Synthetic organic pigments (SOP’s) have been used in works of art in various media for over 100 years. During this time, hundreds have been introduced. Raman spectroscopy and LDI/MS provide complementary information about pigments and are the most useful techniques for their characterization. Raman spectroscopy is particularly useful with pigments with their extended conjugated π-system because the signal is dependent upon change in polarization of the molecule. LDI/MS was performed in both positive and negative ion modes; the negative ion spectra in general has less fragmentation and are useful in identifying the molecular ion.<br/>A series of novel symmetrical and non-symmetrical pigments were synthesized as part of a Capstone Research course at the Naval Academy. The central starting material was Naphthol AS-G (N, N’-Bis(acetoacetyl)-o-toluidine, Fig. 1). It has an acidic hydrogen on each acetoacetyl group. Each react sequentially with substituted aniline derived diazonium salts. Fifteen bis-diazo pigments from five anilines—3-aminobenzonitrile, p-anisidine, 2,5-dichloroaniline, 2,4-dinitroaniline, and 4-(trifluoromethyl)aniline—were synthesized and characterized. A Designer Library of products can be made from the symmetric, bi-functional starting material, thus providing a more personal synthetic laboratory experience in institutions large and small. The strategy is useful for the undergraduate laboratory because 1) the solubility of starting materials, 2) the insolubility and deep color of the products, and 3) microscale of the synthesis based on small analytical sample size used in Raman and LDI-MS.

Designer pigment libraries: Synthesis and analysis of pigments derived from naphthol AS-G by Raman and LDI-MS

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.