22(8) and R43(14) rings (Fig. 6). In the formation of adduct (I), the C—H···O hydrogen bonds in (II) have been displaced by much stronger O—H···O hydrogen bonds, while the N—H···O hydrogen bonds are all preserved.

Experimental top

Oxalic acid (0.5 g, 3.96 mmol) was dissolved in hot water. To the resulting clear solution a solution of 2,5-diketopiperazine (0.45 g, 3.96 mmol) in hot water was added. The mixture was heated over a water bath for 5 h to obtain a clear solution. This solution was allowed to cool to room temperature, and crystals of (I) suitable for single-crystal X-ray diffraction were obtained after two days (m. p. 473 K). IR: 1681 cm−1 (CO). Crystals of (II) were also obtained from aqueous solution: IR 1702 cm−1 (CO).

Refinement top

Crystals of (I) are triclinic; space group P-1 was selected, and confirmed by the subsequent analysis. For (II), the space group P21/c was uniquely assigned from the systematic absences. All H atoms were located from difference maps. H atoms in the organic components were subsequently treated as riding atoms, with C—H distances of 0.99 Å, N—H distances of 0.88 Å and an O—H distance of 0.84 Å, and with Uiso(H) values of 1.2Ueq(C,N) or 1.5Ueq(O). H atoms in the water molecule were permitted to ride at the distances found from difference maps (O—H = 0.85 and 0.91 Å), with Uiso(H) values of 1.5Ueq(O). For both structures, several very intense low-angle reflections were rejected during the data processing because of incomplete profiles and/or detector saturation.

Computing details top

Data collection: COLLECT (Hooft, 1999) for (I); program (reference)? for (II). Cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT for (I); DENZO–SMN (Otwinowski & Minor, 1997) for (II). Data reduction: DENZO and COLLECT for (I); DENZO–SMN for (II). Program(s) used to solve structure: OSCAIL (McArdle, 2003) and SHELXS97 (Sheldrick, 1997) for (I); OSCAIL (McArdle , 2003) and SHELXS97 (Sheldrick, 1997) for (II). For both compounds, program(s) used to refine structure: OSCAIL and SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).

