Synthesis and antimicrobial activities of novel quinazolin-4(3H)-one derivatives containing a 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moiety

A series of novel quinazolin-4(3H)-one derivatives (6a–6y) containing a 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moiety were designed and synthesized, and their structures were fully characterized by ¹H NMR, ¹³C NMR, HRMS and IR spectra. Among them, the structure of compound 6u was unambiguously confirmed via single crystal X-ray diffraction analysis. The obtained bioassay results showed that compounds 6h, 6k, 6l and 6y had the EC₅₀ (half-maximal effective concentration) values of 34.8, 28.2, 41.5 and 42.5 μg/mL against the phytopathogenic bacterium Xanthomonas oryzae pv. oryzae (Xoo), respectively, which were significantly better than commercial bactericide Bismerthiazol (EC₅₀ = 95.8 μg/mL). Additionally, compounds 6a and 6b exhibited the strong inhibition activity against the pathogen Xanthomonas axonopodis pv. citri (Xac).     

Fused bis[2-(2′-hydroxyphenyl)benzoxazole] derivatives for improved fluoride sensing: The impact of regiochemistry and competitive hydrogen bonding

Development of fluorescent chemical sensors for fluoride is important due to increased use of fluoride in environment. A fused bis[2-(2′-hydroxyphenyl)benzoxazole] 5, which is capable of giving ESIPT emission, is found to be a useful fluorescent sensor for fluoride detection. Upon binding to fluoride, bis(HBO) 5 shows a large spectral shift in both fluorescence (from ～490 nm to ～440 nm) and absorption (from 353 nm to 392 nm). In comparison with the isomeric 4, bis(HBO) 5 dramatically improves the sensitivity in fluoride binding (by an order of magnitude), revealing a large impact of regiochemistry on the sensor performance. ¹H NMR has been used to study the fluoride binding, and to correlate the intramolecular hydrogen bonding with the fluoride response. Sensitivity of 5 towards fluoride is as low as 10^?5 M. Bis(HBO) 5 also showed excellent selectivity towards fluoride while being silent to other anions (Cl^?, Br^?, HS^? and PO₄^3?), thus making 5 a potentially useful probe.     

Functionalized N-heterocyclic carbene iridium complexes: Synthesis,structure and addition polymerization of norbornene

Picolyl, pyridine, and methyl functionalized N-heterocyclic carbene iridium complexes [Cp¹Ir(C^N)Cl]Cl (4, C^N = 3-Methyl-1-picolyimidazol-2-ylidene), [Cp¹Ir(C^N)Cl][Cp¹IrCl₃] (5), [Cp¹Ir(C-N)Cl]Cl (6, C-N = 3-Methyl-1-pyridylimidazol-2-ylidene) and [Cp¹Ir(L)Cl₂] (7, L = 1,3-dimethylimidazol-2-ylidene) have been synthesized by transmetallation from Ag(I) carbene species, and characterized by ¹H NMR, ¹³C NMR spectra and elemental analyses. The molecular structures of 5–7 have been confirmed by X-ray single-crystal analyses. The iridium carbene complexes 4 and 6 show moderate catalytic activities (3.03 × 10⁵ g PNB (mol Ir)^?1 h^?1 and 1.70 × 10⁶ g PNB (mol Ir)^?1 h^?1) for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as co-catalyst. The produced polynorbornene have been characterized by IR, ¹H NMR and ¹³C NMR spectra, showing it follows the vinyl-addition-type of polymerization.     

Trichothiazole A,a dichlorinated polyketide containing an embedded thiazole isolated from Trichodesmium blooms

Mass spectrometry-guided isolation of the lipophilic extract of Trichodesmium bloom material led to the isolation and structure characterization of a new thiazole-containing di-chlorinated polyketide (1). The structure of 1 was deduced using 1D and 2D NMR analysis, high-resolution mass spectrometry analysis and complementary spectroscopic procedures. Trichothiazole A possesses interesting structural features, such as a terminal alkyne, two vinyl chlorides and a 2,4-disubstituted thiazole. Trichothiazole A showed moderate cytotoxicity to Neuro-2 A cells (EC₅₀: 13.3 ± 1.1 μM).     

