Fused Thiophene Rings Research Articles

Aromaticity in the Electronic Ground and Lowest Triplet States of Molecules with Fused Thiophene Rings.

Analysis of the variations of the off-nucleus isotropic magnetic shielding, σiso(r), around thiophene, thienothiophenes, dithienothiophenes and sulflowers in their electronic ground (S0) and lowest triplet (T1) states reveals that some of the features of aromaticity and bonding in these molecules do not fit in with predictions based on the popular Hückel's and Baird's rules. Despite having 4n π electrons, the S0 states of the sulflowers are shown to be aromatic, due to the local aromaticities of the individual thiophene rings. To reduce its T1 antiaromaticity, the geometry of thiophene changes considerably between S0 and T1: In addition to losing planarity, the carbon-carbon two 'double' and one 'single' bonds in S0 turn into two 'single' and one 'double' bonds in T1. Well-defined Baird-style aromaticity reversals are observed between the S0 and T1 states of only three of the twelve thiophene-based compounds investigated in this work, in contrast, the sulflower with six thiophene rings which is weakly aromatic in S0 becomes more aromatic in T1. The results suggest that the change in aromaticity between the S0 and T1 states in longer chains of fused rings is likely to affect mostly the central ring (or the pair of central rings); rings sufficiently far away from the central ring(s) can retain aromatic character.

Aryl‐Bridged Thienonaphthalimides: Synthesis, Characterization and Optoelectronic Properties

AbstractThree small molecules consisting of thieno‐fused naphthalimide units connected via aromatic linkers were synthesized to study the effect of fused thiophene rings on the properties of naphthalimide‐based molecules. A protocol for the synthesis of thienonaphthalimide‐based molecules without prior preparation and use of thienonaphthalimide precursors and organoelement compounds (organolithium, organotin, or organoboron compounds) was developed. The protocol is based on double thienannulation of bis‐alkyne substrates with sodium sulfide. The thin‐film morphology, photophysical and electrochemical properties of the obtained small molecules were studied. Single‐layer non‐doped organic light‐emitting diodes based on fluorene‐bridged thienonaphthalimide dimer showed yellow emission with luminance of 2200 cd/m2, and current efficiency of 0.35 cd/A. Combination of transient electroluminescence and photo‐CELIV methods allowed to estimate electron and hole mobility in the synthesized compounds; both are in order of 10−6 cm2V−1 s−1.

Thiophene-fused fulminenes (FuDTs): promising platforms for high-mobility organic semiconductors with a zigzag shape.

Zigzag-shaped [6]phenacene isomers with fused thiophene rings, fulmineno[2,1-b:10,9-b']dithiophene (FuDT-α) and fulmineno[1,2-b:9,10-b']dithiophene (FuDT-β), were syntheized and their p-type organic semicondutor properties were studied. Small effective masses of holes were estimated from the crystal structures of both isomers, which was particularly demonstrated by the hole mobility of 10.5 cm2 V-1 s-1 for FuDT-α single crystals.

Effect of thiophene rings rigidity on dye-sensitized solar cell performance. Dithienothiophene versus terthiophene as [formula omitted] donor moiety

Solar cells are fabricated based on two new dyes. Dye acts as an additive to thin layer interface. The effect of the π-conjugated rigidity of the thiophene rings on the photovoltaic characteristics has been investigated. The structures of the dye 1 was based on dithieno [3,2-b:2′,3′-d] thiophene-2-cyanoacrylic acid, while dye 2 was based on [2,2':5′,2″-terthiophene]-5-cyanoacrylic acid and were confirmed by elemental analysis, mass spectrometry, 1H NMR and 13C NMR spectral data. The P3HT/dye 1/nc-TiO2 solar cell produced the highest efficiency of 0.3 % with an open circuit voltage of 0.7 V compared to dye 2 solar cell. This has been attributed to the difference in energy levels of the dyes and location of their HOMO relative to conduction and valence bands of nc-TiO2. The dye 1 has rigid fused thiophene rings and its HOMO is located between valence band of TiO2 and HOMO of P3HT which leads to improve the charge carrier separation and increase the current density to reach 1.2 mA/cm2.

