Effect Of Spacer Group Research Articles

Enhancing recovery of gold(III) from hydrochloric acid solutions using gemini surfactant microemulsions: The effect of spacer group

The recovery of precious metals from waste has garnered significant attention owing to their non-renewable nature and essential role in the burgeoning information industry. However, enhancing the extraction efficiency of microemulsions remains a significant challenge. In this study, three water-in-oil microemulsions were formulated using gemini surfactants with different spacers (14-OH-14, 14-SO4-14, and 14-3-14) as emulsifiers, supplemented with n-butanol as a cosurfactant, n-heptane as the oil phase, and NaCl aqueous solution as the internal aqueous phase. These microemulsions were employed for the extraction of gold(III) from hydrochloric acid solutions. The results illustrate that all three microemulsions effectively extracted gold(III) through a spontaneous, exothermic, enthalpy-driven anion-exchange mechanism, achieving notable extraction efficiency. In contrast to 14-3-14, incorporating –OH into the spacer significantly augments the positive electrostatic potential through the cationization of –OH in an HCl solution, resulting in a higher binding constant (2.43) and thereby improving the extraction efficiency. However, the presence of −SO4 diminishes the positive electrostatic potential through partial neutralization, resulting in a lower binding constant (1.17), which is detrimental to the extraction process. Response surface optimization revealed that concentrations of C(14-OH-14) and V(1-butanol) significantly influence extraction efficiency and exhibit pronounced interaction. At optimal conditions (C(14-OH-14) = 0.09 mol·L−1, V(1-butanol) = 47.41 %, R=20, and C(NaCl) = 1.57 mol·L−1), over 95.54 % of gold(III) can be extracted from actual e-waste solutions. This study offers an alternative approach for designing or selecting surfactants in microemulsion-based extraction of gold(III) from e-waste.

Circularly polarised luminescence from intramolecular excimer emission of bis-1,8-naphthalimide derivatives.

Chiral excimers exhibit unique photophysical behaviour. However, further molecular design is required along with systematic studies on the effect of spacer groups and solvent polarity. In this study, we prepared four circularly polarised luminescence (CPL)-active molecules that exhibit intramolecular excimer emission. Bis-1,8-naphthalimide (bNI) derivatives D-LybNI, L-LybNI, D-LyMebNI, and L-LyMebNI were prepared with chiral backbones and alkyl linkages between the NI rings with chain lengths of five carbon atoms, suitable for excimer fluorescence. The fluorescence properties were investigated experimentally and theoretically using density functional theory. The molecules exhibited intramolecular excimer fluorescence in polar organic solvents. Mirror-image circular dichroism and CPL spectra were obtained for the D and L forms. D- and L-LyMebNI exhibited relatively large luminescence dissymmetry factors (|glum|) in acetonitrile of 1.9 × 10-3 and 1.6 × 10-3, respectively. Thus, this study demonstrates chiral bNI derivatives with simple synthesis procedures that emit intramolecular excimer fluorescence and have effective CPL properties. These molecules are promising for developing organic molecular systems with bright, highly polarised emission.

Studies on physicochemical properties of three Gemini surfactants with different spacer groups

Three Gemini surfactants with the same hydrophobic chain but different spacer groups, including two cationic Gemini surfactants (CGS and CGS-O) and a zwitterionic Gemini surfactant (ZGS-S), were synthesized, and their chemical structures were characterized by FT-IR and 1H NMR. The effect of spacer group on surface/interface activity, interfacial tension at the oil-water interface, wetting ability, electrolytes tolerance and thermal stability was determined. The results showed the structure of spacer group has a certain influence on the surface/interface activity. Among the three Gemini surfactants, ZGS-S has the strongest ability to reduce surface tension, followed by CGS-O. Three Gemini surfactants can reduce the oil-water interfacial tension to ultra-low value, but the time required to reach the minimum value is different, indicating that the surfactant molecules move at different adsorption rates from solution to the interface. This phenomenon is also confirmed by dynamic surface tension and dynamic contact angle tests. Compared with CGS, CGS-O molecules move slower in the solution, while the adsorption rate of ZGS-S on the interface surpasses that of CGS near the critical micelle concentration. Among the three Gemini surfactants, the electrolytes tolerance of ZGS-S is the strongest, while CGS-O is the lowest. The introduction of sulfate group in spacer group reduces the thermal stability of Gemini surfactant.

