Papers by Yusuf Al-Najjar
Journal of Fungi
Sweet pepper (Capsicum annuum L.), also known as bell pepper, is one of the most widely grown veg... more Sweet pepper (Capsicum annuum L.), also known as bell pepper, is one of the most widely grown vegetable crops worldwide. It is attacked by numerous phytopathogenic fungi, such as Fusarium equiseti, the causal agent of Fusarium wilt disease. In the current study, we proposed two benzimidazole derivatives, including 2-(2-hydroxyphenyl)-1-H benzimidazole (HPBI) and its aluminum complex (Al−HPBI complex), as potential control alternatives to F. equiseti. Our findings showed that both compounds demonstrated dose-dependent antifungal activity against F. equiseti in vitro and significantly suppressed disease development in pepper plants under greenhouse conditions. According to in silico analysis, the F. equiseti genome possesses a predicted Sterol 24-C-methyltransferase (FeEGR6) protein that shares a high degree of homology with EGR6 from F. oxysporum (FoEGR6). It is worth mentioning that molecular docking analysis confirmed that both compounds can interact with FeEGR6 from F. equiseti as...
Applied Organometallic Chemistry
A new set of Ag(I), In (III) and Sn (II) chelates based on azo dye ligand of 5-aminosalicylic aci... more A new set of Ag(I), In (III) and Sn (II) chelates based on azo dye ligand of 5-aminosalicylic acid (H2L) were prepared. The structures of this novel chelates have already been confirmed by elemental analysis, thermo-gravimetric analysis, molar conductance, X-ray diffraction (XRD), UV–Vis, Fourier-transform infrared spectroscopy (FT-IR), and mass spectra. The lower conductivity values showed the non-electrolytic nature. The kinetic and thermodynamic parameters were determined through using Coats–Redfern model, also, potential application; the antibacterial activity of the target compounds was tested by examining their effect on the development of various strains of bacteria. Utilizing UV–visible absorption measurements, we investigated the interaction between calf thymus DNA and the evaluated compounds. According to the findings, the intercalative binding approach, the chelates interact with DNA by assessing the binding constants. Additionally, the in vitro antimicrobial properties of the ligand and its metal chelates were evaluated. The theoretical density functional theory (DFT) simulations for the azo dye ligand (H2L) were completed by using B3LYP/6-311G++ (d,p) basis functions, and the B3LYP/LanL2DZ for Ag(I), In (III), and Sn (II) chelates shows that the uninuclear Ag(I) and Sn(II) chelates under consideration have a tetrahedral geometry. Although the experimental data are in agreement with the octahedral shape for binuclear In (III) chelate. Molecular docking simulations were carried out using molecular operating environment (MOE) software for the ligand and its chelates. Docking simulation results indicated that the Ag(I) chelate was more potent and exhibited a higher affinity for the (3QKK) protein than the In (III) and Sn (II) chelates. This is in agreements with the biological evaluations under studies.
Plants, Sep 16, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Applied Organometallic Chemistry
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2005
The electronic absorption spectra of 1-(4,6-dimethyl-pyrimidin-2-ylazo)-naphthalen-2-ol is studie... more The electronic absorption spectra of 1-(4,6-dimethyl-pyrimidin-2-ylazo)-naphthalen-2-ol is studied in organic solvents of different polarity as well as in buffer solutions of varying pH values at different temperatures and different ratios of methanol. The probable structure of the azodye has been assigned on the basis of spectral studies (IR and (1)H NMR). The effect of Co(II), Ni(II) and Cu(II) ions on the emission spectrum of the free azodye is also assigned. The stoichiometry of the metal complexes is determined spectrophotometrically and conductometrically. Novel complexes of Co(II), Ni(II) and Cu(II) with the pyrimidine azodye have been synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic as well as ESR spectral studies The thermal decomposition of the metal complexes is studied by TGA and DTA techniques. The kinetic parameters like activation energy, pre-exponential factor and entropy of activation are estimated.
Quenching the fluorescence of the dyes 3-(4’-dimethylaminophenyl)-1-(1H-pyrrol-2-yl)prop-2-en-1-o... more Quenching the fluorescence of the dyes 3-(4’-dimethylaminophenyl)-1-(1H-pyrrol-2-yl)prop-2-en-1-one (DMAPrP), 3-(4’-dimethylaminophenyl)-1-(2-furanyl)prop-2-en-1-one (DMAFP) and 3-(4’-dimethylaminophenyl)-1-(2-thienyl)prop-2-en-1-one (DMATP) has been investigated in the presence of silver cation and silver nanoparticles in different media. The results of the quenching experiments were analyzed using Stern-Volmer equation. Quenching the fluorescence of the dyes decreased with increasing medium viscosity. The Stern-Volmer constant (KSV) values in the absence and pres-ence of ethylene glycol show that the quenching efficiencies decrease as the medium viscosity increases indicating that the quenching process is a diffusion-controlled process, and this is consistent with a dynamic-type quenching.
