Isomeric Dimers Research Articles

Isomeric Dimer Acceptors for Stable Organic Solar Cells with over 19 % Efficiency

AbstractThe strategy of isomerization is known for its simple yet effective role in optimizing molecular configuration and enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs). However, the impact of isomerization on the design of dimer acceptors has been rarely investigated, and the relationship between the chemical structure and optoelectronic property remains unclear. In this study, we designed and synthesized two dimer acceptor isomers named D‐TPh and D‐TN, which differ in the positional arrangement of their end capping groups. Compared to D‐TN, D‐TPh exhibited enhanced backbone planarity, elevated lowest unoccupied molecular orbital energy level, and more ordered molecular stacking. Consequently, the OSC device based on PM6 : D‐TPh achieved a PCE of 19.05 %, higher than that (PCE=18.42 %) of the device based on PM6 : D‐TN. Large‐area PM6 : D‐TPh devices (1 cm2) yielded a PCE of 18.00 %. More importantly, the extrapolated T80 lifetime of the PM6 : D‐TPh device is over 2800 h with MPP tracking under continuous one‐sun illumination. These results suggest that isomerization strategy is an effective way to optimize the molecular configuration of dimer acceptors for the fabrication of high‐efficiency and stable OSCs.

Isomeric Dimer Acceptors for Stable Organic Solar Cells with over 19 % Efficiency.

The strategy of isomerization is known for its simple yet effective role in optimizing molecular configuration and enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs). However, the impact of isomerization on the design of dimer acceptors has been rarely investigated, and the relationship between the chemical structure and optoelectronic property remains unclear. In this study, we designed and synthesized two dimer acceptor isomers named D-TPh and D-TN, which differ in the positional arrangement of their end capping groups. Compared to D-TN, D-TPh exhibited enhanced backbone planarity, elevated lowest unoccupied molecular orbital energy level, and more ordered molecular stacking. Consequently, the OSC device based on PM6 : D-TPh achieved a PCE of 19.05 %, higher than that (PCE=18.42 %) of the device based on PM6 : D-TN. Large-area PM6 : D-TPh devices (1 cm2) yielded a PCE of 18.00 %. More importantly, the extrapolated T80 lifetime of the PM6 : D-TPh device is over 2800 h with MPP tracking under continuous one-sun illumination. These results suggest that isomerization strategy is an effective way to optimize the molecular configuration of dimer acceptors for the fabrication of high-efficiency and stable OSCs.

Comparative Analysis of Structural Analogs of Dipyridothiazines with m-Xylene and a Lutidine Moiety—In Silico, In Vitro, and Docking Studies

Dimers of dipyridothiazines with an m-xylene moiety are presented in terms of a comparative analysis with anticancer active structural analogs containing a lutidine system. The synthesis of new isomeric dimers was described, the structure of which was confirmed by 1H, 13C and 2D NMR, and HR MS spectroscopic methods. The preliminary prediction of the pharmacological profile using the Way2Drug server indicated the anticancer potential of the tested derivatives. In vitro biological activity tests were performed on a normal skin cell line (HaCaT) and five cancer cell lines, including human primary colon cancer (SW480), human metastatic colon cancer (SW620), human breast adenocarcinoma (MDA-MB-231), human lung carcinoma (A-549), and human glioblastoma (LN-229), which indicated low cytotoxic activity. In order to explain the surprisingly low activity, a comparative structural analysis of the tested analogs compared to the dimers with the lutidine system was performed using quantum mechanics and molecular docking in relation to histone deacetylase. Molecular docking indicated the different binding sites of the analyzed dimers, which explained the differences in the activity.

Deprotonated sulfamic acid and its homodimers: Does sulfamic acid adopt zwitterion during cluster growth?

