Aza-bridged bis-1,10-phenanthroline acyclic derivatives: synthesis, structure, and regioselective alkylation

A family of acyclic aza-bridged bis-1,10-phenanthroline compounds has been synthesized in a convenient way. The resulting compounds 2 and 2·HCl were fully characterized and their solid state structures and NMR spectroscopic properties were investigated to assess how the structural units affect the alkylation reactions. The results reveal the transoid structure for 2. The broadening NMR peak in 2 is shown to be due to an unusual intramolecular CH?N hydrogen bond. This unique conformation offers an efficient and regioselective method to prepare the amino-substituted bis-2,2′-1,10-phenanthroline derivatives and 1,10-phenanthrolino-N-alkylated compounds.