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A novel alternative route to access rhenium(V)-phthalocyanine complexes through direct metalation of metal-free phthalocyanines (H

A new tailor-made azo dye of coumarin connected to phenolic derivative is presented herein. Azo-hydrazone tautomerism in aqueous solution of the dye was observed and studied using spectroscopic assays such as

Some dihydrobenzo[4,5]imidazo[1,2-c]quinazolines have been synthesized from aldehydes and ketones, using the ketones as both reagents and solvents and tetrahydrofuran (THF) as the solvent for the aldehydes, to yield the triazatetracyclics. The compounds have been characterized with spectroscopy and microanalysis. The crystal structures of 9,9-dimethyl-8,10,17-triazatetracyclo[8.7.02,7.011,16]heptadeca-1(17),2,4,6,11(16),12,14-heptaene (I), 9-butyl-9-methyl-8,10,17-triazatetracyclo[8.7.0.02,7.011,16]heptadeca-(17),2,4,6,11(16),12,14-heptaene (III) and 9-phenyl-8,10,17-triazatetracyclo[8.7.0 02 7.011,16]heptadeca-1(17),2,4,6,11(16),12,14-heptaene (VIII) have been discussed. The computed NMR, IR, molecular electrostatic potential and frontier molecular orbitals of compounds I, III and VIII have been discussed. The M06 functional gave most of its values closest to the experimental values for the bond lengths and bond angles of compounds I and III. For compound VIII, none of the functionals gave values for bond lengths and bond angles that were consistent with the experimental values, but M06 gave values closest to experimental values. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity of the triazatetracyclics showed that compound I exhibits significant DPPH scavenging activity with an IC50 of 56.18 µM compared to 2.37 µM for ascorbic acid.

Various benzoxazepine derivatives have been synthesized and characterized using IR, NMR, GC–MS, and microanalysis. The single-crystal X-ray structures of 2,2-dimethyl-4-[(E)-2-(4-methylphenyl)ethenyl]-2,3-dihydro-1,5-benzoxazepine (RS01), 4-[(E)-2-(2-chlorophenyl)ethenyl] -2,2-dimethyl-2,3-dihydro-1,5-benzoxazepine (RS05), 2,2,4-trimethyl-2,3-dihydrobenzothiazepine (RS11), and 2,2,4-trimethyl-2,3-dihydrobenzoxazepine (RS12) have been discussed. The compounds have been evaluated for their anticancer properties in breast cancer cells. 4-[(E)-2-(2-Chlorophenyl)ethenyl]-2,2-dimethyl-2,3-dihydro-1,5-benzoxazepine (RS03) and RS12 displayed potent cytotoxicity in both benign (MCF-7) and metastatic (MDA-MB-231) breast cancer cells. These compounds were more selective for the MCF-7 cells with RS03 being the most potent compound (IC50 = 15 µM) of the series. Upon further investigation, it was found that RS03 and RS12 induced cell cycle arrest in the G2/M phase and display limited toxicity against the noncancerous breast cell line, MCF-10A.

N-[(9E)-8,10,17-Triazatetracyclo[8.7.0.02,7.011,16]heptadeca-1(17),2,4,6,11(16),12,14-heptaen-9-ylidene] benzamide (I) is synthesized and characterized by spectroscopy, microanalysis, and single crystal X-ray diffractometry. Compound I crystallizes in the monoclinic space group P21/c with a = 15.8980(7) A, b = 4.8067(2) A, c = 21.0455(10) A, β = 101.153(2)°, and Z = 4. The experimental bond lengths and bond angles are contrasted with computed bond lengths and bond angles.

A novel colorimetric and fluorometric method based on coumarin as signalling unit was developed for Hg2+ recognition and quantification. Initially, the alkyne functionality was incorporated into a coumarin system and the resulting molecule showed higher specificity and sensitivity for Hg2+ over other cations in both absorption and emission sensing assays. The Hg2+ recognition was detected as visible colour change from colourless to yellow and as fluorescence quenching. The colour change was assigned to the increased intramolecular charge transfer (ICT) in the signalling unit upon Hg2+ binding whereas a decline in the fluorescence intensity was ascribed to the heavy atom effect from Hg2+. In order to generate a material with high sensing performance level, alkyne-functionalized molecule was hosted into a polymeric material. The resulting functionalized polymer showed higher sensitivity and selectivity for Hg2+ over its corresponding coumarin molecule. The investigation of the possible binding modes for Hg2+ suggested both alkyne and triazole functionalities as potential binding sites for Hg2+. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were evaluated and values less than a recommended maximum level of Hg2+contaminant in drinking water (2.00 μg/L) were obtained (LOD = 0.44 μg/L and LOQ = 1.33μg/L). The real-life application of the method was investigated using natural water samples containing Hg2+ levels equivalent to the maximum tolerable concentration of Hg2+ in drinking water. The outcomes suggested that the method could be used in the sensing and determination of Hg2+ level of contaminant in the environment.

