Acridine Ring Research Articles

Mer-M(CO)3(PNP)0/+ pincer complexes (M = W(0) or Re(I); PNP = 4,5-bis(diphenylphosphino)acridine): synthesis, spectroscopy and anti-Kasha emission.

Two isoelectronic and isostructural W(0) and Re(I) complexes mer-W(CO)3(PNP) (1) and [mer-Re(CO)3(PNP)]Cl (2) (PNP = 4,5-bis(diphenylphosphino)acridine) were synthesized and characterized by X-ray diffraction, infrared, electronic absorption and emission spectroscopy, and cyclic voltammetry. Structures of these complexes show a metal center bonded to the pincer ligand and two axial CO and one equatorial CO ligands. DFT calculations showed that the LUMOs of both complexes are the lowest energy π* orbitals localized in the acridine part of the ligand. The HOMO of 1 is dominated by the dπ orbital of W(0) while the HOMO of 2 has a substantial contribution from the highest energy π orbital of the acridine ring. TD-DFT calculations were performed to assist assignment of the UV-vis absorption spectra. The UV-vis absorption spectrum of 1 shows a very low energy W → π* (acridine) metal-to-ligand-charge-transfer (MLCT) absorption band that ranges from visible (500 nm) to near-infrared (>900 nm) regions and an intense acridine π → π* absorption band at 410 nm. There is a blue-green window in the ∼450-500 nm range between the π → π* and W → π*(acridine) MLCT absorptions. The absorption spectrum of 2, dominated by intense π → π* absorptions, shows no distinct low energy MLCT band. Complex 1 is luminescent, displaying acridine-based ππ* fluorescence at 501 nm which is anti-Kasha as it is higher in energy than the lowest energy excited state.

A "Pincer" Type of Acridine-Triazole Fluorescent Dye for Iodine Detection by Both 'Naked-Eye' Colorimetric and Fluorometric Modes.

Iodine, primarily in the form of iodide (I-), is the bioavailable form for the thyroid in the human body. Both deficiency and excess intake of iodide can lead to serious health issues, such as thyroid disease. Selecting iodide ions among anions has been a significant challenge for decades due to interference from other anions. In this study, we designed and synthesized a new pincer-type acridine-triazole fluorescent probe (probe 1) with an acridine ring as a spacer and a triazole as a linking arm attached to two naphthol groups. This probe can selectively recognize iodide ions in a mixed solvent of THF/H2O (v/v, 9/1), changing its color from colorless to light yellow, making it suitable for highly sensitive and selective colorimetric and fluorescent detection in water systems. We also synthesized another molecular tweezer-type acridine-triazole fluorescent probe (probe 2) that exhibits uniform detection characteristics for iodide ions in the acetonitrile system. Interestingly, compared to probe 2, probe 1 can be detected by the naked eye due to its circulation effect, providing a simple method for iodine detection. The detection limit of probe 1 is determined to be 10-8 mol·L-1 by spectrometric titration and isothermal titration calorimetry measurements. The binding stoichiometry between probe 1 and iodide ions is calculated to be 1:1 by these methods, and the binding constant is 2 × 105 mol·L-1.

Torsional Control of Frustrated Lewis Pair Behaviour Involving PNP‐type Phosphines

AbstractWe present convenient syntheses of a range of PNP‐type phosphines which feature a pair of ortho‐functionalized ArPPh2 moieties linked via a central NMe unit, but which differ in the nature of the additional backbone ‘tether’ linking the aryl groups. These comprise the acyclic system bis(2‐diphenylphosphinophenyl)methylamine, together with related systems centred around 5‐, 6‐ and 7‐membered heterocycles. Structurally, contraction of the backbone tether causes the phosphine centres to be projected further apart, and to be more constrained torsionally to the plane containing the NMe unit. In terms of potential frustrated Lewis pair (FLP) reactivity, the conformationally more flexible systems based on an acyclic linker or a cyclic core featuring a 7‐membered ring, are capable of achieving P−B bond formation and generating a classical Lewis adduct with B(C6F5)3. The less flexible carbazole‐derived compound (featuring a five membered heterocyclic core) gives rise to an FLP at room temperature, and an equilibrium mixture of frustrated and classical Lewis pairs at lower temperatures. Most interestingly, the PNP system based on a central six‐membered acridine ring ‐ which gives rise to the shortest contacts in the solid state between phosphorus and the N‐bound methyl group – undergoes C−H activation in the presence of B(C6F5)3, resulting in the formation of B−H and P−C bonds.

