Theoretical simulation of TADF character of 3,9'-bicarbazole-modified 2,4,6-triphenyl-1,3,5-triazine.

CONTEXT: Three donor (D)-acceptor (A)-type temperature-activated delayed fluorescent (TADF) molecules of 9-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-3,9'-bicarbazole (o-TrzDCz), 9-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-3,9'-bicarbazole (m-TrzDCz), and 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-3,9'-bicarbazole (p-TrzDCz) were designed in this paper, and the photophysical properties, including the intersystem crossing rate, the reorganization energies (λ), and the intersystem crossing/reverse intersystem crossing (ISC/RISC) rate, were simulated to explore the effect of substitution sites on their TADF character. The values of the twist angle between the D and A moieties in ground state and the molecular root-mean-square deviation (RMSD) of the S1 and T1 states referenced to the S0 state indicate that o-TrzDCz possess bigger steric hindrance and stabler molecular configuration. The λ values of the ISC/RISC process should be 0.06/0.04 eV for o-TrzDCz, which are much smaller than those of m-TrzDCz (0.51/0.41 eV) and p-TrzDCz (1.93/1.06 eV). At the same time, o-TrzDCz possess the biggest kRISC (7.28 × 106 s-1) and kr (3.12 × 106 s-1) values and the smallest kp (0.10 s-1) value among the three titled molecules. These data indicate that o-TrzDCz should have more excellent TADF character than m-TrzDCz and p-TrzDCz. In a word, this research presents that adjusting the molecular linking manner should be a charming way to explore novel high-efficient TADF molecules. METHODS: Quantum chemical calculations were performed at PBE0/6-31G* level by Gaussian 09 and ORCA 4.1.0 software packages, and reorganization energies and Huang-Rhys were performed by the DUSHIN program and MOMAP 2019B software package based on the Gaussian 09 output files, while the phosphorescence rates were performed at B3LYP/6-31G* level by Dalton 2021.

Magnetofluid-integrated biosensors based on DNase-dead Cas12a for visual point-of-care testing of HIV-1 by an up and down chip.

The CRISPR Cas system, as a novel nucleic acid detection tool, is often hindered by cumbersome experimental procedures, complicated reagent transfer processes, and associated aerosol pollution risks. In this study, an integrated nucleic acid detection platform named "up and down chip" was developed, which combined RT-RAA technology for nucleic acid amplification, DNase-dead Cas12a-modified magnetic beads for specific recognition of target nucleic acid, and HRP-TMB chromogenic reaction for signal output in different chambers of a single microfluidic chip. The magnetic beads were migrated in an up-and-down manner between different chambers through magnetic driving, achieving a "sample-in, result-out" detection mode. By introducing a homemade heating box for temperature control during the reaction and using the naked eye or a smartphone APP for color-based signal reading, no professional or precise instruments were required in this platform. Using this platform, highly sensitive detection of the HIV-1 genome as low as 250 copies (CPs) per mL was achieved within 100 min while maintaining good detection performance against common variants as well as excellent specificity and anti-interference ability. In addition, compared with qRT-PCR, it also exhibited good accuracy for 56 spiked plasma samples, indicating its promising potential for clinical application.

Integration of a CRISPR Cas12a-assisted multicolor biosensor and a micropipette tip enables visible point-of-care testing of foodborne Vibrio vulnificus.

Foodborne pathogens cause numerous food safety problems, and as a virulent bacterium falling under this category, Vibrio vulnificus (V. vulnificus) poses a huge threat to public health. The conventional methods used for the detection of V. vulnificus, including culture-based and molecular detection methods, have a variety of drawbacks, including being time-consuming and labor-intensive, the requirement of large-scale equipment, and the lack of professional operators. This paper establishes a visible detection platform for V. vulnificus based on CRISPR/Cas12a, which is integrated with nucleic acid isothermal amplification and ß-galactosidase-catalyzed visible color reaction. The specific vvhA gene and a conservative segment in the 16S rDNA gene of the Vibrio genus were selected as the detection targets. By using spectrum analysis, this CRISPR detection platform achieved sensitive detection of V. vulnificus (1 CFU per reaction) with high specificity. Through the color transformation system, as low as 1 CFU per reaction of V. vulnificus in both bacterial solution and artificially contaminated seafood could be visibly observed with the naked eye. Furthermore, the consistency between our assay and the qPCR assay in the detection of V. vulnificus spiked seafood was confirmed. In general, this visible detection platform is user-friendly, accurate, portable, and equipment-free, and is expected to provide a powerful supplement in point-of-care testing of V. vulnificus and also holds good promise for future application in foodborne pathogen detection.

