Crystal structure of catena-poly[[[tri­aqua­strontium]-di-μ2-glycinato] dibromide]

Revathi, P.; Balakrishnan, T.; Ramamurthi, K.; Thamotharan, S.

doi:10.1107/S2056989015012219

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Volume 71| Part 7| July 2015| Pages 875-878

doi:10.1107/S2056989015012219

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Crystal structure of catena-poly[[[triaquastrontium]-di-μ₂-glycinato] dibromide]

Palanisamy Revathi,^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 M. Weil, Vienna University of Technology, Austria (Received 18 June 2015; accepted 25 June 2015; online 30 June 2015)

In the title coordination polymer, {[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂}_n, the Sr²⁺ ion and one of the water molecules are located on twofold rotation axes. The alkaline earth ion is nine-coordinated by three water O atoms and six O atoms of the carboxylate groups of four glycine ligands, two in a chelating mode and two in a monodentate mode. The glycine molecule exists in a zwitterionic form and bridges the cations into chains parallel to [001]. The Br⁻ counter-anions are located between the chains. Intermolecular hydrogen bonds are formed between the amino and carboxylate groups of neighbouring glycine ligands, generating a head-to-tail sequence. Adjacent head-to-tail sequences are further interconnected by intermolecular N—H⋯Br hydrogen-bonding interactions into sheets parallel to (100). O—H⋯Br and O—H⋯O hydrogen bonds involving the coordinating water molecules are also present, consolidating the three-dimensional hydrogen-bonding network.

Keywords: crystal structure; glycine; strontium; N/O—H⋯Br/O hydrogen bonds.

CCDC reference: 1408767

1. Chemical context

Research in the field of coordination polymers has undergone rapid development in recent years due to their interesting structures and their wide range of applications as functional materials (Lyhs et al., 2012 ). One of the simplest amino acids is glycine and some glycine–metal complexes have been reported previously (Fleck et al., 2006 and references therein). The crystal structures of strontium combined with anions of amino acids are rare. As part of our ongoing investigations of the crystal and molecular structures of a series of metal complexes derived from amino acids (Sathiskumar et al., 2015a ,b ; Balakrishnan et al., 2013 ), we report here the crystal structure of a polymeric strontium–glycine complex, {[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂}_n, (I).

2. Structural commentary

The asymmetric unit of (I) contains one Sr²⁺ ion, one glycine ligand, one and a half water molecules and one bromide anion (Fig. 1). The Sr²⁺ cation and one of the water molecules (O4) are located on special positions with site symmetry 2. The bond lengths involving the carboxylate atoms and the protonation of the amino group reveal a zwitterionic form for the glycine ligand in (I). The Sr²⁺ ion is nine-coordinated by three oxygen atoms [Sr—O = 2.526 (4)–2.661 (2) Å] of water molecules and six carboxylate oxygen atoms of four glycine ligands [Sr—O = 2.605 (2)–2.703 (2) Å]. The glycine ligands coordinate each cation in a bis-bidentate and bis-monodentate way and simultaneously bridge two alkaline earth cations. As shown in Fig. 2, this coordination mode leads to the formation of polymeric chains running parallel to [001]. Adjacent Sr²⁺ ions are separated by 4.3497 (3) Å within a chain and the shortest Sr⋯Sr distance between neighbouring chains is 9.4960 (3) Å.

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

. Displacement ellipsoids are drawn at the 40% probability level. [Symmetry codes: (a) −x, y, $[{1\over 2}]$ − z; (b) −x, 1 − y, 1 − z; (c) x, 1 − y, − $[{1\over 2}]$ + z].

Figure 2
The crystal packing of (I)

projected along [010]. H atoms have been omitted for clarity.

