Synthesis, crystal structure, and luminescence of tetrakis(4-methoxyphenyl)methane

A new synthesis of a tetrahedral tecton, tetrakis(4-methoxyphenyl)methane, is reported. This compound exhibits a strong fluorescence around 340 nm at room temperature, both in solution and in the solid state. Upon crystallization, another luminescence band can be observed around 500 nm, attributed to phosphorescence. A study of the single-crystal structure of the compound provided a rationalization of this crystallization induced phosphorescence. The crystal of tetrakis(4-methoxyphenyl)methane belongs to the tetragonal space group P 4 ¯ 21c, and the structural analysis revealed a close packing of the molecules, with no void space and no solvent molecules in the crystal. The molecules are held together in a columnar array via multiple C–H⋯π hydrogen bonds. The hydrogen bonds between the molecules impede the torsional vibrations of the aromatic rings, preventing thermal relaxation from the triplet state, and hence promoting phosphorescence at room temperature.