Search

Optoelectronic properties of linear π‐conjugated polymers/oligomers are of great importance for the fabrication of organic photonic and electronic devices. To this end, the π‐conjugated polymers/oligomers need to meet both optoelectronic and key structural properties in order to fulfill their implementation as active components. In particular, they need to possess low bandgap and high thermal, conformational, and photochemical stabilities. So far, several strategies have been developed to attain such requirements including the covalent and non‐covalent rigidification concepts of the π‐conjugated systems. On the basis of these findings, we describe herein the theoretical studies of novel series of covalently bridged derivatives demonstrating the benefits of the strategy. Comparison of these derivatives with compounds previously described in the literature highlights enhanced optoelectronic properties and behaviors that would be beneficial for the construction and development of new linear π‐conjugated polymers. [ABSTRACT FROM AUTHOR]

Oligo(phenyleneethynylene)s (OPEs) have attracted widespread attention due to their remarkable (opto)electronic and photophysical properties, which have enabled numerous applications. The versatile functionalization possibilities of OPEs make them unique candidates to form various shape‐persistent geometries, including linear, triangular, rectangular, hexagonal and macrocyclic. However, as a result of this structural variety, it is oftentimes challenging to correlate molecular design with self‐assembly properties. In this minireview, we have classified OPEs based on their molecular shapes and correlated them with their self‐assembly behavior in solution. Particularly, we provide important insights into the aggregation propensity of the different molecular shapes and how to tune the association strength using various non‐covalent interactions. Our classification will enable a better understanding of the structure‐property correlation in OPEs, which is key to develop supramolecular functional materials. [ABSTRACT FROM AUTHOR]

Controlling the nanoscale orientation of π‐conjugated systems remains challenging due to the complexity of multiple energy landscapes involved in the supramolecular assembly process. In this study, we have developed an effective strategy for programming the pathways of π‐conjugated supramolecular polymers, by incorporating both electron‐rich methoxy‐ or methanthiol‐benzene as donor unit and electron‐poor cyano‐vinylenes as acceptor units on the monomeric structure. It leads to the formation of parallel‐stacked supramolecular polymers as the metastable species through homomeric donor/acceptor packing, which convert to slip‐stacked supramolecular polymers as the thermodynamically stable species facilitated by heteromeric donor‐acceptor packing. By further investigating the external seed‐induced kinetic‐to‐thermodynamic transformation behaviors, our findings suggest that the donor‐acceptor functionality on the seed structure is crucial for accelerating pathway conversion. This is achieved by eliminating the initial lag phase in the supramolecular polymerization process. Overall, this study provides valuable insights into designing molecular structures that control aggregation pathways of π‐conjugated nanostructures. [ABSTRACT FROM AUTHOR]

Here we present the literary review concerning methods of synthesis and application fields of substituted quinophthalones, an interesting class of heterocyclic compounds containing fragments of substituted/unsubstituted quinolines and phthalic anhydride in their structure. Such compounds have an extended π-conjugated system and are, therefore, most often used as dyes. [ABSTRACT FROM AUTHOR]

The Knoevenagel condensation of azulenyl ketones with malononitrile resulted in the synthesis of π-conjugated 1-mono- and 1,3-bis(phenyldicyanovinyl)azulenes, and the Kumada cross-coupling reaction of bromazulenes with PhMgBr gave 1-mono- and 1,3-biphenylazulene. The electronic spectra of dicyanovinylated azulenes showed strong absorption bands of intramolecular charge transfer in the visible region, as well as significant bathochromic shifts of the absorption maxima of phenylazulenes. [ABSTRACT FROM AUTHOR]

The optoelectronic properties of π-conjugated chromophores have been widely used since the discovery of the conducting properties of synthetic organic polymers in the late 1970s [...]

