• Neeraj

      Articles written in Journal of Chemical Sciences

    • Mesoporous alumina

      Neeraj M Eswaramoorthy

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      Alumina with a fairly large surface area (415 m2g−1) and narrow pore size distribution (pore diameter ∼3 nm), containing octahedral and tetrahedral aluminum, prepared by long chain neutral amine as the surfactant, shows some evidence of textured structure. This material also contains disordered hexagonal structures, but use of partially hydrolyzed aluminum alkoxide with short chain amine templates, results in amorphous alumina with a surface area of 340m2g−1. Use of a polyethylene oxide as the surfactant, did not give the mesoporous structure in the absence of the template.

    • Synthesis of a 4-membered ring zinc phosphate monomer and its condensation self-assembly into an open-framework structure

      S Neeraj Srinivasan Natarajan C N R Rao

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    • Synthesis and characterization of submicron-sized mesoporous aluminosilicate spheres

      Gautam Gundiah M Eswaramoorthy S Neeraj Srinivasan Natarajan C N R Rao

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      Mesoporous aluminosilicate spheres of 0.3–0.4 Μm diameter, with different Si/Al ratios, have been prepared by surfactant templating. Surface area of these materials is in the 510–970 m2 g-1 range and pore diameter in the 15–20 å range.

    • Synthesis and characterization of di- and triorganotin(IV) complexes of 2-tert-butyl-4-methyl phenol

      Neeraj Sharma Archana Maridula Thakur S S Bhatt S C Chaudhry

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      The di- and trialkyltin(IV) complexes of composition R2SnCl$_{2-x}$(OAr), and 𝑛-Bu3Sn(OAr) (R = 𝑛-Bu and Me; 𝑥 = 1 and 2; OAr = OC6H3Bu$^t$-2-Me-4) have been synthesized by the reactions of di-n-butyl and dimethyltin dichlorides and tri-n-butyltin(IV) chloride with 2-tert-butyl-4-methylphenol and triethylamine in tetrahydrofuran. The reaction of triphenyltin chloride with trimethylsilyl-2-t-butyl-4-methylphenoxide in the same solvent however, gives a complex of composition Ph3Sn(OAr). The complexes have been characterized by microanalyses, molar conductance measurements, molecular weight determinations and IR and 1H, 13C and 119Sn NMR and mass spectral studies. Thermal behaviour of the complexes has been studied by TGA and DTA techniques. From the non-isothermal TG data, the kinetic and thermodynamic parameters have been calculated employing Coats-Redfern equation and the mechanism of decomposition has been computed using non-isothermal kinetic method. Thermal investigations on the blends of poly(methylmethacrylate). PMMA, with organotin(IV)-2-tert-butyl-4-methylphenoxides have shown increased thermal stability compared to pure PMMA suggesting thereby their potential as additives towards PMMA.

    • Synthesis, photoluminescence and electrochemical properties of 2,7-diarylfluorene derivatives

      Neeraj Agarwal Pabitra K Nayak N Periasamy

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      A new class of highly fluorescent 9,9'-bis-(alkyl)-2,7-diarylfluorene having electron withdrawing or electron donating groups on the 𝑝-phenyl positions were synthesized and characterized. The highly luminescent fluorene derivatives, 1-6 showed blue emission (376-416 nm), narrow FWHM (∼ 50 nm), high quantum yield ($\phi_{\text{F}} = 0.12-0.87$) and short fluorescence lifetimes, $\tau_{\text{F}} = 0.23-1.14$ ns. The HOMO levels of 9,9'-bis-(alkyl)-fluorene were tuned by the p-substituents at 2,7-phenyl group. Hammett correlation with $E_{\text{HOMO}}$ of these new molecules provides an effective tool to predict the HOMO level of similar molecules prior to the synthesis. These data indicate that they are useful as emitting materials for organic light emitting devices, OLEDs.

    • Synthesis, photophysical and electrochemical properties of 2,8-diaryl-dibenzothiophene derivatives for organic electronics

      Pabitra K Nayak Neeraj Agarwal N Periasamy

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      A series of 2,8-𝑝-diaryldibenzothiophene derivatives were synthesized and characterized. These molecules have electron withdrawing or electron donating groups at the para phenyl position, which alters the electronic properties of these derivatives. The quantum yield, fluorescence lifetime, singlet, triplet and EHOMO energy levels of these compounds were determined by fluorescence, phosphorescence and cyclic voltammetry. A plot of Hammett constants of the para substituents vs EHOMO revealed a linear relationship. The usefulness of these molecules in organic light emitting diodes, OLEDs is discussed vis-à-vis the energy levels and properties.

