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This work proposes a methodology to increase the open‐circuit voltage of perovskite solar cells via modulating the buried interface using π‐conjugated molecules, featuring a push‐pull electronic structure configuration. In the planar perovskite solar cells using tin oxide nanocrystal as an electron transport layer, the 2‐methyl‐1‐aminobenzene derivatives with 4‐(Heptafluoropropan)‐2‐methylaniline notable not only reduce the interfacial energy barrier but also passivate the defects at the buried interface. This modulation enhances the open circuit voltage of Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 (bandgap ≈1.60 eV) perovskite solar cell to a high value of 1.241 V and thus the power conversion efficiency to 24.16% under standard testing condition. An even higher efficiency of 25.11% can be achieved when employing in the Cs0.05MA0.05FA0.9PbI3 (bandgap ≈1.54 eV) perovskite solar cell. The open circuit voltage (1.241 V) is among the highest in triple‐cation perovskite solar cells which reaches 95% Shockley–Queisser limit. A solar‐to‐CO conversion efficiency of 11.76% can be achieved in the fabricated perovskite solar minimodule driven carbon dioxide electrolyzer. This demonstrates the potential of utilizing perovskite solar cells for CO2 conversion as a clean and green energy environment. [ABSTRACT FROM AUTHOR]

A method for the synthesis of two branched π-conjugated polyynes was proposed. The electron absorption, photoluminescence (PL) emissions, and electrochemiluminescence (ECL) properties of the prepared polyynes were further investigated. PL emissions from both chromophores were observed in the visible region of 320–500 nm. Both two polyynes exhibited stable cathode ECL emission, which can be used to design and preparation of functional materials in the future. [ABSTRACT FROM AUTHOR]

Molecular chirality plays a pivotal role across the disciplines of chemical and physical sciences, as well as holding significant implications in the realms of medicine and technology. Chiral macrocycles have attracted recent interests in synthetic chemistry, material science, and supramolecular chemistry. Due to the cyclic arrangements of stereogenic elements or special orientations confined in the rigid structures, π‐conjugated chiral macrocycles are expected to be highly luminescent, and configurationally stable, and thus serve to develop high‐performance chiroptical materials. Given the rapid progress achieved in this new area in recent years, it is significant to highlight new concepts and breakthroughs. This minireview will offer the overview of a wide range of π‐conjugated chiral macrocycles from traditional molecules which include the axially, helically, and planar chiral skeletons to the new chiral nanobelts with a focus on the structure‐function relationship between chiral molecules and the unique chiroptical properties. [ABSTRACT FROM AUTHOR]

Combining π‐conjugated and non‐π‐conjugated groups is an important strategy for synthesizing new nonlinear optical (NLO) crystals. However, the second harmonic generation (SHG) response and optical anisotropy can be limited by improper spatial alignment of these functional groups in the crystal structure. In this work, it is revealed that non‐π‐conjugated [NH2SO3] group acts as both hydrogen bond donor and acceptor, effectively regulating the 2D planar structure formed by π‐conjugated [C4N3H6] groups. The resulting organic–inorganic hybrid crystal C4N3H6SO3NH2 exhibits a strong SHG response (2.5 × KDP), large optical anisotropy (0.233@546 nm), and blue‐violet and green fluorescence near 360 and 520 nm, respectively. This work expands the methodology for creating new NLO crystals through organic–inorganic hybridization, while also showcasing the potential of C4N3H6SO3NH2 as a multifunctional optical material. [ABSTRACT FROM AUTHOR]

We theoretically investigated the nitrogen substitution effect on the molecular structure and π-electron delocalization in linear nitrogen-substituted polycyclic aromatic hydrocarbons (N-PAHs). Based on the optimized molecular structures and magnetic field-induced parameters of fused bi- and tricyclic linear N-PAHs, we found that the local π-electron delocalization of subcycles (e.g., mono- and bicyclic constituent moieties) in linear N-PAHs is preserved, despite deviation from ideal structures of parent monocycles. The introduction of a fused five-membered ring with a pyrrolic N atom (N-5MR) in linear N-PAHs significantly perturbs the π-electronic condition of the neighboring fused six-membered ring (6MR). Monocyclic pyrrole exhibits substantial bond length alternations, strongly influencing the π-electronic systems of both the fused N-5MR and 6MR in linear N-PAHs, depending on the location of shared covalent bonds. A fused six-membered ring with a graphitic N atom in an indolizine moiety cannot generate monocyclic π-electron delocalization but instead contributes to the formation of polycyclic π-electron delocalization. This is evidenced by bifurcated diatropic ring currents induced by an external magnetic field. In conclusion, the satisfaction of Hückel's 4n + 2 rule for both mono- and polycycles is crucial for understanding the overall π-electron delocalization. It is crucial to consider the unique characteristics of the three types of substituted N atoms and the spatial arrangement of 5MR and 6MR in N-PAHs. [ABSTRACT FROM AUTHOR]

Abstract Combining π‐conjugated and non‐π‐conjugated groups is an important strategy for synthesizing new nonlinear optical (NLO) crystals. However, the second harmonic generation (SHG) response and optical anisotropy can be limited by improper spatial alignment of these functional groups in the crystal structure. In this work, it is revealed that non‐π‐conjugated [NH2SO3] group acts as both hydrogen bond donor and acceptor, effectively regulating the 2D planar structure formed by π‐conjugated [C4N3H6] groups. The resulting organic–inorganic hybrid crystal C4N3H6SO3NH2 exhibits a strong SHG response (2.5 × KDP), large optical anisotropy (0.233@546 nm), and blue‐violet and green fluorescence near 360 and 520 nm, respectively. This work expands the methodology for creating new NLO crystals through organic–inorganic hybridization, while also showcasing the potential of C4N3H6SO3NH2 as a multifunctional optical material.