We present a joint experimental and computational study on the geometric and electronic structures of deprotonated sulfamic acid (SA) clusters [(SA)n–H]− (n = 1, 2) employing negative ion photoelectron spectroscopy and high-level ab initio calculations. The photoelectron spectra provide the vertical/adiabatic detachment energy (VDE/ADE) of the sulfamate anion (SM−) H2N●SO3− at 4.85 ± 0.05 and 4.58 ± 0.08 eV, respectively, and the VDE and ADE of the SM−●SA dimer at 6.41 ± 0.05 and 5.87 ± 0.08 eV, respectively. The significantly increased electron binding energies of the dimer confirm the enhanced electronic stability upon the addition of one SA molecule. The CCSD(T)-predicted VDEs/ADEs agree excellently with the experimental data, confirming the identified structures as the most stable ones. Two types of dimer isomers possessing different hydrogen bonding (HB) motifs are identified, corresponding to SM− binding to a zwitterionic SA (SM−●SAz) and a canonical SA (SM−●SAc), respectively. Two N–H⋯O HBs and one superior O–H⋯O HB are formed in the lowest-lying SM−●SAc, while SM−●SAz has three moderate N–H⋯O HBs, with the former being 4.71 kcal/mol more stable. Further theoretical analyses reveal that the binding strength advantage of SM−●SAc over SM−●SAz arises from its significant contributions of orbital interactions between fragments, illustrating that sulfamate strongly interacts with its parent SA acid and preferably chooses the canonical SA in the subsequent cluster formations. Given the prominent presence of SA, this study provides the first evidence that the canonical dimer model of sulfamic acid should exist as a superior configuration during cluster growth.

A Review on Phytochemical, Biological, and Pharma-cological Effects of Psidium guajava Linn. (Guava)

In today’s time there is a tremendously increased use of herbal products worldwide. Psidium guajava L., commonly known as guava, is an essential tropical food plant with various medicinal properties. It is widely available in many countries, especially in Asian countries it is used as a treatment for many diseases. Each plant part has particular properties to treat diseases. The bioactive constituents extracted from Psidium guajava (P. guajava) include (gallic acid, catechin, rutin, Gallocatechin, vanillic acid, quercetin, p-hydroxybenzoic acid, isoquercitrin, casuarina, pedunculagin dimer isomer, myricetin, morin, luteolin, apigenin, ellagic acid, guanosine B, Quercetin-3-0-β-glucoside, ursolic acid and also essential oils) used for the treatment of diseases like anti-diabetes, anti- hypertension, anti- hyperlipidaemia, anti-cancer, autonomous, neuroprotective, anti-depressant, etc. The goal of this review is to provide up-to-date information on the ethnomedicinal uses, bioactive compounds and pharmacological activity of Psidium guajava with greatest emphasis on its therapeutic potential.

UV-A-Induced Photoisomerization and Photodimerization of Curcumin: An Ion Mobility Mass Spectrometry Study.

Curcumin, the bioactive compound present in spice plant turmeric, has been shown to exhibit selective phototoxic activities toward mammalian cancer cells, and it is being used extensively as a photosensitizer (PS) in photodynamic therapies (PDT). However, so far, the fate of curcumin toward photochemical transformations is not well understood. Here we report our findings of a number of novel photochemical reaction channels of curcumin in water-methanol mixture, like photoisomerization, photodimerization, and photooxidation (H2-loss). The reaction was performed by irradiating the curcumin solution with ultraviolet (UV) light of wavelength 350 nm, which is abundant in the earth's troposphere. Product identification and structure elucidation are done by employing an integrated method of drift tube ion mobility mass spectrometry (DTIMS) in combination with high-performance liquid chromatography (HPLC) and collision-induced dissociation (CID) of the mass-selected molecular ions. Two photoisomers of curcumin produced as a result of trans-cis configurational changes about C═C double bonds in the excited state have been identified, and it has been shown that they could serve as the precursors for formation of isomeric dimers via [2 + 2] cycloaddition and H2-loss products. Comparisons of the experimentally measured collision cross-section (CCS) values of the reactant and product ions obtained by the DTIMS method with those predicted by the electronic structure theory are found to be very effective for the discrimination of the produced photoisomers. The observed photochemical reaction channels are potentially significant toward uses of curcumin as a photosensitizer in photodynamic therapy.

