Crystal structure of bis{μ₂-2,2′-[(4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(methylene)]bis(4-oxo-4H-pyran-3-olato)}dicobaltcalcium bis(perchlorate) 1.36-hydrate

Abstract

The title compound, [CaCo 2 (C 22 H 30 N 4 O 6 ) 2 ](ClO 4 ) 2 Á1.36H 2 O or {Ca[Co-(H -2 L1)] 2 }Á2ClO 4 Á1.36H 2 O {where L1 is 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane}, is a trinuclear complex whose asymmetric unit comprises a quarter of the {Ca[Co(H -2 L1)] 2 } 2+ trinuclear complex, half of a perchlorate ion and 0.34-water molecules. In the neutral [Co(H -2 L1)] moiety, the cobalt ion is hexacoordinated in a trigonal-prismatic fashion by the surrounding N 4 O 2 donor set. A Ca 2+ cation holds together two neutral [Co(H -2 L1)] moieties and is octacoordinated in a distorted trigonaldodecahedral fashion by the surrounding O atoms belonging to the deprotonated oxide and carbonyl groups of two [Co(H -2 L1)] units. The coordination of the Co II cation preorganizes L1 and an electron-rich area forms, which is able to host hard metal ions. The comparison between the present structure and the previously published ones suggests a high versatility of this ligand; indeed, hard metal ions with different nature and dimensions lead to complexes having different stoichiometry (mono-and dinuclear monomers and trinuclear dimers) or even a polymeric structure. The heterotrinuclear Co IICa II -Co II complexes are connected in three dimensions via weak C-HÁ Á ÁO hydrogen bonds, which are also responsible for the interactions with the perchlorate anions and the lattice water molecules. The perchlorate anion is disordered about a twofold rotation axis and was refined giving the two positions a fixed occupancy factor of 0.5. The crystal studied was refined as a twocomponent inversion twin [BASF parameter = 0.14 (4)]. Chemical contextPolynuclear metal complexes have long been studied due to their versatility. They find applications in many fields, ranging from molecular recognition to transport and catalysis (Gokel & Barbour, 2017;Weber & Gokel, 2012;Ambrosi et al., 2007a Ambrosi et al., ,b, 2008Ambrosi et al., , 2009aMartell & Hancock, 1996;Voegtle, 1996;Zelewsky, 1996;Lehn, 1988), to name just a few. Moreover, they find applications in the field of bioinorganic chemistry (Fanelli et al., 2016;Marchetti et al., 2015;Patra et al., 2014), for instance as anticancer agents (Bruijnincx & Sadler, 2008) and artificial metalloproteases (Suh & Chei, 2008).On the other hand, hard metal ions also find applications in the biological field. Both rare earth and alkaline earth metal ions are used in the biomedical field, in bioassays and bioimaging applications ( Structural commentaryThe title compound is a trinuclear complex cation of formula {Ca[Co(H -2 L1)] 2 }Á2ClO 4 Á1.36H 2 O and crystallizes in the tetragonal system in space group I4. In the {Ca[Co(H -2 L1)] 2 } 2+ trinuclear complex (Fig. 1), two neutral [Co(H -2 L1)] moieties are held together by the Ca 2+ cation, which is coordinated by oxygen atoms provided by the maltolate groups of the two complexes. The asymmetric unit comprises a quarter of the {Ca[Co(H -2 L1)] 2 } 2+ trinuclear complex, half of a perchlorate ion and 0.34 water mo...