Constant Of Transfer Research Articles

Energy disposal via electron–hole pair excitation in atom recombination on metal surfaces: Electron distribution function and detailed balancing

The energy disposal via electron–hole (e–h) pair formation in the highly exoergic recombination of gas atoms on metal surfaces, has been studied. The impact of this excitation process on the energy spectrum of the metal electrons has been investigated at steady state. The energy distribution function of the electrons is shown to be non-thermal to an extent that depends on the reaction rate, probability distribution function for e–h pair creation and physical parameters of the material. The model has been applied to compute the electron spectra of metal surfaces, using kinetic data on H atom recombination that are available from the literature. The number of electrons made available for detection as chemicurrent has been derived and compared to experimental data on the H/Cu system. The interplay between the electron distribution function and the reaction kinetics is analysed by means of the principle of detailed balance. The detailed balancing analysis shows that, depending on the e–h excitation energy, the rate constant of energy transfer from the bath to the adlayer can be orders of magnitude larger than that proper for equilibrium conditions.

Excited-state proton transfer from pyranine to acetate in methanol

Excited-state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6-trisulphonate, HPTS) to acetate in methanol has been studied by steady-state and time-resolved fluorescence spectroscopy. The rate constant of direct proton transfer from pyranine to acetate (k 1) is calculated to be ∼1 × 109 M−1 s−1. This is slower by about two orders of magnitude than that in bulk water (8 × 1010 M−1 s−1) at 4 M acetate.

Electrochemical and photoelectrochemical response of electrodes coated with LB films of an azopolymer

This paper describes the electrochemical and photoelectrochemical behaviour of electrodes coated with Langmuir–Blodgett (LB) films of an azopolymer. The coating material used is a pyridine azopolymer (PAzPy) obtained by free radical polymerization of 6-[2-(4-pyridyazo)phenoxy]hexyl methacrylate (AzPy). Cyclic voltammetry experiments of LB films deposited at several transference surface pressures were performed to analyze the effect of the molecular packing on the electrochemical response. The influence of the pH of the electrolytic solution was also considered. AFM images have helped in the interpretation of the molecular architecture influence on the redox activity of the films. From the experimental results it was concluded that PAzPy is situated with the nitrogen from the pyridine group close to the ITO electrode surface in the LB films, which allows a direct electron transfer between the electrode surface and the azobenzene group leading to a quick electrochemical response of the films. The azobenzene electrochemical activity and the kinetics of the process are also highly dependent on the proton transfer process between the electrolytic solution and the azobenzene unit. The efficiency of the proton transfer process is determined by the pH of the electrolytic solution as well as by the molecular architecture of the film. The results presented in this paper show that, under optimal conditions, both the percentage of electroactive azobenzene chromophores and the standard heterogeneous rate constant of electron transfer are higher for PAzPy arranged in LB films compared with the values so far reported for azobenzenes of lower molecular weight.

Cathodic behaviour of europium (III) on glassy carbon, electrochemical formation of Al4Eu, and oxoacidity reactions in the eutectic LiCl–KCl

Abstract The electrochemical redox process Eu(III)/Eu(II) in the temperature range 673–823 K on glassy carbon was studied by using transient electrochemical techniques. The results showed that the electroreduction of Eu(III) to Eu(II) is quasi-reversible. Accurate values of the intrinsic rate constant of charge transfer, k 0 , as well as of the charge transfer coefficient, α , have been calculated by simulation of the cyclic voltammograms and from the steady-state current potential curves by applying the pit-mapping, Gauss–Newton non-linear square and simplex methods. The diffusion coefficients of Eu(III) and Eu(II) ions have also been calculated. The validity of the Arrhenius law was verified by plotting the variation of the logarithm of the diffusion coefficients vs 1/ T . For the extraction of europium from molten chlorides, the use of a reactive electrode made of aluminium leading to an Al 4 Eu alloy seems to be a pertinent route. Potentiometric titrations of Eu(III) solutions with oxide donors, using a ytria stabilized zirconia electrode “YSZE” as a pO 2− indicator electrode, have shown the formation of europium oxychloride and its solubility product has been determined at 723 K (p k s (EuOCl) = 8.4 ± 0.3).

