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Excessive content of Cu2+ in water is not allowed since it is pathogenic to human beings and most aquatic animals. In this report, to reveal the general colorimetric recognition mechanism of solid-based sensors, containing soft acid coordination ligand types (–COOH, –C=O, –S–) for Cu2+, a series of polyacrylonitrile fibre-based colorimetric sensors (PAN-TEPA-X) with regular precise coordination structures was designed and prepared, where axially symmetric carboxylic acid molecules (X, (CH2)mSn(COOH)2, 3

Herein, we developed a strategy of rational constructing bimetallic metal–organic frameworks (MOFs) and at the same time embedding charges on backbones. Based on the Pearson’s hard/soft acid/base (...

Students’ misconceptions have become phenomenon in teaching and learning, especially in chemistry which is considered as difficult subject. The objective of this study is to identify undergraduate student’s misconception profiles related to acid-base concepts in inorganic chemistry. This test was conducted with 15 item three tier multiple choices test. Data were identified descriptively and qualitatively. This test instruments are judged as valid with CVR score of 0,99 and mean of 1,73. Meanwhile, the reliability for this instrument varies for each tier combination; for tier one only, r11 was given reliability score for 0,93; for combination tier one and tier two, r11 score was 0,90, and for combination of all tiers, r11 score was 0,81. The test conducted revealed that average percentage of misconception in this test is 33.31% for all items. The highest misconception profile is 60,61% in item no.6 hard soft acid base concept. This includes 15,15% misconception false positive, 9,09% misconception false negative, and 36.36% specific misconception.

Most metal-organic frameworks (MOFs) hardly maintain their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, resulting in insufficient stability, therefore limiting their applications. Thus, the design and synthesis of stable size/morphology-controlled MOF nanocrystals is critical but challenging. In this study, dual-ligand and hard-soft-acid-base strategies were used to fabricate a variety of 3D pillared-layer [Ni(thiophene-2,5-dicarboxylate)(4,4′-bipyridine)]n MOF nanocrystals (1D nanofibers, 2D nanosheets and 3D aggregates) with controllable morphology by varying the concentration of 4,4′-bipyridine and thus controlling the crystal growth direction. Owing to the shorter ion diffusion length, enhanced electron/ion transfer and strong interactions between thiophene-2,5-dicarboxylate and 4,4′-bipyridine, the 2D nanosheets showed much larger specific capacitance than 1D nanofibers and 3D aggregates. A single device with an output voltage as high as 3.0 V and exceptional cycling performance (95% of retention after 5000 cycles at 3 mA cm–2) was realized by configuring two aqueous asymmetric supercapacitive devices in series. The excellent cycling property and charge–discharge mechanism are consistent with the hard-soft-acid-base theory.

We provide a general (yet elementary) proof of Pearson’s hard/soft acid/base principle. Contrary to previous attempts to justify this rule, we go beyond the venerable parabolic model of Parr and Pearson. This new treatment encompasses more realistic E versus N dependencies, while emphasizing the importance of the correct normalization of these models.

Thiocyanate anion (SCN–) can coordinate to solid surfaces in various coordination modes, endowing the solid surfaces with different structures and electronic and catalytic properties, but the rules that dictate the coordination preference are poorly understood due to the multiple coordination sites of both SCN– and the solid surfaces as well as the SCN–-lattice mismatch. In this article, extensive density functional theory calculations are performed to study the coordination modes of SCN– on some selected solid surfaces. In particular, the influence of surface stress, coverage, and counter cations is discussed at length. It is found that the time-honored principle of hard soft acid base can only partly account for the preference of sulfur or nitrogen coordination to the solid surfaces due to its failure to treat the Lewis acids and bases located at the borderline and to deal with the multiple coordination sites and the SCN–-lattice mismatch. Specific to solid surfaces, the coordination number and coordina...

Methylimino-di-n-octylacetamide (MIDOA) was used to extract 57 metals from HCl into n-dodecane. MIDOA is a tridentate ligand with one N donor and two carbonyl O donors and can extract soft acid met...