Figures top
[Figure 1] Fig. 1. The independent molecular components of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level, and atoms labelled with the suffixes A or B are at the symmetry positions (1 − x, −y, 1 − z) and (−x, 2 − y, −z), respectively.
[Figure 2] Fig. 2. Part of the crystal structure of (I), showing the formation of a [100] chain of rings built from 2,5-piperazinedione molecules only. For clarity, H atoms bonded to C atoms have been omitted. Atoms marked with an asterisk (*), a hash (#) or a dollar sign ($) are at the symmetry positions (2 − x, −y, 1 − z), (1 − x, −y, 1 − z) and (−1 + x, y, z), respectively.
[Figure 3] Fig. 3. Part of the crystal structure of (I), showing the formation of a [100] chain of edge-fused rings built from acid and water molecules only. Atoms marked with an asterisk (*), a hash (#) or a dollar sign ($) are at the symmetry positions (1 − x, 2 − y, −z), (−x, 2 − y, −z) and (1 + x, y, z), respectively.
[Figure 4] Fig. 4. A stereoview of part of the crystal structure of (I), showing the formation of a (012) sheet containing R12(5), R22(8), R44(8) and R54(15) rings. For clarity, H atoms bonded to C atoms have been omitted.
[Figure 5] Fig. 5. The molecule of (II), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level, and atoms labelled with the suffix A are at the symmetry position (2 − x, 1 − y, 2 − z).
[Figure 6] Fig. 6. A stereoview of part of the crystal structure of (II), showing the formation of a (11–1) sheet of R22(8) and R43(14) rings.
(I) 2,5-Piperazinedione–oxalic acid–water (1/1/2) top
Crystal data top
C4H6N2O2·C2H2O4·2H2OZ = 1
Mr = 240.18F(000) = 126
Triclinic, P1Dx = 1.583 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.1494 (7) ÅCell parameters from 1073 reflections
b = 6.1984 (8) Åθ = 3.0–27.5°
c = 7.3642 (9) ŵ = 0.15 mm1
α = 83.486 (6)°T = 120 K
β = 82.580 (8)°Plate, colourless
γ = 65.067 (7)°0.42 × 0.18 × 0.08 mm
V = 251.86 (6) Å3
Data collection top
Nonius KappaCCD?
diffractometer
1143 independent reflections
Radiation source: Bruker-Nonius FR91 rotating anode1043 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.048
Detector resolution: 9.091 pixels mm-1θmax = 27.6°, θmin = 3.7°
ϕ and ω scansh = 77
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
k = 88
Tmin = 0.931, Tmax = 0.988l = 99
4586 measured reflections
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)] = 0.042Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.136H-atom parameters constrained
S = 1.20 w = 1/[σ2(Fo2) + (0.0795P)2 + 0.0483P]
where P = (Fo2 + 2Fc2)/3
1143 reflections(Δ/σ)max < 0.001
74 parametersΔρmax = 0.41 e Å3
0 restraintsΔρmin = 0.32 e Å3
Crystal data top
C4H6N2O2·C2H2O4·2H2Oγ = 65.067 (7)°
Mr = 240.18V = 251.86 (6) Å3
Triclinic, P1Z = 1
a = 6.1494 (7) ÅMo Kα radiation
b = 6.1984 (8) ŵ = 0.15 mm1
c = 7.3642 (9) ÅT = 120 K
α = 83.486 (6)°0.42 × 0.18 × 0.08 mm
β = 82.580 (8)°
Data collection top
Nonius KappaCCD?
diffractometer
1143 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
1043 reflections with I > 2σ(I)
Tmin = 0.931, Tmax = 0.988Rint = 0.048
4586 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0420 restraints
wR(F2) = 0.136H-atom parameters constrained
S = 1.20Δρmax = 0.41 e Å3
1143 reflectionsΔρmin = 0.32 e Å3
74 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.64641 (18)0.66722 (18)0.20427 (14)0.0250 (3)
O20.78414 (17)0.21931 (18)0.35910 (14)0.0242 (3)
O110.28936 (17)0.94857 (18)0.04183 (14)0.0237 (3)
O120.07951 (18)0.72801 (18)0.13024 (15)0.0267 (3)
N10.7376 (2)0.0815 (2)0.53587 (16)0.0198 (3)
C20.6554 (2)0.1136 (2)0.42607 (18)0.0195 (3)
C30.3993 (2)0.2135 (2)0.3779 (2)0.0204 (3)
C110.1013 (2)0.9015 (2)0.05216 (18)0.0201 (3)
H10.88920.13660.55900.024*
H1A0.68290.51230.24320.038*
H1B0.76910.69460.16530.038*
H3A0.31640.38010.41400.024*
H3B0.40000.21700.24310.024*
H110.40050.83470.09280.036*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0198 (5)0.0210 (6)0.0346 (6)0.0098 (4)0.0062 (4)0.0063 (4)
O20.0179 (5)0.0232 (5)0.0337 (6)0.0117 (4)0.0058 (4)0.0070 (4)
O110.0197 (5)0.0248 (6)0.0292 (6)0.0123 (4)0.0079 (4)0.0077 (4)