CRISPR Cas12a-enabled biosensors coupled with commercial pregnancy test strips for the visible point-of-care testing of SARS-CoV-2.

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has promoted the development of nucleic acid diagnosis technology. Several platforms with isothermal amplification methods have achieved sensitive and specific detection of SARS-CoV-2. However, they still suffer from complicated operations, delicate instruments, and unintuitive signal output modes. Here, a system consisting of CRISPR Cas12a-based biosensors and commercial pregnancy test strips (CRISPR-PTS) was established for the point-of-care testing of SARS-CoV-2. The target viral nucleic acids were finally reflected on the test strips through four steps, namely sample pretreatment, RT-RAA amplification, CRISPR Cas12a reaction, and separation-free hCG detection. This CRISPR-PTS assay possessed an outstanding sensitivity of as low as 1 copy per µL for SARS-CoV-2 detection and showed an excellent specificity in distinguishing the SARS-CoV-2 pseudovirus as well as other SARS-like viral clinical samples. In addition, the CRISPR-PTS assay performed well in practical applications, with 96.3% agreement versus RT-qPCR in spiked samples. With the advantages of low reagent cost, simple operation procedure, and visible signal output, CRISPR-PTS assay was expected to provide a strong supplement in the prevention and early diagnosis of infectious diseases in resource-limited situations.

Efficient poly(ß-L-malic acid) production from cassava hydrolysate by cell recycle of Aureobasidium pullulans.

Poly(ß-L-malic acid) (PMLA) is a water-soluble, biodegradable, and biocompatible polymer with broad prospective applications and can be hydrolyzed to produce widely used acidulant L-malic acid. In order to meet an increasing demand of PMLA, we employed two effective cell-recycling strategies to produce PMLA from raw cassava hydrolysate by Aureobasidium pullulans ZD-3d. In fed-batch fermentation with raw cassava hydrolysate, 101.9 g/L PMLA was obtained with the productivity and yield of 0.77 g/L/h and 0.40 g/g, respectively. Further, three times of membrane filtration-based cell recycling fermentation was carried out, with a high productivity and yield of 1.04-1.64 g/L/h and 0.5-0.84 g/g achieved, respectively. While harnessing centrifugation-based cell recycling fermentation for five times, the productivity and yield approached 0.98-1.76 g/L/h and 0.78-0.86 g/g, respectively. To our knowledge, the processes showed the highest average PMLA productivity compared with others using low-cost biomass, which offered efficient and economical alternatives for PMLA production. KEY POINTS: • PMLA production from raw cassava hydrolysate by Aureobasidium pullulans was studied • High PMLA productivity and yield were obtained via two cell recycling strategies • The highest average PMLA productivity from low-cost biomass to date was achieved.

Conjugated microporous polyarylimides immobilization on carbon nanotubes with improved utilization of carbonyls as cathode materials for lithium/sodium-ion batteries.

Aromatic polyimide (PI)-based compounds have been widely studied for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to their higher specific energy density, economical, environmentally friendly and adjustable redox potential window. However, their solubility in aprotic electrolytes, inherently poor conductivity and low active site utilization limit their application in large-scale energy storage system (ESS). Here, we synthesized two aromatic PI-based conjugated microporous polymers (CMPs) and integrated them with multi-walled carbon nanotubes (CNT) (TAPT-NTCDA@CNT and TAPT-PMDA@CNT) for using as cathode materials for LIBs and SIBs. The aromatic PI-based CMP can effectively utilize the redox activity site due to its abundant π-conjugated redox active units, stable imide bond, high specific surface area and clear pore structure. As expected, the optimum TAPT-NTCDA@CNT exhibits good rate performance (89.7 mAh g-1 at 2000 mA g-1) and long cycle stability (87.3% capacity retention after 500 cycles) in LIBs. Also, TAPT-NTCDA@CNT can provide a higher initial capacity of 91.1 mAh g-1 in SIBs at 30 mA g-1. This work provides key insights for the further development of other new organic electrodes for other advanced rechargeable batteries.