Dumbbell‐shaped systems based on PAHs‐BODIPY‐triarylamine hybrids TM‐(01‐04) are designed as novel and highly efficient hole‐transporting materials for usage in planar inverted perovskite solar cells. BODIPY is employed as a bridge between the PAH units, and the effects of the conjugated π‐system's covalent attachment and size are investigated. Fluorescence quenching, 3D fluorescence heat maps, and theoretical studies support energy transfer within the moieties. The systems are extremely resistant to UVC 254 nm germicidal light sources and present remarkable thermal stability at degradation temperatures exceeding 350 °C. Integrating these systems into perovskite solar cells results in outstanding power conversion efficiency (PCE), with TM‐02‐based devices exhibiting a PCE of 20.26%. The devices base on TM‐01, TM‐03, and TM‐04 achieve PCE values of 16.98%, 17.58%, and 18.80%, respectively. The long‐term stability of these devices is measured for 600 h, with initial efficiency retention between 94% and 86%. The TM‐04‐based device presents noticeable stability of 94%, better than the reference polymer PTAA with 91%. These findings highlight the exciting potential of dumbbell‐shaped systems based on PAHs‐BODIPY‐triarylamine derivatives for next‐generation photovoltaics. [ABSTRACT FROM AUTHOR]

LGa(P2OC)cAAC 2 features a 1,2‐diphospha‐1,3‐butadiene unit with a delocalized π‐type HOMO and a π*‐type LUMO according to DFT calculations. [LGa(P2OC)cAAC][K(DB‐18‐c‐6)] 3[K(DB‐18‐c‐6] containing the 1,2‐diphospha‐1,3‐butadiene radical anion 3⋅− was isolated from the reaction of 2 with KC8 and dibenzo‐18‐crown‐6. 3 reacted with [Fc][B(C6F5)4] (Fc=ferrocenium) to 2 and with TEMPO to [L−HGa(P2OC)cAAC][K(DB‐18‐c‐6)] 4[K(DB‐18‐c‐6] containing the 1,2‐diphospha‐1,3‐butadiene anion 4−. The solid state structures of 2, 3K(DB‐18‐c‐6], and 4[K(DB‐18‐c‐6] were determined by single crystal X‐ray diffraction (sc‐XRD). [ABSTRACT FROM AUTHOR]

Many optoelectronic applications require organic semiconductor (OSC) materials with high electron affinity. In this work, a series of novel acceptor–donor–acceptor (A–D–A) materials with low-lying LUMO energy levels were designed and characterized. In this strategy, two acceptor dyes, bis-isatin and di-2-(2-oxindolin-3-ylidene) malononitrile, were connected by various π–bridges (benzene ring, benzo[c][1,2,5]thiadiazole, monothiophene, trithiophene). We varied the length of the π–conjugation of the central core and the linkage position of the acceptor core (4- vs. 6-position of the phenyl ring) to investigate the effect on the optical and electrochemical properties of the materials. We performed density functional theory (DFT) and time-dependent DFT (TD–DFT) studies to gain insight into the dyes' electronic properties by determining the energy levels. Our findings demonstrate that with increasing acceptor strength and π–conjugation length of the core, the wavelength of the longest absorption maximum as well as their respective extinction coefficients are enhanced, which results in band-gap reduction either by lowering the LUMO and/or raising the HOMO energy level of the molecules. The potential practical utility of these materials as electron-transport materials for perovskite solar cells (PSCs) has been demonstrated. [ABSTRACT FROM AUTHOR]

The physicochemical properties of fullerene‐based materials typically vary depending on the type and mode of addition of functional groups; therefore, developing fullerene derivatives with novel structures is imperative for further progress in materials science. In this study, we develop an efficient one‐step strategy for synthesizing cyclobutene‐annulated fullerene derivatives (cyclobutenofullerenes) and characterize their electronic properties. Despite the steric strain, cyclobutenofullerenes can be easily prepared via a one‐step reaction of C60 with a secondary propargylic phosphate. Structural analysis of the reaction intermediates suggests that the cascade reaction proceeds through a formal [2+2] cycloaddition of C60 with an allene, caused by the 1,3‐migration of the propargylic phosphate, followed by an additional 1,3‐migration and the subsequent 1,2‐elimination of the phosphodiester moiety. [ABSTRACT FROM AUTHOR]

The role of the molecular structure in the formation of the bathochromic shift of the S0 → S1 transition for a family of N-substituted porphine derivatives was studied. Molecular conformations of porphine, four of its N-substituted derivatives, and two model porphines with selected fixed bond angles and lengths in the macrocycles were optimized, the energies of the molecular orbitals were determined, and electronic absorption spectra were calculated using quantum-chemistry methods. It was found that N-substitution led to significant pyramidalization of the nitrogen atom. The degree of hybridization λ2 of the N atom depended on the volume of the N-substituent and reached a value of λ2 = 2.729 in porphyrin H(N–CCl3)P. The degree of hybridization λ2 of the N atom was established as the factor determining the energy of the long-wavelength S0 → S1 transition because the conjugation along the inner Ca–N–Ca fragment of the pyrrole ring decreased upon pyramidalization of the N atom while π-conjugation via the outer Ca–Cb–Cb–Ca fragment, which led to an increase in the size of the conjugated π-system, simultaneously strengthened. The tilt of the N-substituted pyrrole ring relative to the macrocycle mean plane and the electron-donating/electron-withdrawing properties of the N-substituents did not directly affect the bathochromic shift of the S0 → S1 transition. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons consisting of two or three rubicene substructures were designed as π‐conjugated compounds embedding five‐membered rings. The target compounds with t‐butyl groups were synthesized by the Scholl reaction of precursors consisting of 9,10‐diphenylanthracene units, even though a partially precyclized precursor was required for the synthesis of the trimer. These compounds were isolated as stable and dark blue solids. Single‐crystal X‐ray analysis and DFT calculations revealed the planar aromatic framework of these compounds. In the electronic spectra, the absorption and emission bands were considerably red‐shifted compared with those of the reference rubicene compound. In particular, the emission band of the trimer extended to the near‐IR region while retaining the emissive property. The narrowed HOMO‐LUMO gap with the extension of the π‐conjugation was confirmed by cyclic voltammetry and DFT calculations. [ABSTRACT FROM AUTHOR]