Design,synthesis, and fungicidal activity of novel 1,3,4-oxadiazole derivatives

Employing the intermediate derivatization method (IDM), a series of 1,3,4-oxadiazole derivatives containing arylpyrazoloxyl moiety were designed and synthesized. In vitro bioassays showed that these compounds have moderate to significant fungicidal activity against rice sheath blight and sorghum anthracnose. Furthermore, compound 20 is a promising fungicide for further development.     

Toward a highly sensitive and selective indole-rhodamine-based light-up probe for Hg2+ and its application in living cells

We herein designed and synthesized a light-up fluorescent probe L1 for Hg²⁺ species, which is based on indole derivative and Rhodamine fluorophore. The new probe can show a linear response to Hg²⁺ with high sensitivity and selectivity. As the Hg²⁺ concentration changed from 0 to 450 μM, the fluorescence intensity of L1 at 575 nm changed from 50 to 6181 (～120-fold). The detection limit of the probe was 5.0 × 10^?8 M. Besides, we have successfully applied L1 to monitor Hg²⁺ species in living MCF-7 cells by way of fluorescence imaging.     

Synthesis,characterization and biological evaluation of purine nucleoside analogues

We present a convenient route for the synthesis of C6-amino-C5′-N-cyclopropyl carboxamido-C2-alkynylated purine nucleoside analogues 11a–g via Sonogashira coupling reaction. The nine step synthesis is easy to perform, employing commercially available reagents. Compound 9 is used as key intermediate for the synthesis of analogues 11a–g. Synthetic intermediates and final products are appropriately characterized by IR, ¹H NMR, ¹³C NMR and Mass. The modified nucleoside analogues 11a–g is evaluated for in vitro anticancer activity against MDA-MB-231 and Caco-2 cell lines. Screening data reveals that compounds 11b and 11e displayed potent IC₅₀ value of 7.9, 6.8 µg/mL respectively against MDA-MB-231 and of 7.5, 8.3 µg/mL respectively against Caco-2 than the standard drug doxorubicin, thus establishing the potential anti-cancer properties of these newer derivatives.     

Highly sensitive fluorescent sensor targeting CuCl2 based on thiophene attached anthracene compound (TA)

A novel thiophene attached anthracene (TA) based fluorescent compound was designed and synthesized. The TA showed a high quantum yield (Qy = 0.34) in regard to fluorescence. We applied this TA compound to detect specific metal compound and found that it could identify CuCl₂ from other metals through dramatic fluorescence change at λ_max = 460 nm. It showed strong quenching fluorescence property with CuCl₂ while with other metal compounds it exhibited strong blue fluorescence emission. UV/Vis absorption spectroscopy clearly demonstrated that the quenching property of TA at λ_max = 460 nm was due to overlapping of the fluorescence peak of TA at λ_max = 460 nm and the absorption band of CuCl₂ (from 190 nm to 525 nm). Binding constant (K′), which was 0.0895 mM^?2, indicated a complexation ratio between TA and CuCl₂ as 1:2 and this interaction induced quenching property.     

A sensitive tetraphenylethene-based fluorescent probe for Zn2+ ion involving ESIPT and CHEF processes

A new tetraphenylethene-based fluorescent probe 2-(quinolin-8-yliminomethyl)-4-triphenylvinyl-phenol (HL) for detecting Zn²⁺ ion through the excited state intramolecular proton transfer (ESIPT) and chelation enhanced fluorescence (CHEF) processes has been designed and synthesized. The results show that HL emits relatively strong blue fluorescence at 460 nm without Zn²⁺ ion, however, probe HL displays highly pink fluorescent emission at 600 nm when adding Zn²⁺ ion. The fluorescent emission of HL appears an extremely large Stokes shift, which effectively reduces the interference of background signal. The limit of detection of HL for Zn²⁺ ion can reach to 9.0 × 10^–8 M.     

