The Phane Properties of <i>a</i><i>nti</i>-[2.2](1,4)Biphenylenophane

anti-[2.2](1,4)Biphenylenophane (4) was synthesized from de Meijere's tetrabromo[2.2]paracyclophane (5) through a four-step reaction sequence. Although an average separation of 3.09 Å between the inner ring of the biphenylene units is normal for [2.2]paracyclophanes, a bond distance of 1.54 Å for the ethano C−C bridge at room temperature is shorter than usual. In addition, trimethylsilyl-substituted anti-[2.2](1,4)biphenylenophane 8 sublimes at 220 °C under a pressure lower than 1 × 10-5 Torr without decomposition or thermal isomerization. The high thermal stability of 8 suggested that the ethano bridges of the biphenylenophanes are less strained than those of [2.2]paracyclophane. Bathochromic shifts are observed in their UV−vis absorption spectra. The phane state interactions of 4 and 8 were evidenced by the weak structureless fluorescent emission maximized at 537 and 550 nm in CH2Cl2 along with longer relaxation lifetimes of 229 and 292 ps, respectively.