The phane properties of anti-[2.2](1,4)biphenylenophane

structure: see text] Anti-2.2](1,4)biphenylenophane (4) was synthesized from de Meijere's tetrabromo2.2]paracyclophane (5) through a four-step reaction sequence. Although an average separation of 3.09 A between the inner ring of the biphenylene units is normal for 2.2]paracyclophanes, a bond distance of 1.54 Afor 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 degrees C under a pressure lower than 1 x10(-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 CH(2)Cl(2) along with longer relaxation lifetimes of 229 and 292 ps, respectively.