Π-conjugated Organic Compounds Research Articles

Intermolecular π-π stacking of oligomeric naphthalene cathodes facilitate high performance aluminum ion battery

Π-conjugated organic compounds (π-COCs), as a potential electrode material, mainly emphasized the effects of functional groups and intramolecular π-conjugated system on charge storage in the past studies. In this work, we discovered a brand-new two step energy storage mechanism for π-COCs using oligomeric naphthalene (ONA) with intermolecular π-π stacking structure as electrode material in Al ion battery system. The electrochemical reaction of ONA is identified as the synergistic work of the chemical-adsorption of AlCl4- anions at low potential and the π···[AlCl4]···π interaction at high potential. Based on this, the Al-ONA battery exhibits an excellent electrochemical performance (high specific capacity of 450 mAh/g at 0.1 A/g, long cycle life without attenuation for 4000 cycles at 1 A/g). This discovery of the energy storage mechanism, especially for the π···anion···π interaction, for π-COCs materials opens the door to exploring high performance organic electrode materials in energy storage field.

Nonplanar π-Conjugated Sulfur Heterocyclic Quinone Polymer Cathode for Air-Rechargeable Zinc/Organic Battery with Simultaneously Boosted Output Voltage, Rate Capability, and Cycling Life.

π-conjugated organic compounds with a good charge transfer ability and rich redox functional groups are promising cathode candidates for air-rechargeable aqueous Zn-based batteries (AAZBs). However, the output voltage of even the state-of-the-art π-conjugated organic cathodes lies well below 0.8 V, resulting in insufficient energy density. Herein, we design a nonplanar π-conjugated sulfur heterocyclic quinone polymer (SHQP) as an advanced cathode material for AAZBs by polymerization 1,4-Benzoquinone (BQ) and S heteroatoms periodically. The extended π-conjugated plane and enhanced aromaticity endow SHQP with a more sensitive charge transfer ability and robust structure. Furthermore, the delocalized π electrons in the whole system are insufficient as the π orbit of the S heteroatom is not in the same plane with the π orbit of BQ due to its folded configuration, resulting in negligible variation of electron density around C═O after the polymerization. Thus, the output voltage of SHQP shows no significant decrease even though the thioether bond (-S-) functions as electron donor. Consequently, the Zn/SHQP AAZBs can deliver a record high midpoint discharging voltage (0.95 V), rate performance (119 mAh g-1 at 10 A g-1), and durability (98.7% capacity retention after 200 cycles) across a wide temperature range.

Density functional theory, Monte Carlo simulation and non-covalent interaction study for exploring the adsorption and corrosion inhibiting property of double azomethine functionalised organic molecules

Designing efficient corrosion inhibiting molecules is very important prior to its synthesis and analysis of the anticorrosive property. In this regards, the double azomethine functionalised highly π-conjugated aromatic organic compounds possessing strong and moderate electron activating groups, namely, 4,4'-{1,4-phenylenebis[(E)-methanylylidene-(E)-azanylylidene]}diphenol (TA); 2,2'-{1,4-phenylenebis[(E)-methanylylidene-(E)-azanylylidene]}di(pyrimidine-4,6-diol) (TAD) and 2,2'-{1,4-phenylenebis[(E)-methanylylidene-(E)-azanylylidene]}di(pyrimidine-4,6-dithiol) (TADT) were synthesized and characterised. Subsequently, the in-depth electronic properties were explored using ab initio density functional theory and local reactivity analysis. Afterwards, the interaction spontaneity and mechanism, along with equilibrium adsorption configurations onto Fe(110) surface was probed employing Monte Carlo simulation approach. Additionally, non-covalent interactions within a molecular structure and after its adsorption onto a targeted iron surface were explored using reduced density gradient analysis. Consequently, the obtained results have been explained and the expected corrosion inhibition mechanism, as well as the inhibition capability, have been predicted.

Large π-Extended and Curved Carbon Nanorings as Carbon Nanotube Segments.

