29 research outputs found
Quantitative Investigation of Polymorphism in 3-(Trifluoromethyl)-N-[2-(trifluoromethyl) phenyl] benzamide
info:eu-repo/semantics/publishe
Effect of chemical substitution on the construction of boroxine-based supramolecularcrystalline polymers featuring BâN dative bonds
Assessing the Significance of Hexafluorobenzene as a Unique Guest Agent through Stacking Interactions in Substituted Ethynylphenyl Benzamides
A series of differently
substituted host molecules have been employed
to systematically investigate the nature and strength of the stacking
interactions with hexafluorobenzene in the solid state. The hexafluorobenzene
guest binds to the crystal lattice of the parent compound, the <i>N</i>-ethynylphenyl benzamide host and its nine other halogenated
(-F/-CF3/-Cl/-Br at ortho/meta/para positions individually) analogues
via stacking of aromatic rings. The geometrical and energetic features
of intermolecular interactions in hostâguest molecules have
been investigated, and the results elucidate the dominancy of dispersion
in the stabilization of the aryl-hexafluorobenzene stacking, while
the electrostatic component also plays an important role. The plots
of the molecular electrostatic potential provide a fundamental basis
of the electrostatic complementarity that exists in between the host
and the guest. The topological characterization reveals unambiguous
evidence for the direct participation of the substituents in closed-shell
bonding interactions with the aromatic rings at the local geometry,
which remarkably controls the nature and energetics of such motifs.
Additionally, the observed upfield 19F NMR chemical shifts for perfluorinated
guest upon complexation with the host compounds provide evidence for
the existence of the hostâguest stacking interaction also in
the solution state
Structural mapping of mechanically flexible photoluminescent and photodynamic molecular crystals
Mechanically flexible luminescent organic crystals have become an essential part of modern technologies like optoelectronics, while photoluminescent crystals, able to transform light energy into mechanical motions, are a promising choice for actuating and photonic devices. Here, we present our findings on how quantitative structural mapping can rationalize the change in phosphorescence emission, as a function of the flexibility of elastic single crystals of dibenzothiophene and its brominated derivate. The dibenzothiophene crystals show dual fluorescence (FL) and room temperature phosphorescence (RTP), while the bromo derivative only shows RTP. We further present how the photosalient behavior of room temperature phosphorescent molecular crystals, based on organoboron containing Lewis acid-base adducts, can be explained by crystal-to- crystal [2+2] cycloaddition reactions as the driving force. The latter crystals display short-lived room temperature phosphorescence, while the photodynamic events are accompanied by enhancement of their phosphorescence intensity
Silicone Oil Induced Spontaneous Single-Crystal-to-Single-Crystal Phase Transitions in Ethynyl Substituted <i>ortho</i>- and <i>meta</i>-Fluorinated Benzamides
We present an unusual
observation of facile single-crystal-to-single-crystal
phase transition induced in hydrophobic silicone oil at ambient conditions
which is fast in <i>ortho</i>-fluoro substituted ethynyl
phenyl benzamide and relatively slow for the <i>meta</i>-isomer. These phase transitions are also observed in crystals, on
heating, at high temperature, and in the absence of silicone oil.
The extensive thermal and structural analyses reveal that the phase
transition between the two polymorphs of the <i>ortho</i>-isomer is monotropic in nature and involves large supramolecular
rearrangements, wherein for the <i>meta</i>-isomer the same
is enantiotropic and is driven by altered molecular conformations.
The structural features demonstrate the absence of prevalent and strong
NîžH···Oî»C hydrogen bonds in the crystal
structures of both polymorphs of the <i>ortho</i>-fluoro
substituted benzamide. A plausible molecular mechanism based on energetically
favored âstructural motifsâ has been proposed which
depicts that rotational and translational motion between the molecules
present in the crystal relates molecular motifs and provides a rationale
for the origin of the nucleation and growth process during the phase
transition
Observation of Rapid Desolvation of Hexafluorobenzene Involving Single-Crystal-to-Single-Crystal Phase Transition in a Nonporous Organic Host
We report an unusual
occurrence of an extremely fast single-crystal-to-single-crystal
phase transition induced by rapid desolvation of hexafluorobenzene
at room temperature mediated by a subtle interplay of Ï···Ï
stacking interactions in <i>N</i>-(3-ethynylphenyl)-4-fluorobenzamide.
