Volume 80, Issue 7

This issue of Pure and Applied Chemistry is based on plenary lectures delivered at the International Conference on Modern Physical Chemistry for Advanced Materials (MPC '07), which took place 26-30 June 2007 in Kharkiv, Ukraine. The Conference was sponsored by IUPAC and the European Association for Chemical and Molecular Sciences, and organized by V. N. Karazin Kharkiv National University in cooperation with L. M. Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry of the National Academy of Sciences of Ukraine (Donetsk, Ukraine) and the Physical Chemistry Department of the Ukrainian Chemical Society. Christian Amatore (Academy of Sciences of France) and Anatoliy Popov (National Academy of Sciences of Ukraine) were Chairmen of the International Scientific Committee and the International Organizing Committee, respectively. Professors Yuriy Kholin and Valentin Lebed (Kharkiv National University) headed the Local Organizing Committee and the Program Committee. The aim of the Conference was to review the physicochemical foundations of modern materials science and technology. At the same time, the event offered opportunities for Ukrainian physical chemists to strengthen international ties and collaboration, and to evaluate the status of modern physical chemistry in Ukraine against global criteria. A total of 170 active delegates from 23 countries participated in the scientific program, which provided a showcase for the achievements, both of internationally recognized experts and enthusiastic young researchers, all of whom contributed constructively to lively scientific discussions. The Conference was dedicated to the centenary of the birth of the outstanding physicochemist Prof. Nikolai Izmailov (1907-1961). On 26 June, just before the opening of the Conference, the book Scientific Heritage of N. A. Izmailov and Topical Problems of Physical Chemistry was ceremonially presented to the academic community and the media in the Kharkiv National University Museum. The majority of the 19 plenary lectures were devoted to nanoscience, supramolecular chemistry, self-assembled systems, and organized solutions. The papers collected in this issue are arranged in order of their presentation during the scientific proceedings; lectures on chromatography, delivered by Profs. V. P. Georgiyevskiy (Ukraine), V. G. Berezkin (Russia), and E. Tyihák (Hungary), will be published in the Journal of Planar Chromatography and in other journals. The program also included 46 keynote and oral presentations and 120 posters, which were distributed among symposia devoted to the following topics: chromatography, materials science, solution chemistry, theoretical chemistry, electrochemistry, kinetics and catalysis, and photochemistry. The social program included a classical music concert, welcome party, conference reception, visit to the Museum of Arts, bus excursion to the museum of the great Russian painter Il'ya Repin in Chuguev, and numerous local activities. On 25 June, an all-day excursion to the typical Ukrainian city Poltava provided an opportunity to visit the famous battlefield where the army of Tsar Peter I of Russia achieved a decisive victory over the invading forces of King Charles XII of Sweden in 1709. Nikolay Mchedlov-Petrossyan Conference Editor