Protonated Organic Semiconductors: Origin of Water-Induced Charge-Trap Generation.

Despite dramatic improvements in the electronic characteristics of organic semiconductors, the low operational stability of organic field-effect transistors (OFETs) hinders their direct use in practical applications. Although the literature contains numerous reports on the effects of water on the operational stability of OFETs, the underlying mechanisms of trap generation induced by water remain unclear. Here, a protonation-induced trap generation of organic semiconductors is proposed as a possible origin of the operational instability in organic field-effect transistors. Spectroscopic and electronic investigation techniques combined with simulations reveal that the direct protonation of organic semiconductors by water during operation may be responsible for the trap generation induced by bias stress; this phenomenon is independent of the trap generation at an insulator surface. In addition, the same feature occurred in small-bandgap polymers with fused thiophene rings irrespective of their crystalline ordering, implying the generality of protonation induced trap generation in various polymer semiconductors with a small bandgap. The finding of the trap-generation process provides new perspectives for achieving greater operational stability of organic field-effect transistors.

Highly luminescent antiaromatic diborinines with fused thiophene rings.

Tricoordinate boron-incorporated π-conjugated systems are widely investigated as optoelectronic materials because of their unique p-π* orbital interactions and high Lewis acidity. Among them, thiophene-fused diborinines are characterized by moderate antiaromaticity and extended conjugation. In this work, we have developed two new dithienodiborinines with C2h and C2v symmetries, which exhibited completely different optical properties. The thiophene-fused diborinines synthesized in this study showed excellent fluorescence properties both in solution and in the solid state, with quantum yields of up to 95%. The high antiaromaticity enhanced the Lewis acidity of the boron centers, as proven by the large association constants with fluoride ion estimated from titration experiments. The high Lewis acidity and the superior luminescence property have enabled their application as fluorescent sensor materials for the detection of ammonia vapor.

Computational Study on the Effect of Thienyl π-Donor on the Optical Response of Nonclassical Oligo-Pyrazinothienothiadiazole Biradicaloids.

Computational analyses were performed on nitrogen-rich oligothiadizolothiophenes TTn (n = 0-3) and their four π-donor-substituted derivatives Th-TTn (n = 0-3) to examine the optical response due to geometrical and electronic structural attributes in the longitudinal and transverse axes, respectively. Our results are understood in the context of greater conjugation in the longitudinal axis (via additional fused rings) and substitution of a thienyl π-donor in the transverse axis of the geometry of each derivative. On inspection of the frontier molecular orbitals, we found that the better electron-accepting ability with minimal sacrifice in the ionization potentials results from geometrical aspects in both longitudinal and transverse axes. Due to the narrowed highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, all of the derivatives exhibit a biradicaloid character (BRC) and one-photon panchromatic absorption; however, the open-shell nature weakened the charge transfer characteristics of excitation. In both the series, the odd electron density distributions and electron localization plots amply demonstrate the weakening of ylide character in fused thiophene rings and clearly indicate to the emergence of a long-bond/single BRC in the sulfurdimithide moiety in both series. In addition, the estimated tensor components of the second hyperpolarizability as well as overall responses confirm the shift from the longitudinal to transverse axis following the substitution with the π-donor. Interestingly, the TPA cross sections show comparable behavior, but contrary to γ, π-donor thienyl substitution appears to be discouraging in getting higher TPA responses for higher homologous series. Therefore, this study opens a new conjecture on tuning better nonlinear optical properties of organic functional materials.

