Upside Down! Crystallographic and Spectroscopic Characterization of an [Fe^IV(O_syn)(TMC)]²⁺ Complex

Fe^II(TMC)­(OTf)₂ reacts with 2-^tBuSO₂–C₆H₄IO to afford an oxoiron­(IV) product, <b>2</b>, distinct from the previously reported [Fe^IV(O_anti)­(TMC)­(NCMe)]²⁺. In MeCN, <b>2</b> has a blue-shifted near-IR band, a higher ν­(FeO), a larger Mössbauer quadrupole splitting, and quite a distinct ¹H NMR spectrum. Structural analysis of crystals grown from CH₂Cl₂ reveals a complex with the formulation of [Fe^IV(O_syn)­(TMC)­(OTf)]­(OTf) and the shortest Fe^IVO bond [1.625(4) Å] found to date

Flexible BODIPY Platform That Offers an Unexpected Regioselective Heterocyclization Reaction toward Preparation of 2‑Pyridone[<i>a</i>]‑Fused BODIPYs

We have explored the synthetic routes for regioselective formation of 2-pyridone­[a]- and 2-pyridone­[b]-fused BODIPYs using 1,3,5,7-tetramethyl-2,6-dicarbethoxy-BODIPY as the universal starting platform. While heterocyclization of the 3-(dimethyl­aminovinyl)-BODIPY and 3,5-bis­(dimethyl­amino­vinyl)-BODIPY results in the formation of mono-2-pyridone- and bis-2-pyridone­[b]-fused BODIPYs, respectively, similar heterocyclization of the 1,3-bis­(dimethylaminovinyl)-BODIPY leads to the regioselective formation of the 2-pyridone­[a]-fused BODIPY core, which is the first example of heterocycle­[a]-fused BODIPYs. The regioselective formation of the 2-pyridone­[a]-fused BODIPY was further confirmed by X-ray crystallography and explained on the basis of the DFT and TDDFT calculations that are suggestive of the energy-favorable out-of-plane rotation of the dimethylaminovinyl group located at first position, which accelerates the reaction with n-butylamine. Trends in the UV–vis and fluorescence spectra of the BODIPYs 1–17 were discussed on the basis of DFT and TDDFT calculations

Flexible BODIPY Platform That Offers an Unexpected Regioselective Heterocyclization Reaction toward Preparation of 2‑Pyridone[<i>a</i>]‑Fused BODIPYs

We have explored the synthetic routes for regioselective formation of 2-pyridone­[a]- and 2-pyridone­[b]-fused BODIPYs using 1,3,5,7-tetramethyl-2,6-dicarbethoxy-BODIPY as the universal starting platform. While heterocyclization of the 3-(dimethyl­aminovinyl)-BODIPY and 3,5-bis­(dimethyl­amino­vinyl)-BODIPY results in the formation of mono-2-pyridone- and bis-2-pyridone­[b]-fused BODIPYs, respectively, similar heterocyclization of the 1,3-bis­(dimethylaminovinyl)-BODIPY leads to the regioselective formation of the 2-pyridone­[a]-fused BODIPY core, which is the first example of heterocycle­[a]-fused BODIPYs. The regioselective formation of the 2-pyridone­[a]-fused BODIPY was further confirmed by X-ray crystallography and explained on the basis of the DFT and TDDFT calculations that are suggestive of the energy-favorable out-of-plane rotation of the dimethylaminovinyl group located at first position, which accelerates the reaction with n-butylamine. Trends in the UV–vis and fluorescence spectra of the BODIPYs 1–17 were discussed on the basis of DFT and TDDFT calculations

Long-Range Electronic Communication in Free-Base <i>meso</i>-Poly(Ferrocenyl)-Containing Porphyrins

H2FcPh3P [FcPh3P = 5-ferrocenyl-10,15,20-triphenyl porphyrin(2-)], cis-H2Fc2Ph2P [cis-Fc2Ph2P = 5,10-bisferrocenyl-15,20-diphenyl porphyrin(2-)], trans-H2Fc2Ph2P [trans-Fc2Ph2P = 5,15-bisferrocenyl-10,20-diphenyl porphyrin(2-)], and H2Fc3PhP [Fc3PhP = 5,10,15-trisferrocenyl-20-phenyl porphyrin(2-)] along with H2TPP [TPP = 5,10,15,20-tetraphenylporphyrin] and H2TFcP [TFcP = 5,10,15,20-tetraferrocenyl porphyrin(2-)] were isolated from the direct cross-condensation reaction between pyrrole, benzaldehyde, and ferrocene carboxaldehyde or from the reaction between ferrocenyl-2,2′-dipyrromethane and benzaldehyde, suggesting a scrambling reaction mechanism for the last approach. All compounds were characterized by UV−vis, MCD, and NMR spectroscopy; APCI MS and MS/MS methods; as well as high-resolution ESI MS spectrometry. The conformational flexibility of ferrocene substituents in all compounds was confirmed using variable-temperature NMR and computational methods. DFT calculations were employed to understand the degree of nonplanarity of the porphyrin core as well as the electronic structure of ferrocene-containing porphyrins. In all cases, a set of occupied, predominantly ferrocene-based molecular orbitals was found between the highest occupied and the lowest unoccupied, predominantly porphyrin-based molecular π orbitals. The redox properties of all ferrocene-containing porphyrins were investigated in a CH2Cl2/TFAB [TFAB = tetrabutylammonium tetrakis(perfluorophenyl)borate] system using cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry methods. In all cases, oxidations of individual ferrocene substituent(s) along with porphyrin core oxidation(s) and reductions have been observed. Mixed-valence [cis-H2Fc2Ph2P]+, [trans-H2Fc2Ph2P]+, [H2Fc3PhP]+, and [H2Fc3PhP]2+ complexes were formed in situ under spectroelectrochemical and chemical oxidation conditions and were characterized using UV−vis and MCD approaches. Analysis of intervalence charge-transfer bands observed in the NIR region for all mixed-valence complexes suggests electron localization and thus class II behavior in the Robin−Day classification

