2,2′′-Bis(bromomethyl)-p-terphenyl
01 Sep 2005-Acta Crystallographica Section E-structure Reports Online (Munksgaard International Publishers)-Vol. 61, Iss: 9
TL;DR: The C20H16Br2 compound as mentioned in this paper displays crystallographic inversion symmetry, and two C-H⋯Br inter-actions link the molcule into layers parallel to (\overline{1}11).
Abstract: The molecule of the title compound, C20H16Br2, displays crystallographic inversion symmetry. Two C—H⋯Br interactions link the molecules into layers parallel to (\overline{1}11). The shortest Br⋯Br contact is 4.1599 (4) A.
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TL;DR: In this article, two new crystalline host compounds of bisfluorenol type featuring an elongated core structure compared to a known parent molecule (2,2′′]-1,1′:4′, 1′-1′]-terphenylyl versus 2, 2′-biphenylyl) have been synthesized.
Abstract: Two new crystalline host compounds of bisfluorenol type featuring an elongated core structure compared to a known parent molecule (2,2′′-[1,1′:4′,1′′]-terphenylyl versus 2,2′-biphenylyl) have been synthesized. Crystalline inclusion compounds involving protic guest molecules have been prepared and studied with reference to their crystal structures. Conformational changes as against the prototype compound due to prevention of the intramolecular hydrogen bond between the hydroxy groups give rise to a specific mode of host–guest association, showing preference to the formation of infinite hydrogen bonded chains instead of discrete host–guest units. Potentiality for crystal engineering using respective two-component molecular systems is indicated.
7 citations
TL;DR: In the crystal structure of 2,2′′-bis(2,7-dichloro- 9-hydroxy-9-fluorenyl)-1,1′:4′,1-terphenyl as the tris(triethylamine) solvate, the diol host molecule possesses a ‘folded’ molecular conformation with inversion symmetry.
Abstract: In the title solvate, C44H26Cl4O2·3C6H15N, the asymmetric part of the unit cell comprises two halves of the diol molecules, 2,2′′-bis(2,7-dichloro-9-hydroxy-9H-fluoren-9-yl)-1,1′:4′,1′′-terphenyl, and three molecules of triethylamine, i. e. the diol molecules are located on crystallographic symmetry centres. Two of the solvent molecules are disordered over two positions [occupancy ratios of 0.567 (3):0.433 (3) and 0.503 (3):0.497 (3)]. In the diol molecules, the outer rings of the 1,1′:4′,1′′-terphenyl elements are twisted with reference to their central arene ring and the mean planes of the fluorenyl moieties are inclined with respect to the terphenyl ring to which they are connected, the latter making dihedral angles of 82.05 (8) and 82.28 (8)°. The presence of two 9-fluoren-9-ol units attached at positions 2 and 2′′ of the terphenyl moiety induces a `folded' geometry which is stabilized by intramolecular C—H⋯O hydrogen bonds and π–π stacking interactions, the latter formed between the fluorenyl units and the central ring of the terphenyl unit [centroid–centroid distances = 3.559 (1) and 3.562 (1) A]. The crystal is composed of 1:2 complex units, in which the solvent molecules are associated with the diol molecules via O—H⋯N hydrogen bonds, while the remaining solvent molecule is linked to the host by a C—H⋯N hydrogen bond. The given pattern of intermolecular interactions results in formation of chain structures extending along [010].
3 citations
TL;DR: In this article, the synthesis, crystal structure, polymorphism and dielectric properties of two 2,2′-bis-substituted para-terphenyls were reported.
