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The noncovalent chalcogen interaction between SO2/SO3 and diazines was studied through a dispersion-corrected DFT Kohn–Sham molecular orbital together with quantitative energy decomposition analyses. For this, supramolecular circular chains of up to 12 molecules were built with the aim of checking the capability of diazine molecules to detect SO2/SO3 compounds within the atmosphere. Trends in the interaction energies with the increasing number of molecules are mainly determined by the Pauli steric repulsion involved in these σ-hole/π-hole interactions. But more importantly, despite the assumed electrostatic nature of the involved interactions, the covalent component also plays a determinant role in its strength in the involved chalcogen bonds. Noticeably, π-hole interactions are supported by the charge transfer from diazines to SO2/SO3 molecules. Interaction energies in these supramolecular complexes are not only determined by the S···N bond lengths but attractive electrostatic and orbital interactions also determine the trends. These results should allow us to establish the fundamental characteristics of chalcogen bonding based on its strength and nature, which is of relevance for the capture of sulfur oxides. [ABSTRACT FROM AUTHOR]

An approach was developed for the synthesis of polyfunctionalized pyrimidines based on analogs of 1,2,4-triketones. Acetal-substituted β-diketones are involved in the condensation with amidines in the presence of an excess of (EtO)3B/Et3N in acetonitrile. The conditions of the acid hydrolysis of acetal-containing pyrimidines were found to depend on the nature of substituents in diazine. The use of 1,2,4-triketone in the condensation with amidine allows the synthesis of acetylpyrimidine in one step. [ABSTRACT FROM AUTHOR]

The article discusses the use of the inverse-electron-demand Diels-Alder (IEDDA) reaction as a synthetic tool for creating complex molecular structures. The authors focus on the use of bidentate Lewis acid catalysts to facilitate the IEDDA reaction between phthalazines and cyclooctynes. They found that the catalyst significantly increased the reaction rate and yield of the desired products. The authors also explored the scope of the reaction by testing different substituted phthalazines and cyclooctynes. The method presented in the article provides a convenient and efficient way to synthesize polycyclic aromatic hydrocarbons fused to eight-membered carbocycles. [Extracted from the article]

Electrochemical oxidation of o-tolidine has been assessed in a mixture (70/30) of buffer/acetonitrile and various pHs. The electrochemical results corroborate that the mechanism of electrooxidation of o-tolidine acidic, neutral, and alkaline solutions are different, and three pH zones with different oxidation mechanisms were obtained: in the first region, a reversible oxidation reaction under the E mechanism, in the second region, observing the two one-electron oxidation–reduction under the ECDispE mechanism, and observation of the evidence of the ECE mechanism in the third region. In the continuation, electrosynthesis of a new azo compound has been reported in the third region. This process involves the electrochemical oxidation of o-tolidine in an aqueous phosphate buffer (pH = 7.2) in a divided cell using a carbon anode. [ABSTRACT FROM AUTHOR]

The reactions of pyrazine, pyridazine, and pyrimidine with hydroxyl radicals are theoretically studied. The barrier heights obtained with different electronic structure methods indicate that the reactions can competitively proceed via either abstraction of a hydrogen atom by an OH radical or OH addition to carbon sites. However, the rate constants computed within the temperature range 200 to 1500 K suggest that tunneling play a role resulting in large branching ratios in favor of hydrogen abstraction channels at lower temperatures. [ABSTRACT FROM AUTHOR]

A series of N-substituted α,β-dehydroamino acids N-benzoylmethylamides was prepared starting from substituted 2-phenyl-4-benzylidene-5-oxazolones. The ketoamides were used to the synthesis of substituted 4-imidazolones in the presence of 1,1,1,3,3,3-hexamethyldisilazane as a dehydrating agent. The corresponding amido alcohol was obtained by reduction of (Z)-N-{3-oxo-3-[(2-oxo-2-phenylethyl)amino]-1-phenylprop-1-en-2-yl}benzamide by sodium borohydride, and diazine was obtained by its reaction with hydrazine. Antiradical and anticholinesterase properties of the synthesized compounds were studied. [ABSTRACT FROM AUTHOR]

A dynamic kinetic asymmetric transformation, involving the generation of four stereogenic centers with a well‐defined configuration, occurs in the cyclocondensation of diastereomeric mixtures of 2‐oxocyclohexanepropionic acid racemates 6 with (1S,2R)‐cis‐aminoindanol: two major tetracyclic lactams, 7 a and 7 b, that differ in the configuration of the four stereocenters on the decahydroquinoline moiety were obtained. From the above lactams, the removal of the chiral auxiliary, the introduction of a 2‐piperidone ring, and the closure of the diazine ring complete the first enantioselective total synthesis of the Myrioneuron alkaloid (−)‐schoberine B and its enantiomer (+)‐schoberine B. [ABSTRACT FROM AUTHOR]

