Visible light-induced synthesis of biomass-derived quinoxaline by using Co phthalocyanine immobilized on pyridine-doped g-C_(3)N_(4)

Visible light-driven valorization of biomass has recently been a pioneering field for nitrogen-containing heterocyclics syntheses due to its sustainable features.Herein,various aromatic ring-doped g-C_(3)N_(4) nanosheets(Ar-g-C_(3)N_(4);Ar=Py,Pm,Ph)were precisely designed to modulate their intrinsic electronic and band structure,which involves pyridine(Py),pyrimidine(Pm),and benzene(Ph)-doped g-C_(3)N_(4).Photocatalysts(CoPc/Ar-g-C_(3)N_(4)) of cobalt(II)phthalocyanine(CoPc)-fabricated Ar-g-C_(3)N_(4) were then developed for oxidative cyclization of furoin with 1,2-phenylenediamines for syntheses of various biomass-derived quinoxalines under visible-light irradiation.The catalytic activity(in terms of TOFs)of serial CoPc/Ar-g-C_(3)N_(4) samples increased with their transient photocurrents with CoPc/Py-g-C_(3)N_(4) as the most active one.For CoPc/Py-g-C_(3)N_(4),CoPc species functioned as both sensitizer and catalytic sites;while,doped Py led to a narrowed bandgap energy.Mechanism research further demonstrated that O_(2) was activated to superoxide radical(·O_(2)^(-)) by photoexcited high-level-energy electron(HLEE)transfer from Py-g-C_(3)N_(4) to CoPc for the subsequent aerobic oxidation.

Aspects on the Mechanism of the 1-Phenyl-1<i>H</i>-pyrazolo[3,4-<i>b</i>]quinoxaline Formation

Condensation of D-glucose, o-phenylenediamine and N,N-benzylphenylhydrazine hydrochloride (NNBPHH) in a one-pot reaction, or condensation of 2-(D-arabino-tetritol-1-yl) quinoxaline and NNBPHH, gave 3-(D-erythro-glycerol-1- yl)-1-phenyl-1H-pyrazolo[3,4-b]quinoxaline. The structure of the latter was determined by 1H NMR spectroscopy and by synthesis using phenylhydrazine hydrochloride instead of NNBPHH. Condensation of D-glucose and 4,5-dichloro-o-phenylenediamine gave 6,7-dichloro-2-(D-arabino-tetritol-1-yl)quinoxaline, which upon condensation with NNBPHH gave the corresponding 6,7-dichloro-3-(D-erythro-glycerol-1-yl)-1-phenyl-1H-pyrazolo[3,4-b]quinoxaline. The structure and mechanism of formation of these compounds are discussed.

Hydrothermal Syntheses and Crystal Structures of Two Metal-organic Complexes with 2,3-Pyridinedicarboxylic Acid and 2-Methyl-dipyrido[3,2-f:2',3'-h]quinoxaline Ligands

Two unusual one-dimensional（1-D） compounds,viz.[Co（Medpq）（QUI）·H2O]2n· 2.4nH2O 1 and [Cd（Medpq）（QUI）·H2O]n·nH2O 2,were synthesized by the combination of two different metallic salts and organic ligands,namely 2,3-pyridinedicarboxylic acid（H2QUI） and 2-methyldipyrido[3,2-f：2＇,3＇-h]quinoxaline（Medpq） ligand.The compounds were characterized by elemental analyses,TG,fluorescent emission and single-crystal X-ray diffraction analyses.

Combined electronic/atomic level computational, surface(SEM/EDS),chemical and electrochemical studies of the mild steel surface by quinoxalines derivatives anti-corrosion properties in 1 mol·L^(-1) HCl solution

