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Crystal structure of the tetra­aqua­bis­­(thio­cyanato-κN)cobalt(II)–caffeine–water (1/2/4) co-crystal

aEquipe Métallation, Complexes Moléculaires et Applications, Université Moulay Ismail, Faculté des Sciences, BP 11201 Zitoune, 50000 Meknès, Morocco, bCNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, F-31077 Toulouse, France, and cUniversité de Toulouse, UPS, INPT, LCC, F-31077 Toulouse, France
*Correspondence e-mail: elhamdanihicham41@gmail.com

Edited by C. Rizzoli, Universita degli Studi di Parma, Italy (Received 30 May 2017; accepted 1 June 2017; online 7 June 2017)

In the structure of the title compound [systematic name: tetra­aqua­bis­(thio­cyanato-κN)cobalt(II)–1,3,7-trimethyl-1,2,3,6-tetra­hydro-7H-purine-2,6-dione–water (1/2/4)], [Co(NCS)2(H2O)4]·2C8H10N4O2·4H2O, the cobalt(II) cation lies on an inversion centre and is coordinated in a slightly distorted octa­hedral geometry by the oxygen atoms of four water mol­ecules and two N atoms of two trans-arranged thio­cyanate anions. In the crystal, the complex mol­ecules inter­act with the caffeine mol­ecules through O—H⋯N, O—H⋯O and C—H⋯S hydrogen bonds and ππ inter­actions [centroid-to-centroid distance = 3.4715 (5) Å], forming layers parallel to the ab plane, which are further connected into a three-dimensional network by O—H⋯O and O—H⋯S hydrogen bonds involving the non-coordinating water mol­ecules.

1. Chemical context

Compounds with supra­molecular metal–organic structures, which are diversified by their innovative applications, attract attention in various fields such as non-linear optical activity, catalysis, electrical conductivity, and cooperative magnetic behavior (Fan et al., 2016[Fan, G., Deng, L.-J., Ma, Z.-Y., Li, X.-B., Zhang, Y.-L. & Sun, J.-J. (2016). Chin. J. Struct. Chem. 35, 100-106.]). In particular, the supra­molecular complexes of mixed metals and ligands that possess active pharmaceutical ingredients (APIs) offers an approach to generate crystalline materials that form pharmaceutical co-crystals to effect therapeutic parameters such as solubility and lipophilicity (Ma & Moulton, 2007[Ma, Z. & Moulton, B. (2007). Mol. Pharm. 4, 373-385.]). The properties of caffeine as a pharmaceutical compound exhibiting moisture instability with the formation of a non-stoichiometric crystalline hydrate have been widely studied. Caffeine is a stimulant of the central nervous system and a smooth muscle relaxant, and is used as a formulation additive to analgesic remedies (Trask et al., 2005[Trask, A. V., Motherwell, W. D. S. & Jones, W. (2005). Cryst. Growth Des. 5, 1013-1021.]). Caffeine has attractive effects on various biological systems, including cardiovascular, gastrointestinal, respiratory and muscle systems (Taşdemir et al., 2016[Taşdemir, E., Özbek, F. E., Sertçelik, M., Hökelek, T., Çelik, R. Ç., & Necefoğlu, H. (2016). J. Mol. Struct. 1119, 472-478.]), and forms complexes with transition metals having different coordination and biological properties such as anti-inflammatory and anti­bacterial (Taşdemir et al., 2016[Taşdemir, E., Özbek, F. E., Sertçelik, M., Hökelek, T., Çelik, R. Ç., & Necefoğlu, H. (2016). J. Mol. Struct. 1119, 472-478.]). Thio­cyanate is a commonly used ligand because of its numerous bonding modes to one or more transition metal ions, and provides useful precursors for numerous coordination complexes. Usually, the thio­cyanate anion bonds terminally through the nitro­gen atom with first-row transition metals, and can act as a hydrogen-bond acceptor through the nitro­gen or sulfur atom (Bie et al., 2005[Bie, H. Y., Lu, J., Yu, J. H., Xu, J., Zhao, K. & Zhang, X. (2005). J. Solid State Chem. 178, 1445-1451.]).