ConspectusDesigning and synthesizing topologically unique molecules is a long-term challenge for synthetic chemists. Classical polycyclic aromatic hydrocarbons (PAHs) are a large group of π-conjugated planar organic compounds with rich photophysical and electronic properties, while nonplanar/curved PAHs have different molecular orbital arrangements and demonstrate unique properties. The chemistry of curved aromatic molecules has been of significant interest to explore the relationship between π conjugation and molecular geometry, which offers an attractive combination of fundamental problems, potential applications, and aesthetic appeal. Remarkable advances have been made in the last few decades during the discovery of novel curved aromatic molecules, including corannulenes, fullerenes, and carbon nanotubes (CNTs). Especially, there has been increasing interest in making single-chirality CNTs and their curved molecular components (known as finite segments of CNTs) with a fixed geometry. The most representative examples of such organic molecules are cycloparaphenylenes (CPPs) and related carbon nanorings, which possess cylindrical topologies and nanoscale conjugated segments similar to CNTs. CPPs, as the shortest cross-section and the simplest structure of armchair CNTs, have been synthetically accessible since 2008. Recent years have witnessed breakthroughs and rapid development in the synthesis of CPP-based nanorings as well as their derived molecules. In these molecules, the distortion from aromatic planarity can induce radially oriented π systems and further affect their electronic, optical, self-assembly, and charge-transport characteristics. These unique and interesting carbon nanorings are potentially useful in a variety of optoelectronic and biomedical materials. It is well-known that extension of the π-conjugated system facilitates the delocalization of π electrons and the redistribution of electronic clouds, leading to rich diversification of physical properties in the fields of electronics, optics, and supramolecular chemistry. Therefore, the precise design and controllable synthesis of carbon nanorings with large π conjugation will promote important advances in synthetic chemistry. To date, a number of π-extended carbon nanorings have been reported, and they exhibit novel physicochemical properties resulting from their fascinating topologies and structures. However, challenges still remain in the synthesis of π-extended carbon nanorings and their structural analogues and exploration of their unique properties.In this Account, we give a brief overview of our efforts to synthesize large π-extended carbon nanorings using different strategies and explore their novel applications. In 2013 we started our research on the synthesis of carbon nanorings with large π-conjugated structures. This research project has led to (i) the successful preparation of a series of carbon nanorings with inserted PAHs, especially with various nanographenes inserted, such as hexa-peri-hexabenzocoronene; (ii) the design and synthesis of a series of carbon nanorings consisting solely of PAHs; and (iii) the initial synthesis of π-extended carbon-nanoring-based polymers as the long polymeric segments of CNTs, in which macrocyclic CPPs as the basic repeating blocks were covalently coupled together. Herein we describe in detail how these challenging π-extended carbon nanorings were synthesized, and their interesting physical properties are discussed.

On the Optical Activity of Poly(l-lactic acid) (PLLA) Oligomers and Polymer: Detection of Multiple Cotton Effect on Thin PLLA Solid Film Loaded with Two Dyes

Optical rotatory dispersion (ORD) is a beautiful analytical technique for the study of chiral molecules and polymers. In this study, ORD was applied successfully to follow the degree of polycondensation of l-(+)-lactic acid toward the formation of poly(lactic acid) oligomers (PLAO) and high molecular weight poly(l-lactic acid) (PLLA) in a simple esterification reaction equipment. PLLA is a biodegradable polymer obtainable from renewable raw materials. The racemization of the intrinsically isotactic PLLA through thermal treatment can be easily followed through the use of ORD spectroscopy. Organic or molecular electronics is a hot topic dealing with the combination of π-conjugated organic compounds and polymers with specific properties (e.g., chirality) which can be exploited to construct optoelectronic devices, such as organic light-emitting diodes (OLEDs), organic photovoltaic (OPV) high efficiency cells, switchable chirality devices, organic field-effect transistors (OFETs), and so on. ORD spectroscopy was applied to study either the gigantic optical rotation of PLLA films, as well as to detect successfully the excitonic coupling, occurring in thin solid PLLA green film loaded with a combination of two dyes: SY96 (a pyrazolone dye) and PB16 (the metal-free phthalocyanine pigment). The latter compound PLLA loaded with SY96 and PB16 shows a really gigantic optical activity in addition to typical ORD signal due to exciton coupling and may be considered as a simple and easily accessible model composite of a chiral polymer matrix combined with π-conjugated dyes for molecular electronics studies.

Altering the optoelectronic properties of boron difluoride formazanate dyes via conjugation with platinum(II)-acetylides.

The combination of π-conjugated organic compounds and Pt(ii)-acetylides is a powerful strategy for the production of functional optoelectronic materials. The presence of the heavy element, Pt, in these compounds enhances electronic delocalization generally resulting in low-energy absorption and emission maxima and often leads to intersystem crossing, resulting in phosphorescence. When boron complexes of N-donor ligands, such as boron dipyrromethenes (BODIPYs), are involved the molecular and polymeric materials produced have properties that are advantageous for their use as oxygen-sensors, in triplet-triplet annihilation, and as the functional components of photovoltaics. Based on these exciting results, we endeavored to thoroughly examine the effect of Pt(ii)-acetylide conjugation on the properties of BF2 formazanate dyes, which offer improved redox properties and red-shifted absorption and emission bands compared to many structurally related BODIPYs. The results showed that phosphine-supported Pt(ii)-acetylide incorporation enhanced electronic conjugation, rendering the electrochemical reduction of the BF2 formazanate dyes more difficult, while also red-shifting their absorption and emission maxima. Unlike similar BODIPYs, the presence of Pt(ii) did not facilitate phosphorescence, but rather quenched fluorescence. This study provides significant insights into structure-property relationships and guiding principles for the design of BF2 formazanate dyes, a rapidly emerging family of readily accessible optoelectronic materials.

