Crystal structure of tetra­aqua­bis­(1,3-dimethyl-2,6-dioxo-7H-purin-7-ido-κN7)cobalt(II)

El Hamdani, H.; El Amane, M.; Duhayon, C.

doi:10.1107/S2056989017011379

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Volume 73| Part 9| September 2017| Pages 1302-1304

https://doi.org/10.1107/S2056989017011379

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Crystal structure of tetraaquabis(1,3-dimethyl-2,6-dioxo-7H-purin-7-ido-κN⁷)cobalt(II)

Hicham El Hamdani,^a Mohammed El Amane ^a and Carine Duhayon ^b,^c ^*

^aEquipe Metallation, Complexes Moleculaires et Applications, Universite Moulay, Ismail, Faculte des Sciences, Meknes, BP 11201 Zitoune, 50000 Meknes, Morocco, ^bLaboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France, and ^cUniversité de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, France
^*Correspondence e-mail: elhamdanihicham41@gmail.com

Edited by M. Weil, Vienna University of Technology, Austria (Received 18 July 2017; accepted 2 August 2017; online 4 August 2017)

The title complex, [Co(C₇H₇N₄O₂)₂(H₂O)₄], comprises mononuclear molecules consisting of a Co^II ion, two deprotonated theophylline ligands (systematic name: 1,3-dimethyl-7H-purine-2,6-dione) and four coordinating water molecules. The Co^II atom lies on an inversion centre and has a slightly distorted octahedral coordination environment, with two N atoms of two trans-oriented theophylline ligands and the O atoms of four water molecules. An intramolecular hydrogen bond stabilizes this conformation. A three-dimensional supramolecular network structure is formed by intermolecular O—H⋯O and O—H⋯N hydrogen bonds.

Keywords: crystal structure; theophylline; cobalt; hydrogen bonding.

CCDC reference: 1566195

1. Chemical context

Theophylline (systematic name: 1,3-dimethyl-7H-purine-2,6-dione) belongs to the family of xanthines, which are purine derivatives. It is related to dietary xanthines caffeine and theobromine and is an important pharmacologic compound (Shukla & Mishra, 1994 ). Usually, synthetic drugs of theophylline are used for the treatment of disorder in the physiological functions of the pulmonary system (Childs, 2004 ) because theophylline is a bronchodilator that is given against asthma and bronchospasm in adults (Chen et al., 2007 ).

The complexing ability of theophylline has been studied towards modelling metal interactions with the guanine base of nucleic acids (Orbell et al., 1988 ). Theophylline can be deprotonated in basic or neutral media. In the majority of cases, the resulting anionic ligand is monodentate and coordinates through the N7 atom of theophylline (Marzilli et al., 1973 ; Begum & Manohar, 1994 ; Bombicz et al., 1997 ; Buncel et al., 1985 ), while only in a few cases has a different coordination behaviour been reported, e.g. through the N9 atom of the imidazole ring (Aoki & Yamazaki, 1980 ). In addition, deprotonated theophylline may act as a bidentate ligand, where the initial metal bonding to N7 is supplemented by coordination to the O6 atom, forming an N7/O6 chelate (Cozak et al., 1986 ).

In this study, we reacted theophylline with the Co^II ion to yield the title complex, [Co(C₇H₇N₄O₂)₂(H₂O)₄].

2. Structural commentary

The molecular structure of the title complex is shown in Fig. 1. The complex lies across an inversion centre, with the Co^II atom being coordinated in a slightly distorted octahedral environment by four aqua ligands in the equatorial sites and the imidazole ring N atoms of two 1,3-dimethyl-2,6-dioxo-7H-purin-7-ide ligands [N1 and N1ⁱ; see Table 1 for symmetry code], in the axial sites. The Co—O bond lengths are shorter than the Co—N bond length (Table 1). The purine ring system is essentially planar, with a maximum deviation of 0.029 Å for N5; methyl atoms C10 and C12 deviate from this mean plane by −0.117 and 0.12 Å, respectively. The molecular conformation is stabilized by an intramolecular O—H⋯O hydrogen bond between a water molecule (O15) and a carbonyl O atom (O13) (Table 2), leading to an S(7) graph-set motif (Bernstein et al., 1995 ).

