Nitrogen Donor Research Articles

Fabrication of a new 2D Co(II)-organic framework tuned by semi-flexible dicarboxylate and 1,4-bis(4-pyridinylmethyl)piperazine ligands: Topology, DFT/UB3LYP calculations, Hirshfeld surface analysis and magnetic studies

A new 2D-coordination polymer, {[Co3(L−2)2(HL−)2(bpmp)](H2O)2}n (CP1) was synthesized by using a dicarboxylate ligand, H2L (5–benzylamino–isophthalic acid) and a nitrogen donor ligand 1,4-bis(4-pyridinylmethyl)piperazine (bpmp) with Co(NO3)2•6H2O under hydrothermal conditions via careful tuning the basicity of reaction conditions. Single crystal X-ray studies revealed that CP1 exist as a linear trinuclear cobalt cluster. DFT/UB3LYP/6-31G(d,p) calculations have been performed to study the ground state molecular geometry, IR spectrum, magnetic behavior by electron spin densities distribution as well as to explore various structure based molecular properties. The topological analysis of CP1 results an underlying sql net with a point symbol of {44.62}.Variable temperature magnetic susceptibility measurements of CP1 were carried out over the temperature range 2–300 K which indicates the existence of paramagnetic behavior.

Nickel(II) complexes of m-ethylphenylxanthate with nitrogen donors and their biological screening

A series of five adducts of m-ethylphenylxanthate of nickel(II) [(m-C2H5C6H4OCS2)2Ni] with nitrogen donors have been synthesized in 1:2 molar ratio by the reaction of aqueous solution of NiCl2.6H2O with aqueous solution of sodium salt of m-ethylphenylxanthate. These metal complexes are reacted with nitrogen donors to give donor stabilized complex, [(m-C2H5C6H4OCS2)2(L)2Ni] where, L= 2-, 3-, 4-ethylpyridine and 2-, 3-chloropyridine. The adducts have been characterized by elemental analysis, molar conductance and magnetic susceptibility measurements, IR, electronic, mass spectral studies, thermogravimetric analysis, powder X-ray diffraction, biological studies. The spectral studies have revealed the octahedral coordination of ligands around Ni(II) metal ion. The adducts are found to be paramagnetic and non-ionic in nature. Mass studies show the monomeric nature of the adducts. The complexes have depicted potential antifungal activity against Bipolaris maydis and Rhizoctonia solani. Some of the synthesized Ni(II) xanthate complexes display in vitro cytotoxic efficacy against human cancer cell lines.

Features of High-Frequency EPR/ESE/ODMR Spectroscopy of NV-Defects in Diamond

The methods of high-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE) and optically detected magnetic resonance (ODMR) are used to study the unique properties of nitrogen-vacancy (NV) defects in diamond in strong magnetic fields. It is shown that in strong magnetic fields (∼3–5 T) there occurs an effective optically induced alignment of populations of spin levels resulting in filling the level MS = 0 and emptying of the levels MS = ±1, that makes it possible to record ODMR using the change in the intensity of photoluminescence which reaches 10% at resonance. It is demonstrated that the efficiency of the alignment has the same order as in zero and low magnetic fields. The samples were preliminary studied by the ODMR method in zero magnetic fields that allowed accurate determination of the main parameters of the fine structure and hyperfine interactions with nitrogen nuclei, as well as dipole-dipole interactions between the NV center and deep nitrogen donors in the form of a nitrogen atom replacing carbon, N0. Hyperfine interactions with the nearest carbon atoms (isotope 13C) were observed in the high-frequency ODMR spectra, that opens up opportunities for measuring the processes of dynamic polarization of carbon nuclei in strong magnetic fields using optical methods. It is assumed that narrow ODMR lines in strong magnetic fields can be used to measure these fields with submicron spatial resolution. A new method for recording ODMR of NV centers with microwave frequency modulation has been developed, which simplifies the technique of measuring high magnetic fields. A significant increase in the intensity of the ODMR signal was demonstrated when a strong magnetic field was oriented along the symmetry axis of the NV center.