MnFe2O4 spinel nanoparticles were synthesized by the sonochemical method (co-precipitation in an ultrasonic field). The Bragg diffraction peaks of the synthesized product agreed with the MnFe2O4 spinel reference model, and the average MnFe2O4 crystallite size, calculated using the Debye–Scherrer equation, was approx. 7 nm. The obtained MnFe2O4 spinel nanoparticles were used as potassium persulfate activators during the oxidative degradation of the safranin T diazine dye. The degradation degree of safranin T for the duration of the "advanced" oxidation "ultrasound/ MnFe2O4 / K2S2O8 " of 7200 s and a catalyst content of 0.1 g/L was equal to 98.3%, and the rate constant was 1.529×10–3 s–1. [ABSTRACT FROM AUTHOR]

Nitrogen‐heterocycle‐based covalent organic frameworks (COFs) are considered promising candidates for the overall photosynthesis of hydrogen peroxide (H2O2). However, the effects of the relative nitrogen locations remain obscured and photocatalytic performances of COFs need to be further improved. Herein, a collection of COFs functionalized by various diazines including pyridazine, pyrimidine, and pyrazine have been judiciously designed and synthesized for photogeneration of H2O2 without sacrificial agents. Compared with pyrimidine and pyrazine, pyridazine embedded in TpDz tends to stabilize endoperoxide intermediate species, leading toward the more efficient direct 2e‐ oxygen reduction reaction (ORR) pathway. Benefiting from the effective electron‐hole separation, low charge transfer resistance, and high‐efficiency ORR pathway, an excellent production rate of 7327 μmol g−1 h−1 and a solar‐to‐chemical conversion (SCC) value of 0.62 % has been achieved by TpDz, which ranks one of the best COF‐based photocatalysts. This work might shed fresh light on the rational design of functional COFs targeting photocatalysts in H2O2 production. [ABSTRACT FROM AUTHOR]

The functionalization of methylated azines and diazines has aroused the interest of chemists given the structural diversity that it affords. Hindered lithium dialkylamides have been used to deprotometallate these substrates chemoselectively. In contrast, it can be observed that, despite some promising work, lithium diethylamide has been used very little for this purpose. Our objective here is on the one hand to make an inventory of what reagents have been used to deprotometallate methylpyridines, ‐quinolines and ‐quinoxalines, and on the other hand to describe the results obtained by seeking to functionalize a series of substrates with lithium diethylamide (picolines, 2,4‐lutidine, methylquinolines and 2‐methylquinoxaline). Our efforts to take advantage of the use of an in‐situ trap (a zinc chloride chelate) in these reactions are also described. [ABSTRACT FROM AUTHOR]

Herein, we developed a photoinduced Minisci reaction on a large panel of diazines with good to excellent yields (28 examples, 44 % to 89 %). The reaction using 4CzIPN (1 mol %) as photoinitiator was carried out under white LED irradiation and required a slight excess of the acid reagent (1.2 equiv.). Cyclization reactions were then developed to access original N‐heterocycles building blocks for drug discovery programs. An extension of the reaction to continuous flow was also reported. Finally, the mechanism of the transformation was studied suggesting a plausible radical chain mechanism. [ABSTRACT FROM AUTHOR]

Signal Amplification by Reversible Exchange (SABRE) is an inexpensive and simple hyperpolarization technique that is capable of boosting nuclear magnetic resonance sensitivity by several orders of magnitude. It utilizes the reversible binding of para-hydrogen, as hydride ligands, and a substrate of interest to a metal catalyst to allow for polarization transfer from para-hydrogen into substrate nuclear spins. While the resulting nuclear spin populations can be dramatically larger than those normally created, their lifetime sets a strict upper limit on the experimental timeframe. Consequently, short nuclear spin lifetimes are a challenge for hyperpolarized metabolic imaging. In this report, we demonstrate how both hyperpolarization and long nuclear spin lifetime can be simultaneously achieved in nitrogen-15 containing derivatives of pyridazine and phthalazine by SABRE. These substrates were chosen to reflect two distinct classes of 15N2-coupled species that differ according to their chemical symmetry and thereby achieve different nuclear spin lifetimes. The pyridazine derivative proves to exhibit a signal lifetime of ∼2.5 min and can be produced with a signal enhancement of ∼2700. In contrast, while the phthalazine derivative yields a superior 15 000-fold 15N signal enhancement at 11.7 T, it has a much shorter signal lifetime. [ABSTRACT FROM AUTHOR]

A new method for regioselective zincations of challenging N‐heterocyclic substrates such as pyrimidines and pyridazine was reported using bimetallic bases TMPZnX⋅LiX (TMP=2,2,6,6‐tetramethylpiperidyl; X=Cl, Br). Reactions occurred under mild conditions (25–70 °C, using 1.75 equivalents of base without additives), furnishing 2‐zincated pyrimidines and 3‐zincated pyridazine, which were then trapped with a variety of electrophiles. Contrasting with other s‐block metalating systems, which lack selectivity in their reactions even when operating at low temperatures, these mixed Li/Zn bases enabled unprecedented regioselectivities that cannot be replicated by either LiTMP nor Zn(TMP)2 on their own. Spectroscopic and structural interrogations of organometallic intermediates involved in these reactions have shed light on the complex constitution of reaction mixtures and the origins of their special reactivities. [ABSTRACT FROM AUTHOR]

