Synthesis and study of three novel macrocyclic selena[n]ferrocenophanes containing a naphthalene unit

Three novel macrocyclic ligands, L1-L3, in which a ferrocene unit and a fluorescent moiety are linked to polyselena rings have been designed and prepared from 1,1′-bis(3-bromopropylseleno)ferrocene. Reaction of L with [M(NCMe)₄](PF₆)₂ (M = Pd and Pt) led to complexes [ML](PF₆)₂ (M = Pd and Pt). Crystal structure analysis revealed that after complexation, the macrocyclic ligand adopts the unusual c,c,c conformation due to intramolecular C-H⋯π interactions from the hydrogen atoms of ferrocene moieties to the naphthalene ring. Electrochemical studies showed that in [ML](PF₆)₂ (M = Pd and Pt) the half-wave potential of the 1,1′-ferrocenediyl group shifts to much more positive potentials due to electron density withdrawn from Se donor atoms. Electrochemical and optical measurements were used to calculate HOMO and LUMO levels as well as HOMO-LUMO band gaps. Results were compared and correlated with the differences in molecular structures.