A new compound in kidney stones? Powder X-ray diffraction study of calcium glycinate trihydrate

The present identification of a new compound in kidney stones is relevant in clinical practice. Here, poly[[di-[mu]-aqua-bis(glycinato-[kappa]²N,O)calcium(II)] monohydrate], {[Ca(C₂H₄NO₂)₂(H₂O)₂]·H₂O}_n, has been identified in a possible kidney concretion, although it could be a `false calculus' associated with Munchausen syndrome. The crystal packing is characterized by an infinite zigzag chain of Ca atoms in [Ca(OW)₄O₂N₂] (OW is a water O atom) square anti­prisms, sharing edges formed by water mol­ecules. An uncoordinated water mol­ecule inter­connects the parallel chains in a three-dimensional hydrogen-bonding scheme. Similarities between the trihydrate and the monohydrate are described.

S1. Comment

The chemical formulae of compounds found in pathological calcifications are quite diverse, and stones occur in many tissues and organs (Daudon et al., 1993; Bazin et al., 2012). Although many of them were first characterized as minerals or were synthesized, it sometimes happens that they are encountered for the very first time in living bodies. One such recent new crystal structure is calcium tartrate tetrahydrate form II from rat urinary stones (Le Bail, Bazin et al., 2009). This paper deals with the structure determination of a new calcium glycinate hydrate, namely poly[[di-µ-aqua-bis(glycinato-κ²N,O)calcium(II)] monohydrate], (I) (informally known as calcium glycinate trihydrate), possibly coming from the kidney of a young boy, although this remains to be verified since the sample was not surgically removed but given hand-to-hand from the patient to the physician as passed spontaneously (see Experimental).

When a sample of (I) was received for X-ray diffraction analysis, no complete chemical characterization had yet been made. FT–IR, the usual identification method (which failed) for such kidney stones, indicated the presence of carbonyl groups in the form of carboxylate and the very probable purity (Fig. 1) of the sample, and X-ray fluorescence demonstrated the presence of calcium. In the absence of any suitable single crystal, the structure determination by powder diffractometry was undertaken following the most modern approaches, as detailed in recent blind tests (Le Bail, Cranswick et al., 2009). Indexing using the McMaille software (Le Bail, 2004) led to a triclinic cell with figures of merit (FoM) M₂₀ = 70 (de Wolff, 1968) and F₂₀ = 137 (0.004, 38) (Smith & Snyder, 1979). The intensities were extracted from the powder pattern by the Le Bail (2005) method, confirming the cell by an excellent profile fitting using the FULLPROF software (Rodriguez-Carvajal, 1993) and allowing an attempt at structure solution. Meanwhile, DSC–TGA (differential scanning calorimetry–thermogravimetric analysis), followed by X-ray powder analysis, showed that the residue at 873 K was CaCO₃ calcite. The initial model allowing for further Rietveld refinements was obtained from the ESPOIR direct-space software (Le Bail, 2001) working in `scratch mode', inserting one Ca atom and testing various hypothetical compositions (all atoms moved randomly under a Monte Carlo process to obtain agreement between the extracted structure factors and the calculated ones). A model corresponding to the best agreement obtained by this direct-space approach allowed us to recognize infinite zigzag chains of Ca atoms in an eightfold coordination, with square antiprisms sharing edges. The two identical very simple molecules involved in the structure could only be glycine, according to their characteristic three-dimensional shape and given the context of the sample origin and the structural relationship with synthetic calcium glycinate monohydrate, (II), pre-existing in the literature (Fox et al., 2007). The H-atom positions were inferred from neighbouring sites. The final Rietveld plot is shown in Fig. 2 and an ellipsoid plot of (I) is shown in Fig. 3.

The crystal structure of (I) is built up from [CaOW₄O₂N₂] square antiprisms (OW is a water O atom) sharing two OW–OW edges to form infinite zigzag Ca···Ca···Ca chains along the c axis. These chains are interconnected in a three-dimensional manner by hydrogen bonding through the uncoordinated OW3 water molecule (Fig. 4), which connects to three chains, one via the two coordinated water molecules OW1 and OW2 through OW1—H11···OW3ⁱⁱⁱ and OW2—H21···OW3i^v hydrogen bonds [symmetry codes: x, y + 1, z; (v) x, y + 1, z - 1] and the other two via the uncoordinated O atoms (involved in the C═O bond) of the two independent glycinate ligands through OW3—H31···O2 and OW3—H32···O3^vi hydrogen bonds [symmetry code: (vi) -x + 1, -y + 1, -z + 1]. The remaining hydrogen bonds are within chains. The two NH₂ groups also point towards uncoordinated atoms O2 and O3, while atoms H12 and H22 of the two coordinated water molecules are directed towards atoms O1 and O4.

