Π-conjugated Derivatives Research Articles

Efficient Intersystem Crossing in Extended Helical Perylene Diimide Dimers with Chalcogen-Annulation.

The properties and formation mechanisms of the triplet state have been widely investigated since they are crucial intermediates in photo functional devices. Specifically, helical PDI dimers, horizontal expanded π-conjugated derivatives of PDI, have shown outstanding performance as electron acceptors in enhancing the performance of photovoltaics. Therefore, the exploration of triplet generation in helical PDI dimers plays a crucial role in understanding the mechanisms and excavating their further application. We make use of Se-annulation to induce intersystem crossing (ISC) in helical PDI dimers and further explore the triplet evolution process systematically as the number of Se atoms increases by transient absorption spectroscopy and the hole-electron analysis method. It shows that the twisted molecular conformation has paved the way for potential ISC in a parent molecule PDI2. The incorporation of Se atoms can result in evident promotion in the efficiency of ISC (ϕTPDI2-2Se = 96.9%) compared to the parent molecule PDI2 (ϕTPDI2 = 26.5%), indicating that chalcogen-annulation is also an efficient strategy in a π-extended system. Our results provide useful insights for understanding the triplet evolution process, which can help broaden the application of the π-extended PDI system into high-performance photovoltaics.

Strong chiroptical properties from thin films of chiral imidazole derivatives allowing for easy detection of circularly polarized luminescence

We report the synthesis and characterization of four similar chiral 1-methyl-1H-imidazole π-conjugated derivatives. In particular, we focus on the thin film chiroptical characterization (electronic circular dichroism and circular polarized luminescence),...

Narcissistic self-sorting in Zn(II) porphyrin derived semiconducting nanostructures.

The narcissistic self-sorted phenomenon is explicitly attributed to the structural similarities in organic molecules. Although such relevant materials are rarely explored, self-sorted structures from macrocyclic π-conjugated-based p- and n-type organic semiconductors facilitate the increase of exciton dissociation and charge separation in bulk heterojunction solar cells. Herein, we report two extended π-conjugated derivatives consisting of zinc-porphyrin-linked benzothiadiazole acting as an acceptor (PB) and anthracene as a donor (PA). Despite having the same porphyrin π-conjugated core in PA and PB, variations in donor and acceptor moieties make the molecular packing form one-dimensional (1D) self-assembled nanofibers via H- and J-type aggregates. Interestingly, a dissimilar aggregate of PA and PB exists as a mixture (PA + PB), promoting narcissistic self-sorted structures. Electrochemical impedance investigation reveals that the electronic characteristics of self-sorting assemblies are influenced by the difference in electrostatic potentials for PA and PB, resulting in a transitional electrical conductivity of 0.14 S cm-1. Therefore, the design of such materials for the fabrication of effective photovoltaics is promoted by these extraordinary self-sorted behaviors in comparable organic π-conjugated molecules.

Molecular design of new π-conjugated materials based on pyrimidine for organic solar cellsapplication

The research in new π-conjugated molecules with specific applications has become one of the most interesting topics in the fields of chemical physics and materials science.In fact, these compounds have been widely explored, thanks to their essential particular properties, as novel class of promising materials in the field of optoelectronics. In this work, we emphasize the importance of the materials based on pyrimidine π- conjugated derivatives due to their strong potential for solar cell applications. The Density Functional Theory (DFT) approach at B3LYP level and 6-31G(d,p) orbital basis sets for all atoms as implemented in Gaussian 09 program has been used for complete geometry optimization with no constraints of pyrimidine π-conjugated based derivatives.The assessed molecular properties comprise the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and other molecular properties derived from HOMO and LUMO and their respective energies. The absorption spectra were simulated by Time-Dependent Density Functional Theory (TD/DFT) at the B3LYP/6-31G(d,p) level owing to the calculation of the oscillator strengths, the maximum absorption wavelengths and the excitation energy corresponding to the pyrimidine π-conjugated derivatives. The open circuit voltage and the difference between both the LUMO energy levels of the donor and the acceptor have been also evaluated. Hence, we have scanned the rapport, for the molecules under study, between the molecular, the electronic structure and the efficiency of the solar cell in order to give further insights on the possibility of electron transfer between the donor and the acceptor entities. Our results lead to the likelihood to suggest pyrimidine based materials as bulkheterojunction solar cell for organic solar cells application.

ChemInform Abstract: Synthesis and Structure—Property Relationships of Phosphole‐Based π Systems and Their Applications in Organic Solar Cells

AbstractReview: [46 refs.

Synthesis and Structure-Property Relationships of Phosphole-Based π Systems and Their Applications in Organic Solar Cells.

Phosphole is a chemically tunable heterole, and its π-conjugated derivatives are potential candidates for optoelectronic materials. This account describes recent developments in the synthesis and structure-property relationships of π-conjugated phosphole derivatives made by my research group. Thiophene-phosphole-styrene, phosphole-acetylene-arene, oligophosphole, polyphosphole, areno[c]phosphole, and phosphole-heterole π systems are synthesized using titanacycle-mediated metathesis and palladium-catalyzed cross-coupling reactions. The structural, optical, and electrochemical properties of selected compounds are discussed. Initial results on some applications of thiophene-phosphole copolymers, acenaphtho[c]phospholes, and amine-terthiophene-phosphole donor-π-acceptor dyes in organic solar cells are described. These results give valuable information and guidelines for designing new phosphorus-containing organic materials for molecular electronics.

