Asymmetric Molecules Research Articles

Multispectral compatible anti-reconnaissance strategy: Implementing a modulation system integrating visible light-hyperspectral-radar wave

To tackle the challenges of multi-spectral reconnaissance technology, a pioneering anti-reconnaissance device that integrates visible-light, hyperspectral, and microwave radar functionalities has been developed for the first time. By oxidative polymerization method to create a core–shell Fe3O4@polyaniline composite material for the counter electrode. This design optimized impedance matching, achieving wideband radar wave absorption up to 10.5 GHz (reflection loss < -10 dB). The core–shell structure enhanced specific surface area, improving charge exchange and electrochemical performance to meet stringent counter electrode requirements. And, constructed a frequency-selective metal electrode based on metamaterial principles, complementing the radar wave absorption capabilities of the counter electrode material. Additionally, synthesized an asymmetric viologen molecule as the working electrode, mimicking vegetation color transitions from green to yellow while preserving hyperspectral characteristics and radar wave absorption properties. To enhance hyperspectral compatibility without compromising radar wave absorption or color dynamics, we developed a cross-linked polyvinyl alcohol/hydroxyethyl cellulose film based on biomimetic principles. The device can switch between yellow and green under voltages of 0 or −1.2 V, with both states exhibiting a spectral similarity to foliage exceeding 0.95 and an effective bandwidth reaching 13.44 GHz. The integration of these three functionalities allows the device to operate independently without interference.

Circuits for the spectroscopic readout of bits from molecular quantum-dot cellular automata

Molecular quantum-dot cellular automata (QCA) may provide high speed, low-power, classical information processing in the post-CMOS era. The readout of molecular QCA bits is challenging because the molecules may be much smaller than transistors and even single-electron transistors. This paper builds on a recent proposal for the spectroscopic readout of bits from asymmetric QCA molecules. Here, we propose circuits for fanning out a bit onto a large QCA circuit to increase the spectroscopic signal-to-noise ratio. As the number of molecules in a fanout circuit grows, the internal bias of each asymmetric cell accumulates, and the circuit may become stuck, tolerating only a very small internal bias. We also propose the use of an applied electric field to compensate for a candidate molecule’s internal bias, thereby restoring switchability, even when the internal bias is significant.

Theoretical design of molecular diode based on thiol- and amino- terminated molecules

Utilizing density functional theory (DFT) and non-equilibrium Green’s function, we systematically studied the electrical transport and rectification properties of thiol- and amino-terminated molecules embedded in graphene nanoribbons. We firstly found the thiol-terminated molecules show better electron transport properties compared to the amino-terminated, which can be attributed to the strong electronwithdrawing ability and favorable coupling effects. Secondly, the symmetrical molecules show almost symmetrical current-voltage (I-V) curves and exhibit negligible rectification effects. On the other hand, the asymmetrical molecules exhibit asymmetrical I-V curves and better rectification performance. The rectification effect is closely related to molecular asymmetry degrees. For example, the rectification ratio of asymmetric N6 ((E)-Nl-(3-aminopropyl)-but-2-ene-1,4-diamine) molecule is much smaller than the N4 (5-phenylthiazole-2,4-diamine) and N5 (2,6-diaminohexane-1,1,5-triol) molecules. Furthermore, we found the rectification ratio of the asymmetrical amino-terminated molecules can reach 400, while the biggest rectification ratio of the thiol-terminated molecule can only reach 45. These findings offer crucial insights for future graphene molecular electronic device design.

Multiphoton‐And SHG‐Active Pyrimidine‐Based Liquid Crystalline Thin Films Toward 3D Optical Data Storage

AbstractAn original asymmetric achiral pyrimidine core molecule, with long carbon chains on one side and a coumarin fragment on the other, is designed. This advanced molecular structure enabled the spontaneous emergence of crystalline and liquid crystalline thin films with strong 2nd harmonic generation (SHG) without any corona polishing process or tedious deposition techniques. Moreover, pin‐pointed multiphoton absorption in the liquid crystalline phase effectively switches off the SHG signal locally and permanently, underlining its interest in 3D data storage. This prototypical material, which can be fully addressed by NLO processes, multiphoton writing, and SHG reading, paves the way for the development of efficient flexible materials for 3D optical data storage.

