Ladder-type Structures Research Articles

Nitrogen-Bridged Fused-Ring Nonacyclic and Heptacyclic A-D-A Acceptors for Organic Photovoltaics.

In this work, we designed two nitrogen-bridged fluorene-based heptacyclic FNT and nonacyclic FNTT ladder-type structures, which were constructed by one-pot palladium-catalyzed Buchwald-Hartwig amination. FNT and FNTT were further end-capped by FIC acceptors to form two FNT-FIC and FNTT-FIC non-fullerene acceptors (NFAs), respectively. The two NFAs exhibit more red-shifted absorption and higher crystallinity compared to those of the corresponding carbon-bridged FCT-FIC and FCTT-FIC counterparts. Grazing incidence wide-angle X-ray scattering (GIWAXS) measurements reveal that the 2-butyloctyl groups on the nitrogen in the convex region of FNT-FIC interdigitate with the dioctyl groups on the fluorene in the concave region of another FNT-FIC, resulting in a lamellar packing structure with a d spacing of 13.27 Å. As a consequence, the PM6:FNT-FIC (1:1 wt %) device achieved a power conversion efficiency (PCE) of only 6.60%, primarily due to the highly crystalline nature of FNT-FIC, which induced significant phase separation between PM6 and FNT-FIC in the blended film. However, FNTT-FIC, featuring 2-butyloctyl groups positioned on the nitrogen within the concave region of its curved skeleton, exhibits improved donor-acceptor miscibility, thereby promoting a more favorable morphology. As a result, the PM6:FNTT-FIC (1:1.2 wt %) device exhibited a higher PCE of 12.15% with an exceptional Voc of 0.96 V. This research demonstrates that placing alkylamino moieties within the concave region of curved A-D-A NFAs leads to a better molecular design.

Ladder-type conjugated molecules as robust multi-state single-molecule switches

•Synthesis of a methylthio-functionalized, ladder-type oligoaniline derivative •Excellent stability and high molecular conductance in oxidized and protonated states •Robust switching of single-molecule conductance among three different states Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches. Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches.

Synthesis and exceptional operational durability of polyaniline-inspired conductive ladder polymers.

Ladder-type structures can impart exceptional stability to polymeric electronic materials. This article introduces a new class of conductive polymers featuring a fully ladder-type backbone. A judicious molecular design strategy enables the synthesis of a low-defect ladder polymer, which can be efficiently oxidized and acid-doped to achieve its conductive state. The structural elucidation of this polymer and the characterization of its open-shell nature are facilitated with the assistance of studies on small molecular models. An autonomous robotic system is used to optimize the conductivity of the polymer thin film, achieving over 7 mS cm-1. Impressively, this polymer demonstrates unparalleled stability in strong acid and under harsh UV-irradiation, significantly surpassing commercial benchmarks like PEDOT:PSS and polyaniline. Moreover, it displays superior durability across numerous redox cycles as the active material in an electrochromic device and as the pseudocapacitive material in a supercapacitor device. This work provides structural design guidance for durable conductive polymers for long-term device operation.

A-D-A-type electron acceptors based on pyrrole-containing ladder-type heteroarenes for organic solar cells

<p>Organic solar cells (OSCs) have undergone rapid development and achieved significant breakthroughs in power conversion efficiencies, largely due to the emergence of nonfullerene acceptors (NFAs) with ladder-type multifused-ring structures. Over the past few years, huge efforts have been devoted to synthesizing new ladder-type donor cores via rational molecular design, as it can directly dictate most of the OSC-related physicochemical and optoelectronic properties of NFAs. Among the numerous reported ladder-type donor cores with diverse chemical structures, those containing pyrrole rings are becoming the preferred building blocks for the development of high-performance NFAs due to their intriguing physicochemical properties and unique molecular stacking. To date, most of the state-of-the-art NFAs (e.g., Y-series and M-series acceptors) use pyrrole-containing ladder-type heteroarenes as the donor cores. In this review, we summarize acceptor-donor-acceptor (A-D-A)-type NFAs based on pyrrole-containing ladder-type heteroarenes with detailed discussion of the relationships between molecular structures and device performance. We also provide a brief summary of common synthetic strategies for pyrrole-containing ladder-type heteroarenes. Finally, the remaining challenges and the key research directions in the near future are proposed in the hope of providing some useful insights for the further rational design of novel pyrrole-containing ladder-type building blocks and corresponding high-performance NFA materials.</p>

