Tetra­kis-μ-l-alanine-κ8 O:O′-bis­[tetra­aqua­terbium(III)] hexa­perchlorate

Musa E Mohamed; Deepak Chopra; K N Venugopal; Thavendran Govender; Hendrik G Kruger; Glenn E M Maguire

doi:10.1107/S1600536810002448

. 2010 Jan 23;66(Pt 2):m193–m194. doi: 10.1107/S1600536810002448

Tetrakis-μ-l-alanine-κ⁸ O:O′-bis[tetraaquaterbium(III)] hexaperchlorate

Musa E Mohamed ^a, Deepak Chopra ^b,^*, K N Venugopal ^c, Thavendran Govender ^d, Hendrik G Kruger ^a, Glenn E M Maguire ^a

PMCID: PMC2979733 PMID: 21579659

Abstract

The asymmetric unit of the title compound, [Tb₂(C₃H₇NO₂)₄(H₂O)₈](ClO₄)₆, contains a dinuclear cation and six perchlorate anions, one of which is disordered. In the cation, the four l-alanine molecules are present in their zwitterionic form and bridge two Tb³⁺ ions through their carboxylate O atoms. Each Tb atom is also coordinated by four water molecules in a square-antiprismatic geometry. In the crystal structure, the cations and anions are held together via intermolecular O—H⋯O and N—H⋯O hydrogen bonds.

Related literature

For applications of terbium complexes, see: Ropp (2004 ▶). For complexes of rare-earth ions, see: Ngoan et al. (1988 ▶); Glowiak et al. (1991 ▶, 1996 ▶); Hu et al. (1995 ▶); Tianzhu et al. (1987 ▶).

Experimental

Crystal data

[Tb₂(C₃H₇NO₂)₄(H₂O)₈](ClO₄)₆
M _r = 1415.05
Triclinic,
a = 10.7703 (3) Å
b = 10.7766 (2) Å
c = 11.3521 (3) Å
α = 79.345 (2)°
β = 65.390 (3)°
γ = 67.658 (2)°
V = 1107.44 (5) Å³
Z = 1
Mo Kα radiation
μ = 3.65 mm⁻¹
T = 100 K
0.40 × 0.40 × 0.40 mm

Data collection

Oxford Diffraction Excalibur2 CCD diffractometer
Absorption correction: multi-scan (Blessing, 1995 ▶, 1997 ▶) T _min = 0.637, T _max = 0.780
11115 measured reflections
8505 independent reflections
8128 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.107
S = 1.09
8505 reflections
639 parameters
47 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 1.42 e Å⁻³
Δρ_min = −2.57 e Å⁻³
Absolute structure: Flack (1983 ▶), 770 Friedel pairs
Flack parameter: 0.006 (9)

Data collection: CrysAlis CCD (Oxford Diffraction, 2003 ▶); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2003 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810002448/cv2689sup1.cif

e-66-0m193-sup1.cif^{(34.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810002448/cv2689Isup2.hkl

e-66-0m193-Isup2.hkl^{(416KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H23⋯O12S	0.91	2.20	2.928 (15)	136
N3—H31⋯O17S	0.91	2.32	3.032 (15)	136
O14—H14B⋯O25S	0.85 (10)	2.01 (9)	2.754 (15)	145 (6)
O5—H5A⋯O3Sⁱ	0.86 (4)	2.00 (4)	2.809 (10)	156 (3)
O4—H4B⋯O9Sⁱ	0.85 (5)	2.37 (6)	3.05 (2)	137 (3)
N2—H22⋯O4Sⁱⁱ	0.91	2.23	3.022 (12)	145
N2—H21⋯O15Sⁱⁱ	0.91	2.11	2.768 (19)	129
N1—H13⋯O16Sⁱⁱ	0.91	2.02	2.906 (13)	163
N2—H22⋯O2Sⁱⁱ	0.91	2.22	3.016 (12)	147
N4—H42⋯O7SBⁱⁱⁱ	0.91	2.10	2.98 (5)	163
N3—H33⋯O22Sⁱⁱⁱ	0.91	1.94	2.822 (19)	164
N4—H41⋯O24Sⁱⁱⁱ	0.91	2.18	3.033 (12)	156
N4—H42⋯O5Sⁱⁱⁱ	0.91	2.31	3.049 (13)	139
N1—H11⋯O6S^iv	0.91	2.20	3.002 (15)	147
O3—H3B⋯O6S^iv	0.85 (5)	2.33 (7)	3.149 (15)	161 (4)
N1—H12⋯O4S^v	0.91	2.09	2.981 (11)	165
N2—H21⋯O23S^vi	0.91	2.30	2.924 (10)	125
O3—H3A⋯O23S^vi	0.85 (6)	2.04 (5)	2.882 (10)	171 (4)
O4—H4A⋯O20S^vi	0.86 (6)	2.01 (4)	2.826 (10)	158 (5)
N4—H43⋯O19S^vii	0.91	2.16	3.017 (11)	156
O16—H16B⋯O20S^vii	0.84 (10)	2.16 (5)	2.794 (11)	133 (4)
N3—H32⋯O5S^viii	0.91	2.06	2.926 (12)	159
O13—H13A⋯O8^ix	0.86 (3)	2.01 (3)	2.863 (10)	174 (5)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) ; (ix) .