Fused Indacene Dimers.

Polycyclic hydrocarbons consisting of two or more directly fused antiaromatic subunits are rare due to their high reactivity. However, it is important to understand how the interactions between the antiaromatic subunits influence the electronic properties of the fused structure. Herein, we present the synthesis of two fused indacene dimer isomers: s-indaceno[2,1-a]-s-indacene (s-ID) and as-indaceno[3,2-b]-as-indacene (as-ID), containing two fused antiaromatic s-indacene or as-indacene units, respectively. Their structures were confirmed by X-ray crystallographic analysis. 1 H NMR/ESR measurements and DFT calculations revealed that both s-ID and as-ID have an open-shell singlet ground state. However, while localized antiaromaticity was observed in s-ID, as-ID showed weak global aromaticity. Moreover, as-ID exhibited a larger diradical character and a smaller singlet-triplet gap than s-ID. All the differences can be attributed to their distinct quinoidal substructures.

Fused Indacene Dimers

AbstractPolycyclic hydrocarbons consisting of two or more directly fused antiaromatic subunits are rare due to their high reactivity. However, it is important to understand how the interactions between the antiaromatic subunits influence the electronic properties of the fused structure. Herein, we present the synthesis of two fused indacene dimer isomers: s‐indaceno[2,1‐a]‐s‐indacene (s‐ID) and as‐indaceno[3,2‐b]‐as‐indacene (as‐ID), containing two fused antiaromatic s‐indacene or as‐indacene units, respectively. Their structures were confirmed by X‐ray crystallographic analysis. 1H NMR/ESR measurements and DFT calculations revealed that both s‐ID and as‐ID have an open‐shell singlet ground state. However, while localized antiaromaticity was observed in s‐ID, as‐ID showed weak global aromaticity. Moreover, as‐ID exhibited a larger diradical character and a smaller singlet‐triplet gap than s‐ID. All the differences can be attributed to their distinct quinoidal substructures.

Quantitative Analysis of Diubiquitin Isomers Using Ion Mobility Mass Spectrometry.

The diversity of ubiquitin modifications calls for methods to better characterize ubiquitin chain linkage, length, and morphology. Here, we use multiple linear regression analysis coupled with ion mobility mass spectrometry (IM-MS) to quantify the relative abundance of different ubiquitin dimer isomers. We demonstrate the utility and robustness of this approach by quantifying the relative abundance of different ubiquitin dimers in complex mixtures and comparing the results to the standard, bottom-up ubiquitin AQUA method. Our results provide a foundation for using multiple linear regression analysis and IM-MS to characterize more complex ubiquitin chain architectures.

O,S-Acetals in a New Modification of oxo-Friedel–Crafts–Bradsher Cyclization—Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations

This paper presents the use of O,S-acetals in a new modification of the oxo-Friedel-Crafts-Bradsher cyclization. In this reaction, under mild reaction conditions (25 °C), three- and four-ring fused RO-acenes (major) and/or HO(CH2)2S-acenes (minor) are formed, the latter products having never been observed before in this type of cyclization. In this way, two electronically different fluorophores could be obtained in a single cyclization reaction, one of them having strong electron donor properties (+M effect of alkoxy groups) and the other having donor-acceptor properties (+M and -I effects of the HO(CH2)2S-group, Hammett's constants). Further increasing the reaction temperature, HCl concentration or prolonging reaction time, surprisingly, yielded a 2:1 mixture of cis and trans dimeric isomers, as the only products of this cyclization. The DFT calculations confirmed a greater stability of the cis isomer compared to the trans isomer. The formation of unexpected dimeric products and HO(CH2)2S-acenes sheds light on the mechanism of oxo-Friedel-Crafts-Bradsher cyclization, involving competitive O/S atom protonation in strained O,S-acetals and in strain-free side groups of intermediate species.