Strong chemiluminescence intensities of bis-acridinium esters under neutral and alkaline conditions

Four novel bis-acridinium esters were synthesized using common methods, and their chemiluminescence properties were investigated at pH 7−10. In the chemiluminescence of bis-acridinium esters, the introduction of fluorine at the 2-position of the phenyl ring and methyl groups at the 2,7-positions of the acridine ring changed greatly the chemiluminescence intensities. Pentane-1,5-diyl bis(2-fluoro-4-(2,7,10-trimethylacridinium-9-carbonyloxy)benzoate) bis(trifluoromethanesulfonate) showed strong chemiluminescence and long-lasting chemiluminescence under both neutral and alkaline conditions. Pentane-1,5-diyl bis(2-fluoro-4-(10-methylacridinium-9-carbonyloxy)benzoate) bis(trifluoromethanesulfonate) was applied for highly sensitive chemiluminescence determination of hydrogen peroxide and catalase activity. The linear calibration ranges of hydrogen peroxide and catalase activity were 5–1000 μM (R = 0.999) and 0.05−1 U/mL (R = 0.998), respectively.

Steric and Electronic Effects in N-Heterocyclic Carbene Gold(III) Complexes: An Experimental and Computational Study

A series of neutral acridine-based gold(III)-NHC complexes containing the pentafluorophenyl (-C6F5) group were synthesized. All of the complexes were fully characterized by analytical techniques. The square planar geometry around the gold center was confirmed by X-ray diffraction analysis for complexes 1 (Trichloro [1-methyl-3-(9-acridine)imidazol-2-ylidene]gold(III)) and 2 (Chloro-bis(pentafluorophenyl)[1-methyl-3-(9-acridine)imidazol-2-ylidene]gold(III)). In both cases, the acridine rings play a key role in the crystal packing of the solid structures by mean of π-π stacking interactions, with centroid-centroid and interplanar distances being similar to those found in other previously reported acridine-based Au(I)-NHC complexes. A different reactivity when using a bulkier N-heterocyclic carbene ligand such as 1,3-bis-(2,6-diisopropylphenyl)-2-imidazolidinylidene (SIPr) was observed. While the use of the acridine-based NHC ligand led to the expected organometallic gold(III) species, the steric hindrance of the bulky SIPr ligand led to the formation of the corresponding imidazolinium cation stabilized by the tetrakis(pentafluorophenyl)aurate(III) [Au(C6F5)4]- anion. Computational experiments were carried out in order to figure out the ground state electronic structure and the binding formation energy of the complexes and, therefore, to explain the observed reactivity.

Phase I Study of a Novel Oral Proteasome Inhibitor TQB3602 in Relapsed/Refractory Multiple Myeloma