THEORETICAL INVESTIGATION OF THE EFFECT OF CONJUATION OF THIOPHENE RINGS ON THE CHARGE TRANSPORT OF THIENOCORONENE DERIVATIVES

Based on density functional theory, quantum chemical calculations of the charge-transport rates were performed for five disc-shaped coronene derivatives with varying numbers of fused thiophene rings, using different basis sets 6-31+G(d) and 6-311++G(d,p), hybrid functionals (B3LYP, M06-2X, CAM-B3LYP, WB97XD, M08-HX), and a dispersion-corrected hybrid functional (M06-2X+D3). Our results indicate that increasing the basis set and adding diffusion and polarisation functions had little effect on the molecular reorganisation energy, charge-transport matrix element t, and charge carrier mobility μ. The charge carrier mobility calculated using B3LYP were relatively large, whereas the results calculated using CAM-B3LYP and WB97XD were similar. Among the five coronene derivatives, molecule b with one thiophene ring could be candidates for a n-type organic semiconductor, and molecule c with two thiophene rings can be designed as a p-type semiconductor.

The Critical Role of Electron‐Donating Thiophene Groups on the Mechanical and Thermal Properties of Donor–Acceptor Semiconducting Polymers

AbstractOrganic semiconducting donor–acceptor polymers are promising candidates for stretchable electronics owing to their mechanical compliance. However, the effect of the electron‐donating thiophene group on the thermomechanical properties of conjugated polymers has not been carefully studied. Here, thin‐film mechanical properties are investigated for diketopyrrolopyrrole (DPP)‐based conjugated polymers with varying numbers of isolated thiophene moieties and sizes of fused thiophene rings in the polymer backbone. Interestingly, it is found that these thiophene units act as an antiplasticizer, where more isolated thiophene rings or bigger fused rings result in an increased glass transition temperature (Tg) of the polymer backbone, and consequently elastic modulus of the respective DPP polymers. Detailed morphological studies suggests that all samples show similar semicrystalline morphology. This antiplasticization effect also exists in para‐azaquinodimethane‐based conjugated polymers, indicating that this can be a general trend for various conjugated polymer systems. Using the knowledge gained above, a new DPP‐based polymer with increased alkyl side chain density through attaching alky chains to the thiophene unit is engineered. The new DPP polymer demonstrates a record low Tg, and 50% lower elastic modulus than a reference polymer without side‐chain decorated on the thiophene unit. This work provides a general design rule for making low‐Tg conjugated polymers for stretchable electronics.

Dithieno[3,2-b:2′,3′-d]pyrrole-based hole transport materials for perovskite solar cells with efficiencies over 18%

Dithieno[3,2-b:2′,3′-d]pyrrole (DTP) derivatives are one of the most important organic photovoltaic materials due to better π-conjugation across fused thiophene rings.

Exploring the relevance of thiophene rings as bridge unit in acceptor-bridge-donor dyes on self-aggregation and performance in DSSCs.

The possibility of dye charge recombination in DSSCs remains a challenge for the field. This consists of: (a) back-transfer from the TiO2 to the oxidized dye and (b) intermolecular electron transfer between dyes. The latter is attributed to dye aggregation due to dimeric conformations. This leads to poor electron injection which decreases the photocurrent conversion efficiency. Most organic sensitizers are characterized by an Acceptor-Bridge-Donor (A-Bridge-D) arrangement that is commonly employed to provide charge separation and, therefore, lowering the unwanted back-transfer. Here, we address the intermolecular electron transfer by studying the dimerization and photovoltaic performance of a group of A-Bridge-D structured dyes. Specifically, eight famous sulfur containing π-bridges were analyzed (A and D remained fixed). Through quantum mechanical and molecular dynamics approaches, it was found that the formation of weakly stabilized dimers is allowed. The dyes with covalently bonded and fused thiophene rings as Bridges, 6d and 7d as well as 8d with a fluorene, would present high aggregation and, therefore, high probability of recombination processes. Conversely, using TiO2 cluster and surface models, delineated the shortest bridges to improve the adsorption energy and the stability of the system. Finally, the elongation of the bridge up to 2 and 3 units and their photovoltaic parameters were studied. These results showed that all the sensitizers are able to provide similar photocurrent outcomes, regardless of whether the bridge is elongated. © 2017 Wiley Periodicals, Inc.

