Them-phenylene-bridged bis-oxazole 4,4′,5,5′-tetraphenyl-2,2′-m-phenylenedi-1,3-oxazole and its bulkily substituted analogue 4,4′,5,5′-tetrakis(4-tert-butylphenyl)-2,2′-m-phenylenedi-1,3-oxazole

Abstract

The title m-phenylene-bridged bis-oxazoles, C(36)H(24)N(2)O(2), (I), and C(52)H(56)N(2)O(2), (II), feature different aryl substituents in the 4- and 5-positions of the oxazole units. In the solid state, aside from the different twist of the peripheral aryl rings, the molecules show distinctly different conformations, with anti and syn orientations of the O and N atoms for (I) and (II), respectively. Connected with this property, in the crystal structure of (I), extensive π-stacking is found between the molecules, while the crystal structure of (II) only involves dimer formation as the prominent packing motif.