Crystal structure and thermochromic behavior of the inclusion compounds of 4,5-diphenyl-2-(4-nitrophenyl)-1H-imidazole and of 4,5-diphenyl-2-(2-hydroxy-5-nitrophenyl)-1H-imidazole

4,5-Diphenyl-2-(4-nitrophenyl)-1H-imidazole 2 and 4,5-diphenyl-2-(2-hydroxy-5-nitrophenyl)-1H-imidazole 3 form inclusion compounds with various guest molecules that possess hydrogen donor or hydrogen acceptor groups. The guest molecules play a crucial role in building up the three-dimensional structure. The guest molecules link host molecules through hydrogen bonds. The colors of the solid compounds vary from light yellow to dark red. The thermochromic properties have been determined by the removal of the guest molecules. The crystal structure and the thermal behavior are described and discussed.