Two‐dimensional conjugated covalent organic frameworks (2D c‐COFs) are emerging semiconductor materials for optoelectronic and photothermal applications. In particular, the highly tailorable, semiconducting thiophene‐based 2D c‐COFs have attracted considerable interest due to their nontrivial physicochemical properties such as photo‐activity, broad optical absorption, tunable electronic structures, and so forth. Herein, we demonstrate a novel, crystalline 2D c‐COF based on thienyl‐functionalized benzodithiophene (BDT) and biphenyl (BP) via the Schiff‐base polycondensation reaction. The resultant BDT‐BP‐COF exhibits a broad optical absorption up to ca. 600 nm and decent π‐conjugation along the 2D polymer skeleton, as revealed by the optical absorption and theoretical calculations. The favorable π‐conjugation and the abundant electron‐rich thiophene units confer excellent photo‐activity to BDT‐BP‐COF towards the usage of solar energy. As a proof‐of‐concept application, we explore BDT‐BP‐COF in photothermal conversion, in which it shows a fast surface‐temperature increase upon light irradiation for seconds. [ABSTRACT FROM AUTHOR]

We theoretically investigated the nitrogen substitution effect on the molecular structure and π-electron delocalization in linear nitrogen-substituted polycyclic aromatic hydrocarbons (N-PAHs). Based on the optimized molecular structures and magnetic field-induced parameters of fused bi- and tricyclic linear N-PAHs, we found that the local π-electron delocalization of subcycles (e.g., mono- and bicyclic constituent moieties) in linear N-PAHs is preserved, despite deviation from ideal structures of parent monocycles. The introduction of a fused five-membered ring with a pyrrolic N atom (N-5MR) in linear N-PAHs significantly perturbs the π-electronic condition of the neighboring fused six-membered ring (6MR). Monocyclic pyrrole exhibits substantial bond length alternations, strongly influencing the π-electronic systems of both the fused N-5MR and 6MR in linear N-PAHs, depending on the location of shared covalent bonds. A fused six-membered ring with a graphitic N atom in an indolizine moiety cannot generate monocyclic π-electron delocalization but instead contributes to the formation of polycyclic π-electron delocalization. This is evidenced by bifurcated diatropic ring currents induced by an external magnetic field. In conclusion, the satisfaction of Hückel’s 4n + 2 rule for both mono- and polycycles is crucial for understanding the overall π-electron delocalization. It is crucial to consider the unique characteristics of the three types of substituted N atoms and the spatial arrangement of 5MR and 6MR in N-PAHs.

We report a liquid material based on a pyromellitic diimide (PMDI) framework with branched alkyl chains for the first time. An electron‐accepting PMDI‐based liquid can dissolve electron‐donating solid naphthalene. This liquid demonstrates green photoluminescence (PL) originating from exciplex formation, the properties of which are different from those of the PMDI‐based liquid and naphthalene. The photophysical behavior was investigated by measuring PL spectra and undertaking excited‐state decay measurements. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen (H2) evolution represents a promising and sustainable technology. Covalent organic frameworks (COFs)‐based photocatalysts have received growing attention. A 2D fully conjugated ethylene‐linked COF (BTT‐BPy‐COF) was fabricated with a dedicated designed active site. The introduced bipyridine sites enable a facile post‐protonation strategy to fine‐tune the actives sites, which results in a largely improved charge‐separation efficiency and increased hydrophilicity in the pore channels synergically. After modulating the degree of protonation, the optimal BTT‐BPy‐PCOF exhibits a remarkable H2 evolution rate of 15.8 mmol g−1 h−1 under visible light, which surpasses the biphenyl‐based COF 6 times. By using different types of acids, the post‐protonation is proved to be a potential universal strategy for promoting photocatalytic H2 evolution. This strategy would provide important guidance for the design of highly efficient organic semiconductor photocatalysts. [ABSTRACT FROM AUTHOR]

Carbon‐rich motifs are important building blocks for the fabrication of functional and opto‐electronic materials. Electronic tuning can be achieved by alteration of bonding topologies but also via incorporation of heteroelements, for example phosphorus. Herein we present the palladium/copper mediated formation of branched 1‐phospha‐butadiene derivatives through an unusual alkynylation of a phospha‐enyne fragment. Structural and NMR studies provide mechanistic insights into this alkynylation. Furthermore, we disclose a complex cyclisation of the thus obtained 3‐yne‐1‐phosphabutadiene motifs to give highly substituted phosphole derivatives identified by 2D NMR and SC‐XRD analysis. [ABSTRACT FROM AUTHOR]