Side Substituent Dependence of Photophysical Properties of 9-Arylanthracene-Based π-Conjugates

Abstract Three new 9-arylanthracene-based π-conjugated derivatives with different side substituent (methyl, methoxy, and hexyloxy) were synthesized using Heck coupling/Horner–Emmons reaction in good yields (72–78%) and their photophysical properties investigated. The dependence of the photophysical properties on the side substituent methyl, methoxy, and hexyloxy has been discussed. The absorption maxima of the synthesized compounds in the solution possess similar absorption bands located at 420–423 nm. They are shown to be thermally stable and emit light in sky blue region (ca. 490 nm) in solution. Photoluminescence measurements show a 25–28 nm red shift between solution and powdered states indicated some aggregation in the solid state. The results of cyclic voltammetry measurements of the compounds show good reversibility, indicating that the compounds have good electrochemical stability.

π-Conjugated derivatives containing phosphole rings: synthesis, properties and coordination chemistry

The synthesis and properties of linear π-conjugated systems incorporating phosphole rings are described. Well defined α,α′-(phosphole-aryl) oligomers present low HOMO–LUMO gaps and their optical and electrochemical properties can be tuned via chemical modifications of the P-atom. These organophosphorous π-conjugated chromophores act as ligands toward transition metal ions giving rise to mono- and di-nuclear complexes. The specific properties of these complexes make them valuable materials for OLED's and interesting building blocks for the tailoring of novel NLO-phores. To cite this article: M. Hissler et al., C. R. Chimie 8 (2005). La synthèse et les propriétés de systèmes π-conjugués linéaires incorporant des cycles phospholes sont décrites. Des oligomères α,α′-(phosphole-aryl) de structures bien définies présentent de faibles écarts HO–BV et leurs propriétés optiques et électrochimiques peuvent être modulées à la suite de modifications chimiques impliquant l'atome de phosphore. Ces chromophores organophosphorés π-conjugués peuvent s'associer à des ions métalliques pour former des complexes mono- ou dinucléaires. Les propriétés spécifiques de ces complexes en font des matériaux attractifs pour les diodes électroluminescentes ainsi que pour des dispositifs actifs en optique non linéaire. Pour citer cet article : M. Hissler et al., C. R. Chimie 8 (2005).

Synthesis, theoretical characterisation and spectra of thiophene–fluorene π-conjugated derivatives

The syntheses, spectral measurements and the theoretical study of 2-((9H-fluoren-9-ylidene)methyl)thiophene ( A), ((9H-fluoren-9-ylidene)methyl)-5-(thiophen-2-yl)thiophene ( B), 1-(5-((9H-fluoren-9-ylidene)methyl)thiophen-2-yl)propan-1-one ( C), 1- (5-((9H-fluoren-9-ylidene)methyl)thiophen-2-yl)pentan-1-one ( D), 1,2-bis(1-(5-((9H-fluoren-9-ylidene) methyl)thiophen-2-yl)propylidene)hydrazine ( E) and 1,2-bis(1-(5-((9H-fluoren-9-ylidene)methyl)thiophen-2-yl)pentylidene)hydrazine ( F) are presented. The electron absorption and fluorescence spectra of prepared molecules are measured in polymer matrix and solution. The influence of the conformation (e.g. cis- and trans-forms in the case of E and F molecules) on electronic spectra are interpreted by ZINDO/S method. Our results indicate that the thiophene rings connected with terminal fluorene chromophores through the double bounded carbon atom seem to be suitable candidates for the subsequent preparation of the electro-optical materials.

D2-Symmetric Dimer of 1,1‘-Binaphthyl and Its Chiral π-Conjugated Carbodianion

The synthesis of a chiral, nonracemic π-conjugated system with D2 point group of symmetry and the corresponding chiral carbodianion is described. Cu(II)-mediated oxidation of (R)-2,2‘-dilithio-1,1‘-binaphthyl (prepared from (R)(+)- 2,2‘-dibromo-1,1‘-binaphthyl) gives the corresponding dimer, (R)(+)-3, which is a chiral π-conjugated derivative of o-tetraphenylene, a saddle shaped molecule. When partially resolved 2,2‘-dibromo-1,1‘-binaphthyl is used, amplification of the enantiomeric excess (ee) is observed in the coupling product (3). The dihedral angles between the naphthalene moieties in (R)(+)-3 are about 70 °, as determined by the X-ray crystallography. However, CD and UV spectra, and cyclic voltammetric data of (R)(+)-3 are consistent with small, but far from negligible, conjugation (or homoconjugation) between the naphthalene moieties. The melting points of (R)(+)-3 and its racemate differ by more than 200 °C. Reaction of (R)(+)-3 with Li or Na in tetrahydrofuran (THF) gives the corresponding chiral...

Molecular design and monolayer stability of oligo(phenylenevinylene derivatives

In order to obtain monolayers of wholly π-conjugated derivatives with improved stability and homogeneity, oligo(phenylenevinylene derivatives with different numbers of phenylenevinylene units, different hydrophilic groups and different substituents at the end of the hydrophobic π-conjugated chain were synthesized and their surface pressure—area isotherms and fluorescence microscopy images were examined. The presence of two phenylenevinylene units was suitable for monolayer formation. Monolayers with improved stability were obtainable from sulfonamide derivatives with a tert-butyl or an octadecyl group at the hydrophobic ends and from a derivative which had a sulfonamide group between the π-conjugated structure and an alkyl spacer group Fluorescence microscopy revealed that the tert-butyl derivative formed a homogeneous monolayer in the condensed region. The effects of the substituents upon the monolayer properties were discussed.