Hydrodesulfurization (HDS) is a widely used process currently employed in petroleum refineries to eliminate organosulfur compounds in fuels. The current hydrotreating process struggles to remove organosulfur compounds with a steric hindrance due to the electronic nature of the current catalysts employed. In this work, the effects of adding chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) to rhodium (Rh) and active molybdenum (Mo) species for dibenzothiophene (DBT) HDS catalytic activity was evaluated. HDS activities followed the order of RhMo/ɣ-Al2O3 (88%) &gt, RhMo-AA/ɣ-Al2O3 (73%) &gt, RhMo-CA/ɣ-Al2O3 (72%) &gt, RhMo-EDTA/ɣ-Al2O3 (68%). The observed trend was attributed to the different chelating ligands with varying electronic properties, thus influencing the metal–support interaction and the favorable reduction of the Mo species. RhMo/ɣ-Al2O3 offered the highest HDS activity due to its (i) lower metal–support interaction energy, as observed from the RhMo/ɣ-Al2O3 band gap of 3.779 eV and the slight shift toward the lower BE of Mo 3d, (ii) increased Mo-O-Mo species (NMo-O-Mo ~1.975) and (iii) better sulfidation of Rh and MoO in RhMo/ɣ-Al2O3 compared to the chelated catalysts. The obtained data provides that HDS catalytic activity was mainly driven by the structural nature of the RhMo-based catalyst, which influences the formation of more active sites that can enhance the HDS activity.

Reliance on crude oil remains high while the transition to green and renewable sources of fuel is still slow. Developing and strengthening strategies for reducing sulfur emissions from crude oil is therefore imperative and makes it possible to sustainably meet stringent regulatory sulfur level legislations in end-user liquid fuels (mostly less than 10 ppm). The burden of achieving these ultra-low sulfur levels has been passed to fuel refiners who are battling to achieve ultra-deep desulfurization through conventional hydroprocessing technologies. Removal of refractory sulfur-containing compounds has been cited as the main challenge due to several limitations with the current hydroprocessing catalysts. The inhibitory effects of nitrogen-containing compounds (especially the basic ones) is one of the major concerns. Several advances have been made to develop better strategies for achieving ultra-deep desulfurization and these include: improving hydroprocessing infrastructure, improving hydroprocessing catalysts, having additional steps for removing refractory sulfur-containing compounds and improving the quality of feedstocks. Herein, we provide perspectives that emphasize the importance of further developing hydroprocessing catalysts and pre-treating feedstocks to remove nitrogen-containing compounds prior to hydroprocessing as promising strategies for sustainably achieving ultra-deep hydroprocessing.

Silica-supported vanadium oxides (VxOy-silica 600 °C) and polymer nanofiber [2-(2′-hydroxy-5′-ethenylphenyl)imidazole (PIMv) and styrene (ST) copolymer]-supported oxidovanadium(IV) ([VIVO-p(PIMv-co-ST)]) were synthesized and used as catalysts for the oxidation of refractory organosulfur compounds in fuels in a continuous flow system. Conversion of dibenzothiophene (DBT) to dibenzothiophene sulfone (DBTO2) increased as the flow rate decreased, reaching 100% at flow rates of 0.1 and 0.2 mL/h for (VxOy-silica 600 °C) and [VIVO-p(PIMv-co-ST)], respectively. This was attributed to improved contact time between the catalyst and substrate, which allowed further oxidation to take place. However, the catalytic activity of VxOy-silica 600 °C dropped by 33% after the first oxidation cycle at a flow rate of 0.1 mL/h at 60 °C, unlike [VIVO-p(PIMv-co-ST)], which maintained its activity at 100% after three cycles. Optimized conditions were employed in the oxidation of a hydrotreated fuel sample (Sasol diesel 500) follow...