Applied Organometallic Chemistry
Journal of Molecular Structure
Abstract Three novel chelates, [Ru(L)3]2H2O, C1, [NiL(H2O)3(AcO)]H2O, C2, and [CuL(H2O)(AcO)], C3... more Abstract Three novel chelates, [Ru(L)3]2H2O, C1, [NiL(H2O)3(AcO)]H2O, C2, and [CuL(H2O)(AcO)], C3, derived from 2-(2-hydroxy phenyl)-1-H –benzimidazole) HL, have been designed. The structures of the isolated compounds have been elucidated by elemental analysis, molar conductance, thermal analysis, spectral data (UV–Vis, mass spectra, IR, fluorescence), thermal analysis (TGA) and magnetic moment measurements. The IR spectral data ascertained that the HL compound acts as a monobasic bidentate ligand via the O and N atoms of the OH and C=N groups of the benzimidazole moiety, respectively. The spectral and magnetic measurements implied octahedral structures for C1 and C2 and square planar geometry for C3. The kinetic and thermodynamic parameters of the thermal decomposition stages have been evaluated. Molecular orbital calculations have been performed. The metallochromic behavior of the investigated free ligand was studied in the presence of Ru(III), Ni(II) and Cu(II) ions. The observed spectral changes indicated the ability of HL to act as potential optical sensor for probing these metal ions. Interaction of the investigated compounds with CT-DNA was studied via electronic absorption and emission spectroscopy, as well as ethidium bromide displacement. The results suggested that all compounds interact through intercalative mode. The binding behavior and binding constants have been evaluated and discussed. The CT-DNA-binding constants confirmed the strong intercalation between the investigated ligand and metal complexes with the CT-DNA, suggesting that the investigated compounds can be used as promising therapeutic drug. Finally, the antimicrobial activities of the metal complexes have been screened.
Applied Organometallic Chemistry
Journal of Molecular Structure
Journal of Molecular Structure
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
Journal of Luminescence, 2015
ABSTRACT Cadmium selenide (CdSe) quantum dots (QDs) were synthesized with a cubic shape having a ... more ABSTRACT Cadmium selenide (CdSe) quantum dots (QDs) were synthesized with a cubic shape having a diameter of ~5.24 nm. The prepared CdSe QDs were characterized by using UV-visible, Fourier transform infrared (FTIR), powder X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The UV-visible absorption spectra indicate that the optical band gap of CdSe QDs is ~622 nm and the peak shift can mainly be due to the quantum size effects. The fluorescence decay kinetics for the synthesized QDs was followed by time-resolved fluorescence spectroscopy, and the spectra were analyzed in regard to a bi-exponential model to identify two lifetime values, that is, shorter-lifetime 1.37 ns (55%) and longer-lifetime 6.58 ns (45%). The interaction of coumarin 152 (C152) and coumarin 153 (C153) with QDs surface brings about further considerable changes in the absorption and fluorescence patterns. The calculated binding constant from fluorescence quenching method matches well with that determined from the absorption spectral changes. The static quenching mechanism was confirmed by large magnitude of KSV and unaltered fluorescence lifetime.
Advances in Nanoparticles, 2012
Quenching the fluorescence of the dyes 3-(4 '-dimethylaminophenyl)-1-(1H-pyrrol-2-yl)prop-2-en-1-... more Quenching the fluorescence of the dyes 3-(4 '-dimethylaminophenyl)-1-(1H-pyrrol-2-yl)prop-2-en-1-one (DMAPrP), 3-(4 '-dimethylaminophenyl)-1-(2-furanyl)prop-2-en-1-one (DMAFP) and 3-(4 '-dimethylaminophenyl)-1-(2-thienyl)prop-2-en-1-one (DMATP) has been investigated in the presence of silver cation and silver nanoparticles in different media. The results of the quenching experiments were analyzed using Stern-Volmer equation. Quenching the fluorescence of the dyes decreased with increasing medium viscosity. The Stern-Volmer constant (K SV) values in the absence and presence of ethylene glycol show that the quenching efficiencies decrease as the medium viscosity increases indicating that the quenching process is a diffusion-controlled process, and this is consistent with a dynamic-type quenching.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2008
4-(1H-Pyrazolo (3,4-d) pyrimidin-4-ylazo) benzene-1,3-diol was synthesized and characterized by v... more 4-(1H-Pyrazolo (3,4-d) pyrimidin-4-ylazo) benzene-1,3-diol was synthesized and characterized by various spectral and analytical techniques. Semiempirical quantum calculations using the AM1 method have been performed in order to evaluate the geometry and electronic structure of the title azodye in the ground state. The complex formation between Co(II), Ni(II) and Cu(II) ions and the title azodye was studied conductometrically and spectrophotometrically. The spectrophotometric determination of the title metal ions and titration using EDTA are reported. Co(II), Ni(II) and Cu(II) complexes of the title azodye have been synthesized and characterized by elemental analysis, conductivity, magnetic susceptibility, IR, UV-Vis and thermal analysis (TGA and DTA).The spectral and magnetic data suggested the octahedral geometry for Co(II) and Ni(II) complexes while Cu(II) complexes have square planar geometry. The thermal studies confirmed the chemical formulations of the title complexes. The thermal degradation takes place in two or three steps depending on the type of the metal and the geometry of the complexes. The kinetics of the decomposition was examined by using Coats-Redfern relation. The activation energies and other activation parameters (DeltaH, DeltaS and DeltaG) were computed and related to the bonding and stereochemistry of the complexes.