Crystal structures of two salts of (E)-2-(3,4-dimethoxystyryl)pyrimidinium (HDmsPy+) are studied: (HDmsPy)Cl·H2O and (HDmsPy)Cl·0.5С6H4(OH)2. (E)-2-(3,4-dimethoxystyryl)pyrimidinium chloride is photoinert. Upon UV irradiation, the (E)-2-(3,4-dimethoxystyryl)pyrimidinium cocrystal with catechol as well as pure (E)-2-(3,4-dimethoxystyryl)pyrimidine (DmsPy) are involved in the [2+2]-photocycloaddition reaction with crystal destruction. Structures of solid phase reaction products and a similar photocycloaddition reaction in the solution are analyzed by 1H NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Copper‐dppf catalyzed reductive coupling of diazo compounds through terminal nitrogen is reported. However, copper catalysts are known to produce carbene from diazo compounds; the reaction conditions played an important role in the formation of diazine over carbene generation. Several control experiments have been conducted to understand the reaction mechanism and found that the formation of a copper–Mg heterobimetallic complex would be responsible for the observed reactivity pattern. The reaction produced diazine as a reductive coupling product along with biphenyl as a by‐product. All the synthesized diazines have been characterized fully by using analytical and spectroscopic techniques. [ABSTRACT FROM AUTHOR]

α-Boryl-α-hydrazinoacetic acid is a highly functionalized boron-containing building block that can be easily accessed from readily available α-borylacetaldehyde. The hydrazine motif can be converted into a variety of α-borylated azoles and diazines in a straightforward protocol. Furthermore, the carboxy group can be derivatized to afford novel organoboron compounds that should find applications in various cross-coupling transformations. [ABSTRACT FROM AUTHOR]

In this contribution, a series of seven new push–pull systems has been designed by combining a protonable diazine heterocycle (pyrimidine/pyrazine) with a deprotonable phenol unit through various π-conjugated linkers (phenylene, thienylene, thienylenevinylene, and phenylenevinylene). The (de)protonation in solution resulted in a systematic bathochromic shift both in the absorption and emission maxima compared to the neutral forms. Extensive Density Functional Theory (DFT) and its Time Dependent counterpart (TD-DFT) calculations were performed to rationalize this behavior and understand the impact of (de)protonation on the different optical transitions. These computations showed that (de)protonation affects both the energy and the nature of the vertical transitions, with a significant increase in the Intramolecular Charge Transfer (ICT) character of the (de)excitations. Some of the compounds remained moderately luminescent after (de)protonation, giving a mixture of complementary emitting species that were used to obtain white light emission. [ABSTRACT FROM AUTHOR]

In this paper, we designed and synthesized six new wide band gap donor-acceptor (D-A) copolymers, PZ2 - PZ7 , with diazine isomers (pyrazine, pyridazine, pyrimidine) as the A unit and alkylthiophene- or alkylthiothienyl-substituted BDT as the D unit. The effect of diazine isomeric A units and side-chain substituents on molecular structure, optoelectronic properties and photovoltaic performances of the resulting D-A copolymers were investigated in details. Six low-cost polymers were easily obtained by minimal reaction steps and cheap raw materials. All the polymers exhibited wide band gaps (WBGs) (>1.9 eV) and deep-lying HOMO energy levels (<−5.48 eV), which is convenient for paring with low band gap nonfullerene acceptors (NFAs). Theoretical simulation calculation indicates that diazine isomeric A unit has great impact on the planarity of polymer backbone. Bulk heterojunction polymer solar cells (PSCs) were fabricated with these polymers as donor materials and representative NFAs (Y6 and ITIC) as acceptor materials. After optimization, pyrazine-based polymers PZ2 and PZ3 exhibited higher PCEs than those of pyridazine- and pyrimidine-based ones (PZ4 - PZ7) regardless of the acceptors. Finally, the PZ2 :Y6-based PSC achieved the highest power conversion efficiency (PCE) up to 11.21 %, which could be attributed to more balanced carrier mobility, increased charge dissociation probability, reduced charge recombination, and superior active layer morphology. This work suggests that diazine-based WBG polymers, especially for pyrazine, would become as very promising donor candidates for constructing low-cost and efficient NFA-based PSCs. Six donor-acceptor (D-A) copolymers, PZ2-PZ7 , with simple diazine isomers (pyrazine, pyridazine, pyrimidine) as the A unit and alkylthiophene- or alkylthiothienyl-substituted BDT as the D unit were developed to construct low-cost and efficient polymer donors. Results demonstrated that pyrazine-based polymers PZ2 and PZ3 exhibited higher PCEs than those of pyridazine- and pyrimidine-based ones (PZ4-PZ7) regardless of the acceptors. Especially, the PZ2:Y6 -based PSC achieved the highest PCE up to 11.21 %, which is mainly attributed to the remarkably increased J SC and FF. [Display omitted] • Six D-A copolymers, PZ2 - PZ7 , with diazine isomers as the A unit were designed and synthesized. • These low-cost polymers were easily obtained by minimal reaction steps and cheap raw materials. • PSCs based on PZ2 with pyrazine as the A unit exhibited an obviously enhanced PCE of 11.21 %. [ABSTRACT FROM AUTHOR]