    • Blue and white light electroluminescence in a multilayer OLED using a new aluminium complex

      Pabitra K Nayak Neeraj Agarwal Farman Ali Meghan P Patankar K L Narasimhan N Periasamy

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      Synthesis, structure, optical absorption, emission and electroluminescence properties of a new blue emitting Al complex, namely, bis-(2-amino-8-hydroxyquinolinato), acetylacetonato Al(III) are reported. Multilayer OLED using the Al complex showed blue emission at 465 nm, maximum brightness of ∼ 425 cd/m2 and maximum current efficiency of 0.16 cd/A. Another multilayer OLED using the Al complex doped with phosphorescent Ir complex showed `white’ light emission, CIE coordinate (0.41, 0.35), maximum brightness of ∼ 970 cd/m2 and maximum current efficiency of 0.53 cd/A.

    • Quantum chemical investigation on structures and energetics of Tungsten Fluoride (WF$_{n}^{f}$) species (𝑞 = 0, ±1; 𝑛 < 6)

      Ambrish Kumar Srivastava Anoop Kumar Pandey Neeraj Misra

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      The present work deals with a systematic study on WF𝑛 species using ab initio density functional method. The geometrical features related to the equilibrium structures of WF𝑛 species up to 𝑛 = 5 are highlighted and the effect of addition as well as removal of an electron is discussed. The chemical stability of these species is discussed by calculating their HOMO-LUMO energy gap and binding energy per atom. The frontier molecular orbital surfaces are also analyzed. The energy based electronic properties such as ionization potential, electron affinity, absolute electronegativity and chemical hardness are also evaluated which provide insights into chemical reactivity of these species.

    • An investigation on structural, vibrational and nonlinear optical behavior of 4b,9b-dihydroxy-7,8-dihydro-4bH-Indeno[1,2-b] Benzofuran-9,10(6H,9bH)-dione: A DFT study

      Tanveer Hasan Sayed Hasan Mehdi Raza Murad Ghalib P K Singh Neeraj Misra

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      A detailed theoretical quantum chemical study on 4b,9b-dihydroxy-7,8-dihydro-4bH-indeno[1,2-b] benzofuran-9,10(6H,9bH)-dione (Dihydroxy-Dihydro-Indeno-Benzofuran-Dione) has been discussed. The structure of the title molecule has been optimized and the structural parameters have been calculated by DFT/B3LYP method with 6-311++G(d,p) basis set. The fundamental vibrational wavenumbers as well as their intensities were calculated and excellent agreement between observed and calculated wavenumbers has been achieved and was interpreted in terms of potential energy distribution analysis. The electronic properties such as HOMO and LUMO energies and associated frontier energy band gap were calculated. Thermodynamical parameters along with the nonlinear optical (NLO) behavior of the title molecule are also discussed. The lower value of frontier orbital energy gap and a higher value of dipole moment suggest that the title compound is highly reactive. The NLO behavior of the title compound has been achieved by dipole moment, polarizability and first static hyperpolarizability. The large value of hyperpolarizability 𝛽total, indicates that the title molecule may serve as a good NLO material. The theoretical results were found to be in coherence with the measured experimental data.

    • Variable coordinating activity of sulfur in silver(I) complexes with thiophene based N¹ -substituted thiosemicarbazones: First case of thiopheneyl-thione sulfur bridging in a dinuclear complex


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      Thiophene-2-carbaldehyde / acetaldehyde-N¹-substituted thiosemicarbazones {R¹R²C² = N³ - N(H)- C¹(=S)N¹HR; R¹, R², R : C₄H₃S, H, Me, Httsc- NMe; C₄H₃S, H, Et, Httsc-NEt; C₄H₃S, H, Ph, Httsc-NPh; C₄H₃S, Me, Et, Hattsc-NEt} and furan-2-carbaldehyde-N-ethyl thiosemicarbazone (C₄H₃O, H, Et, Hftsc-NEt) were reacted with silver(I) halides/silver(I) acetate in presence of triphenylphosphine in organic solvents. These reactions yielded a series of dinuclear [Ag₂(μ-Br)₂ (κ-S-Httsc-NEt)2(PPh3)2]·2MeOH 1, [Ag2Cl2(κ1-SHttsc-NPh)2(μ-S,S-Httsc-NPh)2] 2, [Ag2Cl2(μ-S-Hftsc-NEt)2(κ1-S-Hftsc-NEt)2] 4, [Ag2(μ3-N3,S-ttsc-NMe)2 (Ph3P)2]·2(CH3)2CO 5, [Ag2 (μ3-N3,S-attsc-NEt)2(Ph3P)2]·0.5(CH3)2CO 6 and mononuclear [AgBr(κ1-SHttsc-NPh)(PPh3)2]· MeCN 3 complexes, all of which have been characterized using analytical techniques, IRand NMR spectroscopy, and X-ray crystallography. Thio-ligands bind in neutral form in complexes 1-4 and in anionic form in complexes 5-6. Further, the sulfur donor atoms have shown variable coordination modes incomplexes, namely, κ1-S in 1 and 3; κ1-S, μ-S in 4; κ1-S, μ-S,S (thiopheneyl-thione) in 2 and μ3- N3, S in 5 and 6. Tertiary-phosphine (PPh3) showed dual function of ligation/de-ligation towards silver(I) chloride during the synthesis of complexes 2 and 4. The bridge bonding of Httsc-NPh in 2 through thiopheneyl ring sulfur andthione sulfur is unprecedented in metal-thiosemicarbazone chemistry.

