Crystal structure of poly[[μ2-di­aqua-di­aqua-μ2-l-proline-κ2O:O′-strontium] dibromide]

Sathiskumar, S.; Balakrishnan, T.; Ramamurthi, K.; Thamotharan, S.

doi:10.1107/S2056989015017302

research communications

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 71| Part 10| October 2015| Pages 1199-1202

doi:10.1107/S2056989015017302

Open

access

Crystal structure of poly[[μ₂-diaqua-diaqua-μ₂-L-proline-κ²O:O′-strontium] dibromide]

Selladurai Sathiskumar,^a Thangavelu Balakrishnan,^a ^* Kandasamy Ramamurthi ^b and Subbiah Thamotharan ^c ^*

^aCrystal Growth Laboratory, PG and Research Department of Physics, Periyar EVR College (Autonomous), Tiruchirappalli 620 023, India, ^bCrystal Growth and Thin Film Laboratory, Department of Physics and Nanotechnology, SRM University, Kattankulathur 603 203, India, and ^cBiomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA University, Thanjavur 613 401, India
^*Correspondence e-mail: balacrystalgrowth@gmail.com, thamu@scbt.sastra.edu

Edited by G. Smith, Queensland University of Technology, Australia (Received 2 September 2015; accepted 16 September 2015; online 26 September 2015)

In the title coordination polymer, {[Sr(C₅H₉NO₂)(H₂O)₄]Br₂}_n, the proline molecule exists in a zwitterionic form with one of the ring C atoms disordered over two sites [site-occupancy factors = 0.57 (6):0.43 (6)]. The Sr^II ion is nine-coordinated by six water O atoms, two monodentate and two μ₂-bridging, and three carboxylate O atoms of the proline ligands, with two bridging [Sr—O range = 2.524 (4)–2.800 (5) Å]. In the crystal, there is no direct interaction between the proline molecules. However, the proline and water molecules associate with the bromide counter-anions through a number of intermolecular O—H⋯Br and N—H⋯Br hydrogen-bonding interactions, giving a three-dimensional supramolecular structure.

Keywords: crystal structure; proline; amino acid; strontium coordination polymer; N/O—H⋯Br hydrogen bonds.

CCDC reference: 1424731

1. Chemical context

The study of coordination polymers has been an area of rapid development in recent years due to their interesting structures and their wide range of applications as functional materials (Lyhs et al., 2012 ). Reports of the crystal structures of alkaline earth metal ions combined with anions of amino acids are very limited. As part of our ongoing investigations of the crystal and molecular structures of a series of metal complexes generated from amino acids (Revathi et al., 2015 ; Sathiskumar et al., 2015a ,b ; Balakrishnan et al., 2013 ), we report here the crystal structure of a polymeric strontium–proline complex, {[Sr(C₅H₉NO₂)(H₂O)₄]²⁺ 2(Br⁻)}_n, (I).

2. Structural commentary

The asymmetric unit of the title complex (I) contains one Sr²⁺ ion, one bridging proline ligand and four water molecules, two of which are monodentate and two bridging, and two bromide counter-anions (Fig. 1). In (I), the bond lengths involving the carboxylate atoms and the protonation of the amino group suggest that the proline molecule exists in a zwitterionic form. The Sr^II ion is nine-coordinated by six water oxygen atoms [Sr—O = 2.582 (6)–2.707 (5)Å] and three carboxylate oxygen atoms of zwitterionic proline ligands [Sr—O = 2.524 (4)–2.800 (4) Å; Table 1]. In the strontium–glycine complex, the Sr—O (water) and Sr—O(carboxylate) distances ranges are 2.526 (4)–2.661 (2) and 2.605 (2)–2.703 (2) Å, respectively (Revathi et al., 2015). In (I), one of the carbon atoms (C4) of the pyrrolidine ring is disordered over two sites. In the major component of the pyrrolidine ring, there is a twist conformation on the C2—C5 bond with a pseudo-rotation angle Δ = 40.1 (14)° and a maximum torsion angle φ_m = 43.8 (10)° for the atom sequence N1–C2–C5–C4A–C3 (Rao et al., 1981 ). In the minor component, the pyrrolidine ring exhibits an envelope conformation on N1 with a pseudo-rotation angle Δ = 341.5 (19)° and a maximum torsion angle φ_m = 36.0 (9)° for the atom sequence N1–C2–C5–C4B–C3 (Rao et al., 1981). As shown in Fig. 2, the title complex forms a coordination polymeric chain that lies parallel to the a axis. Adjacent Sr^II ions are separated by 3.9387 (7) Å within a chain.

Table 1
Selected bond lengths (Å)

Sr1—O1	2.524 (4)	Sr1—O2ⁱ	2.728 (4)
Sr1—O3	2.625 (6)	Sr1—O3ⁱⁱ	2.707 (6)
Sr1—O4	2.630 (6)	Sr1—O4ⁱⁱ	2.651 (5)
Sr1—O5	2.593 (5)	Sr1—O2ⁱⁱⁱ	2.800 (5)
Sr1—O6	2.582 (6)
Symmetry codes: (i) x+1, y, z; (ii) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ ; (iii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ .

Figure 1
The coordination sphere of Sr²⁺ in the crystal structure of (I)

. Only the major components of the disordered proline ligands are shown. Displacement ellipsoids are drawn at the 50% probability level. For symmetry codes, see Table 1

Figure 2
The Sr–water coordination polymeric chain substructure of (I)

, with peripheral water O—H⋯Br hydrogen bonds shown as dashed lines.