Crystal structures of three isomeric styryldiazine derivatives (E)-2-(3,4-dimetoxystryl)pyrazine, (E)-2-(3,4-dimetoxystryl)pyrimidine, and (E)-4-(3,4-dimetoxystryl)pyrimidine with different positions of nitrogen atoms are studied. These compounds can be used as potential initial compounds for biologically active (antibacterial or antitumor) agents, pesticides, fungicides, dyes, analytical reagents. Even though these molecules have similar chemical structures and geometric parameters in the crystal, the crystal packing motifs of these three compounds differ significantly. The conducted PBE0/6-31G(d,p) quantum chemical calculations show that these molecules may have several conformers with close energies, including those observed in the crystal, and that these forms may transform into each other through barriers not exceeding 43.5 kJ/mol. The highest density at 120 K and the highest energy of crystal lattice calculated by the UNI force field are observed for the pyrimidine derivative (E)-2-(3,4-dimetoxystryl)pyrimidine (6). This is the only structure that exhibits photocyclization in solid state due to the fact that its crystal contains centrosymmetric dimers with a distance between the atoms of olefin fragments equal to ≈ 3.9 Å. [ABSTRACT FROM AUTHOR]

The bonding energies of proton-bound homodimers BH+B were measured by ion mobility equilibrium studies and calculated at the DFT B3LYP/6-311++G** level, for a series of nitrogen heterocyclic molecules (B) with electron-withdrawing in-ring N and on-ring F substituents. The binding energies (ΔH° dissoc) of the proton-bound dimers (BH+B) vary significantly, from 29.7 to 18.1 kcal/mol, decreasing linearly with decreasing the proton affinity of the monomer (B). This trend differs significantly from the constant binding energies of most homodimers of other organic nitrogen and oxygen bases. The experimentally measured ΔH° dissoc for (1,3-diazine)2H+, i.e., (pyrimidine)2H+ and (3-F-pyridine)2H+ are 22.7 and 23.0 kcal/mol, respectively. The measured ΔH° dissoc for the pyrimidine .+(3-F-pyridine) radical cation dimer (19.2 kcal/mol) is signifcantly lower than that of the proton-bound homodimers of pyrimidine and 3-F-pyridine, reflecting the stronger interaction in the ionic H-bond of the protonated dimers. The calculated binding energies for (1,2-diazine)2H+, (pyridine)2H+, (2-F-pyridine)2H+, (3-F-pyridine)2H+, (2,6-di- F-pyridine)2H+, (4-F-pyridine)2H+, (1,3-diazine)2H+, (1,4-diazine)2H+, (1,3,5-triazine)2H+, and (pentafluoropyridine)2H+ are 29.7, 24.9, 24.8, 23.3, 23.2, 23.0, 22.4, 21.9, 19.3, and 18.1 kcal/mol, respectively. The electron-withdrawing substituents form internal dipoles whose electrostatic interactions contribute to both the decreased proton affinities of (B) and the decreased binding energies of the protonated dimers BH+B. The bonding energies also vary with rotation about the hydrogen bond, and they decrease in rotamers where the internal dipoles of the components are aligned efficiently for inter-ring repulsion. For compounds substituted at the 3 or 4 (meta or para) positions, the lowest energy rotamers are T-shaped with the planes of the two rings rotated by 90° about the hydrogen bond, while the planar rotamers are weakened by repulsion between the ortho hydrogen atoms of the two rings. Conversely, in ortho-substituted (1,2-diazine)2H+ and (2-F-pyridine)2H+, attractive interactions between the ortho (C-H) hydrogen atoms of one ring and the electronegative ortho atoms (N or F) of the other ring are stabilizing, and increase the protonated dimer binding energies by up to 4 kcal/mol. In all of the dimers, rotation about the hydrogen bond can involve a 2-4 kcal/mol barrier due to the relative energies of the rotamers. [ABSTRACT FROM AUTHOR]

We present a comprehensive ab-initio study of electron collisions with pyrazine, pyrimidine, and pyridazine. The emphasis is placed on the identification and characterization of electron resonances in these systems. We use the R-matrix method and show that analysing the time-delay reveals resonances whose signature is not visible in the eigenphase sums. In addition to the well known π* resonances below 5 eV, we find three core-excited shape resonances in the energy range 5.5-8.5 eV and a few Feshbach resonances in the dipolar molecules. Additionally, 11 resonances with little effect on the elastic scattering from ground state diazines (but significant effect in elastic collisions with the molecules in an excited state) are found and characterized. We correlate these resonances across the three molecules and discuss their possible correspondence to resonances described in earlier studies on uracil. [ABSTRACT FROM AUTHOR]

A highly efficient and practical procedure for chemo‐ and regioselective synthesis of ortho‐diacylbenzenes through Pd‐catalyzed oxidative C–H bond activation has been developed. Using this method, a variety of ortho‐diacylbenzenes were prepared in moderate to good yields, by direct acylation of diazines with toluene derivatives as acylation source. Ortho‐diacylbenzenes may be used as precursors in synthesis of pharmaceuticals and agrochemicals. [ABSTRACT FROM AUTHOR]

