Axial Chirality Research Articles

Conjugation-Induced Spin Delocalization in Helical Chiral Carbon Radicals via Through-Bond and Through-Space Effects.

A class of highly stable hydrocarbon radicals with helical chirality are synthesized, which can be isolated and purified by routine column chromatography on silica gel. These carbon-centered radicals are stabilized by through-bond delocalization and intramolecular through-space conjugation, which is evidenced by Density Functional Theory (DFT) calculation. The high stability enables to directly modify the carbon radical via palladium-catalyzed cross-coupling with the radical being untapped. The structures and optoelectronic properties are investigated with a variety of experimental methods, including Electron Paramagnetic Resonance (EPR), Ultraviolet Visisble Near Infrared (UV-vis-NIR) measurements, Cyclic Voltammetry (CV), Thermogravimetry Analysis (TGA), Circular Dichroism (CD) spectra, High-Performance Liquid Chromatography (HPLC), and X-ray crystallographic analysis. DFT calculations indicated that the 9-anthryl helical radical is more stable than its tail-to-tail σ-dimer over 13.2kJmol-1 , which is consistent with experimental observations.

Synthesis of Indole‐Fused 1,4‐Diazepinones via Photoredox‐Catalyzed Cascade Cyclization Reaction

AbstractA photoredox‐promoted approach for the synthesis of [1,4]diazepino[1,7‐a]indol‐6(7H)‐ones starting from N‐indolyl phenylacrylamides and aroyl chlorides as radical source is reported. This method, that involves a cascade radical addition on C−C double bond followed by intramolecular cyclization at indole C2‐position, affords two diastereomeric indole‐fused 1,4‐diazepinones characterized by a N−C(aryl) axial chirality in yields ranging from 51 to 99%.

Helix-Induced Asymmetric Self-Assembly of π-Conjugated Block Copolymers: From Controlled Syntheses to Distinct Properties.

Conspectusπ-Conjugated polymers have gained significant interest because of their potential applications in optoelectronics, bioelectronics, and other domains. The controlled synthesis of π-conjugated block polymers optimizes their performance and enables novel properties and functions. However, precise control of the self-assembled architectures of π-conjugated polymers remains a formidable challenge. Inspired by the precise helical architectures of biomacromolecules, the helical polymers and the supramolecular helical assemblies have gained significant attention. Helical polymers with an excess of one-handed helicity can be optically active with a strong tendency toward self-assembly. Incorporating a helical polymer into a π-conjugated polymer can induce asymmetric helical assemblies, leading to novel chiral materials with unique functionalities.To control the self-assembly of architectures, π-conjugated polymers are usually synthesized into block copolymers by incorporating a polymer with self-assembling characteristics. Although various π-conjugated block copolymers have been produced, precise and asymmetric self-assembly is still challenging and has rarely been addressed. Incorporating helical polymers into the π-conjugated polymers can induce a precise and asymmetric self-assembly, which transfers the chirality of the helical polymer block to the π-conjugated polymer, resulting in chiral supramolecular architectures with unique chiroptical properties and functionalities. However, synthesizing hybrid block copolymers containing two distinct polymer blocks is complicated. Some general strategies such as connecting the chain ends of two preformed homopolymers and extending the chain of a prefabricated π-conjugated polymer with a second monomer are time-consuming and require complex synthetic protocols. Therefore, developing novel strategies for the facile synthesis of π-conjugated block copolymers with a predictable molar mass, low dispersity, and tunable composition is of practical importance.Recently, we investigated a controlled synthesis of helical polyisocyanides, helical polyallenes, and helical polycarbenes by developing advanced Pd(II) and Ni(II) catalysts. These helical polymers were successfully incorporated into π-conjugated polymers, including polythiophene, polyfluorene, and poly(phenyleneethynylene), via a one-pot sequential living block polymerization of the two distinct monomers using Pd(II)- or Ni(II)-complexes as catalysts. As a result, a variety of well-defined π-conjugated block copolymers containing helical polymeric blocks were readily synthesized. Although the copolymerized monomers possess different structures and polymerization mechanisms, the one-pot block copolymerization followed a living polymerization mechanism and provided the desired π-conjugated block copolymers in high yields with controlled molar mass, narrow size distribution, and tunable composition.Remarkably, the helical polymeric block induces the π-conjugated block copolymer asymmetric self-assembly into a supramolecular, one-handed helical architecture resulting in distinct optical properties. More interestingly, by utilizing the crystallization of conjugated blocks and one-handed helical blocks, the crystallization-driven and helix-induced precise asymmetric living self-assembly yielded a family of uniform and single-handed helical architectures with controlled dimensions, narrow distribution, and well-defined helicity. The transfer of helical chirality to the supramolecular architectures rendered the achiral π-conjugated blocks with unique chiroptical properties such as the emission of white light over a broad optical spectrum and the circularly polarized luminescence.