The McMurry coupling is a facile, gentle and low‐cost chemical reaction for synthesizing. Here, for the first time, we employed the McMurry coupling reaction to prepare π‐conjugated anion exchange membranes (AEMs). The inter‐chain π‐π stacking between adjacent benzene rings induces directional self‐assembly aggregation and enables highly ordered ion‐conductive channels. The resulting structure was characterized through UV/VIS spectrum, X‐ray diffraction (XRD) pattern, small‐angle X‐ray scattering (SAXS), transmission electron microscopy (TEM) and density functional theory (DFT) calculations, leading to high OH− conductivity of 135.5 mS cm−1 at 80 °C. Furthermore, the double bonds in the π‐conjugated system also trigger in situ self‐crosslinking of the AEMs to enhance dimensional and alkaline stability. Benefiting from this advantage, the as‐obtained Cr‐QPPV‐2.51 AEM exhibits superior alkaline stability (95 % conductivity retention after 3000 hrs in 1 M KOH at 80 °C) and high mechanical strength of 34.8 MPa. Moreover, the fuel cell using Cr‐QPPV‐2.51 shows a maximum peak power density of 1.27 W cm−2 at 80 °C. [ABSTRACT FROM AUTHOR]

As the models for studying defected graphene, π‐conjugated systems containing heptagonal rings have attracted increasing interest due to their dynamic behaviors, electronic properties, aromaticity, and solid‐state packing. Doping heptagon‐containing π‐conjugated systems with boron not only makes π‐conjugated systems with the boron‐doped heptagonal ring have structural similarity to their all‐carbon analogues, but also could significantly change their electronic properties and intermolecular interactions. This review summarizes research on the different synthetic routes to access boron‐doped heptagons including borepins, azaborepins, and oxaborepins, with the emphasis on the structure‐property relationships at the molecular level. [ABSTRACT FROM AUTHOR]

The synthesis of some novel donor-acceptor and acceptor-donor-acceptor systems containing a 2,2′-bi[3,2-b]thienothiophene donor block and various electron-accepting units is described alongside their photophysical properties studied using electrochemistry, optical spectroscopy and theoretical calculations. The obtained results show that the energy levels can be modulated by changing the strength of the acceptor unit. Among the three investigated end-groups, 1,1-dicyanomethylene-3-indanone exhibited the largest bathochromic shift and the lowest band gap suggesting the strongest electron-withdrawing character. Moreover, the emissive properties of the investigated systems vary greatly with the nature of the terminal group and are generally lower compared to their precursor aldehyde derivatives. [ABSTRACT FROM AUTHOR]

A new type of six-armed π-conjugated structure was built up from benzene as the central core and electron-rich triazine rings as the peripheral group. The hexasubstituted product was liquid and did not exhibit any liquid crystal properties while the equimolar mixtures in 1:1 ratio of the hexasubstituted compound and 4-(dodecyloxy)benzoic acid resulted in an organic salt exhibiting a columnar mesophase characterized with a dendritic growing texture. Examination of the relationship between structure and properties and the presence of the number of carbon atoms in the alkyl chain suggested that, the higher increase led to the phase transition at low temperature to form a columnar mesophase as an ionic liquid crystal composed of cations and anions. These are often stabilized by resonance with strongly delocalized charges. The liquid crystalline properties of the organic salt were investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). [ABSTRACT FROM AUTHOR]

We reveal unique hydrogen (H‐) bonding patterns and exploit them to control the kinetics, pathways and length of supramolecular polymers (SPs). New bisamide‐containing monomers were designed to elucidate the role of competing intra‐ vs. intermolecular H‐bonding interactions on the kinetics of supramolecular polymerization (SP). Remarkably, two polymerization‐inactive metastable states were discovered. Contrary to previous examples, the commonly assumed intramolecularly H‐bonded monomer does not evolve into intermolecularly H‐bonded SPs via ring opening, but rather forms a metastable dimer. In this dimer, all H‐bonding sites are saturated, either intra‐ or intermolecularly, hampering elongation. The dimers exhibit an advantageous preorganization, which upon opening of the intramolecular portion of the H‐bonding motif facilitates SP in a consecutive process. The retardation of spontaneous self‐assembly as a result of two metastable states enables length control in SP by seed‐mediated growth. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four biphenylene-derived PAHs finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). The results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states.

