Fused Ring Compounds Research Articles

A π-Stacked Highly Stable, Insensitive, Energy-Containing Material with a Useful Planar Structure

Abstractπ-Stacking is common in materials, but different π–π stacking modes remarkably affect the properties and performances of materials. In particular, weak interactions, π-stacking and hydrogen bonding often have a significant impact on the stability and sensitivity of high-energetic compounds. A fused [5,7,5]-tricyclic energetic compound with a conjugated structure has been designed and synthesized. 4H-[1,2,5]Oxadiazolo[3,4-e][1,2,4]triazolo[3,4-g][1,2,4]triazepin-8-amine is obtained in 48% yield from 3-amino-4-carboxy-1,2,5-oxadiazole through an efficient two-step reaction. Owing to its layered planar structure and weak π interactions between layers, 4H-[1,2,5]oxadiazolo[3,4-e][1,2,4]triazolo[3,4-g][1,2,4]triazepin-8-amine exhibits high thermal stability (T d = 318 °C), low sensitivity (IS = 40 J, FS = 360 N), and relatively excellent detonation performance (D = 7059 ms–1, P = 20.2 GPa). This detonation performance is superior to that of the conventional explosive TNT. The developed procedure provides a new method for the synthesis of fused ring compounds.

Unveiling the influence of end-capped acceptors modification on photovoltaic properties of non-fullerene fused ring compounds: a DFT/TD-DFT study.

Herein, unique A-D-A configuration-based molecules (NBD1-NBD7) were designed from the reference compound (NBR) by utilizing the end-capped acceptor modification approach. Various electron-withdrawing units -F, -Cl, -CN, -NO2, -CF3, -HSO3, and -COOCH3, were incorporated into terminals of reference compound to designed NBD1-NBD7, respectively. A theoretical investigation employing the density functional theory (DFT) and time-dependent DFT (TD-DFT) was performed at B3LYP/6-311G(d,p) level. To reveal diverse opto-electronic and photovoltaic properties, the frontier molecular orbitals (FMOs), absorption maxima (λ max), density of states (DOS), exciton binding energy (E b), open-circuit voltage (V oc) and transition density matrix (TDM) analyses were executed at the same functional. Moreover, the global reactivity parameters (GRPs) were calculated using the HOMO-LUMO energy gaps from the FMOs. Significant results were obtained for the designed molecules (NBD1-NBD7) as compared to NBR. They showed lesser energy band gaps (2.024-2.157 eV) as compared to the NBR reference (2.147 eV). The tailored molecules also demonstrated bathochromic shifts in the chloroform (671.087-717.164 nm) and gas phases (623.251-653.404 nm) as compared to NBR compound (674.189 and 626.178 nm, respectively). From the photovoltaic perspectives, they showed promising results (2.024-2.157 V). Furthermore, the existence of intramolecular charge transfer (ICT) in the designed compounds was depicted via their DOS and TDM graphical plots. Among all the investigated molecules, NBD4 was disclosed as the excellent candidate for solar cell applications owing to its favorable properties such as the least band gap (2.024 eV), red-shifted λ max in the chloroform (717.164 nm) and gas (653.404 nm) phases as well as the minimal E b (0.126 eV). This is due to the presence of highly electronegative -NO2 unit at the terminal of electron withdrawing acceptor moiety, which leads to increased conjugation and enhanced the intramolecular charge transfer (ICT) rate. The obtained insights suggested that the designed molecules could be considered as promising materials for potential applications in the realm of OSCs.

Carbene-Assisted Arene Ring-Opening.

Despite the significant achievements in dearomatization and C-H functionalization of arenes, the arene ring-opening remains a largely unmet challenge and is underdeveloped due to the high bond dissociation energy and strong resonance stabilization energy inherent in aromatic compounds. Herein, we demonstrate a novel carbene assisted strategy for arene ring-opening. The understanding of the mechanism by our DFT calculations will stimulate wide application of bulk arene chemicals for the synthesis of value-added polyconjugated chain molecules. Various aryl azide derivatives now can be directly converted into valuable polyconjugated enynes, avoiding traditional synthesis including multistep unsaturated precursors, poor selectivity control, and subsequent transition-metal catalyzed cross-coupling reactions. The simple conditions required were demonstrated in the late-stage modification of complex molecules and fused ring compounds. This chemistry expands the horizons of carbene chemistry and provides a novel pathway for arene ring-opening.

