Authors:S. Salunke Gawali, R. Dalvi, Khursheed Ah and S. Rane
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 (Ea) 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.
Authors:S. Y. Rane, S. B. Padhye, G. N. Natu, A. H. Kumar and E. M. Khan
The solid-state deaquation of thetrans- andcis-oximates of lawsone (I) and phthiocol (II) with cobalt(II) was investigated by means of non-isothermal thermogravimetry. The modes of deaquation during the thermolyses of hydrated oximates of (I) and (II) with compositions CoL2·2H2O were compared. The weight lossvs. temperature data were treated by using the Coats and Redfern relations. The kinetic data support a rearrangement-type mechanism for the deaquation of the oximate of phthiocol. TheEa values for both the ligands and water molecules were found to be ∼23 kJ/mol.