In the monohydrate, (II), the water molecule enters only one corner of the [CaOWO₅N₂] square antiprisms, which share two O–O edges forming similar zigzag chains. In both structures, there is N,O-chelation, i.e. each glycinate ligand coordinates via both the carboxylate and the amino groups. No O,O-chelation occurs. The trihydrate adds the basic motif of the terminal N,O-chelating form to the list of binding modes of Hgly or gly^- in calcium glycine compounds (Natarajan et al., 2012), while the monohydrate is characterized by the µ₃-bridging O,O,O',N-tetradendate and µ₂-bridging O,O,N-tridentate modes. The chains corresponding to both hydrates are compared in Figs. 5 and 6. A topotactic dehydration from the trihydrate to the monohydrate looks possible, in spite of the need for some reorientation of the glycine molecules. However, the first endothermic peak on the DSC graph at 400 K corresponds to 19% mass loss, which is probably associated with the departure of 2.5 water molecules, so it may exist as a hemihydrate, but this was not checked by thermodiffractometry. The next events on the DSC–TGA curve correspond to the departure of the remaining water (in the 473–573 K range), followed by a strong endothermic peak at 593 K and two small exothermic peaks at 683 and 723 K, CaCO₃ calcite being present in the 773–873 K range.

Related literature

For related literature, see: Bazin et al. (2012); Daudon et al. (1993); Fox et al. (2007); Gault et al. (1988); Le Bail (2001, 2004, 2005); Le Bail, Bazin, Daudon, Brochot, Robbez-Masson & Maisonneuve (2009); Le Bail, Cranswick, Adil, Altomare, Avdeev, Cerny, Cuocci, Giacovazzo, Halasz, Lapidus, Louwen, Moliterni, Palatinus, Rizzi, Schilder, Stephens, Stone & van Mechelen (2009); Natarajan et al. (2012); Rodriguez-Carvajal (1993); Sabot et al. (1999); Smith & Snyder (1979); de Wolff (1968).

S2. Experimental

The sample submitted for analysis consisted of many small pieces passed spontaneously by a young boy. Because of its peculiar composition, as revealed by the structure determination, we conclude that the sample probably did not come from the urinary tract and may correspond to a spurious stone. No pathology is yet known which would lead to such lithiasis (Daudon et al., 1993; Bazin et al., 2012). Indeed, calcium glycinate is a common compound in a variety of manufactured cosmetic products or is proposed as a complementary food. The chemical phase commonly reported is the monohydrate. However, we cannot exclude changes in the hydration related to special storage of the product, or even the possibility that the pure trihydrate is sold as such with the `calcium glycinate' name. Factitious stones are not exceptional findings and the literature contains many clinical cases reporting the history of patients with psychatric disorders who simulated a false nephrolithiasis disease (Gault et al., 1988; Sabot et al., 1999). Urolithiasis is only one aspect of Munchausen syndrome, which may be observed as a variety of clinical symptoms. In the present case, the father of the child experienced a history of recurrent nephrolithiasis, thus probably explaining why the boy may have chosen to simulate urolithiasis rather than another type of disease.

S3. Refinement

The cell parameters are those obtained from powder data indexing. The reduced cell [a = 5.7627 (3), b = 9.6572 (5) and c = 9.6878 (5) Å, and α = 82.533 (2), β = 89.412 (3) and γ = 76.997 (3)°] is obtained by the transformation matrix (001/100/010). Rietveld refinement was carried out with restraints on the glycine [C—C = 1.527 (5) Å, N—C = 1.453 (5) Å, O—C = 1.255 (5) Å, O—O = 2.230 (5) Å, C—H = 1.00 (1) Å and N—H = 0.92 (1) Å] and water [O—H = 0.90 (1) Å and H···H = 1.49 (1) Å] molecules, as taken from the Ca(gly)₂.H₂O crystal structure (Fox et al., 2007).