Enhanced Near-Infrared Emission from Eight-Coordinate vs Nine-Coordinate YbIII Complexes Using 2-(5-Methylpyridin-2-yl)-8-hydroxyquinoline.

Enhanced near-infrared (NIR) luminescence from two structurally related heterobinuclear NaIYbIII eight-cooridnate and heterobinuclear YbIIINaI eight-coordinate (CN = 8) complexes is reported and compared to a nine-coordinate (CN = 9) homoleptic complex. For the heteroleptic complex, [Yb(MPQ2)(acac)], the YbIII cation is coordinated to two tridentate 2-(5-methylpyridin-2-yl)-8-quinolinate (MPQ) anions, with a bidentate acetylacetonate (acac) anion completing the coordination sphere. Instead, the heterobinuclear [NaYb(MPQ)4] complex comprises a total of four anionic MPQ ligands, two of which exhibit κ3-coordination to the YbIII cation. The remaining two MPQ anions are unidentate toward the lanthanide and form μ2-bridges via the deprotonated quinolinate oxygens to a bound NaI cation which is also coordinated to the remaining nitrogen donor atoms. The structural properties of these complexes were evaluated by single-crystal X-ray diffraction (SXRD), continuous shape measure (CShM) analysis, and 1H NMR spectroscopy using a diamagnetic LuIII analogue. The corresponding photophysical properties were examined in CH2Cl2 solution by using absorption and emission spectroscopy. For both the complexes, characteristic YbIII emission is observed at ca. 980 nm, with recorded photoluminescence quantum yields (Φobs) and NIR luminescence lifetimes (τobs) of 2.0% and 14.0 μs vs 1.5% and 11.6 μs for the [NaYb(MPQ)4] and [Yb(MPQ)2(acac)] complexes, respectively. Interestingly, the eight-coordinate YbIII complexes both have higher photoluminescence quantum yields when compared to the homoleptic [Yb(MPQ)3] complex, which has a reported quantum yield of 1.0% and a NIR lifetime determined herein of 13.3 μs under identical conditions. These results have been rationalized by considering the overall efficiency of the ligand-centered sensitization process (ηsens = Φisc × Φeet), together with subsequent radiative (kr) and nonradiative (knr) deactivation of the YbIII cation. Moreover, the efficiency of the intersystem crossing (Φisc) and electronic energy transfer (Φeet) processes involved in the antennae effect have been quantified for the new complexes using a combination of nanosecond and femtosecond transient absorption techniques and have been compared to our previous results using [Ln(MPQ)3] complexes with Ln = Yb and Lu.

The Role of Zinc(II) Ion in Fluorescence Tuning of Tridentate Pincers: A Review.

Tridentate ligands are simple low-cost pincers, easy to synthetize, and able to guarantee stability to the derived complexes. On the other hand, due to its unique mix of structural and optical properties, zinc(II) ion is an excellent candidate to modulate the emission pattern as desired. The present work is an overview of selected articles about zinc(II) complexes showing a tuned fluorescence response with respect to their tridentate ligands. A classification of the tridentate pincers was carried out according to the binding donor atom groups, specifically nitrogen, oxygen, and sulfur donor atoms, and depending on the structure obtained upon coordination. Fluorescence properties of the ligands and the related complexes were compared and discussed both in solution and in the solid state, keeping an eye on possible applications.