Background: TQB3602 is a novel oral proteasome inhibitor with an acridine ring in addition to the main structure of ixazomib, which maintains better metabolic stability and higher activity and selectivity in preclinical models of multiple myeloma. TQB3602 consists of the L-malate ester with active boronic acid compound WXFL10410333 selectively targeting 20S proteasome enzyme. This is the first-in-human study to evaluate the safety, tolerability and pharmacokinetics of TQB3602 and assess the efficacy of TQB3602 combined with immunomodulators/dexamethasone regimen in relapsed/refractory multiple myeloma (RRMM). Study Design and Methods: This study is a multi-center open-label Phase I study in RRMM, consisting of the dose escalation phase and dose expansion phase. The inclusion criteria mainly include: 1) 18 to 75 years old male or female, 2) ECOG score of 0 to 2, 3) Life expectancy ≥12 weeks, 4) RRMM had received at least two treatment regimens (including lenalidomide or thalidomide, bortezomib, and glucocorticoid). The exclusion criteria mainly include: 1) grade ≥ 2 peripheral nerve diseases, 2) grade > 1 diarrhea during the screening period, 3) ixazomib has been administered less than five half-lives before the first dose of TQB3602, 4) previous allogeneic hematopoietic stem cell transplantation. TQB3602 was administered alone in 3+3 dose escalation (at a starting dose of 0.5mg on days 1, 8 and 15 in a 28-day cycle) until toxicity or disease progression in the dose escalation phase. According to prior lines of therapy, patients with RRMM were divided into two dose expansion cohorts, including TQB3602/lenalidomide/dexamethasone and TQB306/pomalidomide/dexamethasone (TQB3602 6mg on days 1, 8, 15, lenalidomide 25mg daily or pomalidomide 4mg daily on days 1 to 21, dexamethasone 20mg on days 1-2, 8-9, 15-16, 22-23 in a 28-day cycle). Results: The study enrolled 56 patients with RRMM including 25 patients in the dose escalation and 31 patients in the dose expansion between May 28, 2020 and July 20, 2022. The demographics and baseline characteristics were shown in table 1. Patients received single-agent TQB 3602 0.5mg to 7 mg on days 1, 8 and 15 of a 28-day cycle and two dose-limiting toxicities occurred at 7 mg, including diarrhea and grade 2 peripheral neuropathy. The maximum tolerated dose of TQB3602 was determined as 6.0mg. The terminal half-life was 23 to 152 hours after multiple dosing and the mean half-life was approximately 82 hours for 6mg TQB3602. The dose expansion cohorts recruited 29 RRMM patients receiving TQB3602/pomalidomide/dexamethasone regimen and two RRMM patients receiving TQB3602/lenalidomide/dexamethasone regimen. Among 14 response-evaluable patients in the dose expansion cohorts, eight RRMM (57%) achieved partial response or better (figure 1). The most common adverse events included thrombocytopenia, neutropenia, anemia, diarrhea, hypokalemia, fatigue and peripheral neuropathy. Adverse events of grade ≥3 included thrombocytopenia, neutropenia, anemia, elevated transaminase, diarrhea and pulmonary infection. Conclusions: TQB3602 is generally well tolerated. The combination therapy has shown preliminary efficacy in RRMM, and further clinical trials are in progress. (NCT04275583) Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Review on Acridines as Antiproliferative Agents.

Acridine rings can be found in molecules used in many different areas, including industry and medicine. Nowadays, acridines with anti-bacterial activity are of research interest due to decreasing bacterial resistance. Some acridine derivatives showed antimalarial or antiviral activity. Acridine derivatives were also investigated for anti-tumor activity due to the interaction with topoisomerase II and DNA base pairs. Considering these possible uses of acridine derivatives, this work overviewed all significant structure performances for the specific action of these compounds. The objective of this study is to review the activity of acridines as anti-proliferative agents. This review is designed as acridines acting as topoisomerase I and II inhibitors/ poison, Acridines on the G-quadraplux interaction, Acridines with metal complexes, Acridines with quinacrine scaffold, Acridines with sulphur moiety. Although introduced in the 19th century, acridine derivatives are still of scientific interest. In this review, acridine derivatives with various biological activities (antiparasitic, antiviral, anti-bacterial, and antiproliferative) and their structure-activity relationship analyses are presented. Although several mechanisms of their action are known, the only important are discussed here. It can be concluded that the dominant mechanisms are DNA intercalation and interaction with enzymes.

Highly selective and sensitive detection of mercury (II) and dopamine based on the efficient electrochemiluminescence of Ru(bpy)32+ with acridine orange as a coreactant

Developing highly specific, rapid, and cost-effective electrochemiluminescence (ECL) methods capable of detecting multiple analytes remains a compelling research goal but it is still a substantial challenge due to narrow choice of ECL systems. In this study, efficient ECL detections were achieved by using anodic Ru(bpy)32+-acridine orange (AO) ECL system. In present system, dimethylamino substituent on acridine ring acts as active sites for strong ECL generation, while heterocyclic nitrogen atom (–N–) contributes to specific complex formation with metal ion. Accordingly, this anodic ECL method was exploited for highly sensitive detection of both mercury (II) (Hg2+) and dopamine (DA), with detection limits as low as 0.36 nM (linear range 0.01–50 μM) and 1.0 nM (linear range 0.01–10 μM), respectively. The mechanism of Hg2+ detection was supported by density functional theory (DFT) calculations. Notably, the ECL method exhibit superior selectivity over numerous competing interfering agents. Moreover, the method achieved the detection of both targets in practical media with excellent recoveries (96.0–103.8%). Importantly, the method demonstrates potential advantages in terms of selectivity, sensitivity, rapidity, simplicity, and low cost. This work realizes a successful attempt to further expand the analytical applications of ECL systems and may initiate new thoughts in utilizing acridines in diverse ECL-based sensing and imaging applications.