The corrosion characteristics of SUS304 exposed to 0.5 M Cl− aqueous solution containing different metal cations were studied with immersion tests, surface analysis and electrochemical tests. The mechanism of corrosion with metal cations was clarified by the XPS analysis results together with the hard and soft acid and base (HSAB) concept and the passive films structure. It is supposed that metal cations with large hardness make a layer by chemical bonding with the passive films. The passive films are protected by the metal cation layer from Cl− attack, and consequently corrosion reactions are inhibited.

Thirty years ago, Parr and Yang postulated that favorable chemical processes are associated with large changes in the electronic chemical potential or, equivalently, the electronegativity. They called this the "|Δμ| big is good" rule and noted that if the rule could be justified, then it "would constitute a validation of frontier theory from first principles." We provide a simple and insightful justification for the "|Δμ| big is good" rule, with special emphasis on electron-transfer reactions. Furthermore, we show that it implies Pearson's hard/soft acid/base principle mathematically and confirm this result with numerical examples. This supports Parr's intuition that many other reactivity precepts arise as corollaries to the more fundamental "|Δμ| big is good" rule. In all of this, it is essential to consider the intensive nature of the chemical potential.

‘Double displacement reactions’ are commonly observed in solutions and aqueous phase. They are less common in solid phase and generally requires high temperature to take place. However, in this article, we report double displacement reactions taking place in solid phase at room temperature. We also highlight the criteria required for the occurrence of displacement reactions in solid state at room temperature. The driving force for all the double displacement reactions is explained using Pearson’s hard and soft acid and base (HSAB) concept, and in few cases involvement or aid of water of hydration is observed.

Bioligands (BL) present in plant and microbes are primarily responsible for their use in metal decontamination. Both primary (proteins and amino acid) and secondary (proliferated) response in the form of BL is possible in plants and microbes toward metal bioremediation. Structure of these BL have specific requirement for preferential binding towards a particular metal in biomass. The aim of this review is to explore various templates from BL (as metal host) for the metal detoxification/decontamination and associated bioremediation. Mechanistic explanation for bioremediation may involve the various processes like: (i) electron transfer; (ii) translocation; and (iii) coordination number variation. HSAB (hard and soft acid and base) concept can act as guiding principle for many such processes. It is possible to investigate various structural homolog of BL (similar to secondary response in living stage) for the possible improvement in bioremediation process.

Novel applications of nanotechnology may lead to the release of engineered nanoparticles (ENPs), which result in concerns over their potential environmental hazardous impact. It is essential for the research workers to be able to quantitatively characterise ENPs in the environment and subsequently to assist the risk assessment of the ENPs. This study hence explored the application of nanoparticle tracking system (NTA) to quantitatively describe the behaviour of the ENPs in natural sediment-water systems. The NTA allows the measurement of both particle number concentration (PNC) and particle size distribution (PSD) of the ENPs. The developed NTA method was applied to a range of gold and magnetite ENPs with a selection of surface properties. The results showed that the positively-charged ENPs interacted more strongly with the sediment than neutral and negatively-charged ENPs. It was also found that the citrate coated Au ENPs had a higher distribution percentage (53%) than 11-mercaptoundecanoic acid coated Au ENPs (20%) and citrate coated magnetite ENPs (21%). The principles of the electrostatic interactions between hard (and soft) acids and bases (HSAB) are used to explain such behaviours; the hard base coating (i.e. citrate ions) will interact more strongly with hard acid (i.e. magnetite) than soft acid (i.e. gold). The results indicate that NTA is a complementary method to existing approaches to characterise the fate and behaviour of ENPs in natural sediment.

We use a soft-approach for synthesis of quasi-spherical, ultra-small, digestively-ripened, stable copper oxide QDs (radius

A new extractant biuret(C8) is synthesized and tested for solvent extraction of hard acid metals, for example, actinides, and soft acid metals. This compound has a central frame similar to that of malonamide but with an additional amino functional group introduced into the central framework; in this case, both the amidic oxygen atoms and the amino nitrogen atom may bond with metals. We found that both hard and soft acid metals can be extracted from nitric or perchloric acids to n-dodecane using biuret(C8). It is clear that D(Pd, Pu, U) values of approximately 100 can be obtained using 0.1 M biuret(C8)/n-dodecane.