The study provides a technological method for the removal of nitrogen compounds from fuels, via oxidation and extractive adsorption. The use of batch process resulted in lack of specificity of the quinoline oxidation reaction with several products produced via ring-opening while the flow micro-reactor presented a high degree of selectivity to quinoline-N-oxide (67%). The application of molecularly imprinted 2,6-pyridine-polybenzimidazole nanofibers displayed excellent quinoline-N-oxide removal (86%) with an adsorption capacity (qe) of 4.8 mg/g. Isothermal titration calorimetry (ITC) interactions between quinoline-N-oxide and 2,6-PyPBI confirmed a favourable interaction. DFT studies on quinoline-N-oxide vs 2,6-PyPBI further indicated: (i) a hydrogen bonding (through amino group of 2,6-PyPBI and oxygen atoms of the quinoline-N-oxide), (ii) pi-pi stacking and (iii) van der Waals interactions. The selective oxidation and adsorption of nitrogen compounds present in fuel, which has been demonstrated here, would be a sustainable green chemistry technology for the production of clean fuel. Keywords: Vanadium(V) oxide, tert-Butylhydroperoxide (t-BuOOH), Quinoline, Oxidation

A novel and structurally simple coumarin-based ligand (L) containing a picolinamide moiety was developed for fluorogenic detection of transition metal ions in water. Investigations of the absorption and emission spectra of L in the presence of different metal ions showed that the ligand has higher sensitivity and specificity towards Cu2+ in water over a number of metal ions. The presence of cupric ions induced significant fluorescence quenching in the emission spectrum of L which was assigned to the transfer of excitation energy from the fluorophore to the metal d-orbital and/or charge transfer from the fluorophore to the metal ion. NMR studies of the ligand upon continuous addition of Cu2+ indicated that the interaction with Cu2+ involved deprotonation of the hydroxyl group attached to coumarin. The latter affected the electronic properties of the coumarin system and the changes were detected in the emission spectrum of the ligand. The binding ratio of the L–Cu2+ complex was investigated through Job's plot analysis which indicated a 1 : 1 stoichiometric ratio between L and Cu2+ with an association constant of 2.33 × 106 M. TD-DFT calculations were performed to explain the electronic configuration of the ligand L, its possible Cu2+ complex and a possible quenching mechanism. Analytical application of the ligand L showed that the proposed method could be used successfully for the detection and quantification of Cu2+ in real samples at micromolar levels.

A novel fluorescent polymer for Hg2+ recognition was developed based on the phototautomerism mechanism of 7-hydroxycoumarin in aqueous solution. The developed system showed higher sensitivity and specificity towards Hg2+ in the acetonitrile/water mixture over various other metal ions, with a significant fluorescence quenching of the main emission band. It was shown that the presence of Hg2+ affects the chemical equilibrium of the 7-hydroxycoumarin phototautomers through the excited state intramolecular proton transfer (ESIPT) mechanism, which results in ratiometric fluorescence response upon stepwise addition of Hg2+. The occurrence of ESIPT mechanism was explained based on a comparison of the 1H NMR spectra of the starting alkynylated coumarin (4) in a non-polar aprotic solvent (CDCl3) and in a polar aprotic solvent (DMSO-d6). This was further confirmed by 1H NMR of 4 upon stepwise addition of Hg2+ in a polar aprotic solvent (DMSO-d6). From titration experiments, a higher sensitivity with a detection limit at the nanomolar level (50 nM) was observed and the response was fast and reversible. The real applications of the developed system were investigated in real samples and satisfactory results were obtained for both fresh and lake water samples.

2-(Benzamido)thiazolylbenzoate is synthesized via a novel method. It is characterized by spectroscopy, micranalysis, and GC-MS. It crystallizes in the monoclinic space group P21/n with a = 19.8990(5), b = 7.3680(2), c = 22.3845(6) A, β = 113.799(1)°, V = 3002.85(14) A3Z = 8. The HOMO-LUMO of the reactants and products are considered.

N-[(9E)-8,0 10,0 17-triazatetracyclo[8.7.0.02,7.011,18]heptadeca-1(17),2(7),3,5,11,13,15-heptaen-9-ylidene] acetamide (I) is synthesized and characterized by spectroscopy, microanalysis, and single crystal X-ray diffractometry. Compound 1 crystallizes in the monoclinic space group P21/n with a = 17.5552(17) A, b = 4.6163(4) A, c = 17.7662(17) A, β = 115.953(3)°, and Z = 4. The bond angles and bond lengths of the compound are computed using the density functional theory with B3LYP, BPW91, and wB97XD functionals and the 6-31G++(d,p) basis set. The frontier orbitals that contribute to the reactivity of triazatetracyclics are discussed.