Carbonyl-rich Poly(pyrene-4,5,9,10-tetraone Sulfide) as Anode Materials for High-Performance Li and Na-Ion Batteries.

Organic carbonyl electrode materials are widely employed for alkali metal-ion secondary batteries in terms of their sustainability, structure designability and abundant resources. As a typical redox-active organic electrode materials, pyrene-4, 5, 9, 10-tetraone (PT) shows high theoretical capacity due to the rich carbonyl active sites. But its electrochemical behavior in secondary batteries still needs further exploration. Herein, PT-based linear polymers (PPTS) is synthesized with thioether bond as bridging group and then employed as an anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). As expected, PPTS shows improved conductivity and insolubility in the non-aqueous electrolyte. When used as an anode material for LIBs, PPTS delivers a high reversible specific capacity of 697.1 mAh g-1 at 0.1 A g-1 and good rate performance (335.4 mAh g-1 at 1 A g-1 ). Moreover, a reversible specific capacity of 205.2 mAh g-1 at 0.05 A g-1 could be obtained as an anode material for SIBs.

Polymerization and coordination synergistically constructed photothermal agents for macrophages-mediated tumor targeting diagnosis and therapy.

Developing an ideal photothermal agent is one of the challenges for effective photothermal therapy (PTT). Herein, a green and simple yet versatile method is developed to construct a novel poly-(iron-dopamine coordination complexes) nanoparticles (P[Fe-DA]-NPs) based on polymerization and coordination synergistically by using Fe3+ ions and dopamine (DA) in aqueous solution, and simultaneously poly(vinylpyrrolidone) (PVP) is applied to improve dispersion stability. P[Fe-DA]-NPs can be laden into macrophages directly with no further purification required to target tumor tissue to perform cell-mediated strategy. P[Fe-DA]-laden macrophages as an ideal photothermal agent has the advantages of good biocompatibility, simple preparation process, high photothermal performance, and effective tumor targeting. Furthermore, the P[Fe-DA]-laden macrophages possess excellent photoacoustic imaging (PAI) capacity for guiding the precise PTT. The results show that the tumors are significantly suppressed after PTT with the help of the accurate PAI diagnosis. This cell-mediated strategy may be the most promising avenue for the future clinical cancer therapy.

An Easy Method of Synthesis CoxOy@C Composite with Enhanced Microwave Absorption Performance.

Design of interface-controllable magnetic composite towards the wideband microwave absorber is greatly significance, however, it still remains challenging. Herein, we designed a spherical-like hybrids, using the Co3O4 and amorphous carbon as the core and shell, respectively. Then, the existed Co3O4 core could be totally reduced by the carbon shell, thus in CoxOy core (composed by Co and Co3O4). Of particular note, the ratios of Co and Co3O4 can be linearly tuned, suggesting the controlled interfaces, which greatly influences the interface loss behavior and electromagnetic absorption performance. The results revealed that the minimum reflection loss value (RLmin) of -39.4 dB could be achieved for the optimal CoxOy@C sample under a thin thickness of 1.4 mm. More importantly, the frequency region with RL < -10 dB was estimated to be 4.3 GHz, ranging from 13.7 to 18.0 GHz. The superior wideband microwave absorption performance was primarily attributed to the multiple interfacial polarization and matched impedance matching ability.

Development of sulfide, nitrogen co-doping hollow carbon with wideband electromagnetic absorption capability.

Exploration of an economic, easy-producing method to develop high-performance electromagnetic absorber has been a global research interest, owing to the increasingly electromagnetic pollution and interference. In this work, sulfide, nitrogen co-doping carbon (NS-HCS) has been successfully prepared by an in situ copolymer and subsequent calcination reaction. The morphologies and phase compositions of these as-prepared samples are analyzed via the transmission electron microscopy (TEM), element mappings, X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS). The result confirms the hollow shaped structure of amorphous carbon is constructed with various types of N, S based covalent bonds. The dotted N and S elements are contribution for the conductive loss and dipole polarization relaxation behavior. The minimum reflection loss value of -34 dB, and effective bandwidth reaches 6.8 GHz with only 1.6 mm. The as-prepared wideband electromagnetic absorber will pave a simple and effective method to obtain lightweight, broadband and thin thickness electromagnetic absorption materials.

