Acceptor Moieties Research Articles

Planar Chiral Charge-Transfer Cyclophanes: Convenient Synthesis, Circularly Polarized Light-Responsive Photothermal Conversion and Supramolecular Chiral Assembly.

We report herein a series of macrocycles in which the densely π-stacked charge-transfer (CT) donor/acceptor with naphthalenediimides (NDIs) or perylene diimide (PDI) as acceptor moiety pairing various donor moieties are locked by covalent bond. The X-ray crystallography of C8BDT-NDI reveals a short intramolecular π-stacking distance around 3.4 Å and the existence of intermolecular donor/acceptor π-stacking (3.7 Å). The intramolecular CT is highly dependent on the electron-donating ability of donor moiety and replacing carbazole (C8KZ) with benzo[1,2-b:4,5-b']dithiophene (C8BDT) or dihydroindolo[3,2-b]indole (C8DN) redshift CT absorption into NIR region. Notably, both C8BDT-NDI and C8DN-NDI demonstrate excellent photothermal performance, which is a result of the active non-radiative pathways. Interestingly, the different molecular symmetry between donor and acceptor moiety in cyclophanes endow C8BDT-NDI and C8DN-NDI with intrinsic planar chirality. The enantiomeric C8BDT-NDI shows chiral selectivity for incident light, i.e., when irradiated by left-circularly polarized light, (R)-C8BDT-NDI is more sensitive and a higher maximum stable temperature is achieved. While, enantiomeric C8DN-NDI pack with different orientations forming M- and P-handedness helix, respectively, demonstrating molecular planar chirality being transferred and amplified through molecular assembly. These results provide insight into the intramolecular charge transfer in enforced D/A π-stacks in which CT interactions and planar chirality would be engineered through structural control.

Photovoltaic response promoted via intramolecular charge transfer in triphenylpyridine core with small acceptors: A DFT/TD-DFT study

Currently, A−π−A configured molecules (TTP1-TTP6) were designed from the reference compound (TPPR) by modifying the terminal acceptors for photovoltaic materials. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using the M06/6-311G(d,p) functional were employed to analyze the photonic and electronic properties of the newly designed derivatives. Various analyses; frontier molecular orbitals (FMOs), density of states (DOS), absorption spectra (λmax), transition density matrix (TDM), binding energy (Eb), hole-electron and open circuit voltage (Voc) were performed to explore the photovoltaic properties of triphenylpyridine based compounds. The structural modulation with acceptor moieties significantly tuned their HOMO and LUMO levels, resulting in reduced band gaps (2.833–3.037 eV). They also exhibited broader absorption spectra (λmax) ranging from 482.560 to 514.756 nm as compared to the reference compound (486.289 nm). Notably, TPP3 showed the good photovoltaic response as it displayed the least energy gap (2.833 eV) with lower binding energy (0.415 eV) and bathochromic shift (512.798 nm) in absorption spectra as compared to all other derivatives. Beside this, a comparative study with spiro-OMeTAD and P3HT standard hole transport materials illustrated that these materials can also be utilized as effective photovoltaic materials.

Mechanism of Solid-State 1H Photochemically Induced Dynamic Nuclear Polarization in a Synthetic Donor-Chromophore-Acceptor at 0.3 T.

1H photochemically induced dynamic nuclear polarization (photo-CIDNP) has recently emerged as a tool to enhance bulk 1H nuclear magnetic resonance (NMR) signals in solids at magnetic fields ranging from 0.3 to 21.1 T, using synthetic donor-chromophore-acceptor (D-C-A) molecules as optically active polarizing agents (PAs). However, the mechanisms at play for the generation of spin polarization in these systems have not been determined but are essential for an in-depth understanding and further development of the process. Here, we introduce site-selective deuteration to identify the 1H photo-CIDNP mechanisms at 85 K and 0.3 T in D-C-A molecule PhotoPol. We find that the protons on the acceptor moiety are essential for the generation of polarization, establishing differential relaxation as the main mechanism. These results establish selective deuteration as a tool to identify and suppress polarization transfer mechanisms, which opens up pathways for further optimization of the optical PA at both low and high magnetic fields.

