Solid-State Behaviour of the Dichlorobenzenes: Actual, Semi-Virtual and Virtual Crystallography

Boese, Roland; Kirchner, Michael T.; Dunitz, Jack D.; Filippini, G.; Gavezzotti, Angelo

doi:10.1002/1522-2675(20010613)84:6<1561::aid-hlca1561>3.0.co;2-m

Cited by 56 publications

(67 citation statements)

References 13 publications

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“…In a previous paper [9], we discussed the experimental crystal structures of the dichlorobenzenes in terms of energy calculations and qualitative geometrical arguments based largely on intermolecular contacts in the crystals. We contrasted the absence of explicit electrostatic terms in the UNI force field with their obligatory presence as an intrinsic feature of other force fields, in particular the Williams force field [10].…”

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confidence: 64%

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Electrostatic Energies in the 1,4-Dichlorobenzene Polymorph Crystals: the Role of Charge Density Overlap Effects in Crystal Packing Analysis

Dunitz¹,

Gavezzotti²

2002

HCA

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For Dieter Seebach: They that go down to the sea in ships, that do business in great waters:These see the works of the Lord, and his wonders in the deep 1 ).Electrostatic and polarization energies for the three known polymorphic crystal structures of 1,4-dichlorobenzene, as well as for one particularly stable virtual crystal structure generated by computer search, were calculated by a new accurate numerical integration method over static molecular charge densities obtained from high level ab initio molecular-orbital calculations. Results are compared with those from standard empirical atom-atom force fields. The new electrostatic energies, which include charge density overlap (penetration) effects, are seen to be much larger than and sometimes of opposite sign to those derived from point-charge models. None of the four polymorphs is substantially more stable than the others on electrostaticenergy grounds. Molecule-molecule electrostatic energies have been calculated for the more important molecular pairs in each of the four structures; trends are found to be very different from those indicated by point-charge energies or by total energies estimated with a parametric atom-atom force field. Conclusions based exclusively on analysis of intermolecular atom contacts and point-charge electrostatics may need to be modified in the light of the new kind of calculation.Introduction. ± Every crystal structure determined by X-ray analysis provides the answer to a question ± what is the molecular structure of the compound? ± and simultaneously poses a new question ± why did the compound choose to crystallize in that particular crystal structure rather than in another? We can describe in precise metrical detail the intermolecular packing that is found to occur in the new crystal structure (or crystal structures, for polymorphism is turning out to be far more common than previously supposed [1]), and there is usually no shortage of ways to −explain× the new structure in terms of local intermolecular interactions. By means of energy calculations with empirical-potential functions, we can usually confirm that the new structure corresponds to a minimum in the calculated energy hypersurface, but that is about as far as our present capabilities can go.For a given molecule of known structure, we still have no good theory that enables us to predict its crystal structure with confidence [2]. There is no deep mystery about this. As far as we can tell, the fundamental physics of supramolecular chemistry are understood. The main problem is that, when molecules are brought into contact, the interaction energy is a complicated function of mutual orientation and distance, with the result that many different packing arrangements of a given molecule can have packing energies within a range of only a few kJ mol À1 . For example, for benzene, 30

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confidence: 64%

“…± Table 1 summarizes experimental information about the three known polymorphs of 1,4-dichlorobenzene as determined by X-ray diffraction at 100 K [11] plus the best virtual structure obtained in our previous study [9]. Since computational crystal structures are energy-optimized without regard of kinetic energies, they are formally 0 K structures.…”

mentioning

confidence: 75%

Electrostatic Energies in the 1,4-Dichlorobenzene Polymorph Crystals: the Role of Charge Density Overlap Effects in Crystal Packing Analysis

Dunitz¹,

Gavezzotti²

2002

HCA

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“…Therefore, the intensity of each peak can give an idea of the relative number of molecules occupying that specific site. [42] Under ambient pressure, the most stable phase at low temperature (< 100 K) is the g phase, followed by the a phase from 281 K to 311 K, and between 311 K and the melting point (325 K) the b phase is more stable. In the spectrum of the capillary in Figure 2 b, three spectroscopic sites (NS, GS, and RS) are observed.…”