Switched enantioselectivity by solvent components and temperature in photocyclodimerization of 2-anthracenecarboxylate with 6~A,6~X-diguanidio-γ-cyclodextrins

A series of 6A,6X-diguanidio-g-cyclodextrins (CDs) were synthesized as chiral hosts for mediating the enantiodifferentiating[4+4] photocyclodimerization of 2-anthracenecarboxylic acid (AC). Variation of the temperature and the ammonia contents led to greatly enhanced head-to-head photodimers 3 and 4, companying by inversion of product chirality.     

Dinuclear Rh(I) complex with 2,7-bis(diphenylphosphino)-1,8-naphthyridine: Synthesis,structure, and dynamic property

Reaction of [RhCl(cod)]₂ with 2,7-bis(diphenylphosphino)-1,8-naphthyridine (dpnapy) and 2,6-xylyl isocyanide (XylNC) in the presence of NH₄PF₆ afforded the dirhodium(I) complex, [Rh₂(μ-dpnapy)₂(XylNC)₄](PF₆)₂ (5), and similar procedures using [MCl₂(cod)] (M = Pt, Pd) resulted in the formation of [Pt₂(μ-dpnapy)₂(XylNC)₄](PF₆)₄ (6) and [Pd₂Cl₂(μ-dpnapy)₂(XylNC)₂](PF₆)₂ (7). Complexes 5–7 were characterized by elemental analysis, IR, UV–Vis, ¹H and ³¹P{¹H} NMR, and ESI mass spectroscopic techniques, to involve a small and rigid d⁸ {M₂(μ-dpnapy)₂} metallomacrocycle. Complex 5 readily incorporated a silver(I) ion into the macrocycle to afford [Rh₂Ag(μ-dpnapy)₂(XylNC)₄](PF₆)₃ (8) which was characterized by X-ray crystallography. The Ag(I) ion is trapped by two trans N atoms of dpnapy ligands, resulting in an asymmetric Rh–Ag⋯Rh structure, determined as a disordered model in the crystal structure, and however, in a CH₂Cl₂ solution, a dynamic interconversion of the two Ag-trapped sites was observed with low-temperature NMR studies, which was further supported by DFT molecular orbital calculations. When an acetonitrile solution of complex 5 was treated over a droplet of mercury(0), the polymeric compound formulated as {[Rh(μ-dpnapy)(XylNC)₂](PF₆)}_n (9) was isolated as yellow single crystals, which were revealed by X-ray crystallography to consist of C₆ helical rods along c axis with a pitch of 33.5 Å (rise of unit = 5.6 Å) and a diameter of 20.64 Å.     

Synthesis and characterization of novel intramolecularly O,C,O-coordinated heteroleptic organostannylenes and their tungstenpentacarbonyl complexes

The syntheses are reported of the novel heteroleptic organostannylenes [2,6-(ROCH₂)₂C₆H₃]SnCl (1, R = Me; 2, R = t-Bu) and of their tungstenpentacarbonyl complexes [2,6-(ROCH₂)₂C₆H₃](X)SnW(CO)₅ (3, X = Cl, R = Me; 4, X = Cl, R = t-Bu; 5, X = H, R = Me). The compounds were characterized by means of elemental analyses, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopies, electrospray mass spectrometry and in case of 3 and 4 also by single crystal X-ray diffraction analysis. For the two latter compounds the substituents bound at the ether oxygen atom control the strength of intramolecular O → Sn coordination. Thus, the O–Sn distances amount to 2.391(5)/2.389(5) (3) and 2.464(3)/2.513(3) Å (4).     

