Temperature Dependence of Calixarene Crystal Luminescence

Calixarene is methylene linked phenolic macrocycles available in several cavity sizes, and a variety of functional groups at the top and bottom rims of cavity. Calixarenes could have four possible geometrical structures such as cone, partial cone, 1,2-alternate, and 1,3-alternate. 12,13 The remarkable chemical property of calixarene is its ability to dissolve a wide variety of other compounds, both in solution and in the solid state. Calixarene forms inclusion compounds by dissolving other molecules to form crystalline solids. These inclusion compounds can be formed with essentially any guest. The selectivity and orientation of guest molecules in the cavity depend on the size and functional group of guest molecules. The calixarene crystals have well defined structures and stoichiometries and sufficiently small disorder that even atoms of the guest molecules can be located by Xray crystallography. 13 Calixarene may serve as a universal host for studies and utilization of optical phenomena in crystalline system, but essentially nothing is known about the optical properties of these material, although some characteristics have been reported. 14-16 Much of the photoluminescence work on calixarene has been conducted on porous silicon coated with calixarene, 14 on water-soluble calixarene, 15 or on Langmuir-Blodgett films. 16 Here we report the investigation of the photoluminescence of calixarene crystals as functions of temperature, time, and exciton concentration. The particular derivatives of calixarene interested in this study contain butyl groups on their upper rim and hydroxyl groups on the lower rim with four phenol moieties.