Facile synthesis of 5,10,15-hexaaryl truxenes: structure and properties

A new synthesis of 5,10,15-hexaaryltruxene derivatives has been developed. Experimental observations and theoretical calculations confirmed that the presence of aryl substituents on the sp(3)-hybridized bridge carbon atoms had an effect on the photophysical properties of the truxene core. Interestingly, the cage compound 11 possessing a distorted truxene core was verified by X-ray diffraction analysis; the influence of the peripheral aryl substituents on the photophysical properties of the truxene core was diminished because of its molecular rigidity.     

Combined QSAR/QSPR,Molecular Docking,and Molecular Dynamics Study of Environmentally Friendly PBDEs with Improved Insulating Properties

To improve the insulating properties of polybrominated diphenyl ethers(PBDEs), we studied the molecular structures and energy gap(Eg) values of 209 PBDEs using a three-dimensional quantitative structure-activity relationship(3D-QSAR) model, molecular docking, and molecular dynamics. We also analyzed the interaction mechanisms of PBDEs using a 2D-QSAR model, molecular substitution characteristics, and molecular docking. The 3D-QSAR model showed that the 2-, 4-, 5-, and 6-positions significantly influenced the PBDE insulating properties. Using BDE-34 as a template molecule, we designed six derivatives with 0.47%-28.44% higher insulation tlian BDE-34. Compared with BDE-34, the stability and flame retardancy of the above six derivatives were not adversely affected. These derivatives, except for 2,6-cyanomethyl-BDE, 2-cyanomethyl-BDE, and 2-aniinomethyl-BDE, were more toxic and biodegradable than BDE-34, but showed weaker bioaccumulation and migration abilities than BDE-34. Mechanism analysis showed that the highest occupied orbital energy, the most negative charge, and the dipole moment were the main quantitative parameters that aflected the PBDE insulating properties. PBDE insulation gradually decreased as the number of Br atoms increased. The level of similarity between the substitution patterns on the two benzene rings was significantly correlated with PBDE insulation, with hydrophobic groups having a more significant efiect on PBDE insulation.     

Tuning the Optical Properties of Sulfonylaniline Derivatives: Degeneracy Breaking of Benzene Orbitals and Linkage through Nodal Planes

The orbital degeneracy of benzene rings is resolved by an asymmetric push-pull system in 2,6-bis(methylsulfonyl)aniline (BMeSA), in which the highest occupied molecular orbital (HOMO) is located at the 4-position, while the lowest unoccupied molecular orbital (LUMO) is located at a different position and has a nodal plane through the carbon atoms at the 1- and 4-positions. Therefore, the π-extension of BMeSA at the 4-position reveals a strong overlap in the HOMO and a minimal overlap in the LUMO. Consequently, π-extended BMeSA derivatives exhibit longer absorbance and emission wavelengths in the order of the electron-donating abilities of their substituents at the 4-position, which is based on a decrease in an absolute HOMO-level-dependent HOMO-LUMO gap in accordance with the nodal arrangement. Positive fluorescent solvatochromism with polarity-dependent decrease in fluorescent intensity was also observed. The biaryls exhibited more planar geometries in the excited state than in the ground state. The charge transfer mechanism, which can be described as node-induced intramolecular charge transfer (NICT), differs from the planar intramolecular charge transfer (PICT) and twisted intramolecular charge transfer (TICT).     

Molecular dipoles at substrate/film interfaces influencing surface energy of Langmuir-Blodgett films

Langmuir and Langmuir-Blodgett (LB) films of novel rigid Schiff base amphiphiles with different polar groups on aromatic rings have been studied at air/water interfaces and on solid substrates. The local surface potentials for the different substituents on the aromatic groups of the amphiphiles are correlated to the surface energy of LB films on solid substrates. Their contributions are probed on high-surface-energy (hsfe) quartz and hydrophobically modified low-surface-energy (lsfe) quartz. Using theoretical estimates, the long-range effects of the substituents of the polar groups on the alkyl chains have been studied from charge on the carbon and hydrogen atoms of the alkyl tails. The calculations indicate that a substituted carbon atom has a charge that is directly dependent on the nature of the atoms to which it is attached rather than on the charges of any other atoms of the substituents. This work shows that the polar substituents on the head group clearly influence the distal methylene groups of the tail. Thus, any treatment, either theoretical or experimental, of these films in contact with solid substrates should include the local relative permitivities of the polar moieties, which seem to play an important role in determining macroscopic properties such as surface energy.     

