Novel liquid crystal star-shaped based coumarin: Synthesis, characterization, phase behaviors and photoluminescence studies with DFT analysis

Two unconventional of symmetrical star-shaped molecules have been synthesized by employing 1,3,5-trihydroxybenzene (phloroglucinol) as a central core, which is connected to coumarin through ether flexible chain spacer. The molecular structure was fully characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance and elemental analysis. The phase transition and their thermal behaviors have been studied by combining differential scanning calorimetry, polarized optical microscopy. The analysis shows that the liquid crystal phase did not emerge in all synthesized star-shaped molecules. The absence of mesomorphic properties is confirmed in molecules with short spacer alkyl chains in both series. Moreover, nematic phase emergence was observed during the heating cycle. Physical properties such as Photo-Luminescence and decay lifetimes were also studied. These results indicate that an increase in the length of the carbon chain led to a significant effect on the Photo-Luminescence emission and delayed a decay time. The Density Functional Theory analysis confirms the star shape of molecules in the gas phase. Some molecules show significant dipole moment values, making them promising candidates for electrostatic field sensing applications.