Systematic investigation of the structure–property relationship of substituted <i>p</i>-alkoxy-azothiophenes

Differently substituted <i>p</i>-alkoxy azothiophenes with increasing alkoxy chains were systematically investigated in terms of their structure-property relationships. In particular, it was observed that increasing the length of the alkoxy chain had an unusual effect on the melting point, which did not follow the expected odd-even effect. It was also shown that changing the length of the alkoxy chain did not significantly affect the thermal half-life, a finding that disagrees with results reported in other studies. These observations provide valuable insights into structure-property relationships with important implications for the design and development of azobenzenes as molecular materials for various applications. Furthermore, each <i>p</i>-alkoxy azothiophene was investigated in terms of neat solid-state photoisomerisation or photoinduced liquefaction, which is a critical parameter for application as a molecular solar thermal phase-change (MOST-PCM) energy storage system.