Evaluating the electronic properties of ditopic and hetero-ditopic ligands derived from benzimidazole and pyrazole by 13C NMR spectroscopy

Huynh’s electronic parameter (HEP) was applied to distinguish the electronic properties of benzimidazole and pyrazole donors in N^N ditopic and N^N′ hetero-ditopic, dinucleating ligands by 13C NMR spectroscopy of their dipalladium complexes bearing terminal iPr2-bimy reporter ligands. The 13Ccarbene NMR resonances of the iPr2-bimy ligand (HEPs) indicate stronger donation of the symmetrical dibenzimidazole compared to that of the dipyrazole with a ΔHEP value of 1.54 ppm. Based on this benchmark value, the effect of spacer groups on the electron donation of the mixed benzimidazole-pyrazole ligands was investigated for the first time. The donicity gap between the benzimidazole and pyrazole donors increases with alkylene spacers, but shrinks with the 1,4-phenylene linker, suggesting electronic communication between the two different heterocycles via π-electron conjugation. Furthermore, these complex probes could also be used to catalyze the direct arylation of pentafluorobenzene, which showed that the unsymmetrically bridged, dinuclear complexes with alkylene linkers are more reactive.

Theoretical study on the effect of spacer groups on the nonlinear optical properties of polyvinyl carbazole molecular fragments

In this paper, polyvinyl carbazole fragments with side-hung chromogenic groups were used as the parent. The relationship between the structure and the properties of NLO was studied by changing the type of spacer groups on chromogenic groups with density functional theory (DFT). The results show that all designed systems have significant second-order NLO response. The first hyperpolarizability (β0) of the system has the following regularity (taking PBE0 algorithm as an example): the β0 value of the system is related to the type of electron-donating and electron-withdrawing spacer group (X).The β0 value of electron-donating spacer group is larger than that of electron-withdrawing spacer, and the β0 value of the molecule is independent of the size of the spacer group. When the spacer group is methyl, the value of β0 (168.1 × 10−30 esu) is the largest in tested electron-donating group. When the spacer group is an electron-withdrawing group, the value of β0 is related to electron-withdrawing ability, and the value of β0 is inversely proportional to the electron-withdrawing ability of the spacer group.

Ferrocene clicked polypyrrole derivatives: effect of spacer group on electrochemical properties and post-polymerization functionalization

In this study, novel ferrocene-functionalized N-alkyl substituted pyrrole derivatives, namely 4-ferrocenyl-1-[3-(pyrrol-1-yl)propyl]-1H-1,2,3-triazole (Py3Fc), 4-ferrocenyl-1-[4-(pyrrol-1-yl)butyl]-1H-1,2,3-triazole (Py4Fc), and 4-ferrocenyl-1-[6-(pyrrol-1-yl)hexyl]-1H-1,2,3-triazole (Py6Fc), were synthesized via click reaction and the monomers were characterized by 1H NMR, 13C NMR, FTIR, and HRMS techniques. Redox properties of the monomers were investigated by cyclic voltammetry (CV) studies. Contrary to general literature, both Py4Fc and Py6Fc were electrochemically polymerized without loss in redox activity of ferrocene group. Moreover, click chemistry was utilized in post-polymerization functionalization. For this purpose, three azide-containing polypyrroles, P(Py3N3), P(Py4N3), and P(Py6N3) were electrochemically synthesized and subjected to click reaction in the presence of ethynylferrocene. CV studies of the post-polymerization functionalized polymers revealed quasi-reversible waves, while only P(Py6-post-Fc) showed the characteristic redox behavior of both polypyrrole and ferrocene. Thus, in this study preparation of a conducting homopolymers of pyrrole having covalently bonded ferrocene units was demonstrated and effect of spacer group is investigated.