3. Supramolecular features

The crystal structure of (I) contains an intricate network of intermolecular N—H⋯O, N—H⋯Br, O—H⋯O and O—H⋯Br hydrogen bonds (Table 1). The protonated N atom of the glycine molecule is capable of forming three hydrogen-bonding interactions. One of them is the characteristic head-to-tail sequence in which amino acids are self-assembled through their amino and carboxylate groups (Sharma et al., 2006 ; Selvaraj et al., 2007 ; Balakrishnan et al., 2013). In (I), the zwitterionic glycine molecules are arranged in linear arrays that run parallel to the [110] direction (Fig. 3), and adjacent glycine molecules are interconnected by an intermolecular N1—H1A⋯O1 hydrogen bond. This interaction can be described as a head-to-tail sequence having a C(5) graph-set motif (Bernstein et al., 1995 ). In each array, the Br⁻ counter anions bridge neighbouring glycines. Taken together, these three interactions form a hydrogen-bonded sheet extending parallel to (100). One of the water molecules (O3) acts as a donor for two different Br⁻ anions. These intermolecular O—H⋯Br interactions result in a cyclic dibromide motif as observed in the crystal structure of N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium dibromide dihydrate (Srinivasan et al., 2006 ). Within this motif, the distance between Br anions is 5.3398 (3) Å, and the distance between water oxygen atoms (O3⋯O3′) is 3.932 (4) Å. Adjacent cylic dibromide motifs, which are parallel to [001], are interconnected by another water molecule (O4) (Table 1 and Fig. 4).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O1ⁱ	0.88 (5)	2.00 (5)	2.879 (4)	175 (4)
N1—H1B⋯Br1ⁱⁱ	0.88 (4)	2.58 (4)	3.450 (3)	179 (4)
N1—H1C⋯Br1ⁱⁱⁱ	0.89 (4)	2.51 (4)	3.321 (3)	152 (3)
O4—H4⋯O3^iv	0.83 (2)	2.01 (2)	2.828 (3)	166 (5)
O3—H3A⋯Br1ⁱⁱ	0.84 (5)	2.50 (5)	3.335 (3)	170 (4)
O3—H3B⋯Br1^v	0.84 (2)	2.55 (3)	3.296 (3)	148 (4)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (ii) $[x, -y+2, z-{\script{1\over 2}}]$ ; (iii) $[-x+{\script{1\over 2}}, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ ; (iv) $[x, -y+1, z-{\script{1\over 2}}]$ ; (v) $[-x, y, -z+{\script{3\over 2}}]$ .

Figure 3
Zwitterionic glycine molecules are interconnected by intermolecular N—H⋯O and N—H⋯Br hydrogen bonds into (100) sheets.

Figure 4
Cyclic dibromide motifs are interconnected by intermolecular O—H⋯O interactions.

4. Synthesis and crystallization

Crystals of (I) were grown from an aqueous solution by slow solvent evaporation at room temperature. Analytical grade reagents glycine (Merck) and strontium bromide hexahydrate (Sigma–Aldrich) were taken in a 2:1 molar ratio, dissolved in double-distilled water and stirred well for 4 h using a temperature-controlled magnetic stirrer to yield a homogeneous mixture. The solution was finally filtered using Whatman filter paper. The beaker containing the solution was closed with a polythene sheet with two (or) three perforations and kept in a dust-free atmosphere for slow evaporation. Single crystals were harvested after a growth period of 20 days.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The positions of the amino and water H atoms were located from difference Fourier maps. The O3—H3B and O4—H4 distances of the water molecules were restrained to 0.85 (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 atoms.

Table 2
Experimental details

Crystal data
Chemical formula	[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂
M_r	451.63
Crystal system, space group	Orthorhombic, Pbcn
Temperature (K)	296
a, b, c (Å)	16.4198 (9), 9.5438 (5), 8.2402 (4)
V (Å³)	1291.30 (12)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	10.38
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	Bruker Kappa APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 1999)
T_min, T_max	0.251, 0.410
No. of measured, independent and observed [I > 2σ(I)] reflections	22178, 1564, 1244
R_int	0.070
(sin θ/λ)_max (Å⁻¹)	0.661

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.057, 1.14
No. of reflections	1564
No. of parameters	99
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.86, −0.68
Computer programs: APEX2 and SAINT (Bruker, 2004 ), SIR92 (Altomare et al., 1995 ), SHELXL2014 (Sheldrick, 2015 ), PLATON (Spek, 2009 ) and Mercury (Macrae et al., 2008 ).