The synthesis of some novel donor-acceptor and acceptor-donor-acceptor systems containing a 2,2′-bi[3,2-b]thienothiophene donor block and various electron-accepting units is described alongside their photophysical properties studied using electrochemistry, optical spectroscopy and theoretical calculations. The obtained results show that the energy levels can be modulated by changing the strength of the acceptor unit. Among the three investigated end-groups, 1,1-dicyanomethylene-3-indanone exhibited the largest bathochromic shift and the lowest band gap suggesting the strongest electron-withdrawing character. Moreover, the emissive properties of the investigated systems vary greatly with the nature of the terminal group and are generally lower compared to their precursor aldehyde derivatives.

Modulating the structure of a photocatalyst at the molecular level can improve the photocatalytic efficiency and provides a guide for the synthesis of highly qualified photocatalysts. In this study, TiO2 was modified by various organic compounds to form different TiO2-based hybrid photocatalysts. 1,10-Phenanthroline (Phen) is an organic material with delocalized π-conjugated systems. It was used to modify TiO2 to form the hybrid photocatalyst Phen/TiO2. Furthermore, 1,10-phenanthrolin-5-amine (Phen-NH2) and 1,10-phenanthroline-5-nitro (Phen-NO2) were also used to modify TiO2 to form NH2-Phen/TiO2 and NO2-Phen/TiO2, respectively. The samples of TiO2, Phen/TiO2, NO2-Phen/TiO2, and NH2-Phen/TiO2 were carefully characterized, and their photocatalytic performance was compared. The results indicated that the photocatalytic efficiency followed the order of NH2-Phen/TiO2 > NO2-Phen/TiO2 > Phen/TiO2 > TiO2. It could be found that modifying TiO2 with different organic compounds containing delocalized π-conjugated systems could enhance the photocatalytic ability; furthermore, the level of this enhancement could be modulated by different delocalized π-conjugated systems.

Azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes composed of the 1,6'-biazulene unit have been successfully prepared from corresponding Zincke salts. The synthesis of polymethines through the reaction of Zincke salts with several amines, followed by a Knoevenagel reaction with malononitrile, was accomplished in moderate to high yields (40-92 %). Meanwhile, the reaction of Zincke salts with secondary amines and the subsequent sequential condensation-cyclization with cyclopentadienide ions, so-called Ziegler-Hafner method, produced the corresponding 1,6'-biazulenes, 1,6';3,6''-terazulenes, and quinqueazulene, respectively. The structural, optical, and electrochemical properties of the azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes were revealed by single-crystal X-ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations. These results suggested that the substituents on the azulene ring and their substitution positions directly affect their reactivities, optical and electrochemical properties. [ABSTRACT FROM AUTHOR]

Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, chemists also started to exploit intricate phenomena such as the interplay of local and global (anti)aromaticity or aromaticity in non-planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here that allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. After exemplifying the method in different planar hydrocarbons, we study two non-planar macrocycles to show the unique benefits of the VIST method for molecules with competing π-conjugated systems and conclude with a norcorrole dimer showing clear evidence of through-space aromaticity. We believe that the VIST method will be a highly valuable addition to the computational toolbox. [ABSTRACT FROM AUTHOR]

Besides their widespread use in coordination chemistry, 2,2'‐bipyridines are known for their ability to undergo cis–trans conformational changes in response to metal ions and acids, which has been primarily investigated at the molecular level. However, the exploitation of such conformational switching in self‐assembly has remained unexplored. In this work, the use of 2,2'‐bipyridines as acid‐responsive conformational switches to tune supramolecular polymerization processes has been demonstrated. To achieve this goal, we have designed a bipyridine‐based linear bolaamphiphile, 1, that forms ordered supramolecular polymers in aqueous media through cooperative aromatic and hydrophobic interactions. Interestingly, addition of acid (TFA) induces the monoprotonation of the 2,2'‐bipyridine moiety, leading to a switch in the molecular conformation from a linear (trans) to a V‐shaped (cis) state. This increase in molecular distortion along with electrostatic repulsions of the positively charged bipyridine‐H+ units attenuate the aggregation tendency and induce a transformation from long fibers to shorter thinner fibers. Our findings may contribute to opening up new directions in molecular switches and stimuli‐responsive supramolecular materials. [ABSTRACT FROM AUTHOR]