Poly(carboxybetaine methacrylamide)-Modified Nanoparticles: A Model System for Studying the Effect of Chain Chemistry on Film Properties, Adsorbed Protein Conformation, and Clot Formation Kinetics

Nonfouling polymer architectures are considered important to the successful implementation of many biomaterials. It is thought that how these polymers induce conformational changes in proteins upon adsorption may dictate the fate of the device being utilized. Herein, oxidized silicon nanoparticles (SiNP) were modified with various forms of poly(carboxybetaine methacrylamide) (PCBMA) for the express purpose of understanding how polymer chemistry affects film hydration, adsorbed protein conformation, and clot formation kinetics. To this end, carboxybetaine monomers differing in intercharge separating spacer groups were synthesized, and nitroxide-mediated free radical polymerization (NMP) was conducted using alkoxyamine initiators with hydrophobic (TEMPO) and hydrophilic (β-phosphonate) terminal groups. The physical properties (surface composition, thickness, grafting density, etc.) of the resulting polymer-SiNP conjugates were quantified using several techniques, including Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and thermogravimetric analysis (TGA). The effect of spacer group on the surface charge density was determined using zeta potential measurements. Three proteins, viz., lysozyme, bovine α-lactalbumin, and human serum albumin, were used to evaluate the effect film properties (charge, hydration, end-group) have on adsorbed protein conformation, as determined by circular dichroism (CD), fluorescence spectroscopy, and fluorescence quenching techniques. Hemocompatibility of these surfaces was observed by measuring clot formation kinetics using the plasma recalcification time assay. It was found that chain chemistry, as opposed to end-group chemistry, was a major determiner for water structure, adsorbed protein conformation, and clotting kinetics. It is thought that the systematic evaluation of how both chain (internal) and end-group (external) polymer properties affect film hydration, protein conformation, and clot formation will provide valuable insight that can be applied to all engineered surfaces for biomedical applications.

Multi‐functional initiator and poly(carboxybetaine methacrylamides) for building biocompatible surfaces using “nitroxide mediated free radical polymerization” strategies

AbstractBiomaterials generally suffer from rapid nonspecific protein adsorption, which initiates many deleterious host responses, and complex chemistries that are employed to facilitate cellular interactions. A chemical approach that, based upon current literature, combines a nonfouling architecture with a biomemtic cell‐adhesive end‐group, is presented. Namely, surface‐initiated polymerization of zwitterionic [poly (carboxybetaine methacrylamide)] brushes, with controlled charge densities and phosphonate head groups. Nitroxide mediated free radical polymerization (NMFRP) was employed for various reasons: reduces presence of potentially cytotoxic organometallic catalysts common in atom transfer radical polymerization (ATRP); and it allows a phosphonate end‐group instead of the common brominated end‐group. Thermally oxidized silicon wafers were covalently functionalized with diethyl‐(1‐(N‐(1‐(3‐(trimethoxysilyl)propylcarbamoyl)ethoxy)‐N‐tert‐butylamino)ethyl)phosphonate. NMFRP was used to graft zwitterionic carboxybetaine methacrylamide monomers of varying inter‐charge separation. The resulting thin films were characterized using Attenuated Total Reflectance‐Fourier Transform Infrared (ATR‐FTIR) and X‐ray photoelectron (XPS) spectroscopy, ellipsometry, water contact angle analysis, and thermo gravimetric analysis (TGA). The effect of spacer group on the surface charge density was determined using zeta potential techniques. It is thought that this stratagem will facilitate the ability to tailor systematically both the interior and terminal polymer properties, providing a platform for further understanding how these conditions affect protein adsorption as well as cell‐surface interactions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Computational Analysis of Adhesion of Primer Ligands to Dentinal Collagen: Effect of Spacer Groups in Ligand and Amino Acid Residue Sequence Differences in Collagen

