Crystal structure of the tetra-aqua-bis-(thio-cyanato-κ N)cobalt(II)-caffeine-water (1/2/4) co-crystal

Abstract

In the structure of the title compound [systematic name: tetra-aqua-bis-(thio-cyanato-κN)cobalt(II)-1,3,7-trimethyl-1,2,3,6-tetra-hydro-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 octa-hedral geometry by the oxygen atoms of four water mol-ecules and two N atoms of two trans-arranged thio-cyanate anions. In the crystal, the complex mol-ecules inter-act with the caffeine mol-ecules through O-H⋯N, O-H⋯O and C-H⋯S hydrogen bonds and π-π inter-actions [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 mol-ecules.

Keywords: caffeine; crystal structure; hydrogen bonding; single-crystal X-ray diffraction analysis.

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

Figure 2

Partial packing diagram of the title compound, showing the network of hydrogen bonds (orange dotted lines) and π–π inter­actions (purple dotted lines) linking complexes and caffeine mol­ecules into layers parallel to the ab plane.

Figure 3

Crystal packing of the title compound viewed down the a axis.