Ferrocenylated imine- and amine(secondary/tertiary)- phosphine P^N ligands and their Pd(II) complexes: Synthesis and structural characterization

A new family of ferrocenylated P^N ligands where the nitrogen donor is either of an imine or amine (secondary/tertiary), was synthesized. The condensation reaction between diphenylphosphino propylamine and formyl ferrocene led to the formation of imine ligand [(η5-C5H5)Fe{(η5-C5H4)CH=N-(CH2)3-PPh2)}] (1), which on reduction with NaBH4 gave secondary amine ligand [(η5-C5H5)Fe{(η5-C5H4)CH2-NH-(CH2)3-PPh2)}] (2). Additionally, nucleophilic substitution reaction of diphenylphosphino ethyl/propyl amine with [FcCH2NMe3+][I−] salt leads to tertiary-amine ligand [(η5-C5H5)Fe(η5-C5H4)CH2]2-N-(R-PPh2) where R= C2H4 (3) and C3H6 (4). The newly synthesized ferrocenylated ligands were then complexed with Pd(II) giving [cis(κ2-P^N)PdCl2] type complexes (5-8), where imine, secondary amine, and tertiary amine ligands act as a bidentate ligand. The molecular structures of ligand (3), and complexes (5), (6), and (7) have also been determined by X-ray crystallography. In the molecular structures of these complexes, the Pd(II) center presents a distorted square-planar geometry. During the isolation of ligand (4), corresponding phosphine oxide (4A) along with a phosphonium salt (4B) was also isolated as by-products and were characterized by X-ray crystallography. The preliminary catalytic evaluation of complex (7) in the Suzuki-Miyaura cross-coupling reaction of arylboronic acids with aryl bromides was performed.

Metabolomic Analysis of the Serum in Rats with Methamphetamine-Induced Conditioned Place Preference

To understand what happens in the serum after methamphetamine (MA) administration, nuclear magnetic resonance-based metabolomics was performed to investigate the characteristic metabolite profile in the serum of rats with MA-induced conditioned place preference. The results showed that tyrosine concentration was significantly higher in the MA-induced group (1.68 × 10–5 ppm) than in the control group (0.99 × 10–5 ppm) (p = 0.004), uncharacterized lipid concentration was significantly higher in the control group (1.28 × 10–3 ppm) than in the MA-induced group (0.78 × 10–3 ppm) (p = 0.008), acetone concentration was significantly higher in the control (1.65 × 10–4 ppm) than in the and MA-induced group (1.10 × 10–4 ppm) (p = 0.005), and leucine concentration was significantly higher in the control (5.20 × 10–4 ppm) than in the MA-induced group (4.37 × 10–4) (p-value = 0.03). This decrease in acetone concentration in the MA-induced group may help elucidate why ketogenic diet has shown promise for many neurological disorders. Tyrosine is the precursor of dopamine and γ-aminobutyric acid, and leucine is the major nitrogen donor for glutamate synthesis. These results suggest that a disturbance in the substrate supply in the circulatory system partly explains MA toxicity in the central nervous system.

Synthesis, Structures, and Water Adsorption of Two Coordination Polymers Constructed by M(II) (M = Ni (1) and Zn (2)) with 1,3-Bis(4-Pyridyl)Propane (bpp) and 1,2,4,5-Benzenetetracarboxylate (BT4-) Ligands.

Two coordination polymers (CPs), with chemical formulas {[Ni2(bpp)2(BT)(H2O)6] 1.5(EtOH) 1.5H2O}n (1) and [Zn(bpp)(BT)0.5]·5H2O (2) (bpp = 1,3-bis(4-pyridyl)propane, and BT4− = tetraanion of 1,2,4,5-Benzenetetracarboxylic acid), have been synthesized and structurally characterized by single-crystal X-ray diffraction methods. In compound 1, the coordination environments of two crystallographically independent Ni(II) ions are both distorted octahedral bonded to two nitrogen donors from two bpp ligands and four oxygen donors from one BT4- ligand and three water molecules. Both bpp and BT4− act as bridging ligands with bis-monodentate and 1,4-bis-monodentate coordination modes, respectively, connecting the Ni(II) ions to form a 2D layered metal-organic framework (MOF). Adjacent 2D layers are then arranged orderly in an ABAB manner to complete their 3D supramolecular architecture. In 2, the coordination environment of Zn(II) ion is distorted tetrahedral bonded to two nitrogen donors from two bpp ligands and two oxygen donors from two BT4− ligands. Both bpp and BT4- act as bridging ligands with bis-monodentate and 1,2,4,5-tetrakis-monodentate coordination modes, respectively, connecting the Zn(II) ions to form a 3D MOF. The reversible water de-/adsorption behavior of 1 between dehydrated and rehydrated forms has been verified by cyclic Thermogravimetric (TG) analyses through de-/rehydration processes. Compound 1 also exhibits significant water vapor hysteresis isotherms.