Computing details

Data collection: HIGHSCORE (PANalytical, 2003); cell refinement: McMaille (Le Bail, 2004); data reduction: HIGHSCORE (PANalytical, 2003); program(s) used to solve structure: ESPOIR (Le Bail, 2001); program(s) used to refine structure: FULLPROF (Rodriguez-Carvajal, 1993); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: PLATON (Spek, 2009).

Figures

	Fig. 1. FT–IR spectrum of (I), which may help urologists to identify such kidney stones, if any are confirmed.
	Fig. 2. Final Rietveld plot for (I). Observed data points are indicated by dots, and the best-fit profile (upper trace) and the difference pattern (lower trace) are solid lines. The vertical bars indicate the positions of the Bragg peaks.
	Fig. 3. The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (a) -x + 1, -y + 1, -z; (b) -x + 1, -y + 2, -z + 1.[
	Fig. 4. A projection of the structure of (I) along the short c axis, showing how the infinite zigzag chains of calcium antiprisms sharing edges are interconnected through hydrogen bonding involving the OW3 water molecules.
	Fig. 5. A view of the chains of [CaOW4O2N2] square antiprisms sharing two OW–OW edges in (I).
	Fig. 6. A view of the [CaOWO5N2] square antiprisms sharing two O–O edges in the monohydrate, (II), for comparison with Fig. 5.

poly[[di-µ-aqua-bis(glycinato-κ²N,O)calcium(II)] monohydrate]

Crystal data

[Ca(C2H4NO2)2(H2O)2]·H2O	V = 520.76 (5) Å^3
Mr = 242.25	Z = 2
Triclinic, P1	F(000) = 256
Hall symbol: -P 1	The cell parameters are those obtained from powder data indexing. The reduced cell a = 5.763, b = 9.657, c = 9.688, alpha = 82.53, beta = 89.41, gamma = 77.00 is obtained by the transformation matrix (0 0 -1, -1 0 0, 0 1 0)
a = 9.6572 (5) Å	Dx = 1.545 Mg m^−3
b = 9.6878 (5) Å	Cu Kα radiation, λ = 1.540560 Å
c = 5.7627 (3) Å	T = 293 K
α = 90.588 (3)°	Particle morphology: fine powder
β = 76.997 (3)°	white
γ = 97.467 (2)°	flat sheet, 8 × 8 mm

Data collection

PANalytical X'Pert PRO diffractometer	Data collection mode: reflection
Radiation source: X-ray tube	Scan method: step
None monochromator	2θmin = 4.943°, 2θmax = 69.943°, 2θstep = 0.017°
Specimen mounting: dusted through a sieve

Refinement

Rp = 2.044	126 parameters
Rwp = 2.710	67 restraints
Rexp = 1.323	Hydrogen site location: inferred from neighbouring sites
RBragg = 2.63	H atoms treated by a mixture of independent and constrained refinement
R(F) = 6.82	(Δ/σ)max = 0.03
χ^2 = 4.202	Background function: interpolated
3825 data points	Preferred orientation correction: none
Profile function: pseudo-Voigt

Special details

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 e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ca1	0.8757 (3)	0.8959 (3)	0.2978 (5)	0.0873 (19)*
OW1	0.8683 (8)	1.0369 (7)	0.6539 (14)	0.126 (3)*
H11	0.8490 (12)	1.1169 (8)	0.624 (2)	0.126 (3)*
H12	0.8356 (12)	0.9849 (11)	0.7746 (14)	0.126 (3)*
OW2	0.9626 (7)	1.1346 (8)	0.0889 (14)	0.126 (3)*
H21	0.8726 (12)	1.1566 (13)	0.097 (4)	0.126 (3)*
H22	0.995 (2)	1.1748 (12)	0.213 (3)	0.126 (3)*
OW3	0.7748 (9)	0.2564 (7)	0.897 (2)	0.139 (5)*
H31	0.815 (7)	0.340 (4)	0.83 (2)	0.139 (5)*
H32	0.687 (4)	0.262 (3)	0.990 (12)	0.139 (5)*
N1	0.8325 (6)	0.6569 (5)	0.1838 (6)	0.095 (2)*
H41	0.7505 (9)	0.6331 (10)	0.1160 (15)	0.095 (2)*
H42	0.9065 (10)	0.6256 (9)	0.0636 (15)	0.095 (2)*
N2	0.6257 (5)	0.8512 (6)	0.5114 (6)	0.095 (2)*
H51	0.6062 (11)	0.7795 (9)	0.6308 (14)	0.095 (2)*
H52	0.5886 (9)	0.9274 (9)	0.5966 (19)	0.095 (2)*
O1	0.9089 (8)	0.7462 (3)	0.5953 (8)	0.094 (2)*
O2	0.8296 (8)	0.5377 (5)	0.7711 (11)	0.094 (2)*
O3	0.5112 (5)	0.8158 (8)	−0.0467 (11)	0.094 (2)*
O4	0.7221 (4)	0.9006 (8)	0.0328 (8)	0.094 (2)*
C1	0.8120 (6)	0.5621 (5)	0.3836 (7)	0.095 (2)*
H61	0.7063 (7)	0.5364 (13)	0.4468 (15)	0.095 (2)*
H62	0.8496 (12)	0.4733 (7)	0.3278 (15)	0.095 (2)*
C2	0.8787 (9)	0.6159 (4)	0.5866 (8)	0.095 (2)*
C3	0.5337 (6)	0.8088 (6)	0.3513 (7)	0.095 (2)*
H71	0.5141 (13)	0.7046 (6)	0.3559 (17)	0.095 (2)*
H72	0.4393 (7)	0.8419 (12)	0.4124 (18)	0.095 (2)*
C4	0.5918 (5)	0.8560 (11)	0.0928 (6)	0.095 (2)*

