Exposure of [MnIII6CrIII]3+ single-molecule magnets to soft X-rays: The effect of the counterions on radiation stability

Abstract

X-ray absorption spectroscopy stud ies of the [MnIllGCrlll)1' single-mo lecu le magnet deposited as a microcrystalline layer on go ld substrates are presented. The oxidation state of the manganese cente rs cha nges from Mnlll to Mn" due to irradiatio n with soft X-rays. The influence of the charge-neutralizing anions on the stability of [MnIll 6Crlll)1' aga inst soft X-ray exposure is investigated for the different a nions tetraphenylborate (BPh 4-), lactate (C3HS0 3-) and perchlorate «(10 4-), The exposure d e pendence of the radiation-induced reduction process is compared for [MnIllGCrlll)1' with the three different anions.

Probing the magnetic moments of [MnIII6CrIII]3+ single-molecule magnets—A cross comparison of XMCD and spin-resolved electron spectroscopy

“…The spectral shape of the Mn L 3,2 absorption edge is very sensitive to changes in the oxidation state of the Mn ions, thereby making XAS a useful tool to monitor the sample condition. Reference data obtained from bulk Mn II and Mn III oxides provide a means to determine the Mn II /Mn III ratio present in the [Mn III 6 Cr III ] 3+ sample [32]. The intact [Mn III 6 Cr III ] 3+ molecule contains solely Mn III , therefore this ratio serves as an indicator of changes to the molecule condition due to preparation or radiation exposure.…”

“…The electron spectrometer as well as the Mott polarimeter has been used successfully before [33,51,53,64,65] and has been described in more detail elsewhere, see [53,65]. The UHV setup was completed by an electrically isolated sample stage in order to perform total-electron-yield mode XAS measurements, a sample transfer and preparation system providing UHV storage for up to 6 samples and a load-lock with a pumpdown time of less than 1 h, allowing frequent sample changes made necessary by the limited sample lifetime under soft X-ray exposure [32].…”

“…Methanolic solutions of the SMM with a concentration of 9·10 −5 mol/l were prepared. Based on the results of an earlier XAS study on the radiation sensitivity of the investigated SMM [32], the most stable [Mn III 6 Cr III ](ClO 4 ) 3 SMM with perchlorate anions was chosen for the spin-resolved electron spectroscopy measurements.…”

“…The [Mn III 6 Cr III ] 3+ SMM investigated here were synthesized according to the procedure described in earlier works [26,32]. Methanolic solutions of the SMM with a concentration of 9·10 −5 mol/l were prepared.…”

“…For detailed information concerning the specifications of both beamlines see [59][60][61]. An off-focus sample position was chosen to reduce the synchrotron radiation flux at the sample to 10 11 photons/s/100 mA with respect to the radiation sensitivity of the [Mn III 6 Cr III ] 3+ SMM [32].…”