The nature of the hostâguest stacking interaction has been
explored in terms of interaction energy, electrostatic complementarity,
and topological analysis with the inputs from reduced density gradient-noncovalent
interactions fingerprint descriptor. Furthermore, the compound also
exists in two other nonsolvated polymorphic forms
Effect of chemical substitution on the construction of boroxine-based supramolecular crystalline polymers featuring BâN dative bonds
We report the mechanochemical synthesis of five single-crystalline phenylboroxine and 1,4-diazabicyclo[2.2.2]octane (DABCO) ligand-based adducts, directed by boron-nitrogen dative bonds. By tuning the electronic features of the phenylboroxines by chemical modifications (-H/-OMe/-F/-Cl/-Br) at the para-position, the formation of the resulting bicomponent adducts can be controlled to obtain molecular to 1D polymeric crystalline materials. The electrostatic and quantum topological aspects of the B <- N bonds reveal the origin for the different binding modes of the boroxine-DABCO adducts yielding molecular to polymeric structures
Photomechanical Motions in Organoboron-Based Phosphorescent Molecular Crystals Driven by a Crystal-State [2 + 2] Cycloaddition Reaction
Photoluminescent molecular crystals integrated with the
ability
to transform light energy into macroscopic mechanical motions are
a promising choice of materials for both actuating and photonic devices.
However, such dynamic photomechanical effects, based on molecular
organoboron compounds as well as phosphorescent crystalline materials,
are not yet known. Here we present an intriguing example of photomechanical
molecular single crystals of a newly synthesized organoboron containing
Lewis acidâbase molecular adduct (BN1, substituted triphenylboroxine
and 1,2-di(4-pyridyl)ethylene) having a capsule shape molecular geometry.
The single crystals of BN1 under UV light exhibit controllable rapid
bendingâshape recovery, delamination, violent splittingâjumping,
and expanding features. The detailed structural investigation by single-crystal
X-ray diffraction and 1H NMR spectroscopy reveals that
the photosalient behavior of the BN1 single crystals is driven by
a crystal-to-crystal [2 + 2] cycloaddition reaction, supported by
four donorâacceptor type BâN bonds. The instant photomechanical
reaction in the BN1 crystals occurs under UV on account of sudden
release of stress associated with the strained molecular geometry,
significant solid-state molecular movements (supramolecular change),
and cleavage of half intermolecular BâN linkages to result
in a complete photodimerized single-crystalline product via the existence
of two other intermediate photoproducts. In addition, the BN1 crystals
display short-lived room temperature phosphorescence, and the photodynamic
events are accompanied by the enhancement of their phosphorescence
intensity to yield the photoproduct. Interestingly, the molecular
crystals of the final photoproduct polymerize at ambient conditions
when recrystallized from the solution forming a 2D supramolecular
crystalline polymer stabilized by the retention of all BâN
coordination modes
Quantitative Investigation of Polymorphism in 3â(Trifluoromethyl)â<i>N</i>â[2-(trifluoromethyl)phenyl]benzamide
The occurrence of concomitant dimorphism
has been observed in the
case of trifluoromethyl substituted benzanilide, namely, 3-(trifluoromethyl)-<i>N</i>-[2-(trifluoromethyl)Âphenyl]Âbenzamide, wherein both forms
show the presence of a multiple number of molecules in the asymmetric
unit (<i>Z</i>âČ > 1). Thermal studies confirm
the
âextremely rare occurrenceâ of simultaneous melting
and solid-to-solid phase transition at the same temperature from centrosymmetric, <i>Z</i>âČ = 2 structure (triclinic, <i>P</i>1Ì
,
form I) to noncentrosymmetric, <i>Z</i>âČ = 4 structure
(monoclinic, <i>Cc</i>). Both forms exhibit similar density
and lattice energy. Conformationally different molecules in the asymmetric
unit in both the high-<i>Z</i>âČ structures are observed
to be connected with strong NâH···Oî»C
and weak CâH···Oî»C hydrogen bonds. The
dissimilarities in the crystal packing were analyzed by Xpac method,
and the moleculeâmolecule interaction energies were evaluated
by the PIXEL method. The results revealed the presence of 2D isostructurality
between the two forms which mainly consists of the most stabilized
intermolecular interactions (namely, strong N- H···Oî»C,
CâH···Oî»C, and CâH···Ï
hydrogen bonds) in their crystal packing while differences in their
crystal packing are mainly on account of the presence of weak CâH···FâCÂ(sp<sup>3</sup>) hydrogen bond and CÂ(sp<sup>3</sup>)âF···FâCÂ(sp<sup>3</sup>) interactions