Outer Phenyl Rings Research Articles

The crystal structures and Hirshfeld surface analysis of three new bromo-substituted 3-methyl-1-(phenylsulfonyl)-1H-indole derivatives

Three new 1H-indole derivatives, namely, 2-(bromomethyl)-3-methyl-1-(phenylsulfonyl)-1H-indole, C16H14BrNO2S, (I), 2-[(E)-2-(2-bromo-5-methoxyphenyl)ethenyl]-3-methyl-1-(phenylsulfonyl)-1H-indole, C24H20BrNO3S, (II), and 2-[(E)-2-(2-bromophenyl)ethenyl]-3-methyl-1-(phenylsulfonyl)-1H-indole, C23H18BrNO2S, (III), exhibit nearly orthogonal orientations of their indole ring systems and sulfonyl-bound phenyl rings. Such conformations are favourable for intermolecular bonding involving sets of slipped π–π interactions between the indole systems and mutual C—H...π hydrogen bonds, with the generation of two-dimensional monoperiodic patterns. The latter are found in all three structures, in the form of supramolecular columns with every pair of successive molecules related by inversion. The crystal packing of the compounds is additionally stabilized by weaker slipped π–π interactions between the outer phenyl rings (in II and III) and by weak C—H...O, C—H...Br and C—H...π hydrogen bonds. The structural significance of the different kinds of interactions agree with the results of a Hirshfeld surface analysis and the calculated interaction energies. In particular, the largest interaction energies (up to −60.8 kJ mol−1) are associated with pairing of antiparallel indole systems, while the energetics of weak hydrogen bonds and phenyl π–π interactions are comparable and account for 13–34 kJ mol−1.

Development of Sulfamoylated 4-(1-Phenyl-1H-1,2,3-triazol-4-yl)phenol Derivatives as Potent Steroid Sulfatase Inhibitors for Efficient Treatment of Breast Cancer.

We present here the advances achieved in the development of new sulfamoylated 4-(1-phenyl-1H-1,2,3-triazol-4-yl)phenol derivatives as potent steroid sulfatase (STS) inhibitors for the treatment of breast cancer. Prompted by promising biological results and in silico analysis, the initial series of similar compounds were extended, appending a variety of m-substituents at the outer phenyl ring. The inhibition profiles of the newly synthesized compounds were evaluated using a radioisotope enzymatic assay and, together with the preceding reported derivatives, using a radioisotope assay in MCF-7 cells. The most active compound, 5l, demonstrated an extraordinary STS inhibitory potency in MCF-7 cells with an IC50 value improved 5-fold compared to that of the reference Irosustat (0.21 vs 1.06 nM). The five most potent compounds were assessed in vivo in a 67NR mouse mammary gland cancer model, with 4b measured to induce up to 51% tumor growth inhibition at 50 mg/kg with no evidence of side effects and toxicity.

Atomically Precise Engineering of Single‐Molecule Stereoelectronic Effect

AbstractCharge transport in a single‐molecule junction is extraordinarily sensitive to both the internal electronic structure of a molecule and its microscopic environment. Two distinct conductance states of a prototype terphenyl molecule are observed, which correspond to the bistability of outer phenyl rings at each end. An azobenzene unit is intentionally introduced through atomically precise side‐functionalization at the central ring of the terphenyl, which is reversibly isomerized between trans and cis forms by either electric or optical stimuli. Both experiment and theory demonstrate that the azobenzene side‐group delicately modulates charge transport in the backbone via a single‐molecule stereoelectronic effect. We reveal that the dihedral angle between the central and outer phenyl ring, as well as the corresponding rotation barrier, is subtly controlled by isomerization, while the behaviors of the phenyl ring away from the azobenzene are hardly affected. This tunability offers a new route to precisely engineer multiconfigurational single‐molecule memories, switches, and sensors.

Atomically Precise Engineering of Single-Molecule Stereoelectronic Effect.

