Steric, electronic and solvation effects in the co-ordination of amines by the [Fe(CN)5(OH2)]3− ion

Abstract

Equilibrium constants K for the substitution of co-ordinated H 2 O in [Fe II (CN) 5 (OH 2 )] 3Ϫ by sterically hindered amines (both α and β branching, viz. NH 2 Me-NMe 3 and NH 2 Me-NH 2 Bu t ) and by aniline have been determined in aqueous solution with I = 0.1 mol dm Ϫ3 (NaClO 4 ) at 25 ЊC by UV/VIS spectrophotometry. Comparison with published data on the rates of Fe᎐N bond fission and their further correlation with the energetics of protonation of the free amines shows that the observed variation in log K for aliphatic amines reflects 'solvation' as well as more typically steric effects. Aniline differs from the aliphatic amines both in its smaller crystal-field splitting (shared by other aromatic amines) and a low value of log K comparable to that of NMe 3 .

Optoelectronic Switches Based on Wide Band Gap Semiconductors

“…The redox potentials of thioether complexes usually fall within the 240-405 mV range, and the DMSO complex shows a reversible one-electron reduction at +559 mV vs Ag/AgCl, while the parent ammine complex shows a oneelectron reversible wave at +119 mV (Figure 1). All studied compounds show relatively strong metal-centered (MC) transitions 33,54,57 within 350-400 nm (Figure 2a). In contrary to aromatic amine complexes, the [Fe II (CN) 5 SR 2 ] 3species do not exhibit any metal-to-ligand charge transfer MLCT transitions within 300-1100 nm.…”