: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

The main synthetic approaches for the preparation of porphyrazines are outlined. In addition, some structural and spectroscopic properties, especially the UV-vis absorption profiles emanating from their peripheral functionalization, the modification of the tetraazaporphyrin skeleton or the arrangement of macrocycles in a supramolecular manner, are discussed. Cyclotetramerization of appropriate dinitrile derivatives or modification of peripheral substituents on porphyrazines constitute the main synthetic routes. Moreover, the use of special templates, as well as different intermediates or nonpyrrolic precursors, are tools for the attainment of azaporphyrin analogues of distinct nature and unusual characteristics.

The chemistry of porphyrazines: an overview

Mechanisms of Inorganic Reactions. A Study of Metal Complexes in Solution.

Magnesium(II), zinc(II), and metal-free phthalocyanines (Pcs) and azaphthalocyanines (AzaPcs) containing alkylsulfanyl, aryloxy, and dialkylamino peripheral substituents have been synthesized. The complexation of magnesium(II) by metal-free Pcs and AzaPcs has been studied in detail to determine the optimal reaction conditions necessary to ensure a complete conversion. Photophysical and photochemical measurements in tetrahydrofuran showed that magnesium(II) AzaPcs with aryloxy and alkylsulfanyl substituents have excellent fluorescent properties (Φ(F) up to 0.73) and that the corresponding zinc(II) Pcs are efficient singlet oxygen producers (Φ(Δ) up to 0.68). The presence of dialkylamino substituents causes intramolecular charge transfer within the molecule that competes with fluorescence and singlet oxygen formation. Alkylsulfanyl MgAzaPc and ZnAzaPc were the most photostable compounds among the series of studied derivatives. In addition, high molar absorption coefficients (e ∼ 300,000 M(-1) cm(-1)), absorption (λ(max) ∼ 650 nm), and emission (λ(em) ∼ 660 nm, high Φ(F)) in the red region suggest that these molecules are potential fluorescent probes that are superior to the commercial red cyanine dye Cy5. MgAzaPc, when incorporated into lipidic bilayers of liposomes, maintains excellent fluorescence properties (Φ(F) = 0.64). Water-soluble MgAzaPc with quaternary ammonium peripheral substituents retained a high fluorescence quantum yield even in water (Φ(F) = 0.25). The described properties show that magnesium(II) AzaPcs are excellent red-emitting fluorophores with potential applications as fluorescent probes in sensing or in vitro imaging applications.

Magnesium azaphthalocyanines: an emerging family of excellent red-emitting fluorophores.

The bromination of [5-(4-nitrophenyl)-10,15,20-triphenylporphyrinato]cobalt(II) and [5,10,15-tris-(4-nitrophenyl)-20-phenylporphyrinato]cobalt(II) with N-bromosuccinimide in a mixture of chloroform and dimethylformamide gave [2,3,7,8,12,13,17,18-octabromo-5-(4-nitrophenyl)-10,15,20-triphenylporphyrinato]-cobalt(II) and [2,3,7,8,12,13,17,18-octabromo-5,10,15-tris(4-nitrophenyl)-20-phenylporphyrinato]cobalt(II). Treatment of the cobalt complexes with a mixture of perchloric and sulfuric acids afforded the corresponding metal-free porphyrins. Electron absorption, 1H NMR, and mass spectra of the synthesized compounds were studied, and acidity and basicity constants of the porphyrin ligands in acetonitrile were determined.

Synthesis and Acid–Base Properties of β-Octabromo-Substituted Unsymmetrical Nitrophenylporphyrins

Complexes Co2+ and Co3+ with octaphenyltetraazaporphyrin, octa(4-bromphenyl)tetraazaporphyrin and octa(4-nitrophenyl)tetraazaporphyrin were obtained and identified. The influence of the composition of reaction medium on the oxidation processes of the complexes Co2+ → Co3+ in DMF was revealed and the optimum conditions of formation of the corresponding compounds were determined.

Synthesis and spectral properties of the Co2+ and Co3+ complexes with octaaryltetraazaporphyrins

The metal-exchange reaction of Mg(II)-octaphenyltetraazaporphyrin with CoCl2 leading to formation of Co(II)-octaphenyltetraazaporphyrin was studied by the method of UV-vis spectroscopy. The kinetic parameters of the metal-exchange reaction were determined.

Metal-exchange reaction of Mg-octaphenyltetraazaporphyrin with Co(II)

Исследована реакция переметаллирования 5,10,15,20-тетрафенилтетрабензопорфирината Cd(II) с хлоридами Ni(II), Pd(II) и Pt(II) в диметилформамиде и феноле. Cинтезированы соответствующие порфиринаты Ni(II), Pd(II) и Pt(II). При обработке 5,10,15,20-тетрафенилтетрабензопорфирината Pt(II) бромом в хлороформе получен порфиринат Pt(IV)(Br)2. Синтезированные соединения идентифицированы методами электронной абсорбционной, 1Н ЯМР спектроскопии, масс-спектрометрии и элементного анализа.

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Tetraphenyltetrabenzoporphyrinates of Ni(II), Pd(II), Pt(II) and Pt(IV)

The selectivity and degree of bromination of pyrrole rings in porphyrazine strongly depends on the brominating agent and solvent nature. The reaction of porphyrazine magnesium complex with molecular bromine and N-bromosuccinimide in pyridine gave magnesium complex of dibromotetraazaporphine. Increasing bromine substitution in porphyrazine enhances its acidic properties.

Natalya V. Chizhova

Papers

Synthesis and Acid–Base Properties of β-Octabromo-Substituted Unsymmetrical Nitrophenylporphyrins

Synthesis and spectral properties of the Co2+ and Co3+ complexes with octaaryltetraazaporphyrins

Metal-exchange reaction of Mg-octaphenyltetraazaporphyrin with Co(II)

Tetraphenyltetrabenzoporphyrinates of Ni(II), Pd(II), Pt(II) and Pt(IV)

Bromination of Tetraazaporphine and Its β-Substituted Derivatives Using Pyridine as Solvent and Catalyst