[Scheme 1]

2. Structural commentary

The asymmetric unit of the title compound (Fig. 1[link]) contains half a complex mol­ecule of formula [Co(NCS)2(H2O)4], a caffeine mol­ecule and two free water mol­ecules. The cobalt(II) cation lies on an inversion centre and displays a trans-arranged octa­hedral coordination geometry provided by the N atoms of two thio­cyanate anions and four O atoms of coordinating water mol­ecules. The Co1—N15 [2.0981 (8) Å] and Co1—O18 [2.0981 (7) Å] bond lengths are equal within standard uncertainties and significantly longer than the Co1–O19 bond length [2.0732 (7) Å], and therefore the CoN2O4 octa­hedron is slightly axially compressed. This structural feature is typical for related compounds (Shylin et al., 2013[Shylin, S. I., Gural'skiy, I. A., Haukka, M. & Golenya, I. A. (2013). Acta Cryst. E69, m280.], 2015[Shylin, S. I., Gural'skiy, I. A., Bykov, D., Demeshko, S., Dechert, S., Meyer, F., Hauka, M. & Fritsky, I. O. (2015). Polyhedron, 87, 147-155.]). The thio­cyanato ligands are bound through the nitro­gen atoms and are nearly linear [N15—C16—S17 = 177.81 (8)°], while the Co–NCS linkage is bent [C16—N15—Co1 = 167.35 (8)°]. Previously reported complexes with an N-bound NCS group possess similar structural features (Petrusenko et al., 1997[Petrusenko, S. R., Kokozay, V. N. & Fritsky, I. O. (1997). Polyhedron, 16, 267-274.]). The caffeine mol­ecule is nearly planar (r.m.s. deviation = 0.0346 Å), with a maximum deviation from the mean plane of 0.0404 (7) Å for atom N5.

[Figure 1]
Figure 1
The asymmetric unit [expanded for the cobalt(II) cation to show the full coordination sphere; primed atoms are related to the non-primed atoms by the symmetry operation −x + 2, −y + 1, −z + 1] of the title compound, with displacement ellipsoids drawn at the 50% probability level

3. Supra­molecular features

In the crystal, each complex mol­ecule inter­acts with four neighboring caffeine mol­ecules through classical O—H⋯N and O—H⋯O hydrogen bonds (Table 1[link]) involving the coordinating water mol­ecules as H-atom donors to form layers parallel to the ab plane. These planes are further enforced by C—H⋯S hydrogen bonds and ππ inter­actions occurring between centrosymmetrically related six-membered rings of the purine ring system [CgCgi = 3.4715 (5) Å; Cg is the centroid of the N3/N7/C4/C6/C8/C9 ring; symmetry code: (i) 1 − x, 2 − y, 1 − z; Fig. 2[link]], and are alternated by layers of non-coordinating water mol­ecules linked through O—H⋯O and O—H⋯S hydrogen bonds (Fig. 3[link]), leading to the formation of a three-dimensional network (Fig. 3[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C2—H21⋯S17i 0.97 2.83 3.7622 (9) 160.6
O20—H202⋯O21ii 0.86 1.98 2.8119 (11) 161.6
O19—H191⋯O21 0.86 1.91 2.7634 (10) 174.9
O18—H182⋯N3iii 0.85 2.01 2.8671 (11) 178.4
O21—H211⋯S17iv 0.88 2.38 3.2481 (7) 173.3
O21—H212⋯O20iv 0.87 1.97 2.8157 (11) 164.8
O20—H201⋯O12 0.85 2.02 2.8531 (10) 166.8
O19—H192⋯O14v 0.85 1.89 2.7460 (10) 178.5
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) x, y+1, z; (iii) x+1, y, z; (iv) [-x+2, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]; (v) -x+2, -y+1, -z+1.
[Figure 2]
Figure 2
Partial packing diagram of the title compound, showing the network of hydrogen bonds (orange dotted lines) and ππ inter­actions (purple dotted lines) linking complexes and caffeine mol­ecules into layers parallel to the ab plane.
[Figure 3]
Figure 3
Crystal packing of the title compound viewed down the a axis.

4. Synthesis and crystallization

In a glass tube, a solution of CoCl2·6H2O (129 mg, 1 mmol) in 5 ml of water and caffeine (194.19 mg, 1 mmol) in 10 ml of ethanol was added to a solution of potassium thio­cyanate (190 mg, 2 mmol) in 5 ml of water. Single crystals of the title compound suitable for X-ray analysis were grown after several months by slow evaporation of the solvent at room temperature.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All H atoms could be located in a difference-Fourier map, but those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H = 0.98, O—H = 0.82 Å) and with Uiso(H) set at 1.2–1.5 times of the Ueq of the parent atom, after which the positions were refined with riding constraints (Cooper et al., 2010[Cooper, R. I., Thompson, A. L. & Watkin, D. J. (2010). J. Appl. Cryst. 43, 1100-1107.]).

