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

Svetlana V Yurtaeva; Ildar F Gilmutdinov; Aleksandr A Rodionov; Ruslan B Zaripov; Marianna P Kutyreva; Olga V Bondar; Oleg V Nedopekin; Nail R Khafizov; Oleg N Kadkin

doi:10.1021/acsomega.9b02048

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

ACS Omega. 2019 Sep 30;4(15):16450-16461. doi: 10.1021/acsomega.9b02048. eCollection 2019 Oct 8.

Authors

Svetlana V Yurtaeva¹, Ildar F Gilmutdinov², Aleksandr A Rodionov², Ruslan B Zaripov¹, Marianna P Kutyreva³, Olga V Bondar³, Oleg V Nedopekin², Nail R Khafizov³, Oleg N Kadkin³

Affiliations

¹ Zavoisky Kazan Physical-Technical Institute, Federal Research Center Kazan Scientific Center, Russian Academy of Sciences, ul. Sibirskii Trakt 10/7, Kazan 420029 Russia.
² Institute of Physics, Kazan Federal University, ul. Kremlevskaya 16a, Kazan 420008, Russia.
³ Alexander Butlerov Institute of Chemistry, Kazan Federal University, ul. Lobachevskogo 1/29, Kazan 420008, Russia.

Abstract

The unusual temperature behavior of the electron spin resonance (ESR) spectra and magnetic properties are experimentally observed in copper(II) complexes with a dendritic ligand based on the Boltorn H30 polymer (Perstorp Specialty Chemicals AB, Sweden) functionalized with fumaric acid residues in a molar ratio of 1:6. The ESR spectra at low temperatures show signs of transition to higher spin states at temperatures below 8-10 K, and the temperature dependences of the integral ESR signal intensities and magnetic susceptibility show the positive deviation from the Curie-Weiss law, thereby pointing to the presence of ferromagnetic exchange interactions in the system under study. The values of the exchange interaction parameters are calculated by quantum-chemical simulation of the possible structure of the copper(II) complex when assuming the formation of trinuclear coordination sites embedded in the hyperbranched polymer structure. The results of density functional theory calculations indicate the possibility of ferromagnetic exchange through carboxylate bridges in the trinuclear magnetic clusters, and the calculated values of the exchange interaction parameters make it possible to construct theoretical curves of the temperature dependence of the effective magnetic moment, which satisfactorily fit the experimental data, especially considering that polymers are characterized by disperse molecular weights and chemical structures.