The International Conference on Modern Physical Chemistry for Advanced Materials was organized primarily to commemorate the centenary of the birth of Prof. Nikolai Izmailov and to pay tribute to his scientific achievements and legacy. Nikolai Arkadievich Izmailov was born in Sukhumi, in the southern region of the Russian Empire, on 22 June 1907. After his family moved to Kharkov (in Ukrainian: Kharkiv), he developed an early interest in chemistry and eventually enrolled as a Ph.D. student at Kharkov State University (at that time, it was called the Kharkov Institute of Public Education) in 1928. He initially conducted research into sorption of gases, under the guidance of Prof. Kosakevitch. Thereafter, he investigated the influence of salts on adsorption of organic molecules on water/air interface. He received his Ph.D. in 1937. From 1934, conducting his research at the University, he started a joint appointment at Kharkov Pharmaceutical Research Institute, and his independent scientific interests developed along two main directions, namely, static and dynamic properties of sorption from solutions and the influence of the solvent on dissociation of electrolytes. It was here that he collaborated with Maria Shraiber to introduce the "drop-chromatographic method" in 1938, which later became known as thin layer chromatography (TLC). This finding is widely recognized and acclaimed, and continues to play an essential role in everyday laboratory practice. At a time when one of the most promising methods of drug analysis was titrimetry, and in the course of his work at the Pharmaceutical Institute, Izmailov also became interested in using nonaqueous solvents for this purpose. He recognized that water is the most atypical of solvents, and tried to rationalize the origin of the then-novel concept of the differentiating influence of organic solvents on acid-base properties. Throughout the 1930s, Izmailov investigated the possibility of employing indicator electrodes, especially glass electrodes, in organic solvents. In 1944, Izmailov headed the Department of Physical Chemistry at the University. In his Sc.D. dissertation presented in 1948, as well as in his publications during the 1950s, he proposed a scheme of dissociation of electrolytes in solutions, which is recognized as probably the most complete. The main point, in respect to acids, was based on the idea of improving the fundamental but somewhat schematic Brønsted's theory, by considering solvation of all the equilibrium species. Just this viewpoint rationalized the differentiating action of solvents on the strength of acids (i.e., unequal changes in their dissociation constants). A seminal review published in 1950 bore the title of his dissertation, "The influence of solvents on the strength of acids", and presented a comprehensive and lucid classification of nonaqueous solvents according to the character of their levelling and differentiating influence on acids strength. He proposed the following groupings of solvents: (i) amphoteric, such as water and alcohols; (ii) mixtures of alcohols and dioxane with water; (iii) acidic solvents, such as formic, acetic, propionic acids, sulfuric acid and its mixtures with water, and liquid hydrogen halides; (iv) basic solvents, such as ammonia, hydrazine, pyridine, etc.; (v) aprotic solvents: benzene, chlorobenzene, etc.; (vi) "differentiating" solvents. The latter category, exemplified by nitriles, nitro compounds, aldehydes, ketones, and amides, had by then been known to differentiate strength of salts due to Walden's papers. Izmailov significantly elaborated this concept and adapted it to acids and bases, taking into consideration solvation effects. In fact, this significant group of solvents (vi) is now known as dipolar aprotic (A. Parker) or dipolar non-hydrogen-bond donor (HBD) solvents (F. Bordwell). In order to interpret the p K a shifts, the transfer activity coefficients of ions were divided into two parts. As a result, a general equation was proposed for the difference between the pKa in the organic solvent and in water, which included both the so-called Born term, already used by Brønsted, and the item reflecting other solvation effects. Actually, this was a unification of electrostatic approaches (Brønsted, Wynne-Jones, Gurney) and "chemical" theory of solvation (in the spirit of Mendeleyev and Kablukov). This was a decisive step toward the understanding of the multiplicity of solvent effects. In order to reveal the peculiarities of solvation of molecules, Izmailov compared interaction between acids (carboxylic acids and phenols) and alcohols on the one hand and ketones, nitriles, etc., on the other, using the "inert" solvents as media. Besides, Izmailov underlined the significance of degree of charge delocalization in conjugated anions (i.e., carboxylate and phenolate) with respect to alterations in the strength of corresponding acids in organic solvents; later, such ideas grew very popular. These concepts enabled the different changes in dissociation constants of acids belonging to the same "charge type" to be rationalized, but to different "chemical types" on going from water to organic solvents, despite Brønsted's theory, a general effect that had already been stressed by Verhoek. In Izmailov's scheme of electrolytic dissociation, the possibility of the existence of ion pairs between solvated proton and anion of the acid was foreseen. Indeed, he had even alluded to this in his dissertation completed in 1947. Accordingly, for dissociation of salts CA, the scheme not only took into account solvated species (C + A - ) solv , free solvated ions C + solv , and A solv , but postulated also associates of solvated ions, C + solv A solv . The latter can be considered as a prototype of the so-called solvent-separated, or loose, or long ion pairs C + //A - . Izmailov and his associates continued studying acids, bases, and salts in alcohols, polar and nonpolar aprotic (non-HBD) solvents, acidic and basic solvents, mainly by potentiometry; the results of their exhaustive research were presented in a vast series of papers under the title "Thermodynamic properties of electrolytes in nonaqueous solutions" published in the Russian Journal of Physical Chemistry , as well as in other publications. Izmailov proposed several new methods for estimating activity coefficients of ion transfer from water to nonaqueous solvents and Gibbs energy of ion solvation and generalized the concept of unique (unified) acidity scale in different solvents. The most monumental of Izmailov's contributions was the treatise "Electrochemistry of solvents", which was published in Russian in 1959. Most of the original sections of this voluminous 958-page work, devoted to the detailed scheme of electrolytic dissociation, differentiating action of solvents, solvation, etc., were completely reviewed in the excellent monograph of Shatenshtein, which was translated into English and thus became available to international readership. This major contribution is well known to those working in the field of solution chemistry and is still frequently cited. Izmailov also continued his early studies on the behavior of glass electrode in different solvents. He made a considerable contribution to the theory of physicochemical analysis. In Ukraine, Izmailov was one of the pioneers in the application of radioactive indicators to physical chemistry. The latter were used by him both for studying solubility and solvation of salts and to gain understanding of the response mechanism of glass electrodes. Izmailov was among the first who used Volta cells for determination of real solvation energies and activity coefficients of single ions. At the end of the 1950s, he applied quantum chemistry to estimate proton affinities and ionic solvation energies. The untimely death of Nikolai Izmailov in 1961 was a loss to science, but his prolific output of over 280 publications ensures his place in the records of modern physical chemistry. This appreciation introduces a collection of works that would surely have captured his interest and will serve to honor his memory. A more detailed and personalized account of the man and the times in which he lived and achieved will be published in the September 2008 issue of Chemistry International and furnishes a link to a short bibliography listing some of his seminal publications. Nikolay O. Mchedlov-Petrossyan V. N. Karazin National University