Multifaceted role of branched-chain amino acid metabolism in cancer

Metabolic reprogramming fulfils increased nutrient demands and regulates numerous oncogenic processes in tumors, leading to tumor malignancy. Branched-chain amino acids (BCAAs, i.e., valine, leucine, and isoleucine) function as nitrogen donors to generate macromolecules such as nucleotides and are indispensable for human cancer cell growth. The cell-autonomous and non-autonomous roles of altered BCAA metabolism have been implicated in cancer progression and the key proteins in the BCAA metabolic pathway serve as possible prognostic and diagnostic biomarkers in human cancers. Here we summarize how BCAA metabolic reprogramming is regulated in cancer cells and how it influences cancer progression.

Dinickel(II) complexes with pyridine-substituted bis(triazolylmethyl)amine ligands: Structures and magnetic properties

The coordination behavior of the newly prepared bis(triazolylmethyl)amine-type ligands bis[(1-R-1H-1,2,3-triazol-4-yl)methyl]amine [R = CH2Ph (L1), CH2-2-pyridyl (L2)] and 1-(1-benzyl-1H-1,2,3-triazol-4-yl)-N-((1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)methanamine (L3) toward NiII ions was investigated. The reaction of NiCl2·6H2O with the benzyl-substituted bis(triazolylmethyl)amine ligand L1 afforded the mononuclear NiII complex Ni(L1)2Cl2 (1). On the other hand, dinuclear NiII complexes, [Ni2(L2)2Cl2]Cl2 (2) and [Ni2(L3)2Cl2]Cl2 (3), were obtained when NiCl2·6H2O was reacted with the pyridine-substituted ligands L2 and L3, respectively. Single-crystal X-ray analysis revealed that the two octahedral NiII centers in 2 and 3 are bridged by two triazole rings through nitrogen donors to generate the dinuclear complexes with a syn arrangement. Meanwhile, treatment of Ni(NO3)2 with L2 afforded the related dinickel(II) complex [Ni2(L2)2(NO3)2](NO3)2 (2′), in which two non-bridging triazole rings and two nitrate ions are positioned in an anti arrangement. Complexes 2 and 3 showed antiferromagnetic coupling between the two NiII centers (S = 1), with J values following the trend: 2′ > 2 > 3.

Modular construction and photocatalytic properties of two Co(II) metal-organic frameworks

The self-assembly of 5-fluorine-3-(3,5-dicarboxylphenxoy)benzoic acid(H3L) with cobalt(II) salts in absence as well as presence of a nitrogen donor ancillary ligand 1,1′-(1,4-butanediyl)bis(imidazole) (bib)yields two new metal–organic frameworks (MOFs) with formula[Co2(μ3OH) (L)(H2O)3·2·75H2O]n (1) and [Co2(μ3OH)(L)(bib)(H2O)2]n (2).The crystallographic studies reveal that1 exhibits only 2D bilayer structure, while 2displays 8-connected node 3-periodic network. The photocatalytic activities of the newly designed MOFs have been tested for the degradation of a model organic dyemethyl violet (MV). The photocatalytic experimental results demonstrated that both 1 and 2 displayed efficient photocatalytic performances to degrade MV under UV irradiation. The mechanism using which these MOFs executed photocatalytic behaviour has been proposed through band structure calculations.

