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Reduction of analytes in matrix-assisted laser desorption/ionization (MALDI) often obscures the actual determination of molecular structure. To address the redox reactions in laser desorption/ionization processes, the organic dyes Methylene Blue, Janus Green B, Crystal Violet and Rhodamine B were analyzed by MALDI or by desorption/ionization on porous silicon (DIOS). Susceptibility to reduction in MALDI was dependent on both the reduction potentials of analytes and the molar ratio of analyte to matrix molecules. Addition of Cu(II) ions as an electron scavenger suppressed the reduction of Methylene Blue in MALDI. The results suggested that electron transfer to analytes from the sample target and/or from the matrix contributed to the reduction. In DIOS, the reductions of organic dyes were more prominent than in MALDI, and were not prevented by Cu(II) ion doping, probably due to direct contact of the analytes with silicon which had little electric resistance.

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Paraelectric behavior due to a dynamic Jahn-Teller ͑JT͒ effect is reported for the manganese͑III͒ spincrossover complex ͓Mn͑taa͔͒ ͓H 3 taaϭtris"1-(2-azolyl)-2-azabuten-4Ϫyl…amine͔ in the high-spin ͑HS͒ phase above T c ϭ48 K. The dielectric constant obeys the Curie-Weiss law with an asymptotic Curie temperature 26 K, suggesting competition between a low-spin ͑LS͒ phase and a ferrodistortively ordered ͑FO͒ phase at low temperatures. A phase diagram based on a four-state Ising-Potts model incorporating both a virtual cooperative JT transition (HS↔FO) and a spin-crossover transition (HS↔LS) is proposed to elucidate the interrelation of the HS, LS, and FO phases.