Detonation nanodiamond (DN) was discovered in 1963, but for several reasons was known only among a small number of scientists until the turn of the century. The most serious cause was the fact that primary nanocarbon particles formed by the "bottom-up method" are in general covalently bound together under high-temperature and -pressure conditions to form large agglutinates, which were difficult to separate by conventional methods. DN was not an exception. A breakthrough led to the isolation of primary particles having the expected size of 4-5 nm by wet-milling with zirconia micro-beads. Thus, long-waited primary particles of DN finally became available in kg quantities in the form of colloidal sol, gel, and readily redispersible flakes. Progress in the development of a new form of the old material is presented.

Due to population upsurge, pesticides (derivatives of organophosphorus acids included) find widespread use in agriculture. The toxicity and long-term environmental hazard of such compounds require detailed studies on decomposition mechanisms of the pesticides and development of efficient, readily available, and inexpensive systems for their decontamination. A simple and straightforward method for the decomposition of organophosphorus compounds involves their reactions with nucleophiles. Studies on the reactivity of "normal" and α-nucleophiles toward electron-deficient centers allowed us to state a number of basic principles on the nature of the α-effect. One of the most important conclusions is: It is unlikely that the structure variations in the known α-nucleophiles will result in higher reactivity than that of hydroxylamine anion. As a practical matter, the essential disadvantages of decomposition of organophosphorus compounds in water and organic solvents are: (i) instability of active nucleophiles and oxidizing agents, (ii) corrosiveness, and (iii) extremely low solubility of organophosphorus compounds in water. These dictate the strategy of further studies, namely, carrying out the reaction in microorganized media. The first research line involves the development of the functional imidazole-based detergents functionalized with α-nucleophilic fragments. A number of efficient detergents were first synthesized. An examination of the nucleophilicity of the functional fragments in water and in the micellar phase and quantitative assessment of the factors responsible for the micellar effects showed unambiguously that the main cause of the observed accelerations is the substrate concentrating in the micellar pseudophase. The second research line consists of studies on the reactivity of versatile oxidative/nucleophilic systems involving H 2 O 2 /activator and polyhalide ion organocomplexes in water, aqueous alcohols, and micelles of cationic detergents. The novel sources of "active" halogen are highly competitive both with conventional hazardous chlorine derivatives and "green" systems involving H 2 O 2 /activator.