Geometric parameters (Å, º)

Ca1—O1	2.359 (5)	OW2—H21	0.913 (15)
Ca1—OW1	2.446 (8)	OW3—H31	0.90 (6)
Ca1—OW2	2.569 (8)	OW3—H32	0.90 (5)
Ca1—O4	2.361 (5)	N1—C1	1.442 (6)
Ca1—N1	2.410 (6)	N2—C3	1.441 (7)
Ca1—N2	2.436 (5)	N1—H41	0.961 (10)
Ca1—OW2^i	2.456 (8)	N1—H42	0.955 (10)
Ca1—OW1^ii	2.550 (8)	N2—H51	0.953 (10)
O1—C2	1.261 (5)	N2—H52	0.947 (11)
O2—C2	1.275 (7)	C1—C2	1.515 (8)
O3—C4	1.265 (8)	C3—C4	1.521 (6)
O4—C4	1.247 (8)	C1—H61	1.003 (10)
OW1—H11	0.848 (11)	C1—H62	0.999 (9)
OW1—H12	0.839 (12)	C3—H72	0.994 (10)
OW2—H22	0.908 (18)	C3—H71	1.002 (8)
O1···OW1	2.900 (8)	N2···O3^iii	2.545 (7)
O1···O4^iii	3.229 (7)	N2···O4	2.731 (6)
O1···N1	2.738 (7)	N2···OW1	3.023 (9)
O1···N2	3.174 (9)	N2···C4^iii	3.293 (5)
O1···OW1^ii	2.933 (9)	N2···O1	3.174 (9)
O1···OW2^ii	2.605 (9)	N2···N1	3.210 (7)
OW1···OW2^ii	3.077 (11)	N1···H22^i	2.884 (16)
OW1···OW2^iii	2.960 (11)	C2···N1^iii	3.395 (6)
OW1···OW3^iv	2.677 (11)	C2···C2^x	3.435 (10)
OW1···O1	2.900 (8)	C4···N2^vi	3.293 (5)
OW1···N2	3.023 (9)	C2···H41^iii	3.035 (10)
OW1···O1^ii	2.933 (9)	C2···H31	2.96 (6)
OW1···O4^iii	2.587 (9)	C2···H22^ii	2.622 (16)
OW1···OW1^ii	2.923 (11)	C2···H62^x	3.009 (14)
O2···N1^iii	2.637 (7)	C2···H42^iii	2.821 (10)
O2···OW3	2.780 (9)	C3···H41	2.953 (11)
OW2···OW1^ii	3.077 (11)	C3···H52^xi	2.937 (11)
OW2···O1^ii	2.605 (9)	C4···H51^vi	2.734 (9)
OW2···O4	3.097 (10)	C4···H12^vi	2.794 (12)
OW2···N1^i	2.845 (9)	C4···H41	2.826 (13)
OW2···OW3^v	2.719 (12)	C4···H52^vi	2.957 (11)
OW2···O4^i	3.031 (8)	C4···H32^vii	2.92 (4)
OW2···OW2^i	2.911 (11)	H11···OW3^iv	2.125 (14)
OW2···OW1^vi	2.960 (11)	H11···H22	2.50 (2)
O3···N2^vi	2.545 (7)	H11···H31^iv	2.48 (7)
O3···OW3^vii	2.702 (11)	H12···OW2^iii	2.715 (12)
OW3···OW1^viii	2.677 (11)	H12···OW3^iv	2.817 (13)
OW3···O2	2.780 (9)	H12···C4^iii	2.794 (12)
OW3···O3^vii	2.702 (11)	H12···H21^iii	2.54 (2)
OW3···OW2^ix	2.719 (12)	H12···O4^iii	1.772 (10)
O4···N2	2.731 (6)	H12···H22^ii	2.41 (2)
O4···OW2^i	3.031 (8)	H21···H31^v	2.56 (8)
O4···N1	2.930 (8)	H21···H32^v	2.37 (4)
O4···OW2	3.097 (10)	H21···OW1^vi	2.80 (2)
O4···O1^vi	3.229 (7)	H21···OW3^v	1.976 (19)
O4···OW1^vi	2.587 (9)	H21···H12^vi	2.54 (2)
O1···H12	2.639 (11)	H22···H11	2.50 (2)
O1···H22^ii	1.711 (18)	H22···O1^ii	1.711 (18)
