Regioselective synthesis of novel substituted indazole-5,6-diamine derivatives

The synthesis of a series of novel indazole-5,6-diamine derivatives is described. This indazole ring system was incorporated in an octahydropyrrolo[3,4-b]phenazine scaffold and was diversely and regioselectively substituted on the nitrogen atoms at the 5- and 10-positions. Thus, the nitrogen atom at the 5-position was found to be more reactive toward electrophiles than the one at the 10-position. This difference of reactivity could be attributed to the electronic effect of the pyrazole moiety. Moreover, an unexpected tetrahydropyran protecting group migration was observed from the N-1 atom to the C-11 position of the octahydropyrrolo[3,4-b]phenazine scaffold.     

Caractéristiques des spectres de résonance paramagnétique électronique des radicaux formés à partir des tétrahydro-1,2,3,4 et octahydro-1,2,3,4,6,7,8,9 phénazine

A detailed analysis of the E. P. R. spectra of the anion and diprotonated cation radicals of partly hydrogenated phenazine derivatives is presented. Furthermore, the gyromagnetic ratios of the pyrazine, tetramethylpyrazine, quinoxaline and phenazine radicals are measured. Higher than those of the corresponding aromatic radicals, the g factors are correlated to the nitrogen hyperfine coupling constant. This shows the effect of the 2p spin-orbit coupling of the nitrogen and of the unpaired electron-spin density on the nitrogen in this series of 1,4-diazines.     

Effect of conjugated core building block dibenzo[a,c]phenazine unit on π‐conjugated electrochromic polymers: Red‐shifted absorption

A comparative investigation was undertaken for the electrosynthesis and electrochemical properties of three different electroactive polymers having a conjugated core building block, dibenzo[a,c]phenazine. A series of monomers has been synthesized as regards to thiophene based units; thiophene, 3‐hexyl thiophene, and 3,4‐ethylenedioxythiophene. The effects of different donor substituents on the polymers' electrochemical properties were examined by cyclic voltammetry. Introducing highly electron‐donating (ethylene dioxy) group to the monomer enables solubility while also lowering the oxidation potential. The planarity of the monomer unit enhances π‐stacking and consequently lowering the E_g from 2.4 eV (PHTP) to 1.7 (PTBP). Cyclic voltammetry and spectroelectrochemical measurements revealed that 2,7‐bis(4‐hexylthiophen‐2‐yl)dibenzo[a,c]phenazine (HTP) and 2,7‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)dibenzo[a,c]phenazine (TBP) possessed electrochromic behavior. The colorimetry analysis revealed that while PTBP have a color change from red to blue, PHTP has yellow color at neutral state and blue color at oxidized state. Hence the presence of the phenazine derivative as the acceptor unit causes a red shift in the polymers' absorption to have a blue color. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1714–1720, 2010     

Reactivities of heterocyclic quinoneimines (review)

Data on the reactions of phenazine, phenoxazine, and phenothiazine derivatives in which the bridge nitrogen atom is included in a quinoneimine fragment are correlated. The effect of the nature of the second bridge heteroatom, benzo annelation, and activation of the substrate and the reagent on the reactivities of the heterocyclic quinoneimines cited above is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1030, August, 1989.     

Alkynylated phenazines: synthesis, characterization, and metal-binding properties of their bis-triazolyl cycloadducts

We have synthesized a series of ethynylated phenazines and their bis-triazolyl cycloadducts to serve as metal ion sensors. Binding of metal ions is achieved through coordination to the phenazine nitrogen atom and the triazole ring. To allow metal sensing in aqueous solution, the triazole units are substituted with water-soluble ethylene glycol chains. These phenazine cycloadducts exhibit a selective affinity for binding silver ions. Examination of the halogenated analogues reveals a lowering of the band gap and the corresponding bathochromic shifts in the absorption and emission spectra. The electron-withdrawing properties of these halogens also result in significantly decreased metal-binding activity of the phenazine cycloadducts.     

Dibenzophenazine derivatives as visible photosensitizers for diaryliodonium salts

The use of two dibenzo[a,c]phenazine derivatives, 10,13‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)dibenzo[a,c]phenazine and 10,13‐bis(4‐hexylthiophen‐2‐yl)dibenzo[a,c]phenazine are reported as photosensitizers for diaryliodonium salt photoinitiators. Novel dyes based on the dibenzo[a,c]phenazine skeleton are shown to be efficient in carrying out the cationic photopolymerizations. Representative examples of different types of monomers including epoxide, and vinyl monomers are polymerized in the presence of the photosensitizers and diphenyliodonium hexafluorophosphate (Ph₂I⁺PF). Polymerizations are initiated at room temperature using long wavelength UV and visible light, and monitored by optical pyrometry. The photopolymerization of an epoxide monomer via solar irradiation is also demonstrated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Carpet Beater Molecules: Synthesis and Characterization of Functional Hexa-peri-benzocoronene–Alkyne Coupling Products

