: 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 metal-exchange reaction between Cd(II) octa-(4-bromophenyl)porphyrinate and cobalt chloride in DMF and DMSO was studied by UV-Vis spectroscopy. The kinetic parameters of the metal-exchange reaction were calculated. A possible mechanism of the reaction was established. An effect of the nature of the solvent and metal salt on the reaction rate was revealed. Comparative analysis of the apparent rate constants of the metal exchange reaction between CoCl2 and Cd(II) octa-(4-bromophenyl)porphyrinates and Cd(II) octa-(4-bromophenyl)tetraazaporphyrinate in DMF and DMSO was performed.

Some Aspects of Metal Exchange Between Cadmium Porhyrinate Octa-(4-bromophenyl)porphyrin and Cobalt Chloride in Organic Solvents

The metal-exchange reaction of cadmium 5,10,15,20-tetraphenylporphyrinate (CdTPP) and cadmium 2-bromo-5,10,15,20-tetraphenylporphyrinate (CdTPPBr) with copper acetate (Cu(OAc)(2)) in dimethylformamide was studied spectrophotometrically. The kinetic parameters of the metal-exchange reaction were determined. A possible stoichiometric reaction mechanism was proposed.

Metal-exchange reaction between cadmium tetraphenylporphyrinates and copper(II) in dimethylformamide

Metal exchange of cadmium 5,10,15,20-tetraphenylporphyrinate (CdTPP) and cadmium 2-bromo-5,10,15,20-tetraphenylporphyrinate (CdTPPBr) with zinc acetate in dimethylformamide was spectrophotometrically examined. The kinetic parameters of the metal exchange reaction were determined. A possible stoichiometric mechanism of the reaction was suggested. The effect of the bromo substituent in β-position of the pyrrole in the cadmium tetraphenylporphyrinate on the metal exchange reaction with Zn(OAc)2 in DMF was found.

Natalya V. Chizhova

Papers

Some Aspects of Metal Exchange Between Cadmium Porhyrinate Octa-(4-bromophenyl)porphyrin and Cobalt Chloride in Organic Solvents

Metal-exchange reaction between cadmium tetraphenylporphyrinates and copper(II) in dimethylformamide

Reaction of Metal Exchange of Cadmium 5,10,15,20-Tetraphenylporphyrinate and Its β-Bromo Derivative with Zinc Acetate in Dimethylformamide