Table 2
Experimental details

Crystal data
Chemical formula [Co(NCS)2(H2O)4]·2C8H10N4O2·4H2O
Mr 707.61
Crystal system, space group Monoclinic, P21/c
Temperature (K) 120
a, b, c (Å) 10.65854 (19), 8.16642 (14), 18.0595 (3)
β (°) 96.4701 (15)
V3) 1561.93 (3)
Z 2
Radiation type Mo Kα
μ (mm−1) 0.75
Crystal size (mm) 0.25 × 0.20 × 0.20
 
Data collection
Diffractometer Oxford Diffraction Gemini
Absorption correction Multi-scan (CrysAlis PRO; Agilent, 2011[Agilent (2011). CrysAlis PRO. Agilent Technologies, Yarnton, England.])
Tmin, Tmax 0.78, 0.86
No. of measured, independent and observed [I > 2.0σ(I)] reflections 62568, 4002, 3693
Rint 0.023
(sin θ/λ)max−1) 0.689
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.023, 0.022, 1.13
No. of reflections 3586
No. of parameters 196
H-atom treatment H-atom parameters not refined
Δρmax, Δρmin (e Å−3) 0.36, −0.24
Computer programs: GEMINI (Oxford Diffraction, 2006[Oxford Diffraction (2006). Gemini User Manual. Oxford Diffraction, Abingdon, England.]), CrysAlis PRO (Agilent, 2011[Agilent (2011). CrysAlis PRO. Agilent Technologies, Yarnton, England.]), SIR92 (Altomare et al., 1994[Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.]), CRYSTALS (Betteridge et al., 2003[Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487.]) and CAMERON (Watkin et al., 1996[Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, Oxford, England.]). Weighting scheme: Chebychev polynomial, (Watkin, 1994[Watkin, D. (1994). Acta Cryst. A50, 411-437.]; Prince, 1982[Prince, E. (1982). In Mathematical Techniques in Crystallography and Materials Science. New York: Springer-Verlag.]).

Supporting information


Computing details top

Data collection: Gemini (Oxford Diffraction, 2006); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SIR92 (Altomare et al., 1994); 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).

(I) top
Crystal data top
[Co(NCS)2(H2O)4]·2C8H10N4O2·4H2OF(000) = 738
Mr = 707.61Dx = 1.504 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 26895 reflections
a = 10.65854 (19) Åθ = 4–29°
b = 8.16642 (14) ŵ = 0.75 mm1
c = 18.0595 (3) ÅT = 120 K
β = 96.4701 (15)°Block, orange
V = 1561.93 (3) Å30.25 × 0.20 × 0.20 mm
Z = 2
Data collection top
Oxford Diffraction Gemini
diffractometer
3693 reflections with I > 2.0σ(I)
Graphite monochromatorRint = 0.023
φ & ω scansθmax = 29.3°, θmin = 3.1°
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2011)
h = 1413
Tmin = 0.78, Tmax = 0.86k = 1010
62568 measured reflectionsl = 2424
4002 independent reflections
Refinement top
Refinement on FPrimary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.023H-atom parameters not refined
wR(F2) = 0.022 Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)]
where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)2]2 Ai are: 4.58 -1.83 2.76
S = 1.13(Δ/σ)max = 0.001
3586 reflectionsΔρmax = 0.36 e Å3
196 parametersΔρmin = 0.24 e Å3
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 0.1K.