Plasma Concentrations, Pharmacokinetics and Urinary Excretion of Gatifloxacin after Single Intravenous Injection in Buffalo Calves

The pharmacokinetics and urinary excretion of gatifloxacin were investigated after a single intravenous injection of 4 mg/kg body weight in buffalo calves. The therapeutic plasma drug concentration was maintained for up to 12 h. Gatifloxacin rapidly distributed from blood to tissue compartments, which was evident from the high values of the distribution rate constant, alpha1 (11.1 +/- 1.06 h(-1)) and the rate constant of transfer of drug from central to peripheral compartment, k12 (6.29 +/- 0.46 h(-1)). The area under the plasma drug concentration-time curve and apparent volume of distribution were 17.1 +/- 0.63 (microg.h)/ml and 3.56 +/- 0.95 L/kg, respectively. The elimination half-life (t (1/2 beta)), total body clearance (ClB) and the ratio of drug present in tissues and plasma (T/P) were 10.4 +/- 2.47 h, 235.1 +/- 8.47 ml/(kg.h) and 10.1 +/- 2.25, respectively. About 19.7% of the administered drug was excreted in urine within 24 h. A satisfactory intravenous dosage regimen for gatifloxacin in buffalo calves would be 5.3 mg/kg at 24 h intervals.

Picosecond IR-UV pump–probe spectroscopic study on the vibrational energy flow in isolated molecules and clusters

Intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) from the XH stretching vibrations, where X refers to O or C atom, of aromatic molecules and their hydrogen(H)-bonded clusters are investigated by picosecond time-resolved IR-UV pump probe spectroscopy in a supersonic beam. For bare molecules, we mainly focus on IVR of the OH stretch of phenol. We describe the IVR of the OH stretch by a two-step tier model and examine the effect of the anharmonic coupling strength and the density of states on IVR rate and mechanism by using isotope substitution. In the H-bonded clusters of phenol, we show that the relaxation of the OH stretching vibration can be described by a stepwise process and then discuss which process is sensitive to the H-bonding strength. We discuss the difference/similarity of IVR/VP between the "donor" and the "acceptor" sites in phenol-ethylene cluster by exciting the CH stretch vibrations. Finally, we study the vibrational energy transfer in the isolated molecules having the alkyl chain, namely phenylalcanol (PA). In this system, we measure the rate constant of the vibrational energy transfer between the OH stretch and the vibrations of benzene ring which are connected at the both ends of the alkyl chain. This energy transfer can be called "through-bond IVR". We investigate the three factors which are thought to control the energy transfer rate; (1) "OH <--> next CH(2)" coupling, (2) chain length and (3) conformation. We discuss the energy transfer mechanism in PAs by examining these factors.

Behavior of riboflavin on plain carbon paste and aza macrocycles based chemically modified electrodes

The electrochemical behavior of riboflavin at a carbon paste electrode and electrodes modified with aza crown ethers have been studied using voltammetric techniques. The macrocycles used as modifiers were 1,4,8,11-tetraazacyclooctadecane; 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane; 1,4,7,10-tetraoxa-13-azacyclopentadecane and 1,4,7,10-tetratosyl-1,4,7,10-tetraazacyclooctadecane, out of which 1,4,8,11-tetraazacyclooctadecane showed better response for riboflavin. The interaction of riboflavin with 1,4,8,11-tetraazacyclooctadecane was confirmed by complexation study in 20% DMSO + water (log K 5.58) using differential pulse polarography. The kinetic parameters viz. electron transfer coefficient and rate constant of electron transfer across the modified electrode were found to be 0.708 and 5.5 s −1, respectively. The surface coverage of the 1,4,8,11-tetraazacyclooctadecane modified electrode was calculated to be 5 × 10 −10 mol cm −2 by cyclic voltammetry and chronocoulometry. A linear working range of 0.5 ng cm −3 to 70 μg cm −3 with a detection limit of 0.2 ng cm −3 has been obtained using 1,4,8,11-tetraazacyclooctadecane modified electrode by square wave anodic stripping voltammetry. It was possible to determine riboflavin in presence of some organic molecules like thiamine hydrochloride, nicotinamide, pyridoxine hydrochloride, ascorbic acid, para-aminobenzoic acid and l-tryptophan. Also simultaneous and quantitative determinations were achieved for combination of some of these. The electrode could be used for estimation of riboflavin in pharmaceutical and food samples.

