SQUID magnetic studies

Fig. 11 Implementation of the carbanion method for insoluble (gel forming) polyethers. Steps 1-4 correspond to swelling of polyether with THF-d8, generation of carbopolyanion, oxidation with removal of a Teflon-coated magnetic stirbar, and flame sealing of the quartz sample vessel for SQUID magnetic studies, respectively. Reproduced with permission from Ref. 62. Copyright 2004 Dr. Suchada Rajca.

SQUID magnetic studies indicate average values of S 6-7 and S % 10 for 54 and 55, respectively (Fig. 36). Values of Msat 0.6 /iB indicate that about 60% of unpaired electrons in the limit of very low temperature and high field for both polyradicals.113... 

The next higher homolog of 28-radical 55, 42-radical 56, in which six calix[4]arene rings were annelated to the center macrocycle, was prepared and studied. However, the SQUID magnetic studies gave relatively low average values of 5 9-12 and Msat 0.3 one of the possible reasons was insufficient purity of the 42-ether precursor of 56. 

EPR spectra of 58 at 140-150 K were obtained on the identical samples, for which SQUID magnetic studies were carried out. A single resonance at g 2 in the Aim, — 1 region was observed. For samples with the increasing values of S, the width of the resonance decreased and its propensity to microwave saturation greatly increased. These changes were mirrored by decreased intensity of the Ams — 2 signal.117... 

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