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.52963 (7)0.70159 (10)0.44118 (4)0.0159
N30.39238 (7)0.69668 (10)0.52732 (4)0.0165
N50.50891 (7)0.88202 (9)0.61607 (4)0.0138
N70.70166 (7)0.97981 (10)0.57845 (4)0.0148
N150.87722 (7)0.56972 (10)0.57738 (4)0.0177
C20.42006 (9)0.64292 (12)0.46092 (5)0.0177
C40.49202 (8)0.79469 (11)0.55076 (5)0.0134
C60.61761 (8)0.97269 (11)0.63265 (5)0.0145
C80.68939 (8)0.89801 (11)0.50972 (5)0.0140
C90.57826 (8)0.80031 (11)0.49965 (5)0.0138
C100.58693 (10)0.66144 (13)0.37365 (5)0.0214
C110.41902 (9)0.86319 (12)0.67132 (5)0.0187
C130.81636 (9)1.07902 (13)0.59652 (6)0.0212
C160.82097 (8)0.58619 (11)0.62832 (5)0.0146
O120.63887 (6)1.04807 (9)0.69164 (4)0.0199
O140.76700 (6)0.91542 (9)0.46473 (4)0.0191
O181.14207 (7)0.63274 (10)0.56379 (4)0.0243
O191.04404 (7)0.29467 (9)0.56531 (4)0.0202
O200.85940 (7)1.15725 (10)0.78244 (4)0.0218
O211.04346 (7)0.33657 (9)0.71711 (4)0.0227
S170.73704 (2)0.60472 (3)0.699098 (13)0.0206
Co11.00000.50000.50000.0133
H210.36740.56830.42930.0226*
H1030.66970.61050.38740.0339*
H1020.59580.76140.34460.0343*
H1010.53020.58350.34480.0347*
H1110.43970.94200.71120.0299*
H1120.33390.88280.64710.0298*
H1130.42580.75330.69210.0310*
H1310.85461.09640.55130.0326*
H1320.79421.18470.61720.0322*
H1330.87411.02110.63280.0327*
H1811.13980.64630.60980.0378*
H2020.90341.22950.76180.0364*
H1911.04280.30140.61270.0336*
H1821.21640.65380.55310.0384*
H2111.10730.28090.73940.0376*
H2121.05910.44090.71760.0382*
H2010.79201.14120.75380.0355*
H1921.10200.22920.55520.0330*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0180 (4)0.0155 (4)0.0136 (3)0.0004 (3)0.0001 (3)0.0018 (3)
N30.0150 (3)0.0163 (4)0.0178 (4)0.0018 (3)0.0000 (3)0.0004 (3)
N50.0130 (3)0.0168 (4)0.0119 (3)0.0009 (3)0.0028 (3)0.0008 (3)
N70.0127 (3)0.0175 (4)0.0140 (3)0.0031 (3)0.0010 (3)0.0002 (3)
N150.0152 (3)0.0229 (4)0.0155 (3)0.0010 (3)0.0039 (3)0.0018 (3)
C20.0164 (4)0.0178 (4)0.0185 (4)0.0015 (3)0.0005 (3)0.0012 (3)
C40.0133 (4)0.0136 (4)0.0132 (4)0.0012 (3)0.0007 (3)0.0012 (3)
C60.0140 (4)0.0156 (4)0.0135 (4)0.0007 (3)0.0002 (3)0.0007 (3)
C80.0137 (4)0.0141 (4)0.0140 (4)0.0024 (3)0.0012 (3)0.0023 (3)
C90.0149 (4)0.0146 (4)0.0120 (4)0.0011 (3)0.0011 (3)0.0000 (3)
C100.0269 (5)0.0228 (5)0.0152 (4)0.0007 (4)0.0058 (4)0.0028 (4)
C110.0177 (4)0.0244 (5)0.0152 (4)0.0010 (4)0.0067 (3)0.0006 (3)
C130.0154 (4)0.0269 (5)0.0208 (4)0.0084 (4)0.0000 (3)0.0009 (4)
C160.0139 (4)0.0147 (4)0.0146 (4)0.0021 (3)0.0005 (3)0.0003 (3)
O120.0199 (3)0.0232 (3)0.0163 (3)0.0028 (3)0.0006 (2)0.0052 (3)
O140.0172 (3)0.0224 (3)0.0190 (3)0.0006 (3)0.0071 (2)0.0021 (3)
O180.0175 (3)0.0413 (4)0.0147 (3)0.0121 (3)0.0044 (2)0.0074 (3)
O190.0212 (3)0.0232 (3)0.0173 (3)0.0041 (3)0.0063 (2)0.0018 (3)
O200.0203 (3)0.0300 (4)0.0146 (3)0.0021 (3)0.0004 (2)0.0011 (3)
