Open-chain polyamine ligands with more rigid double connecting bridges. Study of their metal ion selectivities by molecular mechanics calculation, crystallography, and thermodynamics

Ligands with two N-(2-aminoethyl), N-(3-aminopropyl), or N-acetate pendant groups on piperazine, homopiperazine or 1,5-diazacyclooctane are described. Protonation and formation constants of some of the complexes of these ligands with Cu(II), Ni(II), Zn(II), Cd(II), Pb(II), Ca(II), Sr(II), and Ba(II) are determined. Electronic spectra of the complexes with Cu(II) and low-spin Ni(II) are reported. The crystal structure of [Ni(BAP-HP)](ClO 4 ) 2 is reported (BAP-HP=1,4-bis(3-aminopropyl)-1,4-diazacycloheptane)