This work is devoted to the study of the inhibition of corrosion of mild steel(MS)in molar hydrochloric acid(1 mol·L-1 HCl)by two named quinoxaline derivatives namely,2-(2,4-dichlorophenyl)-1,4-dihydroquinoxaline(HQ)and 2-(2,4-dichlorophenyl)-6-methyl-1,4-dihydroquinoxaline(CQ).The inhibitory efficacy of HQ and CQ compounds is first evaluated using the gravimetric method and using electrochemical techniques(stationary and transient techniques).The results showed that our compounds are efficient corrosion inhibitors and the inhibition rates(ηEIS%)reached up to 91%and 94.2%at 10-3 mol·L-1 for HQ and CQ,respectively.The mentioned molecules are classified as mixed-type inhibitors.The adsorption of these inhibitors on the surface of steel in hydrochloric HCl 1 mol·L-1 medium obeys the Langmuir adsorption isotherm.The results of the scanning electron microscope(SEM)showed the formation of a protective film on the surface of the steel in the presence of the inhibitors studied.Elementary analysis is obtained by energy dispersive X-ray spectroscopy(EDS).The inhibition property was further elucidated by theoretical approaches such as:Density Functional Theory(DFT),quantum chemical descriptors(QCD),local reactive indices,solvent effect,theoretical complexation,Molecular Dynamic(MD)simulation,effect of temperature on adsorption energy(Eads),Radial Distribution Function(RDF),and Mean Square Displacement(MSD).The results of these approaches support the experimental results.

Ga(ClO_4)_3-catalyzed Reaction of 1,2-Diamines and α-Bromoketones:Synthesis of 2-Substituted Quinoxalines

Ga（ClO4）3-catalyzed reaction of 1,2-aryldiamines and α-bromoketones to afford 2-substituted quinoxalines in good yields is described.The reaction proceeded via grinding process with 10%（molar fraction） catalyst under solvent-free conditions at room temperature.For unsymmetrical o-phenylenediamines bearing electron-withdrawing groups,regio-selective quinoxalines were obtained.

Potential benefits of quinoxaline 1, 4-dioxides in aldosterone dysmetabolism disease—A medical hypothesis

Quinoxaline 1, 4-dioxides (QdNOs) are quinox-aline derivatives which have been used as an-timicrobial agents and growth promoters in animals widely. They are also assumed to cure human disease such as anticancer, antitubercular and inhibiting parasite. QdNOs such as carbadox and their major metabolites induced a special decline of aldosterone production from the swine adrenal in vivo and in vitro, and thus cause hypovolemia, hyponatremia and hyperkalemia. This can also be expected to be the case for human. As a mainly physiological hormone and a novel steroid with potent mineralocorticoid activity, aldosterone plays an important role in the pathophysiological process of brain, renal and heart disease progression and may be a renal and vascular risk factor. Here, we provide evidence to support the hypothesis that QdNOs may lead potential benefits in aldosterone dysmetabolism disease via the synthesis deficiency of aldosterone in adrenal and/or the cardiovascular tissues. If the hypothesis is true, it may provide a new option into the therapy for aldosterone dysmetabolism disease, especially in cardiovascular system, and thus assume a broader application of QdNOs.

Hydrothermal Reaction, Structure and Magnetic Properties of a Binuclear Cobalt Complex with N-donor Ligand:2-Methyldipyrido[3,2-f:2ˊ3ˊ-h]quinoxaline

One complex [Co1.5（C6H5CHCHCOO）3（Medpq）]·H2O（C6H5CHCHCOO = cinnamic acid, Medpq = 2-methyldipyrido[3,2-f：2,3-h]quinoxaline） 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG, single-crystal X-ray diffraction and magnetic susceptibility measurements. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.224（5）, b = 14.572（5）, c = 15.139（5）A, α = 112.704（5）, β = 97.168（5）, γ = 109.749（5）, V = 1871.8（13） 3 and Z = 2（at 293（2） K）. In the crystal structure, the Co（1） ion is hexa-coordinated with six atoms from three different cinnamic acid ligands and the symmetric three different cinnamic acid ligands; the Co（2） center adopts a coordination environment with two nitrogen atoms from Medpq ligand and four oxygen atoms from two different cinnamic ligands, assuming a slightly distorted octahedral geometry, respectively. The negative value of the Weiss constant indicates antiferromagnetic exchange interactions between the Co ions.

