Helical Figure-of-Eight Loop Dicopper(I) Compounds: Syntheses, Structures, and Dynamics.

The synthesis of a series of nine large macrocyclic ligands with two N(2)S(2) (thioether and Schiff-base imine) binding sites each, with different bridges between the donor atoms of each site (ethylene, o-xylylene, propylene, butylene) and different spacer groups between the two binding sites (p-xylylene, 2,5-dimethyl-p-xylylene, 2,5-dimethoxy-p-xylylene), and the synthesis of a similar ligand with a preorganized double-helical geometry, based on a paracyclophane spacer group, are reported, together with the syntheses and characterizations of the corresponding dicopper(I) compounds. The solid state structures of the dicopper(I) complexes have two tetrahedral copper(I) sites, separated by ca. 8 Å, and a figure-of-eight loop configuration of the ligand with a parallel arrangement of the two substituted benzene spacer groups (benzene.

Template synthesis of a tetraazamacrocyclic ligand with two pendant pyridinyl groups: properties of the isomers of the metal-free ligand and of their first-row transition metal compounds.

The one-step reaction of [Cu(en)(2)](2+) (en = 1,2-diaminoethane) with formaldehyde, ethyl 2-pyridyl acetate, and base produces a mixture of [Cu(s-pypymac)](2+) and [Cu(a-pypymac)](2+) (s-pypymac = syn-6,13-bis(2-pyridinyl)-1,4,8,11-tetraazacyclotetradecane, a-pypymac = anti-6,13-bis(2-pyridinyl)-1,4,8,11-tetraazacyclotetradecane; syn-to-anti ratio approximately 1:9) in low yield (6%). Ion exchange chromatography is used for isomer separation, and the two isomers of the metal-free ligand are obtained by reduction of the copper(II) complexes and subsequent ion exchange chromatography. Crystal structure analyses of the metal-free a-pypymac ligand, of two isomeric copper(II) compounds of a-pypymac and one of s-pypymac, and of the cobalt(III) complexes of a- and s-pypymac and nickel(II), as well as zinc(II) complexes of a-pypymac, are reported and discussed on the basis of the expectations from force field calculations and from published experimental data of the transition metal compounds of the bis-pendant amine derivative diammac.