Host-guest doped room/high-temperature phosphorescence of diarylfuro[3,2-b]pyridine derivatives

Due to the high temperature that can easily lead to non-radiative transitions of triplet excitons, obtaining high-temperature phosphorescence (HTP) materials is challenging. Herein, using diarylfuro[3,2-b]pyridines as the guest molecules and polyacrylic acid (PAA) as the host molecule, the two-component doped materials exhibit green room-temperature phosphorescence (RTP) with afterglow times of 2–8 s, delayed lifetimes of 256–939 ms, and phosphorescence quantum efficiencies of 140.3–21.2 %, and green HTP emissions with 2 s afterglow and 208 ms delayed lifetime at 373 K. The HTP activity of the doped system originates from the rigid environment provided by PAA, planar and rigid molecular structures of diarylfuro[3,2-b]pyridines, and strong interactions between PAA and diarylfuro[3,2-b]pyridines. Furthermore, using organic small molecules as the reference host molecules, compared to benzophenone, 5-methylphthalic anhydride, and butane-1,2,3,4-tetracarboxylic acid with chemical structures similar to PAA result in better RTP/HTP properties, revealing that strong interactions between host and guest molecules play a very important role in ultralong phosphorescence emissions of these host–guest doped materials. Moreover, these doped materials based on diarylfuro[3,2-b]pyridines can be developed as advanced anti-counterfeiting and encryption materials. This result provides valuable reference for developing excellent RTP/HTP materials based on N,O-containing fused-ring compounds.

Fused-ring compounds with a N–B–N unit for efficient blue OLEDs

Fused-ring compounds containing a N–B–N (NBN) unit have emerged as a class of emitters for organic light-emitting diodes (OLEDs) in recent years. However, despite the success of these compounds in achieving efficient green OLEDs, their application in blue OLEDs has not yet been realized. In this study, two new NBN-containing compounds featuring unsymmetrical molecular structures are designed and synthesized. The structural design endows the compounds with efficient blue emission and narrower emission bandwidths. A blue fluorescent OLED based on one of the compounds exhibits simultaneously a high external quantum efficiency of 4.2% and an excellent Commission Internationale de L'Eclairage (CIE) coordinate of (0.152, 0.096). The impressive performance of the OLED device suggests that with proper molecular designs, NBN-containing compounds possess great potential as excellent blue emitters for OLEDs, and thus merit further investigation and attention.

Multi-colour room-temperature phosphorescence from fused-ring compounds for dynamic anti-counterfeiting applications.

We present a facile strategy to achieve purely organic multi-colour room-temperature phosphorescence (RTP) films by doping typical fused-ring compounds into a poly(vinyl alcohol) matrix. Such RTP films demonstrate inherent RTP emission ranging from green to red with a long lifetime and high quantum yield (QY) (lifetime: ∼0.56 ms, QY: ∼35.4%). We further exploit such high-performance RTP films for dynamic information encryption.

Towards improved comprehensive energetic properties by skeleton modification

Skeleton modification can expand pathways to tune the comprehensive properties for energetic compounds. In this work, skeleton modification was applied to the preparation of a family of new nitramine substituted [1,2,4]triazolo[3,4-f][1,2,4]triazine fused ring compounds.

Preparation of novel heat-resistant and insensitive fused ring energetic materials

Compared with traditional polycyclic-based heterocyclic energetic compounds, the synthesis of fused ring compounds is more challenging since only a few substrates meet the structural requirements for a fused cyclization reaction.

Diastereoselective Synthesis of Allenes through Phosphine-Catalyzed Cascade Isomerization/Annulation.

Phosphine-catalyzed cascade isomerization/annulation has been developed to realize a diastereoselective synthesis of allenes installed on the hexahydropentalene skeleton, which contains five chiral centers (and one axial chirality). This reaction tolerated a broad range of allenoates and enynes. The allene products were transformed to various halogen-substituted fused-ring compounds.

Thermostable Insensitive Energetic Materials Based on a Triazolopyridine Fused Framework with Alternating Nitro and Amine Groups

AbstractIn this work, we designed and synthesized a series of novel triazolopyridine fused-ring compounds with alternating nitro and amine groups. Three compounds showed remarkable thermal stability at 256, 310, and 294 °C, respectively, and a low mechanical sensitivity [impact sensitivity (IS) = 40 J, friction sensitivity (FS) = 324 N; IS = 35 J, FS = 240 N; and IS > 40 J, FS = 324 N, respectively]. Significantly, two of these compounds exhibited a better detonation performance [detonation velocity (D) = 8200 and 8335 m s–1, Detonation pressure (P) = 25.6 and 27.2 GPa, respectively] than the widely used heat-resistant explosive hexanitrostilbene (HNS; D = 7612 m s–1, P = 24.3 GPa). Additionally, a nitramine derivative displayed a detonation performance (D = 8569 m s–1, P = 31.3 GPa) similar to that of the high-energy explosive RDX. The superior properties of the materials were further confirmed by X-ray diffraction analysis and by several theoretical calculations (ESP, LOL–π, Hirshfeld surfaces, RDG, and NCI analyses). These results indicated that the three compounds might be potential candidates for use as heat-resistant energetic materials.