Supporting information

CCDC reference: 1408767

Crystal structure: contains datablock I. DOI: 10.1107/S2056989015012219/wm5177sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015012219/wm5177Isup2.hkl

checkCIF report

Chemical context top

Research in the field of coordination polymers has undergone rapid development in recent years due to their interesting structures and their wide range of applications as functional materials (Lyhs et al., 2012). One of the simplest amino acids is glycine and some glycine–metal complexes have been reported previously (Fleck et al., 2006 and references therein). The crystal structures of strontium combined with anions of amino acids are rare. As part of our ongoing investigations of the crystal and molecular structures of a series of metal complexes derived from amino acids (Sathiskumar et al., 2015a,b; Balakrishnan et al., 2013), we report here the crystal structure of a polymeric strontium–glycine complex, {[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂}_n, (I).

Structural commentary top

The asymmetric unit of (I) contains one Sr²⁺ ion, one glycine ligand, one and a half water molecules and one bromide anion (Fig. 1). The Sr²⁺ cation and one of the water molecules (O4) are located on special positions with site symmetry 2. The bond lengths involving the carboxylate atoms and the protonation of the amino group reveal a zwitterionic form for the glycine ligand in (I). The Sr²⁺ ion is nine-coordinated by three oxygen atoms [Sr—O = 2.526 (4)–2.661 (2) Å] of water molecules and six carboxylate oxygen atoms of four glycine ligands [Sr—O = 2.605 (2)–2.703 (2) Å]. The glycine ligands coordinate each cation in a bis-bidentate and bis-monodentate way and simultaneously bridge two alkaline earth cations. As shown in Fig. 2, this coordination mode leads to the formation of polymeric chains running parallel to [001]. Adjacent Sr²⁺ ions are separated by 4.3497 (3) Å within a chain and the shortest Sr···Sr distance between neighbouring chains is 9.4960 (3) Å.

Supramolecular features top

\ The crystal structure of (I) contains an intricate network of intermolecular N—H···O, N—H···Br, O—H···O and O—H···Br hydrogen bonds (Table 1). The protonated N atom of the glycine molecule is capable of forming three hydrogen-bonding interactions. One of them is the characteristic head-to-tail sequence in which amino acids are self-assembled through their amino and carboxylate groups (Sharma et al., 2006; Selvaraj et al., 2007; Balakrishnan et al., 2013). In (I), the zwitterionic glycine molecules are arranged in linear arrays that run parallel to the [110] direction (Fig. 3), and adjacent glycine molecules are interconnected by an intermolecular N1—H1A···O1 hydrogen bond. This interaction can be described as a head-to-tail sequence having a C(5) graph-set motif (Bernstein et al., 1995). In each array, the Br^- counter anions bridge neighbouring glycines. Taken together, these three interactions form a hydrogen-bonded sheet extending parallel to (100). One of the water molecules (O3) acts as a donor for two different Br^- anions. These intermolecular O—H···Br interactions result in a cyclic dibromide motif as observed in the crystal structure of N,N'-dibenzyl-N,N,N',N'-\ tetramethylethylenediammonium dibromide dihydrate (Srinivasan et al., 2006). Within this motif, the distance between Br anions is 5.3398 (3) Å, and the distance between water oxygen atoms (O3···O3') is 3.932 (4) Å. Adjacent cylic dibromide motifs, which are parallel to [001], are interconnected by another water molecule (O4) (Table 1 and Fig. 4).

Synthesis and crystallization top

Crystals of (I) were grown from an aqueous solution by slow solvent evaporation at room temperature. Analytical grade reagents glycine (Merck) and strontium bromide hexahydrate (Sigma–Aldrich) were taken in a 2:1 molar ratio, dissolved in double-distilled water and stirred well for 4 h using a temperature-controlled magnetic stirrer to yield a homogeneous mixture. The solution was finally filtered using Whatman filter paper. The beaker containing the solution was closed with a polythene sheet with two (or) three perforations and kept in a dust -ree atmosphere for slow evaporation. Single crystals were harvested after a growth period of 20 days.

