Abstract:

r-1,c-2, t-3, t-4-1,3-bis(4-biphenyl)-2,4-di(4-pyridyl)cyclobutane (II) was obtained in diluted sulfuric acid by photodimerization reaction. Its structure was determined by X-ray diffraction method. The crystal is monoclinic, space group is P21/n,with a=1.0038(2), b=1.8995(4), c=1.4647(3)nm, β=98.82(3)°, Z=4. The cyclobutane ring of II has puckered conformation. It was found that under short wave UV light II is easy to be photolyzed to reproduce its monomer trans-1-(4-biphenyl)-2-(4-pyridyl)ethene (E-I),and then the new formed E-I transforms to its cis-isomer(Z-I) through trans-cis isomerization. Finally, the equilibrium of isomerization establishes between E-I and Z-I. Photolysis of II or E-I will form the same isomerization mixture.

Key words: Crystal strueture, Photodimerization, Trans-cis isomerization