CONTROL OF SOLID-STATE PHOTODIMERIZATION OF TRANS-CINNAMIC ACID BY DOUBLE SALT FORMATION WITH DIAMINES

By double salt formation, diamines can steer the solid-state [2+2] photodimerization of trans-cinnamic acid (1). Thus, the yields for the photodimerization were significant only in three double salts, i.e., the ones with tn and t- and c-chxn, which are assumed to have an overlap structure. The resultant photodimer is generally beta-truxinic acid, although in one case, epsilon-truxillic acid was formed. alpha-Truxillic acid was not produced from any of the double salts studied. The X-ray crystal structures of three double salts of low photoreactivity (1 . en, 1 . pen, 1 . hen) were consistent with Schmidt’s rule.