Coordination Modes of Polypyridyl Quinoxaline with Hg(Ⅱ),Pb(Ⅱ),Co(Ⅱ)and Mn(Ⅱ)

The interaction of metal ions（Hg^2＋,Pb^2＋,Co^2＋,Mn^2＋） with polypyridyl quinoxaline ligand 2,3,6,7,10,11-hexakis（2-pyridyl）dipyrazino[2,3-f：20,30-h]quinoxaline（HPDQ） was investigated,and four new complexes have been synthesized and characterized.Complex 1 exhibits a 0dimensional dual-core structure,2 is a one-dimensional chain structure based on a dual-core Pb unit,while 3 and 4 show a 0 dimensional single-core structural unit.Complex 1 is of monoclinic system,space group C2/c with a = 19.211（4）,b = 23.896（5）,c = 12.698（3） A°,β= 120.11（3）°,V= 5043.0（17）A°3,Z = 4,S = 1.053,F（000） = 2976,R^a = 0.0637 and wR^b = 0.1068（I 〉 2σ（I））.Complex 2 adopts triclinic system,space group P1 with a = 10.370（2）,b = 12.195（2）,c = 21.033（4） A°,α = 80.87（3）,β= 81.22（3）,γ = 82.38（3）°,V= 2579.3（8） A°3,Z = 2,S = 1.099,F（000） = 1328,R^a = 0.0609 and wR^b =0.1365（I 〉 2σ（I））.Complex 3 is of monoclinic system,space group Cllc with a = 14.166（3）,b =16.621（3）,c = 20.248（4） ？,β = 92.18（3）°,V= 4764.0（16） A°3,Z = 4,S = 1.005,F（000） = 2108,R^a =0.0589 and wR^b = 0.1332（I 〉 2σ（I））.Complex 4 belongs to the monoclinic system,space group C2/c with a = 14.404（3）,b = 16.626（3）,c = 20.346（4） ？,β = 92.43（3）°,V= 4868.2（17） A°3,Z = 4,S= 1.068,F（000） = 2108,R^a = 0.0833 and wR^b = 0.1591（I 〉 2σ（I））.Furthermore,the behavior of HPDQ with Hg^2＋,Pb^2＋,Co^2＋ and Mn^2＋ in the solution was also investigated,and the result shows after the metal ions were added respectively,the emission of all solutions shows fluorescence quenching and has a red shift compared with that of the HPDQ ligand.

SYNTHESIS AND CHARACTERIZATION OF ORGANOSOLUBLE POLYAMIDES FROM QUINOXALINE BASED DIAMINE

Aromatic/aliphatic polyamides were synthesized from a diamine monomer, 2,3-bis-p-aminophenylquinoxaline （IV）, based on quinoxaline and various dicarboxylic acids of aliphatic, aromatic and heterocyclic. The diamine and polyamides were characterized by elemental analysis, FTIR and IH-NMR. The solubility of the polyamides was affected by the quinoxaline and heterocyclic groups in the polymer chain. They were all soluble in common organic solvents such as dimethylsulfoxide （DMSO）, N,N-dimethylformamide （DMF） and N-methylpyrolidone （NMP）. The polyamides showed inherent viscosity in the range of 0.25-0.3 dL/g in DMSO at 25℃ and good thermal stability with the char yields in the range of 65%-82% at 600℃ in nitrogen.

Convenient Synthesis of Substituted Quinoxalines and 2H-Benzo[b][1,4]oxazines in Water

A facile and convenient synthesis method has been developed for substituted quinoxalines and 2H-benzo[b][1,4]oxazines from the reactions of a-bromoketones with benzene-1,2-diamine and 2-aminophenol, respectively, which were catalyzed by tetrabutylammonium bromide（TBAB） in aqueous basic media.

Structures and Spectroscopic Properties of(1)Dipyridine Quinoxaline with Hg(Ⅱ), Cu(Ⅰ) and Ag(Ⅰ)

The interaction of Hg（Ⅱ）, Cu（Ⅰ） and Ag（Ⅰ） with dipyridine quinoxaline ligand 2,3-bis（2-pyridyl）quinoxaline（DPQ） were investigated, and three new complexes have been synthesized and characterized. Complex 1 exhibits a 0D dual-core structure, complex 2 is a 0D tetra nuclear case based on a dual-core Cu unit, and complex 3 shows a one-dimensional pipeline structure. Furthermore, the optical properties of complex and DPQ were also investigated, and the results showed that the fluorescence intensity of complexes was weaker than that of ligand DPQ.