Asymmetric main-chain twisted small molecules for efficient polymer solar cells

Polymer solar cells (PSCs) based on small molecules with twisted backbones as electron acceptors, have many advantages over their planar counterparts, such as upshifted molecular energy levels, better charge extraction performance, enhanced extinction coefficient, extended carrier lifetime and reduced recombination rate, which are very helpful in improving the power conversion efficiencies (PCE). The present study was designed to synthesize two new small molecules with main-chain twisted structures that include an asymmetric electron donor core thiophene-phenylene-thieno[3,2-b]thiophene, namely i-T-TT and i-T-TT-4F, to investigate the “structure-property” correlation of main-chain twisted acceptors. Both asymmetric molecules exhibit bent geometric structures, and the fluorinated acceptor i-T-TT-4F possesses a more red-shifted spectrum, improved molar extinction coefficient, and deepened molecular energy levels. As a result, when combined with the middle bandgap polymer donor J52, there was a remarkable efficiency of 12.22 % for the device of i-T-TT-4F, higher than that of i-T-TT (9.51 %). Our research illustrates the importance of the main-chain twisted asymmetric electron-donating core and fluorinated end-capping group in the construction of efficient PSCs.

Thin-film polydiacetylenes of a stable blue phase based on symmetrical and unsymmetrical diacetylene &lt;i&gt;N&lt;/i&gt;-arylcarbamates

The conditions and features of the formation of Langmuir monolayers of symmetrical and asymmetrical diacetylene N-arylcarbamates and the structural organization of Langmuir-Schaefer films based on them were studied. Photopolymerization of monolayer solid films of two types of molecules was monitored using absorption spectroscopy and showed the transition of diyne molecules to the blue phase polydiacetylene state. The efficiency of the solid-phase topochemical polymerization reaction in a film of symmetrical diynes turned out to be 5 times higher than in a film of asymmetrical diyne molecules. The morphology of monolayer surfaces before and after UV irradiation was studied using scanning electron microscopy.

Rotational properties of two interacting cold polar molecules: Linear, symmetric, and asymmetric tops

We examine the potential-energy curves and polarization of the dipole moments of two static polar molecules under the influence of an external dc electric field and their anisotropic dipole-dipole interaction. We model the molecules as quantum rigid rotors to take their rotational degrees of freedom into account and consider a selection of linear, symmetric, and asymmetric top molecules. We provide a comprehensive examination of the energy curves and polarization of the dipoles for varying intermolecular separation and direction of the electric field and find that the properties of the molecules depend strongly on the field's direction at short separations, showing the importance of accounting for molecular rotation. The latter provides insight into the possible effects of accounting for rotational degrees of freedom in molecular dipolar gases. Published by the American Physical Society 2024

New Molecularly Flexible Self-Assembling Benzothiadiazole Derivatives: Mesomorphism And DFT Investigations

In the present study, we have synthesized symmetric/unsymmetrical BTD embedded self-assembling molecules and investigated for their mesomorphic properties. Two symmetrical series (BTDK-(2-18) and BTDC-(4-18)) comprises benzothiadiazole moiety as a central core unit which is connected to two different systematically varied end-groups, alkoxy ester and alkoxy coumaryl unit connected through ether and imine linkages. On the other hand, the asymmetric molecules have an alkoxy chalconyl unit at one end and a formyl group at the other. It was observed that, the mesomorphism is completely depends on the molecular flexibility. New molecules revealed mesomorphic behaviour with N (nematic), SmA (smectic-A) and SmC (smectic-C) mesophase with high thermal stability and greater range. Changes in mesogenic units (alkoxy ester & alkoxy coumaryl unit) and the impact of altering the alkoxy chain at both ends have been investigated. Interesting evaluation has been carried out on the molecular flexibility which resulted in different mesomorphic behaviour of molecules under study. Furthermore, the experimentally established values of the mesophase thermal stability (Tc) and mesophase temperature ranges (ΔTSmA, ΔTSmC, and ΔTN), as well as the type of the mesophase, were related to the calculated quantum chemical parameters (Frontier molecular orbitals (FMOs), Aspect Ratio, Polarizability, dipole moment, molecular and electrostatic potential (MEP)) that were obtained by using the DFT method of the investigated compounds.

Dipole Moment Modulation of Terminal Groups Enables Asymmetric Acceptors Featuring Medium Bandgap for Efficient and Stable Ternary Organic Solar Cells.

