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beta-Diketones are an important class of bidentate cyclometalating compounds, used in organometallic chemistry as ancillary ligands because of their wide commercial availability and easy synthesis. They are employed to finely tune the electronic, spectroscopic and physical properties of metal complexes. Heteroleptic iridium complexes often benefit from the use of -diketonate ligands, their properties being similar to those of the corresponding homoleptic tris-cyclometalated ones. Nevertheless, in some cases, their use results in a complete quenching of the phosphorescence. Aiming to understand the origin of this drawback, we designed a suitable class of heteroleptic complexes and studied their thermal stability (DSC/TGA). We explored the effect of the ancillary ligand in a series of Ir(iii) complexes bearing 2-phenylpyridine (ppy) as a cyclometalated ligand and acac (acetylacetonate), tta (2-thienoyltrifluoroacetonate), dtdk (1,3-di(thiophen-2-yl)propane-1,3-dionate) and BPhen (4,7-diphenyl-1,10-phenanthroline) as ancillary ligands. Through photochemical and electrochemical investigations, whose results agree with and support our density functional theory calculations, we demonstrate that -diketonate ligands with low triplet energy generate dark triplet excited states with negligible coupling to the ground state which indeed promote non-radiative relaxation through population of higher states.

Following the IUPAC-endorsed procedure, the primary pH standards offered by the equimolal phosphate buffer (Na2HPO4 (0.01 mol⋅kg−1) + KH2PO4 (0.01 mol⋅kg−1)) in the (N-methyl-2-pyrrolidinone + water) solvent mixture of 50 mass percent composition at various temperatures have been determined from potential difference measurements with the reversible Harned cell. Since the essential prerequisite of the above procedure is the knowledge of the (hitherto unknown) standard potential difference of Harned’s cell, a parallel supplementary series of potential difference measurements has been carried out with the reversible cell, Pt|H2|HCl(m)|AgCl|Ag|Pt according to the classical thermodynamic procedure. The problem of comparability of the pH scale in the (N-methyl-2-pyrrolidinone + water) solvent with that in the pure water solvent is duly discussed in terms of primary medium effects.

In the Atom Transfer Radical Polymerization (ATRP) technique, the suggested polymerization scheme is pivoted by a metal complex acting as a redox catalyst able to coordinate with the incipient radicals. The development of an a priori criterion of choice of the best (complex + solvent) combination is one of the current topics in this field. In this context we performed polarographic investigations on copper complexes with multidentate amino ligands (TMEDA and Me6TREN, plus acetonitrile as a reference) in water and in water + acetonitrile mixed solvents. In the latter case we took into account the competition between the co-solvent acetonitrile [a weaker ligand, but concentrated, selectively stabilizing Cu(I)], and the polyamine [a stronger ligand, but diluted, preferentially stabilizing Cu(II)], achieving further stabilization of the complexed copper, with a narrow potential range of stability as Cu(I), which is modulated through the acetonitrile/polyamine ratio. An interpretative scheme is presented.

An advantageous procedure is developed, allowing preparation of electrodeposited silver electrodes of highly controlled polycrystalline surface (characterized by both electrochemical techniques and SEM), to be employed as cathodes for interphase and electrocatalysis studies. Such electrodes, tested in halide adsorption experiments in parallel with the more demanding single-crystal and polycrystalline silver rod ones, acting as a reference, perform competitively in terms of both reproducibility and stability. The same experiments allow further evaluation of the surface roughness factors of the electrodeposited silver electrodes, based on (i) the Parsons–Zobel criterion and (ii) the comparison of their capacitance minima with those of the (110) single-crystal ones, both approaches resulting in very good agreement with the standard UPD and capacitive methods.

Determination of primary standards for pH measurements in glycerol + water solventmixtures has been carried out based on reversible emf measurements of the cellPt|H2|KHPh (m PS) + KCl (m Cl)|AgCl|Ag|Ptwhere KHPh denotes the potassium hydrogen phthalate buffer solution of molalitym PS = 0.05 mol-kg−1, at glycerol mass fractions w G = 0.2 and 0.4, within thetemperature range −10 to 40°C. A multilinear regression procedure as a functionof electrolyte molality, glycerol mass fraction w G, and temperature T has beenapplied for the data processing leading to the values of primary standards pHPS.These can be represented by the following regression equationpHPS = (4.007037±0.001113) + (3.55844±0.01776)x G+(0.39622±0.01410)z + (4.3084±0.3377)z 2− (50.66±10.53)x G z 2 + (457.10±78.48)x G 2 z 2where z = (T − 298.15)/298.15. Parallel values of the first ionization constantof o-phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid, the parent acid of KHPh),which are essential for the above calculations, have been determined fromreversible emf measurements of the cellPt|H2|H2Ph (m 1) + KHPh (m 2) + KCl (m 3)|AgCl|Ag|Ptover the range of solvent composition and temperatures mentioned above.