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Doping the Backbone of π-Conjugated Polymers with Tricoordinate Boron: Synthetic Strategies and Emerging Applications.

The doping of π-conjugated organic compounds with trivalent boron atoms produces materials with intriguing properties and functions that result from the interaction of the π-electron system with the vacant p orbital on boron. This offers unique opportunities in various applications such as organic (opto)electronics, biomedical imaging, and sensors for physiologically relevant anions or amines, as demonstrated by numerous examples on the molecular scale. Recently, the B-doping strategy has been expanded to polymer chemistry with a view to benefit from the best of both worlds. Herein, recent advances in the synthesis of π-conjugated polymers doped with tricoordinate boron in the backbone are reviewed. Selected applications are described where these functional materials have already been successfully implemented.

Synthesis, Characterization and Photophysical Properties of Benzylidene-Fluorene Derivatives

A convenient and rapid method for the synthesis of benzylidene-fluorene from aromatic aldehydes and fluorene in presence of 1, 8-diazobicyclo [5,4,0] undec-7-ene (DBU) as an organic catalyst at room temperature giving good yields, short reaction time and easy isolation. Fluorene based π-conjugated organic compounds have found dominant usance that bring about them deserved entrant for utilizations in organic optoelectronic devices and chemical sensors. The report high points an approach to synthesize these materials and to study the photophysical properties

Domino Direct Arylation and Cross-Aldol for Rapid Construction of Extended Polycyclic π-Scaffolds.

Five-membered aromatic heterocycles are a ubiquitous skeleton of π-conjugated organic compounds, and their incorporation requires synthetic protocols that are not easily industrially sustainable or scalable. Improved methodologies for their insertion into π-scaffolds are therefore necessary. We report an efficient and scalable protocol involving a one-pot cross-Aldol direct arylation reaction protocol for the rapid construction of thiophene- and furan-based π-extended organic materials.

ChemInform Abstract: B=N Units as Part of Extended π‐Conjugated Oligomers and Polymers

AbstractReview: [39 refs.

B=N Units as Part of Extended π-Conjugated Oligomers and Polymers.

The replacement of C=C units by their isoelectronic and isosteric B=N units (BN/CC isosterism) in π-conjugated organic compounds, as a strategy to produce novel organic-inorganic hybrid materials, has recently been successfully transferred to π-conjugated polymers. This Concept provides an overview of the recent advances in this quickly evolving field, with a focus on synthesis, photophysical and electrochemical properties of the new polymers and related oligomers, as well as possible future applications in organic electronics and optoelectronics.

Research in the Field of Organic Photovoltaics at the Institute for Problems of Chemical Physics of Russian Academy of Sciences

AbstractIn the present review we highlight the main research activities in the field of organic photonics and photovoltaics at the Institute for Problems of Chemical Physics of Russian Academy of Sciences (IPCP RAS). Extensive investigation of optical and electrical properties of π-conjugated organic compounds performed at IPCP RAS since 1960’s resulted in design of many exciting materials representing organic semiconductors, metals and superconductors. Organic Schottky barrier and p/n junction photovoltaic devices constructed at IPCP RAS in 1960’s and 1970’s were among the first examples of reasonably efficient organic solar cells at that time. These early discoveries inspired younger generations of the researchers to continue the work of their mentors and explore the world of organic materials and photonic devices such as molecular photonic switches, organic light emitting diodes, solar cells, photodetectors, photoswitchable organic field-effect transistors and memory elements.

Preparation and Characterization of (E)- and (Z)-2-(Biphenyl-4-yl)-1-(4-bromophenyl)-1-phenylethene Isomers

Department of Chemistry, Chung-Ang University, Seoul 156-756, KoreaReceived February 6, 2014, Accepted February 19, 2014Key Words: 2-(Biphenyl-4-yl)-1-(4-bromophenyl)-1-phenylethene, Single-crystal structure, Horner–Wad-sworth–Emmons reactionVarious π-conjugated organic compounds have been ap-plied in a wide range of optoelectronic devices such asorganic field-effect transistors, organic photovoltaic cells,and organic solid-state lasers.