    • 3-/3,5-Pyrrole-substituted BODIPY derivatives and their photophysical and electrochemical studies


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      Nucleophilic substitution on 3-bromo/3,5-dibromo-4,4'-difluoro-8-(aryl)-4-bora-3a,4a-diaza-sindacene (BODIPY), substituted with anisyl or thienyl at meso positions, with neat pyrrole afforded the mono and di-pyrrole substituted BODIPYs 1–4 in good yields. Large bathochromic shifts, upto ∼180 nm in absorption maxima (581–682 nm), and fluorescence maxima (606–695 nm) were observed for these BODIPYs. Absorption and fluorescence properties were studied in different solvents to compare the effect of mono and di substitution on BODIPY. The Lippert-Mataga equations were used which predict strong polarization of monosubstituted BODIPYs. Electrochemical studies were carried out to find the oxidation potential and HOMO energy levels were calculated. Theoretical studies of 1–4 provide the insight on the electron density distribution in 1–4. Theoretical and experimental photo-physical studies in different solvents were correlated to findthe substituent effects on BODIPY.

    • Synthesis, photophysical, electrochemical and electroluminescence studies of red emitting phosphorescent Ir(III) heteroleptic complexes


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      Five heteroleptic, cyclometalated (CN) Iridium(III) complexes of acetylacetone (acac) and 1-phenyl-isoquinoline (piq) derivatives, Ir(acac)(piq) ₂, Ir(acac)(2,4-difluoro-piq) ₂, Ir(acac)(4-trifluoromethylpiq) ₂, Ir(acac)(4-N,N-dimethyl-piq) ₂, Ir(acac)(4-acetyl-piq) ₂, were synthesized and characterized. The ((CN) ₂ Ir(acac) complexes in toluene showed phosphorescence (λmax = 598 nm to 658 nm) with quantum yields (0.1 to 0.32) and microsecond lifetimes (0.43 to 1.9 μs). The complexes were non-luminescent in thin films due to self-quenching but luminescent when lightly doped (5%) in a host organic material, 4,4' -Bis(Ncarbazolyl)- 1,1' -biphenyl (CBP). The HOMO levels determined using cyclic voltammetric oxidation potentials were in the range−5.48 to−5.80 eV. Electroluminescence properties and performance of the Ir complexes dopedin CBP (active layer) were studied in a multilayer (ITO/F4TCNQ/TPD/doped CBP/BCP/LiF/Al) organic light emitting device (OLED). The electroluminescense (EL) spectra of the device matched with the phosphorescent spectra of the Ir complexes. The turn-on voltage at ∼4.5 V, maximum brightness of 7600 cd/m² and current efficiency of ∼7.0 cd/A at a brightness of ∼100 cd/m² indicate that these are promising OLED materials.

    • Deep blue organic light-emitting diodes of 1,8-diaryl anthracene


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      We report on the optimization of organic light emitting diode (OLED) devices using 1,8-di-(4-trifluromethylphenyl)-anthracene (CF3-DPA) as the active emissive layer. CF3-DPA emits in the deep blue region with an emission peak at 432 nm in solution which showed a slight red shift in thin films. CF3-DPA hashigh reported fluorescence quantum efficiency,~67%, as compared to 9,10-diphenyl anthracene (9,10-DPA).We optimized the OLED devices with different hole transporting layers (HTLs). Bilayer devices formed with N,N' -di(1-naphthyl)-N,N' -diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPD) as the HTL gave a reasonable light output. We observed that trilayer or multilayer devices with the inclusion of poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) and/or copper phthalocyanine as an additional HTL reduced the turn on voltage by ~5 to 9 V, though the brightness of the light emission also decreased. Including suitable carrier (electron or hole) transporting layers like 2, 2' ,2''' -(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)and 4,4' -Bis(N-carbazolyl)-1,1' -biphenyl (CBP) increases the efficiency of the devices. From our studies, we conclude that though NPD/CF3-DPA interface is crucial for light emission, the performance of the devices is limited by the mismatch of the hole and electron mobilities and the low internal quantum efficiency of CF3-DPA in the solid state. Devices having ITO/NPD/CF3-DPA/TPBi/LiF-Al geometry were observed to be the most efficient.

