Measurement of thermal diffusivity of some halogeno benzimidazole complexes of cobalt(Ii), copper (Ii) and copper(I) using laser induced photoacoustic effect

Abstract

The photoacoustic (PA) effect is an effective method fer obtaining information on the thermal and optical properties of materials [1-10]. The success of this JeW spectroscopic technique is mainly due to the &ct that only the absorbed light contributes to the ~gnal, giving a large signal to noise ratio. According !O the Rosencwaig-Gersho theory [3], the primary ~urce of the acoustic signal in the cell arises from Ihe periodic beat flow from the solid to the coupling mediwn, as the solid is cyclically heated by the ~rption of chopped light. The periodic flow of !his heat into the coupling medium produces pressure fluctuations, which are detected as an acoustic signal by microphone at the modulation frequency, f in this energy conversion (optical to acoustic), the thermal properties of the sample play a significant role. This suggests the possibility of using Ihc PA effect for the study of thermal properties of solids such as the thermal diffusivity and specific heat capacity. A search through the literature reveals that very few PA studies have been carried out on metal complexes and that no work has been reported on benzimidazole complexes. Complexes of benzimidazoles have attracted considerable attention in recent years. Benzimidazole derivatives have been reported to have antibacterial, antifungal, antiviral, antitumour, anticancer, antifiammatory. analgesic, antipyretic, antineoplastic, antihelmentic, germicidal and immW1o-chemical agent activities. Complex compounds of transition metal ions with imidazole, benzimidazole and their substituted ligands have been studied extensively [11-15]. Recently, many low molecular weight complexes of Cu(u) containing imidazole ligand ha~e been proposed as models of active sites of Cu proteins [16-18]. Incorporation of nitro groups in the azole compounds gives them anti-amoebic activity as well [19]. Some of the Co(lI) and CU(II) complexes reported have shown better catalytic activity, particularly in the synthetically ·important reaction of oxidation of substituted phenols, in which Co(u) and Cu(n) play a major role in catalysing these types of reactions. The structure of the ligand is shown in Fig. 1. Tn this letter, we report thermal studies of 1nitrobenzyl-2-nitrophenyl benzimidazole (NBPBI) complexes of CoCH), CU(II) and Cu(J) by laser induced photoacoustic techniques. Figure 1 Structure of the ligand (NBPBI).