Interacting Emission Species among Donor and Acceptor Moieties in a Donor-Grafted Polymer Host/TADF-Guest System and Their Effects on Photoluminescence and Electroluminescence.

Thermally activated delayed fluorescence (TADF)-based electroluminescence (EL) devices adopting a host/guest strategy in their emitting layer (EML) are capable of realizing high efficiency. However, TADF emitters composed of donor and acceptor moieties as guests dispersed in organic host materials containing a donor and/or an acceptor are subject to donor-acceptor (D-A) interactions. In addition, electron delocalization between neighboring emitter molecules could form different species of aggregates. Here, we investigate the effects of intermolecular interacting emission species on the optoelectronic properties of sky-blue/green/red (sB/G/R) TADF emitters as guests using poly(biphenyl-Si/Ge) grafted with various donor moieties as hosts. We found the presence of guest/guest exciplex (Dg/Ag)*, host/guest exciplexes (Dh/Ag)*, and aggregates through the exploration of interactions between neighboring TADF guest molecules and between host and TADF-guest molecules. The nonradiative 3(Dh/Ag)* (ΔEST ≈ 0.5 eV) could increase the internal conversion rate (kIC) and reduce delayed luminescence, and both of them could cause a decrease in PLQY. The luminescence of 3(Dh/Ag)* may have a positive or negative effect on PLQY depending on its triplet energy. As the singlet and triplet energies of (aggregate)* are lower than those of (ICT)*, energy transfer from (ICT)* to (aggregate)* could occur. The low PLQY nature of (aggregate)* means that it is more likely to cause quenching in device emission. The emissions from (Dh/Ag)* and (aggregate)* are found to have increased full width at half-maximum and lead to lower emission color purity. Such intermolecular interactions should also occur in host/guest (TADF) systems and nondoped TADF emitter systems and thus are important factors for the molecular design of the TADF emitter and/or its accompanying host for high device efficiency and emission color purity.

Enhancing perovskite solar cells performance through tailored design: pyridine-functionalized phenothiazine derivatives with modified end-capped acceptor moieties

Abstract Future energy resources are being developed using clean and renewable energies since these sources offer environmentally friendly and sustainable choices to traditional sources like fossil fuels. Among various renewable energy sources, solar energy is becoming increasingly efficient with advancements in organic photovoltaic systems. Organic semiconductor materials, which require high electron affinity and possess desirable optical and electronic properties, are crucial for these systems. Researchers are constantly trying to increase the role of photovoltaic materials in optoelectronic applications. With current energy demands, there is a shift from traditional solar cells to perovskite photovoltaic materials due to their significant contributions to renewable energy. Therefore, we have designed a new stream of donor- π -acceptor (D- π -A) type pyridine functionalized phenothiazine derivates-based donor materials, resulting in nine fabricated HTMs (PT1-PT9), by substituting the terminals with thiophene and acceptors moieties respectively to enhance the photovoltaic properties of perovskite solar cells (PSCs). All newly proposed materials were computationally examined to estimate their optoelectronics, geometrical, and photovoltaic properties using quantum chemical approach, and then compared to the reference. For organic hole-transporting materials, a heterocyclic phenothiazine core (PTZ) has been proven effective as it has feasible structure modifications, excellent electron-donating properties, and straightforward synthesis. The study of electronic parameters (density of state, frontier molecular orbitals, and electrostatic potential ESP), optical properties (light harvesting efficiency, absorption maxima, dipole moment, and first excitation energies) and charge transfer characteristics (electron–hole overlap, transition density matrix) of designed materials revealed that there is an increase in absorption range under the influence of terminal acceptor groups, with lowering the bandgap values compared to the reference. A density of state (DOS) graph and HOMO–LUMO schema are evidence of the electron-withdrawing effect of acceptor moieties. Transition density matrix (TDM) analysis proves reliable charger transfer in designed molecules. Reorganization energy values for designed molecules are lower than the reference making charge transfer carriers more efficient. Additionally, solvation-free energy values (−17.28 to −33.19 Kcalmol−1) and higher dipole moments suggest better surface-wetting and solubility properties. In general, the fabricated materials have exceptional charge mobilities with higher absorption and reduced band gap values that make them suitable and stable candidates for photovoltaic devices.