Refinement top

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1995); 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 environment of Sr²⁺ in the crystal structure of (I). Displacement ellipsoids are drawn at the 40% probability level. [Symmetry codes: (a) -x, y, 1/2 - z; (b) -x, 1 - y, 1 - z; (c) x, 1 - y, -1/2 + z].
	Fig. 2. The crystal packing of (I) projected along [010]. H atoms have been omitted for clarity.
	Fig. 3. Zwitterionic glycine molecules are interconnected by intermolecular N—H···O and N—H···Br hydrogen bonds into (100) sheets.
	Fig. 4. Cyclic dibromide motifs are interconnected by intermolecular O—H···O interactions.

catena-Poly[[[triaquastrontium]-di-µ₂-glycinato] dibromide] top

Crystal data top

[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂	D_x = 2.323 Mg m⁻³
M_r = 451.63	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcn	Cell parameters from 6100 reflections
a = 16.4198 (9) Å	θ = 2.5–27.8°
b = 9.5438 (5) Å	µ = 10.38 mm⁻¹
c = 8.2402 (4) Å	T = 296 K
V = 1291.30 (12) Å³	Block, colourless
Z = 4	0.15 × 0.10 × 0.10 mm
F(000) = 872

Data collection top

Bruker Kappa APEXII CCD diffractometer	1244 reflections with I > 2σ(I)
Radiation source: Sealed tube	R_int = 0.070
ω and ϕ scan	θ_max = 28.0°, θ_min = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −21→21
T_min = 0.251, T_max = 0.410	k = −12→12
22178 measured reflections	l = −9→10
1564 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)] = 0.023	w = 1/[σ²(F_o²) + (0.0169P)² + 1.7773P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.057	(Δ/σ)_max = 0.001
S = 1.14	Δρ_max = 0.86 e Å⁻³
1564 reflections	Δρ_min = −0.67 e Å⁻³
99 parameters	Extinction correction: SHELXL2014 (Sheldrick 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
2 restraints	Extinction coefficient: 0.0086 (3)

Crystal data top

[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂	V = 1291.30 (12) Å³
M_r = 451.63	Z = 4
Orthorhombic, Pbcn	Mo Kα radiation
a = 16.4198 (9) Å	µ = 10.38 mm⁻¹
b = 9.5438 (5) Å	T = 296 K
c = 8.2402 (4) Å	0.15 × 0.10 × 0.10 mm

Data collection top

Bruker Kappa APEXII CCD diffractometer	1564 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 1999)	1244 reflections with I > 2σ(I)
T_min = 0.251, T_max = 0.410	R_int = 0.070
22178 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.023	2 restraints
wR(F²) = 0.057	H atoms treated by a mixture of independent and constrained refinement
S = 1.14	Δρ_max = 0.86 e Å⁻³
1564 reflections	Δρ_min = −0.67 e Å⁻³
99 parameters

Special details top

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.