Pyrrole-contained fused-ring compounds

Three series of pyrrole-contained fused ring compounds are summarized. In recent years, these compounds attracted wide attention with their special and elegant structures. Furthermore, they have played important roles in new optoelectronic materials and guest receptors due to their excellent photoelectric effects and unique properties with nitrogen atom doping.

Microwave-Assisted C–C Bond Formation to Access Fused-Ring Compounds

Microwave-Assisted C–C Bond Formation to Access Fused-Ring Compounds

Influence of azo-based donor modifications on nonlinear optical amplitude of D-π-A based organic chromophores: A DFT/TD-DFT exploration

Organic heterocyclic fused ring compounds possess remarkable nonlinear optical (NLO) amplitude, are potentially employed in optical computing and nano-photonics. Herein, ITTBCR1 was quantum chemically modified into a series of novel D-π-A configured NLO compounds (ITTBCD2-ITTBCD6) by substituting various efficient donor moieties. To investigate the electronic, photophysical, and NLO properties, ITTBCR1 and ITTBCD2-ITTBCD6 were subjected to density functional theory (DFT) and time-dependent DFT calculations at M06/6–311 G(d,p) level of theory. Frontier molecular orbital analysis (FMOs) illustrated that the newly designed chromophores exhibit smaller energy gaps (1.625–2.013 eV) compared to ITTBCR1 (2.384 eV). The global reactivity parameters estimated through Egap revealed higher softness (σ = 0.49–0.61 Eh) values, implying enhanced reactivity of ITTBCD2-ITTBCD6 compounds. An efficient push-pull mechanism disclosed positive charges on donors and π-spacers, while the acceptor moieties exhibited a negative charge. The presence of charge separation states and the substantial involvement of molecular orbitals in the charge transfer were explored by natural bond orbitals (NBOs), transition density matrix and density of states analyses. The UV-Vis study of the designed compounds displayed larger bathochromic shifts with wider absorption spectra. Also, a significantly large NLO behavior was found in all the novel entities (ITTBCD2-ITTBCD6), thus potentially employable as NLO materials. Inclusively, compound ITTBCD5 demonstrated highest linear polarizability (〈α〉 = 2.250 ×103a.u.), and first hyperpolarizability (βtot = 70.155 ×104a.u.), therefore proposed as the most proficient NLO material. Comparative study for NLO properties at various functional showed that at M06/6–311 G (d,p) significant NLO results could be obtained. The current investigation revealed that by controlling the type of donor motifs, numerous NLO compounds can be designed, which are equally productive in hi-tech NLO applications.

Synthesis of Two Series of Isomeric Triazolo-Triazine Fused Energetic Salts: High Thermal Stability, Insensitivity, and High Performances

In recent years, the safety of energetic materials has attracted more and more attention. How to design and synthesize heat-resistant and insensitive energetic materials has become an urgent problem to be solved. In this work, two series of energetic salts based on isomeric triamino triazolo-triazine fused-ring compounds were designed and synthesized by incorporating oxygen-rich anions (such as NO3– or ClO4–) with nitrogen-rich energetic cations. All of the new compounds were fully characterized by infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), elemental analysis, and differential scanning calorimetry (DSC). Decomposition temperatures (Td) of isomeric perchlorate salts 3 and 9 are 315 and 364 °C, respectively. Their different properties, densities and molecular stabilities are rationally explained based on crystal structures and packing patterns. Meanwhile, perchlorate 9 has the highest decomposition temperature and good detonation performance (D = 8485 m s–1, P = 27.7 GPa), which is superior to HNS and PYX and suggests that it could be applied as a heat-resistant insensitive explosive.

Solid-State Luminescence Stimulus-Responsive Property and Doped RTP Emission of Novel 7a,8,10,11-Tetrahydro-9H- pyrido[2',1':2,3][1,3]oxazino[6,5,4-ij]isoquinoline Derivative.