Cation exchange in Metal-Organic Frameworks (MOFs) is an emerging synthetic pathway for modifying chemical compositions and has been expansively investigated. It has been shown to be an important tool for leveraging novel functional MOFs that otherwise have not been achieved via the conventional technique. Yet, the governing physical and chemical factors responsible for this occurrence are not clearly understood. The most encountered interpretations are related with the presence of open metal sites, coordinated solvent or lattice distortion tolerance. There is no unifying concept that gives a detailed insight on some common observations in cation exchanged MOFs, e.g. why some MOFs can undergo complete and reversible cation exchange, complete but irreversible, partial exchange, and in some cases, they do not exchange. Other puzzles include, why certain cation can exchange others while some cannot, why exchange can proceed in certain solvents but fails in others. Herein, we qualitatively demonstrate how the concept of Hard-Soft Acid-Base principle allows a plethora of reported experimental observations dealing with cation exchange at the SBUs of MOFs could be reasonably explained. This review is intended to provide rationalization of cation exchange behaviors in both stable and labile MOFs, based on the hardness or softness of cations and ligands, effect of solvents, temperature and exchange period using the HSAB principle’s point of view. We hope that this review may lead to a deeper understanding of the cation exchange behavior in MOFs, which in turns allow chemists to use it as a predictive tool for engineering novel functional MOFs with the required complexities.

We provide a new proof for Pearson’s hard/soft acid/base (HSAB) principle. Unlike alternative proofs, we do not presuppose a simplified parabolic dependence on the energy of the system with respect to changes in its number of electrons. Instead, we use the more physically grounded finite-temperature formulation of the grand-canonical ensemble. We show that under the usual assumptions regarding the chemical potentials and hardnesses of the involved species, the HSAB rule holds for a wide range of temperatures.

Kariesh cheese is a highly nutritive soft acid cheese made from naturally fermented skimmed milk, mainly manufactured at home by small holders and sold at local markets. Due to unhygienic condition during manufacturing and low quality raw milk, many outbreaks of human brucellosis were reported. This study was done to evaluate the use of acetic and citric acids, as natural organic acids, to produce kariesh cheese instead of the traditional method to control Brucella infection. Sensory evaluation revealed that all treatments didn't differ (P>0.05) than control except 2% citric acid which characterized to a little extent by lemon flavor, crudeness body and texture and less whiter color than other treatments. B. meletensis strains didn’t affected by acetic (1%) or citric (1.5%) acids, but both of them were completely inhibited by acetic (1.5%), or have 4 log reduction by citric (2%) acids. For B. abortus thefield and S19 strains were completely inhibited by 1% acetic acid, but citric acid 2% significantly (P

The general-purpose reactivity indicator (GPRI) is utilized to discern the reactive sites of the phenylsulfinate ion, PhSO 2 - , both in isolation and with a sodium counterion. While some approaches based on the hard/soft acid/base (HSAB) principle fail to indicate that the oxygens are the hard (electrostatic) sites of the molecule and that the sulfur is the soft (electron-transfer) site of phenylsufinate, the GPRI succeeds. A computer code, written in Fortran, that computes the general-purpose reactivity indicator is released in the supplementary information .

•The fluorescence intensity of ZnSe QDs could be quenched by Cu2+.•Foreign ions showed insignificantly effect on the use of QDs as Cu2+ probe.•The quenching mechanism was discussed to be a static quenching procedure.•The static quenching was explained by the strong affinity from soft acid and base.