Table 1
Selected geometric parameters (Å, °)

N1—Co1	2.1847 (12)	O15—Co1	2.0756 (10)
O14—Co1	2.1022 (11)

N1—Co1—N1ⁱ	180	O14—Co1—O15ⁱ	91.42 (4)
N1—Co1—O14	88.00 (4)	N1—Co1—O15	90.47 (4)
Symmetry code: (i) -x, -y+1, -z+1.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O14—H142⋯O11ⁱⁱ	0.81	1.99	2.773 (2)	164
O15—H151⋯O13	0.83	1.82	2.638 (2)	173
O14—H141⋯O11ⁱⁱⁱ	0.81	2.01	2.817 (2)	174
O15—H152⋯N3^iv	0.82	2.01	2.799 (2)	162
Symmetry codes: (ii) -x+1, -y+1, -z+2; (iii) x, y, z-1; (iv) $[-x, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Figure 1
The molecular structure of the title complex. Primed atoms are related to the nonprimed atoms by the inversion centre of the title compound (symmetry code: −x, −y + 1, −z + 1). Displacement ellipsoids are drawn at the 50% probability level.

3. Supramolecular features

In the crystal, the mononuclear units are connected into a layered arrangement parallel to (010). The coordinating water molecules are involved in various hydrogen-bonding interactions (Table 2), including R₄²(8) graph-set motifs that are formed through (O14⋯O11ⁱⁱ = 2.817 (2) Å and O14⋯O11ⁱⁱⁱ = 2.773 (2) Å; see Table 2 for symmetry codes) between a coordinating water molecule and the carbonyl groups of symmetry-related theophylline ligands (Fig. 2). In addition, water molecule O15 is hydrogen bonded to the nonmethylated N atom of the imidazole group (O15⋯N3^iv = 2.799 (2) Å; see Table 2 for symmetry code), leading to an overall three-dimensional network.

Figure 2
The crystal structure, showing the overall three-dimensional hydrogen-bonded network (hydrogen bonds as dashed lines).

4. Synthesis and crystallization

Theophylline (360 mg, 2 mmol) was dissolved in water (20 ml). An aqueous solution (10 ml) of NaOH (80 mg, 2 mmol) was added slowly. CoCl₂·6H₂O (237 mg, 1 mmol) in water (10 ml) was then added. Pink single crystals of the title compound suitable for X-ray analysis were obtained after several months by slow evaporation of the solvent at room temperature.

5. Refinement

Details of data collection and structure refinement are summarized in Table 3. The calculated strategy was based on monoclinic chiral symmetry, with a completeness of 100%, an average multiplicity of 11.4 and no missing reflections. However, some reflections were still missing after data collection, thus reducing the completeness to less than 100%. All H atoms were located in a difference map, but those attached to C atoms were repositioned geometrically. The H atoms were refined with soft restraints on bond lengths and angles to regularize their geometry (C—H = 0.93–0.98 Å, N—H = 0.86–0.89 Å, N—H = 0.86 Å and O—H = 0.82 Å) and U_iso(H) values (in the range 1.2–1.5 times U_eq of the parent atom), after which the positions were refined with riding constraints (Cooper et al., 2010 ).

Table 3
Experimental details

Crystal data
Chemical formula	[Co(C₇H₇N₄O₂)₂(H₂O)₄]
M_r	489.31
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	175
a, b, c (Å)	7.6304 (3), 13.1897 (6), 9.6670 (4)
β (°)	104.9744 (17)
V (Å³)	939.87 (7)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.98
Crystal size (mm)	0.20 × 0.20 × 0.15

Data collection
Diffractometer	Nonius KappaCCD
Absorption correction	Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997 )
T_min, T_max	0.81, 0.86
No. of measured, independent and observed [I > 2.0σ(I)] reflections	41453, 1736, 1704
R_int	0.028
(sin θ/λ)_max (Å⁻¹)	0.604

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.021, 0.023, 1.00
No. of reflections	1686
No. of parameters	142
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.22
Computer programs: COLLECT (Nonius, 2001 )., DENZO/SCALEPACK (Otwinowski & Minor, 1997), APEX2 (Bruker, 2006 ), SUPERFLIP (Palatinus & Chapuis, 2007 ), CRYSTALS (Betteridge et al., 2003 ) and CAMERON (Watkin et al., 1996 ).

Supporting information

CCDC reference: 1566195

Crystal structure: contains datablocks global, New_Global_Publ_Block, I. DOI: https://doi.org/10.1107/S2056989017011379/wm5408sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017011379/wm5408Isup2.hkl

checkCIF report

Computing details top

Data collection: COLLECT (Nonius, 2001).; cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: APEX2 (Bruker, 2006); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).