A series of representative diazines and pyridine N‐oxides were subjected to alkylation using several different alkylating agents. The 15N NMR chemical shifts (δN values) of the diazines, pyridine N‐oxides and derived alkylation products were determined using 1H‐15N HMBC NMR spectroscopy at natural 15N abundance. The changes in the 15N NMR chemical shifts (Δ(δN) values) that occurred on going from starting materials to products in these reactions were analyzed. N‐alkylation of diazines resulted in large upfield shifts of the δN values of the alkylated nitrogen (of the order of 100 ppm or greater). While O‐alkylation of pyridine N‐oxides resulted in upfield shifts of the δN values of the N‐(alkoxy)pyridinium nitrogen, the Δ(δN) values were of a much smaller magnitude (ca. –42 ppm) than those observed for N‐alkylations of diazines. Nitrogen NMR spectroscopic data from the literature of relevance to alkylation of azines, diazines, azine N‐oxides and diazine N‐oxides was gathered together, and using this in tandem with our 15N NMR spectroscopic data, we have been able to corroborate our observations on the trends observed in the Δ(δN) values associated with N‐ and O‐alkylation reactions of aromatic N‐heterocycles and N‐oxides. An analysis protocol that relies on synergistic evaluation of 1H‐15N HMBC and 1H‐13C HMBC NMR spectra has been developed that enables unambiguous diagnosis of the occurrence of N‐alkylation of aromatic N‐heterocycles and O‐alkylation of aromatic N‐oxides. [ABSTRACT FROM AUTHOR]

Non-covalent interaction plays an important role in different π-system, aromatic compounds and other biomolecules. The π-π stacking interaction between heteroaromatic systems is an important area of research. Herein, we have taken one simple organic heterocycle such as a diazine molecule and some of its isomers to investigate the π-π stacking interaction. Stacking interactions of heterocycles are highly sensitive towards the position, bond angle and dihedral angle of the heteroatoms and it also results in different interactions for different stacked models. We have chosen the stacked dimers of diazine isomers (1,2-diazine, 1,3-diazine and 1,4-diazine) and quantum mechanical studies have been carried out to compute the π-π stacking interaction using (Møller-Plesset) MPn methods. The diazine isomers show variation in stacking interaction with different intermolecular rotation and we observed a conformational variation in different stacked models of diazine. [ABSTRACT FROM AUTHOR]

A linear Cu 4 complex containing a combination of square pyramidal and octahedrally coordinated Cu(II) ions is reported. The metal centres are linked via diazine and chloride bridges. Magnetic studies reveal the presence of strong antiferromagnetic interactions via the diazine bridge and moderate ferromagnetic interactions via the chloro bridges. The pyrimidinyl hydrazone ligand O C{NHN C(Me)(pm)} 2 (pm = 2-pyrimidinyl) (L 3 H 2) has two potentially protic H atoms and multiple donor atoms. The reaction of L 3 H 2 with CuCl 2 ·2H 2 O yielded the tetranuclear complex [Cu 4 (L 3 H) 2 Cl 6 (CH 3 OH) 2 ] (1). Structural studies on 1 reveal the molecule is located about a crystallographic inversion centre, affording two crystallographically independent Cu(II) centres with the two symmetry equivalent [Cu 2 (L 3 H)Cl 3 CH 3 OH] units connected via µ 2 -Cl bridges to generate a linear tetranuclear copper complex. The ligand is singly deprotonated (L 3 H−) and twisted around the diazine N N′ bond, affording an N 3 donor set for the Cu1 centre and an N 2 O donor set for the Cu2 centre. The Cu1 ion is five coordinate with an [N 3 ] donor set from the L 3 H− ligand and the remaining two sites occupied by Cl− anions. The Cu2 ion is six coordinate with the L 3 H− ligand offering a mer [N 2 O] donor set, with the three remaining sites occupied by two Cl− anions and a MeOH molecule. Magnetic studies reveal the presence of strong antiferromagnetic interactions via the diazine bridge linking the Cu1 and Cu2 ions and moderate ferromagnetic interactions via the chloro bridges located about the inversion centre, connecting the Cu2 and Cu2i ions. [ABSTRACT FROM AUTHOR]

The three‐dimensional framework 3∞[LaCl3(pyz)] and the dimeric complexes [Ln2Cl6(pyz)(py)6]·2pyz (Ln = Sm, Er) were obtained from solvothermal reaction of the respective chlorides LnCl3 with pyrazine (pyz) in pyridine (py) at 200 °C. In the compounds, pyrazine ligands interlink Ln‐cations: in the complexes to a dimer, in the framework structure to 2D sheets, which are further connected via chloride bridges. This results in an uninodal 6‐c net with the point symbol (48.67) and a variant of the sxa topology. The dimeric complexes exhibit 4f‐based emission in the visible for samarium and in the NIR for erbium, both sensitized by the pyrazine ligands, as mechanistic insights show. [ABSTRACT FROM AUTHOR]