Multiple orthogonal coordinative interactions were utilized to construct heterometal-decorated tetrahedral cages from in situ formed trinuclear ZrIV clusters through the combination with other metal ions such as CuII or PdII . Through effective use of the hard/soft acid/base principle, the orthogonal self-assembly process of Zr-bpydc-CuCl2 (H2 bpydc=2,2-bipyridine-5,5-dicarboxylic acid) can be finely controlled using three strategies: post-synthetic metallization, a stepwise metalloligand approach, or a one-pot reaction.

This review covers synthetic work carried out in the field of stilbene and oligostilbene chemistry. It includes a brief overview of the methods used for the synthesis of monomeric stilbenoids. The production of oligomeric species by means of enzymatic or micro- bial conversion is examined in detail. Biomimetic syntheses of stilbene oligomers are then scrutinised. Most of the work is based on the dimerisation of stilbenoid monomers with help of one-electron oxidants or through acid catalysis. Mechanistic interpretations of the oxi- dative couplings observed by the various groups are proposed and suggest that the outcome of these reaction be guided by the "hard and soft acid and base" (HSAB) principle together with supramolecular interactions between the reacting stilbenoid monomers. Eventually, the few non-biomimetic full syntheses are presented and their strategies analysed.

Digestive ripening is an efficient method that leads to monodispersed nanoparticles from polydispersed ones. A systematic investigation of digestive ripening with different agents viz. dodecanethiol and dodecylamine on different metallic systems is presented. It is shown that both the metallic system involved and the digestive ripening agent have influences on the final size distribution. Further, it is demonstrated that the interaction strength between the different metals and the digestive ripening agents based on Hard Soft Acid Base principles could be invoked to explain the variation in nanoparticle size.

In this article, we present a chemoaffinity-mediated synthetic strategy toward trivalent rare earth (RE) sulfides-based nanocrystals with poor affinity between cation and anion (i.e., RE(3+) and S(2-)). With the affinity mediation among multiple constituents based on hard and soft acid and base theory, we synthesized a series of monodisperse NaRES(2) nanocrystals (RE = La to Lu, Y). The revelation of the nanocrystal growth mechanism from both experimental evidence and crystal structure modeling has enabled a robust control over the sizes and morphologies of the nanocrystals. This principle of chemoaffinity has also promised the synthesis of well-defined but even more complex RE-based hetero-nanostructures (i.e. NaLaS(2)-Au, Au@NaLaS(2), NaLaS(2)@Ag(2)S, Au@NaLaS(2)@Ag(2)S) with tunable optical properties. Furthermore, this synthetic method has yielded durable NaCeS(2)-based red nano-pigments under ambient conditions, with superior brightness and permeability in polydimethylsiloxane.

Three novel supramolecules of the Ag(I) complexes of [Ag4(pyapa)4(SO4)2 · 6H2O]n, 1, {[Ag2(pyapa)2][ClO4]2}n, 2 and {[Ag2(pyapa)2(H2O)][NO3]2}n, 3, (pyapa = 1-(2-pyrazinyl)piperazine) have been prepared by self-assembly of Ag(I) salts with 1-(2-pyrazinyl)piperazine (pyapa) in MeOH/H2O system. The IR, TGA and elemental analysis have been recorded and all the complexes have been structurally characterized by X-ray crystallography confirming that complexes 1–3 are one-dimensional coordination polymers. The pyapa ligands in complexes 1–3 bind soft acid Ag(I) ions through the pyrazinyl and piperazinyl groups forming the 1-D polymeric chains. The anions SO 4 2 in complexes 1 shows the disordered geometries and bridging the Ag(I) atoms, while the anions ClO 4 - and NO 3 - in complexes 2–3 are not coordinated to the Ag(I) atoms, and all of them play an important roles in linking cationic chains into 3-D supramolecular structures. Thermal gravimetric analyses (TGA) were carried out to investigate their thermal properties.