The electromotive forces (emf) E A and E C of the following concentration cells with transference: $${\text{Ag}}\left| {{\text{AgCl}}} \right|{\text{KCl (}}m_2 {\text{)}}\left\| {{\text{KCl(}}m_1 {\text{)}}\left| {{\text{AgCl}}} \right|{\text{Ag and K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} |{\text{KCl(}}m_1 {\text{)}}} \right\|{\text{KCl(}}m_2 {\text{)|K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} ,$$ respectively, together with the emfs E MAX of the corresponding double cell without transference: $${\text{K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} \left| {{\text{KCl(}}m_1 {\text{)}}} \right|{\text{AgCl}}\left| {{\text{Ag}} - {\text{Ag}}} \right|{\text{AgCl}}\left| {{\text{KCl(}}m_2 {\text{)}}} \right|{\text{K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} $$ have been measured at KCl molalities m (m 1 fixed and m 2 varied, with m 2>m 1) approximately up to the KCl solubility limit in 12 solvent mixtures for the three aqueous–organic solvent systems (ethylene glycol+water), (acetonitrile + water), and (1,4-dioxane + water) up to 0.8 mass fraction of organic component. For all the cases explored, the E A vs. E MAX relation is linear over the whole KCl molality range. The ionic transference numbers t of KCl determined therefrom show a curvilinear dependence on the mass fraction of the organic component of the relevant solvent mixture and are found to fall in the range 0.52–0.48, viz., within ±4% of exact equitransference (t + = t − = 0.5). In particular, KCl becomes exactly equitransferent (i.e., an ideal salt bridge) in aqueous mixtures with the following mass fractions of organic component: 0.4 ethylene glycol and 0.09 acetonitrile, as well as 0.12 methanol, and 0.08 and 0.34 ethanol from our recent work. Even if use of KCl as a salt bridge would be somewhat restricted by its limited solubility in high mass fractions of dioxane and acetonitrile and pending extension of investigation to other mixed-solvent systems, the above figures characterize KCl as a fairly good “intersolvental” salt bridge in electrochemistry, electroanalysis, and corrosion science.

Characterization of an Avicel PH 102 MCC powder through polymerization degree determination, X‐ray diffraction and N2 adsorptions at subcritical temperatures is described. Specific characterizations of MCC/H2O exchange in different environments were performed by means of thermogravimetric weight losses on time/temperature scale and analyses of water adsorption/absorption from saturated vapors at 310 K. The reversibility of MCC/H2O interactions and the influence of different ‘surface area probes’ on the specific surface area are discussed.

Electromotive forces (emf) were measured in the transference cells: Ag∣AgCl∣- Nacl (m2) in Z∥ NaCl (m1) in Z∣AgCl∣Ag and NaxHg1-x∣NaCl (m1) in Z∥ NaCl (m2) in Z∣NaxHg1-x (where NaxHg1-x denotes a flowing Na–amalgam electrode and Z an aqueous-organic solvent mixture) at various molalities m2 > m1 of NaCl in Z = (ethylene glycol + water), (acetonitrile + water) and (1,4-dioxane + water), with mass fractions of the organic components ≤0.8. The transference number of Na+ in (ethylene glycol + water) and (1,4-dioxane + water) varies little with respect to that in pure water medium, whereas in (acetonitrile + water) it increases remarkably with increasing proportion of acetonitrile so as to approach equitransference, behavior similar to that previously found in (methanol + water) and in (ethanol + water). At acetonitrile mass fraction 0.6 NaCl is sufficiently close to equitransference to emerge as a useful salt bridge, nearly at the same level as the popular aqueous KCl.

To make the (Pb)Hg‖PbSO4‖SO 4 2− electrode really usable and attractive for extensive application to thermodynamic studies, a new, simplified design and a convenient preparative procedure have been introduced, ensuring stable amalgams and reproducible electrode potentials. The electrode so prepared has been exhaustively characterized both thermodynamically and as a SO 4 2− -sensing electrode, in different sulfate solutions, including H2SO4. The past discrepancies of standard potentials-mainly due to preparation and/or handling problems-are discussed and, for a final resolution of the question, a practical standardization procedure is proposed.

The electromotive force of the amalgam cell {NaxHg1-x‖NaCl(m)‖AgCl‖Ag} has been measured at 25°C as a function of the mole fraction x of Na in amalgams and of the molality m of NaCl in (ethylene glycol + water), (acetonitrile + water), and (1,4-dioxane + water) mixed solvents, containing up to 0.8 mass fraction of the organic component, with relative permittivities e ≥ 27. The relevant standard molal electromotive forces \(E_{\text{m}}^ \circ \) have been determined, together with the mean molal activity coefficient γ± of NaCl as a function of its molality. In the case of (ethylene glycol + water) mixtures, a linear dependence of \(E_{\text{m}}^ \circ \) on the mass fraction of ethylene glycol is observed, which is quite unusual, The Debye-Huckel equation is applicable successfully over the whole range of molalities explored, which extends to the vicinity of the solubility limit of NaCl in each solvent. The dependence of the standard emf on the logarithm of the volume fraction of water in the aqueous-organic solvent mixtures have been analyzed in terms of Feakins and French's theory, leading to a primary hydration number 7.2 for NaCl, in good agreement with previous results employing different methods.