Enantio- and regioselective [2 + 2 + 2] cycloaddition of BN-diynes for construction of C-B axial chirality

Enantio- and regioselective [2 + 2 + 2] cycloaddition of BN-diynes for construction of C-B axial chirality

Progress on the Enantioselective Synthesis of Axially Chiral Cycloalkylidenes

AbstractThe discovery of new asymmetric synthetic methodologies and the asymmetric synthesis of new chiral compounds have been a major focus of synthetic organic chemists for decades. Axially chiral compounds have gained considerable attention in recent years because of their widespread utility in asymmetric catalysis and synthesis. Methods for the asymmetric synthesis of axially chiral cycloalkylidenes, a subset of axially chiral molecules, are far fewer compared to those developed for the preparation of chiral allenes and chiral biaryl compounds. In this review, different approaches for the synthesis of axially chiral cycloalkylidenes are summarized.1 Introduction2 Methods for the Enantioselective Synthesis of Axially Chiral Cycloalkylidenes2.1 Asymmetric Synthesis of Axially Chiral Cycloalkylidenes2.1.1 Asymmetric Horner–Wadsworth–Emmons (HWE) Reactions2.1.2 Asymmetric Wittig Reactions2.1.3 Asymmetric Dehydrohalogenation Reactions2.1.4 Asymmetric Elimination Reactions of Chiral Sulfoxides/Selenoxides2.1.5 Kinetic Resolution of Prochiral Compounds2.1.6 Other Miscellaneous Methods2.2 Catalytic Asymmetric Synthesis of Axially Chiral Cycloalkylidenes3 Conclusion

Stereogenic π-Conjugated Macrocycles: Synthesis, Structure, and Chiroptical Properties Including Circularly Polarized Luminescence

AbstractHighly symmetrical and aesthetically pleasing molecules have attracted the attention of organic chemists. We synthesized new highly symmetric stereogenic π-conjugated macrocycles with planar or axial chirality. Macrocyclic oligomers synthesized by Yamamoto coupling or Suzuki–Miyaura cross-coupling from the π-unit containing chirality. These cyclization reactions gave multiple oligomers in relatively high yields. We then elucidated their structures and investigated their chiroptical properties, including circular dichroism (CD) and circularly polarized luminescence (CPL). Because of the selection rule for rigid and symmetric structures, these macrocycles exhibit a high dissymmetry factor (g abs or g lum) for circularly polarized light in CD or CPL. Several rigid cyclic compounds retain a highly symmetric structure in the excited state and exhibit higher g lum values than common chiral organic compounds. This Account provides a brief background regarding chiroptical properties, followed by a summary of the various macrocycles synthesized in this study. We are glad if this Account will be a source of ideas not only for chemists working with π-conjugated compounds, but also for synthetic chemists working with chiral compounds, especially those engaged in asymmetric synthesis.1 Introduction2 Brief Description of Chiroptical Properties3 Stereogenic Macrocycle Based on [2.2]Paracyclophane3.1 Stereogenic Double-decker Oligothiophene3.2 Stereogenic Biselenophene Macrocycle3.3 Helical Oligophenylene Linked with [2.2]Paracyclophane4 Stereogenic Macrocycle Based on Binaphthyl4.1 Cyclic Oligomer of Chiral Binaphthyl4.2 Doubly Twisted Binaphthyl Dimer4.3 Cyclic Oligomer of Binaphthyl Extended with Paraphenylene4.4 Curved Helical Paraphenylene Anchoring Chiral Binaphthyl4.5 Binaphthyl-Hinged [5]-Helicene5 Summary

Stereocontrol of C-N Axial and Spiro-Central Chirality via Rh(II)-Catalyzed Enantioselective N-H Bond Insertion of Indolinone-Spiroacetal.