3. Supramolecular features

The crystal structure of (I), is stabilized by intermolecular N—H⋯Br and O—H⋯Br hydrogen bonds (Table 2). One of the characteristic features observed in amino acid complexes is the head-to-tail sequence in which amino acids are self-associated through their amino and carboxylate groups (Sharma et al., 2006 ; Selvaraj et al., 2007 ; Balakrishnan et al., 2013; Revathi et al., 2015). In the crystal structure of the L-proline lithium bromide monohydrate complex, there is a head-to-tail sequence observed (Sathiskumar et al., 2015a). In contrast, there is no direct hydrogen-bonding interaction between the proline molecules in (I).

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯Br2ⁱ	0.90 (6)	2.52 (5)	3.374 (7)	159 (6)
N1—H1B⋯Br3ⁱ	0.90 (7)	2.40 (7)	3.240 (7)	156 (8)
O3—H3C⋯Br3^iv	0.84 (7)	2.63 (7)	3.440 (6)	163 (7)
O3—H3D⋯Br2^v	0.84 (7)	2.54 (7)	3.376 (6)	172 (5)
O4—H4E⋯Br2^vi	0.85 (6)	2.47 (7)	3.281 (6)	162 (7)
O4—H4F⋯Br3^vii	0.83 (6)	2.52 (6)	3.347 (6)	174 (6)
O5—H5C⋯Br2ⁱ	0.86 (5)	2.54 (5)	3.369 (6)	164 (6)
O5—H5D⋯Br3^vii	0.84 (6)	2.48 (6)	3.304 (6)	166 (6)
O6—H6C⋯Br2^v	0.83 (6)	2.58 (6)	3.393 (6)	167 (5)
O6—H6D⋯Br3ⁱ	0.85 (7)	2.56 (6)	3.378 (6)	162 (7)
Symmetry codes: (i) x+1, y, z; (iv) $[-x+{\script{3\over 2}}, -y+1, z+{\script{1\over 2}}]$ ; (v) $[-x+2, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (vi) $[-x+{\script{3\over 2}}, -y, z+{\script{1\over 2}}]$ ; (vii) $[-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

As shown in Fig. 3, two water molecules and two bromide anions along with Sr²⁺ ions generate a hydrogen-bonded sheet which lies parallel to the a axis. Within this sheet, two Sr²⁺ ions and two water oxygens form a cyclic motif. Water molecules (O3 and O4) interconnect the bromide anions, forming a chain. In (I), two molecules (O5 and O6) act as donors for intermolecular O—H⋯Br hydrogen bonds. These hydrogen bonds generate a cyclic dibromide motif similar to that observed in a related structure (Revathi et al., 2015). Adjacent dibromide motifs in (I), which run parallel to the b axis, are interconnected by proline ligands through intermolecular N—H⋯Br hydrogen bonds on both sides (Fig. 3). Adjacent supramolecular arrangements of cyclic dibromide⋯proline⋯cyclic dibromide motifs are interlinked further by water molecules (O3 and O4) through O—H⋯Br hydrogen bonds. This entire arrangement forms a butterfly-like structure. The overall hydrogen-bonded supramolecular structure (Fig. 4) is three-dimensional.

Figure 3
The butterfly-like supramolecular arrangements generated by intermolecular N—H⋯Br and O—H⋯Br hydrogen bonds. Only atoms involved in hydrogen-bonding interactions are labelled.

Figure 4
The crystal packing of (I)

viewed along the a axis, with hydrogen bonds shown as dashed lines. C-bound H atoms have been omitted for clarity.

4. Synthesis and crystallization

Single crystals of the title complex were obtained by slow evaporation from an aqueous solution of L-proline and strontium bromide hexahydrate in a 1:1 stoichiometric molar ratio at 306 K. The prepared solution was stirred well and filtered. The resultant filtered solution was left undisturbed to allow evaporation. After 15 days, colourless prismatic crystals were harvested.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. One of the carbon (C4) atoms of the pyrrolidine ring appears to be disordered over two sites. These positions were defined for this atom and constrained refinement of the site-occupation factors led to a value of 0.57 (6) for the major component. The positions of amino and water H atoms were located from difference Fourier maps. Further, the O—H distances in the water molecules were restrained to 0.85 (2) Å. The N—H distances of amino group were also restrained, to 0.89 (2) Å. The remaining hydrogen atoms were placed in geometrically idealized positions (C—H = 0.97 Å with U_iso(H) = 1.2U_eq(C) and were constrained to ride on their parent atom. The Flack absolute structure parameter was determined to be 0.008 (8) (788 Friedel pairs; Parsons et al., 2013 ), indicating an S configuration for C2, consistent with that for the parent L-proline (Kayushina & Vainshtein, 1965 ).

Table 3
Experimental details

Crystal data
Chemical formula	[Sr(C₅H₉NO₂)(H₂O)₄]Br₂
M_r	434.63
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	296
a, b, c (Å)	6.7079 (4), 12.9125 (9), 15.4499 (11)
V (Å³)	1338.20 (16)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	10.01
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	Bruker Kappa APEXII CCD
Absorption correction	Multi-scan (SABABS; Bruker, 2004 )
T_min, T_max	0.26, 0.44
No. of measured, independent and observed [I > 2σ(I)] reflections	14183, 2345, 2081
R_int	0.068
(sin θ/λ)_max (Å⁻¹)	0.594

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.032, 0.063, 1.07
No. of reflections	2345
No. of parameters	186
No. of restraints	26
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.60, −0.86
Absolute structure	Flack x determined using 788 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013)
Absolute structure parameter	0.008 (8)
Computer programs: APEX2, SAINT and XPREP (Bruker, 2004), SIR92 (Altomare et al., 1993 ), SHELXL2014 (Sheldrick, 2015 ), PLATON (Spek, 2009 ) and Mercury (Macrae et al., 2008 ).