    • Synthesis of acridone-naphthylamine derivative and its thermallyactivated delayed fluorescence studies for application in OLEDs


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      Acridone (acceptor) and naphthylamine (donor) based Donor-Acceptor-Donor (D-A-D) compound (1) was synthesised, characterised and its thermally-activated delayed fluorescence (TADF) properties were studied in detail. Compound 1 is fluorescent and emits in the green region (550 nm). The energy gapbetween the ground and the lowest excited singlet (S1) state is estimated to be 2.55 eV. The energy gap between the CT singlet and triplet states (ΔEST) was found to be ~0.3 eV. Small ΔES1-T1 is one of the important criteria for TADF to take place in a molecule and thus detailed photophysics has been studied.Transient lifetime measurements showed an increase in the fluorescence lifetime (s) on purging with N2, as compared with that in air-saturated solution, indicating the involvement of the triplet state in emission. Emission at 550 nm was also observed with a delay of 100 ls which corresponded to the delayed fluorescencein 1. The lifetime of TADF was found to be 176 ls. Applications of TADF materials in organic lightemitting devices (OLEDs) has gotten attention as TADF materials utilise the triplet excitons which helps in increasing internal quantum efficiency of device. Air-saturated based on 1 were fabricated and their intensity was found to be nearly as high as 17,000 Cd/m2 at 25 mA/cm2 which was comparable to many of the known TADF emitters.

    • A hydrogel based on dialdehyde carboxymethyl cellulose–gelatin and its utilization as a bio adsorbent


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      In the present study, the dialdehyde carboxymethyl cellulose (DCMC) was cross-linked covalently to gelatin via the Schiff base reaction to form a three-dimensional hydrogel (DCMC-cl-G). The crosslinking degree of DCMC and gelatin was estimated to be 50.31 ± 2.65. The maximum swelling capacityof the hydrogel in aqueous medium was around 74 g/g at pH 10.0 and 37°C with equilibrium swelling attained in three hours and the compressive strength of the hydrogel was found to be 55 ± 0.76 kPa at 60% strain. The biodegradation studies confirmed 82.67% degradation of the hydrogel sample within a period oftwelve weeks. Further, the hydrogel was evaluated as a bio adsorbent for the removal of hazardous dyes, namely Rhodamine B (RhB) and Methyl Violet (MV) from water due to its decent swelling capacity and good mechanical strength. The maximum percentage of RhB and MV removed from the respective dye solutionsusing DCMC-cl-G hydrogel was 96.5% and 90% at pH 6.0, respectively. Both dyes followed Langmuir adsorption isotherm, which considers monolayer adsorption of adsorbate over adsorbent, with a pseudosecond-order kinetic model.

    • Synthesis, Spectroscopic Characterization, Biocidal evaluation Molecular Docking & DFT Investigation of 16-18 membered Macrocyclic Complexes of Cobalt (II)


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      Macrocyclic ligands (MacL1-MacL3) and Co(II) complexes were synthesized via template condensation of o-phenylenediamine with various aromatic dicarboxylic acids. The elemental analysis, FTIR,mass spectrometry, 1H NMR, 13C NMR, UV-vis, SEM analysis, powder X-ray diffraction, thermo-gravimetric(TG) analysis, electrochemical studies, and DFT analysis were used to characterize these synthesized ligands and their cobalt (II) complexes. TGA analysis to determine the stability and decomposition kinetic parameters. In element analysis, the percentage of different elements present and also the stoichiometry of compounds were confirmed. The proposed framework for tetraaza macrocyclic cobalt (II)complexes was supported by spectral analysis, which also revealed distorted octahedral geometry surrounding the central metal atom. The molecular structure of cobalt (II) complexes was also optimized theoretically, and their electronic or thermodynamic parameters were obtained from density functional theory (DFT). The synthesized ligands and their cobalt (II) complexes were tested against bacteria: Escherichia coli, Bacillus subtitles. Candida albicans were tested for antifungal properties. It was found that ligands and complexes show good antimicrobial results. Finally, using the Auto Dock VinaPyRx programme, molecular docking studies were used to evaluate the biological significance of the synthesized ligands to identify the probable and efficient binding mechanisms between the various ligands and the active site of the receptor protein.

      Antimicrobial, DFT, and Docking representation of Cobalt (II) macrocyclic complexes

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