This study sought to assess by computer modeling the interactions between dentinal collagen and primer monomer ligands used to promote bonding of restorations to tooth. Modeling was carried out both by direct and indirect methods to probe interaction mechanisms. Ligands studied in this investigation conformed chemically to methacrylate phosphates of alkane diol, with changes in the number of methylene spacer groups. Increase in number of methylene groups in the series introduces increasing levels of ligand conformational freedom. An automatic docking program was used to analyze the effect of these changes on primer-collagen interactions in direct (target-based) modeling. The effect of limited modifications of amino acid residue sequences in structural variants of type 1 dentinal collagen was also assessed in this approach. The indirect (ligand-based) modeling used a pharmacaphore search to mimic primer binding to type 1 collagen using a common functional alignment algorithm. Docking energy, and the non-bonded and electrostatic contributions to it, showed statistically highly significant differences (p<0.0001) with ligand conformational freedom. But the effect of collagen composition differences was, although statistically significant (p<0.05), relatively small. Both target-based direct docking and ligand-based indirect modeling visualizations showed that conformations tended to align in a 3-D geometric pattern in bound states, and that the conformational flexibility of the ligands played a critical role in alignment. The results suggest that incorporation of spacer groups in primer monomers may modify dentin bonding to improve overall adhesion under optimum conditions.

Effect of spacer groups on the performance of MCM-41-supported platinum cluster-derived hydrogenation catalysts

MCM-41 was functionalized with (EtO) 3SiCH 2Cl, (MeO) 3SiCH 2CH 2CH 2Cl, and (CH 3)Cl 2SiCH 2Cl. The functionalized materials were characterized by solid-state NMR (CPMAS, 29Si and 13C) and XPS. The NMR data indicate that three new silicon environments were created by (EtO) 3SiCH 2Cl and (MeO) 3SiCH 2CH 2CH 2Cl, whereas with (CH 3)Cl 2SiCH 2Cl, two new silicon environments were obtained. XPS results from Si 2 p core level and the valence band from the material functionalized by (MeO) 3Si(CH 2) 3Cl was found to be the same as that of the corresponding fresh catalyst ( 1a), in contrast to that of the materials functionalized by the other two silane reagents. After further functionalization with triethylamine, these materials were used as inorganic anion exchangers to support the cluster anion [Pt 12(CO) 24] 2−. Solid-state NMR ( 29Si, 13C, 15N) was used to establish the presence of the quaternary ammonium group in the cluster-supported species. Analogous materials were also created using fumed silica as the support, and all of the cluster-supported materials were tested as catalysts for the hydrogenation of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, ethylacetoacetate, 4-nitrotoluene, cyclohexanone, allyl alcohol, and styrene. The best activity was obtained for the catalyst that had MCM-41 as the support and chloropropyl as the spacer group. TEM showed that the supports and the spacer groups had observable effects on the platinum crystallite size of the catalysts.

The effects of spacer groups on the chelation characteristics of some new mannich polymers containing 8-hydroxyquinoline

Two new chelate-forming polymers, poly[8-hydroxyquinoline-5,7-diyl(piperazine- N, N ′-bismethylene)] (Polymer I) and poly[8-hydroxyquinoline-5,7-diyl( N, N ′-dimethylethylenediamine N, N ′-bismethylene)] (Polymer II) were prepared through a Mannich-type condensation of 8-hydroxyquinoline with formaldehyde and piperazine or N, N ′-dimethylethylenediamine, respectively. The chelation properties of these polymers toward the divalent metal-ions, Mg 2+, Ca 2+, Ni 2+, Cu 2+, Zn 2+, and Cd 2+ were studied by a static batch equilibration technique at 25 °C as a function of contact time and pH. Polymers I and II exhibited faster rates of metal-ion uptake and highly improved capacities than their parent phenol–formaldehyde system, poly(8-hydroxyquinoline-5,7-diylmethylene). Polymer I exhibited higher capacities and a more pronounced selectivity towards Cu 2+ than Polymer II. The nature and rigidity of the spacer group was found to play a paramount role in determining the chelation characteristics of the chelating polymer; the use of piperazine as a spacer group was found to considerably enhance the capacity and selectivity of this class of chelating polymers toward divalent metal ions.