Coordination complexes can be used to photocage biologically active ligands, providing control over the location, time, and dose of a delivered drug. Dual action agents can be created if both the ligand released and the ligand-deficient metal center effect biological processes. Ruthenium(ii) complexes coordinated to pyridyl ligands generally are only capable of releasing one ligand in H2O, wasting equivalents of drug molecules, and producing a Ru(ii) center that is not cytotoxic. In contrast, Ru(ii) polypyridyl complexes containing diazine ligands eject both monodentate ligands, with the quantum yield (ΦPS) of the second phase varying as a function of ligand pKa and the pH of the medium. This effect is general, as it is effective with different Ru(ii) structures, and demonstrates that diazine-based drugs are the preferred choice for the development of light-activated dual action Ru(ii) agents. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterisation of a family of three CoII4 and two CoII3 complexes from a symmetrical diazine ligand, H2hyda = N,N-bis(3-methoxy salicylidene)hydrazine. The metallic skeletons of all complexes reveal a nearly linear arrangement of CoII centers. The present results highlight the profound influence of anions on the structural outcome of a complex. Furthermore, distortion imposed by the twisted nature of the diazine-based ligand depends on the use of associated anions which results in triple helical CoII4 and double helical CoII3 entities. The CoII ions in complexes 1–3 are antiferromagnetically coupled leading to an S = 0 ground state. In contrast, complexes 4 and 5 exhibit a magnetic ground state, but exhibit different behaviours at low temperatures due to differences in crystal packing and hence intermolecular interactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Fluorinated thiosemicarbazones derived from N -(diethylaminothiocarbonyl)benzimidoyl chlorides show a considerable activity against Trypanosoma cruzi , the parasite, which is responsible for Chaga's disease. Highlights • Biologically active thiosemicarbazones with N -(diethylaminothiocarbonyl)benzamidine fragments have been prepared. • Fluorination of the compounds enhances their activity against the parasite Trypanosoma cruzi. • Fluorinated 6-amino-1,3,5-thiadiazine-2-thiones are formed by slight modifications of the reaction conditions. Abstract A series of thiosemicarbazones was obtained by condensation of halogenated N -(diethylaminothiocarbonyl)benzimidoyl chlorides (3b–3h) with 4,4-dimethyl-3-thiosemicarbazide. The activity of the halogenated compounds against the parasite Trypanosoma cruzi was evaluated and compared to the previously reported activity of the corresponding non-substituted thiosemicarbazone. It was found that the halogen-substitution enhances in most cases the anti-parasitic activity. The meta -fluorinated compound (4g) was identified as the most potent one (IC 50 = 9.0 μM, CC 50 > 200 μM), having a selectivity index (SI = IC 50 /CC 50), which is 4-times higher than that of the non-substituted compound. Slight modification of the reaction conditions employed for the synthesis of some of the benzoylthioureas 3a–3g led to the unexpected formation of novel halogenated 6-amino-1,3,5-thiadiazine-2-thiones. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Four series of tetrahydro-2 H -1,3,5-thiadiazine Thione (THTT) derivatives. • New THTT derivatives were screened for their in vitro antileishmanial activity. • Most of the compounds showed significant antileishmanial activity. • Comparative cytotoxicity of compounds (9c vs 10a) was also examined. • Predicted physicochemical parameters showed good drug-like characteristics. Abstract Four series of heterocyclic compounds, namely, tetrahydro-2 H -1,3,5-thiadiazine thione derivatives were synthesized in good to excellent yields and were screened for their in vitro antileishmanial activities against Leishmania major (promastigotes). Most of the compounds showed significant antileishmanial activity within the range of IC 50 = 15.48–39.36 μM when compared with standard pentamidine (IC 50 = 14.95 μM). The structure-activity relationship showed that N-3 and N-5 substituents have a key role against leishmanicidal activity. The ester analogues (series B) were found to have a 1.5 to 5-fold reduced activity compared to their acidic counterparts. Cytotoxicity against mammalian mouse fibroblast 3 T3 cells was also evaluated and compared between the acid and its ester analogue. The reduction of antileishmanial activity and loss of toxicity in the newly developed THTT ester derivative indicates that these compounds can be used as a template study for the production of effective antileishmanial ester prodrugs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 3,4,4,5-Tetrachloro-4 H -1,2,6-thiadiazine reacts with cat. BnEt 3 NCl to give a mixture of mono- and polycyclic heterocycles. • Single crystal X-ray studies support the structures of four minor products. • Independent synthesis for 8-bromo-4-chloropyrrolo[2′,1′:2,3]imidazo[4,5- c ][1,2,6]thiadiazine-6,7-dicarbonitrile. Abstract 3,4,4,5-Tetrachloro-4 H -1,2,6-thiadiazine was reacted with BnEt 3 NCl (10 mol%) to give perchloro-9-thia-1,5,8,10-tetraazaspiro[5.5]undeca-1,4,7,10-tetraene (up to 18% yield), 4,5,6-trichloropyrimidine-2-carbonitrile (up to 44% yield) and four minor side products: 2,7-dichlorothiazolo[5,4- d ]pyrimidine-5-carbonitrile, 2-(4-chloro-6 H -thiazolo[5,4- c ][1,2,6]thia-diazin-6-ylidene)malononitrile, 4,8-dichloropyrrolo[2′,1′:2,3]imidazo[4,5- c ][1,2,6]thiadiazine-6,7-dicarbonitrile and 4,7-dichloro-[1,2,6]thiadiazino[3,4- b ]thiazolo[5,4- e ][1,4]diazepin-9(10 H)-one. Single crystal X-ray studies support the structures of the minor products. Tentative rationale for the formation of these minor products and the synthesis of 8-bromo-4-chloropyrrolo[2′,1′:2,3]imidazo[4,5- c ][1,2,6]thiadiazine-6,7-dicarbonitrile are presented. [ABSTRACT FROM AUTHOR]

