Complexation Stabilized Conformational Regulation of Ferrocene Bearing Podand Dipeptide Chains (- l -Ala- l -Pro-NHPy)

The structural characterization of the palladium complex of the ferrocene 1 bearing podand dipeptide chains (- l -Ala- l -Pro-NHPy) was demonstrated. The ferrocene 1 forms the 1:1 trans complex 2 with PdCl 2 (MeCN) 2 to stabilize the intramolecular conformational regulation in both solution and solid states. The crystal structure of 2 revealed a pseudohelical conformation through palladium binding and chirality organization via sterically constrained moieties (Pro) and intramolecular hydrogen bondings between CO (Ala) and NH (another Ala) of each podand dipeptide chain (N(1)···O(2*), 2.88 Å; N(1*)···O(2), 2.97 Å), giving a 10-membered hydrogen-bonded ring. Such an ordered conformation was supported by the induced circular dichroism. Another noteworthy feature of the ferrocene 1 is its strong tendency to self-assemble through participation of all available hydrogen-bonding donors in the solid state.