Various decorations, functionalizations, or defects of conjugated benzenoid or graphitic networks are considered, with special attention to the case that the structures are possibly extended in one or two dimensions. This includes various polymers, their end structures, and defects of side groups or vacancies along the chain, strip, or nanotube. This approach further includes various boundary (or edge) structures on semi-infinite graphite, as well as various "quasi-local" defects in what is otherwise two-dimensionally infinite graphite, such defects encompassing vacancy defects, selected substitutional defects, and perhaps even dislocations and disclinations. There are many possible such nanostructures, but property characterization is ultimately desired. Attention is paid to consequent occurrences of defect-localized unpaired (or weakly paired) electrons, as formulated within a resonating valence bond (RVB) framework, especially as regards simple classically appealing theorems or rules. But a further molecular orbital (MO) view is developed. Note is made of associated modifications in the local density of states near the Fermi energy. Consonance of predictions from RVB and MO viewpoints is taken as an indicator of reliable prediction.

Solutions of the zwitterionic betaine dye 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (hereinafter called standard betaine dye ) and its derivatives are solvatochromic, thermochromic, piezochromic, and halochromic. That is, the position of its longest-wavelength intramolecular charge-transfer (CT) absorption band depends on solvent polarity, solution temperature, external pressure, and the type and concentration of salts (ionophores) added to the betaine dye solution. The outstanding large negative solvatochromism of this standard betaine dye has been used to establish UV/vis spectroscopically a comprehensive set of empirical parameters of solvent polarity, called E T (30) resp. E T N values, now known for many molecular and ionic solvents as well as for a great variety of solvent mixtures. This report describes relevant physicochemical properties of this standard betaine dye as well as the definition and some more recent practical applications of these solvent polarity parameters, derived from the standard betaine dye and its derivatives. In particular, the perichromism of the standard betaine dye can be used to study the polarity of microheterogeneous solutions (e.g., micelles and other organized media), surfaces (e.g., silica, alumina, cellulose), glasses (e.g., sol-gel systems), and solids (e.g., polymers), and for the construction of chemical sensors. As extension to solvatochromism, the more general term perichromism describes UV/vis band shifts of chromophore-containing solutes which are caused not only by changes in the surrounding solvent sphere, but also by their embedding in other surroundings such as micelles, vesicles, glasses, polymers, solids, interfaces, and surfaces. Some representative examples for such extended applications of the perichromic standard betaine dye are given.

The key features of the phonon-induced relaxation of electronic excitations in the (7,0) zig-zag carbon nanotube (CNT) and the Pb 16 Se 16 quantum dot (QD) are contrasted using a time-domain ab initio density functional theory (DFT) simulation. Upon excitation from the valence to the conduction band (CB), the electrons and holes nonradiatively decay to the band-edge in both materials. The paper compares the electronic structure, optical spectra, important phonon modes, and decay channels in the CNT and QD. The relaxation is faster in the CNT than in the QD. In the PbSe QD, the electronic energy decays by coupling to low-frequency acoustic modes. The decay is nonexponential, in agreement with non-Lorentzian line-shapes observed in optical experiments. In contrast to the QD, the excitation decay in the CNT occurs primarily via high-frequency optical modes. Even though the holes have a higher density of states (DOS), they relax more slowly than the electrons, due to better coupling to low-frequency vibrations. Further, the expected phonon bottleneck is not observed in the QD, as rationalized by a high density of optically dark states. The same argument applies to the CNT. The computed results agree well with experimentally measured ultrafast relaxation time-scales and provide a unique atomistic picture of the electron-phonon relaxation processes.

