Spectral, electrochemical and thermal characteristics of glass forming hydrazine derivatives

• We obtained π-conjugated compounds, that is, hydrazine derivatives.
• We analyze the influence of azines structure on their physical properties.
• They exhibited glass-forming properties and high thermal stability.
• They emitted blue light in a blend with PMMA.
• They undergo electrochemical oxidation and reduction processes.

The azines being condensation products of benzophenone hydrazone with triphenylamine substituted with different numbers of aldehyde groups and also with terephthaldicarboxaldehyde were prepared. Their spectral, thermal and electronic properties that is, orbital energies and resulting energy gap calculated theoretically by density functional theory (DFT) and estimated by electrochemical measurements were explored. The prepared hydrazine derivatives exhibited glass-forming properties with glass-transition temperatures in the range of 10–98 °C and high thermal stability with decomposition temperatures placed between 231 and 337 °C. The photoluminescence (PL) studies showed that all investigated compounds both in solid state as blends with PMMA and in NMP solution emitted blue light, however, with different intensity. Relative PL intensity of azines was investigated in NMP in relation to rhodamine-B used as a standard. Moreover, the stability of azines during doping with acid and ferric chloride was spectroscopically demonstrated via repeated doping/dedoping in solution and in film. All compounds are electrochemically active. Depend on chemical structure of azines they undergo reversible or irreversible electrochemical oxidation and reduction processes. The LUMO levels were found in the range from −2.66 to −3.0 eV. They exhibited energy band gap (Eg) estimated electrochemically from 2.57 to 3.22 eV.

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