Anthracene-based ferrocenylselenoethers: Syntheses, crystal structures, Cu(i) complexes and sensing property

Three novel anthracene-based ferrocenylselenoethers, 1,5-diselena-3-(anthracen-9′-ylmethyl)-[5]ferrocenophane (L3), 1,3-bis(ferrocenylseleno)-2-(anthracen-9′-ylmethyl)propane (L4) and N,N-bis[2-(ferrocenylselena)ethyl]-N-(anthracen-9′-ylmethyl)amine (L5) and their Cu(i) complexes, [Cu₂Br₂(L2)₂] (L2 = 1,1′-bis[2-(anthracen-9′-yloxy)-ethylseleno]ferrocene) (1), [Cu₂I₂(L2)₂] (2), [Cu₂I₂(L3)₂]·1.25CH₂Cl₂ (3) and [Cu₄I₄(L5)₂]·CH₂Cl₂ (4), have been prepared and structurally characterized. The X-ray crystallography analysis reveals that the complexes 1-3 possess a rhomboidal Cu₂X₂ core which is sandwiched by two L ligands through two Se atoms to form a dimer, while 4 owns a distorted cubane-like Cu₄I₄ core which is double-bridging linked by two L5 ligands via two Se atoms to produce a 1D loop chain. Each Cu(i) ion in 1-4 displays a distorted tetrahedral geometry. The unique structural feature in L3-L5 is the coexistence of a redox moiety (ferrocenyl) and a fluorescent chromogenic group (anthracenyl). In the cation sensing study, L3 and L4 present multiresponsive signals for Cu²⁺ and Hg²⁺, L5 for Cu²⁺, Zn²⁺ and Hg²⁺. The selectivity can be tuned by incorporating an additional donor N atom, and/or oxidation of the ferrocene unit.