Synthesis of novel 1,2,3-triazole based acridine and benzothiazole scaffold N-glycosides with anti-proliferative activity, docking studies, and comparative computational studies

In this investigation, the cycloaddition reaction of azide-alkyne derivatives 1a,b with glucopyranose azide 2a,b was catalyzed via Cu(I) to afford the corresponding acetylated 1,2,3-triazole N-glycoside derivatives 3a and 3b; respectively. The observed 1,2,3-triazole N-glycoside derivatives were examined via spectral analysis such as FT-IR,1HNMR, and mass spectrum. The investigated N-glycoside derivatives were exhibited antitumor activity against HCT-116, A549, HepG2, and MCF-7 tumor cells. The N-glycoside derivatives were docked against PDBID:5h38 and PDBID:4hdq with energy affinity rang (-8.87,-7.65 kcal/mol) and bond distance 2.69Å-2.91Å and attached with several hydrogen-bonding interactions inside the pocket of protein which confirmed the higher activity of benzo[d]thiazole and acridine rings attached with 1,2,3-triazole N-glycoside moiety. Furthermore, the theoretical studies of 1,2,3-triazole N-glycosides 3a and 3b utilized DFT/B3LYP/6–31G(d) basis set were investigated through bond length Å, and bond angle degrees, dihedral angle, geometrical parameters, FMO, surface contour which confirmed the stability of benzothiazole and acridine rinds in their energies and physical parameters.

Calf Thymus DNA Exposed to Quinacrine at Physiological Temperatures and pH Acquires Immunogenicity: A Threat for Long Term Quinacrine Therapy.

Quinacrine is an Acridine derivative with two potentially reactive groups; a diamino butyl side chain and an Acridine ring both capable of interacting with DNA but in different ways. This is an antimalarial drug approved by FDA for long term clinical trials and for the treatment of other diseases as well. The study evaluates the physicochemical interactions of quinacrine with DNA (calf thymus DNA) through characterizations of quinacrine DNA adduct (Q-DNA) by various techniques. It was observed that quinacrine induces stability in the structure of DNA, as the onset of melting was found to be increased by 6°C in the melting temperature profile of Q-DNA supported by other data obtained during study, deviation from the native structure of DNA was analyzed by FTIR that showed specific shifts in the region of 1707-1400cm-1.The study also probed the antigenicity of Q-DNA compared to its non antigenic native counterpart (N-DNA), by using both as antigens in female New Zealand White rabbits. Q-DNA was found to be antigenic with antibody titer > 1:6400. IgG was isolated and characterized to check for binding specificity. These antibodies were found to be promiscuous capable of cross reacting with other cellular molecules. Analysis of the data obtained suggested that intracellular accumulation of quinacrine and its ability to cross nucleus may allow the drug to interact with DNA. This may bring about significant structural perturbations in the macromolecule triggering an immunogenic response at the site where anti Q-DNA antibody and Q-DNA complex accumulates.

Thermochemiluminescence‐Based Sensitive Probes: Synthesis and Photophysical Characterization of Acridine‐Containing 1,2‐Dioxetanes Focusing on Fluorophore Push‐Pull Effects

AbstractN‐substituted acridine‐containing 1,2‐dioxetanes have been recently proposed as thermochemiluminescence (TCL) universal labels for bioanalytical applications. The TCL properties of these compounds markedly depend on the nature of substituents of the acridine ring. In the attempt to obtain new TCL probes with improved properties and stability, the push‐pull approach was adopted, in which both electron withdrawing and electron donating groups are present in the acridine moiety. The results have been useful to better understand the role of the different decorations at the acridine fluorophore in modulating the photophysical properties and the activation parameters of 1,2‐dioxetane labels. Moreover, the great versatility and innovation of these molecules make them extremely attractive for bioanalytical applications, in particular as labels for immune‐ and gene‐probe assays.