Novel dithiourea derivatives have been designed as HIV-1 protease inhibitors using Autodock 4.2, synthesized and characterized by spectroscopic methods and microanalysis. 1-(3-Bromobenzoyl)-3-[2-({[(3-bromophenyl)formamido]methanethioyl}amino)phenyl]thiourea ( 10 ) and 3-benzoyl-1{[(phenylformamido)methanethioyl]amino}thiourea ( 12 ) gave a percentage viability of 17.9±5.6% and 11.2±0.9% against Trypanosoma brucei. Single crystal X-ray diffraction analysis of 1-benzoyl-3-(5-methyl-2-{[(phenylformamido)methanethioyl]amino}phenyl)thiourea ( 1 ), 3-benzoyl-1-(2-{[(phenylformamido)methanethioyl]amino}ethyl)thiourea ( 11 ), 3-benzoyl-1-{[(phenylformamido)methanethioyl]amino}thiourea ( 12 ) and 3-benzoyl-1-(4-{[(phenylformamido)methanethioyl]amino}butyl)thiourea ( 14 ) have been presented. 1-(3-Bromobenzoyl)-3-[2-({[(3-bromophenyl)formamido]methanethioyl}amino)phenyl]thiourea ( 10 ) gave a percentage inhibition of 97.03±0.37% against HIV-1 protease enzyme at a concentration of 100 µM.

A novel pyridyl-based ligand with multiple binding sites was developed as potential turn on fluorescent probe for mercuric ion. In comparison with other transition metal ions, the ligand displayed a significant optical selectivity and sensitivity for Hg

A novel colorimetric and fluorometric method based on coumarin as signalling unit was developed for Hg

Desulfurization of fuel oils is an essential process employed in petroleum refineries to reduce the sulfur content to levels mandated for environmental protection. Hydrodesulfurization (HDS), which is currently being employed, is limited in treating refractory organosulfur compounds and only reduces the sulfur content in fuels to a range of 200-500 ppmS. In this chapter, several scientific and technological advances reported in the literature for the desulfurization of fuels are reviewed and discussed. Amongst these techniques, oxidative desulfurization (ODS) and adsorptive desulfurization (ADS) are proposed as additional steps to complement HDS in meeting the mandated ultra-low sulfur levels (10 ppmS). In the ODS technique, refractory organosulfur compounds are oxidized to organosulfones, followed by solvent extraction or adsorption of the organosulfones. The chemistry involved in the development and fabrication of sulfur/sulfone responsive adsorbents is also discussed. The use of molecular imprinted polymers (MIPs) and coordination polymers (CPs) for the selective adsorption of organosulfone compounds (in ODS) and/or organosulfur (in ADS) offers various properties such as imprinting effect, hydrogen bonding, π-π interactions, van der Waals forces, π-complexation, and electrostatic interactions. CPs, in particular metal organic frameworks (MOFs), have been reported to possess suitable features to overcome most of these challenges associated with adsorptive ultra-deep desulfurization when design strategies to achieve good selectivity are strictly followed. Matching the sizes of the cavities to the critical dimensions of the sulfur containing compounds (SCCs), using suitable metal centres which allow for coordinative interaction with the SCCs and using linkers with suitable functionality as to enhance specific interaction (dispersion forces) with the SCCs were considered to be pivotal features to prioritize. The prospects for the use of MIPs and CPs for future industrial applications in desulfurization are envisaged.

A novel co-crystal of 2-aminobenzimidazole and 2-[(benzoylcarbamothioyl)amino] propanoic acid is synthesized and characterized by spectroscopy, elemental analysis, GC-MS, and single crystal XRD. A computation of the structures involved in the formation of the co-crystal are carried out and their contribution to reactivity is explained.