Bis-periazulene (cyclohepta[def]fluorene) is one of the seven possible non-alternant isomers of pyrene. Different from the other isomers, bis-periazulene had remained an uncharacterized hydrocarbon until 2022, since it was first reported in 1955. This paper documents our recent achievements in synthesizing and characterizing bis-periazulene derivatives. Its triaryl derivatives 5c‒e exhibited the superimposed electronic structures of peripheral, polarized, and open-shell π-conjugated systems. Furthermore, in contrast to previous theoretical predictions, bis-periazulene derivatives showed the singlet ground state. [ABSTRACT FROM AUTHOR]

On‐surface cyclodehydrogenation recently became an important reaction to planarize π‐conjugated molecules and oligomers. However, the high‐activation barrier to cleave the C−H bond often requires high‐temperature annealing, consequently restricting structures of precursor molecules and/or leading to random fusion at their edges. Here, we present a synthesis of pyrrolopyrrole‐bridged ladder oligomers from 11,11,12,12‐tetrabromo‐1,4,5,8‐tetraaza‐9,10‐anthraquinodimethane molecules on Ag(111) with bond‐resolved scanning tunnelling microscopy. This non‐dehydrogenative cyclization between pyrazine and ethynylene/cumulene groups has a low‐activation barrier for forming intermediary dimeric oligomer containing dipyrazinopyrrolopyrrolopyrazine units, thus giving new insight into the strain‐sensitive in ladder‐oligomer formation. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have received broad interest owing to their permanent porosity, high stability, and tunable functionalities. COFs with long‐range π‐conjugation and photosensitizing building blocks have been explored for sustainable photocatalysis. Herein, we report the first example of COF‐based energy transfer Ni catalysis. A pyrene‐based COF with sp2 carbon‐conjugation was synthesized and used to coordinate NiII centers through bipyridine moieties. Under light irradiation, enhanced energy transfer in the COF facilitated the excitation of Ni centers to catalyze borylation and trifluoromethylation reactions of aryl halides. The COF showed two orders of magnitude higher efficiency in these reactions than its homogeneous control and could be recovered and reused without significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

Recent success in the synthesis of π‐conjugated heavier pnictogen (As, Sb, and Bi) compounds and their transition metal complexes has led to the current surge in interest that led to significant development in the field of photophysical and optoelectronic properties of heavier pnictogens and their transition metal complexes. The presence of heavier pnictogens (As, Sb and Bi) in the molecular skeleton promotes inter‐system crossing (ISC) and reverse inter‐system crossing (RISC), because of the heavy atom effect, via altering the intermolecular interactions and orbital energy levels. As a result, π‐conjugated heavier pnictogen compounds such as arsines, dibenzoarsepins, arsinoquinoline, heterofluorene, benzo[b]heterole (heterole=arsole, bismole, and stibole) show unique optoelectronic properties such as narrow bandgap, low‐energy absorption, and long‐wavelength emission than lighter pnictogen‐based compounds. This review focuses on recent advances in the synthesis and photophysical properties of heavier pnictogen compounds. The synthesis and photophysical properties of heavier pnictogens are discussed and elaborated. [ABSTRACT FROM AUTHOR]

The first examples of a π‐conjugated benzo[b]phosphole P‐oxide in which two phosphole P‐oxide units are connected by a carbon‐carbon double bond are described. The molecules are synthesized as E isomers with respect to the carbon‐carbon double bond and exist as stable cis and trans isomers (chiral and meso one respectively) relatively to the two stereogenic P atoms. The optical and electrochemical properties of both isomers have been investigated by experiment and computations. [ABSTRACT FROM AUTHOR]

Common nonlinear optical (NLO) crystals consist of traditional functional building blocks with inherent optical limitation. Herein, inspired by traditional (B3O6)3− inorganic building block, we theoretically identified a new type of organic functional building blocks and then successfully synthesized the first cyamelurate NLO crystal, Ba(H2C6N7O3)2 ⋅ 8 H2O. To our surprise, the constituent (H2C6N7O3)− building block is not in structurally optimal arrangement, but Ba(H2C6N7O3)2 ⋅ 8 H2O exhibits excellent optical properties including wide band gap of 4.10 eV, very large birefringence of 0.24@550 nm, and exceptionally strong second‐harmonic generation (SHG) response of about 12×KH2PO4. Both the SHG response and birefringence are much larger than those of commercial NLO crystal β‐BaB2O4 with optimally aligned (B3O6)3− building block. Theoretical calculations suggest that the expanded π‐conjugation delocalization within (H2C6N7O3)−vs (B3O6)3− should be responsible to the enhanced performance. This work implies that there is still much room to develop new NLO crystals with excellent functional building blocks that may be longly neglected. [ABSTRACT FROM AUTHOR]

The influence of the degree of π-conjugation in biaroylmethane ligands upon Eu3+ luminescence efficiency in corresponding neutral tris-complexes was investigated in depth. The data obtained by both steady-state and time-resolved luminescence measurements gave an inside into electronic energy transfer mechanisms in the abovementioned complexes. It was shown that extension of the π-system in the naphthalene moiety in comparison to the phenyl one lead to a substantial decrease of both the S1 and T1 energy of the corresponding symmetrical β-diketones, which, in turn, led to a decrease of the total quantum yield of respective Eu3+ complexes. The obtained results are of interest for the rational design of highly luminescent complexes with NIR-emitting lanthanides, as the resonant levels energies are low and can hardly be sensitized by common ligands. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polarizability and Raman intensity of the simplest quinoid hydrocarbon BQM. • SVD analyses for orbital deformations by the electric field and molecular vibrations. • NPOs give an unique orbital representation for electronic deformations in the field. • Large long-axis polarizability and Raman intensity due to HOMO-LUMO promotion. • Mechanism of the weak Raman intensity of the breathing-like CCC stretch mode. The polarizability and Raman intensity of the smallest quinoid hydrocarbon p -benzoquinodimethane were analyzed as electronic deformations in the electric field. The perturbed canonical MOs (CMOs) were transformed to NPOs using the singular value decomposition. The NPOs can represent the intrinsic characters of the electronic deformations that CMOs cannot describe properly. The electronic deformations of HOMO-LUMO type dominate the long-axis polarizability and the strongest Raman intensities. TDDFT calculations demonstrated the relevance of the NPOs to the singly-excited wavefunctions of excited states. The mode-specific predictivity of Raman intensity was discussed based on the polarizability components obtained by B3LYP and CCSD(T) calculations. [ABSTRACT FROM AUTHOR]

