2,2′-Bipyridines carrying a diazo moiety and their complexes with bis(hexafluoroacetylacetonato)copper: Synthesis, structures, electronic and magnetic properties of their photoproducts in frozen solutions

H. Morikawa, F. Imamura, Y. Tsurukami, T. Itoh, H. Kumada, Satoru Karasawa, N. Koga, H. Iwamura

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Abstract

4-(α-Diazobenzyl)-2,2′-bipyridine 2, diazodi{4-(2,2′-bipyridyl)}methane 3, and 1,3-benzenediyl{4-(4′-methyl-2.2°prime;-bipyridyl)diazomethane} 4 were prepared as new types of spin sources/magnetic couplers. The molecular structures of bipyridine ligands, 2, 3, 4, and [Cu(hfac)2·2] were revealed by X-ray analyses. Photolysis of 2, 3, 4, and their complexes with Cu(hfac)2 in MTHF frozen solutions at cryogenic temperature was followed by UV-Vis and EPR spectroscopy. UV-Vis and EPR spectra after photolysis showed strong two absorptions; at 508 and 471 nm for 2, and 511 and 476 nm for 3, and characteristic sets of EPR signals due to the triplet states; |D/hc|=0.418, and 0.436 cm-1 and |E/hc|=0.021 and 0.022 cm-1 for 2 and 3, respectively. Diazo compound 4 after photolysis also showed absorptions at 506 and 471 nm and EPR signals characteristic of a quintet. Their complexes with Cu(hfac)2 showed a red shift of 3-14 nm in the visible spectra and gave EPR spectra characteristic of the high-spin complexes under similar conditions. Magnetic susceptibility measurements on a SQUID magnetometer were carried out using a sample similar to the one employed in the UV-Vis and EPR studies. The field dependence of magnetization in frozen solution suggested that the ground-state spin multiplicities of the photoproducts of 2, 3, and 4 were triplet, triplet, and quintet, respectively. Similarly, those of their complexes with Cu(hfac)2 were quartet, quintet, and septet, respectively.

Original languageEnglish
Pages (from-to)493-502
Number of pages10
JournalJournal of Materials Chemistry
Volume11
Issue number2
DOIs
Publication statusPublished - Mar 15 2001

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All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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