O1···H11^ii	2.593 (13)	H22···C2^ii	2.622 (16)
OW1···H22	2.826 (18)	H22···H12^ii	2.41 (2)
OW1···H52	2.860 (12)	H22···H42^i	2.467 (16)
OW1···H21^iii	2.80 (2)	H31···C2	2.96 (6)
OW1···H22^ii	2.780 (17)	H31···H11^viii	2.48 (7)
O2···H31	1.93 (4)	H31···O2	1.93 (4)
O2···H42^iii	2.118 (11)	H31···H21^ix	2.56 (8)
O2···H41^iii	2.202 (11)	H32···C4^vii	2.92 (4)
OW2···H42^i	2.559 (12)	H32···O3^vii	1.92 (4)
OW2···H12^ii	2.656 (13)	H32···H21^ix	2.37 (4)
OW2···H12^vi	2.715 (12)	H41···C2^vi	3.035 (10)
O3···H51^vi	1.929 (10)	H41···O2^vi	2.202 (11)
O3···H32^vii	1.92 (4)	H41···H71	2.564 (15)
O3···H52^vi	2.258 (12)	H41···C3	2.953 (11)
OW3···H12^viii	2.817 (13)	H41···C4	2.826 (13)
OW3···H21^ix	1.976 (19)	H42···H22^i	2.467 (16)
OW3···H11^viii	2.125 (14)	H42···O2^vi	2.118 (11)
O4···H21	2.772 (15)	H42···C2^vi	2.821 (10)
O4···H41	2.700 (12)	H51···O3^iii	1.929 (10)
O4···H12^vi	1.772 (10)	H51···C4^iii	2.734 (9)
N1···O1	2.738 (7)	H52···C4^iii	2.957 (11)
N1···O2^vi	2.637 (7)	H52···O3^iii	2.258 (12)
N1···O4	2.930 (8)	H52···C3^xi	2.937 (11)
N1···OW2^i	2.845 (9)	H52···H72^xi	2.288 (14)
N1···C2^vi	3.395 (6)	H62···C2^x	3.009 (14)
N1···C3	3.353 (8)	H71···H41	2.564 (15)
N1···N2	3.210 (7)	H72···H52^xi	2.288 (14)
N1···C4	3.337 (9)
O1—Ca1—OW1	74.2 (2)	Ca1—OW2—H22	95.0 (10)
O1—Ca1—OW2	144.1 (3)	H21—OW2—H22	108.2 (19)
O1—Ca1—O4	138.1 (3)	Ca1—OW2—H21	94.7 (11)
O1—Ca1—N1	70.06 (16)	Ca1^i—OW2—H22	122.0 (13)
O1—Ca1—N2	82.9 (2)	Ca1^i—OW2—H21	120.7 (15)
O1—Ca1—OW2^i	112.0 (3)	H31—OW3—H32	111 (6)
O1—Ca1—OW1^ii	73.3 (3)	Ca1—N1—C1	111.7 (3)
OW1—Ca1—OW2	82.0 (3)	Ca1—N2—C3	111.1 (3)
OW1—Ca1—O4	125.4 (3)	Ca1—N1—H41	116.0 (7)
OW1—Ca1—N1	140.6 (2)	C1—N1—H41	105.5 (7)
OW1—Ca1—N2	76.5 (2)	C1—N1—H42	105.6 (7)
OW1—Ca1—OW2^i	139.6 (3)	Ca1—N1—H42	115.7 (7)
OW1—Ca1—OW1^ii	71.6 (3)	H41—N1—H42	101.2 (8)
OW2—Ca1—O4	77.7 (3)	Ca1—N2—H51	114.4 (7)
OW2—Ca1—N1	137.4 (2)	Ca1—N2—H52	115.4 (7)
OW2—Ca1—N2	117.5 (2)	C3—N2—H51	105.8 (8)
OW2—Ca1—OW2^i	70.8 (3)	C3—N2—H52	106.5 (7)
OW1^ii—Ca1—OW2	73.9 (2)	H51—N2—H52	102.8 (9)
O4—Ca1—N1	75.8 (2)	N1—C1—C2	115.8 (4)
O4—Ca1—N2	69.39 (16)	O1—C2—C1	116.3 (5)
OW2^i—Ca1—O4	78.0 (2)	O1—C2—O2	123.3 (5)
OW1^ii—Ca1—O4	144.2 (2)	O2—C2—C1	110.4 (5)
N1—Ca1—N2	83.0 (2)	N2—C3—C4	115.7 (5)
OW2^i—Ca1—N1	71.5 (2)	O3—C4—C3	115.0 (6)
