Thermal,magnetic and spectral studies of metal-quinone complexes. Part II. Media effect on Coligation of Aqua Ligands |
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Authors: | Salunke Gawali S Dalvi R Ah Khursheed Rane S |
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Institution: | (1) Department of Chemistry, University of Pune, Pune, 411 007, India |
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Abstract: | Syntheses of phthiocol complexes with Cu(II) in inert media resulted in anhydrous monomer Cu-4: Cu(NQ)2] and dimer Cu-5: Cu(NQ)(NSQ)]2, however synthesis in air generates polymeric hydrated Cu-6: Cu(NQ)2(H2O)2]n. Media and colligation give rise to charge transfers in coordination compounds and lead to different redox ligations of 3-methyl-2-hydroxy-1,4-naphthoquinone.
These redox forms are determined from quantitization of activation energies (E
a) of different pyrolytic steps in TG using the rising temperature expression of Coats and Redfern. 'Tyrosinase'-type mechanism
is discussed for the redox-type ligation. Characteristic six-line EPR signals of dimeric Cu-5 lead to zero field splitting
parameters D=0.01608 cm-1and E=0.01576 cm-1. Cu-6 shows molecular association through hydrogen bonding. Variable temperature magnetic measurement data of Cu-6 from 6
to 300 K is fitted to the polymeric expression of Bonner and Fisher model. The best fit was obtained with antiferrromagnetic
exchange coupling constantJ=-2 cm-1, g=2.2 having R=4.2·10-4.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | polymer dimer Ea redox forms zfs (zero field split) |
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