In the paper, a report on the rational design of the calixarene receptors bearing ligating, H-donor, H-acceptor fragments at the wide and/or narrow rim of the macrocycle is presented. The calixarenes form supramolecular complexes with various cations, anions, organic molecules, and biomolecules in solution, in the crystalline state and even in the gas phase. The calixarenes or their complexes can be used as materials for radionuclide extraction, construction of chemosensors, and drug design.

The so-called apparent ionization constants of various acids (mainly indicator dyes) in versatile organized solutions are analyzed. Aqueous micellar solutions of colloidal surfactants and related lyophilic colloidal systems display a strong differentiating influence on the acidic strength of indicators located in the dispersed pseudophase, i.e., non-uniform changes of p K a on going from water to the given system. This concept allows the influence of such media on acid-base properties of dissolved reagents to be rationalized. It is demonstrated that the differentiating phenomenon is the main reason for limitation of the common electrostatic model of acid-base interactions, and is the principal hindrance to exact evaluations of the interfacial electrical potentials of ionic micelles by means of acid-base indicators. Salt effects, i.e., the influence of supporting electrolytes on the apparent ionization constants of acid-base indicators in the Stern region of ionic micelles, are considered. These salt effects can be conventionally divided into two kinds, namely, general ( normal ) and special ( specific ) effects. While the first type adds up to screening of the surface charge, the second one consists in micellar transitions caused by hydrophobic counterions.

Cyclodextrins (CDs) attract much attention for industrial applications and academic research. A few experimental methods for determination of the binding constant between CD and a guest molecule were reviewed critically. A hydrophile–hydrophobe matching model for host–guest docking was proposed for estimation of the binding constant and the solution structure of the complex. Rather detailed solution structures of CD complexes were determined by proton NMR spectroscopy, aided by calculations of molecular mechanics and surface areas, and were used to analyze the binding constants. The binding constants of CDs with multi-site guests were analyzed on the basis of their solution structures. The working mechanisms and physicochemical predictions in a few pharmaceutical applications of CDs were proposed on the basis of detailed solution structures and accurate binding constants.

The advantages of dye-doped polymer matrices over polymers and dyes, separately, are analyzed. The effects of the polymer nature and chemical constitution of organic dyes on the spectral and luminescent properties of these matrices are discussed. The processes of dye aggregation in polymers are characterized, and their influence on the photophysical properties and photochemical stability of dye-doped nonphotoconducting and photoconducting polymers is discussed. The different approaches for the struggle with dye aggregation in polymers are offered. The main paths of energy degradation of electronic excitation in such materials are analyzed. The prospects for the applications of dye-doped polymer materials as passive Q-switches of solid-state lasers, active laser media (ALM), luminescent solar concentrator (LSCs), photovoltaic cells, and electroluminescent (EL) emitters are demonstrated.

The paper reviews ion aggregation in ionic solution in solvents of low and high permittivity. Although higher ion aggregates from 1:1 type electrolytes in low-pemittivity media (ε r < 10) are widely accepted, only a few chemists have recognized the higher ion aggregation in the higher-permittivity media. However, we have clarified that the chemical interaction, such as coordination, can operate between simple anions and cations in nonaqueous solvents (20 < ε r < 65) of low solvation ability. Acids (HA) and their conjugate base anions (A - ) may react with each other to form homoconjugated species, such as A - (HA) 2 , in acetonitrile or benzonitrile (i.e., solvents possessing poor hydrogen-bonding donor and acceptor abilities). An analytical method of conductivity data for 1:1 electrolytes has been developed and successfully applied to very complicated systems, in which the ion pair (1:1), triple ions (2:1 and 1:2), and the quadrupole (2:2 association) are involved in a solution at the same time. After observing the direct reaction of some anions (e.g., Cl - ) and cations (e.g., Li + ) toward a certain species, we interpreted comprehensively the salt effects in chemical equilibria, based on distinct chemical interactions and not merely a vague term, "medium effect". The mechanism of salt effects on solvolysis reactions of the S N 1 type in organic-aqueous mixed solvents has been elucidated. We discussed that a reaction manner similar to that in nonaqueous solution can take place even in some "aqueous" solution if the huge network of hydrogen-bonding of bulk water (the number of water, n w > ~10 8 ) is destroyed due to any spatial barriers (such as ions, molecules, surface) or elevated temperature.