The synthesis of the novel redox active ligand 3-(2′,6′-pyrimidine)-benzo-1,2,4-thiadiazine (pmbtdaH) is reported. The radical pmbtda can be prepared by in situ 1 e − oxidation and its radical character confirmed by EPR spectroscopy, along with DFT calculations of the spin density distribution. Reaction of pmbtdaH with ZnCl 2 ·2H 2 O in a 1:1 mol ratio afforded the dinuclear complex Zn 2 Cl 4 (pmbtdaH) 2 ( 1 ) in which the two trigonal bipyramidal metal centres are linked via μ 2 -bridging Cl − ligands while the pmbtdaH ligand binds in an N,N′-chelate fashion via N(4) and the pyrimidinyl N(1) atom. The outcome of the reaction of pmbtdaH with Zn(hfac) 2 (hfac = hexafluoroacetylacetonate) proved sensitive to the crystallization method; the mononuclear octahedral complex Zn(hfac) 2 (pmbtdaH) ( 2 ) in which the ligand coordinates in a similar N,N′-chelate fashion to that observed in 1 was isolated by layering a concentrated CH 2 Cl 2 solution with hexane. Conversely the same reaction mixture afforded the tetranuclear complex Zn 4 (hfac) 6 (pmbtda ox ) 2 ( 3 ) when left undisturbed in a sealed vial. In 3 the ligand is both deprotonated and oxidized forming an anionic ligand in which there are two potential N,N′-chelate pockets and an additional S-oxide donor. The pmbtda ox − ligand bridges between a Zn(hfac) 2 and a Zn(hfac) unit to form Zn 2 (hfac) 3 (pmbtda ox ). Two such Zn 2 (hfac) 3 (pmbtda ox ) units dimerise through the S-oxide oxygen atom to form a centrosymmetric tetranuclear Zn 4 (hfac) 6 (pmbtda ox ) 2 cluster. The structures of 1 – 3 have been determined by X-ray diffraction, elemental analysis, IR and UV–Vis spectroscopies as well as 1 H NMR spectroscopy for complex 2 . [ABSTRACT FROM AUTHOR]

Heteroaryl thioethers, comprised of pyridines and diazines, are an important class of compounds with relevance to medicinal chemistry. Metal-catalyzed cross-couplings and S N Ar reactions are traditionally used to form C–S bonds in these systems but are limited by available halogenated precursors. An alternative approach is presented where pyridines and diazines are transformed into heterocyclic phosphonium salts and then C–S bonds are formed by adding thiolate nucleophiles. The process is 4-selective for pyridines, simple to execute and can be used to make derivatives of complex pharmaceuticals. [ABSTRACT FROM AUTHOR]

A straightforward process to aminate pyridines and diazines is presented by reacting phosphonium salt derivatives with sodium azide. The iminophosphorane products are versatile precursors to several nitrogen-containing functional groups, and the process can be applied to building block heterocycles, to drug-like fragments, and for late-stage functionalization of complex pharmaceuticals. Appealing features of this strategy include using C-H bonds as precursors, precise regioselectivity, and a distinct scope from other amination methods, particularly those relying on halogenated azaarenes. [ABSTRACT FROM AUTHOR]

The development of a commercial manufacturing route to verubecestat (MK-8931) is described, highlights of which include the application of a continuous processing step to outcompete fast proton transfer in a Mannich-type ketimine addition, a copper-catalyzed amidation reaction, and an optimized guanidinylation procedure to form the key iminothiadiazine dioxide core. [ABSTRACT FROM AUTHOR]

Carbon disulfide complexes with diazine (pyridazine, pyrimidine or pyrazine) have been studied by density functional BLYP-D3 and ab initio CCSD(T) methods. All possible conformers of these complexes have been found. In the chalcogen bonded complexes, the CCSD(T)/cc-pvtz calculated interaction energies (ΔE) range between −0.89 and −2.19 kcal mol −1 . These complexes are more stable than those stabilized by hydrogen bond. The linear correlation between the ΔE and the most negative values of the electrostatic potential surfaces (V s,min ) on the nitrogen atom of the diazines has been found. According to the symmetry-adapted perturbation theory (SAPT) analysis, in the chalcogen bonded complexes among all of the attraction forces the electrostatic component is the most important one, while in the hydrogen bonded and stacking complexes the dispersion contribution is the leading term. Moreover, the Natural Bond Orbitals (NBO), AIM and Noncovalent Interaction Index (NCI) analyses have been performed. [ABSTRACT FROM AUTHOR]

A new dinuclear cobalt(III) compound [Co (2,2 ′-azinodimethyldiphenol)] has been synthesized, which shows better cytotoxic activity than carboplatin and exhibits potent in vitro antiproliferative activity . [ABSTRACT FROM AUTHOR]