Influence of π-linker on triphenylamine-based hole transporting materials in perovskite solar cells

In this work, three simple hole transporting materials containing a thiophene, thieno [3,2-b]thiophene (two fused thiophene rings) or a dithieno[3,2-b:2′,3'-d]thiophene (three fused thiophene rings) as π-linker substituted by 4′,4″-dimethoxytriphenylamine donor groups are presented. The influence of increasing fused thiophene rings of π-linker in new compounds on the photophysical, electrochemical, thermal properties, hole mobility and photovoltaic performance in perovskite solar cells are investigated. The compound, in which dithieno[3,2-b:2′,3'-d]thiophene act as π-linker, shows better hole mobility and higher thermal stability than the compounds that contain thiophene or thieno [3,2-b]thiophene π-linker. Due to the improved hole mobility and superior hole extraction ability of the compound which contains dithieno[3,2-b:2′,3'-d]thiophene π-linker, the perovskite solar cells based on it achieve higher Jsc, Voc and FF values than the devices based on the other two compounds. These results indicate that the increasing fused thiophene rings of π-linker in hole transporting materials can be helpful to develop efficient perovskite solar cells.

Tuning the fused aromatic rings to enhance photovoltaic performance in wide band-gap polymer solar cells

Abstract Two novel wide band-gap polymers of PFT1 and PFT2 were designed as the alternative to P3HT in organic electronics, in which the fused aromatic rings were utilized and altered to tune their molecular co-planarity and photovoltaic performance in solar cells. As observed, although PFT1 exhibited strong inter-molecular interaction, slightly twisted molecular structure was observed, thus leading to an inferior PCE value of 1.95% in BHJ solar cells and holes mobility of 2.04 × 10 −2 cm 2 V −1 s −1 in OFETs in contrast to its isomeric polymer PBTFT. On the other hand, when the fused thiophene rings was tuned to construct PFT2, much planar polymer backbone was achieved, finally leading to the maximum PCE value of 3.34% in polymer solar cells and much enhanced holes mobility up to 3.93 × 10 −2 cm 2 V −1 s −1 in OFETs. Our results here further indicated that tuning the fused aromatic rings in polymer backbone could improve their charge transfer properties and enhance their photovoltaic performance in solar cells significantly.

Preparation, optical and electrochemical properties, and molecular orbital calculations of tetraazaporphyrinato ruthenium (II) bis(4-methylpyridine) fused with one to four diphenylthiophene units

2,5-Diphenyl-3,4-dicyanothiophene (1) and phthalonitrile (2) were mixed and treated with ruthenium (III) trichloride, 4-methylpyridine, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 2-ethoxyethanol at 135°C, to produce low-symmetrical tetraazaporphyrins (TAPs) (3), (4), (5), and (6) with one to three thiophene rings. Two thiophene-annelated tetraazaporphyrins were isolated as opposite and adjacent isomers 4 and 5. The structure of 3 was determined by X-ray crystallography, showing that the thiophene ring linked at the 3,4-positions on the tetraazaporphyrin scaffold deviates from the mean plane of the four central pyrrole nitrogen atoms (N1–N3–N5–N7). Optical and electrochemical properties of the products were examined by UV–vis and magnetic circular dichroism (MCD) spectroscopy, together with cyclic voltammetry. In the 1H NMR spectra, the signals of 4-methylpyridine coordinating to the central ruthenium atom appeared at a higher magnetic field than those of uncoordinated 4-methylpyridine itself due to the shielding effect of the TAP ring. Increasing the number of fused thiophene rings resulted in 1) lower magnetic field shifts of the signals of axially coordinated 4-methylpyridine in the 1H NMR spectra, 2) lower energy shifts of the Q band absorption in the UV–vis spectra, and 3) decreasing (cathodic shift) of the first oxidation potentials. The structures of simplified model compounds were optimized using the DFT method with the Gaussian 09 program at the B3LYP/LANL2DZ level for the Ru atom and the B3LYP/6-31G (d, p) level for the C, H, N, and S atoms. The optimized structures were utilized to calculate the NMR shielding constants, the HOMO and LUMO orbital energies, and the electronic absorption spectra.