Supporting information

CCDC reference: 1424731

Crystal structure: contains datablock I. DOI: 10.1107/S2056989015017302/zs2346sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015017302/zs2346Isup2.hkl

checkCIF report

Chemical context top

The study of coordination polymers has been an area of rapid development in recent years due to their interesting structures and their wide range of applications as functional materials (Lyhs et al., 2012). Reports of the crystal structures of alkaline earth metal ions combined with anions of amino acids are very limited. As part of our ongoing investigations of the crystal and molecular structures of a series of metal complexes generated from amino acids (Revathi et al.,2015; Sathiskumar et al., 2015a,b; Balakrishnan et al., 2013), we report here the crystal structure of a polymeric strontium–proline complex, {[Sr(C₅H₉NO₂)(H₂O)₄]²⁺ 2(Br^-)}_n, (I).

Structural commentary top

The asymmetric unit of the title complex (I) contains one Sr ion, one bridging proline ligand and four water molecules, two of which are monodentate and two bridging, and two bromide counter-anions (Fig. 1). In (I), the bond lengths involving the carboxylate atoms and the protonation of the amino group suggest that the proline molecule exists in a zwitterionic form. The Sr^II ion is nine-coordinated by six water oxygen atoms [Sr—O = 2.582 (6)–2.707 (5)Å] and three carboxylate oxygen atoms of zwitterionic proline ligands [Sr—O = 2.524 (4)–2.800 (4) Å; Table 1]. In the strontium–glycine complex, the Sr—O (water) and Sr—O(carboxylate) distances ranges are 2.526 (4)–2.661 (2) and 2.605 (2)–2.703 (2)Å, respectively (Revathi et al., 2015). In (I), one of the carbon atoms (C4) of the pyrrolidine ring is disordered over two sites. In the major component of the pyrrolidine ring, there is a twist conformation on the C2—C5 bond with a pseudo-rotation angle Δ = 40.1 (14)° and a maximum torsion angle φ_m = 43.8 (10)° for the atom sequence N1–C2–C5–C4A–C3 (Rao et al., 1981). In the minor component, the pyrrolidine ring exhibits an envelope conformation on N1 with a pseudo-rotation angle Δ = 341.5 (19)° and a maximum torsion angle φ_m = 36.0 (9)° for the atom sequence N1–C2–C5–C4B–C3 (Rao et al., 1981). As shown in Fig. 2, the title complex forms a coordination polymeric chain that lies parallel to the a axis. Adjacent Sr^II ions are separated by 3.9387 (7) Å within a chain.

Supramolecular features top

The crystal structure of (I), is stabilized by intermolecular N—H···Br and O—H···Br hydrogen bonds (Table 2). One of the characteristic features observed in amino acid complexes is the head-to-tail sequence in which amino acids are self-associated through their amino and carboxylate groups (Sharma et al., 2006; Selvaraj et al., 2007; Balakrishnan et al., 2013; Revathi et al., 2015). In the crystal structure of the L-proline lithium bromide monohydrate complex, there is a head-to-tail sequence observed (Sathiskumar et al., 2015a). In contrast, there is no direct hydrogen-bonding interaction between the proline molecules in (I).

As shown in Fig. 3, two water molecules and two bromide anions along with Sr ions generate a hydrogen-bonded sheet which lies parallel to the a axis. Within this sheet, two Sr ions and two water oxygens form a cyclic motif. Water molecules (O3 and O4) interconnect the bromide anions, forming a chain. In (I), two molecules (O5 and O6) act as donors for intermolecular O—H···Br hydrogen bonds. These hydrogen bonds generate a cyclic dibromide motif similar to that observed in a related structure (Revathi et al., 2015). Adjacent dibromide motifs in (I), which run parallel to the b axis, are interconnected by proline ligands through intermolecular N—H···Br hydrogen bonds on both sides (Fig. 3). Adjacent supramolecular arrangements of cyclic dibromide···proline···cyclic dibromide motifs are interlinked further by water molecules (O3 and O4) through O—H···Br hydrogen bonds. This entire arrangement forms a butterfly-like structure. The overall hydrogen-bonded supramolecular structure (Fig. 4) is three-dimensional.

Synthesis and crystallization top

Single crystals of the title complex were obtained by slow evaporation from an aqueous solution of L-proline and strontium bromide hexahydrate in a 1:1 stoichiometric molar ratio at room temperature (306 K). The prepared solution was stirred well and filtered. The resultant filtered solution was left undisturbed to allow evaporation. After 15 days, colourless prismatic crystals were harvested.

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 3. One of the carbon (C4) atoms of the pyrrolidine ring appears to be disordered over two sites. These positions were defined for this atom and constrained refinement of the site-occupation factors led to a value of 0.57 (6) for the major component. The positions of amino and water H atoms were located from difference Fourier maps. Further, the O—H distances in the water molecules were restrained to 0.85 (2) Å. The N—H distances of amino group were also restrained, to 0.89 (2) Å. The remaining hydrogen atoms were placed in geometrically idealized positions (C—H = 0.97 Å with U_iso(H) = 1.2U_eq(C) and were constrained to ride on their parent atom. The Flack absolute structure parameter was determined to be 0.008 (8) (788 Friedel pairs; Parsons et al., 2013), indicating an S configuration for C2, consistent with that for the parent L-proline (Kayushina & Vainshtein, 1965).

Related literature top

For related literature, see: Balakrishnan et al. (2013); Kayushina & Vainshtein (1965); Lyhs et al. (2012); Parsons et al. (2013); Rao et al. (1981); Revathi et al. (2015); Sathiskumar et al. (2015a, 2015b); Selvaraj et al. (2007); Sharma et al. (2006).