Planar Chiral Charge‐Transfer Cyclophanes: Convenient Synthesis, Circularly Polarized Light‐Responsive Photothermal Conversion and Supramolecular Chiral Assembly

We report herein a series of macrocycles in which the densely π‐stacked charge‐transfer (CT) donor/acceptor with naphthalenediimides (NDIs) or perylene diimide (PDI) as acceptor moiety pairing various donor moieties are locked by covalent bond. The X‐ray crystallography of C8BDT‐NDI reveals a short intramolecular π‐stacking distance around 3.4 Å and the existence of intermolecular donor/acceptor π‐stacking (3.7 Å). The intramolecular CT is highly dependent on the electron‐donating ability of donor moiety and replacing carbazole (C8KZ) with benzo[1,2‐b:4,5‐b']dithiophene (C8BDT) or dihydroindolo[3,2‐b]indole (C8DN) redshift CT absorption into NIR region. Notably, both C8BDT‐NDI and C8DN‐NDI demonstrate excellent photothermal performance, which is a result of the active non‐radiative pathways. Interestingly, the different molecular symmetry between donor and acceptor moiety endows C8BDT‐NDI and C8DN‐NDI with intrinsic planar chirality. The enantiomeric C8BDT‐NDI shows chiral selectivity for incident light, i.e., when irradiated by left‐circularly polarized light, (R)‐C8BDT‐NDI is more sensitive and a higher maximum stable temperature is achieved. While, enantiomeric C8DN‐NDI pack with different orientations forming M‐ and P‐handedness helix, respectively, demonstrating molecular planar chirality being transferred and amplified through molecular assembly. These results provide insight into the intramolecular charge transfer in enforced D/A π‐stacks in which CT interactions and planar chirality would be engineered through structural control.

Exploring the interaction between derivatives of urea with resorcinol-based acridinedione dyes by employing fluorescence methods and molecular docking approach

Akyl urea derivatives, either symmetrical or unsymmetrical in nature possessing a free N-H or N-alkyl moieties in the molecular framework of urea governs the excited state properties of acridinedione dye (ADR1) which is a resorcinol-based derivative. Fluorescence enhancement (FE) of ADR1 dye is observed on the addition of unsymmetrical urea derivatives, whereas a decrease in the fluorescence intensity resulted upon the addition of symmetrical urea derivatives. The nature of the urea derivatives controls the suppression of photoinduced electron transfer (PET) via space, which is the cause of the FE. FQ results from the donor and acceptor moieties of ADR1 dye promoting the PET process. Urea (U), symmetrical and unsymmetrical urea derivatives (except Tetramethyl urea (TMU)) results no significant shift of the localized excited (LE) state emission of ADR1 dye. Studies of the ADR1 dye’s fluorescence lifetime in the presence of urea compounds show a significant increase in lifetime. This phenomenon is explained by a significant difference in the hydrogen-bonding (HB) pattern, which causes variationin the microenvironment created by thesolute molecules in the aqueous phase. Both the hydrophobic effects of the alkyl group substituents in the urea molecular framework and the HB interactions between the solute and solvent influence the excited state features of ADR1 dye. Further, the role of urea derivatives and ADR1 dye (both are considered as competitive guest molecules) energetics and molecular interactions were studied in the presence of host molecule, Human Serum Albumin (HSA). The binding energy (BE) and several bimolecular interactions driven by urea derivatives in the presence of ADR1-HSA complex in comparison with that of urea derivatives-HSA complex were investigated by molecular docking (Mol.Doc) methodology. Incorporating theoretical research along withsteady state and time-resolved fluorescence investigations proved to be an effective method to evaluate the interactions of competing solutes comprising bothhydrophobic and HB functional groups.

