A novel oxygen atom transfer reaction. Isomerization of nickel(II) octaethylporphyrin N-oxide to nickel(II) octaethyloxochlorin

Highly Sensitive, Easy-to-Use, One-Step Detection of Peroxide-, Nitrate- and Chlorate-Based Explosives with Electron-Rich Ni Porphyrins

Homemade explosives, such as peroxides, nitrates, and chlorates, are increasingly abused by terrorists, criminals, and amateur chemists. The starting materials are easily accessible and instructions on how to make the explosives are described on the Internet. Safety considerations raise the need to detect these substances quickly and in low concentrations using simple methods. Conventional methods for the detection of these substances require sophisticated, electrically operated, analytical equipment. The simpler chemical detection methods are multistep and require several chemicals. We have developed a simple, one-step method that works similarly to a pH test strip in terms of handling. The analytical reaction is based on an acid-catalyzed oxidation of an electron-rich porphyrin to an unusually stable radical cation and dication. The detection limit for the peroxide-based explosive triacetone triperoxide (TATP), which is very frequently used by terrorists, is 40 ng and thus low enough to detect the substance without direct contact via the gas phase. It is sufficient to bring the stick close to the substance to observe a color change from red to green. Nitrates and chlorates, such as ammonium nitrate, urea nitrate, or potassium chlorate, are detected by direct contact with a sensitivity of 85-350 ng. A color change from red to dark brown is observed. The test thus detects all homemade explosives and distinguishes between the extremely impact-, shock-, and friction-sensitive peroxides and the less sensitive nitrates and chlorates by color change of a simple test strip.

The origin of the absorption spectra of porphyrin N- and dithiaporphyrin S-oxides in their neutral and protonated states

DFT, TDDFT, and SCS-CC2 calculations were used to investigate the excited states of the NIR absorbing neutral and protonated forms of a dithiaporphyrin S-oxide and a porphyrin N-oxide.

Formation of chlorins andmeso-substituted porphyrins through intramolecular nitrogen-carbon migration ofN-substituted porphyrins

A series of N -substituted porphyrins were synthesized either by direct alkylation of the symmetrical porphyrins or from the unsymmetrical porphyrins obtained via MacDonald's procedure using the appropriate N -substituted dipyrromethanes. Depending upon the nature of the peripheral substitutions in the porphyrin system, the nickel(II)-promoted rearrangement of these compounds gave either meso-substituted or unsubstituted Ni(II) porphyrins or chlorins. The chlorins and meso-substituted porphyrins were formed via the intramolecular migration of the N -substituent to carbon. This approach provides easy access for the synthesis of chlorins and the meso-substituted porphyrins, which are otherwise difficult to synthesize.