A novel 7a,8,10,11-tetrahydro-9H-pyrido[2',1':2,3][1,3]oxazino[6,5,4-ij]isoquinoline derivative (POIQ) is accidentally obtained from an isoquinoline derivative and iodine in dimethyl sulfoxide, which is demonstrated to undergo a mechanism of demethylation and thus intramolecular nucleophilic substitution. POIQ with twisted molecular conformation and loose stacking arrangement shows multifunctional optical properties including dual-state emission, mechanochromic, and solid-state acidochromic activities. Furthermore, an organic room temperature phosphorescence (RTP) doped system with green afterglow of 2 s is constructed using POIQ as the guest and easily available phenyl benzoate as the host, in which the host molecules assist in the transfer of the triplet excitons of the guest molecules. Rewritable optical recording media and information encryption are alsorealized based on multifunctional optical properties of this compound. This work provides inspiration for the development of N,O-containing fused-ring compounds with fluorescence/RTP properties.

Self-Assembly Fabrication of Energetic Perchlorates with High Density and Near-Infrared Laser Ignition Capacity

In this work, four energetic compounds (1–4) were prepared through the combination of nitrogen-rich heterocyclic fused-ring compounds and perchloric acid via a self-assembly methodology. The densities of these compounds were higher than 1.92 g cm–3, and compound 2 exhibited the highest density of 2.04 g cm–3, which exceeded those of most of the traditional energetic compounds. The calculated detonation velocity, detonation pressure, and specific impulse of compound 2 were 9317 m s–1, 41.1 GPa, and 264 s, respectively; these values were greater than those of high-energy and high-density material 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Furthermore, compound 1 is the first example of metal-free energetic materials with near-infrared (λ = 1064 nm) laser ignition ability. The high densities and excellent energetic performances of these compounds indicate that self-assembly is a promising approach for the development of advanced energetic materials.

Cobalt-Catalyzed Nitrogen Atom Insertion in Arylcycloalkenes.

Developing strategies enabling the modification of underlying molecular frameworks facilitates access to underexplored chemical spaces. Skeletal editing is an emerging technology for late-stage diversification of bioactive molecules. However, the current state of this knowledge remains undeveloped. This work describes a simple protocol that "inserts" a nitrogen atom into arylcycloalkenes to form the corresponding N-heterocycles. The use of an inexpensive cobalt catalyst under aqueous and open-air conditions makes this protocol very practical. Examples of late-stage modification of compounds of pharmaceutical interest and complex fused ring compounds further demonstrated the potentially broad applicability of this methodology.

Donor-Acceptor Type of Fused-Ring Thermally Activated Delayed Fluorescence Compounds Constructed through an Oxygen-Containing Six-Membered Ring.

Nowadays, thermally activated delayed fluorescence (TADF) compounds with a fused-ring core skeleton are getting increasing research interest because of their use in high-performance organic light-emitting diodes (OLEDs). In this study, TADF compounds featuring a D-A-type fused-ring core skeleton are developed. The challenging compatibility of a planarized D-A arrangement and the TADF property is achieved through linking the D and A moieties with two oxygen atoms within a six-membered ring. Compared with a single-oxygen analogue possessing a flexible skeleton and a twisted D-A arrangement, these fused-ring compounds with higher skeleton rigidity show higher photoluminescence quantum yields and narrower emission spectra in toluene and in doped thin films. Their electroluminescent devices achieve high external quantum efficiencies (up to 19.4%), suggesting the potential of rarely achieved D-A-type fused-ring TADF systems to serve as high-performance emitters of OLEDs.

Palladium-Catalyzed Borylative Cyclizations of α-(2-Bromoaryl) Ketones to Form 1,2-Benzoxaborinines.

Herein, we report that palladium catalyzes the borylative cyclization of α-(2-bromoaryl) ketones to afford 1,2-benzoxaborinines. The developed system is compatible with a variety of functionalities (Me, t-Bu, OMe, NMe2, F, Cl, CN, CF3, CO2Me, and heteroaryl groups) and is applicable to the synthesis of B-O-containing tri- and tetracyclic fused-ring compounds.

Synthesis, nematicidal evaluation, and SAR study of benzofuran derivatives containing 2-carbonyl thiophene

Plant-parasitic nematodes are major threat for crop protection. The lack of nematicides with new mode of action and increasing resistance raises the need for novel nematicides. In order to seek new nematicidal lead, originating from the structure of chalcone, a series of fused ring compounds was obtained by ring closure design strategy. These compounds were modified further. The nematicidal activity against M. incognita of synthesized compounds was evaluated. The bioassay showed that compound 3 and some of its derivatives such as compounds 18, 19, 21, 22, 23, 24 and 26 exhibited excellent nematicidal activity. Among them, compound 23 exhibited significant bioactivity. The LC50/72 h value reached 3.20 mg/L in vitro and the inhibition rate was 100.00% at 40 mg/L in the matrix. The structure-activity relationship of synthesized compounds was discussed in details. The influence of compound 23 on egg hatching, motility, and feeding behavior of C. elegans was also evaluated.