Synthesis,Structure, Properties,and Application of a Carbazole‐Based Diaza[7]helicene in a Deep‐Blue‐Emitting OLED

A carbazole‐based diaza[7]helicene, 2,12‐dihexyl‐2,12‐diaza[7]helicene ( 1 ), was synthesized by a photochemical synthesis and its use as a deep‐blue dopant emitter in an organic light‐emitting diode (OLED) was examined. Compound 1 exhibited good solubility and excellent thermal stability with a high decomposition temperature (T_d=372.1 °C) and a high glass‐transition temperature (T_g, up to 203.0 °C). Single‐crystal structural analysis of the crystalline clathrate ( 1 )₂ ? cyclohexane along with a theoretical investigation revealed a non‐planar‐fused structure of compound 1 , which prevented the close‐packing of molecules in the solid state and kept the molecule in a good amorphous state, which allowed the optimization of the properties of the OLED. A device with a structure of ITO/NPB (50 nm)/CBP:5 % 1 (30 nm)/BCP (20 nm)/Mg:Ag (100 nm)/Ag (50 nm) showed saturated blue light with Commission Internationale de L’Eclairage (CIE) coordinates of (0.15, 0.10); the maximum luminance efficiency and brightness were 0.22 cd A^?1 (0.09 Lm W^?1) and 2365 cd m^?2, respectively. This new class of helicenes, based on carbazole frameworks, not only opens new possibilities for utilizing helicene derivatives in deep‐blue‐emitting OLEDs but may also have potential applications in many other fields, such as molecular recognition and organic nonlinear optical materials.     

Synthesis and red electroluminescence of a dimesityl-functionalized bistetracene

The single crystal analysis of the as-prepared 8,16-dimesityltetraceno[2,1,12,11-opqra]tetracene (DMTA) suggests that the parent bistetracene backbone is almost in a plane without any intermolecular p-stacking interaction. The fabricated devices based on DMTA as an emitter exhibit a maximum brightness of 632 cd/m² at 14.7 V with the CIE coordinate of (0.623, 0.349).     

Diterpenoids from the aerial parts of Leonurus macranthus

One cis clerodane-type (1) and three highly oxygenated labdane-type diterpenes (2-4) were isolated from the aerial parts of Leonurus macranthus. Compound 1 represents the first example of cis clerodane-type diterpene in the plants of Leonurus genus.     

Antiplasmodial Securinega alkaloids from Phyllanthus fraternus: Discovery of natural (+)-allonorsecurinine

The chemical investigation of the antimalarial plant Phyllanthus fraternus G. L. Webster (Phyllanthaceae) resulted in the discovery of the Securinega alkaloid (+)-allonorsecurinine (1), previously reported as a synthetic compound, together with the known ent-norsecurinine (2), nirurine (3), bubbialine (4), epibubbialine (5) and the lignan phyllanthin (6). The structure and absolute configuration of the new compound were elucidated on the basis of extensive spectroscopic analysis, optical rotation, and GIAO NMR shift calculation followed by CP3 analysis. The antiplasmodial activity of these compounds was evaluated against chloroquine-resistant (W2) and -sensitive (3D7) strains of Plasmodium falciparum. Among them, ent-norsecurinine (2) and (+)-allonorsecurinine (1) showed the strongest activity (IC₅₀: 1.14 ± 0.32 and 2.57 ± 0.53 µM) respectively, against W2 but one of the weakest against 3D7.     

Metal π complexes of benzene derivatives: Part 56. (η6-Fluoranthene)(tricarbonyl)chromium: isomerism and haptotropic equilibration

Reaction of fluoranthene with Cr(CO)₃Py₃/BF₃·OEt₂ at 25 °C affords a mixture of two isomeric complexes: traces of tricarbonyl(1-5,15-η⁶-fluoranthene)chromium (3) (coordination to benzene) and, as the major product, tricarbonyl(1-4,15,16-η⁶-fluoranthene)chromium (2) (coordination to naphthalene). The ratio 3:2 is less than 0.05 according to ¹H-NMR of crude product before crystallization. Complex 2 is thermodynamically less stable than 3: at 100 °C in decane or C₆D₆ for 8 h or at 90 °C in C₆F₆ for 100 h 2 rearranges irreversibly to 3 via an inter-ring haptotropic shift of the Cr(CO)₃ group from the naphthalene moiety to the benzene part of the fluoranthene ligand. NMR evidence for a degenerate reversible haptotropic shift within the naphthalene moiety is absent. The isomers 2 and 3 have been characterized by X-ray structural analysis.     

