Hisanobu Ogoshi

Infrared Spectra and Normal Coordinate Analysis of Metalloporphins

The infrared spectra of porphin and its metal complexes with 64Zn, 68Zn, Cu, and Ni have been obtained from 4000 to 100 cm−1. Normal coordinate analyses have been carried out on the D4h model of the porphin complexes with 64Zn, 68Zn, Cu, and Ni. Only the eighteen in‐plane vibrations have been calculated. The results indicate that the bands between 1700 and 950 cm−1 are due to CC stretching, CN stretching, CH in‐plane bending, CCN in‐plane bending or coupled vibrations between these modes, and that the largest contribution of the metal‐nitrogen stretching coordinate is found in the vibrations at ≈ 203, 246, and 295 cm−1 of the Zn, Cu, and Ni complexes, respectively. The Urey‐Bradley force constants for the corresponding metal‐nitrogen stretching modes are estimated to be 0.553, 0.662, and 0.760 mdyn/A, respectively.

Catalytic reactions of metalloporphyrins.: II. Activation and catalytic aldol condensation of ketone with rhodium(III)-porphyrin perchlorate under neutral and mild conditions☆

Abstract Acetone and methyl ethyl kektone undergo facile and direct metalation at the methyl groups by a cationic (octaethylporphyrinato) rhodium (III) complex with a non-coordinating perchlorate counteranion, (OEP)Rh III (ClO 4 ), under mild conditions. Acetylacetone and ethyl acetoacetate are similarly metalated at the internal methylene groups. The metalation of acetone is firs-order with respect to both rhodium complex and ketone, and involves the (OEP)Rh III (ClO 4 )-assisted, rate-determining enolization of the ketone. The resulting 2-oxopropyl-rhodium derivative undergoes facile cleavage of the CRh bond with electrophiles such as H + and Br 2 . When cyclohexanone is used as substrate, on the other hand, (OEP)Rh III (ClO 4 ) catalyzes the aldol condensation of the ketone effectively, where the intermediate cyclohexanone enolate reacts with the ketone or other carbonyl compound present and regenerates the Rh III complex. An essential aspect of the present reaction is the remarkable ability of (OEP)Rh III (ClO 4 ) to promote enolization of simple ketones by activation with charge-separated [(OEP)Rh III + (a Lewis acid) under mild and neutral conditions. The second-order rate constant of (OEP)Rh III (ClO 4 )-assisted enolization of acetone at 30°C ( k 2 = 2.6 × 10 −4 M −1 sec −1 ) is 10 7 times as large as that of its spontaneous enolization in water, where water is both acid and bse.

Intramolecular hydrogen bond in enol form of 3-substituted-2,4-pentanedione

Abstract The 3-substituent effect on the enolic ring of 2,4-pentanedione has been investigated. A linear relationship between the chemical shifts of the enolic proton and the chelated carbonyl stretching vibrations has been found for the various highly enolized 3-substituted-2,4-pentanediones. The stronger electron-withdrawing resonance effect of the substituent at 3-position results in the lower magnetic field shift of the enolic proton and the lower frequency shift of the chelated carbonyl stretching. Semi-empirical Huckel calculations have been performed to enable discussion of the electronic effect of the substituents.

Chiral recognition and chiral sensing using zinc porphyrin dimers

Abstract The chiral zinc porphyrin dimer linked by the ( S )-NMe 2 or ( R )-2,2′-dimethoxy-1,1′-binaphthyl tightly binds diamines via a zinc–nitrogen coordinated ditopic interaction. In particular, the zinc porphyrin displays excellent enantioselectivity towards Lys. The D / L selectivity is determined to be 11–12 for the lysine derivatives. The achiral zinc porphyrin dimers linked by biphenyl unit exhibit a significantly induced CD in the Soret region in the presence of chiral diamines such as lysine amides and cystine diesters, indicating that the chirality of the amino acid derivatives can be monitored upon the complexation with the achiral zinc porphyrin dimer. These results conclude that the zinc porphyrin dimers linked by rigid spacers may be good receptors to discriminate two enantiomers or monitor the absolute configuration of a diamine.

Molecular recognition of α,ω-diamines by metalloporphyrin dimer

Abstract Porphyrin dimer linked with chiral binaphthyl derivative was prepared as a ditopic coreceptor for a series of diamines. Its zinc complex shows the good affinity for α,ω-diamines H 2 N(CH 2 ) n NH 2 (n = 6, 8, 10, 12; K a = 10 5 – 10 6 M −1 in CH 2 Cl 2 at 15 °C). These complexes gave the significant bisignate CD spectra due to the exciton coupling between two zinc porphyrins and its intensity depends on the length of diamine. The CD spectrum in the complex reflects angle and flexibility of the chiral twist between two zinc porphyrin units.

Fluoropyrroles and tetrafluoroporphyrins

Abstract Photolysis of pyrrole-β-diazonium tetrafluoroborates gave β-fluoropyrroles. These were further converted to 1,3,5,7-tetrafluoroporphyrins, the first example of ring-fluorinated porphyrin derivatives.

Syntheses and reactions of iridium complexes of octaethylporphyrin

Abstract New iridium porphyrin complexes (I-V) have been prepared by the reactions of octaethylporphyrin (OEPH 2 ) or N-methyloctaethylporphyrin (N-Me·OEPH) with μ-dichloro-hexacarbonyl-diiridium(I) ([Ir(CO) 3 Cl] 2 ) or μ-dichlorobis[π-cyclooctadiene-(1,5)]-diiridium(I) ([Ir(COD)Cl] 2 ). Hydrido- and organo-iridium(III)OEP complexes (VI-XII) have been synthesized by various methods and characterized on the basis of spectroscopic measurements.

Catalytic Reactions of Metalloporphyrins. Part 1. Catalytic Modification of Borane Reduction of Ketone with Rhodium(II) Porphyrin as Catalyst.

(Octaethylporphyrinato)rhodium(III) Chloride exhibits efficient catalysis in the aerobic reduction of ketones (I) with NaBH4 to give the alcohols (II).

Electron deficient porphyrins. 1. Tetrakis(trifluoromethyl)porphyrin and its metal complexes

Abstract 1,3,5,7-Tetrakis(trifluoromethyl)-2,4,6,8-tetraethylporphyrin and its metal (Cu(II), Zn(II), and Co(II) complexes have been prepared.

Resonance Raman spectra of 15N enriched metallooctaethylorphyrins. Characterization of the oxidation state marker bands of hemoproteins

Abstract Resonance Raman spectra of 15 N enriched metallooctaethylporphyrins [M(OEP) − 15 N 4 ] [M = Ni 2+ , Fe 3+ (high spin), and Fe 3+ (low spin)] were observed. Polarized Raman lines corresponding to the oxidation state marker band of hemoproteins were observed at 1377 (Ni), 1369 (Fe high spin) and 1372 −1 (Fe low spin) which were shifted to lower frequency from those of the 14 N compounds by 6, 5, and 6 cm −1 , respectively. The vibrational mode for this band was shown to include an appreciable contribution of the C α N symmetric stretching vibration and to be associated with ca. 0.01 A of in-phase displacement of the four pyrrole nitrogens toward the metal ion.