Among the numerous applications of vibrational spectroscopy, the important ones concern structural investigations of chemical system. We used both IR-absorption and Raman scattering spectroscopies when examining tautomeric phenomena which take place in 9-acridinamine and its derivatives [1,2]. These compounds exhibit numerous biological activities, are used as model compounds in investigations and are fragments of commonly used drugs. We are currently investigating relations between the structure and features of vibrational spectra of 10-substituted 9-acridinones – the compounds which can be fragments of fluorescent labels and occur in products of reaction of various chemiluminescent labels, containing acridine skeleton, with hydrogen peroxide. Thermogravimetric and differential scanning calorimetry measurements with the exception of information on the thermal behaviour of systems investigated, provide thermochemical and kinetic characteristics to be undergone during heating processes. Thus we determined enthalpies of sublimation of 9-acridinamine and its derivatives from thermogravimetric traces and compared these with crystal lattice energies predicted theoretically [3]. Further, we investigated thermal decomposition of 10-methylacridinium halides – relatively simple aromatic quaternary salts – by TG-FTIR method, in order to reveal the decomposition pathway and determine the thermodynamic and kinetic characteristics for the process [4]. Similar aims appeared during investigations of the thermal dissociation of 1-methylpyridinum halides by TG-FTIR technique [5]. Using this method we are currently examining thermal dissociation of quaternary alkanaminium halides – hoping to obtain information on the decomposition pathways, as well as thermodynamics and kinetics of the process. These relatively simple compounds are very good models with which to verify basic phenomenological and theoretical descriptions of solid phase reaction thermodynamics and kinetics.

All thermogravimetric and spectroscopic measurements in the above described investigations were carried out on a Netzsch TG 209 thermobalance coupled to a Bruker IFS 66 FTIR spectrometer, Bruker FRA 106 FT- module connected with an FTIR system and Netzsch DCS 204 instrument.

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