Within the scope of this paper, nine π-expanded mono-substituted 5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronenes (HBC) are introduced. 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronene served as precursor and was reacted with ethynyltrimethylsilane in a Sonogashira coupling reaction. The acetylene unit is used as a linker and can undergo another Sonogashira coupling reaction combining different phenyl coupling partners with the HBC core. The electron-withdrawing groups such as nitrile, pyridine and carbonyl species (aldehyde, methylester, carboxylic acid) as well as the three quinoxaline based species (diphenylquinoxaline, dibenzo[a,c]phenazine, phenanthro[4’,5’-a,b,c]phenazine) serve as substitution moieties. Their influence on the optoelectronic properties were investigated by UV/Vis absorption spectroscopy demonstrating a maximum redshift of 7 nm compared to starting compound 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl) HBC. As for the phenanthro[4’,5’-a,b,c]phenazine substituted HBC a dramatic decrease in the intensity of the absorption of the UV/Vis spectrum was observed. The fluorescence spectroscopy pointed out that the dibenzo[a,c]phenazine and phenanthro[4’,5’-a,b,c]phenazine substitution changed the spectra to one broad peak departing from the characteristic HBC-like emission pattern.     

A reinvestigation of the bamberger-ham phenazine. Synthesis: A limitation

The Bamberger-Ham condensation of 4-substituted nitrosobenzenes in concentrated sulfuric acid reported as a method of synthesis for phenazine N-oxides has been found to be limited to electron donating substituents. Methyl 4-nitrosobenzoale has been found to react under these conditions to give dimethyl 2-nitrodiphenylamine-4, 5-diearboxylate ( 2 ). Compounds of unknown structure previously reported to arise from acid treatment of 4-bromo- and 4-chloronilrosobenzene have been shown to be 4, 5-dibromo-2-nitrosophenylamine ( 10 ) and the analogous dichloro compound. Treatment under stronger acidic conditions (oleum) converted 10 but not 2 into the corresponding phenazine N-oxide. Mechanistic implications are discussed.     

Role of electronic structure on DNA light-switch behavior of Ru(II) intercalators

A series of ruthenium(II) complexes possessing ligands with an extended pi system were synthesized and characterized. The complexes are derived from [Ru(bpy)3](2+) (1, bpy = 2,2'-bipyridine) and include [Ru(bpy)2(tpphz)](2+) (2, tpphz = tetrapyrido[3,2-a:2',3'-c:3',2'-h:2',3'-j]phenazine), [Ru(bpy)2(dppx)](2+) (3, dppx = 7,8-dimethyldipyrido[3,2-a:2',3'-c]phenazine), [Ru(bpy)2(dppm2)](2+) (4, dppm2 = 6-methyldipyrido[3,2-a:2',3'-c]phenazine), and [Ru(bpy)2(dppp2)](2+) (5, dppp2 = pyrido[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline). The excited-state properties of these complexes, including their DNA "light-switch" behavior, were compared to those of [Ru(bpy)2(dppz)](2+) (6, dppz = dipyrido[3,2-a:2',3'-c]phenazine). Whereas 2, 3, and 4 can be classified as DNA light-switch complexes, 5 exhibits negligible luminescence enhancement in the presence of DNA. Because relative viscosity experiments show that 2-6 bind to DNA by intercalation, their electronic absorption and emission spectra, electrochemistry, and temperature dependence of the luminescence were used to explain the observed differences. The small energy gap between the lowest-lying dark excited state and the bright state in 2-4 and 6 is related to the ability of these complexes to exhibit DNA light-switch behavior, whereas the large energy gap in 5 precludes the emission enhancement in the presence of DNA. The effect of the energy gap among low-lying states on the photophysical properties of 1-6 is discussed. In addition, DFT and TD-DFT calculations support the conclusions from the experiments.     

Synthesis of 5,6-Dimethylbenz[a]phenazine

5,6-Dimethylbenz[a]phenazine ( 4 ), an aza analogue of the carcinogenic 5,6-dimethylbenz-[c]acridine has been obtained by a 1,1-dehydration-rearrangement (Wagner-Meerwin type) from 5,5-dimethyl-6-hydroxy-5,6-dihydrobenz[a]phenazine ( 3 ). The alcohol 3 was obtained from the hydrogenation of the corresponding ketone 2 which was prepared in two ways: Method A, the oxidation of 5,5-dimethyl-5,6-dihydrobenz[a]phenazine ( 1 ); Method B, the hydrolysis of the 6,6-dibromo derivative 5 of 1.     

