Structural diversity of copper(II) amino alcoholate complexes

Dinuclear vs. Mononuclear Copper(II) Coordination Species of Tylosin and Tilmicosin in Non-Aqueous Solutions

“…The ratio between the metal(II) cations and the macrolide antibiotics was confirmed by the elemental analysis data (Table 2), which in addition indicate the presence of one mole of nitrate anions (blue complexes) or two moles of chlorides (green complexes) per one mole of copper(II) ions, respectively. The overall neutral character of the species formed is secured by the deprotonation of the antibiotics in the blue complexes and their participation in the non-dissociated form in the green coordination compounds [21]. The observed elemental composition can be attributed to the formation of two possible constructs which contain one (mononuclear species, 2a'-b'/3a'-b') or two (dinuclear complexes, 2a-b/3a-b) metal(II) centers ligated by the corresponding number of antibiotic ligands and inorganic anions.…”

“…The 16-membered veterinary antibiotics contain a mycaminose substituent, which was already found to be the main coordination site of the mononuclear copper(II)-bismacrolidates, isolated under water-alkaline conditions [26]. The suitable position of the Nand OH-donor atoms in this sugar moiety (an aminoalcohol fragment) is a prerequisite for the formation of dinuclear Cu(II) complexes in non-aqueous solutions [21], which is why we assume that the blue and green coordination species contain a dinuclear chromophore and are of composition [Cu 2 (µ-NO 3 ) 2 L 2 ] (2a-b) and [Cu 2 (µ-Cl) 2 Cl 2 (HL) 2 ] (3a-b), respectively. The suggested dinuclear complexes can be constructed by two metal centers bound with two bidentate aminoalcohol(ate) fragments, which in addition serve as a bridge between the copper(II) ions (Scheme 2a,b).…”

“…Both saccharides contain a tertiary nitrogen atom and hydroxyl group(s) at close distance(s), capable of binding metal ions and forming 5-membered chelates. This N,O-bearing environment appears to be the main coordination site of the macrolides towards copper(II) ions and could play different roles in the formation of mono-, di-or polynuclear complex species depending on the reaction conditions applied [21].…”

“…The formation of these complex species is in agreement with the known data on various mononuclear bis-aminoalcoholates obtained under similar reaction conditions. On the other hand, the aminoalcohol-bearing ligands are able to form di-or polynuclear coordination species in non-aqueous solutions [21], which in turn leads to the following general questions: How will the macrolides behave in the presence of copper(II) ions in such an environment? What is the coordination mode of the antibiotics in non-polar media?…”

Structural diversity and magnetic properties of copper(ii) quinaldinate compounds with amino alcohols

“…29 A recent review describes the structural diversity of the copper(II) amino alcoholate complexes. 30 The most common structural type encountered is Cu(µ-OR) 2 Cu, a dinuclear core with copper(II) ions bridged by two amino alcoholate ( -OR) oxygen atoms. Owing to its rigid behavior, the dinuclear cores served as building units in the construction of metal-organic frameworks (MOFs) 31,32 whose dimensionality was controlled through denticity of the parent amino alcohol 23 .…”