Optically active dithiocarbamato Fe(II)–NO complex and its application for the NO detection

The presence of NO can be detected by circular dichroism (CD) spectroscopy, which is based on an asymmetric transformation in tris(dithiocarbamato)iron(II) complex. The complex [Fe(S-proOHdtc)3]4− {S-proOHdtc2− = 1-dithiocarboxyl-4-hydroxy-S-proline(2−)} in methanol shows a large negative CD peak at 600 nm. It suggests that, in the epimerization equilibrium between Δ(S,S,S) and Λ(S,S,S), the Δ(S,S,S) complex is predominant species in methanol. The reaction of NO with Δ(S,S,S)-[Fe(S-proOHdtc)3]4− in methanol shows a decrease of the negative CD peak at 600 nm. This phenomenon of the CD peak decrease shows the NO presence and it can be used for the detection of NO.

CD spectra of K4[Fe(S-proOHdtc)3] in methanol solution were changed on NO gas bubbling at 50 mL/min for 10 min. The large negative CD signal at 600 nm is attributed to the first order asymmetric transformation between Δ(S,S,S) and Λ(S,S,S) for the tris(S-proOHdtc) ferrate(II) complex. The peak at 600 nm is mainly Δ(S,S,S) species. When NO gas is bubbled into a solution of K4[Fe(S-proOHdtc)3] in methanol at 50 mL/min from an NO cylinder, a rapid decrease of the CD peak at 600 nm occurred after 3 min for 4, 4.5, 5, 6 and 10 min of bubbling time. The decrease of the CD peak on NO gas bubbling, reflects the decomposition of the [Fe(S-proOHdtc)3]4− to [Fe(NO)(S-proOHdtc)2]2−. This phenomenon of the CD peak decrease corresponds to NO presence and can be applied for the NO detection in methanol.Figure optionsDownload as PowerPoint slideHighlights
► K4[Fe(S-proOHdtc)3] in methanol shows a relatively large CD peak at 600 nm.
► The large and negative peak observed at 600 nm was mainly Δ(S,S,S) species.
► The CD signal decrease with NO means Δ(S,S,S)-[Fe(S-proOHdtc)3]4− decomposed.
► The ESR signal change with NO until 5 min is similar to the CD peak change.
► Optically active K4[Fe(S-proOHdtc)3] complex can be useful in the detection of NO.