Cu(II)-complexes ofN-Salicylideneaniline Bull. Korean Chem. Soc. 2004, Vol. 25, No. 1 45 Photoreactivity and Thermogravimetry of Copper(II) Complexes of MS icylideneaniline and Its Derivatives Ahmed H. Osman,* Aref A. M. Aly, Mohamed Abd El-MottalebJ and Gamal A. H. Gouda' Chemistry Department, Faculty ofScience, Assiut University, Assiut 71561, Egypt 'Chemistry Department, Faculty ofScience, Al-Azhar University, Assiut, Egypt Received March 19, 2003 CuII-complexes of N-salicylideneaniline and its derivatives were not light sensitive in most solvents such as acetonitrile. A photo-decomposition occurred upon irradiation in halocarbon solvents such as CHCl3. It has been suggested that such photoreactivity is attributed to the reactivity of charge-transfer to solvent (CTTS) excited state attained upon irradiation. A mechanism has been proposed to account for the results obtained. The complexes have been thermally analysed in nitrogen and static air using thermogravimetry (TG) and derivative thermogravimetry (DTG). The thermal degradation of the complexes proceeds in two or three stages. The kinetic parameters obtained from the Coats-Redfern and Horowitz-Metzger equations show the kinetic compensation effect. Key Words : CuII-complexes of N-salicylideneaniline, Charge transfer to solvent (CTTS), Photochemistry, Thermogravimetry Introduction Schiff bases form stable complexes with metals that perform important role in biological systems.1 They find also wide applications in analytical chemistry since they allow simple and inexpensive determinations of several organic and inorganic substances. Furthermore, many Schiff bases exhibit antiviral and antibacterial activity and can also be regarded as mimetic systems for enzyme models.2,3 Some Schiff base complexes were found to be very effective catalysts for hydrolytic cleavage or transesterification of RNA phosphate diester backbone.4 Therefore metal complexes of Schiff bases attained a prominent place in coordination chemistry, which was shown over many years by the large number of publications5 and by the comprehensive reviews.6,7 In view of the above mentioned importance of Schiff bases and their complexes and due to the fact that few reports are known in the literature regarding photochemical8 and thermal behaviour9-11 of Schiff base complexes, we performed photolysis and thermogravimetric studies on CuII-complexes of N-salicylideneaniline and its derivatives (I) as a continuation of our previous interest in this respect. 12-14 Corresponding author. E-mail: ahosman@acc.aun.edu.eg Experimental Section Materials. All chemicals were of analytical grade. The CuII complexes, bis(N-salicylideneaniline)copper(II), [Cu(SA)2]; bis(N-salicylideneaniline)(dichloro)copper(II) dihydrate, [Cu(SA)2Cl2].2H2O; bis(N-salicylidene-o-anisidine)copper (II), [Cu(SOA)2]; bis(N-salicylidene-o-toluidine)copper(II), [Cu(SOT)2] and bis(salicylidene-p-toluidine)copper(II), [Cu(SPT)2] were prepared according to literature procedures.15 Photolyses. The light source was an Osram HBO 200 W/2 Lamp. Monochromatic light was obtained using the Scholt IL interference filter 298 nm. The photolyses were carried out in solutions of different solvents in 1 cm spectrophoto- meter cells at room temperature. Progress of the photolyses was monitored by using a UV-2101 PC shimadzu spectro- photometer. For quantum yield determinations the complex concentrations (〜10-2 M) were chosen so as to attain a complete light absorption. Absorbed light intensities were determined by ferrioxalate actinometry.16 The photoproducts were identified by their absorption spectra. The absorptions at the maxima of 330-350 nm were used to determine the concentration of the photoproducts (the free ligands) after substracting the absorbance of the starting complexes. It is to be noted that the photolyses in the presence of air and in deareated solutions (nitrogen atmosphere) are the same indicating that oxygen has no effect. Thermogravimetric analyses. Shimadzu TGA-50 H thermalanalyser was used for recording thermogravimetric data of the complexes in a dynamic nitrogen atmosphere (20 mL min-1) at a heating rate of 10 °C min-1. In static air the measurements were achieved using an electrobalance of the Sartorius 200 MP type, converted to a thermobalance by inclusion of a small furnace and sample holder. The temper- ature was monitored using a Chromel-Alumel thermocouple