The title compound, ( E)-1-(2,6-diisopropylphenyl)-2-phenyldiazine (I), was synthesized and characterized using a combination of H, C, and N NMR spectroscopy, infrared and UV/Vis spectroscopy, X-ray crystallography, and GC mass spectrometry. The solid-state structure is also reported. The unsymmetric azobenzene crystallizes in the space group P2/c with unit cell parameters a = 8.001(7) Å, b = 17.827(16) Å, c = 11.129(10) Å, β = 101.960(10)°, V = 1553(2) Å, Z = 4, D = 1.139 g/cm. Graphical Abstract: The synthesis of ( E)-1-(2,6-diisopropylphenyl)-2-phenyldiazine (I) and its characterization using a combination of combination of H, N, and C NMR spectroscopy, infrared and UV/Vis spectroscopy, mass spectrometry, and X-ray crystallography is described in this report. [ABSTRACT FROM AUTHOR]

Complexes and coordination polymers were obtained from trivalent lanthanide chlorides together with thiazole (thz) and the diazine ligands pyrazine (pyz) and pyrimidine (pym). The compounds [ Ln2Cl6(pyz)(thz)6] ·2thz ( Ln = Tb, Er), 1∞[Pr2Cl6(pyz)(thz)6], and [ Ln2Cl6(pym)2(thz)4] ( Ln = Tb, Er) could be obtained, their crystal structures, luminescence as well as thermal properties were determined. The compounds with Tb and Er show intense luminescence with a strong sensitizer effect of the ligands that can be observed by dominant ligand excitation and exclusive metal emission for VIS and NIR. [ABSTRACT FROM AUTHOR]

A series of 7-azinyl-substituted triazolopyridines and 3-(6-azinyl- substituted 2-pyridyl)triazolopyridines were synthesized by addition of the corresponding 3-substituted 7-lithiotriazolopyridine to pyrimidine, pyrazine, pyridazine, and 1,3,5-triazine respectively, followed by hydrolysis and oxidation. [ABSTRACT FROM AUTHOR]

Mono- and dinuclear N-heterocyclic carbene palladium complexes with diazine ligands were synthesized and characterized through adjusting the stoichiometric ratio of the reactants. The catalytic properties of all complexes were further studied in the Mizoroki–Heck reaction. The results indicated that the dinuclear complexes induced some benefits in catalytic behavior. [ABSTRACT FROM PUBLISHER]

This article presents the photophysical properties of a series of diazine chromophores. The influence of five parameters has been studied: the presence of a diazine/benzodiazine fragment, the nature of the diazine fragment (1,3-diazine/1,4-diazine), the presence or not of an vinyl linker between diazine ring and phenylene fragments of the π-conjugated bridge, the presence of a phenylene/biphenylene linker and the nature of electron donating group (dimethylamino/diphenylamino). Taguchi's design of experiment combined with analysis of variance methodologies have been employed to highlight the main structural parameters influencing the position of absorption and emission maxima of dichloromethane solution and the extend of emission solvatochromic range exhibited by this family of chromophores. [ABSTRACT FROM AUTHOR]

A novel series of benzofuran derivatives containing thiazole, thiadiazine, and pyridotriazolopyrimidine were synthesized starting from 1-(benzofuran-2-yl)-3-(1 H-indol-3-yl)prop-2-en-1-one. Also, triazolopyrimidine derivatives were prepared from the reaction of 2-acetylbenzofuran and pyrazole-4-carbaldehyde with 2-thiobarbutyric acid and reaction of the product with hydrazonoyl halides. The structures of the newly synthesized compounds were elucidated on the basis of elemental analyses, spectral data, and alternative synthetic routes whenever possible. Anticancer activity against 60 different human tumor cell lines representing leukemia, melanoma, and cancers of the lung, colon, brain, ovary, breast, prostate, and kidney was validated by the U.S. National Cancer Institute using a two-stage process. The results revealed that pyrazoline-1-thiocarbohydrazide 4b, triazolopyrimidine 20d, and pyrimidine thione 25 have promising antitumor activity against most cell lines. [ABSTRACT FROM AUTHOR]

The electrochemical properties of twenty 3-aryl-quinoxaline-2-carbonitrile 1,4-di-N-oxide derivatives with varying degrees of cytotoxic activity were investigated in dimethylformamide (DMF) using cyclic voltammetry and first derivative cyclic voltammetry. With one exception, the first reduction of these compounds was found to be reversible or quasireversible and is attributed to reduction of the N-oxide moiety to form a radical anion. The second reduction of the diazine ring was found to be irreversible. Compounds containing a nitro group on the 3-phenyl ring also exhibited a reduction process that may be attributed to that group. There was good correlation between molecular structure and reduction potential, with reduction being facilitated by an enhanced net positive charge at the electroactive site created by electron withdrawing substituents. Additionally, the reduction potential was calculated using two common basis sets, 6-31g and lanl2dz, for five of the test molecules. There was a strong correlation between the computational data and the experimental data, with the exception of the derivative containing the nitro functionality. No relationship between the experimentally measured reduction potentials and reported cytotoxic activities was evident upon comparison of the data. [ABSTRACT FROM AUTHOR]