A series of 5-coordinate oxidovanadium(iv) complexes based on 2-(2'-hydroxyphenyl)imidazole (HPIMH), with substituent groups of different electronegativities on the phenolic para position (HPIMX; X = -H, -Br, -OMe and -NO2), were synthesized and characterized. Three of these complexes were characterized by single crystal X-ray diffraction, [VIVO(PIMH)2], [VIVO(PIMBr)2] and [VIVO(PIMNO2)2], as well as a dioxidovanadium(v) compound ([VVO2(PIMH)(PIMH2)]). The complexes were tested for their catalytic activities in the oxidation of dibenzothiophene (DBT), the major refractory organosulfur compound found in fuel. The nitro substituted compound [VIVO(PIMNO2)2] had the highest catalytic oxidation activity followed by: [VIVO(PIMH)2][VIVO(PIMBr)2][VIVO(PIMMeO)2]. The decrease in activity is attributed to the different electronegativities of the substituent groups, which influence the electron density on the metal center, the V[double bond, length as m-dash]O bond distances and infrared stretching bands. Geometry index (τ) values calculated from single crystal X-ray diffraction (SC-XRD) data and DFT studies provided further insights on the trend in activity observed. SC-XRD, EPR, 51V NMR and UV-Vis spectroscopies, and DFT studies were instrumental in studying the mechanism of the catalyzed reaction and proposal of intermediate species. Both radical and non-radical pathways are plausible for the catalytic oxidation and participation of reactive oxygen species in both pathways is also postulated.

A new selective cobalt acetate tetrahydrate or cerium nitrate hexahydrate mediated cleavage of the C–N bond of a benzoyl isothiocyanate derivative to give (carbamoylamino)methanethioamide is presented. The cleavage of the C–N could not be achieved in the absence of thione. The novel silver-mediated conversion of a thione to the carbonyl was achieved on 1-((benzamido)formyl)urea and replicated on (carbamoylamino)methanethioamide to give the deaminolyzed bisurea (dicarbamolyamine). The compounds were characterized by IR, NMR, microanalysis and GC–MS. The single crystal X–ray diffraction studies of the crystal structures of compoundsI,II,IIIandVis discussed.

Molecularly imprinted polymer (MIP) nanofibers were prepared by the electrospinning of poly 2-(1H-imidazol-2-yl)-4-phenol (PIMH) in the presence of various nitrogen containing compounds (N-compounds). Molecularly imprinted polymer nanofibers show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 11.7 ± 0.9 mg g−1, 11.9 ± 0.8 mg g−1 and 11.3 ± 1.1 mg g−1 for quinoline, pyrimidine and carbazole, respectively. Molecular modelling based upon density functional theory (DFT) indicated that hydrogen bond interactions may take place between the lone-pair nitrogen atom of model compounds (quinoline and pyrimidine) and the –OH and –NH groups of the PIMH nanofibers. The adsorption mode followed the Freundlich (multi-layered) adsorption isotherm, which indicated possible nitrogen–nitrogen compound interactions. Molecularly imprinted polymer nanofibers show potential for the removal of nitrogen-containing compounds in fuel.

Molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol microspheres (MIPs) were prepared by suspension polymerization of 2-(1H-imidazol-2-yl)-4-vinylphenol in the presence of nitrogen containing compounds (N-compounds). Nitrogen containing compounds such as quinoline, pyrimidine and carbazole, largely found in fuel oils, were employed as templates in MIP synthesis. Isothermal titration calorimetric (ITC) studies revealed that quinoline/2-(1H-imidazol-2-yl)-4-phenol (PIMH) and pyrimidine/2-(1H-imidazol-2-yl)-4-phenol (PIMH) interactions were exothermic (−18.0 ± 4.8 and −28.1 ± 3.6 kJ mol−1, respectively), while the carbazole/2-(1H-imidazol-2-yl)-4-phenol (PIMH) interaction was endothermic (3.3 ± 0.7 kJ mol−1). Imprinted microspheres show selectivity for the various target nitrogen-containing compounds in fuel oil with adsorption capacities of 10.56 mg g−1, 11.71 mg g−1 and 10.84 mg g−1 for pyrimidine, carbazole and quinoline, respectively. The removal of other stubborn nitrogen containing compounds from fuel oil demonstrates their potential application in the field of fuel denitrogenation.

The deleterious effects of refractory polyaromatic hydrocarbons found in fuels such as organo-sulfur compounds are such that they emit SOx to the environment when combusted, thereby reducing air quality. Herein, oxidative desulfurization (ODS) which is a complementary step to hydrodesulfurization (HDS) was carried out in an attempt to eliminate sulfur compounds in fuels. Refractory organosulfur compounds were oxidized using tert-butyl hydroperoxide as an oxidant and a poly[VO(allylSB-co-EGDMA)], (vanadium(IV) functionalized polymer of 6,6′-(1E,1′E)-(1,2-phenylenebis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-allylphenol) crosslinked with ethyleneglycol dimethacrylate) as a catalyst to convert sulfur compounds to polar sulfones. Some of the organosulfones were adsorbed via the use of molecularly imprinted polybenzimidazole nanofibers. The sulfur in heavy fuel oil after the oxidation/adsorption method fell below 8900 ± 200 ppmw S from the initial value of 17 920 ± 100 ppmw S.