Depending on the connectivity of solubilizing oligoethylene glycol (OEG) side chains to the π‐cores of amphiphilic naphthalene and perylene bisimide dyes, self‐assembly in water occurs either upon heating or cooling. Herein, we show that this effect originates from differences in the enwrapping capability of the π‐cores by the OEG chains. Rylene bisimides bearing phenyl substituents with three OEG chains attached directly to the hydrophobic π‐cores are strongly sequestered by the OEG chains. These molecules self‐assemble at elevated temperatures in an entropy‐driven process according to temperature‐ and concentration‐dependent UV/Vis spectroscopy and calorimetric dilution studies. In contrast, for rylene bisimides in which phenyl substituents with three OEG chains are attached via a methylene spacer, leading to much weaker sequestration, self‐assembly originates upon cooling in an enthalpy‐driven process. Our explanation for this controversial behavior is that the aggregation in the latter case is dictated by the release of "high energy water" from the hydrophobic π‐surfaces as well as dispersion interactions between the π‐scaffolds which drive the self‐assembly in an enthalpically driven process. In contrast, for the former case we suggest that in addition to the conventional explanation of a dehydration of hydrogen‐bonded water molecules from OEG units it is in particular the increase in conformational entropy of back‐folded OEG side chains upon aggregation that provides the pronounced gain in entropy that drives the aggregation process. Thus, our studies revealed that a subtle change in the attachment of solubilizing substituents can switch the thermodynamic signature for the self‐assembly of amphiphilic dyes in water from enthalpy‐ to entropy‐driven. [ABSTRACT FROM AUTHOR]

In recent years, pathway complexity has been studied in detail for a large variety of organic and π‐conjugated molecules. However, such investigations on their metal‐containing analogues have received only little attention to date, despite the well‐known potential of metal complexes in various fields. In this Minireview, we have collected recent examples of d8 metal complexes (Pt(II), Pd(II) and Au(III) complexes) exhibiting controlled supramolecular polymerization through pathway complexity and seeded‐growth approaches. Controlling the competing thermodynamic vs. kinetic pathways in these systems should help develop advanced metallosupramolecular functional materials with excellent photophysical, electronic, magnetic, catalytic, and biomedical applications. [ABSTRACT FROM AUTHOR]

Angle‐strained alkyne‐containing π‐conjugated macrocycles are attractive compounds both in functional materials chemistry and biochemistry. Their interesting reactivity as well as photophysical and supramolecular properties have been revealed in the past three decades. This review highlights the recent advances in angle‐strained alkyne‐containing π‐conjugated macrocycles, especially their synthetic methods, the bond angles of alkynes (∠sp at C≡C−C), and their functions. The theoretical and experimental research on cyclo[n]carbons and para‐cyclophynes consisting of ethynylenes and para‐phenylenes are mainly summarized. Related macrocycles bearing other linkers, such as ortho‐phenylenes, meta‐phenylenes, heteroaromatics, biphenyls, extended aromatics, are also overviewed. Bond angles of strained alkynes in π‐conjugated macrocycles, which are generable, detectable, and isolable, are summarized at the end of this review. [ABSTRACT FROM AUTHOR]

In order to understand the electronic contribution of the thienopyrazine building block on the electronic properties of π-conjugated systems, small molecules containing thiophene and thienopyrazine moieties are synthesized and jointly studied by theoretical (DFT) and experimental methods (UV-Vis, UPS). Taking advantages of these preliminar attractive results, four low band gap extended structures have been elaborated on the base of Donor-Acceptor-Donor sequences (DAD); these elongated π-conjugated molecules exhibit noticeable electronic and absorption properties spreading from the near UV to NIR regions. [ABSTRACT FROM AUTHOR]

This document discusses the synthesis and potential applications of heteracyclo[n]phanes, which are cyclic structures derived from π-conjugated chromophores. These structures have been widely used in various fields such as batteries, sensors, and photovoltaic cells due to their electrical properties. The document highlights a recent strategy for achieving cyclic derivatives of these structures, which could expand their potential for use as metal-gas sequestering agents and sensing materials. The authors also mention ongoing research in identifying nanoarchitectures for integration into devices like sensors. [Extracted from the article]

Supramolecular gels containing porphyrins and phthalocyanines motifs are attracting increased interests in a wide range of research areas. Based on the supramolecular gels systems, porphyrin or phthalocyanines can form assemblies with plentiful nanostructures, dynamic, and stimuli-responsive properties. And these π-conjugated molecular building blocks also afford supramolecular gels with many new features, depending on their photochemical and electrochemical characteristics. As one of the most characteristic models, the supramolecular chirality of these soft matters was investigated. Notably, the application of supramolecular gels containing porphyrins and phthalocyanines has been developed in the field of catalysis, molecular sensing, biological imaging, drug delivery and photodynamic therapy. And some photoelectric devices were also fabricated depending on the gelation of porphyrins or phthalocyanines. This paper presents an overview of the progress achieved in this issue along with some perspectives for further advances.