Acridine–O6-benzylguanine hybrids: Synthesis, DNA binding, MGMT inhibition and antiproliferative activity

O6-Methylguanine-DNA-methyltransferase (MGMT) is a key DNA repair enzyme involved in chemoresistance to DNA-alkylating anti-cancer drugs such as Temozolomide (TMZ) through direct repair of drug-induced O6-methylguanine residues in DNA. MGMT substrate analogues, such as O6-benzylguanine (BG), efficiently inactivate MGMT in vitro and in cells; however, these drugs failed to reach the clinic due to adverse side effects. Here, we designed hybrid drugs combining a BG residue covalently linked to a DNA-interacting moiety (6-chloro-2-methoxy-9-aminoacridine). Specifically, two series of hybrids, encompassing three compounds each, were obtained by varying the position of the attachment point of BG (N9 of guanine vs. the benzyl group) and the length and nature of the linker. UV/vis absorption and fluorescence data indicate that all six hybrids adopt an intramolecularly stacked conformation in aqueous solutions in a wide range of temperatures. All hybrids interact with double-stranded DNA, as clearly evidenced by spectrophotometric titrations, without intercalation of the acridine ring and do not induce thermal stabilization of the duplex. All hybrids, as well as the reference DNA intercalator (6-chloro-2-methoxy-9-aminoacridine 8), irreversibly inhibit MGMT in vitro with variable efficiency, comparable to that of BG. In a multidrug-resistant glioblastoma cell line T98G, benzyl-linked hybrids 7a–c and the N9-linked hybrid 19b are moderately cytotoxic (GI50 ≥ 15 μM after 96 h), while N9-linked hybrids 19a and 19c are strongly cytotoxic (GI50 = 1–2 μM), similarly to acridine 8 (GI50 = 0.6 μM). Among all compounds, hybrids 19a and 19c, similarly to BG, display synergic cytotoxic effect upon co-treatment with subtoxic doses of TMZ, with combination index (CI) values as low as 0.2–0.3. In agreement with in vitro results, compound 19a inactivates cellular MGMT but, unlike BG, does not induce significant levels of DNA damage, either alone or in combination with TMZ, as indicated by the results of γH2AX immunostaining experiments. Instead, and unlike BG, compound 19a alone induces significant apoptosis of T98G cells, which is not further increased in a combination with TMZ. These results indicate that molecular mechanisms underlying the cytotoxicity of 19a and its combination with TMZ are distinct from that of BG. The strongly synergic properties of this combination represent an interesting therapeutic opportunity in treating TMZ-resistant cancers.

Synthesis and biological evaluation of phenothiazine derivative-containing hydroxamic acids as potent class II histone deacetylase inhibitors.

The pathogenesis of Alzheimer's disease (AD) has been associated with dysregulation of histone deacetylases (HDACs). Previously, acridine-based HDAC inhibitors have shown potential in ameliorating HDAC activity and enhancing neurite outgrowth. In this study, the acridine ring was modified using various phenothiazine derivatives. Several resulting compounds exhibited potent enzyme-inhibiting activity towards class II HDACs when compared to the clinically approved HDAC inhibitor SAHA. Compound 4f demonstrated the highest class II HDAC inhibition (IC50=4.6-600nM), as well as promotion of neurite outgrowth. Importantly, compound 4f displayed no cytotoxicity against neuron cells. Compound 4f was further evaluated for cellular effects. Altogether, these findings show a potential strategy in HDAC inhibition for treatment of the neurological disease.

Acridine‐1,8‐diones: Synthesis and Biological Applications

AbstractThe unpretentious features of acridine‐1,8‐dionesviz. presence of N‐heteroatom, electronic behavior, acridine ring skeleton and wide possibilities of diversified substitution, bichromophoric structure and interaction ability with various proteins, make them an interesting scaffold of heterocyclic, medicinal and industrial chemistry. A tremendous development in the field of acridinediones in terms of synthetic strategies, bioactivity, industrial and other applicability has been explored in past four decades. In this perspective, an overview has been given on the state‐of‐art discoveries for the synthesis and biological applications of acridine‐1,8‐diones from 1980 to 2020. The study highlighted the history, chemistry and properties of these derivatives and provided deep insights into the synthetic protocols using various catalysts and techniques like nano‐catalyst, ionic‐liquids, microwave, ultrasound etc. under varied conditions along with biological activity against many lethal diseases. Finally, the respective prospects and limitations to these systems have been addressed. Furthermore, attempts have been done to bring many outstanding researches together and express the significance of acridine‐1,8‐diones through several aspects. We hope that the article shall deliver an impetus to explore further the synthetic values and mechanistic puzzles of acridinedione moiety and to design more promising hybrid multi‐targeted drugs and other industrial composites for the goodness of humanity

Crystal structure and Hirshfeld surface analysis of ethyl 2-[9-(2-hy-droxy-phen-yl)-3,3,6,6-tetra-methyl-1,8-dioxo-2,3,4,4a,5,6,7,8a,9,9a,10,10a-dodeca-hydro-acridin-10-yl]acetate.