A Self-Polymerized Nitro-Substituted Conjugated Carbonyl Compound as High-Performance Cathode for Lithium-Organic Batteries.

Conjugated carbonyl compounds have received much attention as cathode materials for developing green lithium-ion batteries (LIBs). However, their high dissolution and poor electronic conductivity in organic electrolyte restrict their further application. Herein, a self-polymerized nitro-substituted conjugated carbonyl compound (2,7-dinitropyrene-4,5,9,10-tetraone, PT-2 NO2 ) is applied as a high-performance cathode material for LIBs. PT-2 NO2 exhibits a high reversible capacity of 153.9 mAh g-1 at 50 mA g-1 after 120 cycles, which is higher than that of other substituted compounds. Detailed characterization and theoretical calculations have testified that PT-2 NO2 is transformed into an azo polymer through an irreversible reductive coupling reaction in the first discharge process, and then carbonyl and azo groups reversibly react with Li ions in subsequent cycles. In addition, this azo polymer is also synthesized and applied as the electrode material, which shows similar electrochemical performance to PT-2 NO2 but with higher initial coulombic efficiency. Thus, this work provides a simple but effectively way to construct organic cathode materials with multiple redox sites for green and high-performance LIBs.

Conjugated Carbonyl Polymer-Based Flexible Cathode for Superior Lithium-Organic Batteries.

Conjugated carbonyl compounds are deemed as high theoretical capacity and green electrode materials for lithium-ion batteries (LIBs) but are limited by their high dissolution and poor electronic conductivity. In this paper, we have successfully synthesized a series of multicarbonyl conjugated polymers using the coupling polymerization reaction and then constructed carbonyl-conjugated polymer/carbon nanotube hybrid films by a vacuum-filtration method. Importantly, the hybrid films could serve as a flexible, binder-free, and free-standing organic cathode for LIBs, which could deliver a high reversible discharge capacity of 142.3 mAh g-1 at 50 mA g-1, good cycling stability with a capacity retention of 74.6% at 500 mA g-1 after 300 cycles, and excellent rate capability of 120.6 mAh g-1 at 1000 mA g-1. In addition, the theoretical calculation has proved that the symmetrical conjugated structure can well accommodate four Li+ ions during the electrochemical reaction. Interestingly, the assembled full cell and flexible battery can power the small devices, suggesting its potential to use in bendable or wearable energy-storages devices.

A Bipolar and Self-Polymerized Phthalocyanine Complex for Fast and Tunable Energy Storage in Dual-Ion Batteries.

Bipolar redox organics have attracted interest as electrode materials for energy storage owing to their flexibility, sustainability and environmental friendliness. However, an understanding of their application in all-organic batteries, let alone dual-ion batteries (DIBs), is in its infancy. Herein, we propose a strategy to screen a variety of phthalocyanine-based bipolar organics. The self-polymerizable bipolar Cu tetraaminephthalocyanine (CuTAPc) shows multifunctional applications in various energy storage systems, including lithium-based DIBs using CuTAPc as the cathode material, graphite-based DIBs using CuTAPc as the anode material and symmetric DIBs using CuTAPc as both the cathode and anode materials. Notably, in lithium-based DIBs, the use of CuTAPc as the cathode material results in a high discharge capacity of 236 mAh g-1 at 50 mA g-1 and a high reversible capacity of 74.3 mAh g-1 after 4000 cycles at 4 A g-1 . Most importantly, a high energy density of 239 Wh kg-1 and power density of 11.5 kW kg-1 can be obtained in all-organic symmetric DIBs.

Engineering Charge Transfer Characteristics in Hierarchical Cu2S QDs @ ZnO Nanoneedles with p⁻n Heterojunctions: Towards Highly Efficient and Recyclable Photocatalysts.

