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 CuII, 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.