O210.0241 (3)0.0246 (4)0.0195 (3)0.0044 (3)0.0020 (3)0.0047 (3)
S170.01944 (11)0.02902 (12)0.01456 (10)0.00462 (9)0.00757 (8)0.00446 (9)
Co10.01068 (8)0.01859 (9)0.01093 (8)0.00186 (6)0.00259 (5)0.00104 (6)
Geometric parameters (Å, º) top
N1—C21.3469 (12)C10—H1020.980
N1—C91.3820 (11)C10—H1010.985
N1—C101.4616 (12)C11—H1110.972
N3—C21.3407 (12)C11—H1120.975
N3—C41.3588 (12)C11—H1130.972
N5—C41.3727 (11)C13—H1310.963
N5—C61.3792 (11)C13—H1320.980
N5—C111.4672 (11)C13—H1330.969
N7—C61.4006 (11)C16—S171.6476 (9)
N7—C81.4027 (11)O18—Co12.0981 (7)
N7—C131.4723 (11)O18—H1810.842
N15—C161.1610 (12)O18—H1820.853
N15—Co12.0981 (8)O19—Co12.0732 (7)
C2—H210.969O19—H1910.860
C4—C91.3749 (12)O19—H1920.853
C6—O121.2291 (11)O20—H2020.864
C8—C91.4226 (12)O20—H2010.846
C8—O141.2314 (11)O21—H2110.877
C10—H1030.982O21—H2120.868
C2—N1—C9105.49 (7)H111—C11—H112110.1
C2—N1—C10126.68 (8)N5—C11—H113109.5
C9—N1—C10127.76 (8)H111—C11—H113109.0
C2—N3—C4103.21 (8)H112—C11—H113110.5
C4—N5—C6119.42 (7)N7—C13—H131108.3
C4—N5—C11119.83 (7)N7—C13—H132109.8
C6—N5—C11120.37 (7)H131—C13—H132109.6
C6—N7—C8126.55 (7)N7—C13—H133109.2
C6—N7—C13116.65 (7)H131—C13—H133110.3
C8—N7—C13116.77 (7)H132—C13—H133109.6
C16—N15—Co1167.35 (8)N15—C16—S17177.81 (8)
N1—C2—N3113.89 (8)Co1—O18—H181120.7
N1—C2—H21122.0Co1—O18—H182127.7
N3—C2—H21124.1H181—O18—H182109.1
N5—C4—N3126.58 (8)Co1—O19—H191119.2
N5—C4—C9121.78 (8)Co1—O19—H192120.6
N3—C4—C9111.64 (8)H191—O19—H192110.2
N7—C6—N5117.28 (8)H202—O20—H201107.9
N7—C6—O12120.99 (8)H211—O21—H212111.4
N5—C6—O12121.70 (8)O18i—Co1—O18179.995
N7—C8—C9111.93 (7)O18i—Co1—N15i87.69 (3)
N7—C8—O14121.76 (8)O18—Co1—N15i92.31 (3)
C9—C8—O14126.29 (8)O18i—Co1—N1592.31 (3)
C8—C9—N1131.30 (8)O18—Co1—N1587.69 (3)
C8—C9—C4122.88 (8)N15i—Co1—N15179.995
N1—C9—C4105.77 (8)O18i—Co1—O1989.86 (3)
N1—C10—H103109.4O18—Co1—O1990.14 (3)
N1—C10—H102109.5N15i—Co1—O1992.36 (3)
H103—C10—H102110.5N15—Co1—O1987.64 (3)
N1—C10—H101107.3O18i—Co1—O19i90.14 (3)
H103—C10—H101109.9O18—Co1—O19i89.86 (3)
H102—C10—H101110.2N15i—Co1—O19i87.64 (3)
N5—C11—H111108.8N15—Co1—O19i92.36 (3)
N5—C11—H112108.9O19—Co1—O19i179.994
Symmetry code: (i) x+2, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H21···S17ii0.972.833.7622 (9)160.6
O20—H202···O21iii0.861.982.8119 (11)161.6
O19—H191···O210.861.912.7634 (10)174.9
O18—H182···N3iv0.852.012.8671 (11)178.4
O21—H211···S17v0.882.383.2481 (7)173.3
O21—H212···O20v0.871.972.8157 (11)164.8
O20—H201···O120.852.022.8531 (10)166.8
O19—H192···O14i0.851.892.7460 (10)178.5
Symmetry codes: (i) x+2, y+1, z+1; (ii) x+1, y+1, z+1; (iii) x, y+1, z; (iv) x+1, y, z; (v) x+2, y1/2, z+3/2.
 

Acknowledgements

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

References

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