We exploited the inherent geometrical isomerism of a PtII complex as a new tool to control supramolecular assembly processes. UV irradiation and careful selection of solvent, temperature, and concentration leads to tunable coordination isomerism, which in turn allows fully reversible switching between two distinct aggregate species (1D fibers↔2D lamellae) with different photoresponsive behavior. Our findings not only broaden the scope of coordination isomerism, but also open up exciting possibilities for the development of novel stimuli‐responsive nanomaterials. [ABSTRACT FROM AUTHOR]

A series of molecules in which 9H‐carbazole (electron donor, D) and 2,2′:6′,2′′‐terpyridine (electron acceptor, A) are connected through rigid π‐conjugated bridges (D‐π‐A systems) have been synthesized and their photophysical properties examined in detail, with the support of DFT calculations. The bridges are made of different sequences of ethynylene, phenylene, and anthracene groups. The synthetic strategies involve condensation of 2‐acetylpyridine with the aromatic aldehyde moiety on different functionalized π‐conjugated bridges and couplings with carbazole derivatives. The system incorporating anthracene in the bridge shows the typical absorption and emission fingerprints of this polycyclic hydrocarbon. The other systems have HOMOs and LUMOs centred, respectively, over the carbazole and the bridge and exhibit solvatochromic charge‐transfer (CT) luminescence with high photoluminescence yield up to 70 %, except when an ethynylene unit is directly attached to the carbazole ring, due to a trans‐bent non‐emissive π–σ* excited state. [ABSTRACT FROM AUTHOR]

Controlling the nanoscale morphology in assemblies of π‐conjugated molecules is key to developing supramolecular functional materials. Here, we report an unsymmetrically substituted amphiphilic PtII complex 1 that shows unique self‐assembly behavior in nonpolar media, providing two competing anti‐cooperative and cooperative pathways with distinct molecular arrangement (long‐ vs. medium‐slipped, respectively) and nanoscale morphology (discs vs. fibers, respectively). With a thermodynamic model, we unravel the competition between the anti‐cooperative and cooperative pathways: buffering of monomers into small‐sized, anti‐cooperative species affects the formation of elongated assemblies, which might open up new strategies for pathway control in self‐assembly. Our findings reveal that side‐chain immiscibility is an efficient method to control anti‐cooperative assemblies and pathway complexity in general. [ABSTRACT FROM AUTHOR]

The supramolecular polymerization of an acid‐sensitive pyridyl‐based ligand (L1) bearing a photoresponsive azobenzene moiety was elucidated by mechanistic studies. Addition of trifluoroacetic acid (TFA) led to the transformation of the antiparallel H‐bonded fibers of L1 in methylcyclohexane into superhelical braid‐like fibers stabilized by H‐bonding of parallel‐stacked monomer units. Interestingly, L1 dimers held together by unconventional pyridine–TFA N⋅⋅⋅H⋅⋅⋅O bridges represent the main structural elements of the assembly. UV‐light irradiation caused a strain‐driven disassembly and subsequent aggregate reconstruction, which ultimately led to short fibers. The results allowed to understand the mechanism of mutual influence of acid and light stimuli on supramolecular polymerization processes, thus opening up new possibilities to design advanced stimuli‐triggered supramolecular systems. [ABSTRACT FROM AUTHOR]

