Estimation of energy levels of self-assembled ferrocenyls and investigation of charge-driven electro-crystallization of ferricenyl materials

Three tetra-ferrocenylethynylpyridinyl copper complexes, L₄(CuI)₄ (1), L₄(CuBr)₂ (2), L₄(CuCl)₂ (3) and one ferrocenylethynylpyridinyl Ligand (L) have been investigated for their HOMO and LUMO energy levels. The band gap energy for each material has been calculated using optical absorption spectrum. Cyclic Voltammetry was used to estimate the oxidation potential and energy band diagram consequently. Cyclic voltammetry in dichloroethane showed chemically reversible multiferrocenyl oxidation signals with evidence for product electro-crystallization. We isolated the semi-oxidized products by electrodeposition onto a Pt disc electrode and investigated by scanning electron microscopy (SEM). SEM confirmed the spontaneous formation of crystalline oxidation products with distinctive morphologies for complex 1 & 3. Energy dispersive X-ray elemental analysis shows presence of hexaflurophosphate (counter-ion) with the Fe:P ratio of 2:1, and 2:1 for the electrocrystallized products of 1 and 3, respectively proposing the formulae [1]²⁺(PF₆ ^-)₄ and [3]²⁺(PF₆ ^-)₂ for the electro-crystallized products.