Structure-redox potential relations of some tris(β-dicarbonylato)iron(III) chelates

Electronic effect of β‐diketonato ligands on the redox potential of fac and mer tris(β‐diketonato) iron(III) complexes: A density functional theory study and molecular electrostatic potential analysis

“…The experimental reduction potential (RP exp ) of the 16 tris(β‐diketonato)iron(III) complexes 1‐16 (Figure ) is reported to be an one‐electron (1e − ) reduction . In order to understand the possible effect of fac vs mer isomers on the reduction potential, as well as the nature of the electronic distributions in the neutral and reduced states (as a result of the differences in their R 1 and R 2 substituents), a computational study of the reduction potentials of 27 models of the 16 tris(β‐diketonato)iron(III) complexes is presented (Figure ), namely five complexes containing symmetrically substituted β‐diketonato ligands (complexes 1, 4, 5, 10, and 11, with R 1 = R 2 ) and 11 asymmetric complexes that can exist as both mer and fac isomers (complexes 2, 3, 6‐9, and 12‐16, with R 1 ≠ R 2 ).…”

“…Δ G s ( M ) and Δ G s ( M − ) in Equation are the solvation effects of the Gibbs free energy. Because the experimental reduction potentials are reported vs Fc/Fc + , the reference of the standard hydrogen electrode potential ( E SHE = 4.28 V) in Equation is changed to the absolute reduction potential of Fc/Fc + in acetonitrile solution (4.980 V) in all calculations in this study. The reduction potential from the second cycle is computed using the gas‐phase‐calculated adiabatic ionization energies (IPs, the enthalpy changes of one‐electron reactions in the gas phase), an entropy term (TΔS, where ΔS is the gas‐phase entropy), and solvation energies (ΔΔ G sol from Equation ) as reported in literature, using Equation : …”

“…The experimental reduction potential of 16 derivatives of the tris(β‐diketonato)iron(III) complexes, with β‐diketonato(R 1 COCHCOR 2 ) ─ , with substituents R 1 and R 2 in different combinations of H, C 4 H 3 S, C 4 H 3 O, CH 3 , Ph, CF 3 , or C(CH 3 ) 3 , have been reported in the literature . Among these 16 derivatives, 11 of them with unsymmetrical substituents R 1 ≠ R 2 can exist as either fac or mer isomers (Figure ).…”

“…For example, an electrolyte based on the tris(acetylacetonato)iron(III)/(II) redox couple of tris(acetylacetonato)iron(III) showed a very high dye‐regeneration yield (>99%) when used in p‐type DSSCs . The reported experimental reduction potential of tris(β‐diketonato)iron(III) complexes ranges from −1.286 eV to 0.202 eV (expressed vs the ferrocene/ferrocenyl couple, Fc/Fc + ), depending on the electron withdrawing or donating tendency of the substituents at the R 1 and R 2 positions (Figure and Table ).…”

Mixed Ligand Complexes of Cobalt(II) – Synthesis, Structure, and Properties of Co4(thd)4(OEt)4

“…From the MS data in Table 2 it is seen that Co(thd)(dpd) is detected right up to 290°C which is highest temperature reached by the present MS apparatus. The existence of the complexes Cr(dpd) 3 [30,31], Fe(dpd) 3 [32,33], Co(dpd) 3 [34,35], and Cu(dpd) 2 [29,36] is already reported. The fragment Co(thd)(C 6 H 9 O 2 ) (true enough in very low abundance in the present MS spectra) indicates the existence of another new mixed-ligand Co II complex with a β-keto aldehyde [C 6 H 9 O 2 abbreviated dbd as a derivative of H(dbd) ϭ 3,3-dimethylbutane-1,2-dione].…”