Influence of terminal moiety on PCE of DSSCs: An In Silico study based on triazatruxene-benzothiadiazole dye

Our study utilized an experimentally synthesized dye as a reference molecule, employing a donor-π linker-acceptor (D-π-A) framework for organic solar cells. The molecule featured a triazatruxene group linked with alkyl branches as the donor and ethynyl benzoic acid as the acceptor, connected through a derivative of benzothiadiazole as the π linker. To improve optoelectronic and photovoltaic properties, ten theoretically designed dyes (ZA1–ZA10) are proposed, differing from the reference (R) by modifying the terminal acceptor moiety. Various quantum analyses, including frontier molecular orbitals, optical properties, reorganization energies, binding energies, transition density matrices (TDM), molecular electrostatic potential (MEP), dipole moment, and density of states were carried out at DFT/B3LYP/6-31G(d,p). Ground state geometries revealed a co-planar morphology in ZA1–ZA10, facilitating efficient charge transportation. TDM and MEP illustrated improved electronic transitions in the excited states. Computational analyses revealed superior photovoltaic properties of ZA1–ZA10. Notably, ZA5 exhibited the most significant redshift (1021 nm) in absorption, lowest bandgap (1.44 eV), smallest transition energy (1.21 eV), least binding energy (0.23 eV), and improved charge mobilities. Results from the adsorption of ZA1-ZA10 on the TiO2 layer confirmed their anchoring potential and effective injection of electrons to anatase (TiO2)9. These significant outcomes promise the potential and novelty of our designed dyes for higher power conversion efficiencies (PCE) in dye-sensitized solar cells (DSSCs).

B3H3Be ← F-: A Case of Extremely Strong Dative Bond.

Chemical bonding has attracted chemists since its inception. Dative bonding between a donor and acceptor moiety is also an important phenomenon, which results in stabilization of many chemical compounds. Herein, we show that an extremely strong dative bond is possible between a fluoride ion and a beryllium center which is a part of a half-sandwich complex, B3H3Be. Quantum chemical calculations have shown the possibility of formation of a half-sandwich complex of Be with a B3H32- ring. Calculations reveal that the complex is stable toward dissociation. The half-sandwich complex features a very low-lying lowest unoccupied molecular orbital (LUMO) concentrated on the Be atom, thereby indicating a Lewis acidic character of the complex. This lower-lying LUMO at the beryllium center is responsible for forming an extremely strong dative bond with the fluoride donor.

Exploring Spectral and Electrochemical Behavior of Hydroxy‐N‐Benzylideneanilines by Integrated Theoretical and Experimental Approaches

ABSTRACTThe present work explored the effect of –OH group substitution (o/p) on the spectral and electrochemical behavior of N‐benzylideneaniline. The geometry optimization of unsubstituted and (o/p)‐OH‐substituted analogs revealed the coplanarity of the molecules. The vibrational spectra of the compounds were computed using density functional theory (DFT) and compared with the experimental data. The observed bands were assigned based on total energy distribution (TED). Predicted electronic absorption spectra from time‐dependent density functional theory (TD‐DFT) calculation were compared with the UV–visible spectra of the molecules. The analysis of the lowest spin‐allowed (singlet‐singlet) excited states divulged possible electronic transition. The o‐substituted benzylideneaniline possessed the lowest highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap among the substituted and unsubstituted analogs. The intramolecular contacts were interpreted using natural bond orbital and localized molecular orbital analysis. The –CH=N– linkage was investigated as a bridge for the electron delocalization from the donor to acceptor moieties. The manifestation of a reduction peak in the cyclic voltammetric studies confirmed the electrochemical behavior in the –OH‐substituted molecule, which was diffusion‐controlled. The discrepancy in the electrochemical property concerning the position of the –OH substituent of the candidate molecules was put forward.