Truxene‐Based Columnar Liquid Crystals: Self‐Assembled Structures and Electro‐Active Properties

Columnar liquid‐crystalline (LC) truxene derivatives containing branched flexible alkyl chains have been designed and synthesized. The dicyanomethylene and dithiafulvene substituents have been introduced into the π‐conjugated truxene framework to tune their electronic and redox properties as well as the molecular assembled structures. The π‐conjugated cores of dicyanomethylene‐ and dithiafulvene‐appended truxenes adopt bowl‐shaped conformations, giving rise to a large intrinsic dipole moment perpendicular to the aromatic framework. These molecules form stable columnar LC structures through intermolecular dipole–dipole interactions. The redox properties of LC truxene derivatives have been examined by cyclic voltammetry. The dicyanomethylene‐appended truxene shows the reversible four‐step electrochemical reductions, whereas the dithiafulvene‐appended truxene undergoes three‐step oxidations.     

Synthesis, crystal structures, and properties of 6,12-diaryl-substituted indeno[1,2-b]fluorenes

Fused polycyclic indeno[1,2-b]fluorene derivatives with aryl substituents at the 6,12-positions have been prepared as a potential antiaromatic 20π electronic system. They showed strong absorptions in the visible region and amphoteric redox properties. The quinoid-type molecular structures were revealed by X-ray crystal-structure analysis, which indicated that the bond lengths of the quinoid unit depend on the aryl substituents. Whereas nucleus-independent chemical shift NICS(1) calculations indicate the antiaromatic nature of the s-indacene core, they have higher stability than substituted acene derivatives. The derivatives with difluorophenyl or anthryl groups were stable in solution. Vapor-deposited thin films showed ambipolar carrier transportation in the field-effect transistor devices.     

具有扭曲的分子内电荷转移的芳香酮衍生物的结构与光谱性能研究

设计合成了一系列基于芳香酮的具有分子内扭曲态电荷转移(TICT)特性的化合物,通过线性光物理性质与双光子吸收性质的表征,研究了分子结构中不同共轭基团和不同取代基位置对化合物光谱性能的影响,同时通过溶剂效应研究了化合物的分子内电荷转移性质。结合理论计算结果表明分子的共轭骨架和取代基的位置都能显著影响分子内电荷转移特征。其中芴酮系列的化合物表现出了较强的双光子吸收与聚集诱导荧光增强效应,在生物荧光成像领域有着潜在的应用价值。     

Synthesis and spectral properties of autocomplexes of the nitroquinoline series

A number of new NH-bridged nitroquinoline derivatives with intramolecular charge transfer (autocomplexes) were synthesized starting from 8-chloro-5,7-dinitroquinoline and aromatic N,O-heterocyclic amines characterized by different donor powers and substitution patterns. The charge transfer in their molecules may occur via both direct polar conjugation through the bond sequence including the bridging nitrogen atom and through space between spatially close molecular fragments (contact charge transfer).     

Effect of Alkyl,Aryl, and <Emphasis Type="Italic">meso</Emphasis>-Aza Substitution on the Thermal Stability of BODIPY

The effect of peripheral alkyl, aryl, and meso-aza substitution on the thermal stability of BODIPYs in an argon or oxygen atmosphere has been analyzed using thermogravimetric study results. It has been shown that an increase in the length of 2,6-alkyl substituents to seven carbon atoms is accompanied by the growth of BODIPY thermal stability by 80°C. The greatest increase in the destruction temperature of BODIPY (by 100°C) is attained via the introduction of phenyl groups in the 1,3,5,7-positions of its dipyrromethenmethene framework. meso-Aza substitution does not almost produce any effect on the thermal stability of BODIPY dyes. The BODIPY destruction beginning temperature decreases by 60–90°C in the presence of air oxygen. The thermal stability of BODIPY tends to decrease with reducing degree and symmetry of alkyl substitution in the dipyrromethene framework. A lower thermal stability of BODIPY in comparison with zinc(II) dipyrromethenates is due to the participation of fluorine atoms in intramolecular redox processes.     

Spectrographie de masse en série du bornane I: Bornanes monosubstitués

A study has been made of the fragmentation of 2- and 3-monosubstituted bornanes. Ketones, oximes, alcohols, amines and their N-methyl derivatives were examined. Different fragmentations were compared according to the 2- or 3-position of the substituents. The results show the importance of cleavage α to the substituent bearing the charge. The α bond cleaved is that bond directed to the carbon atom with the greater degree of substitution. These results allow one to differentiate, by mass spectroscopy, the 2- and the 3-positions in the bornane skeleton.     