Many optoelectronic applications require organic semiconductor (OSC) materials with high electron affinity. In this work, a series of novel acceptor–donor–acceptor (A–D–A) materials with low-lying LUMO energy levels were designed and characterized. In this strategy, two acceptor dyes, bis-isatin and di-2-(2-oxindolin-3-ylidene) malononitrile, were connected by various π–bridges (benzene ring, benzo[c][1,2,5]thiadiazole, monothiophene, trithiophene). We varied the length of the π–conjugation of the central core and the linkage position of the acceptor core (4- vs. 6-position of the phenyl ring) to investigate the effect on the optical and electrochemical properties of the materials. We performed density functional theory (DFT) and time-dependent DFT (TD–DFT) studies to gain insight into the dyes’ electronic properties by determining the energy levels. Our findings demonstrate that with increasing acceptor strength and π–conjugation length of the core, the wavelength of the longest absorption maximum as well as their respective extinction coefficients are enhanced, which results in band-gap reduction either by lowering the LUMO and/or raising the HOMO energy level of the molecules. The potential practical utility of these materials as electron-transport materials for perovskite solar cells (PSCs) has been demonstrated.

The photocatalytic water splitting capability of metal‐free graphitic carbon nitride (g‐C3N4) photocatalyst is determined by its microstructure and photoexcited electrons transfer. Herein, a segmented structure was developed, consisting of alternant g‐C3N4 nanotubes and graphitic carbon rings (denoted as Cr‐CN‐NT). The Cr‐CN‐NT showed ordered structure and ultralong length/diameter ratio of 150 nm in diameter and a few microns in lengths, which promoted electron transport kinetics and elongated photocarrier diffusion length and lifetime. Meanwhile, the local in‐plane π‐conjugation was formed and extended in Cr‐CN‐NT, which could improve charge carrier density and prohibit electron–hole recombination. Accordingly, the average hydrogen evolution rate of Cr‐CN‐NT reached 9245 μmol h−1 g−1, which was 61.6 times that of pristine CN, and the remarkable apparent quantum efficiency (AQE) of Cr‐CN‐NT reached up to 12.86 % at 420 nm. This work may provide a pathway for simultaneous morphology regulation and in‐plane modification of high‐performance photocatalysts. [ABSTRACT FROM AUTHOR]

The synthetic access to macrocyclic molecular topologies with interesting photophysical properties has greatly improved thanks to the successful implementation of organic and inorganic corner units. Based on recent reports, we realized that pseudo‐meta [2.2]paracyclophanes (PCPs) might serve as optimal corner units for constructing 3D functional materials, owing to their efficient electronic communication, angled substituents and planar chirality. Herein, we report the synthesis, characterization and optical properties of four novel all‐carbon enantiopure macrocycles bearing three to six pseudo‐meta PCPs linked by 1,3‐butadiyne units. The macrocycles were obtained by a single step from enantiopure, literature‐known dialkyne pseudo‐meta PCP and were unambiguously identified and characterized by state of the art spectroscopic methods and in part even by x‐ray crystallography. By comparing the optical properties to relevant reference compounds, it is shown that the pseudo‐meta PCP subunit effectively elongates the conjugated system throughout the macrocyclic backbone, such that already the smallest macrocycle consisting of only three subunits reaches a polymer‐like conjugation length. Additionally, it is shown that the chiral pseudo‐meta PCPs induce a remarkable chiroptical response in the respective macrocycles, reaching unprecedented high molar circular dichroism values for all‐carbon macrocycles of up to 1307 L mol−1 cm−1. [ABSTRACT FROM AUTHOR]

Being isoelectronic with alkynes, iminoboranes with a polar B≡N triple bond have been exclusively investigated as a potent 1,2‐dipole in synthetic chemistry. Herein, we disclose the unprecedented reactivity of aryliminoboranes via the BNCC π conjugation, namely hetero‐enyne behavior. This allows for facile dearomative Diels–Alder‐like reactions of aryliminoboranes with aldehydes. This cycloaddition features mild conditions, is catalyst‐free, and has a broad substrate scope and good functional group tolerance. Kinetic and computational studies reveal its second‐order reaction and concerted cyclization mechanism. This report unveils new synthetic application of iminoboranes beyond their classical reaction patterns. [ABSTRACT FROM AUTHOR]

A large optical anisotropy is the most important parameter of birefringent crystals. Integrating π-conjugated groups with large polarizable anisotropy into target compounds is a common strategy for constructing brilliant birefringent crystals. However, the key problem is to enhance the density of the birefringence-active units and further arrange them parallelly. In this study, three novel birefringent crystals, C 9 H 7 NBrX (X = Cl, Br, NO 3 ), are successfully synthesized by introducing a new birefringence-active [C 9 H 7 NBr] + unit. Interestingly, these compounds feature similar layered structures but exhibit different optical anisotropies at 550 nm (0.277 for C 9 H 7 NBrCl, 0.328 for C 9 H 7 NBrBr, and 0.401 for C 9 H 7 NBrNO 3 ) owing to the different anions in them. Particularly, the small trigonal planar NO 3 anions perfectly fill the interstices of the π-conjugated [C 9 H 7 NBr] + groups with large optical anisotropy, with the resulting compound C 9 H 7 NBrNO 3 showing superior optical properties compared to the others. The above findings provide strategies for designing new optical materials with large birefringence by matching birefringence-active groups of different sizes. Additionally, a new theory for predicting and comparing the polarizability anisotropy of compounds is proposed, which would guide in exploring large birefringent crystals., (© 2024 Wiley‐VCH GmbH.)

