Modulating the Self-Assembly of Calix[4]azacrowns to Design Materials with Improved Emission and Stimuli-Responsive Behavior

1,3-[Ethylene-bis­(aminocarbonylmethyl)]-p-tert-butylcalix­[4]­arene is analyzed and its optical properties
are investigated, showing luminescence upon aggregation at low temperature
or in the solid state described as aggregation-induced blue emission.
The shift of the self-assembly from nanoporous to helical framework
in the crystal is associated with a remarkable blue-shift and 33-fold
increase in the fluorescence intensity. The purple-blue light emission
is highly efficient (ΦF ∼ 60%) and is switched
to thermally activated yellow emission as a stimuli-responsive behavior
of the helical assembly. The emitting material has been characterized
by single crystal and powder X-ray diffraction, ATR-FTIR spectroscopy,
and DSC and PLTM analysis, and its optical properties are investigated.