Charge transport in a single-molecule junction is extraordinarily sensitive to both the internal electronic structure of a molecule and its microscopic environment. Two distinct conductance states of a prototype terphenyl molecule are observed, which correspond to the bistability of outer phenyl rings at each end. An azobenzene unit is intentionally introduced through atomically precise side-functionalization at the central ring of the terphenyl, which is reversibly isomerized between trans and cis forms by either electric or optical stimuli. Both experiment and theory demonstrate that the azobenzene side-group delicately modulates charge transport in the backbone via a single-molecule stereoelectronic effect. We reveal that the dihedral angle between the central and outer phenyl ring, as well as the corresponding rotation barrier, is subtly controlled by isomerization, while the behaviors of the phenyl ring away from the azobenzene are hardly affected. This tunability offers a new route to precisely engineer multiconfigurational single-molecule memories, switches, and sensors.

Columnar Propeller‐Like 1,3,5‐Triphenylbenzenes: Probing the Effect of Chlorine on the Suzuki Cross‐Coupling and Liquid Crystalline Properties

Suzuki cross‐couplings either between chlorinated N‐methyliminodiacetic acid (MIDA)‐protected aryl boronates and 1,3,5‐tribromobenzene or between chlorinated aryl bromides and phenyltrisboronic species to star‐shaped 1,3,5‐triphenylbenzenes with different substitution patterns and chloro substituents at the outer phenyl rings were studied. The chlorinated precursors required for the respective reaction were synthesized and characterized. Depending on the used coupling reaction target triphenylbenzenes were isolated in yields between 42 % and 88 %. Their mesomorphic properties were influenced by the substitution pattern and number of peripheral chlorine atoms. Triphenylbenzene with 3,5‐alkoxy substitution and H in para‐position self‐assembled into either columnar hexagonal (Colh) mesophases or a soft crystal. While threefold chloro substitution in meta‐position of the outer phenyl rings led to stable room temperature Colho phases, triphenylbenzenes with threefold para‐chloro or 3,5‐dichloro substitution were non‐mesomorphic. Based on X‐ray diffraction data a helical packing model for the observed phases similar to that of related alkoxy‐substituted triphenylbenzenes was proposed.

Twisting and bending photo-excited phenylethynylbenzenes - a theoretical analysis.

Oligo(phenylethynyl)benzenes are a family of compounds that exhibit a rich photochemistry changing dramatically with different orientation of a phenyl group in the molecule. Quantum-chemical calculations have been performed to investigate different members of this family of compounds and compared to previous experimental and theoretical studies. 1,4-Bis(phenylethynyl)benzene (BPEB) has different optical properties than its smaller relative diphenylacetylene; however, upon twisting an outer phenyl ring of BPEB, its photochemistry becomes very similar. Fluorine substituents at the central benzene ring are shown to have only small effects on the optical properties of BPEB.

Polar Switching and Cybotactic Nematic Ordering in 1,3,4-Thiadiazole-Based Short-Core Hockey Stick-Shaped Fluorescent Liquid Crystals.

We report here the synthesis and thermotropic properties of novel short-core hockey stick-shaped liquid crystalline molecules based on the 1,3,4-thiadiazole core. Polar switching behavior is observed in the cybotactic nematic and smectic mesophases for the bent-core thiadiazole derivatives. The presence of the lateral methoxy moiety in the outer phenyl ring of the four-ring molecules facilitates the formation of spontaneous ordering in the nematic phase observed via X-ray diffraction measurements. Anomalous temperature dependence of spontaneous polarization on cooling is explained by the possible antiferroelectric packing of the molecules that require higher electric field for switching. The compounds exhibited a strong absorption band at ∼356 nm and a blue emission band at ∼445 nm with a good quantum yield of φf ∼0.39. The mega Stokes shift is observed and depends on the nature of the solvent.

Low-temperature nematic phase in azo functionalised reactive hockey stick mesogens possessing lateral methyl group

We report, the design, synthesis and mesomorphic behaviour of new hockey stick mesogens containing photochromic azo group and a reactive double bond. The structure of the compounds resemble the hockey stick due to unequal distribution of the phenyl rings in the two arms of the molecule and possess a reactive 4-n-undecenyloxy chain attached at short arm of the bent-core molecule, while the elongated arm consists of a small methoxy group and photochromic azo linkage between two phenyl rings. All the compounds exhibit a wide-range of enantiotropic nematic phase at low temperature. The photo-responsive behaviour of nematic phase was characterized by polarising optical microscopy with in situ white light irradiation. Upon irradiation, the nematic phase almost completely disappeared in about 20s. We have also investigated the effect of the position of methyl group substitution at the outer phenyl ring of the elongated arm of the molecule on the nematic phase of azo functionalised compounds. Our theoretical calculations predict that different position of methyl group does not bring any significant change in reactivity profile, electronic properties and spectroscopic properties. Irrespective of the position of a methyl group, trans conformation has slightly greater stability as well as less reactivity than cis conformation.