In the title compound, C27H33NO5, a 3,3,6,6-tetra-methyl-tetra-hydro-acridine-1,8-dione ring system carries an ethyl acetate substituent on the acridine N atom and an o-hy-droxy-phenyl ring on the central methine C atom of the di-hydro-pyridine ring. The benzene ring is inclined to the acridine ring system at an angle of 80.45 (7)° and this conformation is stabilized by an intra-molecular O-H⋯O hydrogen bond between the hy-droxy substituent on the benzene ring and one of the carbonyl groups of the acridinedione unit. The ester C=O oxygen atom is disordered over major and minor orientations in a 0.777 (9):0.223 (9) ratio and the terminal -CH3 unit of the ethyl side chain is disordered over two sets of sites in a 0.725 (5): 0.275 (5) ratio. In the crystal, C-H⋯O hydrogen bonds combine to link the mol-ecules into a three-dimensional network. van der Waals H⋯H contacts contribute the most to the Hirshfeld surface (66.9%) followed by O⋯H/H⋯O (22.1%) contacts associated with weak hydrogen bonds.

In vitro anti-plasmodial activity of new synthetic derivatives of 1-(heteroaryl)-2- ((5-nitroheteroaryl)methylene) hydrazine

Objective: To evaluate new compounds synthesized by integrating quinoline, quinazoline, and acridine rings with the active moiety of (5-nitroheteroaryl) methylene hydrazine.Methods: A new series of compounds (1a, 1b, 2a, 2b, 3a, and 3b) were synthesized and evaluated for cytotoxicity against COS-7 cells using the MTT assay. In vitro anti-plasmodial activity of the compounds was measured against CQ-sensitive (3D7) and CQ-resistant (K1) Plasmodium (P.) falciparum strains. β-hematin assay was performed to assess the inhibitory effects of β-hematin formation for new compounds.Results: The synthetic compounds had anti-plasmodial activity against blood-stage of 3D7 [IC50=(0.328-5.483) μM] and K1 [IC50=(0.622-7.746) μM] strains of P. falciparum, with no cytotoxicity against COS-7 cells in effective doses. Compounds 1a, 1b, and 2b were the most effective derivatives against P. falciparum 3D7 and K1 strains. Based on the β-hematin assay, the inhibition of β-hematin formation is the main mechanism of the inhibitory effect of these compounds.Conclusions: The synthetic compounds could inhibit the erythrocytic stages of CQ-sensitive and resistant P. falciparum strains without toxicity towards mammalian cells. Compounds 1b, 2a, and 2b had comparable anti-plasmodial activity against both CQ-sensitive (3D7) and resistant (K1) P. falciparum strains. These compounds may be promising lead structures for the development of new anti-malarial drugs.

Zn(II) complexes of substituted oxyacridinate ligands. Synthesis, structure and properties

A number of new zinc complexes with 1,3-di‑tert‑butyl‑7-methylacridin-4-olate or 1,3-di‑tert‑butyl‑7-bromoacridin-4-olate ligands Zn(AcrMe)2, Zn(AcrMe)2(DMSO), Zn(AcrMe)2(Py)2, [Zn(Et)(AcrMe)]2, Zn(AcrBr)2, Zn(AcrBr)2(DMSO) and [Zn(Et)(AcrBr)]2 were synthesized by the reaction of respective acridinol with Et2Zn and structurally characterized. All compounds exhibited photoluminescence in the form of a single band in the 600 - 700 nm region. Compounds Zn(AcrMe)2 and [Zn(Et)(AcrMe)]2 displayed also weak electroluminescent properties. It is found that introduction of both alkyl or bromine substituents into acridine rings cause the hypsochromic shift of emission band. The resistance of organozinc complexes to strong ionizing radiation was studied using the example of [Zn(Et)(AcrMe)]2. X-ray diffraction study showed that the molecular structure of the complex did not change after strong neutron-gamma irradiation for 45 h.