Capabilities of Compact High-Frequency EPR/ESE/ODMR Spectrometers Based on a Series of Microwave Bridges and a Cryogen-Free Magneto-optical Cryostat

A magnetic resonance spectrometer operating at several fixed frequencies in the millimeter range is designed on the basis of a new generation of microwave bridges and a cryogen-free magneto-optical cryogenic system. The spectrometer allows measurements of EPR in continuous wave and pulse (free-induction decay, FID and electron spin echo, ESE) modes, photo-EPR, and optically detected magnetic resonance (ODMR) in a wide range of temperatures (1.5–300 K) and magnetic fields (up to 7 T with the ability to invert the field). It is based on a line of unified microwave bridges with a powerful oscillator and a superheterodyne receiver. Currently, they operate in W and D bands (at 94 and 130 GHz, respectively), but the frequency bands can be extended. In addition to highly stable fixed-frequency oscillators with narrow spectrum (better than − 100 dBc at 10 kHz offset at 94 GHz), they have variable frequency oscillators, which simplify tuning of the microwave circuit with a resonator and allow operation with frequency modulation when using a non-resonant microwave system. In the latter, it is possible to study large samples and quickly change the operating frequency of the spectrometer, simply replacing the microwave bridge. For all frequencies, the spectrometer uses common hardware and original software. The performance of the spectrometer at 94 GHz and 130 GHz was tested in measurements of CW-EPR, ESE and ODMR of NV defects in diamond single crystals, Tb3+ and Ce3+ ions in yttrium aluminum garnet crystals, nitrogen donors, and V3+ ions in 6H-SiC.

Theoretical analysis of the spodium bonds in HgCl2⋯L (L = ClR, SR2, and PR3) dimers

Abstract Halogen bonds have received increasing interest in non-covalent interactions. Recently, a new kind of non-covalent interaction, spodium bond, was proposed to refer to a net attractive interaction between any element of group 12 and electron rich atoms. Due to strong relativistic effect, Hg is much different from the other group 12 elements, which prefers more linear coordination. Thus, we theoretically studied the model of HgCl2⋯L (where L = ClR, SR2, PR3 families) to explore the nature of the linear coordinated spodium bonds. Analyses of electrostatic potential surfaces, together with ELF, LOL, and chemical bonding analyses, suggest the presence of covalent interaction. Complexes with nitrogen, oxygen, and fluorine donors result in more coulombic component, whereas others are dominated by covalent interaction, indicating coexistence of coulombic and covalent interaction. Besides, covalent interaction is significantly stronger with phosphorus donor. This model can provide intriguing perspectives for future weak intermolecular interactions studies.

Towards new routes to increase the electrocatalytic activity for oxygen reduction reaction of n-doped graphene nanofibers

A facile preparation of nitrogen doped graphene nanofibers (GNF) is required in order to promote an easy scalable method for the production of batteries using this material as catalyst support. In this work, two simple oxygen pretreatments were developed in order to maximize the nitrogen amount on the structure of the carbon nanomaterial. In that sense, a mild-term oxidation with acid and a high oxidative procedure using potassium permanganate were developed. After that, the two oxidized fibers and the raw ones were doped using a hydrothermal method which use 2-chlorethyl amine as nitrogen donor. All the materials have been deeply studied by SEM, RAMAN, FTIR, CHNS, Zeta potential, XRD, N2 adsorption-desorption and, TGA analysis. The characterization of the material showed that its structure after the treatments was more defective, significantly varying the surface area of the final material. After the hydrothermal treatment different amounts of N atoms (1.2–5.5%) were introduced in the structure depending on the oxidative treatment. The introduction of the nitrogen atoms increases the activity on oxygen reduction reaction (ORR) in almost all the cases, increasing further in the case of the GNF pretreated with acids which increase the electrochemical activity considerably.