Hirshfeld and AIM Analysis of the Methylone Hydrochloride Crystal Structure and Its Impact on the IR Spectrum Combined with DFT Study

Herein, the Hirshfeld surfaces analysis of the crystalline methylone hydrochloride was performed in order to analyze NH⋯Cl, CH⋯Cl, and CH⋯O intermolecular interactions and study the formation of the NН2+–Cl− salt fragment in methylone hydrochloride crystal. There are two isomeric dimers with parallel and side-by-side orientation extracted from the crystal packing to model the IR spectrum of the crystalline methylone hydrochloride within the framework of density functional theory (DFT) and B3LYP/6-31G(d,p) method. We have assigned and interpreted all observed IR bands in the experimental spectrum of the 3,4-methylenedioxymethcathinone hydrochloride standard crystal sample that is important for forensic-medical examination. It was shown that intermolecular interactions between the NН2+ and Cl− ionic moieties occur in crystalline samples that confirm the presence of the ionized form of the methylone hydrochloride compound with the NН2+Cl− fragment.

Prediction of the structures and heats of formation of MO2, MO3, and M2O5 for M = V, Nb, Ta, Pa.

Structures for the mono-, di-, and tri-bridge isomers of M2O5 as well as those for the MO2 and MO3 fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. The lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa. The di-bridge isomers were predicted to be composed of MO2+ and MO3- fragments, whereas the mono- and tri-bridge are two MO2+ fragments linked by an O2-. The heats of formation of M2O5 dimers, as well as MO2 and MO3 neutral and ionic species were predicted using the Feller-Peterson-Dixon (FPD) approach. The heats of formation of the MF5 species were calculated to provide additional benchmarks. Dimerization energies to form the M2O5 dimers are predicted to become more negative going down group 5 and range from -29 to -45 kcal mol-1. The ionization energies (IEs) for VO2 and TaO2 are essentially the same at 8.75 eV whereas the IEs for NbO2 and PaO2 are 8.10 and 6.25 eV, respectively. The predicted adiabatic electron affinities (AEAs) range from 3.75 eV to 4.45 eV for the MO3 species and vertical detachment energies from 4.21 to 4.59 eV for MO3-. The calculated MO bond dissociation energies increase from 143 kcal mol-1 for M = V to ∼170 kcal mol-1 for M = Nb and Ta to ∼200 kcal mol-1 for M = Pa. The M-O bond dissociation energies are all similar ranging from 97 to 107 kcal mol-1. Natural bond analysis provided insights into the types of chemical bonds in terms of their ionic character. Pa2O5 is predicted to behave like an actinyl species dominated by the interactions of approximately linear PaO2+ groups.

Rapid determination of key impurities in high purity bisphenol A with reversed phase separation and triple quadrupole mass spectrometry

Liquid chromatography with diode array detection (DAD) or ultraviolet spectroscopic (UV) detection as the most important analytical technique for the accurate quantification of impurities in bisphenol compounds normally requires long analysis time for baseline separation of all components as well as highly concentrated sample solutions for the detection of trace levels. To expand the application possibilities to all stages of polymerisation processes, an easy and robust reversed phase separation for 7 known impurities of bisphenol-A (BPA) including 4-isopropenylphenol and its dimeric isomers, o, p-bisphenol-A and trisphenol was established in this work. The method has been validated for the detection with triple quadrupole mass spectrometry (qqqMS) and DAD. In the investigated concentration range 0.5 – 100 mg/kg, the linearity is verified for both detection techniques. The limit of quantification (LOQ) for each impurity is with 0.5 – 1.5 mg/kg for qqqMS and 15 mg/kg for DAD sufficient for the evaluation of BPA as a raw material for polymerisation processes. The separation time for all impurities is 10 min whereas earlier reported methods need a minimum of 25 to 40 min. In addition the necessary sample concentration of BPA could be reduced to 5 mg/mL compared to existing methods where the sample concentration typically is > 50 mg/mL. For all those reasons the validated method can be efficiently applied for frequent process monitoring. Furthermore, 4 additional impurities were detected and identified. Mainly these are reaction products from the isopropenylphenol structure in combination with confirmed impurities as trisphenol or chroman. The quantification of these structures was established with trisphenol as reference and two structures were detected in all BPA qualities of this study in a concentration range from 20 – 400 mg/kg.