An overview of pharmacological activities of acridine derivatives

The derivatives of acridine can be served as a lead molecule of an antibacterial, anti-viral antiprotozoal, anti-viral, antitubercular, anti-fungal, anti-malarial and anti-cancer agents. Even though the usage of acridine becomes limited due to its side effects, so many potent and safe compounds can be derived through molecular modification in the acridine ring. Since the resistance of pathogens and tumour cells has become more common nowadays, it necessitates the search of new drug candidates. Since the treatment and management of Alzheimer's disease is such a complicated and proper drug regimen is not designed so far, The cholinesterase activity of acridines can be used to derive novel compounds from treating Alzheimer's disease. The mosquito larvicidal activity of acridines is considered as an advantage as vector control to reduce the spreading rate of malaria. Unfortunately, the versatility of the acridine molecule is not entirely explored still. If new approaches may overcome the drawbacks of the acridines such as resistance of pathogens and tumour cells in synthesis and formulation acridine analogues will become a useful drug candidate for the treatment of diseases mentioned above. So this article aims to seek the attention of researchers in the acridine to utilise it’s a wide range of biological activities in the development of novel drug molecules for the various diseases in the future.

1.42-Fold Enhancement of Blue OLED Device Performance by Simply Changing Alkyl Groups on the Acridine Ring

Summary Developing high-efficiency blue thermally activated delayed fluorescence (TADF) emitters is still a formidable challenge. Here, we report five blue TADF emitters designed by simply changing the frequently used methyl group (C1) to a longer one gradually to subtly adjust the energy levels. DAc-C1–DAc-C5 are developed by using diphenylsulfone (DPS) as the acceptor and acridine with different-length alkyl chains on C(9) as the donor groups. These five compounds have high photoluminescence quantum yields (PLQYs) (75%–84%) with blue emission. The DAc-C2-based OLED device exhibits the maximum external quantum efficiency (EQE) of up to 24.1% with CIE (0.15, 0.19), which is 1.42 times higher than that of state-of-the-art TADF OLEDs based on DAc-C1 (EQE: 17.0%) under the same conditions, confirming the power of the molecular design strategy. Furthermore, the crystal analyses partially explain the influence of the alkyl chain on the device property, demonstrating a new approach for achieving TADF luminogens with high performance.

Effect of a Pendant Acceptor on Thermally Activated Delayed Fluorescence Properties of Conjugated Polymers with Backbone-Donor/Pendant-Acceptor Architecture.

Three sets of conjugated polymers with backbone-donor/pendant-acceptor architectures, named PCzA3PyB, PCzAB2Py, and PCzAB3Py, are designed and synthesized. The three isomeric benzoylpyridine-based pendant acceptor groups are 6-benzoylpyridin-3-yl (3PyB), 4-((pyridin-2-yl)carbonyl)phenyl (B2Py) and 4-((pyridin-3-yl)carbonyl)phenyl (B3Py), whereas the identical backbone consists of 3,6-carbazolyl and 2,7-acridinyl rings. One acridine ring and each acceptor group constitute a definite thermally activated delayed fluorescence (TADF) unit, incorporated into the main chain of the polymers through the 2,7-position of the acridine ring with the varied content. All of the polymers display legible TADF features with a short microsecond-scale delayed lifetime (0.56-1.62 μs) and a small singlet/triplet energy gap (0.10-0.19 eV). Progressively redshifted emissions are observed in the order PCzAB3Py, PCzA3PyB, and PCzAB2Py owing to the different substitution patterns of the pyridyl group. Photoluminescence quantum yields can be improved by regulating the molar content of the TADF unit in the range 0.5-50 %. The non-doped organic light-emitting devices (OLEDs) fabricated by solution-processing technology emit yellow-green to orange light. The polymers with 5 mol % of the TADF unit exhibit excellent comprehensive electroluminescence performance, in which PCzAB2Py5 achieves a maximum external quantum efficiency (EQE) of 11.9 %, low turn-on voltage of 3.0 V, yellow emission with a wavelength of 573 nm and slow roll-off with EQE of 11.6 % at a luminance of 1000 cd m-2 and driving voltage of 5.5 V.