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

Figures top

	Fig. 1. The coordination sphere of Sr²⁺ in the crystal structure of (I). Only the major components of the proline ligands are shown. Displacement ellipsoids are drawn at the 50% probability level. For symmetry codes, see Table 1.
	Fig. 2. The Sr–water coordination polymeric chain substructure of (I), with peripheral water O—H···Br hydrogen bonds shown as dashed lines.
	Fig. 3. The butterfly-like supramolecular arrangements generated by intermolecular N—H···Br and O—H···Br hydrogen bonds. Only atoms involved in hydrogen-bonding interactions are labelled.
	Fig. 4. The crystal packing of (I) viewed along the a axis, with hydrogen bonds shown as dashed lines. C-bound H atoms have been omitted for clarity.

Poly[[µ₂-diaqua-diaqua-µ₂-L-proline-κ²O:O'-\ strontium] dibromide] top

Crystal data top

[Sr(C₅H₉NO₂)(H₂O)₄]Br₂	D_x = 2.157 Mg m⁻³
M_r = 434.63	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P2₁2₁2₁	Cell parameters from 7063 reflections
a = 6.7079 (4) Å	θ = 2.6–28.5°
b = 12.9125 (9) Å	µ = 10.01 mm⁻¹
c = 15.4499 (11) Å	T = 296 K
V = 1338.20 (16) Å³	Block, brown
Z = 4	0.15 × 0.10 × 0.10 mm
F(000) = 840

Data collection top

Bruker Kappa APEXII CCD diffractometer	2081 reflections with I > 2σ(I)
Radiation source: Sealed tube	R_int = 0.068
ω nd φ scan	θ_max = 25.0°, θ_min = 2.6°
Absorption correction: multi-scan (SABABS; Bruker, 2004)	h = −7→7
T_min = 0.26, T_max = 0.44	k = −15→15
14183 measured reflections	l = −18→18
2345 independent reflections

Refinement top

Refinement on F²	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.032	w = 1/[σ²(F_o²) + (0.0267P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.063	(Δ/σ)_max < 0.001
S = 1.07	Δρ_max = 0.60 e Å⁻³
2345 reflections	Δρ_min = −0.86 e Å⁻³
186 parameters	Absolute structure: Flack x determined using 788 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
26 restraints	Absolute structure parameter: 0.008 (8)

Crystal data top

[Sr(C₅H₉NO₂)(H₂O)₄]Br₂	V = 1338.20 (16) Å³
M_r = 434.63	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 6.7079 (4) Å	µ = 10.01 mm⁻¹
b = 12.9125 (9) Å	T = 296 K
c = 15.4499 (11) Å	0.15 × 0.10 × 0.10 mm

Data collection top

Bruker Kappa APEXII CCD diffractometer	2345 independent reflections
Absorption correction: multi-scan (SABABS; Bruker, 2004)	2081 reflections with I > 2σ(I)
T_min = 0.26, T_max = 0.44	R_int = 0.068
14183 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.032	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.063	Δρ_max = 0.60 e Å⁻³
S = 1.07	Δρ_min = −0.86 e Å⁻³
2345 reflections	Absolute structure: Flack x determined using 788 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
186 parameters	Absolute structure parameter: 0.008 (8)
26 restraints

Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Sr1	1.34882 (8)	0.24302 (5)	0.43342 (4)	0.0174 (2)
O1	1.0492 (6)	0.2322 (4)	0.3350 (3)	0.0257 (16)
O2	0.7439 (6)	0.2420 (4)	0.3916 (3)	0.0243 (16)
O3	1.5725 (8)	0.3885 (5)	0.5016 (4)	0.0243 (19)
O4	1.5819 (8)	0.1162 (4)	0.5200 (4)	0.0213 (17)
O5	1.3443 (9)	0.0648 (4)	0.3561 (4)	0.035 (2)
O6	1.3860 (9)	0.3899 (5)	0.3212 (4)	0.038 (2)
N1	0.9404 (8)	0.2529 (6)	0.1734 (4)	0.026 (2)
C1	0.8660 (9)	0.2426 (5)	0.3307 (4)	0.018 (2)
C2	0.7837 (9)	0.2600 (6)	0.2411 (4)	0.021 (2)
C3	0.8370 (12)	0.2347 (7)	0.0890 (5)	0.042 (3)
C4A	0.623 (2)	0.211 (3)	0.1117 (11)	0.034 (7)	0.57 (6)
C5	0.6277 (12)	0.1840 (7)	0.2082 (5)	0.042 (3)
C4B	0.660 (5)	0.167 (3)	0.1117 (13)	0.035 (8)	0.43 (6)
Br2	0.18627 (12)	0.02641 (6)	0.15165 (6)	0.0389 (3)
Br3	0.22307 (13)	0.44596 (7)	0.11973 (6)	0.0466 (3)
H1A	1.024 (9)	0.199 (4)	0.180 (5)	0.02 (2)*
H1B	1.033 (10)	0.303 (5)	0.175 (6)	0.05 (3)*
H3C	1.522 (13)	0.429 (5)	0.538 (4)	0.06 (3)*
H3D	1.622 (13)	0.422 (5)	0.460 (4)	0.07 (4)*
H4E	1.532 (12)	0.085 (5)	0.563 (3)	0.05 (3)*
H4F	1.640 (10)	0.075 (4)	0.487 (4)	0.04 (3)*
H5C	1.281 (10)	0.060 (6)	0.308 (3)	0.06 (3)*
H5D	1.450 (7)	0.030 (6)	0.353 (5)	0.06 (3)*
H6C	1.478 (8)	0.432 (5)	0.327 (5)	0.03 (3)*
H6D	1.319 (11)	0.402 (7)	0.276 (4)	0.09 (4)*
H31	0.89720	0.17700	0.05850	0.0500*	0.57 (6)
H32	0.84480	0.29580	0.05270	0.0500*	0.57 (6)
H41	0.57440	0.15290	0.07800	0.0410*	0.57 (6)
H42	0.53890	0.27050	0.10120	0.0410*	0.57 (6)
H51	0.49920	0.19560	0.23530	0.0500*	0.57 (6)
H52	0.66830	0.11280	0.21770	0.0500*	0.57 (6)
H2	0.72630	0.32970	0.23900	0.0250*
H33	0.92450	0.19970	0.04850	0.0500*	0.43 (6)
H34	0.79360	0.29960	0.06370	0.0500*	0.43 (6)
H43	0.68850	0.09490	0.09960	0.0420*	0.43 (6)
H44	0.54310	0.18790	0.07910	0.0420*	0.43 (6)
H53	0.49510	0.21140	0.21840	0.0500*	0.43 (6)
H54	0.63970	0.11870	0.23880	0.0500*	0.43 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sr1	0.0142 (3)	0.0215 (4)	0.0165 (3)	0.0003 (3)	−0.0010 (3)	0.0006 (3)
O1	0.017 (2)	0.041 (3)	0.019 (3)	0.006 (2)	−0.001 (2)	−0.003 (3)
O2	0.024 (2)	0.033 (3)	0.016 (3)	0.004 (3)	0.004 (2)	0.002 (3)
O3	0.025 (3)	0.029 (3)	0.019 (4)	0.000 (2)	0.000 (3)	−0.003 (3)
O4	0.024 (3)	0.024 (3)	0.016 (3)	0.000 (2)	0.003 (3)	0.000 (3)
O5	0.033 (3)	0.044 (4)	0.029 (4)	0.006 (3)	−0.002 (3)	−0.010 (3)
O6	0.034 (4)	0.043 (4)	0.037 (4)	−0.012 (3)	−0.011 (3)	0.017 (3)
N1	0.022 (3)	0.035 (4)	0.022 (4)	−0.005 (4)	0.000 (3)	0.004 (4)
C1	0.025 (4)	0.011 (3)	0.017 (4)	−0.001 (3)	−0.003 (3)	−0.004 (3)
C2	0.024 (3)	0.026 (4)	0.013 (4)	0.005 (4)	0.002 (3)	0.000 (4)
C3	0.052 (5)	0.059 (6)	0.015 (4)	0.000 (5)	−0.001 (4)	−0.001 (4)
C4A	0.036 (10)	0.041 (15)	0.025 (9)	0.001 (8)	−0.007 (7)	−0.014 (9)
C5	0.035 (5)	0.066 (6)	0.025 (5)	−0.025 (4)	−0.006 (4)	−0.004 (5)
C4B	0.033 (13)	0.042 (17)	0.030 (11)	−0.010 (13)	0.005 (10)	−0.023 (11)
Br2	0.0357 (5)	0.0379 (5)	0.0432 (5)	0.0057 (4)	−0.0102 (4)	−0.0197 (4)
Br3	0.0505 (6)	0.0484 (6)	0.0409 (6)	−0.0239 (4)	−0.0107 (4)	0.0197 (5)

Geometric parameters (Å, º) top

Sr1—O1	2.524 (4)	N1—H1A	0.90 (6)
Sr1—O3	2.625 (6)	N1—H1B	0.90 (7)
Sr1—O4	2.630 (6)	C1—C2	1.507 (9)
Sr1—O5	2.593 (5)	C2—C5	1.522 (11)
Sr1—O6	2.582 (6)	C3—C4A	1.509 (17)
Sr1—O2ⁱ	2.728 (4)	C3—C4B	1.52 (4)
Sr1—O3ⁱⁱ	2.707 (6)	C4A—C5	1.53 (2)
Sr1—O4ⁱⁱ	2.651 (5)	C4B—C5	1.52 (2)
Sr1—O2ⁱⁱⁱ	2.800 (5)	C2—H2	0.9800
O1—C1	1.238 (7)	C3—H31	0.9700
O2—C1	1.248 (8)	C3—H32	0.9700
O3—H3C	0.84 (7)	C3—H33	0.9700
O3—H3D	0.84 (7)	C3—H34	0.9700
O4—H4E	0.85 (6)	C4A—H41	0.9700
O4—H4F	0.83 (6)	C4A—H42	0.9700
O5—H5D	0.84 (6)	C4B—H43	0.9700
O5—H5C	0.86 (5)	C4B—H44	0.9700
O6—H6D	0.85 (7)	C5—H51	0.9700
O6—H6C	0.83 (6)	C5—H54	0.9700
N1—C3	1.496 (10)	C5—H52	0.9700
N1—C2	1.486 (8)	C5—H53	0.9700