This study puts forth a novelterminal groupdesign todevelopmedium-bandgap Y-series acceptors beyond conventional side-chain engineering.We focused onthe strategical integration of an electron-donating methoxy group and an electron-withdrawing halogen atomatbenzene-fusedterminal groups. This combination preciselymodulatedthedipole moment and electron density of terminal groups, effectively attenuating intramolecular charge transfereffect, and widening the bandgap ofacceptors. The incorporation of theseterminalgroups yielded two asymmetric acceptors, named BTP-2FClO and BTP-2FBrO, both of which exhibited open-circuit voltage (VOC) as high as 0.96 V in binary devices, representing thehighestVOCs among the asymmetric Y-seriessmall molecule acceptors. More importantly, both BTP-2FClO and BTP-2FBrO exhibitmodestaggregation behaviorsandmolecular crystallinity,making themsuitable as a third component to mitigate excess aggregation of the PM6: BTP-eC9 blend and optimize thedevices'morphology.As a result,the optimized BTP-2FClO-based ternary organic solar cells (OSCs) achieved a remarkable power conversionefficiency (PCE)of 19.34%, positioning it among the highest-performing OSCs.Ourstudyhighlights themolecular designimportance on manipulating dipole moments and electron densityindevelopingmedium-bandgap acceptors,andoffersa highly efficient third component forhigh-performance ternary OSCs.

Observation of spectral splitting of whispering-gallery modes in asymmetrical photonic molecules.

This Letter investigates mode splitting via whispering gallery modes (WGMs) in asymmetrical photonic molecules (PMs) composed of size-mismatched dual microspheres fabricated from fused silica. The characteristics of asymmetrical PMs were analyzed both numerically and experimentally, focusing specifically on the separation and intensity differences of splitting peaks. The splitting spectra exhibited a redshift, and the separation of two splitting peaks reached a maximum in symmetrical PMs, with a minimal difference in intensity also observed. It was noted that the splitting peaks shifted in opposite directions for the same PMs when coupling points with the tapered fibers were varied. This phenomenon can be applied to select similarly sized microparticles and to recognize PMs in optical devices.

How Solvation Alters the Thermodynamics of Asymmetric Bond-Breaking: Quantum Simulation of NaK+ in Liquid Tetrahydrofuran.

Gas-phase potential energy surfaces (PESs) are often used to provide an intuitive understanding of molecular chemical reactivity. Most chemical reactions, however, take place in solution, and it is unclear whether gas-phase PESs accurately represent chemical processes in solvent environments. In this work we use quantum simulations to investigate the dissociation energetics of NaK+ in liquid tetrahydrofuran (THF) to understand the degree to which solvent interactions alter the gas-phase picture. Using umbrella sampling and thermodynamic integration techniques, we construct condensed-phase free energy surfaces of NaK+ on THF in both the ground and electronic excited states. We find that solvation by THF completely alters the nature of the NaK+ bond by reordering the thermodynamic dissociation products. Reaching the thermodynamic dissociation limit in THF also requires a long-range charge transfer process that has no counterpart in the gas phase. Gas-phase PESs, even with perturbations, cannot adequately describe the reactivity of simple asymmetric molecules in solution.

Composition Heterogeneity of Metal Ions Bound at the Oxygen-Evolving Center of Photosystem II in Living Cells.

Recent resolution advancement of in situ cryo-electron tomography (cryo-ET) and cryo-electron microscopy (cryo-EM) enables us to visualize large enzymes-in-action in atomic detail in their native environments inside living cells, such as photosystem II (PSII) and the ribosome. A variety of crystallographic and cryo-EM structures of PSII have been published for the purified PSII dimeric core complexes by itself, in supercomplexes with photosystem I (PSI) and light-harvesting complexes (LHC), and in megacomplexes with phycobilisome (PBS). In the latter case, two or five copies of asymmetric dimeric PSII molecules are present in highly asymmetric environments that differ from other 2-fold symmetric structures. Previous systematic analysis of X-ray free-electron laser (XFEL) crystal structures of PSII has shown different degrees of composition heterogeneity of metal ion cofactor bound at the oxygen-evolving center (OEC), including between two monomers of the same PSII dimer. This study analyzed the metal ions bound at four OECs in two asymmetric dimeric PSII molecules within in situ cryo-ET structures reported for an asymmetric PBS-PSII-PSI-LHC megacomplex determined in a living organism without purification and shows that composition heterogeneity with reduced metal ion occupancies at the OEC of PSII is a general phenomenon. This finding could have profound implications for spectroscopic interpretations of unpurified PSII samples.