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

	x	y	z	U_iso*/U_eq
C1	0.14184 (17)	0.5997 (3)	0.4781 (4)	0.0178 (6)
C2	0.1901 (2)	0.6557 (3)	0.6205 (4)	0.0232 (7)
H2A	0.1529	0.6963	0.6989	0.028*
H2B	0.2183	0.5788	0.6729	0.028*
N1	0.2500 (2)	0.7627 (3)	0.5708 (4)	0.0263 (6)
O1	0.15044 (13)	0.6537 (2)	0.3416 (2)	0.0224 (5)
O2	0.09257 (13)	0.5034 (2)	0.5090 (3)	0.0251 (5)
O3	−0.00732 (17)	0.8029 (3)	0.4322 (3)	0.0308 (6)
O4	0.0000	0.3083 (4)	0.2500	0.0331 (8)
Br1	0.14700 (2)	0.97766 (4)	0.86395 (4)	0.02908 (12)
Sr2	0.0000	0.57306 (4)	0.2500	0.01637 (12)
H1A	0.279 (3)	0.793 (5)	0.654 (6)	0.062 (15)*
H1B	0.224 (2)	0.830 (4)	0.520 (5)	0.046 (13)*
H1C	0.287 (3)	0.726 (4)	0.505 (5)	0.044 (12)*
H4	−0.007 (3)	0.264 (4)	0.164 (4)	0.064 (15)*
H3A	0.033 (3)	0.853 (5)	0.404 (5)	0.059 (15)*
H3B	−0.0497 (19)	0.852 (4)	0.444 (6)	0.067 (16)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0131 (14)	0.0216 (15)	0.0186 (14)	0.0022 (11)	0.0002 (12)	−0.0025 (12)
C2	0.0231 (17)	0.0283 (18)	0.0183 (16)	−0.0036 (13)	−0.0017 (13)	−0.0028 (13)
N1	0.0224 (15)	0.0283 (17)	0.0283 (15)	−0.0035 (13)	−0.0052 (14)	−0.0055 (14)
O1	0.0204 (11)	0.0284 (12)	0.0184 (11)	−0.0046 (9)	−0.0007 (9)	0.0022 (9)
O2	0.0259 (12)	0.0277 (12)	0.0216 (11)	−0.0084 (9)	−0.0011 (9)	0.0018 (9)
O3	0.0295 (14)	0.0273 (14)	0.0356 (14)	−0.0015 (12)	0.0082 (12)	−0.0045 (11)
O4	0.044 (2)	0.031 (2)	0.0248 (19)	0.000	0.0019 (18)	0.000
Br1	0.02717 (19)	0.0276 (2)	0.0325 (2)	0.00143 (14)	0.00329 (15)	0.00078 (14)
Sr2	0.01582 (19)	0.0194 (2)	0.01391 (19)	0.000	−0.00064 (16)	0.000

Geometric parameters (Å, º) top

C1—O1	1.246 (4)	O2—Sr2	2.703 (2)
C1—O2	1.251 (3)	O3—Sr2	2.661 (2)
C1—C2	1.513 (4)	O3—H3A	0.84 (5)
C1—Sr2	3.004 (3)	O3—H3B	0.842 (19)
C2—N1	1.477 (4)	O4—Sr2	2.526 (4)
C2—H2A	0.9700	O4—H4	0.833 (19)
C2—H2B	0.9700	Sr2—O2ⁱⁱ	2.605 (2)
N1—H1A	0.88 (5)	Sr2—O2ⁱ	2.605 (2)
N1—H1B	0.88 (4)	Sr2—O3ⁱⁱⁱ	2.661 (2)
N1—H1C	0.89 (4)	Sr2—O1ⁱⁱⁱ	2.695 (2)
O1—Sr2	2.695 (2)	Sr2—O2ⁱⁱⁱ	2.703 (2)
O2—Sr2ⁱ	2.605 (2)	Sr2—C1ⁱⁱⁱ	3.004 (3)