Synthesis, Characterization, Anti-Bacterial and Anti-Fungal Activities of New Quinoxaline 1,4-di-N-Oxide Derivatives

A new series of quinoxaline 1,4-di-N-oxides were synthesized and evaluated for their antibacterial and antifungal activities. The best result was demonstrated by 3-amino-N-(4-methoxyphenyl)-2-quinoxalinecarboxamide 1,4-di-N-oxide 4e, MIC (0.24 μg/ml) against Aspergillus fumigatus, and (0.12 μg/ml) against Streptococcus pneumonia.

Molecular and electronic structure of several 2,3-dithienylquinoxalines and their 2:1 complexes with silver(I) nitrate

We have synthesized three bis (thienyl) quinoxalinesilver(I) complexes;however, unlike analogous silver(I) complexes of pyridylquinoxaline that utilize (N, N) bidentate behavior from the quinoxaline and pyridyl ring nitrogens, the bis(thienyl) quinoxaline ligands did not utilize the bonding potential of the thienyl rings to give (N, S) bonding modes. PES spectra modeling of these ligands indicates that the preferential metal bonding via only the quinoxaline nitrogen atoms is due to the N-rich, but S-poor, characters of the frontier orbitals.

Crystal Structure and Spectroscopic Analysis of Polyphenyl Quinoxaline with Hg(Ⅱ)

The interaction of Hg^2＋ with polyphenyl quinoxaline ligand 2,3,6,7,10,11-hexaphenyldipyrazino[2,3-f：2＇,3＇-h]quinoxaline（HPQ） was investigated, and a new complex（C（49）H（32）N6Br2Cl2Hg） has been synthesized and characterized. It exhibits a 0D single-core structure,and adopts triclinic P 1 space group with a = 11.139（2）, b = 13.429（3）, c = 14.488（3）A, α =76.10（3）, β = 83.16（3）, γ = 87.36（3）o, V = 2088.4（7） A^3, Z = 2, S = 1.056, F（000） = 1104, R = 0.0417 and w R = 0.0931（I 〉 2σ（I））. Furthermore, the behavior of HPQ with Hg^2＋ in the solution was also investigated, and the result shows that HPQ was found to have excellent fluorescent selectivity for Hg^2＋ over many other metal ions（Li^＋, K^＋, Na^＋, Sr^＋, Ca^2＋, Mg^2＋, Mn^2＋, Fe^3＋, Ni^2＋, Co^2＋, Cu^2＋, Zn^2＋,Cd^2＋, Pb^2＋, Al^3＋ and Cr^3＋） based on the intermolecular charge-transfer mechanism, which makes HPQ a potential fluorescence sensor or probe for Hg^2＋.

Crystal Structure and Spectroscopic Analysis of Polypyridyl Quinoxaline with Ce(Ⅲ) and Nd(Ⅲ)

Two high coordination crystals were obtained by the interaction of Ce^（3＋） and Nd^（3＋） with polypyridyl quinoxaline ligand 2,3,6,7,10,11-hexakis（2-pyridyl）dipyrazino[2,3-f：20,30-h]quinoxaline（HPDQ）, and they were characterized. Complex 1 exhibits a 0 dimensional three-nuclear structure, with the three Ce（Ⅲ） atoms being ten-, eleven- and twelve-coordinated. Complex 2 is a 0 dimensional dual-core structure and the Nd（Ⅲ） atom is ten-coordinated. Complex 1 is of monoclinic system, space group P2/c with a = 16.850（3）, b = 16.617（3）, c = 24.017（5） ？, β = 100.94（3）o, V = 6602（2） ？~3, Z = 4, S = 1.062, F（000） = 3372, R = 0.0504 and wR = 0.1463（I 〉 2σ（I））. Complex 2 adopts a monoclinic system, space group C2/c with a = 25.795（5）, b = 20.166（4）, c = 13.059（3） ？, β = 112.29（3）°, V = 6286（2） ？~3, Z = 4, S = 1.004, F（000） = 2664, R = 0.0663 and wR = 0.1821（I 〉 2σ（I））. Furthermore, the behaviors of HPDQ with Ce^（3＋） and Nd^（3＋） in the solution are also investigated. After the Ce^（3＋） is added, the ultraviolet absorption of the solution is enhanced with a red shift compared with that of the HPDQ ligand. While after adding Nd^（3＋）, the ultraviolet absorption of the solution is weakened, and it has a red shift which is the same as Ce^（3＋）. However, after the respective addition of metal ions, the emission of all solutions is quenched and has a red shift compared with that of the HPDQ ligand.

