Please use this identifier to cite or link to this item: http://hdl.handle.net/10316/99945
Title: 2,4,6-Trinitro-N-(m-tolyl)aniline: A New Polymorphic Material Exhibiting Different Colors
Authors: Nogueira, Bernardo Albuquerque 
Lopes, Susana Margarida Martins 
Lopes, Susy Branco 
Nikitin, Timur 
Rodrigues, Ana Clara Beltran 
Eusébio, Maria Ermelinda da Silva 
Paixão, José António de Carvalho 
Melo, Teresa Margarida Vasconcelos Dias de Pinho e 
Milani, Alberto 
Castiglioni, Chiara 
Fausto, Rui 
Keywords: 2,4,6-trinitro-N-(m-tolyl)aniline; color polymorphism; molecular structure; crystal structure; thermal analysis; infrared, Raman and UV-Vis spectroscopies
Issue Date: 18-Nov-2021
Publisher: American Chemical Society
Project: UIDB/00313/2020 
UIDP/00313/2020 
UIDB/04564/2020 
UIDP/04564/2020 
SFRH/BD/129852/2017 
Serial title, monograph or event: Cryst. Growth Des.
Volume: 12
Issue: 21
Abstract: 2,4,6-Trinitro-N-(m-tolyl)aniline or N-picryl-m-toluidine (abbreviated as TMA), exhibiting color polymorphism, was synthesized and characterized structurally, spectroscopically and thermodynamically. The studies consider both the isolated molecule of the compound (studied theoretically at the DFT(B3LYP)/6-311++G(d,p) level, and experimentally by matrix isolation infrared spectroscopy) and its polymorphic crystalline phases. The investigations on the isolated molecule allowed to evaluate the major intramolecular interactions determining the conformational preferences of the compound, and characterize it in detail from the vibrational point of view. Two conformers were found (A and B), which differ in the relative orientation of the ring moieties of the molecule. Polymorph screening, by recrystallization of the compound using different solvents, allowed to identify three different polymorphs, exhibiting red, orange and yellow colors, which were subsequently characterized structurally by single crystal X-ray diffraction, vibrationally, by infrared and Raman spectroscopies (complemented by fully-periodic DFT calculations on the crystals), electronically, using solid state ultraviolet-visible absorption spectroscopy, and thermodynamically, by differential scanning calorimetry and polarized light thermomicroscopy. The yellow polymorph was found to be a conformational polymorph of the orange and red ones, while the last two are packing polymorphs. Mechanistic insights on the causes of the different colors of the polymorphs are presented. On the whole, the reported investigation constitutes a comprehensive structural (for both the isolated molecule and crystalline phases), spectroscopic and thermal analysis of the newly prepared compound, with particular emphasis on the rare color polymorphism it exhibits.
URI: http://hdl.handle.net/10316/99945
ISSN: 1528-7483
DOI: 10.1021/acs.cgd.1c01123
Rights: openAccess
Appears in Collections:I&D CQC - Artigos em Revistas Internacionais

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