Symmetrical and unsymmetrical ferrocenyl perylenediimides: Design, synthesis and properties

•Unsymmetrical and symmetrical ferrocenyl perylenediimides (PDIs) were synthesized.•Properties of symmetrical and unsymmetrical ferrocenyl PDIs were compared.•The extended π-conjugation leads to red shift in absorption.•Unsymmetrical PDIs show systematic tuning of fluorescence with nature of spacers.•Electrochemical studies show strong Donor-Acceptor interactions.

Symmetrical and unsymmetrical ferrocenyl perylenediimides (PDIs) 1–6 were designed and synthesized by the Sonogashira cross-coupling and nucleophilic aromatic substitution (SNAr) reactions. The PDIs were functionalized with ferrocenyl moiety through varying spacers to study the effect of one and two ferrocenyl units on their photophysical and electrochemical properties. The ferrocenyl unit and PDI were coupled through 3-phenylacetylene, 4-phenylacetylene and 4-phenoxy linkages to tune the electronic properties. The ferrocenyl PDIs show red shift in the absorption with the increasing conjugation. The efficient electronic communication between the ferrocenyl unit and PDI leads to the strong charge-transfer from donor ferrocene to the acceptor PDI core and quenching of fluorescence. The electrochemical studies reveal the effect of spacers on the Donor-Acceptor (D-A) interactions and electronic energy levels. The oxidation of ferrocenyl PDIs 1–6 are harder than free ferrocene indicating the considerable delocalization of ferrocenyl electrons on the PDI moiety. The experimental observations were adequately supported by theoretical calculations.

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