Novel enaminone derived from thieno [2,3-b] thiene: Synthesis, x-ray crystal structure, HOMO, LUMO, NBO analyses and biological activity.

BackgroundDue to their structural and therapeutic diversity, thienothiophene derivatives have attracted much synthetic interest because of their reactivity and biological activity. The thieno [2,3-b] thiophene moiety has been used in the design of a novel pharmaceutical therapies. Additionally, its enaminones derivatives are versatile synthons and have a lot of synthetic applications such as N-heterocycles, wide variety of naturally occurring alkaloids and pharmaceutical drugs.ResultsSynthesis of (2E,2′E)-1,1′-(3,4-diphenylthieno [2,3-b] thiophene-2,5-diyl) bis (3-(dimethylamino) prop-2-en-1-one) 5 was reported. The structure of compound 5 was deduced by spectroscopic techniques. The compound was crystallizes in the monoclinic system with space group P-1 with cell coordinates a=9.9685 (8) Å, b=10.1382 (8) Å, c=13.3220 (11) Å, α=101.018 (2) °, β=94.480 (2) °, γ=107.207 (1) °, V=1249.3 (1) Å3, and Z=2. In the crystal molecules are packed in chains formed via weak intermolecular C21–H21A… O1, C22–H22A…O2 and C27–H27A…O2 hydrogen bondings. Theoretical quantum chemical calculations have been performed on the studied compound using the DFT B3LYP/6-311G (d, p) method. The geometric parameters of the optimized structure are in good agreement with the experimental data obtained from our reported X-ray structure. The two benzene rings and the two side chains are not coplanar with the fused thiophene rings. The electronic spectra of the studied compound have been calculated using the TD-DFT method at the same level of theory. The transition bands at 352.9 nm (f=0.5549) and 332.1 nm (f=0.2190) are due to the H-1 → L (72%) and H → L + 1 (82%) excitations respectively. The NBO calculations were performed to predict the natural atomic charges at the different atomic sites and to study the different intramolecular charge transfer (ICT) interactions occurring in the studied system. It is found that the O and N-atoms have the highest negative charge densities while the S-atoms are the most electropositive. These results give idea about how our molecule could react with the receptor active sites. Compound 5 was evaluated against ant-microbial activity.ConclusionsSynthesis, molecular structure and spectroscopic invesitgation of (2E,2′E)-1,1′-(3,4-diphenylthieno [2,3-b] thiophene-2,5-diyl) bis (3- (dimethylamino) prop-2-en-1-one) 5 was studied.Graphical Molecular structure investigation of novel enaminone derived from thieno [2,3-b] thiene.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-015-0100-9) contains supplementary material, which is available to authorized users.

Synthesis and Characterization of Donor-Acceptor Copolymers Having Dithienophene – Benzothiadiazol Moieties Suitable for Use in Solar Cells

Since the discovery of conducting polymers, researches have been focused on the design and synthesis of new type polymers for development of novel conductive materials. Wynberg et al. have discovered donor-acceptor copolymers and this event has received a great deal of interest. The most important feature of these copolymers is that the band gaps are lowered because of the delocalization of π electrons over electron-donating and electron-accepting groups. For this purpose, several donor and acceptor groups were introduced and they have been concluded to be suitable for light emitting diodes (LEDs) and solar cells. Dithienothiophenes, comprising three fused thiophene rings, have a quite rich electronic structure and therefore, they are expected to show a donor-type behavior. Recently, better donor-type groups were discovered when compared to the ones in the past and their properties were investigated in terms of usability in solar cell applications. In this study, we have synthesized and characterized DTT-Btz-containing donor-acceptor copolymers.

