Dyeing polymorphs: The MALDI host 2,5-dihydroxybenzoic acid

Dawn E. Cohen, Jason B. Benedict, Brian Morlan, Daniel T. Chiu, Bart Kahr

Research output: Contribution to journalArticlepeer-review


The dye methyl red was used to distinguish concomitant polymorphs of the matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) host, 2,5-dihydroxybenzoic acid. Red and purple crystals were readily separated by inspection. They corresponded to the known Form I (P21/c, a = 4.9110(3) Å, b = 11.8280(7) Å, c = 11.0580(6) Å, β = 91.059(3)°, V = 642.22 Å3) and Form II (P21/c, a = 5.5610(2) Å, b = 4.8690(1) Å, c = 23.6880 (8) Å, β = 100.191(1)°, V = 631.27 Å3), respectively. X-ray structures of cocrystals of dihydroxybenzoic acids and methyl red, measurements of the linear dichroism of mixed crystals, and force-field calculations were used to investigate the mechanism of differential coloring. The relevance of the observations to investigations of the MALDI mechanism are discussed.

Original languageEnglish (US)
Pages (from-to)492-495
Number of pages4
JournalCrystal Growth and Design
Issue number3
StatePublished - Mar 2007

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


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