(E)-2-{[(2-Amino-phen-yl)imino]-meth-yl}-5-(benz-yl-oxy)phenol and (Z)-3-benz-yl-oxy-6-{[(5-chloro-2-hy-droxy-phen-yl)amino]-methyl-idene}cyclo-hexa-2,4-dien-1-one.

The title Schiff base compounds, C20H18N2O2 (I) and C20H16ClNO3 (II), were synthesized from 4-benz-yloxy-2-hy-droxy-benzaldehyde by reaction with 1,2-di-amino-benzene for (I), and condensation with 2-amino-4-chloro-phenol for (II). Compound (I) adopts the enol-imine tautomeric form with an E configuration about the C=N imine bond. In contrast, the o-hy-droxy Schiff base (II), is in the keto-imine tautomeric form with a Z configuration about the CH-NH bond. Neither mol-ecule is planar. In (I), the central benzene ring makes dihedral angles of 46.80 (10) and 78.19 (10)° with the outer phenyl-amine and phenyl rings, respectively, while for (II), the corresponding angles are 5.11 (9) and 58.42 (11)°, respectively. The mol-ecular structures of both compounds are affected by the formation of intra-molecular contacts, an O-H⋯N hydrogen bond for (I) and an N-H⋯O hydrogen bond for (II); each contact generates an S(6) ring motif. In the crystal of (I), strong N-H⋯O hydrogen bonds form zigzag chains of mol-ecules along the b-axis direction. Mol-ecules are further linked by C-H⋯π inter-actions and offset π-π contacts and these combine to form a three-dimensional network. The density functional theory (DFT) optimized structure of compound (II), at the B3LYP/6-311+G(d) level, confirmed that the keto tautomeric form of the compound, as found in the structure determination, is the lowest energy form. The anti-oxidant capacities of both compounds were determined by the cupric reducing anti-oxidant capacity (CUPRAC) process.

Crystal structures and antioxidant capacity of (E)-5-benzyloxy-2-{[(4-chlorophenyl)imino]methyl}phenol and (E)-5-benzyloxy-2-({[2-(1H-indol-3-yl)ethyl]iminiumyl}methyl)phenolate

The title Schiff base compounds, C20H16ClNO2 (I) and C24H22N2O2 (II), were synthesized via the condensation reaction of 2-amino-4-chloro-phenol for (I), and 2-(2,3-di-hydro-1H-indol-3-yl)ethan-1-amine for (II), with 4-benz-yloxy-2-hy-droxy-benzaldehyde. In both compounds, the configuration about the C=N imine bond is E. Neither mol-ecule is planar. In (I), the central benzene ring makes dihedral angles of 49.91 (12) and 53.52 (11)° with the outer phenyl and chloro-phenyl rings, respectively. In (II), the central benzene ring makes dihedral angles of 89.59 (9) and 72.27 (7)°, respectively, with the outer phenyl ring and the mean plane of the indole ring system (r.m.s. deviation = 0.011 Å). In both compounds there is an intra-molecular hydrogen bond forming an S(6) ring motif; an O-H⋯O hydrogen bond in (I), but a charge-assisted N+-H⋯O- hydrogen bond in (II). In the crystal of (I), mol-ecules are linked by C-H⋯π inter-actions, forming slabs parallel to plane (001). In the crystal of (II), mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers. The dimers are linked by C-H⋯O hydrogen bonds, C-H⋯π inter-actions and a weak N-H⋯π inter-action, forming columns propagating along the a-axis direction. The anti-oxidant capacity of the synthesized compounds was determined by cupric reducing anti-oxidant capacity (CUPRAC) for compound (I) and by 2,2-picrylhydrazyl hydrate (DPPH) for compound (II).

Bent-core dimers with top-to-bottom linkage between central units.