O1—Sr1—O3	137.44 (18)	Sr1—O6—H6D	130 (6)
O1—Sr1—O4	138.19 (17)	Sr1—O6—H6C	119 (5)
O1—Sr1—O5	70.37 (18)	H6C—O6—H6D	111 (8)
O1—Sr1—O6	73.32 (18)	C2—N1—C3	107.2 (5)
O1—Sr1—O2ⁱ	129.10 (14)	C3—N1—H1B	117 (6)
O1—Sr1—O3ⁱⁱ	69.11 (17)	H1A—N1—H1B	97 (5)
O1—Sr1—O4ⁱⁱ	70.35 (17)	C2—N1—H1A	114 (5)
O1—Sr1—O2ⁱⁱⁱ	112.66 (13)	C2—N1—H1B	115 (5)
O3—Sr1—O4	84.36 (18)	C3—N1—H1A	105 (5)
O3—Sr1—O5	145.76 (18)	O1—C1—C2	115.4 (5)
O3—Sr1—O6	71.85 (19)	O2—C1—C2	117.0 (5)
O2ⁱ—Sr1—O3	62.82 (16)	O1—C1—O2	127.6 (6)
O3—Sr1—O3ⁱⁱ	133.75 (19)	N1—C2—C5	102.2 (6)
O3—Sr1—O4ⁱⁱ	77.67 (17)	N1—C2—C1	112.2 (5)
O2ⁱⁱⁱ—Sr1—O3	72.95 (16)	C1—C2—C5	117.6 (6)
O4—Sr1—O5	71.86 (18)	N1—C3—C4B	104.6 (10)
O4—Sr1—O6	137.87 (18)	N1—C3—C4A	105.7 (8)
O2ⁱ—Sr1—O4	62.60 (16)	C3—C4A—C5	104.7 (10)
O3ⁱⁱ—Sr1—O4	80.08 (17)	C3—C4B—C5	104.8 (19)
O4—Sr1—O4ⁱⁱ	133.67 (19)	C2—C5—C4A	101.1 (12)
O2ⁱⁱⁱ—Sr1—O4	72.62 (16)	C2—C5—C4B	108.8 (15)
O5—Sr1—O6	110.10 (19)	N1—C2—H2	108.00
O2ⁱ—Sr1—O5	84.14 (17)	C1—C2—H2	108.00
O3ⁱⁱ—Sr1—O5	66.80 (19)	C5—C2—H2	108.00
O4ⁱⁱ—Sr1—O5	136.53 (18)	N1—C3—H31	111.00
O2ⁱⁱⁱ—Sr1—O5	120.21 (17)	N1—C3—H32	111.00
O2ⁱ—Sr1—O6	75.56 (17)	N1—C3—H33	111.00
O3ⁱⁱ—Sr1—O6	140.90 (18)	N1—C3—H34	111.00
O4ⁱⁱ—Sr1—O6	75.16 (19)	C4A—C3—H31	111.00
O2ⁱⁱⁱ—Sr1—O6	128.45 (18)	C4A—C3—H32	111.00
O2ⁱ—Sr1—O3ⁱⁱ	138.60 (17)	H31—C3—H32	109.00
O2ⁱ—Sr1—O4ⁱⁱ	136.37 (16)	C4B—C3—H33	111.00
O2ⁱ—Sr1—O2ⁱⁱⁱ	118.24 (13)	C4B—C3—H34	111.00
O3ⁱⁱ—Sr1—O4ⁱⁱ	82.36 (17)	H33—C3—H34	109.00
O2ⁱⁱⁱ—Sr1—O3ⁱⁱ	60.87 (16)	C3—C4A—H41	111.00
O2ⁱⁱⁱ—Sr1—O4ⁱⁱ	61.37 (16)	C3—C4A—H42	111.00
Sr1—O1—C1	144.8 (4)	C5—C4A—H41	111.00
Sr1^iv—O2—C1	144.7 (4)	C5—C4A—H42	111.00
Sr1ⁱⁱ—O2—C1	124.2 (4)	H41—C4A—H42	109.00
Sr1^iv—O2—Sr1ⁱⁱ	90.87 (13)	H43—C4B—H44	109.00
Sr1—O3—Sr1ⁱⁱⁱ	95.2 (2)	C3—C4B—H44	111.00
Sr1—O4—Sr1ⁱⁱⁱ	96.47 (17)	C5—C4B—H43	111.00
H3C—O3—H3D	111 (6)	C3—C4B—H43	111.00
Sr1ⁱⁱⁱ—O3—H3C	115 (5)	C5—C4B—H44	111.00
Sr1ⁱⁱⁱ—O3—H3D	110 (5)	C2—C5—H52	112.00
Sr1—O3—H3C	119 (6)	C2—C5—H53	110.00
Sr1—O3—H3D	107 (5)	C2—C5—H51	112.00
H4E—O4—H4F	111 (6)	C4B—C5—H54	110.00
Sr1—O4—H4E	117 (5)	H53—C5—H54	108.00
Sr1—O4—H4F	111 (4)	C2—C5—H54	110.00
Sr1ⁱⁱⁱ—O4—H4F	107 (4)	C4A—C5—H51	112.00
Sr1ⁱⁱⁱ—O4—H4E	112 (5)	C4A—C5—H52	112.00
Sr1—O5—H5D	119 (5)	H51—C5—H52	109.00
Sr1—O5—H5C	118 (5)	C4B—C5—H53	110.00
H5C—O5—H5D	109 (7)