Effect of Electron-Donating Substituents and an Electric Field on the ΔEST of Selected Imidazopyridine Derivatives: A DFT Study.

A series of thermally activated delayed fluorescent (TADF) molecules having an imidazopyridine acceptor, a benzene linker, and a 9,9-dimethyl-9,10-dihydroacridine donor are designed and examined using a quantum chemical approach. The above framework spatially separates the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), minimizing their overlap, ultimately resulting in a reduced energy gap between the excited singlet and triplet states (ΔEST). The impact of electron-donating substituents (-Me, -Et, -t-Bu, -OMe, and -NMe2) on the donor moiety of the parent molecule 2-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)imidazo[1,2-a]pyridine-3,6-dicarbonitrile (Ac-CNImPy) is investigated. The calculated results revealed that for a given substituent, the para-substituted derivatives exhibit relatively less ΔEST, compared to that of the respective ortho- and meta derivatives. The value of ΔEST decreased with an increase in the electron-donating capacity of the substituent. Additionally, the ΔEST of the disubstituted derivatives is found to be less than that for the monosubstituted derivatives. The charge transport studies revealed that molecules with strong electron-donating substituents act as electron transporters. The effect of an external electric field (EEF) on ΔEST of the parent molecule Ac-CNIMPY and its derivative is also examined and revealed that the ΔEST can be further reduced by applying an electric field of appropriate strength in a direction perpendicular to the dipole moment of the molecule and in the plane of the acceptor moiety.

Tailoring Diversified Peripheral Anchor Groups in Spirofluorene‐Dithiolane‐Based Hole Transporting Materials for Efficient Organic and Perovskite Solar Cells from First‐Principle

AbstractThis quantum mechanical approach recommends push–pull molecular engineering to fabricate hole‐transporting materials (HTMs) for photovoltaic cells. It integrates acceptor moieties via thiophene to fluorene core, resulting in five novel HTMs (SFD‐1 to SFD‐5). The results exhibit that derivative HTMs show excellent coherence in excitation, dispersion, and transportation of charge carriers, ensuring robust hole mobility. The anchor moieties functionalized HTMs unveil excellent band alignment with perovskite with fitting HOMO energy levels (−4.93–−5.35 eV), less optical absorption in visible portion ( < 520). This acceptor integration has improved the hole mobility in derivatives, accredited to the smaller hole reorganization energy (0.14–0.68 eV), and greater hole transfer integral (0.22–0.33 eV). The transition density matrix analysis exhibited robust electronic coupling, subtler charge carrier overlapping and greater charge transfer length (7.48–13.73 Å). This resulted in an excellent upsurge in intrinsic charge transference (70.75–92.70%) and smaller exciton binding energy, leading to easier exciton dissociation, and fewer recombination fatalities. However, an adequate variation in dipole moment (4.04 D to 16.34 D) and Gibbs solvation‐free energy (−18.06 to −21.89 kcal mol−1) ensures facile film formation and processability. In conclusion, this approach recommends these flourene‐based HTMs are highly desireable for forthcoming solar cell technology.

Boron cluster-based TADF emitter via through-space charge transfer enabling efficient orange-red electroluminescence