Section: Bulk Fluorescence Spectramentioning

confidence: 99%

“…X-ray crystallography has identified at least three metastable phases of p-DCB (a, b, and g). [42] Under ambient pressure, the most stable phase at low temperature (< 100 K) is the g phase, followed by the a phase from 281 K to 311 K, and between 311 K and the melting point (325 K) the b phase is more stable. [43] The crystalline g phase presents a monoclinic structure with two molecules per unit cell.…”

Section: Bulk Fluorescence Spectramentioning

confidence: 99%

Stable Single‐Molecule Lines of Terrylene in Polycrystalline para‐Dichlorobenzene at 1.5 K

et al. 2014

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The spectroscopic properties of single terrylene (Tr) molecules are studied in a polycrystalline matrix of para-dichlorobenzene (p-DCB) at 1.5 K. Samples grown in a glass capillary show a very strong site at 597 nm, which is redshifted by more than 700 cm(-1) from the observed transition energy for Tr in p-DCB prepared as a film on a coverslip (572 nm). Each of these two sites is characterized by measuring their single-molecule spectroscopic parameters at 1.5 K. Lifetime-limited linewidths of 45±5 MHz are found for both sites. Fluorescence detection rates reach 8×10(4) count s(-1) at saturation. The spectral trails of the majority of single molecules show no spectral jumps, indicating an absence of interacting two-level systems; however, the small distribution of linewidths may indicate weak interactions with low-frequency modes. Frequency jumps are observed for 10 % of the molecules. The complete emission spectra from two different single molecules at the center of each of the two sites is presented. Debye-Waller factors of αDW=0.33±0.05 for the normal site (572 nm) and αDW=0.30±0.05 for the red site (597 nm) are reported. This new host-guest system provides a quick and easy way to obtain lifetime-limited single-molecule lines.

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“…This corresponds roughly to the general results of the blind tests, showing that the present state of the art leaves much to be desired. In a recent study of Boese et al 13 comparable DE values (1 to 2 kJ mol À1 ) were found for the three dichlorobenzenes in the UNI force field of Filippini and Gavezzotti. 6 Neither in that work nor in the present study was the correct order of the three polymorphs of para-dichlorobenzene reproduced.…”

Section: Crystal Structure Predictionmentioning

confidence: 99%

Crystal structure predictions for disordered halobenzenes

Eijck

2002

Phys. Chem. Chem. Phys.

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Two existing force fields were adjusted for optimal reproduction of the crystal structures and lattice energies of halogenated benzenes and naphthalenes. Crystal structure predictions, including structures with two independent molecules, were made for 21 compounds. It was found that the two force fields, with different functional forms, led to comparable values for the energy of the experimental structures with respect to the global energy minima. These force fields were used for the prediction of disorder in para-substituted benzenes, without using other experimental data. This was done by artificially creating disorder in the most promising hypothetical ordered structures, and comparing the excess energy with RT ln 2. Predictions of the occurrence of orientational disorder in asymmetrically substituted compounds were in agreement with experimental evidence. A comparable approach was followed to study the possibility of mixed crystals consisting of two symmetrically substituted para-dihalobenzenes. It appeared to be possible to estimate the randomization energy for mixtures consisting of two isomorphic compounds. However, the question whether or not such isomorphic compounds will exist in the real world could not be answered with the currently available force fields and methods.

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Solid-State Behaviour of the Dichlorobenzenes: Actual, Semi-Virtual and Virtual Crystallography

Cited by 56 publications

References 13 publications

Electrostatic Energies in the 1,4-Dichlorobenzene Polymorph Crystals: the Role of Charge Density Overlap Effects in Crystal Packing Analysis

Electrostatic Energies in the 1,4-Dichlorobenzene Polymorph Crystals: the Role of Charge Density Overlap Effects in Crystal Packing Analysis

Stable Single‐Molecule Lines of Terrylene in Polycrystalline para‐Dichlorobenzene at 1.5 K

Crystal structure predictions for disordered halobenzenes

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