The inverted triplesalen ligand H6feldMe has been synthesized from 2,4,6-triformyl-phloroglucinol and a ketimine salen half-unit in a convergent synthesis. NMR, IR, and UV-vis spectroscopy reveal that this ligand is n...The inverted triplesalen ligand H6feldMe has been synthesized from 2,4,6-triformyl-phloroglucinol and a ketimine salen half-unit in a convergent synthesis. NMR, IR, and UV-vis spectroscopy reveal that this ligand is not in the O-protonated tau- tomer but in the N-protonated tautomer with substantial heteroradialene contribution. This ligand and the conventional triple- salen ligand H6talent-au2 have been used to synthesize the trinuclear Fem complexes [（feldMe）（FeCl）3] and [（talent-Bu2）（FeC1）3], respectively. The molecular structures of these complexes were obtained by single-crystal X-ray diffraction. Two trinuclear Fem complexes of [（feldMe）（FeCl）3] dimerize via two Fe-phenolate bonds, whereas due to steric hindrance no dimerization is observed for [（talent-Bu2）（FeC1）3]. The structural data also reveal some heteroradialene contribution in the trinuclear complexes. Whereas UV-vis and MOlSbauer spectroscopy are not suitable to distinguish between the two complexes, FT-IR spectra show characteristic features due to the different substitution patterns of the conventional and the inverted triplesalen ligands. Another handle is provided by electrochemistry. Whereas both complexes exhibit an irreversible oxidation wave （0.94 V vs. Fc＋/Fc for [（feldMe）（FeC1）3] and 0.84 V vs. Fc~/Fc for [（talent-Bu2）（FeC1）3]）, which is assigned to the oxidation of the central backbone, higher potential oxidations are reversible for [（talent-Bu2）（FeC1）3]） but irreversible for [（feldMe）（FeC1）3]. This is attributed to the reversible oxidation of the terminal phenolates in the di-tert-butyl substituted [（talentBu2）（FeCl）3] in contrast to the mono-methyl-substituted phenolates in [（feld^ae）（FeC1）3]. The magnetic properties of [（talen^-Bu2）（FeC1）3] reveal a very small ferromagnetic coupling with significant zero-field splitting of the Feul S = 5/2 ions. In contrast, the dimerization of two trinu- clear complexes in [（feldMe）（FeCl）3] results in antiferromagnetic interactions between the two phenolate-bridged FeIII ions, which mask the intra-trinuclear interactions transmitted by the central phloroglucinol backbone.展开更多
基金supported by the Deutsche Forschungsgemeinschaft(FOR945 ‘Nanomagnets: from Synthesis via Interactions with Surfaces to Function’)the Fonds der Chemischen IndustrieBielefeld University
文摘The inverted triplesalen ligand H6feldMe has been synthesized from 2,4,6-triformyl-phloroglucinol and a ketimine salen half-unit in a convergent synthesis. NMR, IR, and UV-vis spectroscopy reveal that this ligand is not in the O-protonated tau- tomer but in the N-protonated tautomer with substantial heteroradialene contribution. This ligand and the conventional triple- salen ligand H6talent-au2 have been used to synthesize the trinuclear Fem complexes [（feldMe）（FeCl）3] and [（talent-Bu2）（FeC1）3], respectively. The molecular structures of these complexes were obtained by single-crystal X-ray diffraction. Two trinuclear Fem complexes of [（feldMe）（FeCl）3] dimerize via two Fe-phenolate bonds, whereas due to steric hindrance no dimerization is observed for [（talent-Bu2）（FeC1）3]. The structural data also reveal some heteroradialene contribution in the trinuclear complexes. Whereas UV-vis and MOlSbauer spectroscopy are not suitable to distinguish between the two complexes, FT-IR spectra show characteristic features due to the different substitution patterns of the conventional and the inverted triplesalen ligands. Another handle is provided by electrochemistry. Whereas both complexes exhibit an irreversible oxidation wave （0.94 V vs. Fc＋/Fc for [（feldMe）（FeC1）3] and 0.84 V vs. Fc~/Fc for [（talent-Bu2）（FeC1）3]）, which is assigned to the oxidation of the central backbone, higher potential oxidations are reversible for [（talent-Bu2）（FeC1）3]） but irreversible for [（feldMe）（FeC1）3]. This is attributed to the reversible oxidation of the terminal phenolates in the di-tert-butyl substituted [（talentBu2）（FeCl）3] in contrast to the mono-methyl-substituted phenolates in [（feld^ae）（FeC1）3]. The magnetic properties of [（talen^-Bu2）（FeC1）3] reveal a very small ferromagnetic coupling with significant zero-field splitting of the Feul S = 5/2 ions. In contrast, the dimerization of two trinu- clear complexes in [（feldMe）（FeCl）3] results in antiferromagnetic interactions between the two phenolate-bridged FeIII ions, which mask the intra-trinuclear interactions transmitted by the central phloroglucinol backbone.