Thermally activated delayed fluorescence (TADF) materials driven by a through-space charge transfer (TSCT) mechanism have garnered wide interest. However, access of TSCT-TADF molecules with long-wavelength emission remains a formidable challenge. In this study, we introduce a novel V-type D-A-D-A' emitter, Trz-mCzCbCz, by using a carborane scaffold. This design strategically incorporates carbazole (Cz) and 2,4,6-triphenyl-1,3,5-triazine (Trz) as donor and acceptor moieties, respectively. Theoretical calculations alongside experimental validations affirm the typical TSCT-TADF characteristics of this luminogen. Owing to the unique structural and electronic attributes of carboranes, Trz-mCzCbCz exhibits an orange-red emission, markedly diverging from the traditional blue-to-green emissions observed in classical Cz and Trz-based TADF molecules. Moreover, bright emission in aggregates was observed for Trz-mCzCbCz with absolute photoluminescence quantum yield (PLQY) of up to 88.8%. As such, we have successfully fabricated five organic light-emitting diodes (OLEDs) by utilizing Trz-mCzCbCz as the emitting layer. It is important to note that both the reverse intersystem crossing process and the TADF properties are profoundly influenced by host materials. The fabricated OLED devices reached a maximum external quantum efficiency (EQE) of 12.7%, with an emission peak at 592 nm. This represents the highest recorded efficiency for TSCT-TADF OLEDs employing carborane derivatives as emitting layers.

DFT/TDDFT Investigation of the Effect of Electron Acceptor Groups on Photovoltaic Performance Using Phenothiazine‐Based D‐Ai‐π‐A Dyes for DSSC Applications

AbstractThis review focuses mostly on organic dye‐sensitized solar cells, as they are an attractive, environmentally friendly alternative to traditional silicon solar cells for the production of renewable energy at a lower cost. The dye chromophore is recognized as the central component of the DSSC device. To improve the electrochemical, photovoltaic, and absorption properties of organic sensitizing dyes, we have designed a series of eight new dyes Pi (i = 1.8) based on the DPA‐2 architecture (the reference molecule). We have investigated the effects of internal absorption of different acceptor groups in D‐Ai‐π‐A before and after binding to the TiO2 cluster surface on the ability to inject electrons into the surface. The benzophenothiazine is the D donor, the π‐spacer is furan, and the A acceptor is cycnoacrylic acid. We are using time‐dependent density functional theory (TD‐DFT), and density functional theory (DFT) in our quantum calculations. It is theoretically possible to predict suitable candidates for the DSSC device and identify correlations between their structure and properties by using DFT and TD‐DFT simulations to thoroughly study in detail electronic structures, natural binding orbital (NBO), analysis of UV‐visible absorption spectra, parameters influencing short‐circuit current density (JSC), open‐circuit voltage (VOC), and intramolecular charge transfer (ICT). Additionally, the relationship between optoelectronic properties and molecular structure was investigated, and the effect of auxiliary acceptor groups (Ai) on the primary photovoltaic properties of the reference molecule DPA‐2. The results show that by changing the internal acceptor to DPA‐2 could create a more coplanar and rigid structure. This would cause the energy gap (Eg) for each of the dyes created to significantly shrink, reducing it from 2.29 to 1.38 eV. The absorption spectra's λmax for each dye would also change color, this was because the acceptor moiety Ai of the phenothiazine moiety changed when it came to DPA‐2 (not including compounds P1 and P4). In contrast, P6 and P7 dyes demonstrate an absorption range beyond 500 nm, implying a more efficient utilization of sunlight in the visible spectrum compared to other dyes. Furthermore, all organic dyes show a robust LHE performance (0.919 to 0.993), correlating with the lowest ΔGreg values (0.097 to 0.356) and the most negative ΔGinject values (−2.067 to −1.121). The power conversion efficiency of PCE and JSC could increase according to these results. Therefore, theoretical research into adding a second internal acceptor group to the D‐Ai‐π‐A structure should produce new methods for improving solar energy output.