From reversible emf measurements of the cell Pt/H2/KHPh+KCl/AgCl/Ag/Pt, reference value pH-metric standards, pHRVS, for 0.05 mol-kg−1 potassium hydrogenphthalate (KHPh) reference buffer solutions in 20, 50, and 80 wt % methylcellosolve (2-methoxyethanol, CH3O-CH2CH2OH)-water solvent mixtures from −10 to +45°C, have been determined in compliance with the criteria endorsed by IUPAC. The corresponding values of the first ionization constant ofo-phthalic acid (H2Ph, benzene-1,2-dicarboxylic acid), which is a key quantity for the acquisition of pHRVS standards, have been determined from emf measurements of the reversible cell Pt/H2/H2Ph+KHPh+KCl/AgCl/Ag/Pt.

Ion-transfer parameters of aqueous hydrochloric acid over a wide molality range have been re-investigated taking the concurrent solventtransfer into due account. In this context, the transference numbers for the hydrogen ion τH and for water τw have been determined from 10−2 to 15 mol-kg−1, together with the corresponding infinite-dilution values τHo and τwo, by processing a set of nearly a hundred emf measurements (some twenty of them new for this work) on HCl concentration cells with transference with both cation-reversible and anion-reversible electrode pairs.

A unified treatment of liquid junction potentials and membrane potentials which accounts for both ionic and solvent transfers at homoionic junctions between ultra concentrated electrolyte solutions, also in terms of the primary hydration parameters and the Stokes-Robinson hydration theory, is described. Application to the determination of cation transference numbers, τ+, water transference numbers, τw, and primary hydration numbers,h, is described as a rational scheme for characterization of concentrated electrolytes as possible new salt bridges for the minimization of liquid junction potentials in electroanalysis. Examples of application of this scheme are presented based on multiple regression analysis of electromotive force measurements of such homoionic concentration cell as Ir | Cl2 | HCl (m 2) ‖ HCl (m 1) | Cl2 | Ir and Hg | Hg2SO4 | Li2SO4 (m 2) ‖ Li2SO4 (m 1) | Hg2SO4 | Hg, with fixedm 1 molality and variedm 2 molality. Based on the electromotive force of analogous homoionic transference cells but with interposed membranes, application of the present procedure can be extended to the determination of ion and solvent transport parameters, notably the degree of permselectivity, of membranes for use either as selective sensors in electroanalysis or selective separators in industrial electrochemistry.

Five strong aqueous binary electrolytes — one symmetrical (CsCl) and four unsymmetrical (Li2SO4, K2SO4, Rb2SO4, Cs2SO4) — have been examined, for possible use as salt bridges for the minimization of liquid junction potentials (EL), up to the highest concentrations practicable, by the method of homoionic transference cells: Pt−Ir | Cl2 | CsCl (m2) ‖ CsCl (m1) | Cl2 | Pt−Ir and Hg | Hg2Cl2 | CsCl (m2) ‖ CsCl (m1) | Hg2Cl2 | Hg for CsCl, and Hg | Hg2SO4 | Me2SO4 (m2) ‖ Me2SO4 (m1) | Hg2SO4 | Hg for the Me2SO4 sulphates where Me=Li, K, Rb and Cs. CsCl, K2SO4, Rb2SO4, and Cs2SO4, prove to belong to the class obeying close equality of transference numbers for their ions, that is,t+= |t−|=0.5, over the whole concentration range (namely, from infinite dilution up to saturation). This result qualifies aqueous CsCl as an unrivalled salt bridge, whose equitransference is obeyed more stringently than any other salt. This is now demonstrated experimentally over the whole molality range, the saturation molality being as high as 11.30 mol kg−1 at 25°C. The observed propertyt+=|t−|=0.5 excludes K2SO4, Rb2SO4, and Cs2SO4, as possible salt bridges because the equitransference conditions for minimization ofEL's are τ+ = |τ−| = l/(z+ + |z−|) = 0.333, i.e.,t+=0.333 andt−=2t+=0.667. Finally, Li2SO4, though behaving quite differently from the other three sulphates studied, does not sufficiently approach the required conditions, contrary to what one might have hoped from its known infinite-dilution transference numbers.

From emf E measurements of the reversible cell $$Pt|H_2 (g,1 atm)|HCl(m)|AgCl|Pt$$ at 0.01