A rhodium-catalyzed carbene N-H insertion protocol for simultaneously controlling the C-N axial and spiro-central chiralities is disclosed, resulting in the rapid assembly of enantiopure N-arylindolinone-spiroacetal derivatives in high yields with excellent enantioselectivities. This promising strategy features the chiral C-N axis, spiro-central chirality, functional group tolerance, and late-stage diversification. DFT calculations indicate that the N-H insertion is the axial-chirality-determining step and that the 1,5-H shift step is regiospecifically caused by the spirocycle.

A free carboxyl-decorated metal-organic framework with 3D helical chirality for highly enantioselective recognition

With the judicious selection of a designed polycarboxylate derived from L-phenylalanine, (S)-5-(((1-carboxy-2-phenylethyl)amino)methyl)isophthalic acid (H3L), a novel homochiral metal-organic framework decorated with a free carboxyl, {[Cu2(HL)2(bipy)]∙2H2O}n (Cu-MOF), has been designed and synthesized in a solvothermal process. The result of single crystal X-ray diffraction analysis showed that Cu-MOF had the character of a three-dimensional structure with helical chirality. As we expected, in Cu-MOF, one accessible free carboxylic acid group on H3L pointed toward the spiral channels, and the other two –COOH groups were utilized in bonding. The enantioseparation performance of Cu-MOF was thoroughly investigated and the results showed that Cu-MOF can specifically recognize S-1-(1-naphthyl) ethanol (S-NE) with enantiomeric excess (ee) value of 99.35 %, which was much higher than the other three racemates. The appropriate size together with suitable interaction sites played an important role in enantioseparations. Inspired by the excellent chiral recognition effects towards S-NE, the chiral recognition mechanism was experimentally clarified. A fully agreement observed in 13C CP MAS NMR analysis as well as the X-ray photoelectron spectroscopy (XPS) determination revealed that a strong hydrogen bonding interaction forces existed between the hydroxyl of the optical S-NE and the decorated –COOH in the chiral framework. The control experiment further identified the decisive role of the uncoordinated carboxyl group in Cu-MOF. In addition, the strong intermolecular off-set π-π interactions between the phenyl ring involved with the coordinated COO− groups in Cu-MOF and the naphthyl ring of S-NE, was the another important factor for the specifical enantioseparation of S-enantiomer. On the basis of strong intermolecular hydrogen bonding, NE racemates were enantioselective discriminated and enantiomeric purity can be determined by means of Raman scattering spectroscopy.

Photoisomerization of "Partially Embedded Dihydropyridazine" with a Helical Structure.

Herein, we report the synthesis of two "partiallyembedded fused-dihydropyridazine N-aryl aza[5]helicene derivatives" (PDH) and the demonstration of their intrinsic photo-triggered multi-functional properties based on a Kekulé biradical structure. Introducing bulky electron-withdrawing trifluoromethyl or pentafluoroethyl groups into the aza[5]helicene framework (PDH-CF3 and -C2F5) gives PDH axial chirality based on the helicity of the P and M forms, even at room temperature. Upon photo-irradiation of PDH-CF3 in a frozen solution, an ESR signal from the triplet biradical with zero-field splitting values, generated by N-N bond dissociation, was observed. However, when the irradiation was turned off, the ESR signal became silent, indicating the existence of two equilibriums, between the biradical and quinoidal forms based on the Kekulé structure, and between N-N bond cleavage and recombination. The observed photo- and thermally induced behaviors indicate that T-type photochromic molecules are involved in the photoisomerization mechanism involving the two equilibriums. Inspired by the photoisomerization, chirality control of PDH by photoracemization was achieved. Multiple functionalities, such as T-type photochromism, photo-excitation-mediated triplet biradical formation, and photoracemization, which are attributed to the "partiallyembedded dihydropyridazine" structure, are demonstrated.

Spin Polarization in Transport Studies of Chirality-Induced Spin Selectivity.

Chirality-induced spin selectivity (CISS) is a recently discovered effect in which structural chirality can result in different conductivities for electrons with opposite spins. In the CISS community, the degree of spin polarization is commonly used to describe the efficiency of the spin filtering/polarizing process, as it represents the fraction of spins aligned along the chiral axis of chiral materials originating from non-spin-polarized currents. However, the methods of defining, calculating, and analyzing spin polarization have been inconsistent across various studies, hindering advances in this field. In this Perspective, we connect the relevant background and the definition of spin polarization, discuss its calculation in different contexts in the CISS, and propose a practical and meaningful figure of merit by quantitative analysis of magnetoresistance in CISS transport studies.