O1—C1—O2	124.1 (3)	O1ⁱⁱⁱ—Sr2—O1	146.83 (10)
O1—C1—C2	119.7 (3)	O4—Sr2—O2ⁱⁱⁱ	75.77 (4)
O2—C1—C2	116.1 (3)	O2ⁱⁱ—Sr2—O2ⁱⁱⁱ	69.96 (8)
O1—C1—Sr2	63.74 (15)	O2ⁱ—Sr2—O2ⁱⁱⁱ	101.82 (7)
O2—C1—Sr2	64.13 (16)	O3ⁱⁱⁱ—Sr2—O2ⁱⁱⁱ	77.44 (7)
C2—C1—Sr2	157.1 (2)	O3—Sr2—O2ⁱⁱⁱ	128.53 (7)
N1—C2—C1	112.2 (3)	O1ⁱⁱⁱ—Sr2—O2ⁱⁱⁱ	48.23 (6)
N1—C2—H2A	109.2	O1—Sr2—O2ⁱⁱⁱ	143.76 (6)
C1—C2—H2A	109.2	O4—Sr2—O2	75.77 (4)
N1—C2—H2B	109.2	O2ⁱⁱ—Sr2—O2	101.82 (7)
C1—C2—H2B	109.2	O2ⁱ—Sr2—O2	69.96 (8)
H2A—C2—H2B	107.9	O3ⁱⁱⁱ—Sr2—O2	128.53 (7)
C2—N1—H1A	111 (3)	O3—Sr2—O2	77.44 (7)
C2—N1—H1B	108 (3)	O1ⁱⁱⁱ—Sr2—O2	143.76 (6)
H1A—N1—H1B	113 (4)	O1—Sr2—O2	48.23 (6)
C2—N1—H1C	111 (3)	O2ⁱⁱⁱ—Sr2—O2	151.53 (9)
H1A—N1—H1C	104 (4)	O4—Sr2—C1ⁱⁱⁱ	94.86 (6)
H1B—N1—H1C	109 (4)	O2ⁱⁱ—Sr2—C1ⁱⁱⁱ	89.95 (7)
C1—O1—Sr2	91.77 (17)	O2ⁱ—Sr2—C1ⁱⁱⁱ	92.77 (7)
C1—O2—Sr2ⁱ	137.62 (19)	O3ⁱⁱⁱ—Sr2—C1ⁱⁱⁱ	67.17 (8)
C1—O2—Sr2	91.27 (18)	O3—Sr2—C1ⁱⁱⁱ	104.38 (8)
Sr2ⁱ—O2—Sr2	110.04 (8)	O1ⁱⁱⁱ—Sr2—C1ⁱⁱⁱ	24.49 (7)
Sr2—O3—H3A	106 (3)	O1—Sr2—C1ⁱⁱⁱ	149.51 (7)
Sr2—O3—H3B	124 (3)	O2ⁱⁱⁱ—Sr2—C1ⁱⁱⁱ	24.60 (7)
H3A—O3—H3B	111 (4)	O2—Sr2—C1ⁱⁱⁱ	161.97 (7)
Sr2—O4—H4	120 (3)	O4—Sr2—C1	94.86 (6)
O4—Sr2—O2ⁱⁱ	73.73 (5)	O2ⁱⁱ—Sr2—C1	92.77 (7)
O4—Sr2—O2ⁱ	73.73 (5)	O2ⁱ—Sr2—C1	89.95 (7)
O2ⁱⁱ—Sr2—O2ⁱ	147.46 (10)	O3ⁱⁱⁱ—Sr2—C1	104.38 (8)
O4—Sr2—O3ⁱⁱⁱ	145.52 (6)	O3—Sr2—C1	67.17 (8)
O2ⁱⁱ—Sr2—O3ⁱⁱⁱ	76.97 (7)	O1ⁱⁱⁱ—Sr2—C1	149.51 (7)
O2ⁱ—Sr2—O3ⁱⁱⁱ	133.43 (8)	O1—Sr2—C1	24.49 (7)
O4—Sr2—O3	145.52 (6)	O2ⁱⁱⁱ—Sr2—C1	161.97 (7)
O2ⁱⁱ—Sr2—O3	133.43 (8)	O2—Sr2—C1	24.60 (7)
O2ⁱ—Sr2—O3	76.96 (7)	C1ⁱⁱⁱ—Sr2—C1	170.29 (11)
O3ⁱⁱⁱ—Sr2—O3	68.96 (11)	O4—Sr2—Sr2^iv	71.300 (10)
O4—Sr2—O1ⁱⁱⁱ	106.59 (5)	O2ⁱⁱ—Sr2—Sr2^iv	35.72 (5)
O2ⁱⁱ—Sr2—O1ⁱⁱⁱ	113.67 (6)	O2ⁱ—Sr2—Sr2^iv	129.21 (5)
O2ⁱ—Sr2—O1ⁱⁱⁱ	76.03 (7)	O3ⁱⁱⁱ—Sr2—Sr2^iv	74.32 (6)
O3ⁱⁱⁱ—Sr2—O1ⁱⁱⁱ	69.40 (8)	O3—Sr2—Sr2^iv	143.02 (6)
O3—Sr2—O1ⁱⁱⁱ	83.18 (8)	O1ⁱⁱⁱ—Sr2—Sr2^iv	80.00 (4)
O4—Sr2—O1	106.59 (5)	O1—Sr2—Sr2^iv	110.90 (4)
O2ⁱⁱ—Sr2—O1	76.03 (7)	O2ⁱⁱⁱ—Sr2—Sr2^iv	34.24 (5)
O2ⁱ—Sr2—O1	113.67 (6)	O2—Sr2—Sr2^iv	131.99 (5)
O3ⁱⁱⁱ—Sr2—O1	83.18 (8)	C1ⁱⁱⁱ—Sr2—Sr2^iv	55.55 (6)
O3—Sr2—O1	69.40 (8)	C1—Sr2—Sr2^iv	128.31 (6)