Quaternary diammonium-functionalized polyvinyl benzyl chloride nanofibers were done using different diamines such as ethylenediamine (EDA), tetramethylene diamine (TMDA), hexamethylenediamine (HMDA), octamethylenediamine (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) with quaternization using methyl iodide, followed by conversion to a chloride form. These were called F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA, F-QUAT DMDA and F-QUAT DDMDA, respectively. Materials characterization was supported using elemental analysis, FTIR, XPS, SEM-EDS, TG and BET analysis. Langmuir and Freundlich's models were applied to analyze the adsorption of [IrCl6]2− and [RhCl5(H2O)]2− onto the materials, and the Freundlich model was obeyed. The mass transfer kinetics were tested on the pseudo-first-order and pseudo-second-order equations, and the process obeyed the pseudo-second-order kinetics. Column studies for the sorption of [IrCl6]2− using the functional materials were carried out and the loading capacities were 5.98 mg/g, 7.95 mg/g, 15.23 mg/g, 21.71 mg/g, 32.94 mg/g and 9.70 mg/g for F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA, F-QUAT DMDA and F-QUAT DDMDA, respectively. This was the order of an improvement in the methylene chain amongst the two ammonium groups up to ten carbons. Theoretically calculated electrostatic potential energies of the cations, dipole moments and solvation energies of the free cations and anions, energies for replacement of the chloride by [IrCl6]2−, and thermodynamic parameters for the formation of ion-pair complexes were used to explain this trend observed for the capacity of the functional reagents. The functional nanofibers displayed potential for use in selective recovery of iridium from rhodium.

A novel pyridyl-based ligand with multiple binding sites was developed as potential turn on fluorescent probe for mercuric ion. In comparison with other transition metal ions, the ligand displayed a significant optical selectivity and sensitivity for Hg2+ in aqueous solution with a remarkable fluorescence enhancement. The obtained spectroscopic response was related to the inhibition of the photo-chemical mechanism known as photo-induced electron transfer (PET) in the ligand and C N isomerization by Hg2+ binding. A good linearity between fluorescence responses and Hg2+ concentration was obtained in the range 3.3 × 10−9 M–1.6 × 10−8 M and a nanomolar level limit of detection (LOD) (1.4 × 10−9 M ~ 0.28 ppb) and limit of quantification (LOQ) (4.8 × 10−9 M ~ 0.93 ppb) were obtained. Both LOD and LOQ values are very low compared to the reported permissible Hg2+ level in drinking water (2 ppb) by US Environmental Protection Agency (EPA). The possible binding mode between ligand and Hg2+ were determined using Job's plot analysis and density functional theory (DFT) calculations and a complex with 1:1 stoichiometric ratio was suggested. The response of the pyridyl ligand upon Hg2+ addition was noted to be fast without any time delay and reversible. The performance of the ligand at nanomolar level of Hg2+ and real sample application of the proposed method was investigated and satisfactory results were obtained.

Merrifield resin functionalized with different quaternary diammonium groups derived from ethylenediamine (EDA), tetramethylenediamine (TMDA), hexamethylenediamine (HMDA), 1,8-diaminooctane (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) were investigated for the separation of [RhCl5(H2O)]2− and [IrCl6]2−. Selective loading of [IrCl6]2− in 6 M HCl medium onto the column was achieved in the presence of [RhCl5(H2O)]2− by the synthesized sorbents. The iridium loading capacities were 3.80, 6.49, 13.07, 19.29, 27.09 and 4.36 mg/g for EDA, TMDA, HMDA, OMDA, DMDA and DDMDA-functionalized microspheres, respectively. The materials showed great potential for application in separating rhodium and iridium from aqueous HCl solutions.