Photophysical properties of ruthenium(II) polyazaaromatic compounds: a theoretical insight

Quantum-chemical methods are applied to study the nature of the excited states relevant in the photophysical processes (absorption and emission) of a series of polyazaaromatic-ligand-based ruthenium(II) complexes. The electronic and optical properties of the free polyazaaromatic ligands and their corresponding ruthenium(II) complexes are determined on the basis of correlated Hartree-Fock semiempirical approaches. While the emission of complexes containing small-size ligands, such as 1,10-phenanthroline or 2,2'-bipyridine, arises from a manifold of metal-to-ligand charge-transfer triplet states ((3)MLCTs), an additional ligand-centered triplet state ((3)L) is identified in the triplet manifold of complexes containing a pi-extended ligand such as dipyrido[3,2-a:2',3'-c]phenazine, tetrapyrido[3,2-a:2',3'-c:3',2'-h:2',3'-j]phenazine, and 1,10-phenanthrolino[5,6-b]-1,4,5,8,9,12-hexaazatriphenylene. Recent experimental data are interpreted in light of these theoretical results; namely, the origin for the abnormal solvent- and temperature-dependent emission measured in pi-extended Ru complexes is revisited.     

Calcium and strontium,and zinc (phenazine)−· species

Calcium and strontium react with phenazine in tetrahydrofuran (THF) at ca 20 ° C to yield red solutions containing paramagnetic species based on (phenazine)⁻· (ESR characterization). Zinc reacts in THF in the presence of zinc chloride or bromide, or without metal halide in pyridine, to yield green or red ESR-active solutions also based on (phenazine)⁻·, and then, for the reaction in pyridine, a brown paramagnetic solid of composition Zn(phenazine)(pyridine)₂.     

Investigation of free radicals from N-substituted dihydrophenazines

A number of N-substituted dihydrophenazines were synthesized. New, neutral radicals of the phenazine series were obtained by oxidizing them with lead dioxide, and several of their properties were studied (EPR spectra and electronic spectra).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1428–1431, October, 1970.     

Sequestering aromatic molecules with a spin-crossover Fe(II) microporous coordination polymer

All in a spin: A series of three-dimensional porous coordination polymer {Fe(dpe)[Pt(CN)(4)]}?G (dpe = 1,2-di(4-pyridyl)ethylene; G = phenazine, anthracene, or naphthalene) exhibiting spin crossover and host-guest functions is reported. The magnetic properties of the framework are very sensitive to the chemical nature (aromatic or hydroxilic solvents) and the size of the included guest molecules.     

New quinoxaline derivatives as accepting units in donor–acceptor type low‐band gap polymers for organic photovoltaic cells

A series of new donor–acceptor‐type low‐band‐gap semiconducting polymers were synthesized as electron donors for organic photovoltaic cells. The polymers comprised quinoxaline derivatives as the acceptors and a benzodithiophene (BDT) derivative as the donors. 5,8‐Dibromoquinoxaline (Qx), 8,11‐dibromobenzo[a]phenazine (BPz), 10,13‐dibromodibenzo[a,c]phenazine (DBPz), and 8,11‐dibromo‐5‐(9H‐carbazol‐9‐yl)benzo[a]phenazine) (CBPz) were synthesized and polymerized with 2,6‐bis(trimethyltin)?4,8‐diethylhexyloxybenzo‐[1,2‐b;3,4‐b]dithiophene (BDT) through Stille cross‐coupling to produce four types of fully conjugated semiconducting polymers: PBDT‐Qx, PBDT‐BPz, PBDT‐DBPz, and PBDT‐CBPz , respectively. Intramolecular charge transfer between the electron donating and accepting units in the polymeric backbone induced a broad absorption from 300 to 800 nm. The optical band gap energies of the polymers were measured from their absorption onsets to be 1.54–1.80 eV depending on the polymer structure. Solution‐processed field‐effect transistors were fabricated to measure the hole mobilities of the polymers, and bulk hetero‐junction photovoltaic devices were fabricated using the synthesized polymers as electron donors and fullerene derivatives as electron acceptors. One of these devices showed a high power conversion efficiency of 3.87% with an open‐circuit voltage of 0.78 V, a short‐circuit current of 9.68 mA/cm², and a fill factor of 0.51 under air mass 1.5 global (AM 1.5 G) illumination conditions (100 mW/cm²). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4136–4149     

Vibrational analyses,vibronic coupling and identification of electronic origins in the lower 1nπ* and 1ππ* states of phenazine and acrid