Panchromatic dyes have been highly useful in the realm of optical devices. Here, we report that panchromatic dyes with heterohelicenes have been successfully synthesized using a donor-acceptor strategy. Our synthesis resulted in the creation of π-extended aza[5]helicene oligomers with butadiyne linkages, which displayed bathochromically shifted absorption and emission spectra. The solvent-dependent optical measurements revealed the intramolecular charge transfer characteristic of these molecules, and theoretical calculations described the biased molecular orbitals on the azahelicene units that generated the charge-transfer characteristic. Encouraged by these results, we also prepared donor-acceptor-donor dyads using azahelicenes and dimide derivatives, resulting in panchromatic absorbing characteristics covering the range from 250 nm to 800 nm. Theoretical calculations showed the presence of mixed charge-transfer transitions and localized transitions on the azahelicene units, which led to a broad light-absorbing property covering the near IR region. Additionally, we conducted measurements of circular dichroism and circularly polarized luminescence for the obtained products. The g-values were reduced by oligomerization, indicating that the lowest energy transitions were allowed in nature., (© 2024 Wiley‐VCH GmbH.)

Mechanochemistry uses mechanical force to break, form, and manipulate chemical bonds to achieve functional transformations and syntheses. Over the last years, many innovative applications of mechanochemistry have been developed. Specifically for the synthesis and activation of carbon‐rich π‐conjugated materials, mechanochemistry offers reaction pathways that either are inaccessible with other stimuli, such as light and heat, or improve reaction yields, energy consumption, and substrate scope. Therefore, this review summarizes the recent advances in this research field combining the viewpoints of polymer and trituration mechanochemistry. The highlighted mechanochemical transformations include π‐conjugated materials as optical force probes, the force‐induced release of small dye molecules, and the mechanochemical synthesis of polyacetylene, carbon allotropes, and other π‐conjugated materials. [ABSTRACT FROM AUTHOR]

Birefringent materials play a significant role in modulating polarized light in optical communication and the laser industry. However, the discovery of deep ultraviolet (DUV, λ<200 nm) birefringent materials still faces a serious challenge. Herein, we propose hydroxylated π‐conjugated [B(OH)3] and [B3O3(OH)3] units for designing DUV birefringent materials. Innovatively, four new hydroxyborates have been synthesized under mild synthesis conditions. They present four novel pseudo layers that benefit from the large degree of freedom assembly modes of [B(OH)3] and [B3O3(OH)3] genes and large birefringence (0.057–0.123@532 nm). Moreover, the Cs3[B(OH)3]2Cl3 crystal features a short DUV cutoff edge (180 nm), which further indicates that the reported compounds are potential DUV birefringent crystals. Free and flexible assembly modes of π‐conjugated [B(OH)3] and [B3O3(OH)3] groups endow them a particular advantage as significant genes for exploring promising DUV birefringent materials. [ABSTRACT FROM AUTHOR]

Additive is a conventional way to enhance halide perovskite active layer performance in multiaspects. Among them, π‐conjugated molecules have significantly special influence on halide perovskite due to the superior electrical conductivity, rigidity property, and good planarity of π‐electrons. In particular, π‐conjugated additives usually have stronger interaction with halide perovskites. Therefore, they help with higher charge mobility and longer device lifetime compared with alkyl‐based molecules. In this review, the detailed effect of conjugated molecules is discussed in the following parts: defect passivation, lattice orientation guidance, crystallization assistance, energy level rearrangement, and stability improvement. Meanwhile, the roles of conjugated ligands played in low‐dimensional perovskite devices are summarized. This review gives an in‐depth discussion about how conjugated molecules interact with halide perovskites, which may help understand the improved performance mechanism of perovskite device with π‐conjugated additives. It is expected that π‐conjugated organic additives for halide perovskites can provide unprecedented opportunities for the future improvement of perovskite devices. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT), time‐dependent DFT, and Marcus theory were used to probe the optoelectronic and charge‐transport properties of compounds obtained by inserting long‐chain aliphatic alkenes or condensed aromatic rings between the planar quinacridone core and the terminal donor diphenylamine moiety of a reference hole‐transporting material (HTM). Compared to the reference HTM, its newly designed derivatives showed lower‐lying highest occupied molecular orbitals that were well matched in energy with the valence band maximum of a representative perovskite absorber. HTMs obtained via the insertion of condensed aromatic rings showed higher hole mobilities than those obtained via the insertion of aliphatic alkenes. Overall, hole mobility was mainly influenced by the charge‐transfer integral, while other factors, such as the hole reorganization energy, hole hopping rate, and centroid distance, had only minor effects. [ABSTRACT FROM AUTHOR]

Abstract Mechanochemistry uses mechanical force to break, form, and manipulate chemical bonds to achieve functional transformations and syntheses. Over the last years, many innovative applications of mechanochemistry have been developed. Specifically for the synthesis and activation of carbon‐rich π‐conjugated materials, mechanochemistry offers reaction pathways that either are inaccessible with other stimuli, such as light and heat, or improve reaction yields, energy consumption, and substrate scope. Therefore, this review summarizes the recent advances in this research field combining the viewpoints of polymer and trituration mechanochemistry. The highlighted mechanochemical transformations include π‐conjugated materials as optical force probes, the force‐induced release of small dye molecules, and the mechanochemical synthesis of polyacetylene, carbon allotropes, and other π‐conjugated materials.

