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首页> 外文期刊>Chemistry: A European journal >The photochemistry of [Fe ~(III)N _3(cyclam-ac)]PF _6 at 266 nm
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The photochemistry of [Fe ~(III)N _3(cyclam-ac)]PF _6 at 266 nm

机译：[Fe〜（III）N _3（cyclam-ac）] PF _6在266 nm的光化学

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The photochemistry of iron azido complexes is quite challenging and poorly understood. For example, the photochemical decomposition of [Fe ~(III)N _3(cyclam-ac)]PF _6 ([1]PF _6), where cyclam-ac represents the 1,4,8,11-tetraazacyclotetradecane-1-acetate ligand, has been shown to be wavelength-dependent, leading either to the rare high-valent iron(V) nitrido complex [Fe ~VN(cyclam-ac)]PF _6 ([3]PF _6) after cleavage of the azide N _α-N _β bond, or to a photoreduced Fe ~(II) species after Fe-N _(azide) bond homolysis. The mechanistic details of this intriguing reactivity have never been studied in detail. Here, the photochemistry of 1 in acetonitrile solution at room temperature has been investigated using step-scan and rapid-scan time-resolved Fourier transform infrared (FTIR) spectroscopy following a 266 nm, 10 ns pulsed laser excitation. Using carbon monoxide as a quencher for the primary iron-containing photochemical product, it is shown that 266 nm excitation of 1 results exclusively in the cleavage of the Fe-N _(azide) bond, as was suspected from earlier steady-state irradiation studies. In argon-purged solutions of [1]PF _6, the solvent-stabilized complex cation [Fe ~(II)(CH _3CN)(cyclam-ac)] ~+ (2 red) together with the azide radical (N _3.) is formed with a relative yield of 80 %, as evidenced by the appearance of their characteristic vibrational resonances. Strikingly, step-scan experiments with a higher time resolution reveal the formation of azide anions (N _3 ~-) during the first 500 ns after photolysis, with a yield of 20 %. These azide ions can subsequently react thermally with 2 red to form [Fe ~(II)N _3(cyclam-ac)] (1 red) as a secondary product of the photochemical decomposition of 1. Molecular oxygen was further used to quench 1 red and 2 red to form what seems to be the elusive complex [Fe(O _2)(cyclam-ac)] ~+ (6). Time-resolved spectroscopy: Time-resolved rapid-scan and step-scan spectroscopy in the mid-infrared spectral region is used to explore the photochemistry of an iron(III) azido complex, and to generate what seems to be a stable nonheme iron-superoxo complex (see figure).
机译：铁叠氮铁络合物的光化学具有很大的挑战性，并且了解甚少。例如，[Fe〜（III）N _3（cyclam-ac）] PF _6（[1] PF _6）的光化学分解，其中cyclam-ac代表1,4,8,11-四氮杂环十四烷-1-乙酸盐配体，已显示是波长依赖性的，导致叠氮化物N裂解后导致稀有的高价铁（V）氮化物络合物[Fe〜VN（cyclam-ac）] PF _6（[3] PF _6）在Fe-N _（叠氮化物）键均质后，_α-N_β键或光还原Fe〜（II）物种从未详细研究这种有趣的反应机理的细节。在这里，在266 nm，10 ns脉冲激光激发之后，使用步进扫描和快速扫描时间分辨傅里叶变换红外（FTIR）光谱研究了室温下乙腈溶液中1的光化学性质。使用一氧化碳作为主要含铁光化学产物的淬灭剂，表明266 nm激发1仅导致Fe-N _（叠氮化物）键的裂解，这是从早期的稳态辐照研究中怀疑的。在[1] PF _6的氩气吹扫溶液中，溶剂稳定的复合阳离子[Fe〜（II）（CH _3CN）（cyclam-ac）] +（2红）与叠氮基（N _3。）由它们的特征振动共振的出现证明，其相对产率为80％。令人惊讶的是，具有更高时间分辨率的步进扫描实验揭示了在光解后的前500 ns内形成叠氮化物阴离子（N _3〜-），产率为20％。这些叠氮化物离子可随后与2个红色发生热反应，形成[Fe〜（II）N _3（cyclam-ac）]（1个红色），作为1光化学分解的副产物。进一步使用分子氧淬灭1个红色和2红色形成似乎难以捉摸的复合物[Fe（O _2）（cyclam-ac）]〜+（6）。时间分辨光谱：中红外光谱区的时间分辨快速扫描和步进扫描光谱用于探索叠氮铁（III）络合物的光化学，并产生看似稳定的非血红素铁。超氧复合物（见图）。

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