Theoretical study of the structure-activity relationship of the S-shaped acceptor molecules for organic solar cell applications

The introduction of a bridge element to covalently ring-lock the neighboring aryl or heteroaryl groups connected by a single bond has led to a variety of fascinating multifused ladder-type structures. Here, we have designed a new series of 2H-pyran containing tetracyclic dithienocyclopentapyran compounds (MMA1 to MMA3). Long conjugation at end-capped of designed systems enhances the power conversion efficiencies of non-fullerene-containing organic solar cells. Different geometric parameters of designed systems have been examined through density functional theory and time-dependent density functional theory. Designed molecules expressed high absorption maxima values with a reduced energy bandgap. Open circuit voltage along with transition density matrix analysis recommended that charge transfer occurs from lower energy orbitals to higher energy orbitals. Reorganization energy analysis also suggested high charge mobility occurs from donor polymer to acceptor molecules. Results of all parameters advocated that designed molecules are potential candidates for high-performance organic solar cells.

Probing the Stability of Ladder-Type Coilable Space Structures

This paper analyzes the buckling and postbuckling behavior of ultralight ladder-type coilable structures, called strips, composed of thin-shell longerons connected by thin rods. Based on recent research on the stability of cylindrical and spherical shells, the stability of strip structures loaded by normal pressure is studied by applying controlled perturbations through localized probing. A plot of these disturbances for increasing pressure is the stability landscape for the structure, which gives insight into the structure’s buckling, postbuckling, and sensitivity to disturbances. The probing technique is generalized to higher-order bifurcations along the postbuckling path, and low-energy escape paths into buckling that cannot be predicted by a classical eigenvalue formulation are identified. It is shown that the stability landscape for a pressure-loaded strip is similar to the landscape for classical shells, such as the axially loaded cylinder and the pressure-loaded sphere. Similarly to classical shells, the stability landscape for the strip shows that an early transition into buckling can be triggered by small disturbances; however, while classical shell structures buckle catastrophically, strip structures feature a large stable postbuckling range.

Fulvalene-Based Polycyclic Aromatic Hydrocarbon Ladder-Type Structures: Synthesis and Properties.

Polycyclic aromatic hydrocarbons (PAHs) have found strong interest for their electronic properties and as model systems for graphene. While PAHs have been studied intensively as single units, here PAHs were constructed in ladder-type arrangements using cross-conjugated fulvalene and dithiafulvalene motifs as connecting units and moving forward a convenient synthetic approach for dimerizing (thio)ketones into olefins by the action of Lawesson's reagent. Some of the PAHs can also be regarded as "super-extended" tetrathiafulvalenes (TTFs) with some of the largest cores ever explored, being multi-redox systems that exhibit both reversible oxidations and reductions. Concomitant absorption redshifts were observed when expanding the ladder-type structures from one to two to three indenofluorene units, and optical and electrochemical HOMO-LUMO gaps were found to correlate linearly. Various conformations (and solid-state packing arrangements) were studied by X-ray crystallography and computations.

Investigating the backbone conformation and configuration effects for donor–acceptor conjugated polymers with ladder-type structures synthesized through Aldol polycondensation

Aldol reaction is a green approach that is exclusively suitable for developing conjugated polymers (CPs) with ladder-type structures.

Synthesis and Characterization of Functionalizable Silsesquioxanes with Ladder-type Structures

Novel tetravinyl- and tetraallyl-substituted laddersiloxanes were synthesized and characterized. It was shown that peripheral olefins could successfully undergo hydrosilylation quantitatively, poss...

Synthesis and Structure of New Trimethylplatinum(IV) Iodide Complexes of 2,2′‐Bipyridine Ligands

The synthesis and structural characterization of four new trimethylplatinum(IV) iodide complexes of 2,2′‐bipyridine ligands {[PtMe3(4,4′‐Clbipy)I] (1), [PtMe3(4,4′‐Brbipy)I] (2), [PtMe3(4,4′‐CNbipy)I] (3) and [PtMe3(4,4′‐NO2bipy)I] (4)} are reported. The 1H NMR spectra of the complexes reveal the presence of two chemically distinct methyl groups in the complexes. X‐ray crystal structures of complexes 1–4 show that the platinum metal center in each of the complexes form distorted octahedral structure being surrounded by methyl groups, bipyridine ligand, and iodine atom. Furthermore, the crystal packing study shows that self‐assembly of the complexes are governed by weak hydrogen bonding and other non‐covalent interactions such as π···π, halogen···π and C–H···π interactions. Complex 1 exhibits infinite one‐dimensional zigzag chain structure and other three complexes form infinite ladder type structures.

