A persistent manganese carbonyl radical with infrared absorption and fluorescence modality

Stable manganese carbonyl radicals as a rapid colorimetric thiol and hydrazine sensor

“…[1][2][3] Previously a class of stable cyclopentadienyl manganese dicarbonyl radicals, CpMn(CO) 2 X (X is -NHR (R ¼ aryl) or -SR (R ¼ aryl and alkyl)) has been synthesized. 4,5 Notably, the colours of the radical complexes are highly dependent on the type of ligand. Radical complexes with alkylthio ligands are red while a deep blue-green colouration is observed with those carrying anilinyl ligands.…”

“…In this work, we have prepared two stable blue CpMn(CO) 2 X radical complexes [where X ¼ -NHPh (anilinyl) (1) and -NHC 6 H 2 (OMe) 3 (3,4,5-trimethoxyanilinyl) (2)] as colorimetric thiol and hydrazine sensors. We have found that these radical complexes change colour rapidly upon reaction with thiol and hydrazine hence enabling their monitoring and quantitation to be carried out using a simple UV-visible absorption spectrometer.…”

“…This absorption has previously been described as a ligand-to-metal charge transfer (LMCT) transition from the anilinyl ring onto the Mn center. 4 The addition of an aliphatic thiol rapidly turns the solution dark red and produces a new absorption peak at 510 nm due to the formation of the CpMn(CO) 2 (-SR) radical complex. 5 As the reaction progresses, an isosbestic point (z555 nm) is observed indicating the clean conversion of 1 to the red complex.…”

“…Although related radical complexes of 1 and 2 have been prepared and structurally characterised, their reactivities towards organic molecules have not been investigated before. 4,5 Using the reaction of 1 with 1-octanethiol as an example (Scheme 2), we believe that the rst step of the reaction is a hydrogen atom (of the S-H bond) abstraction by 1. This regenerates the N-H bond of the aniline ligand which is subsequently displaced by the incoming thio radical.…”