Dimerized small molecule donor enables efficient ternary organic solar cells

Ternary organic solar cells (OSCs) are the feasible and efficient strategy to achieve the high-performance OSCs. It is of great significance to develop a superior third component candidate for constructing efficient ternary OSCs. In this work, we intelligently designed and synthesized a dimerized small molecule donor by connecting two asymmetric small molecule donors with the vinyl group, which is named DSMD-βV. This innovative oligomeric molecule DSMD-βV not only exhibits the complementary absorption and the cascade energy level arrangement with PM6 and BTP-eC9, but also regulates the phase separation micromorphology based on PM6:BTP-eC9. Consequently, PM6:DSMD-βV:BTP-eC9 based ternary device exhibits the improved exciton dissociation, charge transport and decreased recombination, thus achieving a superior power conversion efficiency (PCE) of 18.26 %, surpassing PM6:BTP-eC9 based binary (17.63 %). This work indicates that the dimerized small molecule donor is able to become a promising third component candidate, which also opens up a unique idea for the construction of efficient ternary organic solar cells.

Enhanced Fill Factor and Efficiency of Ternary Organic Solar Cells by a New Asymmetric Non-Fullerene Small Molecule Acceptor.

Asymmetric non-fullerene small molecules acceptor (as-NF-SMAs) exhibit greater vitality in photovoltaic materials compared to their symmetric counterparts due to their larger dipole moments and stronger intermolecular interactions, which facilitate exciton dissociation and charge transmission in organic solar cells (OSCs). Here, we introduced a new as-NF-SMAs, named IDT-TNIC, as the third component in ternary organic solar cells (TOSCs). The asymmetric IDT-TNIC used indacenodithiophene (IDT) as the central core, alkylthio-thiophene as a unilateral π-bridge and extended end groups as electron-withdrawing. Due to the non-covalent conformational lock (NCL) established between O⋅⋅⋅S and S⋅⋅⋅S, the IDT-TNIC molecule preserves its coplanar structure effectively. Furthermore, IDT-TNIC exhibits complementary absorption and excellent compatibility with donor and acceptor materials, as well as optimized ladder energy level arrangement, resulting in a higher and more balanced μh/μe value, more homogeneous and suitable phase separation morphology in TOSCs. Thus, the PCE of the TOSCs reached 17 % when the weight ratio of PM6 : Y6 : IDT-TNIC was 1 : 1.1 : 0.1, and it is noteworthy that when the device area was increased to 1 cm2, the PCE could still be maintained at over 14 %. Detailed studies and analysis indicate that IDT-TNIC has great potential as a third component in OSCs and for large-scale printing in the future.

Orientational Effects and Molecular-Scale Thermoelectricity Control.

The orientational effect concept in a molecular-scale junction is established for asymmetric junctions, which requires the fulfillment of two conditions: (1) design of an asymmetric molecule with strong distinct terminal end groups and (2) construction of a doubly asymmetric junction by placing an asymmetric molecule in an asymmetric junction to form a multicomponent system such as Au/Zn-TPP+M/Au. Here, we demonstrate that molecular-scale junctions that satisfy the conditions of these effects can manifest Seebeck coefficients whose sign fluctuates depending on the orientation of the molecule within the asymmetric junction in a complete theoretical investigation. Three anthracene-based compounds are investigated in three different scenarios, one of which displays a bithermoelectric behavior due to the presence of strong anchor groups, including pyridyl and thioacetate. This bithermoelectricity demonstration implies that if molecules with alternating orientations can be placed between an asymmetric source and drain, they can be potentially utilized for increasing the thermovoltage in molecular-scale thermoelectric energy generators (TEGs).

Computational Insights into Cinchona‐Based Phase Transfer Catalysisfor Asymmetric Conjugate Cyanation

The synthesis of asymmetric organic molecules has experienced a huge development over the last few decades. Phase‐transfer catalysis has been proven to be one of the most powerful methods for these asymmetric transformations. However, the study of the mechanism of these catalysts and the different interactions that they can establish with the reactants has failed to keep pace. In the present study, the conjugate cyanation of two different α,β‐unsaturated ketones are studied in the presence of a well‐known alkaloid quinine‐derived PTC, along with different modifications. The study includes the comparison of different binding modes between the catalysts and the different reactants, the mechanistic study of the reaction and the analysis of the non‐covalent interactions established within the complexes and their role in the global enantioselectivity of the process.

