CF-252 PLASMA DESORPTION MASS-SPECTROMETRY IN THE SYNTHESIS OF PORPHYRIN MODEL SYSTEMS

Cf-252 plasma desorption mass spectrometry has been used in the characterization of more than 100 synthetic porphyrins ranging in mass from 614 u for tetraphenylporphyrin to over 2000 u for some porphyrin model systems. In virtually every case, Cf-252 plasma desorption mass spectrometry yielded an intense ionized molecule ion [M.+ and/or (M + H)+], irrespective of the groups appended to the porphyrin. The appended groups include carboxylic acids, amides, imides, chloroacetamides, Fmoc-protected amino acids, aromatic amines, nitriles, alkynes, alkenes, esters, active esters, benzyl ethers, acetals, dithioacetals, ketones, imines, phenols, quinone, hydroquinone, ferrocene, cyanine dyes, trimethyisilyl protecting groups, nitro groups, and combinations of these functionalities. Metalloporphyrins and porphyrin-porphyrin dimers are also analyzed with ease. Resolved isotopic peaks wore observed for porphyrins with molecular weights below 1000, and unresolved isotopic peaks yielding average masses were observed for porphyrins compounds with higher molecular weights. The limited resolution in the higher molecular weight range does not lessen the utility of the method because the observation of the molecule ions [M.+ and/or (M + H)+] provides unambiguous evidence concerning the success of the synthesis. The Cf-252 plasma desorption mass spectra of porphyrins are not complicated by chemical transformations. This method is ideally suited for rapid analysis of synthetic porphyrins and provides a powerful tool for chemists engaged in the synthesis of complex organic molecules.