Influence of Hyperfine Coupling Strain on Two-Dimensional ESEEM Spectra from I = 1/2 Nuclei

HYSCORE, a variant of two-dimensional ESEEM spectroscopy, is currently one of the most effective tools in high-resolution solid-state EPR spectroscopy. Our systematic studies of hydrogen bonds with semiquinones in 15N-labeled proteins have previously provided us with an extensive collection of 15N HYSCORE spectra produced by N–H…O nitrogen donors. Examination of these spectra has indicated in several cases lineshape distortions not described by available theoretical models. We were able to explain all observed artificial phenomena in the 15N spectra of semiquinones considering a single mechanism—strain of the isotropic hyperfine interaction. In this review article, we introduce the HYSCORE experiment and the theoretical background for spectra of I = 1/2 nuclei in orientation-disordered samples. We then present a description of the observed lineshape distortions and an explanation of the hyperfine strain’s influence on the experimental spectra. In the final part of the article, we discuss (i) similar lineshape distortions found in previously published spectra from 15N, 29Si, 31P, and 57Fe nuclei that can be explained using the approach applied for the analysis of the 15N spectra of semiquinones, and (ii) a recently published analysis of 31P spectra with a different type of lineshape distortion based on a more sophisticated method, where the strength of anisotropic coupling is correlated with the sign and value of the isotropic constant in different conformations of a Cu(II) complex.

Intrinsic Effect of Pyridine-N-Position on Structural Properties of Cu-Based Low-Dimensional Coordination Frameworks.

Metal-organic assemblies have received significant attention for catalytic and other applications, including gas and energy storage, due to their porosity and thermal/chemical stability. Here, we report the synthesis and physicochemical characterization of three metallosupramolecular assemblies consisting of isomeric ambidentate pyridyl-β-diketonate ligands L1–L3 and Cu(II) metal ions. It has been demonstrated that the topology and dimensionality of generated supramolecular aggregates depend on the location of the pyridine nitrogen donor atom in L1–L3. This is seen in characterization of two distinct 2D polymeric assemblies, i.e., [Cu(L1)2]n and [Cu(L2)2]n, in which both β-diketonate and pyridine groups are coordinated to the Cu(II) center, as well as in characterization of the mononuclear 1D complex Cu(L3)2, in which the central atom is bound only by two β-diketonate units.

Novel N-(2-((4-vinylbenzyl)thio)ethyl)Acetamide Functionalized Magnetite Nanoparticle: Synthesis and Test Selective Silver(I) Removal Study

Magnetic nanoparticles embody a valuable suite of technologies for the selective recovery of metals from the aqueous phase owing to their high surface area, the ease of recovery using an externally applied magnetic field and their ability to be custom designed. Ligands bearing sulfur (S-) and nitrogen (N-) donors are suited for such functionalization due to their proven selectivity’s for Ag(I) binding. Herein, we report the synthesis of a novel ligand—N-(2-((4-vinylbenzyl)thio)ethyl)acetamide in two steps and with a 76% yield. Also, the attachment of the ligand to the surface of magnetite nanoparticle with the aid of azobisisobutyronitrile (AIBN) was achieved under mild conditions. The ligand-magnetite nanosorbent demonstrated excellent removal efficiency (99.9%) and outstanding selectivity for Ag(I) recovery under the prevailing experimental conditions. Taking together, the results indicate that N-(2-((4-vinylbenzyl)thio)ethyl)acetamide on magnetite nanoparticles is an efficient sorbent for the selective recovery of Ag(I) from the aqueous phase.