Three quaternary diammonium-functionalized polyvinylbenzyl chloride nanofibers were prepared using hexamethylenediamine (HMDA) quaternized with methyl, ethyl and benzyl groups to produce F-QUAT HMDA-methyl, F-QUAT HMDA-ethyl and F-QUAT HMDA-benzyl, respectively. The synthesized nanofibers were characterized by means of FTIR, XPS, SEM, BET surface area, thermogravimetric analysis and elemental analysis. The materials were used to investigate the adsorption and separation of [RhCl 5 (H 2 O)] 2− and [IrCl 6 ] 2− . Adsorption isothermal batch studies were conducted on both metal ion complexes ([RhCl 5 (H 2 O)] 2− and [IrCl 6 ] 2− ) using single metal aqueous solutions. The Langmuir isotherm confirmed monolayer adsorption for the uptake of both [RhCl 5 (H 2 O)] 2− and [IrCl 6 ] 2− using F-QUAT HMDA-ethyl, F-QUAT HMDA-methyl and F-QUAT HMDA-benzyl. The adsorption process of these materials obeyed the pseudo second-order kinetics, suggesting that chemisorption was be the rate-determining step. Column studies were conducted for a binary mixture of the metal ions chlorido species, and the iridium loading capacities of 15.2(0.8) mg/g, 9.7(0.7) mg/g and 42.9(0.7) mg/g were obtained for F-QUAT HMDA-methyl, F-QUAT HMDA-ethyl and F-QUAT HMDA-benzyl, respectively. This order was interpreted on the basis of inductive effects of the three quaternizing groups. The results provided important insight into the effect of derivatizing the cationic center on the loading capacity for [IrCl 6 ] 2− . This study presents truly iridium-specific sorption materials which can be applied to solutions of low grade ores or secondary raw materials of PGMs.

1,1′-Binaphthyl-2,2′-diol/quinoline (BINOL/QUN) and 1,1′-binaphthyl-2,2′-diol/isoquinoline (BINOL/ISOQUN) adducts were successfully synthesized. X-ray single crystals of BINOL/QUN and BINOL/ISOQUN were grown and analysed. The crystal packing of the molecules in both adducts confirmed that they are held in aggregates by strong hydrogen bonds (O2–H2⋯O3), (O3–H3⋯N1), (O2–H2⋯O1), (O1–H1⋯N1), (O2–H2⋯O1) and weak hydrogen C–H⋯π bonds. The patterns of the hydrogen bonding network as well as the conformation of BINOL contribute to the formation of the shape of the voids that entrap quinoline and isoquinoline. Molecular modelling which was employed to investigate the electronic properties of BINOL/QUN and BINOL/ISOQUN shows that the HOMO positions of the adducts are localized around the 1,1′-binaphthyl-2,2′-diol (BINOL), while the LUMO is positioned on isoquinoline and quinoline. Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) revealed a stronger isoquinoline/BINOL interaction compared to quinoline/BINOL. 6-Vinyl-1,1′-binaphthyl-2,2′-diol was co-polymerized with styrene to form [DBN-co-STY]. Electrospun [DBN-co-STY] exhibited selectivity for quinoline and isoquinoline in a model simulated fuel presenting an adsorption capacity of 2.2 and 2.4 mg g−1 respectively. The adsorption study showed a higher adsorption capacity for isoquinoline compared to quinoline. This may be attributed to the more favourable electronic properties (HOMO–LUMO properties) of isoquinoline. This concept demonstrates the possibility of extracting/separating isoquinoline and quinoline from fuel.

A test strip for the detection of ascorbic acid as well as dopamine employing the reduction of tris-(2,2′-pyridylimidazole)iron(III) immobilised on poly(vinylbenzyl chloride) nanofibres is reported. The strip is based on the standard spectrophotometric procedure for the detection of ascorbic acid in solution using the tris-(2,2′-pyridylimidazole)iron(III) complex, generated in situ, as the indicator. Poly(vinylbenzyl chloride) nanofibres were fabricated through electrospinning followed by post functionalization with a 2-(2′-pyridyl)-imidazole ligand and complexation with iron(III) to form a yellow fibre strip. On addition of ascorbic acid, the fibre strip turned red as a result of the reduction of the complexed iron(III) to iron(II). Similarly, dopamine is believed to form a high spin Fe(II) complex that yields a blue fibre strip. The nanofibre-based approach is much better and simpler as it eliminates the sample preparation step as well as the use of instrumentation because all the required reagents are incorporated within the nanofibre platform. The eyeball detection limit of the fibre test strip was 17.6 mg L−1 for ascorbic acid and 18.4 mg L−1 for dopamine, respectively. The LOD and LOQ values of ascorbic acid were 2.1 and 6.4 mg L−1, respectively, and 1.7 and 5.1 mg L−1 for dopamine, respectively.