O120.0215 (6)0.0226 (6)0.0368 (6)0.0114 (4)0.0068 (4)0.0090 (4)
N10.0148 (5)0.0198 (6)0.0260 (6)0.0090 (4)0.0040 (4)0.0038 (5)
C20.0175 (7)0.0193 (7)0.0228 (7)0.0090 (5)0.0028 (5)0.0008 (5)
C30.0165 (7)0.0205 (7)0.0249 (7)0.0093 (5)0.0041 (5)0.0046 (5)
C110.0184 (7)0.0205 (7)0.0221 (7)0.0091 (5)0.0019 (5)0.0007 (5)
Geometric parameters (Å, º) top
N1—C21.3192 (18)C11—O111.2982 (16)
N1—C3i1.4510 (19)C11—O121.2107 (17)
N1—H10.88C11—C11ii1.545 (3)
C2—O21.2497 (17)O11—H110.84
C2—C31.5042 (19)O1—H1A0.91
C3—H3A0.99O1—H1B0.85
C3—H3B0.99
C2—N1—C3i125.97 (12)N1i—C3—H3B108.6
C2—N1—H1117.0C2—C3—H3B108.6
C3i—N1—H1117.0H3A—C3—H3B107.6
O2—C2—N1122.14 (13)O12—C11—O11126.63 (13)
O2—C2—C3118.32 (12)O12—C11—C11ii122.26 (15)
N1—C2—C3119.54 (12)O11—C11—C11ii111.11 (14)
N1i—C3—C2114.48 (12)C11—O11—H11109.5
N1i—C3—H3A108.6H1A—O1—H1B113.6
C2—C3—H3A108.6
C3i—N1—C2—O2178.94 (13)O2—C2—C3—N1i179.08 (12)
C3i—N1—C2—C31.4 (2)N1—C2—C3—N1i1.2 (2)
Symmetry codes: (i) x+1, y, z+1; (ii) x, y+2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···O20.911.802.6971 (14)168
O1—H1B···O12iii0.851.992.8208 (15)167
O1—H1B···O11iv0.852.462.9565 (15)118
O11—H11···O10.841.692.5040 (14)164
N1—H1···O2v0.882.012.8807 (16)170
Symmetry codes: (iii) x+1, y, z; (iv) x+1, y+2, z; (v) x+2, y, z+1.
(II) 2,5-Piperazinedione top
Crystal data top
C4H6N2O2F(000) = 120
Mr = 114.11Dx = 1.646 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 508 reflections
a = 3.8967 (10) Åθ = 4.4–27.5°
b = 11.527 (3) ŵ = 0.13 mm1
c = 5.159 (2) ÅT = 120 K
β = 96.46 (2)°Plate, colourless
V = 230.26 (12) Å30.58 × 0.26 × 0.06 mm
Z = 2
Data collection top
Nonius KappaCCD
diffractometer
508 independent reflections
Radiation source: fine-focus sealed X-ray tube490 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.105
ϕ scans, and ω scans with κ offsetsθmax = 27.5°, θmin = 4.4°
Absorption correction: multi-scan
(SORTAV; Blessing, 1995, 1997)
h = 44
Tmin = 0.935, Tmax = 0.992k = 1414
2525 measured reflectionsl = 66
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)] = 0.067Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.206H-atom parameters constrained
S = 1.25 w = 1/[σ2(Fo2) + (0.1311P)2 + 0.0775P]
where P = (Fo2 + 2Fc2)/3
508 reflections(Δ/σ)max < 0.001
37 parametersΔρmax = 0.48 e Å3
0 restraintsΔρmin = 0.49 e Å3
Crystal data top
C4H6N2O2V = 230.26 (12) Å3
Mr = 114.11Z = 2
Monoclinic, P21/cMo Kα radiation
a = 3.8967 (10) ŵ = 0.13 mm1
b = 11.527 (3) ÅT = 120 K
c = 5.159 (2) Å0.58 × 0.26 × 0.06 mm
β = 96.46 (2)°
Data collection top
Nonius KappaCCD
diffractometer
508 independent reflections
Absorption correction: multi-scan
(SORTAV; Blessing, 1995, 1997)
490 reflections with I > 2σ(I)
Tmin = 0.935, Tmax = 0.992Rint = 0.105
2525 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0670 restraints
wR(F2) = 0.206H-atom parameters constrained
S = 1.25Δρmax = 0.48 e Å3
508 reflectionsΔρmin = 0.49 e Å3
37 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O20.5941 (4)0.63335 (11)0.6680 (2)0.0190 (6)
N10.8110 (4)0.45696 (13)0.7787 (3)0.0159 (6)
C20.7821 (4)0.56985 (18)0.8176 (3)0.0148 (6)
C30.9821 (5)0.62391 (14)1.0532 (4)0.0159 (7)
H10.69390.42810.63760.019*
H3A1.13660.68420.99390.019*
H3B0.81750.66311.15720.019*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O20.0226 (10)0.0126 (9)0.0206 (9)0.0006 (5)0.0028 (6)0.0012 (5)
N10.0191 (11)0.0114 (10)0.0165 (9)0.0000 (6)0.0010 (7)0.0005 (5)
C20.0158 (11)0.0122 (10)0.0169 (10)0.0012 (6)0.0042 (7)0.0017 (6)
C30.0168 (11)0.0107 (10)0.0198 (11)0.0014 (6)0.0001 (7)0.0001 (6)
Geometric parameters (Å, º) top
N1—C21.323 (3)C2—C31.503 (3)
N1—C3i1.454 (2)C3—H3A0.99
N1—H10.88C3—H3B0.99
C2—O21.241 (2)
C2—N1—C3i126.23 (15)N1i—C3—C2114.75 (15)
C2—N1—H1116.9N1i—C3—H3A108.6
C3i—N1—H1116.9C2—C3—H3A108.6
O2—C2—N1122.68 (17)N1i—C3—H3B108.6
O2—C2—C3118.31 (17)C2—C3—H3B108.6
N1—C2—C3119.01 (16)H3A—C3—H3B107.6
C3i—N1—C2—O2178.40 (14)O2—C2—C3—N1i178.55 (13)
C3i—N1—C2—C31.1 (3)N1—C2—C3—N1i1.0 (3)
Symmetry code: (i) x+2, y+1, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O2ii0.881.962.840 (2)176
C3—H3B···O2iii0.992.513.266 (3)133
Symmetry codes: (ii) x+1, y+1, z+1; (iii) x, y+3/2, z+1/2.