A fast,highly selective and sensitive dansyl-based fluorescent sensor for copper (II) ions and its imaging application in living cells

Since the copper ions (Cu²⁺) play a fatal role in many foundational physiological processes, it is important to develop a simple, highly sensitive and selective sensor for Cu²⁺ detection in living systems. Herein, an intramolecular charge transfer (ICT) and dansyl-based fluorescent chemosensor 1 was designed, synthesized and characterized for the sensitive and selective quantification of Cu²⁺. It exhibited remarkable fluorescence quenching upon addition of Cu²⁺ over other selected metal ions, attributed to the complex formation between 1 and Cu²⁺ with the association constant 6.7 × 10⁵ M^?1. The sensor 1 showed a fast and linear response towards Cu²⁺ in the concentration range from 0 to 12.5 × 10^?6 mol L^?1 with the detection limit of 2.5 × 10^?7 mol L^?1. This detection could be carried out in a wide pH range of 5.0–14. Furthermore, sensor 1 can be used for detecting Cu²⁺ in living cells.     

Synthesis,spectroscopic studies and structures of square-planar nickel(II) and copper(II) complexes derived from 2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol

Two new nickel(II) [Ni(L)₂] and copper(II) [Cu(L)₂] complexes have been synthesized with bidentate NO donor Schiff base ligand (2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol) (HL) and both complexes Ni(L)₂ and Cu(L)₂ have been characterized by elemental analyses, IR, UV–vis, ¹H, ¹³C NMR, mass spectroscopy and room temperature magnetic susceptibility measurement. The tautomeric equilibria (phenol-imine, O–H?N and keto-amine, O?H–N forms) have been systemetically studied by using UV–vis absorption spectra for the ligand HL. The UV–vis spectra of this ligand HL were recorded and commented in polar, non-polar, acidic and basic media. The crystal structures of these complexes have also been determined by using X-ray crystallographic techniques. The complexes Ni(L)₂ and Cu(L)₂ crystallize in the monoclinic space group P2₁/n and P2₁/c with unit cell parameters: a = 10.4552(3) Å and 12.1667(4) Å, b = 8.0121(3) Å and 10.4792(3) Å, c = 13.9625(4) Å and 129.6616(3)Å, V = 1155.22(6) Å³ and 1155.22(6) Å³, D_x = 1.493 and 1.476 g cm^?3 and Z = 2 and 2, respectively. The crystal structures were solved by direct methods and refined by full-matrix least squares to a find R = 0.0377 and 0.0336 of for 2340 and 2402 observed reflections, respectively.     

Spectral studies of Fe(III) complexes of dipodal tridentate chelating agents

The dipodal ligands (Im) and (BIm) as well as complexes [FeLCl₃] [L = Im (1) and BIm (2)] have been prepared and studied using spectroscopic techniques. The magnetic moment, IR, electronic (ligand field), FAB-mass and NMR spectral data indicate a hexa-coordinate geometry around high-spin state Fe³⁺ where the ligands coordinate as a tridentate [N,N,N] chelating agent. ⁵⁷Fe-Mössbauer spectral data confirmed the presence of a ligand asymmetry around Fe³⁺ in a high-spin state electronic configuration (t_2g³,e_g², S = 5/2) with nuclear transition Fe(±3/2 → ±1/2) exhibiting Kramer's double degeneracy. The molecular computations provided the optimum energy perspective plots for the molecular geometries giving the important structural data.