Quinoxaline-specific enantioselective sulfa-michael reaction catalyzed by chiral phosphoric acid

Highly enantioselective sulfa-Michael additions(SMA)between 2-alkenyl quinoxalines and aromatic thiols are accomplished using a low loading of chiral phosphoric acid catalyst(1 mol%).It was confirmed by an investigation of a lot of azaarenes that the two C-N units of quinoxalines are indispensable for controlling the reaction enantioselectivities.A series of non-terminal 2-alkenes substituted with aryls or alkyls,even other electro-withdrawing groups such as ketones,esters,or amides,selectively reacted and afforded the desired SMA products(48 examples)in good regioselectivities with high yields(up to 99%)and good ee values(up to 97%).

Halogenated thiophene substitutions on quinoxaline unit to achieve morphology optimization in efficient organic solar cells

Halogenated thiophenes are generally used units for constructing organic semiconductor materials for photovoltaic applications.Here,we introduced thiophene,2-bromothiophene,and 2-chlorothiophene units to the central core of quinoxaline-based acceptors and obtained three acceptors,Qx-H,Qx-Br,and Qx-Cl,respectively.Compared with Qx-H,Qx-Br and Qx-Cl showed enhanced absorption,down-shifted energy levels,improved crystallinity,and reduced energy disorder.The improved crystallinity significantly optimized the blend morphology,leading to efficient charge generation and transport and,therefore,less bimolecular recombination.Eventually,PM6:Qx-Br-based devices exhibited an outstanding power conversion efficiency of 17.42%with a high open-circuit voltage(VOC)of 0.915 V.Furthermore,Y6 was introduced into the PM6:Qx-Br binary system to improve the light utilization,and the resulting ternary devices delivered a high PCE of 18.36%.This study demonstrated the great potential of halogenated thiophene substitution in quinoxaline-based acceptors for building high-performance organic solar cell acceptor materials.

New Quinoxaline-Based Blue Emitters: Molecular Structures, Aggregation-Induced Enhanced Emission Characteristics and OLED Application

Three new deep blue light emitters,bearing quinoxaline with different substituents(biphenyl/pyrene)at the 1-or 2-position,were synthesized by a Pd-catalysed coupling reaction in high yields,and were fully characterized by 1H/13C NMR spectroscopy,single crystal X-ray diffraction,and high-resolution mass spectrometry(HRMS).

6,7-DIALKOXY-2,3-DIPHENYLQUINOXALINE BASED CONJUGATED POLYMERS FOR SOLAR CELLS WITH HIGH OPEN-CIRCUIT VOLTAGE

6,7-Dialkoxy-2,3-diphenylquinoxaline based narrow band gap conjugated polymers, poly[2,7-（9-octyl-9H- carbazole）-alt-5,5-（5,8-di-2-thinenyl-（6,7-dialkoxy-2,3-diphenylquinoxaline））] （PCDTQ） and poly[2,7-（9,9-dioctylfluorene）- alt-5,5-（5,8-di-2-thinenyl-（6,7-dialkoxy-2,3-diphenylquinoxaline））] （PFDTQ）, have been synthesized by Suzuki polycondensation. Their optical, electrochemical, transport and photovoltaic properties have been investigated in detail. Hole mobilities of PCDTQ and PFDTQ films spin coated from 1,2-dichlorobenzene （DCB） solutions are 1.0 X 10-4 and 4.1 X 10-4 cm2 V-1 s-l, respectively. Polymer solar cells were fabricated with the as-synthesized polymers as the donor and PC61BM and PC7 IBM as the acceptor. Devices based on PCDTQ：PC71BM （1：3） and PFDTQ：PC7 IBM （1：3） fabricated from DCB solutions demonstrated a power conversion efficiency （PCE） of 2.5% with a Voc of 0.95 V and a PCE of 2.5% with a Voof 0.98 V, respectively, indicating they are promising donor materials.