Equipped with staggered gap p-n heterojunctions, a new paradigm of photocatalysts based on hierarchically structured nano-match-shaped heterojunctions (NMSHs) Cu2S quantum dots (QDs)@ZnO nanoneedles (NNs) are successfully developed via engineering the successive ionic layer adsorption and reaction (SILAR). Under UV and visible light illumination, the photocatalytic characteristics of Cu2S@ZnO heterojunctions with different loading amounts of Cu2S QDs are evaluated by the corresponding photocatalytic degradation of rhodamine B (RhB) aqueous solution. The results elaborate that the optimized samples (S3 serial specimens with six cycles of SILAR reaction) by means of tailored the band diagram exhibit appreciable improvement of photocatalytic activities among all synthesized samples, attributing to the sensitization of a proper amount of Cu2S QDs. Such developed architecture not only could form p⁻n junctions with ZnO nanoneedles to facilitate the separation of photo-generated carries but also interact with the surface defects of ZnO NNs to reduce the electron and hole recombination probability. Moreover, the existence of Cu2S QDs could also extend the light absorption to improve the utilization rate of sunlight. Importantly, under UV light S3 samples demonstrate the remarkably enhanced RhB degradation efficiency, which is clearly testified upon the charge transfer mechanism discussions and evaluations in the present work. Further supplementary investigations illustrate that the developed nanoscale Cu2S@ZnO heterostructures also possess an excellent photo-stability during our extensive recycling photocatalytic experiments, promising for a wide range of highly efficient and sustainably recyclable photocatalysts applications.

Medium optimization for pyrroloquinoline quinone (PQQ) production by Methylobacillus sp. zju323 using response surface methodology and artificial neural network-genetic algorithm.

Methylobacillus sp. zju323 was adopted to improve the biosynthesis of pyrroloquinoline quinone (PQQ) by systematic optimization of the fermentation medium. The Plackett-Burman design was implemented to screen for the key medium components for the PQQ production. CoCl2 · 6H2O, ρ-amino benzoic acid, and MgSO4 · 7H2O were found capable of enhancing the PQQ production most significantly. A five-level three-factor central composite design was used to investigate the direct and interactive effects of these variables. Both response surface methodology (RSM) and artificial neural network-genetic algorithm (ANN-GA) were used to predict the PQQ production and to optimize the medium composition. The results showed that the medium optimized by ANN-GA was better than that by RSM in maximizing PQQ production and the experimental PQQ concentration in the ANN-GA-optimized medium was improved by 44.3% compared with that in the unoptimized medium. Further study showed that this ANN-GA-optimized medium was also effective in improving PQQ production by fed-batch mode, reaching the highest PQQ accumulation of 232.0 mg/L, which was about 47.6% increase relative to that in the original medium. The present work provided an optimized medium and developed a fed-batch strategy which might be potentially applicable in industrial PQQ production.

Enhanced fed-batch production of pyrroloquinoline quinine in Methylobacillus sp. CCTCC M2016079 with a two-stage pH control strategy.

The effects of pH control strategy and fermentative operation modes on the biosynthesis of pyrroloquinoline quinine (PQQ) were investigated systematically with Methylobacillus sp. CCTCC M2016079 in the present work. Firstly, the shake-flask cultivations and benchtop fermentations at various pH values ranging from 5.3 to 7.8 were studied. Following a kinetic analysis of specific cell growth rate (µ x ) and specific PQQ formation rate (µ p ), the discrepancy in optimal pH values between cell growth and PQQ biosynthesis was observed, which stimulated us to develop a novel two-stage pH control strategy. During this pH-shifted process, the pH in the broth was controlled at 6.8 to promote the cell growth for the first 48 h and then shifted to 5.8 to enhance the PQQ synthesis until the end of fermentation. By applying this pH-shifted control strategy, the maximum PQQ production was improved to 158.61 mg/L in the benchtop fermenter, about 44.9% higher than that under the most suitable constant pH fermentation. Further fed-batch study showed that PQQ production could be improved from 183.38 to 272.21 mg/L by feeding of methanol at the rate of 11.5 mL/h in this two-stage pH process. Meanwhile, the productivity was also increased from 2.02 to 2.84 mg/L/h. In order to support cell growth during the shifted pH stage, the combined feeding of methanol and yeast extract was carried out, which brought about the highest concentration (353.28 mg/L) and productivity (3.27 mg/L/h) of PQQ. This work has revealed the potential of our developed simple and economical strategy for the large-scale production of PQQ.