Chirality Transfer Intramolecular Pauson-Khand Reaction with N-C Axially Chiral Sulfonamides Bearing an Ene-Yne Structure.

An intramolecular Pauson-Khand reaction with enantioenriched N-C axially chiral N-allyl-N-(2-alkynylphenyl)sulfonamide derivatives proceeded with complete chirality transfer from axial chirality (P configuration) to central chirality (R configuration), affording chiral nitrogen-containing tricyclic compounds (tetrahydrocyclopentaquinolin-2-one derivatives).

Copper-Catalyzed, Regioselective, Unsymmetrical Homocoupling of Quinoxalin-2(1H)-ones to Form C-N Homodimers.

An environmentally benign and efficient method for the synthesis of unsymmetrical diquinoxalin-2(1H)-ones with potential axial chirality via inexpensive copper-catalyzed, low-toxicity, and stable PIFA oxidation, rarely assisted by PhSeSePh, regioselective homocoupling of quinoxalin-2(1H)-ones under mild conditions is developed. This practical scheme is compatible with a variety of functional groups and allows the preparation of functionalized unsymmetrical dimeric quinoxalin-2(1H)-ones from readily available and safe starting materials, providing new ideas for the sustainable development of methodological studies of quinoxalin-2(1H)-ones.

Catalytic Enantioselective Synthesis of Inherently Chiral Molecules: Recent Advances

AbstractInherent chirality represents a distinct category of molecular chirality that does not fall within the traditional classification of four chiral elements: central, axial, planar, and helical chirality. While extensive research has been conducted on the catalytic enantioselective construction of these conventional chiralities, the corresponding synthesis of inherently chiral molecules has remained largely unexplored. This minireview provides a comprehensive summary of recent advancements in this field, focusing on the catalytic asymmetric synthesis of inherently chiral calixarenes, saddle‐shaped tetraphenylenes and their heterocycle derivatives, mechanically planar chiral rotaxanes and chiral multilayer 3D frameworks, as well as our perspective in this field.

Tetrachlorovancomycin: Total Synthesis of a Designed Glycopeptide Antibiotic of Reduced Synthetic Complexity.

A technically straightforward total synthesis of a new class of vancomycin analogues of reduced synthetic complexity was developed that provided tetrachlorovancomycin (1, LLS = 15 steps, 15% overall yield) and its precursor aglycon 29 (nearly 20% overall yield). The class retains all the intricate vancomycin structural features that contribute to its target binding affinity and selectivity, maintains the antimicrobial activity of vancomycin, and achieves the simplification by an unusual addition, not removal, of benign substituents to the core structure. The modification, accomplished by addition of two aryl chloride substituents to provide 1, permitted a streamlined total synthesis of the new glycopeptide antibiotic class by removing the challenges associated with CD and DE ring system atropisomer stereochemical control. This also enabled their simultaneous and further-activated SNAr macrocyclizations that establish the tricyclic skeleton of 1. Key elements of the approach include catalyst-controlled diastereoselective formation of the AB biaryl axis of chirality (>30:1 dr), an essentially instantaneous macrolactamization of the AB ring system free of competitive epimerization (>30:1 dr), racemization free coupling of the E ring tetrapeptide, room temperature simultaneous CD and DE ring system cyclizations, a highly refined 4-step conversion of the cyclization product to the aglycon, and a protecting-group-free one-pot enzymatic glycosylation for disaccharide introduction. In addition to the antimicrobial evaluation of tetrachlorovancomycin (1), the preparation of key peripherally modified derivatives, which introduce independent and synergistic mechanisms of action, revealed their exceptional antimicrobial potency and provide the foundation for future use of this new class of synthetic glycopeptide analogues.

Constructing Highly Efficient Circularly Polarized Multiple Resonance Thermally Activated Delayed Fluorescence Materials with Intrinsically Helical Chirality.

