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Molecular and Crystal Structures of N-Picryl-m-phenolidine and Investigation of...

Nogueira, Bernardo Albuquerque; Lopes, Susana Margarida Martins; Pinho e Melo, Teresa; Paixão, José António de Carvalho; Milani, Alberto

The molecular and crystal structures of N-picryl-m-phenolidine (or, 3-(2,4,6-trinitrophenylamino)phenol; TAP) were investigated by quantum chemical electronic structure calculations (including state-of-the-art fully-periodic DFT calculations for the crystal) and single crystal X-ray diffraction. The molecule of the compound has four low-energy conformers, which have calculated relative energies within 0.7 kJ mo...


Color Polymorphs of ROY-ol

Nogueira, Bernardo A.; Lopes, Susana M. M.; Milani, Alberto; André, Vânia; Paixão, José A.; Eusébio, M. Ermelinda S.; Melo, Teresa M. V. D. Pinho e

Color polymorphism is a fascinating property exhibited by compounds that have polymorphs of different colors. The most famous family of substances forming molecular organic color polymorphs is the ROY family of compounds. ROY, which states for the red, orange, and yellow colors of the polymorphs of 5-methyl-2-((2-nitrophenyl)amino)thiophene-3-carbonitrile, is currently the compound exhibiting the largest number...


2,4,6-Trinitro-N-(m-tolyl)aniline: A New Polymorphic Material Exhibiting Differ...

Nogueira, Bernardo Albuquerque; Lopes, Susana Margarida Martins; Lopes, Susy Branco; Nikitin, Timur; Rodrigues, Ana Clara Beltran

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 crysta...


The correlation between experimental polarized Raman spectra and their density ...

Nogueira, Bernardo Albuquerque; Milani, Alberto; Castiglioni, Chiara; Fausto, Rui

In this study, the polarized Raman spectra of the R3c LiNbO3 crystal are used as a benchmark test for density functional theory (DFT) full periodic boundary conditions linear combination of atomic orbitals (LCAO) calculation of the Raman tensors, according to the implementation in the CRYSTAL software. The theoretical approach used proved to provide excellent results regarding wavenumbers and relative intensiti...


2,4,6-Trinitro-N-(m-tolyl)aniline: A New Polymorphic Material Exhibiting Differ...

Nogueira, Bernardo A.; Lopes, Susana M. M.; Lopes, Susy; Nikitin, Timur; Rodrigues, Ana Clara B.; Eusébio, Maria Ermelinda S.; Paixão, J. A.

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 matrixisolation infrared spectroscopy) and its polymorphic cryst...


Polymorphism in 1-methylhydantoin: Investigation by periodic DFT calculations a...

Nogueira, Bernardo Albuquerque; Milani, Alberto; Ogruc Ildiz, Gulce; Paixão, J. A.; Castiglioni, Chiara; Rui Fausto

In previous studies [Puszyńska-Tuszkanow et al. Polyhedron, 2011, 30(12), 2016; Nogueira et al. J. Phys. Chem. A, 2014, 118(31), 5994; Nogueira et al., J. Mol. Struct., 2017, 1148, 111], two different polymorphs of 1-methylhydantoin (1-MH, C4H6N2O2) were identified (forms I and II) and characterized using infrared and Raman spectroscopies, as well as by X-ray diffraction. In this work, a new polymorph of the co...


Color polymorphism in organic crystals

Nogueira, Bernardo A.; Castiglioni, Chiara; Fausto, Rui

Color polymorphism is an interesting property of chemical systems which present crystal polymorphs of different colors. It is a rare phenomenon, with only a few examples reported in the literature hitherto. Nevertheless, systems exhibiting color polymorphism have many potential applications in different domains, such as pigment, sensor, and technology industries. Here, known representative chemical systems show...


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