catena-Poly[[[aqua(glycine-κO)lithium]-μ-glycine-κ2 O:O′] bromide]

In the title coordination polymer, {[Li(C2H5NO2)2(H2O)]Br}n, the Li+ cation is coordinated by three carboxylate O atoms of zwitterionic glycine molecules and by a water molecule, forming a distorted tetrahedral geometry. One of the two glycine molecules bridges neighbouring complexes, forming an infinite chain parallel to the c axis. Polymeric chains are further linked by extensive hydrogen bonds involving the Br− anions and glycine and water molecules, producing a three-dimensional network.

In the title coordination polymer, {[Li(C 2 H 5 NO 2 ) 2 (H 2 O)]Br} n , the Li + cation is coordinated by three carboxylate O atoms of zwitterionic glycine molecules and by a water molecule, forming a distorted tetrahedral geometry. One of the two glycine molecules bridges neighbouring complexes, forming an infinite chain parallel to the c axis. Polymeric chains are further linked by extensive hydrogen bonds involving the Br À anions and glycine and water molecules, producing a threedimensional network.

Comment
The asymmetric unit of the title complex contains two glycine molecules, one Li cation, one Branion and a water molecule (Fig. 1). The bond lengths and angles around the carboxylic groups of both glycine molecules indicate that they are deprotonated and each carboxylic group then carries a negative charge. The amino groups of the glycine molecules are protonated. The positive charge of the ammonium groups are compensated for by the negative charge of the carboxylate groups. The central Li atom is coordinated by a water molecule and three carboxylate oxygen atoms of the three glycine molecules, and has a distorted tetrahedral coordination geometry. One of the two glycine molecules acts as a bridging ligand connecting neighbouring complexes to an infinite chain parallel to the c axis (Fig. 2).
The ammonium group of one glycine molecule is involved in an intermolecular hydrogen bond (N1-H1A···O4) with an adjacent glycine molecule (Table 1). Another amino group of the second glycine molecule also participates in an intermolecular hydrogen bond (N2-H2B···O1) with a neighbouring carboxylate group of a glycine molecule. These two hydrogen bonds combined to produce C 2 2 (10) (Bernstein et al., 1995) chains that run parallel to the c axis. Adjacent C 2 2 (10) chains are connected by another N1···O1 hydrogen bond via hydrogen H2C. Two types of N2···O1 hydrogen bonds generate two ring motifs, R 2 4 (8) and R 4 4 (20), with C 2 2 (10) chains (Fig. 3). These two ring motifs are arranged alternately along the c axis.
Each polymer chain is interconnected with neighbouring polymeric chains via a hydrogen bond (N2-H2C···O1, Table   1) involving the ammonium group of glycine and a symmetry-related carboxylate group. This hydrogen bond produce two ring motifs R 2 2 (18) and R 2 2 (26). These two rings motifs are arranged alternately along the bc plane (Fig. 4). Four glycine molecules and two Li cations are involved in the former ring, while six glycines and four Li ions are involved in the latter motif. The Branion acts as an acceptor for two different ammonium groups (atoms N1 and N2) of the glycine molecules. The water molecule acts as a donor for two different intermolecular hydrogen bonds with a carboxylate oxygen (O2) and the Branion. The N1-H1C···Br1, O1W-H1···O2 and O1W-H2···Br1 hydrogen bonds held together to form a R 4 6 (18) ring motif (Fig. 5).

Experimental
A 1:1 stoichiometeric mixture of glycine and lithium bromide was dissolved in double distilled water. Colourless blockshaped single crystals were obtained after 2 weeks by slow evaporation.

Refinement
The positions of H atoms bound to nitrogen and water oxygen were determined from difference electron density maps and refined freely along with their isotropic displacement parameter. The O-H distances of water molecule are restrained to 0.84 (2) Å using DFIX option. The H atoms bound to carbon were placed in geometrically idealized positions (C-H = 0.99 Å) and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C).

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.  (7) 0.0217 (9) 0.0058 (7)  O3 0.0410 (10) 0.0198 (7) 0.0349 (10) 0.0062 (7) 0.0300 (9) 0.0011 (7) (17)