Statistical copolymerization plays a key role in many biological and technological processes; however, mechanistic understanding of the formation of analogous supramolecular counterparts remains limited. Herein, we report detailed insights into the supramolecular co‐assembly of two π‐conjugated PdII and PtII complexes, which in isolation self‐assemble into flexible fibers and nanodisks, respectively. An efficient single‐step co‐assembly into only one type of nanostructure (fibers or nanodisks) takes place if any of the components is in excess. In contrast, equimolar mixtures lead to PdII‐rich fiber‐like co‐assemblies by a statistical co‐nucleation event along with a residual amount of self‐sorted nanodisks in a stepwise manner. [ABSTRACT FROM AUTHOR]

Abstract Pyrimidine N -oxide moiety for the first time was used as a heterocyclic core for the construction of π-conjugated molecules with fluorescent properties. For the synthesis of the title compounds a simple two-step protocol starting from readily available 4-fluoro-2-methylpyrimidine N -oxides was elaborated. A series of 17 novel pyrimidine N -oxide derivatives containing various functional substituents and π-conjugated systems of different length were obtained. The title compounds revealed fluorescent properties in visible region, possessing emission maximum up to 575 nm. Deoxygenation of the N -oxide group led to the loss of visible fluorescence. The chemosensor properties towards TFA and a number of metal cations were demonstrated for 3a , the first representative of the title series. Cytotoxic activity against breast adenocarcinoma cell line was found for three pyrimidine N -oxide derivatives 3b,i,n. Pyrimidine N -oxide 3a was shown to possess excellent biocompatibility and capability to enter cells, that makes it a promising structure for development of bioimaging fluorescent probes. Highlights • The first series of π-conjugated systems based on pyrimidine N -oxide was obtained. • The title compounds display fluorescence in visible region and chemosensor properties. • Pyrimidine N -oxide 3a is non-toxic and readily accumulates in cells. • Three pyrimidine N -oxides display cytotoxicity against human cancer cells. [ABSTRACT FROM AUTHOR]

Azobenzene and its derivatives are widely used as photoresponsive units for the fabrication of photoresponsive smart materials. In this work, two azobenzene derivatives were designed and investigated as hydrogelators, namely N‐4‐azodiphenyl‐maleimic acid (ADPMA) and N‐4‐azodiphenyl‐succinic acid (ADPSA) bearing azobenzene and carboxylic acid segments. In the process of deprotonation/protonation of the carboxylic acids by pH variation, the self‐assembly of these two gelators was triggered. ADPMA could transform from solution to hydrogel while the solution of ADPSA formed a precipitate under the same conditions. The solution‐gel/precipitate transformation can be repeated by changing the pH. In contrast to the conventional responsiveness to UV‐light irradiation for azobenzene‐based gels, the ADPMA hydrogel shows typical trans‐cis isomerization of the azobenzene unit in solution, yet the hydrogel demonstrates remarkable stability to UV light irradiation in both the bulk gel and thin film states. [ABSTRACT FROM AUTHOR]

Cooperative π–π interactions and H‐bonding are frequently exploited in supramolecular polymerization; however, close scrutiny of their mutual interplay has been largely unexplored. Herein, we compare the self‐assembly behavior of a series of C2‐ and C3‐symmetrical oligophenyleneethynylenes differing in their amide topology (N‐ or C‐centered). This subtle structural modification brings about drastic changes in their photophysical and supramolecular properties, highlighting the reciprocal impact of H‐bonding vs. preorganization on the evolution and final outcome of supramolecular systems. To match or not to match: Detailed self‐assembly studies of a series of C2‐ and C3‐symmetrical π‐systems that differ in the amide connectivity (N‐ vs. C‐centered) were used to examine the reciprocal impact of H‐bonding and preorganization on the evolution of self‐assembled structures. [ABSTRACT FROM AUTHOR]

π-Conjugated molecules are the active materials in organic electronics, yet the range of available materials is limited by the nontrivial, multistep synthetic process required to obtain long π-conjugated backbones. Here, Diels–Alder cycloaddition and its reactivity and selectivity are evaluated as a means for obtaining long, novel, π-conjugated backbones. Particular attention is paid to the Diels–Alder conjugation products of furans, such as selectively substituted arenes and, potentially, carbon nanoribbons. [ABSTRACT FROM AUTHOR]

