Effect of Ligand Chain Length for Tuning of Molecular Dimensionality and Magnetic Relaxation in Redox Active Cobalt(II) EDOT Complexes (EDOT=3,4-Ethylenedioxythiophene)

Subrata Ghosh, Sujit Kamilya, Sakshi Mehta, Radovan Herchel, Mikhail Kiskin, Sergey Veber, Matvey Fedin, Abhishake Mondal

Research output: Contribution to journalArticlepeer-review

Abstract

Four cobalt(II) complexes, [Co(L1)2(NCX)2(MeOH)2] (X=S (1), Se (2)) and {[Co(L2)2(NCX)2]}n (X=S (3), Se (4)) (L1=2,5-dipyridyl-3,4,–ethylenedioxylthiophene and L2=2,5-diethynylpyridinyl-3,4-ethylenedioxythiophene), were synthesized by incorporating ethylenedioxythiophene based redox-active luminescence ligands. All these complexes have been well characterized using single-crystal X-ray diffraction analyses, spectroscopic and magnetic investigations. Magneto-structural studies showed that 1 and 2 adopt a mononuclear structure with CoN4O2 octahedral coordination geometry while 3 and 4 have a 2D [4×4] rhombic grid coordination networks (CNs) where each cobalt(II) center is in a CoN6 octahedral coordination environment. Static magnetic measurements reveal that all four complexes displayed a high spin (HS) (S=3/2) state between 2 and 280 K which was further confirmed by X-band and Q-band EPR studies. Remarkably, along with the molecular dimensionality (0D and 2D) the modification in the axial coligands lead to a significant difference in the dynamic magnetic properties of the monomers and CNs at low temperatures. All complexes display slow magnetic relaxation behavior under an external dc magnetic field. For the complexes with NCS as coligand observed higher energy barrier for spin reversal in comparison to the complexes with NCSe as coligand, while mononuclear complex 1 exhibited a higher energy barrier than that of CN 3. Theoretical calculations at the DFT and CASSCF level of theory have been performed to get more insight into the electronic structure and magnetic properties of all four complexes.

Original languageEnglish
Article numbere202200404
JournalChemistry - An Asian Journal
Volume17
Issue number16
Early online date26 May 2022
DOIs
Publication statusPublished - 15 Aug 2022

Keywords

  • cobalt
  • coordination polymers
  • luminescence
  • redox-active ligands
  • single molecule magnets

OECD FOS+WOS

  • 1.06 BIOLOGICAL SCIENCES
  • 1.04 CHEMICAL SCIENCES

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