O3—Sr1—O1—C1	−76.6 (8)	O5ⁱⁱⁱ—Sr1ⁱⁱⁱ—O3—Sr1	−158.1 (2)
O4—Sr1—O1—C1	101.4 (8)	O6ⁱⁱⁱ—Sr1ⁱⁱⁱ—O3—Sr1	−64.4 (3)
O5—Sr1—O1—C1	128.0 (8)	O1—Sr1—O4—Sr1ⁱⁱⁱ	171.61 (16)
O6—Sr1—O1—C1	−112.8 (8)	O3—Sr1—O4—Sr1ⁱⁱⁱ	−9.71 (18)
O2ⁱ—Sr1—O1—C1	−167.5 (7)	O5—Sr1—O4—Sr1ⁱⁱⁱ	145.3 (2)
O3ⁱⁱ—Sr1—O1—C1	56.1 (8)	O6—Sr1—O4—Sr1ⁱⁱⁱ	45.1 (3)
O4ⁱⁱ—Sr1—O1—C1	−33.0 (8)	O2ⁱ—Sr1—O4—Sr1ⁱⁱⁱ	52.53 (16)
O2ⁱⁱⁱ—Sr1—O1—C1	12.5 (8)	O3ⁱⁱ—Sr1—O4—Sr1ⁱⁱⁱ	−146.0 (2)
O1^iv—Sr1^iv—O2—C1	5.3 (8)	O4ⁱⁱ—Sr1—O4—Sr1ⁱⁱⁱ	−76.7 (3)
O3^iv—Sr1^iv—O2—C1	−125.2 (8)	O2ⁱⁱⁱ—Sr1—O4—Sr1ⁱⁱⁱ	−83.58 (18)
O4^iv—Sr1^iv—O2—C1	136.7 (8)	O3—Sr1ⁱⁱⁱ—O4—Sr1	9.45 (18)
O5^iv—Sr1^iv—O2—C1	64.1 (8)	O2ⁱ—Sr1ⁱⁱⁱ—O4—Sr1	−51.45 (16)
O6^iv—Sr1^iv—O2—C1	−48.4 (8)	O1ⁱⁱⁱ—Sr1ⁱⁱⁱ—O4—Sr1	79.93 (18)
O2ⁱⁱ—Sr1^iv—O2—C1	−174.6 (7)	O3ⁱⁱⁱ—Sr1ⁱⁱⁱ—O4—Sr1	−128.6 (2)
O3^iv—Sr1ⁱⁱ—O2—C1	127.5 (6)	O4ⁱⁱⁱ—Sr1ⁱⁱⁱ—O4—Sr1	−58.9 (3)
O4^iv—Sr1ⁱⁱ—O2—C1	−135.0 (6)	O5ⁱⁱⁱ—Sr1ⁱⁱⁱ—O4—Sr1	53.5 (3)
O1ⁱⁱ—Sr1ⁱⁱ—O2—C1	175.1 (5)	O6ⁱⁱⁱ—Sr1ⁱⁱⁱ—O4—Sr1	157.2 (2)
O3ⁱⁱ—Sr1ⁱⁱ—O2—C1	−50.0 (5)	Sr1—O1—C1—O2	−19.8 (13)
O4ⁱⁱ—Sr1ⁱⁱ—O2—C1	39.4 (5)	Sr1—O1—C1—C2	158.9 (6)
O5ⁱⁱ—Sr1ⁱⁱ—O2—C1	95.3 (5)	Sr1^iv—O2—C1—O1	−172.8 (5)
O6ⁱⁱ—Sr1ⁱⁱ—O2—C1	−98.7 (5)	Sr1ⁱⁱ—O2—C1—O1	13.2 (10)
O2ⁱⁱⁱ—Sr1ⁱⁱ—O2—C1	−5.0 (6)	Sr1^iv—O2—C1—C2	8.5 (11)
O1—Sr1—O3—Sr1ⁱⁱⁱ	−171.81 (15)	Sr1ⁱⁱ—O2—C1—C2	−165.5 (4)
O4—Sr1—O3—Sr1ⁱⁱⁱ	9.48 (18)	C2—N1—C3—C4A	−10.6 (17)
O5—Sr1—O3—Sr1ⁱⁱⁱ	−36.0 (4)	C3—N1—C2—C5	34.0 (8)
O6—Sr1—O3—Sr1ⁱⁱⁱ	−135.3 (2)	C3—N1—C2—C1	160.9 (6)
O2ⁱ—Sr1—O3—Sr1ⁱⁱⁱ	−52.54 (16)	O1—C1—C2—N1	4.6 (9)
O3ⁱⁱ—Sr1—O3—Sr1ⁱⁱⁱ	80.0 (3)	O2—C1—C2—C5	−58.5 (9)
O4ⁱⁱ—Sr1—O3—Sr1ⁱⁱⁱ	146.5 (2)	O2—C1—C2—N1	−176.6 (6)
O2ⁱⁱⁱ—Sr1—O3—Sr1ⁱⁱⁱ	83.01 (17)	O1—C1—C2—C5	122.7 (7)
O4—Sr1ⁱⁱⁱ—O3—Sr1	−9.45 (18)	N1—C2—C5—C4A	−43.4 (12)
O2ⁱ—Sr1ⁱⁱⁱ—O3—Sr1	51.95 (16)	C1—C2—C5—C4A	−166.7 (12)
O1ⁱⁱⁱ—Sr1ⁱⁱⁱ—O3—Sr1	−81.27 (18)	N1—C3—C4A—C5	−17 (2)
O3ⁱⁱⁱ—Sr1ⁱⁱⁱ—O3—Sr1	55.3 (3)	C3—C4A—C5—C2	37 (2)
O4ⁱⁱⁱ—Sr1ⁱⁱⁱ—O3—Sr1	127.5 (2)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Br2ⁱ	0.90 (6)	2.52 (5)	3.374 (7)	159 (6)
N1—H1B···Br3ⁱ	0.90 (7)	2.40 (7)	3.240 (7)	156 (8)
O3—H3C···Br3^v	0.84 (7)	2.63 (7)	3.440 (6)	163 (7)
O3—H3D···Br2^vi	0.84 (7)	2.54 (7)	3.376 (6)	172 (5)
O4—H4E···Br2^vii	0.85 (6)	2.47 (7)	3.281 (6)	162 (7)
O4—H4F···Br3^viii	0.83 (6)	2.52 (6)	3.347 (6)	174 (6)
O5—H5C···Br2ⁱ	0.86 (5)	2.54 (5)	3.369 (6)	164 (6)
O5—H5D···Br3^viii	0.84 (6)	2.48 (6)	3.304 (6)	166 (6)
O6—H6C···Br2^vi	0.83 (6)	2.58 (6)	3.393 (6)	167 (5)
O6—H6D···Br3ⁱ	0.85 (7)	2.56 (6)	3.378 (6)	162 (7)

Symmetry codes: (i) x+1, y, z; (v) −x+3/2, −y+1, z+1/2; (vi) −x+2, y+1/2, −z+1/2; (vii) −x+3/2, −y, z+1/2; (viii) −x+2, y−1/2, −z+1/2.