Enhancement in Open-Circuit Voltage in Organic Solar Cells by Using Ladder-Type Nonfullerene Acceptors.

The open-circuit voltage ( Voc) loss has always been a major factor in lowering power conversion efficiencies (PCEs) in bulk heterojunction organic photovoltaic cells (OPVs). A method to improve the Voc is indispensable to achieve high PCEs. In this paper, we investigated a series of perylene diimide-based ladder-type molecules as electron acceptors in nonfullerene OPVs. The D-A ladder-type structures described here lock our π-systems into a planar structure and eliminate bond twisting associated with linear conjugated systems. This enlarges the interface energy gap (Δ EDA), extends electronic delocalization, and hence improves the Voc. More importantly, these devices showed an increase in Voc without compromising either the Jsc or the FF. C5r exhibited a strong intermolecular interaction and a PCE value of 6.1%. Moreover, grazing-incident wide-angle X-ray scattering analysis and atomic force microscopy images suggested that our fused-ring acceptors showed a suitable domain size and uniform blend films, which were not affected by their rigid molecular structures.

Palladium catalyst imbedded in polymers of intrinsic microporosity for the Suzuki-Miyaura coupling reaction.

Polymers of intrinsic microporosity (PIMs) are porous polymers with rigid ladder-type chain structures. Synthesizing these polymers usually involves the step polymerization of two types of monomer, namely, active fluorine-substituted aromatic ring monomers and phenolic monomers. Herein, we report a new PIMs preparation method using self-synthesized fluorinated monomers and common monomer 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl spirobisindane. The fluorinated monomers were synthesized through the imidization of tetrafluorophthalic anhydride and aromatic diamines. The resulting PIMs served as a support for palladium, with the formed catalyst showing potential for application in the Suzuki–Miyaura coupling reaction.

Generation of an N→B Ladder-type Structure by Regioselective Hydroboration of an Alkenyl-Functionalized Quaterpyridine.

An unusual reactivity of 2-(1-alkenyl)-pyridines towards hydroboration with 9H-borabicyclo[3.3.1]nonane (9H-BBN) has been employed to selectively introduce two borane groups into a conjugated quaterpyridine. Quantitative conversion of the substrate was observed with exclusive regioselectivity. A molecular structure that allows intramolecular N→B coordination was generated. The effect of the ladder formation on the molecular structure and the electronic properties of the conjugated system have been investigated. The synthetic strategy demonstrated herein offers a facile access to N→B ladder-type structures from readily available substrates, and allows to simultaneously introduce several boron centers under mild conditions.

New Lanthanide Alkynylamidinates and Diiminophosphinates

This contribution reports the synthesis and structural characterization of several new lithium and lanthanide alkynylamidinate complexes. Treatment of PhC≡CLi with N,N′-diorganocarbodiimides, R–N=C=N–R (R = iPr, Cy (cyclohexyl)), in THF or diethyl ether solution afforded the lithium-propiolamidinates Li[Ph–C≡C–C(NCy)2] S (1: R = iPr, S = THF; 2: R = Cy, S = THF; 3: R = Cy, S = Et2O). Single-crystal X-ray diffraction studies of 1 and 2 showed the presence of typical ladder-type dimeric structures in the solid state. Reactions of anhydrous LnCl3 (Ln = Ce, Nd, Sm or Ho) with 2 in a 1:3 molar ratio in THF afforded a series of new homoleptic lanthanide tris(propiolamidinate) complexes, [Ph–C≡C–C(NCy)2]3Ln (4: Ln = Ce; 5: Ln = Nd; 6: Ln = Sm; 7: Ln = Ho). The products were isolated in moderate to high yields (61%–89%) as brightly colored, crystalline solids. The chloro-functional neodymium(III) bis(cyclopropylethynylamidinate) complex [{c-C3H5–C≡C–C(NiPr)2}2Ln(µ-Cl)(THF)]2 (8) was prepared from NdCl3 and two equiv. of Li[c-C3H5–C≡C–C(NiPr)2] in THF and structurally characterized. A new monomeric Ce(III)-diiminophosphinate complex, [Ph2P(NSiMe3)2]2Ce(µ-Cl)2Li(THF)2 (9), has also been synthesized in a similar manner from CeCl3 and two equiv. of Li[Ph2P(NSiMe3)2]. Structurally, this complex resembles the well-known “ate” complexes (C5Me5)2Ln(µ-Cl)2Li(THF)2. Attempts to oxidize compound 9 using trityl chloride or phenyliodine(III) dichloride did not lead to an isolable cerium(IV) species.