Tetraaquabis(1,3-dimethyl-2,6-dioxo-7H-purin-7-ido-κN⁷)cobalt(II) top

Crystal data top

[Co(C₇H₇N₄O₂)₂(H₂O)₄]	F(000) = 506
M_r = 489.31	D_x = 1.729 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 9823 reflections
a = 7.6304 (3) Å	θ = 3–25°
b = 13.1897 (6) Å	µ = 0.98 mm⁻¹
c = 9.6670 (4) Å	T = 175 K
β = 104.9744 (17)°	Block, pale pink
V = 939.87 (7) Å³	0.20 × 0.20 × 0.15 mm
Z = 2

Data collection top

Nonius KappaCCD diffractometer	1704 reflections with I > 2.0σ(I)
Graphite monochromator	R_int = 0.028
φ & ω scans	θ_max = 25.4°, θ_min = 2.7°
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	h = −9→9
T_min = 0.81, T_max = 0.86	k = −15→15
41453 measured reflections	l = −11→11
1736 independent reflections

Refinement top

Refinement on F	Primary atom site location: other
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.021	H-atom parameters constrained
wR(F²) = 0.023	Method = Quasi-Unit weights W = 1.0 or 1./4Fsq
S = 1.00	(Δ/σ)_max = 0.0003458
1686 reflections	Δρ_max = 0.29 e Å⁻³
142 parameters	Δρ_min = −0.22 e Å⁻³
0 restraints

Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems open-flow nitrogen cryostat (Cosier & Glazer, 1986) with a nominal stability of 0.1 K.

Cosier, J. & Glazer, A.M., 1986. J. Appl. Cryst. 105-107.

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

	x	y	z	U_iso*/U_eq
N1	0.05846 (17)	0.45527 (9)	0.72491 (13)	0.0126
N3	0.04606 (18)	0.33836 (10)	0.89795 (13)	0.0151
N5	0.24314 (17)	0.42364 (10)	1.10036 (13)	0.0143
N7	0.34987 (17)	0.58201 (10)	1.04872 (13)	0.0139
C2	−0.0068 (2)	0.36737 (12)	0.75802 (16)	0.0143
C4	0.1522 (2)	0.41609 (11)	0.95762 (15)	0.0124
C6	0.3386 (2)	0.50912 (12)	1.14880 (16)	0.0145
C8	0.2695 (2)	0.57724 (11)	0.89958 (16)	0.0136
C9	0.16404 (19)	0.48879 (11)	0.85772 (15)	0.0119
C10	0.2355 (2)	0.34042 (13)	1.19853 (17)	0.0218
C12	0.4475 (2)	0.67528 (12)	1.10615 (17)	0.0196
O11	0.41386 (15)	0.52183 (9)	1.27770 (11)	0.0188
O13	0.29724 (16)	0.64754 (8)	0.82313 (12)	0.0206
O14	0.26896 (14)	0.46163 (9)	0.50496 (11)	0.0197
O15	0.08751 (15)	0.64646 (8)	0.55927 (11)	0.0172
Co1	0.0000	0.5000	0.5000	0.0103
H21	−0.0864	0.3279	0.6895	0.0161*
H103	0.3447	0.3423	1.2769	0.0336*
H101	0.1296	0.3467	1.2352	0.0345*
H102	0.2316	0.2770	1.1486	0.0330*
H121	0.4345	0.7242	1.0325	0.0318*
H122	0.4018	0.7025	1.1814	0.0314*
H123	0.5741	0.6614	1.1459	0.0311*
H142	0.3487	0.4654	0.5786	0.0298*
H151	0.1601	0.6467	0.6392	0.0273*
H141	0.3056	0.4824	0.4383	0.0306*
H152	0.0280	0.6987	0.5575	0.0275*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0148 (6)	0.0118 (6)	0.0100 (6)	−0.0004 (5)	0.0012 (5)	−0.0006 (5)
N3	0.0188 (7)	0.0135 (6)	0.0124 (6)	−0.0009 (5)	0.0031 (5)	0.0011 (5)
N5	0.0164 (6)	0.0158 (6)	0.0094 (6)	0.0006 (5)	0.0010 (5)	0.0024 (5)
N7	0.0138 (6)	0.0148 (6)	0.0114 (6)	−0.0019 (5)	0.0003 (5)	−0.0019 (5)
C2	0.0163 (7)	0.0135 (7)	0.0122 (7)	−0.0016 (6)	0.0019 (6)	−0.0014 (6)
C4	0.0125 (7)	0.0136 (7)	0.0109 (7)	0.0021 (6)	0.0026 (6)	0.0001 (6)
C6	0.0112 (7)	0.0191 (8)	0.0129 (7)	0.0028 (6)	0.0026 (6)	−0.0008 (6)
C8	0.0127 (7)	0.0150 (7)	0.0122 (7)	0.0020 (6)	0.0015 (6)	−0.0008 (6)
C9	0.0124 (7)	0.0129 (7)	0.0097 (7)	0.0015 (6)	0.0014 (5)	0.0002 (6)
C10	0.0312 (9)	0.0187 (8)	0.0139 (8)	0.0009 (7)	0.0030 (7)	0.0065 (6)
C12	0.0216 (8)	0.0177 (8)	0.0171 (8)	−0.0042 (7)	0.0004 (6)	−0.0049 (6)
O11	0.0170 (5)	0.0280 (6)	0.0089 (5)	−0.0012 (5)	−0.0008 (4)	−0.0012 (5)
O13	0.0272 (6)	0.0171 (6)	0.0141 (5)	−0.0082 (5)	−0.0008 (5)	0.0032 (5)
O14	0.0146 (5)	0.0329 (7)	0.0105 (5)	0.0010 (5)	0.0012 (4)	0.0005 (5)
O15	0.0236 (6)	0.0119 (5)	0.0125 (5)	0.0007 (5)	−0.0021 (4)	−0.0016 (4)
Co1	0.01218 (14)	0.00993 (14)	0.00793 (14)	−0.00056 (11)	0.00085 (10)	−0.00020 (11)

