Synthesis and properties of hyperbranched polyester polyacrylic acids and their metal complexes

Ferromagnetically Coupled Copper(II) Clusters Incorporated in Functionalized Boltorn H30 Hyperbranched Polymer Architecture: ESR, Magnetic Susceptibility Measurements, and Quantum-Chemical Calculations

“…The representative structure of the starting hyperbranched polymer ligand for the synthesis of transition complexes is shown in Figure 1. The copper(II) complex under study was synthesized by the reaction of copper(II) nitrate hydrate with the polymer ligand in aqueous ethanol according to the procedure described in ref (7) and precipitated as a green-blue powder, the IR spectrum of which was consistent with a tetrahedral coordination geometry.…”

“…6 It was found that the structures and compositions of coordination adducts of the carboxyl-functionalized dendritic oligomer on the basis of third-generation hyperbranched polyester polyol Boltorn H30 are quite sensitive to variation of the degree of functionalization. 7 Depending on the number of monofumaric ester groups per macromolecule, different types of complexes are formed even with the same metal ions. Surprisingly, the electron spin resonance (ESR) spectra of one of the synthesized copper(II) complexes with acid-functionalized Boltorn H30, specifically, the one containing six carboxylic acid groups on average per macromolecule, indicated the formation of a trinuclear ferromagnetically coupled cluster with a ground spin state of S = 3/2 in solid samples.…”

“…Moreover, further clarification of the dendritic structures of the complexes is additionally complicated by the fact that the infrared (IR), ultraviolet, and ESR studies indicate different geometries of coordination sites in solution and powder samples as a result of the coordination of solvent molecules to the metal ions. 7 However, the combination of the quantum-chemical approach and experimental studies of the magnetic properties by the methods of ESR and magnetic susceptibility measurements allowed us to gain insight into the structure of the coordination sites in the synthesized copper(II) complex with the dendritic ligand based on the Boltorn H30 polymer functionalized with fumaric acid residues in a molar ratio of 1:6. It should be noted that the only method to uncover structure–property relationships in this sort of “vague” systems seems to be to simulate their structure using computational techniques and to analyze their magnetic states at a molecular level by using a quantum-chemical approach.…”

“…The resulting hyperbranched polymers contain a different number of free carboxyl groups per macromolecule depending on the ratio of reagents and are capable of coordinating transition metals . It was found that the structures and compositions of coordination adducts of the carboxyl-functionalized dendritic oligomer on the basis of third-generation hyperbranched polyester polyol Boltorn H30 are quite sensitive to variation of the degree of functionalization . Depending on the number of monofumaric ester groups per macromolecule, different types of complexes are formed even with the same metal ions.…”

“…Depending on the number of monofumaric ester groups per macromolecule, different types of complexes are formed even with the same metal ions. Surprisingly, the electron spin resonance (ESR) spectra of one of the synthesized copper­(II) complexes with acid-functionalized Boltorn H30, specifically, the one containing six carboxylic acid groups on average per macromolecule, indicated the formation of a trinuclear ferromagnetically coupled cluster with a ground spin state of S = 3/2 in solid samples . It should be noted that trinuclear copper­(II) coordination systems are uncommon, especially considering that carboxylate complexes tend to form antiferromagnetically coupled binuclear structures with the “lantern” geometry as in well-known dimeric copper­(II) acetate .…”