Experimental details

(I)(II)
Crystal data
Chemical formulaC4H6N2O2·C2H2O4·2H2OC4H6N2O2
Mr240.18114.11
Crystal system, space groupTriclinic, P1Monoclinic, P21/c
Temperature (K)120120
a, b, c (Å)6.1494 (7), 6.1984 (8), 7.3642 (9)3.8967 (10), 11.527 (3), 5.159 (2)
α, β, γ (°)83.486 (6), 82.580 (8), 65.067 (7)90, 96.46 (2), 90
V3)251.86 (6)230.26 (12)
Z12
Radiation typeMo KαMo Kα
µ (mm1)0.150.13
Crystal size (mm)0.42 × 0.18 × 0.080.58 × 0.26 × 0.06
Data collection
DiffractometerNonius KappaCCD?
diffractometer
Nonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Multi-scan
(SORTAV; Blessing, 1995, 1997)
Tmin, Tmax0.931, 0.9880.935, 0.992
No. of measured, independent and
observed [I > 2σ(I)] reflections
4586, 1143, 1043 2525, 508, 490
Rint0.0480.105
(sin θ/λ)max1)0.6520.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.136, 1.20 0.067, 0.206, 1.25
No. of reflections1143508
No. of parameters7437
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.41, 0.320.48, 0.49

Computer programs: COLLECT (Hooft, 1999), program (reference)?, DENZO (Otwinowski & Minor, 1997) and COLLECT, DENZO–SMN (Otwinowski & Minor, 1997), DENZO and COLLECT, DENZO–SMN, OSCAIL (McArdle, 2003) and SHELXS97 (Sheldrick, 1997), OSCAIL (McArdle , 2003) and SHELXS97 (Sheldrick, 1997), OSCAIL and SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), SHELXL97 and PRPKAPPA (Ferguson, 1999).

Selected bond lengths (Å) for (I) top
N1—C21.3192 (18)C11—O111.2982 (16)
N1—C3i1.4510 (19)C11—O121.2107 (17)
C2—O21.2497 (17)C11—C11ii1.545 (3)
C2—C31.5042 (19)
Symmetry codes: (i) x+1, y, z+1; (ii) x, y+2, z.
Hydrogen-bond geometry (Å, º) for (I) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···O20.911.802.6971 (14)168
O1—H1B···O12iii0.851.992.8208 (15)167
O1—H1B···O11iv0.852.462.9565 (15)118
O11—H11···O10.841.692.5040 (14)164
N1—H1···O2v0.882.012.8807 (16)170
Symmetry codes: (iii) x+1, y, z; (iv) x+1, y+2, z; (v) x+2, y, z+1.
Hydrogen-bond geometry (Å, º) for (II) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O2i0.881.962.840 (2)176
C3—H3B···O2ii0.992.513.266 (3)133
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+3/2, z+1/2.
 

Acknowledgements

X-ray data were collected at the EPSRC X-ray Crystallographic Service, University of Southampton, England; the authors thank the staff for all their help and advice. JNL thanks NCR Self-Service, Dundee, for grants which have provided computing facilities for this work.

References

First citationAllen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.  CrossRef Web of Science Google Scholar
First citationBernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.  CrossRef CAS Web of Science Google Scholar
First citationBlessing, R. H. (1995). Acta Cryst. A51, 33–37.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationBlessing, R. H. (1997). J. Appl. Cryst. 30, 421–426.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationDegeilh, R. & Marsh, R. E. (1959). Acta Cryst. 12, 1007–1014.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationDelaplane, R. G. & Ibers, J. A. (1969). Acta Cryst. B25, 2423–2437.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationFerguson, G. (1999). PRPKAPPA. University of Guelph, Canada.  Google Scholar
First citationHooft, R. W. W. (1999). COLLECT. Nonius BV, Delft, The Netherlands.  Google Scholar
First citationIwasaki, F. F., Iwasaki, H. & Saito, Y. (1967). Acta Cryst. 23, 64–70.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationKartha, G., Varughese, K. I. & Lu, C. T. (1981). Acta Cryst. B37, 1798–1800.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationLuo, T. J. M. & Palmore, G. T. R. (2002). Cryst. Growth Des. 2, 337–350.  Web of Science CSD CrossRef CAS Google Scholar
First citationMcArdle, P. (2003). OSCAIL for Windows. Version 10. Crystallography Centre, Chemistry Department, NUI Galway, Ireland.  Google Scholar
First citationNonius (1997). KappaCCD Server Software. Windows 3.11 Version. Nonius BV, Delft, The Netherlands.  Google Scholar
First citationOtwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.  Google Scholar
First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.  Google Scholar
First citationSpek, A. L. (2003). J. Appl. Cryst. 36, 7–13.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationVarughese, K. I. & Kartha, G. (1982). Acta Cryst. B38, 301–302.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar

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