Thermodynamic considerations in co-ordination. Part XXI. Structures of copper(II)–asparaginate, –histidinate, and –threoninate ternary complexes in aqueous solution

Abstract

Thermodynamic-based structures are suggested for [Cu(AsnO)(HisO)], [Cu(AsnO)(HHisO)]⁺, [Cu(AsnO)-(ThrO)], [Cu(HisO)(ThrO)], and [Cu(HHisO)(ThrO)]⁺ in aqueous solution at 25 °C and I= 3.00M(Na[ClO₄]). Histidinate (HisO) appears to be tridentate to Cu^II, threoninate (ThrO) bidentate, and asparaginate (AsnO) ambivalent. The site of proton attachment in the protonated complexes is the primary amine nitrogen of histidinate (HHisO). Values of ΔG^⊖, ΔH^⊖, and ΔS^⊖ for formation of all these complexes are reported.