A Difluoro-Methoxylated Ending-Group Asymmetric Small Molecule Acceptor Lead Efficient Binary Organic Photovoltaic Blend.

Developing a new end group for synthesizing asymmetric small molecule acceptors (SMAs) is crucial for achieving high-performance organic photovoltaics (OPVs). Herein, an asymmetric small molecule acceptor, BTP-BO-4FO, featuring a new difluoro-methoxylated end-group is reported. Compared to its symmetric counterpart L8-BO, BTP-BO-4FO exhibits an upshifted energy level, larger dipole moment, and more sequential crystallinity. By adopting two representative and widely available solvent additives (1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO)), the device based on PM6:BTP-BO-4FO (CN) photovoltaic blend demonstrates a power conversion efficiency (PCE) of 18.62% with an excellent open-circuit voltage (VOC) of 0.933V, which surpasses the optimal result of L8-BO. The PCE of 18.62% realizes the best efficiencies for binary OPVs based on SMAs with asymmetric end groups. A series of investigations reveal that optimized PM6:BTP-BO-4FO film demonstrates similar molecular packing motif and fibrillar phase distribution as PM6:L8-BO (DIO) does, resulting in comparable recombination dynamics, thus, similar fill factor. Besides, it is found PM6:BTP-BO-4FO possesses more efficient charge generation, which yields better VOC-JSC balance. This study provides a new ending group that enables a cutting-edge efficiency in asymmetric SMA-based OPVs, enriching the material library and shed light on further design ideas.

Engineering of asymmetric A1-D1-A2-D2-A1 type non-fullerene acceptors of 4T2CSi–4F derivatives to enhance photovoltaic properties: A DFT study

Designing efficient, non-fused ring-based organic solar cells (OSCs) with high open circuit voltage is a significant challenge. The present research proposes seven novel moieties generated from an existing 4T2CSi–4F (R) asymmetric molecule to increase efficiency. The density functional theory (DFT) was used to examine several essential characteristics like optical, electronic, and efficiency-related properties of molecules. It is revealed that newly presented molecules have superior features that are required to manufacture efficient organic solar cells. They exhibit a lower band gap between 2.05 and 2.34 eV and have a planar shape. Six moieties exhibit lower excitation energy values in the gas and chloroform phases, and five moieties have more excellent dipole moments than the R molecule. UA1 and UA2 show remarkable enhancement in the optoelectronic properties, exhibiting the greater λmax at 773 nm and a smaller excitation energy of 1.60 eV. All the newly presented molecules have lower ionization potential and reorganization energies of the electron. The open circuit voltage (Voc) of five newly designed molecules is greater, varying from 1.40 to 1.55 eV, than R (Voc = 1.38 eV). Furthermore, the newly designed molecules, except UA1 and UA2, show more excellent fill factor (FF) than the R molecule. This significant increase in efficiency-associated metrics (FF and Voc) suggests that these molecules may be effectively implemented to manufacture an upgraded version of OSCs.

Partially “invisible” pulsation of asymmetric soliton molecules

Pulsation is a universal phenomenon in all disciplines of nonlinear science, which generally exhibit various nonlinear soliton dynamic modes in nonlinear optics. With the emergence of real-time spectral measurement technology, a new phenomenon of optical soliton pulsation, “invisible” soliton pulsation, has gradually attracted researchers’ attention. In this paper, by solving the coupled Ginzburg–Landau equation, we have discovered the partially “invisible” pulsation phenomenon of asymmetric soliton molecules (SMs) composed of two unequal-intensity pulses in a normal-dispersion Mamyshev oscillator for the first time. It is indicated that the fluctuation periods of each internal pulse in asymmetric SMs in terms of peak power, energy, and relative phase difference are all four roundtrips. However, the oscillation period of asymmetric SMs energy is two roundtrips, only half of the above period. Further research shows that the oscillation of the relative phase difference between two internal pulses in SMs is related to the variation of their intensity difference, which can also affect the position change of the spectral modulation peak. This work will enrich the research on “invisible” soliton pulsation and is of great significance for promoting the development of nonlinear dissipative systems.

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal-Organic Framework Supercapacitors.

Layered metal-organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.