OW1^ii—Ca1—N1	112.2 (2)	O3—C4—O4	126.0 (4)
OW2^i—Ca1—N2	142.6 (2)	O4—C4—C3	116.8 (4)
OW1^ii—Ca1—N2	144.2 (2)	N1—C1—H62	109.7 (6)
OW1^ii—Ca1—OW2^i	72.5 (3)	C2—C1—H61	108.7 (7)
Ca1—O1—C2	121.5 (4)	N1—C1—H61	108.0 (7)
Ca1—OW1—Ca1^ii	108.4 (3)	H61—C1—H62	105.6 (10)
Ca1—OW2—Ca1^i	109.2 (3)	C2—C1—H62	108.6 (8)
Ca1—O4—C4	121.8 (4)	N2—C3—H71	108.4 (8)
Ca1^ii—OW1—H12	99.8 (10)	N2—C3—H72	109.0 (7)
Ca1—OW1—H12	108.7 (9)	C4—C3—H72	109.5 (8)
H11—OW1—H12	129.7 (14)	H71—C3—H72	105.8 (11)
Ca1—OW1—H11	108.6 (10)	C4—C3—H71	108.0 (8)
Ca1^ii—OW1—H11	99.2 (10)
OW1—Ca1—O1—C2	156.0 (7)	N2—Ca1—N1—C1	−68.8 (4)
OW2—Ca1—O1—C2	−153.7 (6)	OW2^i—Ca1—N1—C1	138.9 (5)
O4—Ca1—O1—C2	30.1 (8)	OW1^ii—Ca1—N1—C1	77.5 (5)
N1—Ca1—O1—C2	−7.1 (6)	O1—Ca1—N2—C3	−129.2 (4)
N2—Ca1—O1—C2	78.0 (7)	OW1—Ca1—N2—C3	155.4 (4)
OW2^i—Ca1—O1—C2	−66.4 (7)	OW2—Ca1—N2—C3	82.0 (5)
OW1^ii—Ca1—O1—C2	−129.0 (7)	O4—Ca1—N2—C3	18.9 (4)
O1—Ca1—OW1—Ca1^ii	77.2 (3)	N1—Ca1—N2—C3	−58.5 (4)
OW2—Ca1—OW1—Ca1^ii	−75.6 (3)	OW2^i—Ca1—N2—C3	−11.9 (6)
O4—Ca1—OW1—Ca1^ii	−144.3 (3)	OW1^ii—Ca1—N2—C3	−177.2 (4)
N1—Ca1—OW1—Ca1^ii	102.9 (4)	O1—Ca1—OW2^i—Ca1^i	−141.7 (3)
N2—Ca1—OW1—Ca1^ii	163.5 (3)	OW1—Ca1—OW2^i—Ca1^i	−50.4 (5)
OW2^i—Ca1—OW1—Ca1^ii	−28.3 (5)	OW2—Ca1—OW2^i—Ca1^i	0.0 (3)
OW1^ii—Ca1—OW1—Ca1^ii	0.0 (3)	O4—Ca1—OW2^i—Ca1^i	81.0 (3)
O1—Ca1—OW2—Ca1^i	101.2 (4)	N1—Ca1—OW2^i—Ca1^i	159.9 (3)
OW1—Ca1—OW2—Ca1^i	149.7 (3)	N2—Ca1—OW2^i—Ca1^i	110.3 (4)
O4—Ca1—OW2—Ca1^i	−81.4 (3)	O1—Ca1—OW1^ii—Ca1^ii	−78.5 (3)
N1—Ca1—OW2—Ca1^i	−28.9 (5)	OW1—Ca1—OW1^ii—Ca1^ii	0.0 (3)
N2—Ca1—OW2—Ca1^i	−140.1 (2)	OW2—Ca1—OW1^ii—Ca1^ii	86.7 (3)
OW2^i—Ca1—OW2—Ca1^i	0.0 (3)	O4—Ca1—OW1^ii—Ca1^ii	125.5 (4)
OW1^ii—Ca1—OW2—Ca1^i	76.6 (3)	N1—Ca1—OW1^ii—Ca1^ii	−138.0 (2)
O1—Ca1—O4—C4	38.5 (9)	N2—Ca1—OW1^ii—Ca1^ii	−28.1 (5)
OW1—Ca1—O4—C4	−68.4 (8)	Ca1—O1—C2—O2	−145.8 (7)
OW2—Ca1—O4—C4	−139.2 (8)	Ca1—O1—C2—C1	−3.5 (9)
N1—Ca1—O4—C4	74.4 (7)	Ca1—O4—C4—O3	−157.7 (8)
N2—Ca1—O4—C4	−13.3 (7)	Ca1—O4—C4—C3	4.7 (11)
OW2^i—Ca1—O4—C4	148.2 (8)	Ca1—N1—C1—C2	−24.3 (6)
OW1^ii—Ca1—O4—C4	−177.2 (7)	Ca1—N2—C3—C4	−24.3 (7)
O1—Ca1—N1—C1	16.2 (4)	N1—C1—C2—O1	19.4 (9)
OW1—Ca1—N1—C1	−10.1 (6)	N1—C1—C2—O2	166.3 (6)
OW2—Ca1—N1—C1	167.7 (4)	N2—C3—C4—O3	178.7 (7)
O4—Ca1—N1—C1	−139.3 (4)	N2—C3—C4—O4	14.4 (11)

