The complexes [Fe^III(HMC)(C₂DMA)₂]CF₃SO₃ ([2]OTf) and [Fe^III(HMTI)(C₂Y)₂]CF₃SO₃ ([3a–c]OTf) have been prepared and thoroughly characterized (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; HMTI = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene; Y = Fc (ferrocenyl, [3a]OTf), 4-(N,N-dimethyl)anilino (DMA, [3b]OTf), or 4-(N,N-bis(4-methoxyphenyl)anilino (TPA, [3c]OTf); OTf^– = CF₃SO₃^–)). Vibrational and electronic absorption spectroelectrochemical analyses following one-electron oxidation of the ethynyl substituent Y revealed evidence of strong coupling in the resultant mixed valent species for all HMTI-based complexes. However, the analogous mixed valent ion based on [2]OTf appeared to be more localized. Thus, the tetra-imino macrocycle HMTI has enabled significant valence delocalization along the −C₂–Fe^III–C₂– bridge. Electron paramagnetic resonance and Mössbauer spectroscopic studies of [3b]OTf reveal that the π-acidity of HMTI lowers the energy of the Fe^III dπ orbitals compared to the purely σ-donating HMC. This observation provides a basis for the interpretation of the macrocycle-dependent valence (de)localization.

中文翻译：

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通过环不饱和度实现铁(III)大环配合物的价态离域

配合物 [Fe ^III (HMC)(C ₂ DMA) ₂ ]CF ₃ SO ₃ ([ 2 ]OTf) 和 [Fe ^III (HMTI)(C ₂ Y) ₂ ]CF ₃ SO ₃ ([ 3a – c ]OTf) ）已制备并彻底表征（HMC = 5,5,7,12,12,14-六甲基-1,4,8,11-四氮杂环十四烷；HMTI = 5,5,7,12,12,14-六甲基- 1,4,8,11-四氮杂环十四-1,3,8,10-四烯；Y = Fc（二茂铁基，[ 3a ]OTf），4-（N，N-二甲基）苯胺基（DMA，[ 3b ]OTf） , 或 4-( N , N -双(4-甲氧基苯基)苯胺基 (TPA, [ 3c ]OTf); OTf ^– = CF ₃ SO ₃ ^– ))。乙炔基取代基 Y 的单电子氧化后的振动和电子吸收光谱电化学分析揭示了所有基于 HMTI 的复合物所得混合价物质中强耦合的证据。然而，基于[ 2 ]OTf的类似混合价离子似乎更局域化。因此，四亚氨基大环HMTI能够沿着-C ₂ -Fe ^III -C ₂ -桥实现显着的价态离域。[ 3b ]OTf的电子顺磁共振和穆斯堡尔谱研究表明，与纯 σ 供体 HMC 相比， HMTI 的 π 酸性降低了 Fe ^III dπ 轨道的能量。这一观察结果为解释大环依赖性价（去）定位提供了基础。