QSPR modelling of dielectric constants of π-conjugated organic compounds by means of the CORAL software

Simplified molecular input line entry system (SMILES) notations of 116 π-conjugated organic compounds have been used in three random splits to develop single optimal descriptor based quantitative structure–property relationships (QSPR) models for the prediction of dielectric constants by CORAL (CORrelation And Logic). Four kinds of optimal descriptors were obtained based on SMILES, hydrogen suppressed graph (HSG), graph of atomic orbitals (GAO) and hybrid descriptors. The Monte Carlo optimization was carried out for each random split by three different methods: (i) classic scheme; (ii) balance of correlations; and (iii) balance of correlations with ideal slopes. The QSPR models gave reliable and accurate values of dielectric constant for all the π-conjugated organic compounds. SMILES and the hybrid-based QSPR model provided the best accuracy for the prediction of dielectric constants. Statistical characteristics of the QSPR model-1 based on classic scheme method are n = 110, r2 = 0.860, Q2 = 0.860, s = 1.84, MAE = 1.30 and F = 696 (training set), n = 6, r2 = 0.947, Q2 = 0.876, s = 0.955, MAE = 0.647 and F = 71 (test set). These QSPR models are further validated by an external validation set of 25 molecules and the robustness is checked by parameters like k, kk, rm2, r*m2, average rm2, ∆rm2and randomization technique ().

Pyrimidine Ring as Building Block for the Synthesis of Functionalized ?-Conjugated Materials

In the past two decades, π-conjugated organic compounds have attracted much attention due to their potential applications in various fields such as liquid crystals, light-emitting, and nonlinear optical materials and self assembling. Introduction of heteroaryl moieties into π-extended systems are particularly useful where electron transfer is necessary and is a way to modify and sometimes enhance properties of advanced “electro-optic”. In π-conjugated materials, azaheterocycles such as pyrimidine, which owing to its aromaticity, its strong electron-withdrawing character, its high dipolar interaction and its pH sensibility, presents the requested characteristics to be incorporated in organic materials in view of numerous and various applications. Such molecular architectures and their applications are reported in this review. Keywords: Pyrimidine, π-conjugated-materials, liquid crystals, non-linear optic, luminescence, charge transport, supramolecular assemblies

ChemInform Abstract: Incorporation of Pyridazine Rings in the Structure of Functionalized π‐Conjugated Materials.

AbstractReview: ca. 170 refs.

Elucidation of specific aspects of dielectric constants of conjugated organic compounds: a QSPR approach

The characteristic aspects of dielectric constants of π-conjugated compounds are elucidated by a quantitative structure property relationship (QSPR) study. To develop a QSPR model, among 141 collected π-conjugated compounds, a subset of 116 compounds was used as the training set for the model building and the rest was used as the test set for the model validation. Statistical regression models using 396 molecular descriptors were generated based on the genetic function approximation algorithm. The predicted dielectric constants obtained by the best model are highly correlated with the experimental values (squared correlation coefficient R(2) of 0.93 and 0.97 for the training and test sets, respectively), while a previous prediction model for general organic molecules (Sild S, Karelson M (2002) J Chem Inf Comput Sci 42:360-367) is not valid for our collected π-conjugated organic compounds. It has been known that the dielectric constants of organic materials are largely influenced by orientational correlations of the constituent molecules. In general, hydrogen bonding is one of the most important intermolecular interactions affecting orientational correlation. In the case of π-conjugated compounds, however, π-π interaction could be another comparable interaction with the hydrogen bonding.

Incorporation of pyridazine rings in the structure of functionalized π-conjugated materials

Throughout the past few decades, the development of new π-conjugated organic compounds has received a lot of attention due to their potential applications ranging from liquid crystals, light-emitting and nonlinear optical applications to self-assembly and supramolecular chemistry. Most of these applications rely on electron transfer (ET) and excitation energy transfer (EET). Introduction in these conjugated structures of N-heterocycles such as the highly electronegative pyridazine ring appeared particularly interesting since the π-deficient character of the pyridazine, used as a dipolar moiety, favored the electron transfer. Moreover, the presence of nitrogen atoms with free electron pairs allows the pyridazine ring to act like as an effective and stable complexing agent for transition metal ions and to be used in supramolecular chemistry for the construction of highly sophisticated architectures. This review highlights recent π-conjugated materials including pyridazine ring and their applications in various fields.

Synthesis of New Thiophene-Based π-Conjugated Organic Compounds and Polymer

Abstract p-Dibromobenzenes and p-phenylenediboronate with π-conjugated bithiophene and terthiophene arms were synthesized. They showed UV–vis absorption peaks in the range of 376–417 nm. p-Phenylenediboronate with bithiophene arms were used for synthesis of a new π-conjugated polymer consisting of isothianaphthene and the p-phenylene units with π-conjugated bithiophene side chains.