Symmetry codes: (i) −x+2, −y+2, −z; (ii) −x+2, −y+2, −z+1; (iii) x, y, z+1; (iv) x, y+1, z; (v) x, y+1, z−1; (vi) x, y, z−1; (vii) −x+1, −y+1, −z+1; (viii) x, y−1, z; (ix) x, y−1, z+1; (x) −x+2, −y+1, −z+1; (xi) −x+1, −y+2, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
OW1—H11···OW3^iv	0.848 (11)	2.125 (14)	2.677 (11)	122.4 (11)
OW1—H12···O4^iii	0.839 (12)	1.772 (10)	2.587 (9)	163.2 (13)
OW2—H21···OW3^v	0.913 (15)	1.976 (19)	2.719 (12)	137.3 (19)
OW2—H22···O1^ii	0.908 (18)	1.711 (18)	2.605 (9)	167.7 (18)
OW3—H31···O2	0.90 (6)	1.93 (4)	2.780 (9)	156 (7)
OW3—H32···O3^vii	0.90 (5)	1.92 (4)	2.702 (11)	144 (4)
N1—H41···O2^vi	0.961 (10)	2.202 (11)	2.637 (7)	106.2 (7)
N1—H42···O2^vi	0.955 (10)	2.118 (11)	2.637 (7)	112.6 (8)
N2—H51···O3^iii	0.953 (10)	1.929 (10)	2.545 (7)	120.1 (8)
N2—H52···O3^iii	0.947 (11)	2.258 (12)	2.545 (7)	96.5 (6)

Symmetry codes: (ii) −x+2, −y+2, −z+1; (iii) x, y, z+1; (iv) x, y+1, z; (v) x, y+1, z−1; (vi) x, y, z−1; (vii) −x+1, −y+1, −z+1.