Abstract Additive is a conventional way to enhance halide perovskite active layer performance in multiaspects. Among them, π‐conjugated molecules have significantly special influence on halide perovskite due to the superior electrical conductivity, rigidity property, and good planarity of π‐electrons. In particular, π‐conjugated additives usually have stronger interaction with halide perovskites. Therefore, they help with higher charge mobility and longer device lifetime compared with alkyl‐based molecules. In this review, the detailed effect of conjugated molecules is discussed in the following parts: defect passivation, lattice orientation guidance, crystallization assistance, energy level rearrangement, and stability improvement. Meanwhile, the roles of conjugated ligands played in low‐dimensional perovskite devices are summarized. This review gives an in‐depth discussion about how conjugated molecules interact with halide perovskites, which may help understand the improved performance mechanism of perovskite device with π‐conjugated additives. It is expected that π‐conjugated organic additives for halide perovskites can provide unprecedented opportunities for the future improvement of perovskite devices.

Abstract We synthesized some of the longest unimolecular oligo(p-phenylene ethynylenes) (OPEs), which are fully substituted with electron-withdrawing ester groups. An iterative convergent/divergent (a.k.a. iterative exponential growth – IEG) strategy based on Sonogashira couplings was utilized to access these sequence-defined macromolecules with up to 16 repeating units and 32 ester substituents. The carbonyl groups of the ester substituents interact with the triple bonds of the OPEs, leading to (i) unusual, angled triple bonds with increased rotational barrier, (ii) enhanced conformational disorder, and (iii) associated broadening of the UV/Vis absorption spectrum. Our results demonstrate that fully air-stable, unimolecular OPEs with ester groups can readily be accessed with IEG chemistry, providing new macromolecular backbones with unique geometrical, conformational, and photophysical properties.

Conventional polymerization for the synthesis of carbon nitride usually generates amorphous heptazine‐based melon with an abundance of undesired structural defects, which function as charge carrier recombination centers to decrease the photocatalytic efficiency. Herein, a fully condensed poly (triazine imide) crystal with extended π‐conjugation and deficient structure defects was obtained by conducting the polycondensation in a mild molten salt of LiCl/NaCl. The melting point of the binary LiCl/NaCl system is around 550 °C, which substantially restrain the depolymerization of triazine units and extend the π‐conjugation. The optimized polymeric carbon nitride crystal exhibits a high apparent quantum efficiency of 12 % (λ=365 nm) for hydrogen production by one‐step excitation overall water splitting, owing to the efficient exciton dissociation and the subsequent fast transfer of charge carriers. [ABSTRACT FROM AUTHOR]

The π-conjugation pathways were identified and the degrees of aromaticity for NH-tautomers of corrole free bases were determined by quantum chemistry methods and absorption spectroscopy. The macrocycle skeletal atoms participated differently in the formation of the π-conjugation pathway. It was supposed that conjugation pathways consisting of 18 π-electrons were dominant. At the same time, each of two NH-tautomers possessed its own distinct π-conjugation pathway, which caused their degrees of aromaticity to differ. It was shown that the peripheral substitution architecture of the macrocycle influenced the degree of aromaticity. A method for controlling the equilibrium between the two NH-tautomers that consisted of designing the electron-density distribution in the macrocycle that was characteristic of one of the tautomers was proposed and proved experimentally. [ABSTRACT FROM AUTHOR]

The preparation of large rylenes often needs the use of solubilizing groups along the rylene backbone, and all the substituents of the terrylenes and quaterrylenes were introduced before creating the rylene skeleton. In this work, we successfully synthesized 2,5,10,13-tetrakis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)terrylene (TB4) by using an iridium-catalyzed direct borylation of C–H bonds in terrylene in 56% yield. The product is soluble in common organic solvents and could be purified without column chromatography. Single crystal X-ray diffraction analysis revealed that the terrylene core is not disturbed by the substituents and is perfectly flat. The photophysical properties of TB4 are also unchanged by the substituents because the carbon atoms at 2,5,10,13-positions have less coefficients on its HOMO and LUMO, estimated by theoretical calculations. Finally, the same borylation reaction was applied for quaterrylene, resulting in the formation of soluble tetra-borylated quaterrylene despite a low yield. The post modification of rylenes enables us to prepare their borylated products as versatile units after creating the rylene skeletons.

Abstract Tremendous efforts have been dedicated to develop low-bandgap nonfullerene acceptors (NFAs) for organic solar cells (OSCs). In comparison, the NFAs with a wide bandgap (WBG) have received less attention. Here, three novel acceptor–donor–acceptor type WBG NFAs (TPT-T, TPTT-T, and TPTTT-T) have been designed and synthesized with different fused central cores by varying the π-conjugation length and molecular structures, which all exhibit wide optical bandgaps over 1.8 eV. The successive π-conjugation extension of electron-donating central cores (from TPT-T to TPTT-T and to TPTTT-T) induces red-shifted absorption spectra, lower optical bandgap, and enhanced electron mobility simultaneously. As a result, the optimized OSC devices based on TPTTT-T:PBT1-C achieved a power conversion efficiency of 7.42%, which was higher than those of PBT1-C:TPTT-T (6.93%) and PBT1-C:TPT-T (6.11%) based devices. These results indicate that extending the molecular π-conjugation structure is an effective strategy to design efficient NFAs for OSCs.

