Crystal Structures of Z and E ortho‐Tetrafluoroazobenzene

Abstract

AbstractThe crystal structures of Z‐ (Pna21, Z=4; single‐crystal X‐ray diffraction data) and E‐ortho‐tetrafluoroazobenzene (Pna21, Z=4; synchrotron powder diffraction data) were solved and refined. These structural analyses reveal that the phenyl rings are almost coplanar in the E isomer, whereas a tilting by 67.8(5)° was found in the Z isomer. This leads to significantly different molecular shapes (longest elongations 13.2 Å x 8.1 Å x 4.0 Å for the E isomer vs. 9.6 Å x 7.0 Å x 6.9 Å for the Z isomer). A comparison of the supramolecular structures of Z‐ and E‐ortho‐tetrafluoroazobenzene with other known fluorinated azobenzenes shows that mainly H…F interactions occur in both isomers of ortho‐tetrafluoroazobenzene, whereas H…F and F…F interactions exist in E‐4H,4H’‐octafluoroazobenzene, only F…F interactions in E‐perfluoroazobenzene, and N…C, F…C as well as F…F interactions in Z‐perfluoroazobenzene.