O1—C1—C2—N1	−6.2 (4)	O1—C1—O2—Sr2ⁱ	−144.8 (2)
O2—C1—C2—N1	176.5 (3)	C2—C1—O2—Sr2ⁱ	32.3 (4)
Sr2—C1—C2—N1	−98.5 (5)	Sr2—C1—O2—Sr2ⁱ	−122.2 (3)
O2—C1—O1—Sr2	22.7 (3)	O1—C1—O2—Sr2	−22.6 (3)
C2—C1—O1—Sr2	−154.3 (2)	C2—C1—O2—Sr2	154.5 (2)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1^v	0.88 (5)	2.00 (5)	2.879 (4)	175 (4)
N1—H1B···Br1^vi	0.88 (4)	2.58 (4)	3.450 (3)	179 (4)
N1—H1C···Br1^vii	0.89 (4)	2.51 (4)	3.321 (3)	152 (3)
O4—H4···O3ⁱⁱ	0.83 (2)	2.01 (2)	2.828 (3)	166 (5)
O3—H3A···Br1^vi	0.84 (5)	2.50 (5)	3.335 (3)	170 (4)
O3—H3B···Br1^viii	0.84 (2)	2.55 (3)	3.296 (3)	148 (4)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1ⁱ	0.88 (5)	2.00 (5)	2.879 (4)	175 (4)
N1—H1B···Br1ⁱⁱ	0.88 (4)	2.58 (4)	3.450 (3)	179 (4)
N1—H1C···Br1ⁱⁱⁱ	0.89 (4)	2.51 (4)	3.321 (3)	152 (3)
O4—H4···O3^iv	0.833 (19)	2.01 (2)	2.828 (3)	166 (5)
O3—H3A···Br1ⁱⁱ	0.84 (5)	2.50 (5)	3.335 (3)	170 (4)
O3—H3B···Br1^v	0.842 (19)	2.55 (3)	3.296 (3)	148 (4)

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

Experimental details

Crystal data
Chemical formula	[Sr(C₂H₅NO₂)₂(H₂O)₃]Br₂
M_r	451.63
Crystal system, space group	Orthorhombic, Pbcn
Temperature (K)	296
a, b, c (Å)	16.4198 (9), 9.5438 (5), 8.2402 (4)
V (Å³)	1291.30 (12)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	10.38
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	Bruker Kappa APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 1999)
T_min, T_max	0.251, 0.410
No. of measured, independent and observed [I > 2σ(I)] reflections	22178, 1564, 1244
R_int	0.070
(sin θ/λ)_max (Å⁻¹)	0.661

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.057, 1.14
No. of reflections	1564
No. of parameters	99
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.86, −0.67

Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SIR92 (Altomare et al., 1995), SHELXL2014 (Sheldrick, 2015), PLATON (Spek, 2009) and Mercury (Macrae et al., 2008).

Acknowledgements

TB and PR acknowledge the Tamil Nadu State Council for Science and Technology, Tamil Nadu, for providing funding as a Major Research Project Scheme (TNSCST/S&T project/PS/RJ/2013–2014). ST is very grateful to the management of SASTRA University for infrastructural and financial support (Professor TRR grant).

References

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Volume 71| Part 7| July 2015| Pages 875-878

doi:10.1107/S2056989015012219

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