Advanced circularly polarized multiple resonance thermally activated delayed fluorescence (CP-MR-TADF) materials synergize the advantages of circularly polarized luminescence (CPL), narrowband emission and TADF characteristic, which can be fabricated into highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs) with high color purity, directly facing the urgent market strategic demand of ultra-high-definition and 3D displays. In this contribution, based on edge topology molecular engineering (ETME) strategy, a pair of high-performance CP-MR-TADF enantiomers, (P and M)-BN-Py, has been developed, which merges the intrinsically helical chirality into MR framework. The optimized CP-OLEDs with emitters (P and M)-BN-Py and the newly developed ambipolar transport host PhCbBCz exhibit pure green emission with sharp peaks of 532nm, full-width at half-maximums (FWHMs) of 37nm, and Commission Internationale de L'Eclairage (CIE) coordinates of (0.29, 0.68). Importantly, they achieve remarkable maximum external quantum efficiencies (EQEs) of 30.6% and 29.2%, and clear circularly polarized electroluminescence (CPEL) signals with electroluminescence dissymmetry factors (gEL s) of -4.37 × 10-4 and +4.35 × 10-4 for (P)-BN-Py and (M)-BN-Py, respectively. This article is protected by copyright. All rights reserved.

Observing Axial Chirality of Chiral Single-Wall Carbon Nanotubes by Helicity-Dependent Raman Spectra.

Helicity-dependent Raman spectra of an isolated, chiral, single-wall carbon nanotube (SWNT) are reported using circularly polarized light. A polar plot of polarized Raman intensity for the radial breathing mode (RBM), which is excited by left-handed or right-handed circularly polarized light, shows asymmetric angle dependence relative to the nanotube axis direction, which reflects the axial chirality of a SWNT. The asymmetry in the polar plot of the RBM can be analyzed by a complex Raman tensor. The complex phase of each component of the Raman tensor has a maximum at chiral angle θ = 15° of a SWNT which is between two achiral SWNTs, that is, zigzag (θ = 0°) and armchair (θ = 30°) SWNTs. Considering the interaction between the chiral SWNT and the circularly polarized light, we discuss the origin of the complex phases excited by the opposite helicity of the circularly polarized light.

Functionalization of Pentacene: A Facile and Versatile Approach to Contorted Polycyclic Aromatic Hydrocarbons.

In this work, a facile and versatile strategy for the synthesis of contorted polycyclic aromatic hydrocarbons (PAHs) starting from the functionalized pentacene was established. A series of novel PAHs 1-4 and their derivatives were synthesized through a simple two-step synthesis procedure involving an intramolecular reductive Friedel-Crafts cyclization of four newly synthesized pentacene aldehydes 5-8 as a key step. All the molecules were confirmed by single-crystal X-ray diffraction and their photophysical and electrochemical properties were studied in detail. Interestingly, the most striking feature of 1-4 is their highly contorted carbon structures and the accompanying helical chirality. In particular, the optical resolution of 2 was successfully achieved by chiral-phase HPLC, and the enantiomers were characterized by circular dichroism and circularly polarized luminescence spectroscopy. Despite the highly nonplanar conformations, these contorted PAHs exhibited emissive properties with moderate-to-good fluorescence quantum yields, implying the potential utility of this series PAHs as high-quality organic laser dyes. By using a self-assembly method with the help of epoxy resin, a bottle microlaser based on 3 a was successfully illustrated with a lasing wavelength of 567.8 nm at a threshold of 0.3 mJ/cm2 . We believe that this work will shed light on the chemical versatility of pentacene and its derivatives in the construction of novel functionalized PAHs.

Catalytic Asymmetric Synthesis of Atropisomers Featuring an Aza Axis.