Geometric parameters (Å, º) top

N1—C2	1.333 (2)	C8—C9	1.416 (2)
N1—C9	1.3994 (18)	C8—O13	1.2375 (19)
N1—Co1	2.1847 (12)	C10—H103	0.971
N3—C2	1.363 (2)	C10—H101	0.966
N3—C4	1.341 (2)	C10—H102	0.962
N5—C4	1.3786 (19)	C12—H121	0.947
N5—C6	1.358 (2)	C12—H122	0.955
N5—C10	1.4620 (19)	C12—H123	0.961
N7—C6	1.382 (2)	O14—Co1	2.1022 (11)
N7—C8	1.4149 (19)	O14—H142	0.810
N7—C12	1.4706 (19)	O14—H141	0.813
C2—H21	0.933	O15—Co1	2.0756 (10)
C4—C9	1.380 (2)	O15—H151	0.826
C6—O11	1.2414 (18)	O15—H152	0.823

C2—N1—C9	102.52 (12)	H103—C10—H102	108.8
C2—N1—Co1	118.74 (10)	H101—C10—H102	109.7
C9—N1—Co1	138.49 (10)	N7—C12—H121	110.0
C2—N3—C4	101.73 (12)	N7—C12—H122	110.7
C4—N5—C6	119.43 (13)	H121—C12—H122	109.2
C4—N5—C10	120.08 (13)	N7—C12—H123	110.6
C6—N5—C10	120.48 (13)	H121—C12—H123	109.2
C6—N7—C8	126.39 (13)	H122—C12—H123	107.1
C6—N7—C12	115.76 (12)	Co1—O14—H142	120.9
C8—N7—C12	117.76 (13)	Co1—O14—H141	115.7
N3—C2—N1	116.71 (13)	H142—O14—H141	110.0
N3—C2—H21	121.3	Co1—O15—H151	110.6
N1—C2—H21	122.0	Co1—O15—H152	129.6
N5—C4—N3	125.28 (14)	H151—O15—H152	104.5
N5—C4—C9	122.90 (14)	N1—Co1—N1ⁱ	180
N3—C4—C9	111.81 (13)	N1—Co1—O14ⁱ	92.00 (4)
N7—C6—N5	117.44 (13)	N1ⁱ—Co1—O14ⁱ	88.00 (4)
N7—C6—O11	120.82 (14)	N1—Co1—O14	88.00 (4)
N5—C6—O11	121.74 (14)	N1ⁱ—Co1—O14	92.00 (4)
N7—C8—C9	113.12 (13)	O14ⁱ—Co1—O14	180
N7—C8—O13	118.63 (13)	N1—Co1—O15ⁱ	89.53 (4)
C9—C8—O13	128.25 (14)	N1ⁱ—Co1—O15ⁱ	90.47 (4)
C8—C9—N1	132.26 (13)	O14ⁱ—Co1—O15ⁱ	88.58 (4)
C8—C9—C4	120.50 (13)	O14—Co1—O15ⁱ	91.42 (4)
N1—C9—C4	107.23 (13)	N1—Co1—O15	90.47 (4)
N5—C10—H103	108.5	N1ⁱ—Co1—O15	89.53 (4)
N5—C10—H101	110.6	O14ⁱ—Co1—O15	91.42 (4)
H103—C10—H101	110.0	O14—Co1—O15	88.58 (4)
N5—C10—H102	109.2	O15ⁱ—Co1—O15	180

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O14—H142···O11ⁱⁱ	0.81	1.99	2.773 (2)	164
O15—H151···O13	0.83	1.82	2.638 (2)	173
O14—H141···O11ⁱⁱⁱ	0.81	2.01	2.817 (2)	174
O15—H152···N3^iv	0.82	2.01	2.799 (2)	162

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

Acknowledgements

The authors would like to thank the LCC CNRS (Laboratory of Chemistry of Coordination) for their help.

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