Photochemical & Photobiological Sciences, 2008
The absorption and fluorescence emission spectral properties of 3-(4'-dimethylaminophenyl... more The absorption and fluorescence emission spectral properties of 3-(4'-dimethylaminophenyl)-1-(2-thienyl)prop-2-en-1-one, abbreviated as DMATP, have been investigated in organized media of aqueous micellar and beta-cyclodextrin (CD) solutions. While the absorption spectra are less sensitive to the nature of the added surfactant or CD, the characteristics of the intramolecular charge transfer (ICT) fluorescence are highly sensitive to the properties of the medium. The ICT maximum is strongly blue-shifted with a great enhancement in the fluorescence quantum yield on adding micellar or CD solutions. This indicates the solubilization of DMATP in the micellar core and formation of an inclusion complex with beta-CD. The critical micelle concentration (CMC) as well as the polarity of the micellar core of SDS, CTAB and TX-100 have been determined. The CMC values are in good agreement with the reported values while the polarity is lower indicating that DMATP molecules are incorporated in the micellar core not at the micellar interface. The inclusion constants of binding of DMATP in micellar or CD have been also determined. The thermodynamic parameters of formation of DMATP:CD inclusion complex have been calculated from the temperature dependence of the fluorescence spectra of the formed complex. The negative enthalpy and free energy of formation indicate that the inclusion process is energetically favorable. The highly negative value of formation entropy (DeltaS = -162.3 J mol(-1) K(-1)) reflects the high restrictions imposed on the movement of both the host and included guest molecules which is consistent with the increase of the fluorescence yield and blue shift of the fluorescence maximum.
Optics & Laser Technology, 2009
The spectral properties such as singlet absorption, molar absorptivity, emission spectra, fluores... more The spectral properties such as singlet absorption, molar absorptivity, emission spectra, fluorescence quantum yield and excited state lifetime of 3-(4 0-dimethylaminophenyl)-1-(2-furanyl)prop-2-en-1-one (DMAFP) have been determined in different solvents. DMAFP dye exhibits a large red shift in both electronic absorption and emission spectra as the solvent polarity increases, indicating a large change in the dipole moment of molecules upon excitation. A crystalline solid of DMAFP gives an excimer like emission at 566 nm due to the excitation of molecular aggregates. This is expected from the idealized crystal structure of the dye that belongs to the B-type class of Steven's classification. The ground and excited state protonation constants of DMAFP are calculated and amounted to 1.71 and 8.3, respectively. DMAFP acts as a good laser dye upon pumping with nitrogen laser (l ex ¼ 337.1 nm) in chloroform, methylene chloride and dioxane and gives laser emission in the range 460-590 nm. The laser parameters such as the tuning range, gain coefficient (a), emission cross section (s e) and half-life energy (E 1/2) are calculated. The photoreactivity and net photochemical quantum yield of DMAFP in chloromethane solvents are also studied.
Optics & Laser Technology, 2013
In this study, we prepared a new chalcone compound (3-(4 0-diethylaminophenyl)-1-(2-pyridinyl) pr... more In this study, we prepared a new chalcone compound (3-(4 0-diethylaminophenyl)-1-(2-pyridinyl) prop-2en-1-one abbreviated as DEAPPP) and examined its characterization and photophysical properties such as singlet absorption, molar absorptivity, fluorescence spectra, and fluorescence quantum yield (f f). DEAPPP dye exhibited a large red shift in both absorption and emission spectra as solvent polarity increases, indicating a large change in dipole moment of molecule upon excitation. Also, the fluorescence quantum yield was solvent dependent. The absorption and fluorescence emission spectral properties of DEAPPP have been investigated in organized media of aqueous micellar and b-cyclodextrin (CD) solutions. While the absorption spectra were less sensitive to the nature of the added surfactant or CD, the characteristics of the intramolecular charge transfer (ICT) fluorescence were highly sensitive to the properties of the medium. The ICT maximum was strongly blue-shifted with a great enhancement in the fluorescence quantum yield on adding micellar or CD. This indicated that the solubilization of DEAPPP increased in the micellar core and an inclusion complex with b-CD was formed. The critical micelle concentration (CMC) as well as the polarity of the micellar core of sodium dodecyl sulfate (SDS), Cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) have been determined. The CMC values were in good agreement with the reported values while the polarity was lower indicating that DEAPPP molecules were incorporated in the micellar core not at the micellar interface. The binding constants of DEAPPP: micelles or DEAPPP: CD complexes have been also determined.
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Papers by Yusuf Al-Najjar