Abstract: The self‐assembly features of hydrophobic bispyridyldichlorido Pd(II) complexes, equipped with an extended aromatic surface derived from oligophenyleneethynylene (OPE) and polarizable amide functional groups, are reported. The cooperative supramolecular polymerization of these complexes results in bundles of thin fibers in which the monomer units are arranged in a translationally displaced or slipped fashion. Spectroscopic and microscopy studies reveal that these assemblies are held together by simultaneous π‐stacking of the OPE moieties and NH···ClPd hydrogen bonds. These unconventional forces are often observed in crystal engineering but remain largely unexploited in supramolecular polymers. Both steric and electronic effects (the presence of bulky and polarizable metal‐bound Cl ligands as well as hydrogen bonding donor NH units) prevent the establishment of short Pd–Pd contacts and strongly condition the aggregation mode of the reported complexes, in close analogy to the previously reported amphiphilic Pd(II) complex 4. The results presented herein shed light on the subtle interplay between different noncovalent interactions and their impact on the self‐assembly of metallosupramolecular systems. [ABSTRACT FROM AUTHOR]

Abstract: A dithieno[a,h]‐s‐indacene‐ (DTI‐) based diradicaloid DTI‐2Br was synthesized and its open‐shell singlet diradical character was validated by magnetic measurements. On the other hand, its macrocyclic trimer DTI‐MC3 and tetramer DTI‐MC4 turned out to be closed‐shell compounds with global antiaromaticity, which was supported by X‐ray crystallographic analysis and NMR spectroscopy, assisted by ACID and 2D‐ICSS calculations. Such change can be explained by a subtle balance between two types of antiferromagnetic spin–spin coupling along the π‐conjugated macrocycles. The dications of DTI‐MC3 and DTI‐MC4 turned out to be open‐shell singlet diradical dications, with a singlet–triplet energy gap of −2.90 and −2.60 kcal mol−1, respectively. At the same time, they are both global aromatic. Our studies show that intramolecular spin–spin interactions play important roles on electronic properties of π‐conjugated macrocycles. [ABSTRACT FROM AUTHOR]

A synthetic route to novel benzofuran fused silole derivatives is described and the new compounds were fully characterized. These compounds showed optical and electrochemical properties that differ from their benzothiophene analog. Preliminary results show that these derivatives can be used as blue emitters in organic light emitting devices (OLEDs) illustrating the potential of these new compounds for opto-electronic applications. [ABSTRACT FROM AUTHOR]

Theoretical investigation of linear and nonlinear optical (NLO) properties in simple complexes consist of alkali metals and π-conjugated systems have been studied at MP2/6-311++G(2d,2p) computational level. Lithium, sodium, and potassium as alkali metals were chosen for interaction with some non-aromatic, aromatic and anti-aromatic systems. For better comparison of results, the π-systems were chosen with the same carbon number: butadiene as a non-aromatic in comparison with cyclobutadiene as an anti-aromatic and hexatriene as a non-aromatic in comparison with benzene as an aromatic system. Results revealed that gap energy of studied π-systems was decreased under the interacting with alkali metals. Furthermore all designed complexes were shown very good results in average polarizability (α) and first hyperpolarizability (β0) parameters. So these very simple dimer complexes could be introduced as promising innovative nonlinear optical materials. [ABSTRACT FROM AUTHOR]

Sensors have attracted particular attention as analytical devices because of their importance in health and security. The ability to obtain unique functions using molecular design have rapidly advanced the use of organic optoelectronic materials of π-conjugated compounds in electronic sensing devices. A brief introduction to sensors, focusing on organic micro- or nanoassemblies created using state-of-the-art protocols for assembly and their recent development for high-performance electronic sensing devices, is presented. [ABSTRACT FROM AUTHOR]

Borinium ions, that is, two-coordinate boron cations, are the most electron-deficient isolable boron compounds. As borinium ions have only four formal valence electrons on boron, they should show a strong tendency to accept electron pairs on the boron atom to fill its valence shell. Thus chemical reactions of borinium ions are expected to give products in which the coordination number of boron is increased from two to three or four. However, contrary to this expectation, we found that the dimesitylborinium ion (Mes2B+) undergoes twofold 1,2-carboboration reactions with two equivalents of diphenylacetylene to yield an unprecedented borinium ion ( 1+) with two substituted vinyl groups on the boron center. NMR spectroscopy and X-ray diffraction analysis of 1+, together with electronic-structure calculations, revealed that the positive charge is delocalized over the entire π-conjugated system. The fact that the chemical transformation of a borinium ion gives rise to a different borinium ion without a change in the coordination number is remarkable and should provide new insight into the chemistry of the Group 13 elements. [ABSTRACT FROM AUTHOR]

