Redox responsive bi/tri-nuclear complexes incorporating ferrocenyl unit: Synthesis, characterization, physicochemical studies and X-ray structure of [C 5H 5FeC 5H 4CH  CHC 5H 4NCH 3]PF 6 with a mirror creating disorder

Abstract

( Trans-1(4-pyridyl)-ethylene) ferrocene, L reacts with K[Ru III(edtaH)]Cl to form binuclear complex. K[Ru III(edtaH)]Cl exist as Ru III(edtaH(H 2O) in aqueous solutions and substitution of the aqua molecule by L occurs within the stopped flow time scale. Rate constants for the reaction are 1620 ± 20, 2080 ± 35, 2690 ± 50 M −1 s −1 at 28, 34 and 39.9°C, respectively [ ΔH # is 30.3 ± 1.1 kJ mol −1 and ΔS # is − 124 ± 4 J K −1 mol −1]. R II(2,2′-bipy) 2Cl 2 reacts with L to form bi/trinuclear complexes. [Ru II(2,2′-bipy) 2LCl]PF 6 and [Ru II(2,2′-bipy) 2L 2](PF 6) 2, depending on the reaction conditions. Luminescence of the Ru II(2,2′-bipy) 2(py) 2 2+ center in the trinuclear complexes is completely quenched presumably through energy transfer pathway. There exist a moderate to weak electrochemical interaction between the two redox centers either in N-methylated form of L or in the bi/trinuclear complexes derived from Ru(II) or Ru(III). All these new bi/trinuclear complexes are characterized by physicochemical methods. Single crystal X-ray structure of [LCH 3]PF 0 is reported. A very low value of powder SHG efficiency observed earlier for this salt can now be well understood in terms of the centrosymmetric molecular arrangement created due to the disorder in the crystal.