Acknowledgments

We thank Dr Kirsty Stewart, UKZN, for the data collection.

supplementary crystallographic information

Comment

Structural determinations of complexes of rare-earth metals with amino acids are of interest to understand the coordination chemistry of these important class of compounds and to utilize in different optical devices (Ropp, 2004).

In this regard, different complexes, with DL-alanine as the amino acid, containing chloride ions as the counter-ion with the rare-earth metal ion being holmium (Ngoan et al., 1988) and dysprosium (Glowiak et al., 1991) have been synthesized and characterized structurally. The commonly observed inorganic counterions are either perchlorate or chloride anions. It has been observed that depending on the counterion present, the crystal structure contains motifs forming either dimers, chains or network structure in the crystal lattice (Hu et al., 1995, and references therein). Keeping in mind the structural diversity associated with these complexes, we report here the structure of a terbium complex with L-alanine, (I), as extension of the already determined crystal structures.

The title compound (I) crystallizes in the triclinic non-centrosymmetric space group P1. Analogous complexes of neodymium (existing as dimorphs; Glowiak et al., 1996), yttrium (Tianzhu et al., 1987),and erbium (Hu et al., 1995) have also been characterized structurally. The present complex is isostructural with the triclinic form of the neodynium complex which also crystallizes in the triclinic space group P1. The dimeric structure of the complex is depicted in Fig.1. The terbium atom exists in a distorted square-antiprism geometry, having a coordination number of eight. The complex contains two eight-membered rings in the dinuclear cluster, the dihedral angles between these being 88.1 (1)°.

The crystal structure is composed of discrete dinuclear clusters of terbium metal atoms bridged by the carboxyl group of the L-alanine ligand. The ligand exists in the zwitterionic form. The Tb–O(carboxyl) distances lie in the range of 2.274 (6)-2.376 (6)Å while those of Tb–O(water) between 2.358 (8)Å and 2.539 (6)Å. The Tb—Tb distance is 4.367 (3)Å. The dinuclear cations are separated by perchlorate ions, which form hydrogen bonds between coordinated water molecules and the amino groups (Table 1).

Experimental

An aqueous solution of terbium perchlorate was prepared by digesting (0.15 gm) terbium oxide in concentrated perchloric acid (2 ml), a suitable concentration of terbium perchlorate (0.33 g, 2 mmol) was achieved by diluting the concentrated solution with 4 ml distilled water. L-alanine (0.10 g, 1 mmol) was added as solid to the above aqueous solution of terbium perchlorate. The mixture was stirred at about 80C on a heating plate while an aqueous solution of NaOH (0.5M) was added dropwise to cause an incipient but permanent precipitate, pH=4. The mixture was then filtered, and the filtrate was then reduced to about 4 ml. The hot solution was tightly covered and allowed to evaporate gradually at room temperature. The crystalline precipitate appeared in about 7 days. The solid was collected by filtration, washed with cold diethyl ether/THF 1:1 v/v, and dried under vacuum in a desiccator charged with silica gel. The melting point is 241C. The presence of terbium metal was detected by xylenol orange indicator.