Manifestation of Intermolecular Interactions in the IR Spectra of 2- and 4-Methylmethcathinones Hydrochlorides: DFT Study and Hirshfeld Surfaces Analysis

This paper reports a Hirshfeld surfaces analysis of crystalline 2- and 4-methylmethcathinone (2-MMC and 4-MMC) hydrochlorides to analyze NH∙Cl and CH∙∙∙Cl intermolecular interactions and approve the formation of the NН2+–Cl– salt fragment in both 2-MMC∙HCl and 4-MMC∙HCl crystals. Two isomeric dimers were separated from the corresponding crystal packing to model IR spectra of the crystalline 2-MMC∙HCl and 4-MMC∙HCl species within the framework of density functional theory (DFT) and B3LYP/6-31G(d,p) approach. All observed IR bands were assigned and interpreted in the experimental spectra of the 2-MMC∙HCl and 4-MMC∙HCl standard crystal samples representing an important aspect of the forensic problem solvation. A detailed analysis of the nature of IR spectra for both isomers has shown that intermolecular interactions between the NН2+ and Cl– ionic moieties occur in two crystalline samples. The presence of the ionized form of the 2- and 4-MMC∙HCl compounds with the NН2+Cl– fragment is a key condition for the correct reproduction of the IR spectra when calculating the corresponding dimer structures as a model of a crystalline sample.

Chemical Characterisation, Antioxidant and Antibacterial Activities of Pinus pinaster Ait. and Pinus pinea L. Bark Polar Extracts: Prospecting Forestry By-Products as Renewable Sources of Bioactive Compounds

Agroforestry by-products have gained rising attention in recent years as they represent inexpensive and abundant raw materials that are a source of added-value chemicals, e.g., for food and pharmaceutical applications, as well as for bioenergy generation. Pinus pinaster Ait. bark extracts are consumed worldwide for their cardiovascular benefits, whilst the health potential of Pinus pinea L. bark has not yet been deeply exploited. Therefore, this study highlights the chemical characterisation of Portuguese P. pinaster Ait. and P. pinea L. bark polar extracts, via ultra-high performance liquid chromatography-diode array detection-tandem mass spectrometry (UHPLC-DAD-MSn) analysis, and their antioxidant and antibacterial activities. Quinic acid, an A-type procyanidin dimer isomer, protocatechuic acid, and quercetin were identified for the first time as P. pinea L. bark components. Moreover, this bark demonstrated a higher total content of identified polar compounds than P. pinaster Ait. bark, with quinic acid being the most abundant compound identified. Regarding antioxidant activity, the pine bark polar extracts exhibited strong reducing power and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) radical scavenging effects compared to natural antioxidants. Moreover, the bactericidal actions of pine bark extracts were shown against Staphylococcus aureus and Escherichia coli at a 3.13–25 mg mL−1 range. Globally, these promising insights can boost the sustainable exploitation of P. pinea L. bark, as already occurs with P. pinaster Ait. bark, for the food and biomedical fields.

Электронное строение димеров на основе изомеров фуллерена C-=SUB=-58-=/SUB=- как структурных элементов пленок на поверхности Au

Within the framework of the Hubbard model, the energy spectra of the Cs and C3v isomers of C58 fullerene and dimers based on them are calculated. The obtained curves of the density of electronic states of these systems are compared with the experimental curves of the films, which were obtained by deposition of the Cs and C3v isomers of C58 fullerene on the (1,1,1) gold surface. A comparative analysis of the curves of the density of electronic states shows that in those sites through which a bond is formed between fullerenes, carbon is not in the sp2, but in the sp3 hybridized state.