Two examples of bis 3,4-dialkoxythiophenes linked with a m -xylene bridge were synthesized in yields of 18% and 32% in a six step process. The formation of the m -xylene bridge, key reaction of the synthesis, was carried out through Williamson, Mitsunobu and trans -etherification reactions which were subsequently compared on performance and versatility. The Mitsunobu reaction assisted by sonication was found to be the best strategy. These molecules are among the few examples of unsymmetrically substituted 3,4-dialcoxythiophenes. During the synthesis an 18 member heterocycle, closely related to a crown ether was isolated. The details of the XRD structure of this heterocycle are discussed. [ABSTRACT FROM AUTHOR]

A series of thienylpyrroles and bithienylpyrroles together with their formyl derivatives 5a – d were synthesized using commercially or readily available coupling components, through three different palladium catalyzed cross-coupling reactions (Suzuki-Miyaura, Stille and decarboxylative coupling). The synthesis of compounds 5 via the Suzuki-Miyaura reaction produced the title compounds in better yields than the other coupling reactions, while, decarboxylative coupling resulted in the lower yields. UV–visible and 1 H NMR studies confirm the existence of significant intramolecular charge transfer (ICT) from the donor pyrrole heterocycle to the acceptor group and a high polarizability of the whole π-conjugated systems. Together these characteristics indicate their strong potential as versatile precursors for the preparation of push-pull heterocyclic compounds for optical applications. [ABSTRACT FROM AUTHOR]

Different D–π–A push–pull molecules in which dipicolylamine (DPA) is used as the donor group, different diazines as the acceptor groups, and styryl as the π-conjugated spacer have been synthesized in a straightforward manner by aldol condensation of 4-(di-2-picolylamino)benzaldehyde and the appropriate methyldiazine. All of the compounds showed π–π* transitions in the UV or visible region and the emission of yellow-green light upon irradiation. Significant red shifts were observed in the fluorescence emission maxima of these compounds on increasing the solvent polarity, a finding that suggests the formation of an intramolecular charge-separated emitting state that is also supported by semi-empirical calculations. In some cases, protonation led to marked color changes, thus showing the ability of these molecules to function as colorimetric pH sensors. The DPA and diazine units can act as coordination sites for metal cations such as Zn 2+ , Cd 2+ or Hg 2+ , leading to a blue or red shift in the fluorescence spectra due to the change in the intramolecular charge transfer properties. This phenomenon could become a powerful tool for the creation of multiple emission colors with a single molecule after suitable design. [ABSTRACT FROM AUTHOR]

In this paper, we present the development of white OLEDs (WOLEDs) using organophosphorus derivatives as fluorescent emitters. The structural changes that we have performed on and around the phosphole ring (functionalization of the phosphorus atom, nature of the substituents at the 2 and 5 position) allow the ability to tune the emission wavelengths and the color emitted by the OLEDs. Using this concept, we developed organophosphorus dopants emitting orange light, which can be mixed with a blue-emitting matrix for the development of WOLEDs. The OLEDs structure allows the development of flexible OLEDs with good performance and CIE coordinates which are independent from the current density. [ABSTRACT FROM PUBLISHER]

We report an innovative template-assisted synthetic protocol for the selective functionalization of terminal triple bonds in oligophenyleneethynylenes (OPE) by pre-organization in aqueous solution. By this approach, three new OPE-based bolaamphiphiles substituted with hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) chains of different length have been synthesized. The chain length was observed to strongly influence the aqueous supramolecular polymerization: bolaamphiphiles with longer hydrophilic chains aggregate into spherical nanoparticles in a stepwise fashion, whereas 2D anisotropic platelets are formed cooperatively if shorter PEtOx chains are used. Our results demonstrate that hydrophobic interactions can be strong enough to trigger cooperative effects in aqueous self-assembly processes. [ABSTRACT FROM AUTHOR]