Long-Range Electronic Communication in Free-Base <i>meso</i>-Poly(Ferrocenyl)-Containing Porphyrins

H2FcPh3P [FcPh3P = 5-ferrocenyl-10,15,20-triphenyl porphyrin(2-)], cis-H2Fc2Ph2P [cis-Fc2Ph2P = 5,10-bisferrocenyl-15,20-diphenyl porphyrin(2-)], trans-H2Fc2Ph2P [trans-Fc2Ph2P = 5,15-bisferrocenyl-10,20-diphenyl porphyrin(2-)], and H2Fc3PhP [Fc3PhP = 5,10,15-trisferrocenyl-20-phenyl porphyrin(2-)] along with H2TPP [TPP = 5,10,15,20-tetraphenylporphyrin] and H2TFcP [TFcP = 5,10,15,20-tetraferrocenyl porphyrin(2-)] were isolated from the direct cross-condensation reaction between pyrrole, benzaldehyde, and ferrocene carboxaldehyde or from the reaction between ferrocenyl-2,2′-dipyrromethane and benzaldehyde, suggesting a scrambling reaction mechanism for the last approach. All compounds were characterized by UV−vis, MCD, and NMR spectroscopy; APCI MS and MS/MS methods; as well as high-resolution ESI MS spectrometry. The conformational flexibility of ferrocene substituents in all compounds was confirmed using variable-temperature NMR and computational methods. DFT calculations were employed to understand the degree of nonplanarity of the porphyrin core as well as the electronic structure of ferrocene-containing porphyrins. In all cases, a set of occupied, predominantly ferrocene-based molecular orbitals was found between the highest occupied and the lowest unoccupied, predominantly porphyrin-based molecular π orbitals. The redox properties of all ferrocene-containing porphyrins were investigated in a CH2Cl2/TFAB [TFAB = tetrabutylammonium tetrakis(perfluorophenyl)borate] system using cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry methods. In all cases, oxidations of individual ferrocene substituent(s) along with porphyrin core oxidation(s) and reductions have been observed. Mixed-valence [cis-H2Fc2Ph2P]+, [trans-H2Fc2Ph2P]+, [H2Fc3PhP]+, and [H2Fc3PhP]2+ complexes were formed in situ under spectroelectrochemical and chemical oxidation conditions and were characterized using UV−vis and MCD approaches. Analysis of intervalence charge-transfer bands observed in the NIR region for all mixed-valence complexes suggests electron localization and thus class II behavior in the Robin−Day classification

A More Reactive Trigonal-Bipyramidal High-Spin Oxoiron(IV) Complex with a cis-Labile Site

The trigonal-bipyramidal high-spin (S = 2) oxoiron(IV) complex [FeIV(O)(TMG2dien)(CH3CN)]2+ (7) was synthesized and spectroscopically characterized. Substitution of the CH3CN ligand by anions, demonstrated here for X = N3– and Cl–, yielded additional S = 2 oxoiron(IV) complexes of general formulation [FeIV(O)(TMG2dien)(X)]+ (7-X). The reduced steric bulk of 7 relative to the published S = 2 complex [FeIV(O)(TMG3tren)]2+ (2) was reflected by enhanced rates of intermolecular substrate oxidation

A More Reactive Trigonal-Bipyramidal High-Spin Oxoiron(IV) Complex with a cis-Labile Site

The trigonal-bipyramidal high-spin (S = 2) oxoiron(IV) complex [FeIV(O)(TMG2dien)(CH3CN)]2+ (7) was synthesized and spectroscopically characterized. Substitution of the CH3CN ligand by anions, demonstrated here for X = N3– and Cl–, yielded additional S = 2 oxoiron(IV) complexes of general formulation [FeIV(O)(TMG2dien)(X)]+ (7-X). The reduced steric bulk of 7 relative to the published S = 2 complex [FeIV(O)(TMG3tren)]2+ (2) was reflected by enhanced rates of intermolecular substrate oxidation

A More Reactive Trigonal-Bipyramidal High-Spin Oxoiron(IV) Complex with a cis-Labile Site

The trigonal-bipyramidal high-spin (S = 2) oxoiron(IV) complex [FeIV(O)(TMG2dien)(CH3CN)]2+ (7) was synthesized and spectroscopically characterized. Substitution of the CH3CN ligand by anions, demonstrated here for X = N3– and Cl–, yielded additional S = 2 oxoiron(IV) complexes of general formulation [FeIV(O)(TMG2dien)(X)]+ (7-X). The reduced steric bulk of 7 relative to the published S = 2 complex [FeIV(O)(TMG3tren)]2+ (2) was reflected by enhanced rates of intermolecular substrate oxidation