The influence of the degree of π-conjugation in biaroylmethane ligands upon Eu3+ luminescence efficiency in corresponding neutral tris-complexes was investigated in depth. The data obtained by both steady-state and time-resolved luminescence measurements gave an inside into electronic energy transfer mechanisms in the abovementioned complexes. It was shown that extension of the π-system in the naphthalene moiety in comparison to the phenyl one lead to a substantial decrease of both the S1 and T1 energy of the corresponding symmetrical β-diketones, which, in turn, led to a decrease of the total quantum yield of respective Eu3+ complexes. The obtained results are of interest for the rational design of highly luminescent complexes with NIR-emitting lanthanides, as the resonant levels energies are low and can hardly be sensitized by common ligands.

[Display omitted] Photopolymerization is an unavoidable polymerization technique used in plethora applications. If benzophenone or thioxanthone have been popular UV photoinitiators, these two structures are unsuitable for performing polymerization experiments in the visible region due to insufficient absorptions. With regards to thioxanthone and in order to redshift its absorption towards the visible range, numerous core-extended thioxanthones have been proposed, enabling to shift their absorptions at longer wavelengths and thus to elaborate visible light photoinitiators. In this field, thioxanthonation of dyes has been extensively studied but the major drawback of this approach was the access to polyaromatic structures exhibiting a low solubility in monomers, adversely affecting the monomer conversion. To address this issue, innovative strategies were envisioned to extend the π-conjugation of thioxanthone while providing an excellent solubility to photoinitiators both in common organic solvents and in monomers. In this review, the different strategies developed to access to these core-extended thioxanthones are detailed and the photopolymerization performance discussed. [ABSTRACT FROM AUTHOR]

In the title compounds, C16H9Cl2N2O2·C4H8O2 and C16H9Cl2N2O2, the bicyclic 4H-chromene cores are nearly planar with maximum deviations of 0.081 (2) and 0.087 (2) Å. In both structures, the chromene derivative molecules are linked into centrosymmetric dimers by pairs of N—H...O hydrogen bonds, forming R22(16) motifs. These dimers are further linked in the 3,4-dichlorophenyl derivative by N—H...N hydrogen bonds into double layers parallel to (100) and in the 2,6-dichlorophenyl derivative by O—H...N hydrogen bonds into ribbons along the [1\overline{1}0] direction. In the 3,4-dichlorophenyl derivative, the 1,4-dioxane solvent molecules are connected to the chromene molecules via O—H...O hydrogen bonds.

For polymer semiconductors, the backbone structure plays an essential role in determining their physicochemical properties and charge transport behaviors. In this work, two donor–acceptor‐type polymers (P‐BDF and P‐NDF) based on benzodifuranone (BDF) and naphthodifunarone (NDF) as electron‐deficient moieties and indaceno‐dithiophene as electron‐rich groups are designed, synthesized and, for the first time, applied in organic field‐effect transistor. P‐BDF and P‐NDF differ from their backbone structures while P‐BDF has a more planar backbone conformation due to its smaller conjugated core size and P‐NDF features a perpendicular‐extended main chain structure. As a result, P‐BDF polymer exhibits bathochromic optical absorption, deeper molecular orbital energy levels, and more importantly, closer π‐stacking and stronger aggregation in the solid state and thus affords a more promising hole mobility of up to 0.85 cm2 V−1 s−1 in OFET devices, while that of the P‐NDF‐based devices is only 0.55 cm2 V−1 s−1. The results suggest the great potential of BDF/NDF‐type chromophores in constructing novel organic semiconductors and also indicate that the main chain coplanarity of polymer semiconductors is more essential than the sole extension of π‐conjugations (especially at the perpendicular direction of polymer main chains) for the design of high‐performance OFET materials. [ABSTRACT FROM AUTHOR]

Metal-organic 1D-coordination polymers, having unique electronic and optical properties, are expected to be a novel advanced functional material capable of fabricating smart plastics, films, and fibers. In this study, we have synthesized a novel metal-organic 1D-coordination polymer composed of a phenylene-bridged bipyrrole bearing N-alkylimino groups (BPI) and palladium(II) ion. The BPI and Pd(II) form square planar bis(bidentate) complex to form a metal coordinated π-conjugation polymer (Poly-BPI/Pd). It is stable in solutions at room temperature, and allowed measurement of its average molecular weight in SEC (Mw = 106,000 and Mn = 18,000, Mw/Mn = 5.88). It also provided a reversible multi redox profile in cyclic voltammetry, most likely originating from strong π-electronic interactions between the BPI components via Pd ion. A variety of substituent groups can be attached to the imino-nitrogens of BPI. A coordination polymer composed of a BPI derivative bearing chiral alkyl chains and Pd(II) showed strong circular dichroism (CD) in the solution due to the unidirectional chiral conformation of the BPI components in the polymer backbone.

Planarity is essential for many organic electronic materials as it maximizes the intramolecular π‐orbital overlap and enables efficient intermolecular interactions through π‐stacking. We propose a statistical way of quantifying the planarity of a wide range of conjugated systems. The quantification takes into account all torsional conformations and their relative contribution to the overall structural disorder, through a planarity index ⟨cos2ϕ⟩. The propensity for planarization and the effect of rotational disorder were examined for a series of commonly used building blocks. The application of the analysis to extended conjugated systems and the correlations between the gas‐phase ⟨cos2ϕ⟩ and crystallographically observed planarity in the solid state were explored. Our calculations also reveal a previously unrecognized effect of increasing band gap upon planarization for conjugated systems coupling strong electron donor and acceptor units. [ABSTRACT FROM AUTHOR]