Conformational polymorphism of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate. II. Structural, thermodynamic, kinetic and mechanistic aspects of phase transformations among the three crystal forms

Richardson, Mary Frances; Yang, Quing-Chuan; Novotny-Bregger, Elisabeth; Dunitz, Jack D.

doi:10.1107/s0108768190005857

Cited by 43 publications

(24 citation statements)

References 2 publications

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“…A less tightly packed crystal structure should favour lower-frequency lattice vibrations and hence lead to an increase in the thermal (energy dispersion) contribution to the entropy. This is in agreement with the general rule that, among polymorphs, the low-temperature form has the higher density [27]. Computer generation of many crystal structures for the same molecule is the ideal computational experiment to test these expectations.…”

supporting

confidence: 66%

Molecular Shape and Crystal Packing: a Study of C12H12 Isomers, Real and Imaginary

Dunitz

Filippini

Gavezzotti

2000

HCA

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supporting

confidence: 66%

Molecular Shape and Crystal Packing: a Study of C12H12 Isomers, Real and Imaginary

Dunitz

Filippini

Gavezzotti

2000

HCA

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“…Improved insight can be gained by studying phase transitions and thermodynamic behaviour. The interest of crystallographers in phase transitions, especially of molecular crystals, therefore, has increased considerably (Dunitz, 1995;Richardson, Yang, Novotny-Bregger & Dunitz, 1990). The interest of crystallographers in phase transitions, especially of molecular crystals, therefore, has increased considerably (Dunitz, 1995;Richardson, Yang, Novotny-Bregger & Dunitz, 1990).…”

Section: Introductionmentioning

confidence: 99%

Trimorphism of 2,2'-dipyridylamine: structures, phase transitions and thermodynamic stabilities

Schödel¹,

Näther²,

Bock³

et al. 1996

Acta Crystallogr Sect B

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Crystals of an unknown third crystalline modification of 2,2'-dipyridylamine were obtained from acetone solution and their crystal structure was determined at both 150K and room temperature. In contrast to the known orthorhombic and triclinic forms, which contain hydrogen-bridged dimers, the molecules of the monoclinic polymorph are arranged in tetramers. The crystallographic results for the monoclinic form are presented here, as well as a detailed comparison of crystal and molecular structures of the three polymorphs. Studies by differential thermal analysis (DTA) and optical microscopy, performed with single crystals, show a transformation of the orthorhombic phase at --~323 K and of the monoclinic form at --~368 K. According to powder diffraction studies, transformation of the low melting orthorhombic polymorph results in a mixture of monoclinic and triclinic phases, whereas the monoclinic modification transforms into the triclinic phase just below its melting point at 368 K. The single crystals of both forms are destroyed during the conversion and, therefore, in both cases a reconstructive transition via nucleation and growth should occur. The conditions for the crystallization of the distinct modifications and their relative thermodynamic stabilities are investigated in different solvents and at different temperatures. Independent of the solvent chosen, the orthorhombic form is the most stable below 263K. In the range between 263 and 313 K the monoclinic form appears to be thermodynamically advantageous and above that temperature, the stability order is changed in favour of the triclinic polymorph. Based on the experimental results, a qualitative free energy-temperature diagram is provided.

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“…In this paper, one will focus on the six most representative families of compounds displaying color polymorphism, whose most famous members are represented in Fig. 2: N-(4-methyl-2-nitrophenyl) acetamide [20][21][22][23][24][25][26] , dimethyl 2,5-dichloro-3,6-dihydroxyterephthalate [27][28][29][30][31][32][33][34][35] , 5-methyl-2-((2-nitrophenyl)amino)thiophene-3-carbonitrile (ROY) [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] , 2,4,6-trinitro-N-(p-tolyl)aniline [54][55][56][57][58][59][60][61] , dimethyl-5-benzoyl-3-phenylindolizine-1,2-dicarboxylate 14 , and 1,4,7,10-tetrabutyltetracene [62][63][64] .…”

mentioning

confidence: 99%

Color polymorphism in organic crystals

2020

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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 showing color polymorphism are reviewed, and the reasons for them to present such property discussed. Also, since some of the concepts related to color polymorphism have been frequently used imprecisely in the scientific literature, this article provides concise, systematic definitions for these concepts. T his paper focuses on color polymorphism, a fascinating property exhibited by chemical systems that present polymorphs showing different colors. In the first few sections, unambiguous definitions of the structural properties and of the relevant physical concepts related with this subject will be provided, since some of them have been frequently used in an imprecise way in the scientific literature. Then, the physicochemical reasons leading to color polymorphism will be described briefly using an essentially phenomenological approach. The last few sections of this paper will survey representative chemical systems showing color polymorphism. Terminology Polymorphism. In the crystallographic context, polymorphism, from the Greek poly (many) and morphe (form), also known as crystal polymorphism, refers to the ability of a certain compound to exist in different crystallographic structures, resulting from different packing arrangements of its molecules in the crystal structure 1. It is worth to differentiate between polymorphism and allotrophism. While the latter term describes the existence of different crystal structures of the same element, polymorphism is used regarding different crystalline structures of compounds. It is also important to mention that in this review, one will not consider solvates, hydrates, or dynamic isomers (including geometric isomers and tautomers) as polymorphic phases, but instead, as pseudopolymorphic states. Hence, a safe criterion for the classification of a system as polymorphic would be if the crystal structures are different but give rise to the same liquid and vapor states. Why is polymorphism so important? The main reason is that although being composed of the same compound, different polymorphic structures can behave as different materials 2. Indeed, in

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Conformational polymorphism of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate. II. Structural, thermodynamic, kinetic and mechanistic aspects of phase transformations among the three crystal forms

Cited by 43 publications

References 2 publications

Molecular Shape and Crystal Packing: a Study of C12H12 Isomers, Real and Imaginary

Molecular Shape and Crystal Packing: a Study of C12H12 Isomers, Real and Imaginary

Trimorphism of 2,2'-dipyridylamine: structures, phase transitions and thermodynamic stabilities

Color polymorphism in organic crystals

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