A nickel vanadyl molecularly imprinted nanofiber (NVMIN) was developed by the electrospinning technique, employing polyethylene terephthalate (PET) and linear polyethylenimine (L-PEI) as the matrix polymers, nickel tetraphenylporphyrin (NTPP) and vanadyl tetraphenylporphyrin (VTPP) as the mixed-template molecules. The fabricated NVMIN was evaluated as a sorbent for the removal of NTPP and VTPP from organic media. The effects of trifluoroacetic acid (TFA), dichloromethane (DCM), dimethyl sulphoxide (DMSO), pentane (PEN) on electro-spinnability of the PET/L-PEI solutions and the morphological appearance of the PET/L-PEI fibers were investigated qualitatively by means of a scanning electron microscope (SEM). Electrospinning of 14 to 30% w/v PET/L-PEI solutions in TFA produced beaded and smooth fibers, depending on the concentration range. The addition of DCM and PEN as modifiers helped improve the electrospinnability, with PEN being the best, while the addition of DMSO made the solutions not spinnable. The results indicated that the NVMIN showed higher affinity (99% higher) for NTPP than the non-imprinted nanofiber (NIN) indicating that the NVMIN contained a lot of specific binding sites. It was determined that the NVMIN exhibited the same selectivity specialism for both NTPP and VTPP. However, the interaction strength was strongly dependant on the type of solvent, where the strongest interaction was achieved in chloroform. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of NTPP onto NVMIN was a spontaneous and exothermic process. Key words: Electrospinning, mixed-templates, adsorption, demetallation, solvents.

A reaction of an acid chloride with a diamine yielded a diamide. m-Toluic acid was chlorinated to m-toluoyl chloride and subsequently reacted with 4-methyl-o-phenylenediamine in pyridine to obtain 3-methyl-N-[2-(3-methylbenzamido)phenylbenzamide (I). 2-(3-Methylphenyl)-1H-benzimidazole (II) has been obtained upon reacting o-phenylenediamine with m-toluic acid in polyphosphoric acid and toluene. The compounds have been characterized by IR, NMR, microanalyses and GC-MS. The crystal structures of the compounds have been discussed. DFT calculations of the frontier orbitals of the precursor compounds have been carried out to ascertain the groups that contribute to the HOMO and LUMO, and to study their contribution to the reactivity in the formation of the diamides and benzimidazoles. The synthesis of the amide from a diamine was seen to be favoured in the presence of a good leaving group attached to the carbonyl as in the case of acid chloride. However, the synthesis of benzimidazoles was found to be favoured in the presence of an excess of a protonating agent and high temperature.

The reaction of benzoyl isothiocyanate with l -serine, l -proline, d -methionine and l -alanine gave 2-[(benzoylcarbamothioyl)amino]-3-hydroxypropanoic acid (I), 1-(benzoylcarbamothioyl)pyrrolidine-2-carboxylic acid (II), 2-[(benzoylcarbamothioyl)amino]-4-(methylsulfanyl)butanoic acid (III) and 2-[(benzoylcarbamothioyl)amino]propanoic acid (IV), respectively. The compounds have been characterized by IR, NMR, microanalyses and mass spectrometry. The crystal structures of all the compounds have also been discussed. Compound II showed rotamers in solution. DFT calculations of the frontier orbitals of the compounds have been carried out to ascertain the groups that contribute to the HOMO and LUMO, and to study their contribution to the reactivity of these compounds. The calculations indicated that the carboxylic acid group in these compounds is unreactive hence making the conversion to benzimidazoles via cyclization on the carboxylic acids impractical. This has been further confirmed by the reaction of compounds I–IV, respectively, with o-phenylene diamine which was unsuccessful but gave compound V.

A novel gold(I)-mediated intramolecular transamidation of thiourea derivatives to yield benzamides via dethiocyanation have been achieved by the reaction of 3-(1,3-benzothiazol-2-yl)-1-(benzoyl)thiourea derivatives in the presence of gold(I) precursors. The compounds have been characterized using IR, NMR, GC-MS and microanalysis. The single crystal XRD of 3-(1,3-benzothiazol-2-yl)-1-(3-bromobenzoyl)thiourea (5), 3-(1,3-benzothiazol-2-yl)-1-(3-methoxybenzoyl)thiourea (6), N-(benzothiazol-2-yl)benzamide (10), N-(benzothiazol-2-yl)-3-chlorobenzamide (11), N-(benzothiazol-2-yl)-4-nitrobenzamide (12), N-(benzothiazol-2-yl)-3-bromobenzamide (14) have been discussed. The novel transformation is thought to proceed by a gold(I)-mediated intramolecular transamidation reaction which releases thiocyanate to yield the benzamide. Density functional theory calculations have been used to support the proposed mechanism for this transformation.