Selected bond lengths (Å) top

Sr1—O1	2.524 (4)	Sr1—O2ⁱ	2.728 (4)
Sr1—O3	2.625 (6)	Sr1—O3ⁱⁱ	2.707 (6)
Sr1—O4	2.630 (6)	Sr1—O4ⁱⁱ	2.651 (5)
Sr1—O5	2.593 (5)	Sr1—O2ⁱⁱⁱ	2.800 (5)
Sr1—O6	2.582 (6)

Symmetry codes: (i) x+1, y, z; (ii) x−1/2, −y+1/2, −z+1; (iii) x+1/2, −y+1/2, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Br2ⁱ	0.90 (6)	2.52 (5)	3.374 (7)	159 (6)
N1—H1B···Br3ⁱ	0.90 (7)	2.40 (7)	3.240 (7)	156 (8)
O3—H3C···Br3^iv	0.84 (7)	2.63 (7)	3.440 (6)	163 (7)
O3—H3D···Br2^v	0.84 (7)	2.54 (7)	3.376 (6)	172 (5)
O4—H4E···Br2^vi	0.85 (6)	2.47 (7)	3.281 (6)	162 (7)
O4—H4F···Br3^vii	0.83 (6)	2.52 (6)	3.347 (6)	174 (6)
O5—H5C···Br2ⁱ	0.86 (5)	2.54 (5)	3.369 (6)	164 (6)
O5—H5D···Br3^vii	0.84 (6)	2.48 (6)	3.304 (6)	166 (6)
O6—H6C···Br2^v	0.83 (6)	2.58 (6)	3.393 (6)	167 (5)
O6—H6D···Br3ⁱ	0.85 (7)	2.56 (6)	3.378 (6)	162 (7)

Symmetry codes: (i) x+1, y, z; (iv) −x+3/2, −y+1, z+1/2; (v) −x+2, y+1/2, −z+1/2; (vi) −x+3/2, −y, z+1/2; (vii) −x+2, y−1/2, −z+1/2.

Experimental details

Crystal data
Chemical formula	[Sr(C₅H₉NO₂)(H₂O)₄]Br₂
M_r	434.63
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	296
a, b, c (Å)	6.7079 (4), 12.9125 (9), 15.4499 (11)
V (Å³)	1338.20 (16)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	10.01
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	Bruker Kappa APEXII CCD diffractometer
Absorption correction	Multi-scan (SABABS; Bruker, 2004)
T_min, T_max	0.26, 0.44
No. of measured, independent and observed [I > 2σ(I)] reflections	14183, 2345, 2081
R_int	0.068
(sin θ/λ)_max (Å⁻¹)	0.594

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.032, 0.063, 1.07
No. of reflections	2345
No. of parameters	186
No. of restraints	26
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.60, −0.86
Absolute structure	Flack x determined using 788 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Absolute structure parameter	0.008 (8)

Computer programs: APEX2 (Bruker, 2004), APEX2 and SAINT (Bruker, 2004), SAINT and XPREP (Bruker, 2004), SIR92 (Altomare et al., 1993), SHELXL2014 (Sheldrick, 2015), PLATON (Spek, 2009) and Mercury (Macrae et al., 2008).

Acknowledgements

TB and SS would like to acknowledge the University Grants Commission (UGC), India for providing financial support [Project No. 41-956/2012(SR)]. ST is very grateful to the management of SASTRA University for infrastructural and financial support (Professor TRR grant).

References

Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl. Cryst. 26, 343–350. CrossRef Web of Science IUCr Journals Google Scholar
Balakrishnan, T., Ramamurthi, K., Jeyakanthan, J. & Thamotharan, S. (2013). Acta Cryst. E69, m60–m61. CSD CrossRef IUCr Journals Google Scholar
Bruker (2004). APEX2, SAINT, XPREP and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Kayushina, R. L. & Vainshtein, B. K. (1965). Kristallografiya, 10, 833–844. Google Scholar
Lyhs, B., Bläser, D., Wölper, C., Haack, R., Jansen, G. & Schulz, S. (2012). Eur. J. Inorg. Chem. pp. 4350–4355. Web of Science CSD CrossRef Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259. Web of Science CrossRef CAS IUCr Journals Google Scholar
Rao, S. T., Westhof, E. & Sundaralingam, M. (1981). Acta Cryst. A37, 421–425. CrossRef CAS IUCr Journals Web of Science Google Scholar
Revathi, P., Balakrishnan, T., Ramamurthi, K. & Thamotharan, S. (2015). Acta Cryst. E71, 875–878. CSD CrossRef IUCr Journals Google Scholar
Sathiskumar, S., Balakrishnan, T., Ramamurthi, K. & Thamotharan, S. (2015a). Spectrochim. Acta Part A, 138, 187–194. Web of Science CSD CrossRef CAS Google Scholar
Sathiskumar, S., Balakrishnan, T., Ramamurthi, K. & Thamotharan, S. (2015b). Acta Cryst. E71, 217–219. CSD CrossRef IUCr Journals Google Scholar
Selvaraj, M., Thamotharan, S., Roy, S. & Vijayan, M. (2007). Acta Cryst. B63, 459–468. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Sharma, A., Thamotharan, S., Roy, S. & Vijayan, M. (2006). Acta Cryst. C62, o148–o152. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 71| Part 10| October 2015| Pages 1199-1202

doi:10.1107/S2056989015017302

Open

access

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text

Search IUCr Journals		doi		Advanced search
Author		volume	page

research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)