Novel and efficient screening of PQQ high-yielding strains and subsequent cultivation optimization.

A novel and efficient screening method for pyrroloquinoline quinone (PQQ) high-yielding methylotrophic strains was developed by using glucose dehydrogenase apoenzyme (GDHA) which depended on PQQ as the cofactor. Using this high-throughput method, PQQ high-yielding strains were rapidly screened out from thousands of methylotrophic colonies at a time. The comprehensive phylogenetic analysis revealed that the highest PQQ-producing strain zju323 (CCTCC M 2016079) could be assigned to a novel species in the genus Methylobacillus of the Betaproteobacteria. After systematic optimization of different medium components and cultivation conditions, about 33.4 mg/L of PQQ was obtained after 48 h of cultivation with Methylobacillus sp. zju323 at the shake flask scale. Further cultivations of Methylobacillus sp. zju323 were carried out to investigate the biosynthesis of PQQ in 10-L bench-top fermenters. In the batch operation, the PQQ accumulation reached 78 mg/L in the broth after 53 h of cultivation. By adopting methanol feeding strategy, the highest PQQ concentration was improved up to 162.2 mg/L after 75 h of cultivation. This work developed a high-throughput strategy of screening PQQ-producing strains from soil samples and also demonstrated one potential bioprocess for large-scale PQQ production with the isolated PQQ strain.

Synthesis and characterization of ultraviolet light-emitting organic acids.

Three ultraviolet light-emitting organic acids of 3,3'-(4-phenyl-4H-1,2,4-triazole-3,5-diyl)dibenzoic acid (Tz-1), 4,4',4″-(4H-1,2,4-triazole-3,4,5-triyl)tribenzoic acid (Tz-2), and 4,4'-(4-(4'-carboxy-[1,1'-biphenyl]-4-yl)-4H-1,2,4-triazole-3,5-diyl)dibenzoic acid (Tz-3) were successfully synthesized and fully characterized by the (1)H NMR, the IR absorption spectra, and the X-ray single crystal diffraction. It was found that Tz-1, Tz-2, and Tz-3 could give out the ultraviolet photoluminescent spectra centered at 369 nm, 365 nm and 350 nm, respectively. The luminescence quantum yields of Tz-1 and Tz-2 were measured to be 0.20 and 0.14, respectively. Additionally, the density functional theory (DFT) and the time-dependent DFT calculations were also carried out for Tz-1, Tz-2, and Tz-3.

Bromidotricarbon-yl[2-phenyl-5-(pyridin-2-yl-κN)-1,3,4-oxadiazole-κN]rhenium(I) dichloro-methane monosolvate.

In the title rhenium(I) complex, [ReBr(C(13)H(9)N(3)O)(CO)(3)]·CH(2)Cl(2), the dichloro-methane solvent mol-ecule is disordered over two positions with an occupancy ratio of 0.81 (15):0.19 (15). The Re(I) atom is coordinated by two N atoms from a 2-phenyl-5-(pyridin-2-yl-κN)-1,3,4-oxadiazole (L) ligand, three C atoms from three carbonyl groups and a Br atom in a distorted octa-hedral geometry. The three rings in L are almost coplanar (a mean plane fitted through all non-H atoms of this ligand has an r.m.s. deviation of 0.063 Å), and the carbonyl ligands are coordinated in a fac arrangement.

Bromidotricarbon-yl[2-(pyridin-2-yl-κN)-5-p-tolyl-1,3,4-oxadiazole-κN]rhenium(I) dichloro-methane monosolvate.

In the title compound, [ReBr(C(14)H(11)N(3)O)(CO)(3)]·CH(2)Cl(2), the coordination geometry of the Re(I) atom is a distorted ReC(3)N(2)Br octa-hedron with the carbonyl C atoms in a fac arrangement. Within the 2-(pyridin-2-yl)-5-p-tolyl-1,3,4-oxadiazole ligand, the dihedral angles between the oxadiazole ring and the pyridine (py) and benzene (bz) rings are 1.7 (2) and 7.1 (2)°, respectively, and the dihedral angle between the py and bz rings is 5.5 (2)°. In the crystal, aromatic π-π stacking between the oxadiazole rings of adjacent mol-ecules [centroid-centroid separation = 3.465 (3) Å] is seen.