Ionic, paramagnetic and photophysical properties of a new biohybrid material incorporating copper perchlorate

The sol-gel method was employed in the synthesis of di-urethane cross-linked poly(-caprolactone) (d-PCL(530)/siloxane biohybrid ormolytes incorporating copper perchlorate, (Cu(ClO4)2). The highest ionic conductivity of the d PCL(530)/siloxanenCu(ClO4)2 system is that with n = 10 (1.4 x 10-7 and 1.4 x 10-5 S cm-1, at 25 and 100 ºC, respectively). In an attempt to understand the ionic conductivity/ionic association relationship, we decide to inspect the chemical environment experienced by the Cu2+ ions in the d-PCL(530)/siloxane medium. The observed EPR spectra are typical of isolated monomeric Cu2+ ions in axially distorted sites. The molecular orbital coefficients obtained from the EPR spin Hamiltonian parameters and the optical absorption band suggests that bonding between the Cu2+ and its ligand in the ormolytes are moderately ionic. Investigation by photoluminescence spectroscopy did not evidence or allow selective excitation of transitions corresponding to complexed Cu2+ species.

We are grateful to the Fundação para a Ciência e Tecnologia and FEDER (PEst C/QUI/UI0686/2013) and grant SFRH/BD/90366/2012 (R. Leones), for financial support of this work. Drs. M. R. Dousti and L. P. Ravaro, from IFSC, are acknowledged for conducting the photoluminescence measurements. The financial support of the Brazilian agencies Capes and CNPq are gratefully acknowledged. Research was partially financed by the CeRTEV, Center for Research, Technology and Education in Vitreous Materials, FAPESP 2013/07793-6. M. M. Silva acknowledges CNPq, for the mobility grant provided by this institution.