Analysing the self-assembly modes in chiral multi-component gels based on donor and acceptor moieties

ABSTRACT The role of the structural similarity in the individual components on the self-assembly process of multi-component systems was studied by analysing the gelation properties of chiral multi-component gels with structurally similar (enantiomers) and non-similar donor or acceptor moieties. The gelation properties of the individual enantiomers, mixed enantiomers, and mixed chiral donor-acceptor compounds were analysed in various solvents. Analysis of the mechanical strength revealed that the mixed chiral gels were stronger compared to other gels in mesitylene; however, a reverse trend was observed for thermal stability. Scanning electron microscopy (SEM) of the dried gels of the mixed enantiomeric and mixed chiral donor-acceptor gels showed morphological changes indicating different self-assembly modes. Powder X-ray analysis revealed that a co-assembled mode was observed for the mixed gels with structurally similar components. However, a self-sorting nature was observed for the mixed chiral donor-acceptor gel, and the charge transfer interaction between the donor and acceptor played a major role in the self-assembly of these mixed gels. We performed computational studies to predict the electronic distribution in the individual chiral molecules. These results demonstrate that altering the structural features of the individual components is one of the key parameters that control the self-assembly modes of multi-component systems.

(SiFA)SeFe: A Hydrophilic Silicon-Based Fluoride Acceptor Enabling Versatile Peptidic Radiohybrid Tracers.

The radiohybrid (rh) concept to design targeted (and chemically identical) radiotracers for imaging or radionuclide therapy of tumors has gained momentum. For this strategy, a new bifunctional Silicon-based Fluoride Acceptor (SiFA) moiety (SiFA)SeFe was synthesized, endowed with improved hydrophilicity and high versatility of integration into rh-compounds. Preliminary radiolabeling and stability studies under different conditions were conducted using model bioconjugate peptides. Further, three somatostatin receptor 2 (sstR2)-targeted rh-compounds ((SiFA)SeFe-rhTATE1-3, TATE = (Tyr3)-octreotate) were developed. Compound (SiFA)SeFe-rhTATE3, enables labeling with 18F for PET imaging or chelation of 177Lu for therapy. The rh-compounds possess comparable receptor binding affinity and in vitro performance as good as the clinically proven gold standards. SstR2-specificity was further shown for (SiFA)SeFe-rhTATE2 using the chicken chorioallantoic membrane (CAM) model. The biodistribution of two compounds in mice showed high accumulation in tumors and excretion via the kidneys, demonstrating the clinical applicability of the (SiFA)SeFe moiety.

Synthesis of model heterojunction interfaces reveals molecular-configuration-dependent photoinduced charge transfer

Control of the molecular configuration at the interface of an organic heterojunction is key to the development of efficient optoelectronic devices. Due to the difficulty in characterizing these buried and (probably) disordered heterointerfaces, the interfacial structure in most systems remains a mystery. Here we demonstrate a synthetic strategy to design and control model interfaces, enabling their detailed study in isolation from the bulk material. This is achieved by the synthesis of a polymer in which a non-fullerene acceptor moiety is covalently bonded to a donor polymer backbone using dual alkyl chain links, constraining the acceptor and donor units in a through space co-facial arrangement. The constrained geometry of the acceptor relative to the electron-rich and -poor moieties in the polymer backbone can be tuned to control the kinetics of charge separation and the energy of the resultant charge-transfer state giving insight into factors that govern charge generation at organic heterojunctions.

Molecular engineering push-pull structural versatility in the triphenylamine-thienodioxine-based hole transporting materials for high-performance organic and perovskite solar cells