ConspectusAtropisomers bearing a rotation-restricted axis are common structural units in natural products, chiral ligands, and drugs; thus, the prevalence of asymmetric synthesis has increased in recent decades. Research into atropisomers featuring an N-containing axis (N-X atropisomers) remains in its infancy compared with the well-developed C-C atropisomer analogue. Notably, N-X atropisomers could offer divergent scaffolds, which are extremely important in bioactive molecules. The asymmetric synthesis of N-X atropisomers is recognized as both appealing and challenging. Recently, we devoted our efforts to the catalytic asymmetric synthesis of N-X atropisomers, benzimidazole-aryl N-C atropisomers, indole-aryl N-C atropisomers, hydrogen-bond-assisted N-C atropisomers, pyrrole-pyrrole N-N atropisomers, pyrrole-indole N-N atropisomers, and indole-indole N-N atropisomers. To obtain the N-C atropisomers, an asymmetric Buchwald-Hartwig reaction of amidines or enamines was employed. Using a Pd(OAc)2/(S)-BINAP or Pd(OAc)2/(S)-Xyl-BINAP catalyst system, benzimidazole-aryl N-C atropisomers and indole-aryl N-C atropisomers were readily obtained. To address the issue of the reduced stability of the diarylamine axis, a six-membered intramolecular N-H-O hydrogen bond was introduced into the N-C atropisomer scaffold. A tandem N-arylation/oxidation process was used for the chiral phosphoric acid (CPA)-catalyzed asymmetric synthesis of N-aryl quinone atropisomers. For N-N atropisomers, a copper-mediated asymmetric Friedel-Crafts alkylation/arylation reaction was developed. The desymmetrization process was completed successfully via a Cu(OTf)2/chiral bisoxazoline or (CuOTf)·Tol/bis(phosphine) dioxide system, thereby achieving the first catalytic asymmetric synthesis of N/N bipyrrole atropisomers. Asymmetric Buchwald-Hartwig amination of enamines was utilized to provide N-N bisindole atropisomers with excellent stereogenic control. This was the first asymmetric synthesis of N-N atropisomers featuring a bisindole structural scaffold using the de novo indole construction strategy. The asymmetric N-N heterobiaryl atropisomer synthesis was substantially facilitated using palladium-catalyzed transient directing group (TDG)-mediated C-H functionalization. Atropisomeric alkenylation, allylation, or alkynylation was accomplished using the Pd(OAc)2/l-tert-leucine system. Herein, we summarize our work on the palladium-, copper-, and CPA-catalyzed asymmetric syntheses of N-C and N-N atropisomers. Furthermore, the application of our work in the synthesis of bioactive molecule analogues and axially chiral ligands is demonstrated. Subsequently, the stability of the chiral N-containing axis is briefly discussed in terms of single crystals and obtained rotational barriers. Finally, an outlook on the asymmetric N-X atropisomer synthesis is provided.

Functionalization of Pentacene: A Facile and Versatile Approach to Contorted Polycyclic Aromatic Hydrocarbons

AbstractIn this work, a facile and versatile strategy for the synthesis of contorted polycyclic aromatic hydrocarbons (PAHs) starting from the functionalized pentacene was established. A series of novel PAHs 1–4 and their derivatives were synthesized through a simple two‐step synthesis procedure involving an intramolecular reductive Friedel–Crafts cyclization of four newly synthesized pentacene aldehydes 5–8 as a key step. All the molecules were confirmed by single‐crystal X‐ray diffraction and their photophysical and electrochemical properties were studied in detail. Interestingly, the most striking feature of 1–4 is their highly contorted carbon structures and the accompanying helical chirality. In particular, the optical resolution of 2 was successfully achieved by chiral‐phase HPLC, and the enantiomers were characterized by circular dichroism and circularly polarized luminescence spectroscopy. Despite the highly nonplanar conformations, these contorted PAHs exhibited emissive properties with moderate‐to‐good fluorescence quantum yields, implying the potential utility of this series PAHs as high‐quality organic laser dyes. By using a self‐assembly method with the help of epoxy resin, a bottle microlaser based on 3 a was successfully illustrated with a lasing wavelength of 567.8 nm at a threshold of 0.3 mJ/cm2. We believe that this work will shed light on the chemical versatility of pentacene and its derivatives in the construction of novel functionalized PAHs.

Improved mechanical performance of quasi-cubic lattice metamaterials with asymmetric joints

In this paper, we propose a simple method for the modification of the unit cells in the lattice metamaterials that provides an improvement of their impact strength. The idea is based on the introduction of small mutual offsets of the interconnected struts inside the unit cells. In such way, the joints between the struts become asymmetric and the overall geometry of the unit cells can be defined as the quasi-cubic with the axis of chirality. Considering four types of cubic lattices with BCC, BCT, FCC and octahedron structures, we modified their geometry and investigated the influence of the offsets and the unit cell size on the overall performance in static and dynamic tests. From the experiments we found that the small offsets (less than the strut diameter) can allow to increase the impact strength of 3d-printed polymeric specimens in 1.5–3 times remaining almost the same density and static mechanical properties. Based on the numerical simulations, we show that the explanation of the observed phenomena can be related to the increase of plastic deformations and damage accumulation in the unit-cells with asymmetric joints leading to the transition from the quasi-brittle to the ductile type of fracture in tested specimens.