Abstract: In the past decades, para-terphenyls have been attracting tremendous attention due to their polymorphism and conformational diversity. In this work we report the synthesis, crystal structure, polymorphism and dielectric properties of two 2,2′′-bis-substituted para-terphenyls: 2,2′′-bis(hydroxymethyl)-para-terphenyl and 2,2′′-bis(acetyloxymethyl)-para-terphenyl. On the basis of calorimetric and X-ray studies, we showed that the latter compound occurs in at least four polymorphic forms with melting points equal to 364, 345, 341 and 326 K, differentiated also in terms of thermodynamic stability and crystal symmetry. The most stable polymorph I is characterized by the P21/n space group. 2,2′′-Bis(hydroxymethyl)-para-terphenyl crystallizes in the monoclinic P21/c space group. Both 2,2′′-bis-substituted para-terphenyls can undergo vitrification, which is a highly exceptional feature for this class of chemical compounds and has not been reported before. Consequently, the molecular dynamics and conformational changes in the glassy and supercooled liquid states were analyzed by means of IR and broadband dielectric spectroscopy. Two relaxation processes were observed for both compounds: structural α-relaxation, connected with reorientational motions of molecules in supercooled liquid, and intermolecular γ-relaxation, ascribed to rotational motions of substituents of the para-terphenyl skeleton. Taking into account the ongoing discussion about the conformational diversity of the para-terphenyl skeleton, we showed that although free rotation of benzene rings is suppressed, the molecules in the glassy and liquid states can adopt both twisted and helical conformations, which results in diversity of the polymorphic forms.
2 citations
TL;DR: In the solvent-free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O-H···π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor.
Abstract: Having reference to an elongated structural modification of 2,2'-bis(hydroxydiphenylmethyl)biphenyl, (I), the two 1,1':4',1''-terphenyl-based diol hosts 2,2''-bis(hydroxydiphenylmethyl)-1,1':4',1''-terphenyl, C44H34O2, (II), and 2,2''-bis[hydroxybis(4-methylphenyl)methyl]-1,1':4',1''-terphenyl, C48H42O2, (III), have been synthesized and studied with regard to their crystal structures involving different inclusions, i.e. (II) with dimethylformamide (DMF), C44H34O2·C2H6NO, denoted (IIa), (III) with DMF, C48H42O2·C2H6NO, denoted (IIIa), and (III) with acetonitrile, C48H42O2·CH3CN, denoted (IIIb). In the solvent-free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O-H···π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor. The corresponding crystal structures are stabilized by intermolecular C-H···π contacts. Due to the distinctive acceptor character of the included DMF solvent species in the crystal structures of (IIa) and (IIIa), the guest molecule is coordinated to the host via O-H···O=C hydrogen bonding. In both crystal structures, infinite strands composed of alternating host and guest molecules represent the basic supramolecular aggregates. Within a given strand, the O atom of the solvent molecule acts as a bifurcated acceptor. Similar to the solvent-free cases, the hydroxy H atoms in inclusion structure (IIIb) are involved in intramolecular hydrogen bonding, and there is thus a lack of host-guest interaction. As a result, the solvent molecules are accommodated as C-H···N hydrogen-bonded inversion-symmetric dimers in the channel-like voids of the host lattice.
TL;DR: In the title compound, C14H12Br2, the Br atoms lie on opposite sides of their ring plane, the biphenyl interplanar angle is 53.52 (8)°.
Abstract: In the title compound, C14H12Br2, the Br atoms lie on opposite sides of their ring plane. The biphenyl interplanar angle is 53.52 (8)°. The packing is characterized by several H⋯Br contacts to each Br atom, but at long distances of 3.07–3.43 A.
Cites background from "2,2′′-Bis(bromomethyl)-p-terphen..."
...Related literature For the structures of bromomethyl-substituted aromatic ring systems, see: Jones & Kuś (2005, 2007); Jones et al. (2007)....
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...We are interested in the structures of bromomethyl-substituted aromatic ring systems, compounds that are often used as synthestic intermediates; e.g. various bromomethylbenzenes (Jones & Kuś, 2007), 2,2"- and 2',5'- bis(bromomethyl)-p-terphenyl (Jones & Kuś, 2005; Jones et al., 2007)....
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TL;DR: In this article, a phase annealing method, related to the simulated-annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution.
Abstract: A number of extensions to the multisolution approach to the crystallographic phase problem are discussed in which the negative quartet relations play an important role. A phase annealing method, related to the simulated annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution. The ideas presented here are incorporated in the program system SHELX-90; the philosophical and mathematical background to the direct-methods part (SHELXS) of this system is described.
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