Novel pyrazolate-bridged binuclear Ni(II), Cu(II) and Zn(II) complexes: Synthesis, X‐ray crystal structure and nonlinear optical studies

In this paper, a pyrazole based ligand (1) containing nitrogen and sulfur donors was prepared and used in the synthesis of the following new binuclear Ni(II), Cu(II), and Zn(II) complexes [Ni2(EtNCSPzMe2)2(µ-PzMe2)2] (2), [Cu2(EtNCSPzMe2)2(µ-PzMe2)2] (3) and [Zn2(EtNCSPzMe2)2(µ-PzMe2)2] (4). The ligand and complexes were characterized by spectroscopic and physico-chemical methods. The crystal structure of [Ni2(EtNCSPzMe2)2(µ-PzMe2)2] was determined by X-ray diffraction analysis. Crystal structure of the (2) describes a binuclear complex, in which nickel ions are bonded by N3S donor atoms set in distorted square planar coordination geometry and the dimethyl pyrazolate groups are placed as the bridge among the metal centers. The nonlinear optical responses of the prepared ligand and metal complexes were investigated under irradiation of 35 mW continuous wave He-Ne (632.8 nm) laser. The z-scan technique was applied for measurement the second-order refractive index (n2) of the synthesized samples. Results show that copper complex (3), demonstrates the highest value of the measured n2 (−10.18 × 10−7 mmW−1).

Synthesis, crystal structure, spectroscopic study and Hirshfeld surface analysis of [Ni(C6H8N2)3]Cl2.2(H2O) (1)

The title compound, [Ni(C6H8N2)3]Cl2.2(H2O), was synthesized by slow evaporation method at room temperature. The structural study by X–ray diffraction indicate that this compound crystallize in the triclinic system, P-1 space group with a = 10.222(2) Å, b = 10.757(2) Å, c = 11.441(3) Å, α=114.30(4)°, β=99.43(3)° and γ=93.01(3)°. The structure is formed by the cation [Ni(C6H8N2)3]2+, tow chloride anions and two molecules water of crystallization. The nickel (II) atom is coordinated to six nitrogen donors from three neutral 2-AMP ligands, adopting a slightly distorted octahedral geometry. The crystal structure is stabilized by strong hydrogen bonds of N–H…Cl, O–H…Cl, C–H…Cl and π–π interactions to obtained three–dimensional network. The newly prepared compound was characterized by XRD, Infrared, UV–Vis spectroscopy and Hirshfeld surface (3D-HS) analysis. Vibrational analysis of the compound was realized by infrared spectroscopy. The optical properties of the crystal were studied using optical absorption UV–visible spectroscopy which confirmed the semiconducting properties by revealing a direct optical band. Hirshfeld Surface projections and Fingerprint plots were elucidated the relative contribution of the H…Cl, C…H, C…C, C…N, H…O intermolecular contacts in the crystal.

Synthesis, silver (I) extraction and silver (I) binding studies of novel N1,N3-bis(2-(benzylthio)ethyl)propanediamide derivatives

Solvent or liquid–liquid extraction represents a highly valuable technique for the selective recovery of metals from the aqueous phase due to the ease of operation and short turnaround times. Ligands bearing soft donor atoms including nitrogen and sulfur are ideal candidates for selective silver recovery due to their preference for silver binding. Herein, novel N1,N3-bis(2-(benzylthio)ethyl)propanediamide derivatives bearing sulfur and nitrogen donor atoms were prepared in low to high yields and tested for Ag+ extraction from ternary aqueous solutions also containing Cu2+ and Pb2+ following a well-established solvent extraction protocol. It was observed that electronics effects at the 4-aryl position in the propanediamide (or malondiamide) derivatives had a significant effect on the selectivity, but little effect on the efficiency of Ag+ extraction with the 4-methoxy analogue proving the most selective. Steric hindrance provided by dimethyl substitutions at the α-positions to the sulfur atoms had negative effects on Ag+ extraction efficiency and selectivity, while diethyl steric hindrance at the methylene center lowered selectivity but increased extraction efficiency for Ag+. Detailed binding studies reveal that one of the malondiamide derivatives which lacked the electronic and steric hindrance groups studied coordinated Ag+ in a 1:1 fashion suggesting a tetrahedral complex geometry. Overall, the results show that simple modification of the electronics and sterics of the N1,N3-bis(2-(benzylthio)ethyl)propanediamides, can improve their selectivity for Ag+ recovery from the aqueous phase.