A structurally new type of core-to-core dimer with a top-to-bottom linkage between the central cores of bent molecules is presented. The structure of the bent-core molecules was modified by changing the length of the spacer between the central cores and terminal chains, by changing the type of linkage groups in the bent-core arms and by variation of the terminal chain polarity – introducing polyfluoroalkyl and oligosiloxane units. Additionally, the outer phenyl ring was substituted with three alkyl chains to mimic a polycatenar system. For all compounds the mesophase behaviour and structural parameters were established to gain information about the molecular structure–mesomorphic property relationship.

Hierarchical Structures Formed by Flexible Dendrimeric Molecules Based on Gallic Acid

AbstractBehavior of first‐generation dendrons based on gallic acid is found to be strongly dependent on the number of terminal alkyl chains attached to the outer phenyl rings; only molecules having three alkyl chains per phenyl ring are mesogenic. Due to the hydrogen bonding, they form micelles that are arranged into cubic Pm3n structure. The cubic phase is also found for dimeric and trimeric gallic ester analogues; it is shown that the size of the crystallographic unit cell correlates with the isotropization temperature, apparently small micelles with high density of alkyl chains at the micelle surface interact more strongly stabilizing the cubic phase. Also behavior of gallic acid dendrons in solution is defined by the number of terminal chains, formation of either large liposomes or gel is observed.

Effects of Anthryl Groups on the Charge Transport and Photovoltaic Properties of Small Triarylamine‐Based Donor‐Acceptor Molecules: A Joint Experimental and Theoretical Study

AbstractThe effects of replacing one of the outer phenyl rings of triphenylamine by 2‐anthryl and 9‐anthryl groups of triphenylamine (TPA) have been investigated on two small push‐pull molecules consisting of a triarylamine donor block connected to a dicyanovinyl acceptor via a thienyl spacer. UV‐Vis absorption, cyclic voltammetry and theoretical calculations show that the mode of linkage of the anthryl group has a limited influence on the electronic properties of the molecule compared to reference compound based on TPA. However experimental and theoretical results show that this simple structural modification exerts a major impact on the hole‐mobility of the resulting materials and thus on their efficiency as donor in planar heterojunction solar cells.

Low-temperature nematic phase in asymmetrical 1,3,4-oxadiazole bent-core liquid crystals possessing lateral methoxy group

ABSTRACTAsymmetrical bent-core molecules based on 1,3,4-oxadiazole bent-core unit have been synthesised as a new design with a lateral methoxy group at outer phenyl ring of the molecule. These new asymmetrical bent-core molecules resemble hockey-stick shaped due to the presence of two different arms of different lengths. One arm of these molecules is elongated having two phenyl rings and possesses a 4-n-alkyloxy chain of a different number of carbon atoms (n = 4, 8, 12 and 18) and other arm is short and has one phenyl ring with fixed 4-n-octyloxy chain. The bent-core molecules possess a lateral polar methoxy group at the elongated arm of the molecule. These bent-core compounds exhibited fluorescence emission in the UV wavelength region (~377–386 nm) whereas in acetonitrile and dimethylformamide, solvent displays blue emission peak with a large stoke shift.The bent-core molecules with the number of carbon atoms (n = 4, 8 and 12) at the elongated arm exhibited monotropic nematic phase at low temperature, while the 4-n-octadecyloxy chain at the elongated arm displayed smectic A phase. Dielectric studies were performed in the nematic phase of the bent-core mesogens confirm the formation of the cybotactic cluster in the nematic mesophases.

Phenyltetrazolyl-phenylamides: Substituent impact on modulation capability and selectivity toward the efflux protein ABCG2 and investigation of interaction with the transporter

We recently presented a novel class of ABCG2 modulators based on the third-generation ABCB1 inhibitor tariquidar bearing a 2,5-linked tetrazole instead of an amid linker. We investigated the modulating potential of the compound class by enlarging the substitution pattern on the outer phenyl rings of the scaffold. To identify the structural conditions for achieving a high response, we decided to determine the individual influence of substituents on the scaffold using monosubstituted derivatives. While electron withdrawing groups (with a few exceptions) and bulky moieties decreased the modulating potency, small electron donating groups ensured a high activity level. Interestingly, the unsubstituted derivative 32 reached a similar inhibitory potential as the best derivatives in the previous study. Enzyme kinetic assays indicated that our derivatives have the same binding site as reference inhibitor Ko143. They were found to interact competitively and non-competitively with the substrates Hoechst 33342 and pheophorbide A, respectively.