Quantitative physicochemical analysis (QPCA) enables the determination of the stoichiometric compositions and physicochemical parameters of species in equilibrium systems proceeding from the composition-property dependencies. The paper discusses modifications to the routine QPCA procedures required to characterize properties of reagents fixed on surfaces of silica-organic hybrid materials. The cooperative effects and the energetic heterogeneity of fixed reagents are especially important in this context. It follows that the main peculiarities of silica surfaces chemically modified by aliphatic amines are (a) the pronounced energetic heterogeneity of reagents caused by the non-random surface topography, (b) the decrease of the bacisity of amines induced by their interactions with residual surface silanols, and (c) the expressed sensibility of reactions in the near-surface layer to the state of its hydration. The interaction of grafted organic bases with metal ions results in the preferred formation of bis metal-ligand coordination compounds. Stability constants of complexes are decreased as a consequence of fixation and depend on not only donor but also acceptor ability of a solvent. Also, the denticity of polydentate ligands may decrease as a result of grafting. The changes of protolytic and complexing properties in the case of grafting of weak acids and phosphorus-containing complexons are due to their interactions with other surface groups and the influence of hydration effects in the near-surface layer.

Organofunctionalized silsesquioxane polymers obtained in a water-soluble form can be used to coat various substrates such as SiO 2 , SiO 2 /Al 2 O 3 , Al 2 O 3 , cellulose/Al 2 O 3 , and graphite or, when obtained in a water-insoluble form, can be used directly. These organofunctionalized silsesquioxanes can also be attached to poly(dimethylsiloxane) (PDMS) polymers. The functional groups constituted by neutral amine groups or cationic groups (pyridinium, 3- and 4-picolinium, or 1,4-diazabicyclo[2.2.2]octane (DABCO), mono- or -dicationic) have relatively high affinity for metal ion in ethanol solutions, as shown by their stability constants. Materials containing attached cationic functional groups have also been efficiently used to immobilize various electroactive species and to construct electrochemical sensors for analytical applications. This work discusses the preparation of silsesquioxane derivatives, their characterization as prepared and when dispersed on several substrates, and comments on some applications of these materials, with an emphasis on the metal adsorption process and manufacture of electrochemical sensors.

Measurements of the liquid-liquid phase diagrams of solutions of the ionic liquids (ILs) 1-dodecyl-3-methylimidazolium chloride (C 12 mimCl) in arenes (benzene, toluene, o -xylene, tetraline) and 1-tetradecyl-3-methylimidazolium chloride (C 14 mimCl) in CCl 4 are reported and compared with those of solutions of trihexyl-tetradecyl-phosphonium halides (P 666 14 Cl, P 666 14 Br) in hydrocarbons and 1-alkyl-3-methylimidazolium tetrafluoroborates (C n mimBF 4 ) in alcohols and water. The phase diagrams of solutions of tetrapentyl-ammonium bromide (N 5555 Br) in water and KI in SO 2 are also discussed. Except for the KI/SO 2 system, which features a lower critical solution point (LCSP), all systems have an upper critical solution point (UCSP) and show corresponding-states behavior. The experimental data are compared with results from simulations and theory concerning the model fluid of charged hard spheres in a dielectric continuum, termed restricted primitive model (RPM). The analysis in terms of of RPM variables shows agreement with the location of the critical point (CP) of the model with noticeable systematic deviations. However, for protic solvents, the CP becomes an LCSP, while in aprotic solvents the CP is a UCSP as expected for Coulomb systems. This indicates that in aprotic solvents, the phase transition is essentially determined by the Coulomb interactions, while in the solutions in protic solvents with hydrogen bonds, both Coulomb and solvophobic interactions are important.