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

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 redoxactive luminescence ligands. All these complexes have been well characterized using single-crystal X-ray diffraction analyses, spectroscopic and magnetic investigations. Magnetostructural studies showed that 1 and 2 adopt a mononuclear structure with CoN 4 O 2 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 CoN 6 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 À as coligand observed higher energy barrier for spin reversal in comparison to the complexes with NCSe À 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.

Spin-state switching: chemical modulation and the impact of intermolecular interactions in manganese(iii) complexes

“…3–5 Among the numerous potentially developed molecular switchable magnetic systems, e.g. single-molecule magnets (SMMs), 6–13 single-chain magnets (SCMs), 14–16 metal-to-metal electron transfer (MMET), 17–24 valence tautomerism, 25 etc. , systems exhibiting spin crossover (SCO) are of particular importance due to their switchable and tunable magnetic, optical and electrical behaviors.…”

“…[3][4][5] Among the numerous potentially developed molecular switchable magnetic systems, e.g. single-molecule magnets (SMMs), [6][7][8][9][10][11][12][13] single-chain magnets (SCMs), [14][15][16] metalto-metal electron transfer (MMET), [17][18][19][20][21][22][23][24] valence tautomerism, 25 etc., systems exhibiting spin crossover (SCO) are of particular importance due to their switchable and tunable magnetic, optical and electrical behaviors. [26][27][28] SCO systems can lead to potential applications in information storage, sensors, molecular spintronics, or display devices.…”