Comparative study of the photophysical and crystallographic properties of 4-(9H-pyreno[4,5-d]imidazol-10-yl)phenol and its alkylated derivatives

A para-hydroxyphenyl substituted pyrenoimidazole and two of its decylated derivatives were synthesized and characterized by UV-Vis absorption and fluorescence spectroscopic analyses. These compounds show significant UV-Vis absorption and fluorescence spectral responses to environmental acidity and basicity, suggesting application as sensitive fluorescence probes for pH. Their molecular structures and crystal packing properties were examined by single-crystal X-ray diffraction (SCXRD) analysis. With the aid of Hirshfeld surface analysis, the roles of various noncovalent forces, including hydrogen bonding, π-stacking, and CH⋯π interactions, in the formation of supramolecular assemblies in the solid state were elucidated.