Synthesis, Crystal Structures, and Skeletal Inversion of Dithienodiphosphorines

ABSTRACTtrans‐ and cis_endo‐Diphenyl[c]dithienodiphosphorines 1a and 1b were successfully synthesized as phosphorus atoms are trivalent. Two stereoisomers, trans form 1a and cis_endo form 1b, were isolated by preparative gel permeation chromatography (GPC) and their butterfly structures were shown by X‐ray crystallographic analyses of the single crystals from hexane/CHCl3 and CH3CN/CHCl3, respectively. The VT‐31P{1H} NMR spectra in CD2Cl2 showed that the signal due to cis_endo form 1b appeared at δP −45.0 with 9.5 Hz of half‐width at −90°C, which is almost same as that at room temperature, while broadening of the signal due to trans form 1a was observed and finally the signal appeared at δP −33.7 with 55.5 Hz of half‐width at −90°C. The results indicated that the skeletal inversion of a tricyclic system in solution is a fast process on the NMR timescale. On the other hand, X‐ray crystallographic analysis showed that trans‐dimesityl[c]dithienodiphosphorine 2a has a planar structure, which is considered as the corresponding transition state of the skeletal inversion of trans form 1a. The 31P signal due to 2a in CD2Cl2 did not change at all even at −90°C, which was in a different manner from 1a at the same temperature, showing that its planar structure is also kept in solution because of the release of the steric repulsion between bulky mesityl groups and fused thiophene rings in the butterfly structure. The density functional theory calculations suggested the low‐energy barriers of the skeletal inversion of trans–trans and cis_endo–cis_exo forms, which were estimated to be 3.79 and 3.31 kcal/mol by searching for transition state using the synchronous transit‐guided quasi‐Newton (STQN) methods.

Diarylated Bi(thieno[2,3‐c]thiophene)s: A Ring‐Fusing Strategy for Controlling the Molecular Alignment of Oligoarenes

Red means go: The dense π stacking of thiophene-fused bithiophene derivatives in the crystalline state led to significantly red-shifted absorption and fluorescence bands (see the photograph of one compound in solution and in the solid state under UV irradiation). The π-stacking structure could be altered by changing the orientation of one of the fused thiophene rings.

Photochemical Double 5‐exo Cyclization of Alkenyl‐Substituted Dithienylacetylenes: Efficient Synthesis of Diarylated Dithienofulvalenes

Smooth and selective: Upon photoirradiation, bis(3-alkenyl-2-thienyl)acetylenes smoothly and selectively undergo double 5-exo-dig cyclization to produce a series of thiophene-fused pentafulvalenes with various aryl substituents. In this fused π-conjugated skeleton, the fused thiophene rings and the aryl substituents significantly modulate the electronic structure of the pentafulvalene skeleton.

Electronic structure calculations for the study of D-π-A organic sensitizers: Exploring polythiophene linkers

In this work we present a detailed study of the atomic and electronic structure of a collection of push–pull organic dyes for high-performance sensitized solar cells (DSSCs). We compare the computed photophysical properties of donor-bridge-acceptor (D-π-A) dyes with polythiophene (Tn) or polycyclopentadithiophene (Cn) conjugated linkers with up to four fused thiophene rings. Excitation energies to lowest excited singlet state have been rationalized by means of fragment and molecular orbitals. Vertical and adiabatic excitation energies are systematically lower for the Cn family and become smaller with the length of the molecular conjugation. We discuss a large variety of computational techniques for the characterization of the charge transfer (CT) nature of the electronic excitation. In addition to standard procedures to quantify CT character, we propose and explain several novel interaction based measures of CT. Finally, we have computed ground and excited state oxidation potentials (GSOP and ESOP) with long-range corrected (LRC) functional.