• Home
  • Search Results
  • Synthesis of water-soluble silicon-porphyrin: protolytic behaviour of axially coordinated hydroxy groups.

Synthesis of water-soluble silicon-porphyrin: protolytic behaviour of axially coordinated hydroxy groups.

Dalton transactions (Cambridge, England : 2003) (2015-11-04)
Sebastian Nybin Remello, Fazalurahman Kuttassery, Takehiro Hirano, Yu Nabetani, Daisuke Yamamoto, Satomi Onuki, Hiroshi Tachibana, Haruo Inoue
ABSTRACT

A new water-soluble silicon(IV)-tetra(4-carboxyphenyl)porphyrin (SiTCPP) with silicon(iv), the second most abundant element on Earth, in the center of porphyrin was synthesized. Fundamental properties including protolytic behaviour of axially coordinating hydroxy groups, and electrochemical behaviour were characterized. The properties were compared with those of silicon(IV)-tetra(2,4,6-trimethylphenyl)porphyrin (SiTMP) and silicon(IV)-tetra(4-trifluoromethylphenyl)porphyrin (SiTFMPP) and discussed in respect to the electron donating/withdrawing effect of the substituents. Two axially coordinating hydroxy groups of SiTCPP exhibit a four-step protolytic behaviour under the acidic conditions along with a single step protolysis of peripheral carboxyl groups. Though SiTCPP and SiTFMPP did not show any reactivity in the photochemical oxygenation of a substrate with K2PtCl6 as a sacrificial electron acceptor, the first oxidation wave in the electrochemical process of SiTCPP and SiTFMPP showed catalytic behaviour in aqueous acetonitrile solution at any pH condition, in contrast to SiTMP which has only a reversible oxidation wave under neutral and weakly acidic conditions. The criteria for the electrochemical oxidative activation of water and the photooxygenation of the substrate were obtained. The higher oxidation wave of Si-porphyrins than ∼0.86 volt vs. SHE is required for the electrochemical oxidation of water, while suitable protecting groups such as a methyl substituent is a requisite for the photochemical oxygenation with K2PtCl6 as a sacrificial electron acceptor.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1,2-Dimethoxyethane, ReagentPlus®, ≥99%, inhibitor-free
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide, 97%
Sigma-Aldrich
1,2-Dimethoxyethane, anhydrous, 99.5%, inhibitor-free
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 0.5 M in toluene
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 0.5 M in 2-methyltetrahydrofuran
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1.5 M in THF
Sigma-Aldrich
Cyclohexene, inhibitor-free, ReagentPlus®, 99%
Sigma-Aldrich
Cyclohexene, contains 100 ppm BHT as inhibitor, ≥99.0%
Sigma-Aldrich
Trichlorosilane, 99%
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1.0 M in THF
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1 M in toluene
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1.0 M in hexanes
Sigma-Aldrich
Lithium bis(trimethylsilyl)amide solution, 1 M in tert-butyl methyl ether