Mononuclear and coordination polymer of silver(I) complexes: design, synthesis, and crystal structure analysis

A series of mononuclear structures and coordination polymers of silver(I) has been synthesized and characterized by IR spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction. Reaction of the silver(I) precursor [Ag(PPh3)2(OAc)] with 2,3-pyridinedicarboxylic acid (2,3-pyCOOH), 2,6-pyridinedicarboxylic acid (2,6-pyCOOH), 3-pyridinecarboxylic acid (3-pyCOOH), and 4-pyridinecarboxylic acid (4-pyCOOH) afforded mononuclear complexes [Ag(PPh3)2(2,3-COO)] (1), [Ag(PPh3)2(2,6-COO)]·EtOH·MeCN (2), [Ag(PPh3)2(3-COO)]·H2O (3), and [Ag(PPh3)2(4-COO)] (4), respectively. Coordination polymers [Ag(PPh3)(2,3-COO)]n (5), [Ag2(PPh3)2(3-pyCOO)2]n (6), and [Ag(PPh3)2(4-COO)]n·EtOH (7) were obtained from reaction of Ag(OAc), PPh3, and pyridinedicarboxylic acid or pyridinecarboxylic acid. Even though the formation of 5 can be achieved by hydrothermal reaction using similar reactants to those in formation of 1, the percentage yield and by-products of the final product prohibit further analysis of the compound. Complexes 5 and 6 are 1-D zigzag and ladder type structures, respectively, with argentophilic interactions, Ag⋯Ag, dominating the stability of 6. Complex 7 shows a 2-D layer structure with three-connected 4.82-fes topology.

Donor-acceptor conjugated polymers based on multifused ladder-type arenes for organic solar cells.

Harvesting solar energy from sunlight to generate electricity is considered as one of the most important technologies to address the future sustainability of humans. Polymer solar cells (PSCs) have attracted tremendous interest and attention over the past two decades due to their potential advantage to be fabricated onto large area and light-weight flexible substrates by solution processing at a lower cost. PSCs based on the concept of bulk heterojunction (BHJ) configuration where an active layer comprises a composite of a p-type (donor) and an n-type (acceptor) material represents the most useful strategy to maximize the internal donor-acceptor interfacial area allowing for efficient charge separation. Fullerene derivatives such as [6,6]-phenyl-C61 or 71-butyric acid methyl ester (PCBM) are the ideal n-type materials ubiquitously used for BHJ solar cells. The major effort to develop photoactive materials is numerously focused on the p-type conjugated polymers which are generally synthesized by polymerization of electron-rich donor and electron-deficient acceptor monomers. Compared to the development of electron-deficient comonomers (acceptor segments), the development of electron-rich donor materials is considerably flourishing. Forced planarization by covalently fastening adjacent aromatic and heteroaromatic subunits leads to the formation of ladder-type conjugated structures which are capable of elongating effective conjugation, reducing the optical bandgap, promoting intermolecular π-π interactions and enhancing intrinsic charge mobility. In this review, we will summarize the recent progress on the development of various well-defined new ladder-type conjugated materials. These materials serve as the superb donor monomers to prepare a range of donor-acceptor semi-ladder copolymers with sufficient solution-processability for solar cell applications.