The spectra of the lowest ¹ nπ2 and ¹ ππ2 singlets of phenazine and acridine were studied in a biphenyl matrix at 2 K. The major findings are: (1) The lowest ππ2 singlets L^a and L^b in phenazine and acridine are clearly located and the vibrational analysis of these states support their assignments. (2) Good evidence is presented that a ¹ nπ2 state is the lowest excited singlet in acridine. The ¹nπ2 origin. The fact that the ¹L^a spectrum of acridine is twenty times broder than the ¹ L^a spectrum of antharacone which is otherwise very similar, is additional evidence that the nπ2 is the lowest excited singlet. (3) Three b^2g and three b^1g out-of-plane modes act as false origins for the long- and short-axis nπ2 spectra of phenazine. (4)Sharp lines in the region of phenazine's second singlet are shown to come from the lower ¹B^3u state and appear to be the same type of vibration interference as described by Wessel. (5) The vibrational analysis of the pure crystal spectra of phenazine published previously has been resigned.     

Polynuclear heterocyclic compounds containing an indole fragment

Derivatives of 6,7,9,10,11,12-hexahydro-5H-indolo[3,2,1-d,e]phenazine and 1,2,3,4-tetrahydroindolo[1,2-a]quinoxaline were obtained by condensation of the sodium derivatives of 1-keto-1,2,3,4-tetrahydrocarbazoles and 2-aroylindoles, respectively, with-bromocyclohexanone dimethylketal. These compounds are converted to derivatives of indolo[1,2-a]-quinoxaline, 5,6-dihydroindolo[1,2-a]quinoxaline, and 8a,9,10,11,12,12a-hexahydro- and 5,6,7,7a,8a,9,10,11,12,12a-decahydro-8H-indolo[3,2,1-d,e]phenazine by dehydrogenation over a Raney nickel catalyst and reduction with sodium in alcohol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1348–1352, October, 1970.     

Zirconium@guanine@MCM-41 nanoparticles: An efficient heterogeneous mesoporous nanocatalyst for one-pot,multi-component tandem Knoevenagel condensation–Michael addition–cyclization Reactions

MCM-41-supported nanoscale guanine bonded with Zr (IV) was prepared using sol–gel method and characterized by FT-IR, Raman, XRD, BET, TGA, EDX, ICP, AAS, X-Ray mapping, SEM and TEM techniques. This compound was employed as an efficient, chemoselectivity and green heterogeneous catalyst in order to prepare a series of benzo[a]benzo[6,7]chromeno[2,3-c]phenazine and spiro[benzo[a]benzo[6,7]chromeno[2,3-c] phenazine] derivatives by one-pot, four-component domino reaction from the 2-hydroxy-1,4-naphthoquinone, benzene-1,2-diamines, 2-hydroxy-1,4-naphthoquinone and carbonyl compounds in PEG, at 100 °C and, also, Bis (pyrazolyl) methane derivatives using aldehydes and 3-Methyl-1-phenyl-5-pyrazolone in ethanol under reflux condition. Results indicated that all products were synthesized in short reaction times and high yields in the ranges 78–99%. The Zr-guanine-MCM-41 can be recycled four runs without any significant loss of its catalytic activity. In addition, the stability of the catalyst was confirmed by metal leaching, heterogeneity tests, SEM and FT-IR techniques.     

Synthesis of novel fluorescent benzo[a]pyrano[2,3-c]phenazine and benzo[a]chromeno[2,3-c]phenazine derivatives via facile four-component domino protocol

An efficient and practical route to novel fluorescent benzo[a]pyrano[2,3-c]phenazine framework has been developed by one-pot, four-component reaction of 2-hydroxynaphthalene-1,4-dione, 1,2-phenylenediamines, aromatic aldehydes, and Meldrum’s acid in glacial acetic acid at 70 °C. Photophysical studies of these compounds have been reported. Reactions involving cyclohexane-1,3-dione/5-methylcyclohexane-1,3-dione/dimedone in the place of Meldrum’s acid yielded corresponding benzo[a]chromeno[2,3-c]phenazine derivatives. Crystal structure of 3k established the regioisomer formed. Mild reaction conditions, good yields, short reaction time, and easy separation are some of the salient features of the present protocol.     

Synthesis and binding investigations of novel crown-ether derivatives of phenanthro[4,5-abc]phenazine and quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine

The synthesis and binding investigation of novel crown-ether derivatives of phenanthro[4,5-abc]phenazine and quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine sensors are reported. The binding studies of these sensors with an array of alkali and alkaline-earth metals are exploited using UV–vis, fluorescence and nuclear magnetic resonance spectroscopies.