Synthesis and properties of a fluorene-capped isotruxene: a new unsymmetrical star-shaped pi-system

An unsymmetrical star-shaped pi-system (1) with an isotruxene core and three fluorene arms has been synthesized, and its photophysical, electrochemical, and thermochemical properties have been investigated and compared with the corresponding symmetrical truxene derivatives 2a-d (Kanibolotsky, A. L.; Berridge, R.; Skabara, P. J.; Perepichka, I. F.; Bradley, D. D. C.; Koeberg, M. J. Am. Chem. Soc. 2004, 126, 13695-13702). Stronger electronic couplings between the arms in 1 vs 2a-d lead to lower optical band gap, larger splitting in oxidation potentials, and superior thermostability. [structure: see text]     

Carbon-13 NMR spectra of DDT,its analogues and related compounds

Carbon-13 NMR spectra of mono- and disubstituted aromatic compounds including DDT, its analogues, homologues, derivatives and certain model compounds have been studied. The Savitsky scheme of carbon chemical shifts in disubstituted benzenes is applicable to these compounds. The data obtained show that in mono- and disubstituted aromatic compounds containing two different substituents in the α- and β-positions of the side chain, the substituted ring carbon atom shifts follow the additivity rule and can be calculated from substituent increments. Mutual effects of substituents in the ring and in the side chains are analysed. The chlorine atoms in α-position to the phenyl ring give rise to an additive α-effect of about 25 ppm, as in perchloroalkanes. The influence of a β-chlorine atom in the side chain on the substituted carbon atom in the ring is, however, only 3 ppm as against the usual value of about 10 ppm for the β-effect in alkyl chains. Moreover, the first β-chlorine substituent has no noticeable influence on the substituted ring carbon chemical shift: the effect of 3 ppm is transferred to the para-carbon atom almost without attenuation. The ring substituted carbon atom signal shifts caused by the γ-effect of chlorine in the side chain are similar to those observed in aliphatic chains. The ortho-chlorine substituents shift the side chain α-carbon atom signal by 3.6-5.2 ppm to high field compared to para-chlorophenyl compounds. This is similar to the chlorine γ-effect in aliphatic chains.     

Diiodinated Mono- and Dipyridylvinyl BODIPY Dyes: Photophysicochemical Properties,in vitro Antibacterial Studies,Molecular Docking and Theoretical Calculations

In this study, novel mono- and dipyridylvinyl boron dipyrromethene dyes are prepared to compare their photodynamic antimicrobial chemotherapy (PACT) activities against Staphylococcus aureus to the corresponding core dyes. Pyridylvinyl substitution at the 3- or 3,5-positions of a meso-4-bromophenylBODIPY core dye via a Knoevenagel reaction with an aromatic 2-bromopyridinecarboxaldehyde shifts the major BODIPY spectral band to longer wavelength. The extended π-conjugation red shifts the main spectral band into the 602–618 nm region in CHCl₃, THF, ethanol and DMSO after monopyridylvinyl substitution and to 685–704 nm after dipyridylvinyl substitution. An enhancement of the population of the T₁ state through the incorporation of iodine atoms at the 2,6-positions results in moderately high singlet oxygen quantum yields in DMSO. The π-extended dyes were found to have significantly lower PACT activities than the diiodinated core dye.     

A simple, modular method for the synthesis of 3,4,5-trisubstituted pyrazoles

A modular approach for the regiocontrolled preparation of pyrazoles bearing substituents on all three carbon atoms is described. Central to this method is the use of a switchable metal-directing group (MDG) to enable sequential direct lithiation of the 3- and 5-positions of the pyrazole ring. Pyrazole boronic esters obtained from these lithiated intermediates can undergo efficient Suzuki cross-coupling under the developed nonaqueous conditions, which minimize undesirable protolytic deboronation. Halogenation of the 4-position provides the means for substitution at the remaining carbon atom.     

Molecular structures of amino and nitro derivatives of 1,3-di(morpholin-4-yl)benzene

The 4,6-diamino-1,3-di(morpholin-4-yl)- and 5-amino-2,4-di(morpholin-4-yl)-1-nitro derivatives of benzene, which serve as model compounds in studies of spatial structures and reactivities of monomer units of many polymers of practical importance, have been studied by X-ray diffraction analysis. The morpholine rings are twisted so that they are virtually perpendicular to the benzene ring. According to the results of AM1 calculations, the hydrogen atoms of the methylene groups of these substituents carry noticeable positive charges. The introduction of different substituents into the benzene ring has no substantial effect on the charge distribution in the morpholine rings due to the absence of conjugation between the lone electron pairs of the nitrogen atoms of the ring and the π-system of the benzene ring. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 444–449, March, 1998.     