Electronic Structure of Dimers Based on C-=SUB=-58-=/SUB=- Fullerene Isomers as Structural Elements of Films on the Au Surface

Within the framework of the Hubbard model, the energy spectra of the Cs and C3v isomers of C58 fullerene and dimers based on them are calculated. The obtained curves of the density of electronic states of these systems are compared with the experimental curves of the films, which were obtained by deposition of the Cs and C3v isomers of C58 fullerene on the (1,1,1) gold surface. A comparative analysis of the curves of the density of electronic states shows that in those sites through which a bond is formed between fullerenes, carbon is not in the sp2, but in the sp3 hybridized state. Keywords: fullerene, dimer, energy spectrum, Hubbard model, Hubbard subband, density of electronic states.

A Covalent‐Like Feature of Intermolecular Hydrogen Bonding in Energetic Molecules 3,6‐Dihydrazino‐s‐tetrazine (DHT)

AbstractTo explore how intermolecular hydrogen bond (H‐bond) interactions enhance the density and stability of energetic molecular systems, the intermolecular H‐bonding nature of different dimer isomers derived from a new‐generation ecofriendly energetic molecule, 3,6‐dihydrazino‐s‐tetrazine is studied. First‐principles calculations showed that the critical point of the electron localization function on H‐bonds (H…N) lines increased with the enhancement of the H‐bond strength, confirming that covalent properties of H‐bonds are more important as their strength is stronger. Further energy decomposition analysis indicates that the induced effect accounts for more than 18% of intermolecular interaction attraction terms in planar isomers, reflecting the indispensable covalent‐like feature of H‐bonds in energetic molecular systems. Moreover, molecular orbitals exhibit clear delocalization characteristics penetrating H‐bond regions, which also provide important evidence for covalent‐like features of H‐bonds. These findings provide new insights to further understand and even regulate the insensitivity of energetic materials.

Native disulphide-linked dimers facilitate amyloid fibril formation by bovine milk αS2-casein

Bovine milk αS2-casein, an intrinsically disordered protein, readily forms amyloid fibrils in vitro and is implicated in the formation of amyloid fibril deposits in mammary tissue. Its two cysteine residues participate in the formation of either intra- or intermolecular disulphide bonds, generating monomer and dimer species. X-ray solution scattering measurements indicated that both forms of the protein adopt large, spherical oligomers at 20 °C. Upon incubation at 37 °C, the disulphide-linked dimer showed a significantly greater propensity to form amyloid fibrils than its monomeric counterpart. Thioflavin T fluorescence, circular dichroism and infrared spectra were consistent with one or both of the dimer isomers (in a parallel or antiparallel arrangement) being predisposed toward an ordered, amyloid-like structure. Limited proteolysis experiments indicated that the region from Ala81 to Lys113 is incorporated into the fibril core, implying that this region, which is predicted by several algorithms to be amyloidogenic, initiates fibril formation of αS2-casein. The partial conservation of the cysteine motif and the frequent occurrence of disulphide-linked dimers in mammalian milks despite the associated risk of mammary amyloidosis, suggest that the dimeric conformation of αS2-casein is a functional, yet amyloidogenic, structure.

Twisted-Planar-Twisted expanded porphyrinoid dimer as a rudimentary reaction-based methanol indicator

Directly linked porphyrin dimers have attracted considerable attention because of their intriguing electronic features. Most emphasis has been placed on either dimers with large dihedral angles between the constituent planar monomeric subunits or those with overall planarity, referred to as “Planar-Twisted-Planar” and “Planar-Planar-Planar”, respectively. Herein, we report a “Twisted-Planar-Twisted” framework, the hexaphyrin dimer D that exists in a trans configuration. Treatment of D with MeOH affords two isomeric dimers, MD1 and MD2, both of which incorporate a methoxy moiety and exist in cis orientations with respect to the tethering linkage. The methanol-promoted conversion is accompanied by a readily discernible color change from green to brown and is not induced to an appreciable level by other alcohols. Dimer D thus acts as a rudimentary, albeit highly selective, reaction-based methanol indicator. This work provides a promising approach for constructing reaction-based chemosensors using porphyrinoid dimers of nonplanar subunits with biased reactivity.