A New Series of Pyrimidine-Containing Linear Molecules: Their Elegant Crystal Structures and Intriguing Photophysical Properties

A new series of aza-substituted analogues 3−5 based on the 1,4-bis(phenylethynyl)benzene moiety have been synthesized by the selective Pd-catalyzed Sonogashira coupling reaction from 5-bromo-2-iodopyrimidine (1). In these linear molecules, the dipolar pyrimidine moiety is introduced as a probe to investigate factors that control the intermolecular interactions over the crystal engineering. The results reveal that the manner of packing changes both dipolar interactions between linear pyrimidine-containing molecules and transition moments simultaneously, resulting in remarkably different photophysical properties. Due to their versatile dipole−dipole and face-to-face π−π interactions in a crystal motif, further applications on the design of ordered crystalline materials for the field effect transistors are promising.