The present study evaluated the use of nisin as an antimicrobial treatment for shelf-life extension of Galotyri, a Greek soft acid-curd cheese, stored aerobically under refrigeration for a period of 42 days. Three different treatments were tested: N0, control sample with no nisin added; N1, 50 IU g −1 nisin; and N2, 150 IU g −1 nisin, the latter two treatments added post-production to the Galotyri cheese. Of all microorganisms enumerated, lactobacilli, lactococci and yeasts were the groups that prevailed in cheese samples, irrespective of antimicrobial treatment. Based primarily on sensory evaluation (appearance and taste) and a microbiological acceptability limit for yeasts (5 log cfu g −1 ), the use of nisin treatments extended the shelf-life of fresh Galotyri cheese stored at 4 °C by ca. 7 days (N1) and 21 days (N2) with cheese maintaining good sensory characteristics.

Low temperature Raman spectroscopic measurements on silver nitroprusside (AgNP), Ag-2Fe(CN)(5)NO] powders display reversible features of a partially converted metastable state. The results are compared with similarly observed metastable state in case of sodium nitroprusside (NaNP) and the differences have been discussed in terms of possible resistance to metastable state formation offered by silver atoms on the basis of hard soft acid base (HSAB) theory.

Mercury(II) complexes with 4,4′-bipyridine (4,4′-bipy) ligand were synthesized and characterized by elemental analysis, and IR, 1H- and 13C-NMR spectroscopy. The structures of the complexes [Hg3(4,4′-bipy)2(CH3COO)2(SCN)4]n (1), [Hg5(4,4′-bipy)5(SCN)10]n (2), [Hg2(4,4′-bipy)2(CH3COO)2]n(ClO4)2n (3), and [Hg(4,4′-bipy)I2]n (4) were determined by X-ray crystallography. The single-crystal X-ray data show that 2 and 4 are one-dimensional zigzag polymers with four-coordinate Hg-atoms, whereas 1 is a one-dimensional helical chain with two four-coordinate and one six-coordinate Hg-atom. Complex 3 is a two-dimensional polymer with a five-coordinate Hg-atom. These results show the capacity of the Hg-ion to act as a soft acid that is capable to form compounds with coordination numbers four, five, and six and consequently to produce different forms of coordination polymers, containing one- and two-dimensional networks.

In this work, we have elucidated the regioselectivity in some Diels–Alder reactions essentially by means of the Hard and Soft Acid Base principle applied locally. On the basis of the Gazquez–Mendez conclusions, we calculated the condensed local softnesses for the terminal atoms in order to show the preferential cyclization mode of these reactions. The results obtained with the B3LYP/6-31G* method confirm the ortho regioselectivity observed experimentally. The regioselectivity of these reactions has also been confirmed by the calculation of the activation energies and by the application of the Houk rule.

The present paper addresses the stability of Lewis acid−base complexes using the recently developed local hard−soft acid−base (HSAB) principle. The principal role of electronegativity equalization and the charge redistribution process in stabilizing the complexes is demonstrated. The soft−soft and hard−hard types of interactions are well distinguished by the electron transfer parameter. The effect of correlation on the reactivity descriptors and subsequently on the soft−soft as well as hard−hard interactions has been studied. The validity of the present model in calculating the interaction energy of these complexes with varying degrees of strength is demonstrated.

In this paper, we have presented a detailed study of a local hard−soft acid−base (HSAB) principle for describing multiple-site interactions between the molecular systems. The local HSAB principle, which has been recently used to study single-site based interactions, can be generalized for the description of multiple-site-based interactions by different ways. We have elaborated these approaches and showed the validity of these models by making a detailed study on model prototype interactions that are relevant to biological molecular interaction processes. We discuss the nature of these approaches and the domain of their applicability.

This paper introduces the Hard Soft Acid Base (HSAB) concept as a promising tool for the selection of gas sensing layers. Target gas molecule — sensitive layer tandems are discussed and interpreted in the terms of this theory. Sensing layers suitable for carbon dioxide, nitrogen dioxide, sulphur dioxide, and hydrogen sulphide detection are presented and classified according to this concept. For oxygen and mineral acids detection, an indirect HSAB approach is discussed. The paper explains how the HSAB principle can be useful in designing gas sensing layers for different types of sensing structures, such as: surface acoustic waves (SAW), colorimetric, chemoresistive, etc.