Molecular structures and reactivities of 1,3-diphthalimidobenzene derivatives

X-ray diffraction analysis of 4,6-di(morpholin-4-yl) and 4,6-di(2,2,2-trifluoroethoxy) derivatives of 1,3-diphthalimidobenzene, which are potent reagents in the synthesis of heterocyclic polymers, was carried out. The conjugation between the π-systems of the benzene ring and of the phthalimide and morpholine substituents is distorted due to the rotation of the substituents about the C(Ar)−N bonds. The AMI calculations demonstrated that the hydrogen atoms of the methylene groups are “acidic”, which is favorable for condensation reactions. Steric hindrances to intramolecular condensation were estimated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1155–1161, June, 1998.     

Theoretical study on the intramolecular hydrogen bond in chloro-substituted N,N-dimethylaminomethylphenols. I. Structural effects

Ab initio and density functional calculations are applied to study the influence of an increasing number of chlorine substituents on the properties of the intramolecular hydrogen bond in substituted Mannich bases. It is shown, that not only the acidity of the proton donor, which depends on the number of chlorine atoms at the aromatic ring, but also steric interactions modify the geometry of the hydrogen bond. Specific interactions of O–ClH–O hydrogen-bonding in some derivatives are estimated by calculations on related chlorophenols.     

In search of oligo(2-thienyl)-substituted pyridine derivatives: a modular approach to di-, tri- and tetra(2-thienyl)pyridines

Herein, we describe our attempts to systematically prepare a series of oligo(2-thienyl)-substituted pyridine derivatives. The crucial starting material, a β-alkoxy-β-ketoenamide, is easily available on a large scale by the reaction of lithiated methoxyallene with thiophene-2-carbonitrile and thiophene-2-carboxylic acid. This three-component reaction is followed by intramolecular cyclization to yield the suitably functionalized 2,6-di(2-thienyl)-substituted pyridine derivates. The two oxygen atoms allow the programmed activation of positions C-3, C-4, or C-5 of the pyridine ring to perform palladium-catalyzed coupling reactions with thiophene-2-boronic acid or 2-(tributylstannyl)thiophene, and alternatively, reductive removal of groups. With this concept, we were able to prepare five pyridine derivatives with 2-thienyl substituents in the 2,6-, 2,3,6-, 2,4,6-, 2,3,4,6-, and 2,3,5,6-positions. 2,3,4,5,6-Penta(2-thienyl)pyridine was not available with our methods. The UV/Vis and fluorescence spectra of all pyridines were recorded and showed a dependence on the substitution pattern and protonation state. For the protonated 2,3,5,6-tetra(2-thienyl)-substituted pyridine, a Stokes shift of about 180 nm with an emission at 515 nm was observed.     

Synthesis and mesomorphic properties of four ring,rod-like fluorene derivatives – the influence of the lateral substitution on mesomorphic properties of 2,7-bis(4-alkylphenyl)-fluorenes

ABSTRACT

This work presents new rod-like compounds being fluorene derivatives linked with other parts of the core at 2 and 7 positions – its synthesis and properties. The fluorene moiety is located in the central position of the four rings molecular core. The chain system in most cases was symmetrical and limited to pentyl or hexyl chains. To study the influence of the lateral substituents on mesomorphic properties two types of substituents have been incorporated, centrally located various short alkyl groups at fluorene’s 9,9 positions and outer core fluorosubstitutions located at side phenyl rings. All synthesised compounds exhibit liquid crystalline properties, where for laterally non-substituted and fluorosubstituted derivatives the dominant phases are smectics, while the nematics phases (nematic and chiral nematic – observed mostly on cooling cycle) occurs for compounds having alkyl substituents at 9,9 positions of fluorene. The synthetic methodology and mesomorphic properties of title compounds will be presented in detail as well as photophysical properties such as UV-visible absorption spectra and fluorescence spectra.     

Intramolecular thermal transformations of N-phthalimidoaziridines: 1,3-dipolar cyclo-addition and rearrangements*

The intramolecular thermal cycloaddition of N-phthalimidoaziridines at multiple bonds of substituents with the intermediate formation of azomethine ylides leads to condensed pyrrole derivatives, in which the five-membered ring is adjacent to a five-, six-, or seven-membered ring. Rearrangements, which sometimes become the predominant reactions, compete with cycloaddition. Thus, aziridines with aryl substituents readily isomerize to give imines with a 1,2-shift of the phthalimide group to one of the carbon atoms. Aziridines with one electron-withdrawing substituent probably do not open to give 1,3-dipoles but rather undergo a Cope-type rearrangement involving the three-membered ring and C = O bond of the second substituent. Even in intramolecular reactions, very low activity is found for the cyano group triple bond and aromatic ring bonds as dipolarophiles.