Manipulation of the electronic and photovoltaic properties of materials based on small push-pull molecules by substitution of the arylamine donor block by aliphatic groups

Push-pull molecules with an arylamine donor block connected to a dicyanovinyl acceptor via a thienyl π-conjugating spacer have been synthesized in order to analyze the effects of replacing an outer phenyl ring of the triphenylamine (TPA) block of a reference compound by methyl, hexyl, heptafluoropentyl and dioxaoctyl groups. Optical, electrochemical and X-ray diffraction data show that these substitutions have minor influence on the energy levels of the molecule but exert a considerable effect on the structure, optical, electrical and photovoltaic properties of the resulting materials.

Twist effects on the electronic and photophysical characters of biphenyl and 4,4′-bis(phenylsulfonyl) biphenyl

The effect of rotation around the central C–C bond on the electronic and photophysical properties of biphenyl and 4,4′-bis(phenylsulfonyl) biphenyl is investigated theoretically using the density functional theory (DFT) method in this work. The sulfonyl groups (▪) act as effective breaking points of π-conjugation between the biphenyl core group and the outer phenyl rings. As a result, the electronic structure of these compounds are consistently observed to be very similar to these be controlled by the central moiety. Attributed to the lowered conjugation induced by twist, rotation around the single bond between two phenyl rings leads to an evolution to a more benzenoid structure for the biphenyl core. A linear relationship between the frontier MOs (HOMOs and LUMOs) energies and twisted angles of the biphenyl core in SO1 was observed. Moreover, both HOMO and LUMO are stabilized when the twisted angle is increased, and the HOMO–LUMO energy gap is enlarged. Correspondingly, the AE/VE will be increased by the rotation of the central C–C bond in biphenyl and SO1. This is confirmed by further excitation energies obtained from TD-DFT analysis based on the S0 or T1 states optimized geometries.

QENS study of molecular motions in partially deuterated liquid crystal 4BT

Molecular rotational dynamic in the crystalline and smectic E phases of selectively deuterated (in the outer phenyl ring) 4-n-butyl-isothiocyanatobiphenyl was investigated by means of quasielastic neutron scattering. The 120° reorientation of the methyl group in the crystal phase could be identified at 125 K. Additionally, ring flips were seen at 200 K. The structure of crystal and smectic E phases was obtained by X-ray measurements and the data give the identification of type of solid phases.

On substituted pyrazole derivatives. I. 3-Methyl-4-[(Z)-2-(4-methylphenyl)hydrazin-1-ylidene]-1-(3-nitrophenyl)-1H-pyrazol-5(4H)-one and 3-methyl-4-[(Z)-2-(4-methylphenyl)hydrazin-1-ylidene]-1-[4-(trifluoromethyl)phenyl]-1H-pyrazol-5(4H)-one.

The title substituted pyrazole derivatives, C17H15N5O3 and C18H15F3N4O, share most of their molecular features, in particular the hydrazinylidene (-HN-N=) rather than the diazene (-N=N-) tautomeric form, and differ only in the substituents (NO2 and CF3) on one of the outer phenyl rings. The molecular units are basically planar, with the rotation of the phenyl rings being hindered by the presence of two intramolecular hydrogen bonds having the keto O atom as acceptor. In both structures, the packing is governed by weak C-H...O, C-H...π and π-π interactions. The subtle way in which minor structural differences lead to rather different supramolecular structures is analysed.

Bent-core Mesogens Containing Amide Linking Groups

One or two amide groups were inserted as linking groups to prepare five-ring bent-core mesogens. Two isomeric series of each 8 compounds were investigated to study the influence of the position and direction of amide and ester connecting groups on the mesophase behaviour. The lateral attachment of halogen atoms to the outer phenyl rings offers a possibility to reduce the melting temperatures and to obtain materials forming mesophases in broad temperature ranges. Compounds with two amide groups show very high melting points. Shifting one of the terminal alkyloxy groups from the para into the meta position results in the loss of liquid crystalline phases. Liquid crystalline materials have been characterized by optical polarizing microscopy, DSC, X-ray diffraction measurements and electro-optical studies.