Design and synthesis of new tectons for halogen bonding-driven crystal engineering

The SNAr between oxygen or nitrogen nucleophiles and iodopentafluorobenzene is a versatile modular approach for the synthesis of telechelic alpha,omega-di-(2,3,5,6-tetrafIuoro-4-iodophenyl) derivatives 1. Despite the presence of a + M substituent in the para position to iodine, these derivatives are effective as halogen bond donors and form strong (IN)-N-... interactions with telechelic alpha,omega-di-(4-pyridyl) derivatives 2. In the resulting 1D infinite chains 3 the starting tectons alternate in an almost collinear fashion. The detailed structures of 3a and 3c were established through X-ray analyses. The overall structural pattern of these co-crystals is largely independent of the size of the starting tectons. Simple variation of the length of the spacers connecting recognition sites into telechelic modules constitutes a sort of metric engineering.