Types, characteristics and metallogenesis of gold deposits in the Jiaodong Peninsula, Eastern North China Craton

The Jiaojia type gold deposits in the Jiaodong Peninsula of the North China Craton represent an emerging major gold reserve, and constitute one of the two important types of gold deposits in China, the other being the Linglong type. The gold mineralization in these deposits can be subdivided into seven categories namely, altered-rock type in the fracture zone, gold-bearing quartz vein type, braided quartz vein type along fracture zones, quartz-sulfide vein type, interlayer type along the detachment belt, altered-conglomerate type and breccia type along the basin margin faults. The peak gold mineralization occurred during Early Cretaceous with the metallogeny controlled by extensive crust–mantle interaction. The deposits are hosted in the Early Precambrian basement and Mesozoic intrusions which experienced phyllic, sulfidic, silicic, and potassic alterations. The structures of the ore bodies include pinchout, repetition splay branches, composite, lateral tilting, echelon and imbrications. The upwelling of hot magma, fluid activity and extensional detachment resulted in the formation of extensive gold deposits in the Jiaodong Peninsula. The extensional detachment derived from magma upwelling provided favorable ore-hosting structure for the gold deposition. The ladder-type ore-hosting structures show variation from sharp to gentle dips with marked enrichment of the gold ores at the gentle angle of the fault segments and at the transition from steep to gentle dip angles, displaying a step-fault-controlled ore deposition. The formation of the gold deposits in the Jiaodong Peninsula coincided with the large-scale Early Cretaceous thinning of the lithosphere in the North China Craton, mainly controlled by extensional tectonics.

On Flow-Acoustic Resonant Interactions in Transitional Airfoils

We discuss our recent experimental and preliminary numerical efforts examining resonant feedback mechanism of flow-acoustic interactions in airfoil transitional boundary layers. Experimentally recorded unsteady responses of loaded, transitional NACA0012 airfoil with tripped suction or pressure sides confirm the presence of shifted ladder-type tonal structures with dual velocity dependence in the acoustic signal previously reported in the literature. The installation of upstream grid generating low-intensity turbulence appears to eliminate the feedback mechanism leaving just a single velocity dependence for the dominant spectral components. Complementary numerical efforts employ a high-order Navier-Stokes solver implementing low-pass filtering of poorly resolved high-frequency solution content to retain numerical accuracy and stability over the range of transitional flow regimes. Within the scope of 2D analysis, the conducted numerical experiments particularly investigate the behavior of the boundary-layer statistical moments during the transitional flow regimes characterized by the presence of the acoustic feedback, and address sensitivity of the latter to the flow Reynolds number.

The First Aziridinylguanidinates: New Precursors for Potentially Volatile Metal Guanidinates

The first lithium-aziridinylamidinates, Li[(C2H4N)C(NR)2]·THF (R = iPr (3), Cy (4); iPr = isopropyl, Cy = cyclohexyl), have been prepared by addition of N-aziridinyllithium, C2H4NLi (2), to either N,N′-diisopropylcarbodiimide or N,N′-dicyclohexylcarbodiimide. The cyclohexyl derivative 4 was crystallised from both diethyl ether (Et2O) and THF to afford the crystalline solvent adducts {Li[(C2H4N)C(NR)2]·S}2 (4: S = THF; 4a: S = Et2O) which were structurally characterised by X-ray diffraction. In the solid state, these lithium-aziridinylamidinates comprise ladder-type dimeric molecular structures.

Synthesis and structural characterization of organotin(IV) carboxylates based on different heterocyclic substituents

Six novel organotin(IV) carboxylates have been successfully synthesized, namely, the polymer (C 6H 5) 3Sn(L1) ∞ ( 1) [HL1 = 4-imidazolyl benzoic acid], the mononuclear (C 6H 5) 3Sn(L2) ( 2) [HL2 = 4-pyrazolylbenzoic acid], (C 6H 5) 3Sn(L3)·CH 3OH ( 3) [HL3 = 4-triazolylbenzoic acid] and (C 6H 5) 3Sn(L4) ( 4) [HL4 = 4-tetrazolyl benzoic acid] and the tetranuclear [( n-Bu 2Sn) 4(L2) 2O 2(OCH 3) 2] ( 5) and [( n-Bu 2Sn) 4(L3) 2O 2(OCH 3) 2] ( 6). X-ray diffraction analyses show 1D infinite chain of polymer 1, single molecular structures of isomorphous complexes 2 and 4, single molecule structures of complex 3 containing solvent CH 3OH molecule and similar ladder-type structures of complexes 5 and 6. The photoluminescence of ligands and 1–6 were also measured in the solid state at room temperature.