This study proposes a push-pull molecular engineering approach to fabricate versatile hole-transporting materials (HTMs) for photovoltaic cells. Herein, we introduce a D-π-A strategy for fabricating four highly functional small molecules of thienodioxine core-based HTMs (CJ06C1 to CJ06C4), via core functionalization with diversified electron-withdrawing acceptor moieties. The engineered HTMs are evaluated by employing quantum calculations to analyze the structure-property relationships from optoelectronic, electrochemical, and solvability attributes. The findings reveal that acceptor-integrated HTMs unveil excellent band alignment with active perovskite layer with deeper HOMO energy levels (-4.96 eV to 5.02 eV), transparency in the visible portion λmaxabs<521, which entail appropriate photophysical attributes. In comparison to the reference HTM (CJ06), the acceptor-integrated HTMs have exhibited potentially higher hole mobility rate, accredited to smaller hole reorganization energies (0.15 eV to 0.21 eV), greater transfer integral values (0.26 eV to 0.31 eV) and greater hole hopping rates (1.08×1028 S−1 to 3.70×1028 S−1). The electron-excitation investigation exhibited stronger electronic coupling, smaller hole-electron spatial overlapping, and higher charge transference length (19.42 Å to 21.14 Å) in the fabricated HTMs. Thus ensued a significant upsurge in intrinsic charge transference (74.22–99.74 %) and lower exciton binding energies, leading to easy charge dissociation and low recombination chances compared to the parent HTM (CJ06C1). Moreover, the findings from dipole moments (12.56 D to 13.05 D) and solvation-free energy (-91.08 kJ/mol) to −108.1 kJ/mol),imply easier processability and aptness for film formation. Overall, this study ensures the efficiency of thienodioxine core functionalization with acceptor moieties for fabricating state-of-the-art HTMs. The promising attributes of fabricated HTMs pave the way for forthcoming perovskite solar cells.

Hydrogen Bond Strengthens Acceptor Group: The Curious Case of the C-H···O=C Bond.

An H-bond involves the sharing of a hydrogen atom between an electronegative atom to which it is covalently bound (the donor) and another electronegative atom serving as an acceptor. Such bonds represent a critically important geometrical force in biological macromolecules and, as such, have been characterized extensively. H-bond formation invariably leads to a weakening within the acceptor moiety due to the pulling exerted by the donor hydrogen. This phenomenon can be compared to a spring connecting two masses; pulling one mass stretches the spring, similarly affecting the bond between the two masses. Herein, we describe the opposite phenomenon when investigating the energetics of the C-H···O=C bond. This bond underpins the most prevalent protein transmembrane dimerization motif (GxxxG) in which a glycine Cα-H on one helix forms a hydrogen bond with a carbonyl in a nearby helix. We use isotope-edited FT-IR spectroscopy and corroborating computational approaches to demonstrate a surprising strengthening of the acceptor C=O bond upon binding with the glycine Cα-H. We show that electronic factors associated with the Cα-H bond strengthen the C=O oscillator by increasing the s-character of the σ-bond, lowering the hyperconjugative disruption of the π-bond. In addition, a reduction of the acceptor C=O bond's polarity is observed upon the formation of the C-H···O=C bond. Our findings challenge the conventional understanding of H-bond dynamics and provide new insights into the structural stability of inter-helical protein interactions.

From Coordination to π‐Hole Chemistry of Transition Metals: Metalloporphyrins as a Case of Study

AbstractHerein we have evidenced the formation of favorable π‐hole Br⋅⋅⋅metal noncovalent interactions (NCIs) involving elements from groups 9, 11 and 12. More in detail, M (M=Co2+, Ni2+, Cu2+ and Zn2+) containing porphyrins have been synthesized and their supramolecular assemblies structurally characterized by means of single crystal X‐ray diffraction and Hirshfeld surface analyses, revealing the formation of directional Br⋅⋅⋅M contacts in addition to ancillary hydrogen bond and lone pair‐π bonds. Computations at the PBE0‐D3/def2‐TZVP level of theory revealed the π‐hole nature of the Br⋅⋅⋅M interaction. In addition, the physical nature of these NCIs was studied using Quantum Chemistry methodologies, providing evidence of π‐hole Spodium and Regium bonds in Zn2+ and Cu2+ porphyrins, in addition to unveiling the presence of a π‐hole for group 9 (Co2+). On the other hand, group 10 (Ni2+) acted as both electron donor and acceptor moiety without showing an electropositive π‐hole. Owing to the underexplored potential of π‐hole interactions in transition metal chemistry, we believe the results reported herein will be useful in supramolecular chemistry, organometallics, and solid‐state chemistry by i) putting under the spotlight the π‐hole chemistry involving first row transition metals and ii) unlocking a new tool to direct the self‐assembly of metalloporphyrins.