A Mechanistic Dichotomy in Scandium Ion-Promoted Hydride Transfer of an NADH Analogue: Delicate Balance between One-Step Hydride-Transfer and Electron-Transfer Pathways

The rate constant (kH) of hydride transfer from an NADH analogue, 9,10-dihydro-10-methylacridine (AcrH2), to 1-(p-tolylsulfinyl)-2,5-benzoquinone (TolSQ) increases with increasing Sc(3+) concentration ([Sc(3+)]) to reach a constant value, when all TolSQ molecules form the TolSQ-Sc(3+) complex. When AcrH2 is replaced by the dideuterated compound (AcrD2), however, the rate constant (kD) increases linearly with an increase in ([Sc(3+)]) without exhibiting a saturation behavior. In such a case, the primary kinetic deuterium isotope effect (kH/kD) decreases with increasing ([Sc(3+)]). On the other hand, the rate constant of Sc(3+)-promoted electron transfer from tris(2-phenylpyridine)iridium [Ir(ppy)3]to TolSQ also increases linearly with increasing ([Sc(3+)]) at high concentrations of Sc(3+) due to formation of a 1:2 complex between TolSQ*- and Sc(3+), [TolSQ*--(Sc(3+)2], which was detected by ESR. The significant difference with regard to dependence of the rate constant of hydride transfer on ([Sc(3+)]) between AcrH2 and AcrD2 in comparison with that of Sc3+-promoted electron transfer indicates that the reaction pathway is changed from one-step hydride transfer from AcrH2 to the TolSQ-Sc3+ complex to Sc3+-promoted electron transfer from AcrD2 to the TolSQ-Sc3+ complex, followed by proton and electron transfer. Such a change between two reaction pathways, which are employed simultaneously, is also observed by simple changes of temperature and concentration of Sc3+.

Mechanistic Borderline between One-Step Hydrogen Transfer and Sequential Transfers of Electron and Proton in Reactions of NADH Analogues with Triplet Excited States of Tetrazines and Ru(bpy)32+*

Efficient energy transfer from Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine, denotes the excited state) to 3,6-disubstituted tetrazines [R(2)Tz: R = Ph (Ph(2)Tz), 2-chlorophenyl [(ClPh)(2)Tz], 2-pyridyl (Py(2)Tz)] occurs to yield the triplet excited states of tetrazines ((3)R(2)Tz(*)), which have longer lifetimes and higher oxidizing ability as compared with those of Ru(bpy)(3)(2+). The dynamics of hydrogen-transfer reactions from NADH (dihydronicotinamide adenine dinucleotide) analogues has been examined in detail using (3)R(2)Tz(*) by laser flash photolysis measurements. Whether formal hydrogen transfer from NADH analogues to (3)R(2)Tz(*) proceeds via a one-step process or sequential electron and proton transfer processes is changed by a subtle difference in the electron donor ability and the deprotonation reactivity of the radical cations of NADH analogues as well as the electron-acceptor ability of (3)R(2)Tz(*) and the protonation reactivity of R(2)Tz(*)(-). In the case of (3)Ph(2)Tz(*), which is a weaker electron acceptor than the other tetrazine derivatives [(ClPh)(2)Tz; Py(2)Tz], direct one-step hydrogen transfer occurs from 10-methyl-9,10-dihydroacridine (AcrH(2)) to (3)Ph(2)Tz(*) without formation of the radical cation (AcrH(2)(*)(+)). The rate constant of the direct hydrogen transfer from AcrH(2) to (3)Ph(2)Tz(*) is larger than that expected from the Gibbs energy relation for the rate constants of electron transfer from various electron donors to (3)Ph(2)Tz(*), exhibiting the primary deuterium kinetic isotope effect. On the other hand, hydrogen transfer from 9-isopropyl-10-methyl-9,10-dihydroacridine (AcrHPr(i)) and 1-benzyl-1,4-dihydronicotinamide (BNAH) to (3)R(2)Tz(*) occurs via sequential electron and proton transfer processes, when both the radical cations and deprotonated radicals of NADH analogues are detected by the laser flash photolysis measurements.

Activation of Electron-Transfer Reduction of Oxygen by Hydrogen Bond Formation of Superoxide Anion with Ammonium Ion

A hydrogen bond formed between the superoxide anion and the ammonium ion (NH4+) accelerates electron transfer from the C60 radical anion to oxygen significantly, whereas the tetra-n-butylammonium ion has no ability to form a hydrogen bond with the superoxidie anion, exhibiting no acceleration of the electron-transfer reduction of oxygen. The second-order rate constant of electron transfer from C60*- to O2 increases linearly with increasing concentration of NH4+. This indicates that O2*- produced in the electron transfer from C60 to O2 is stabilized by 1:1 complex formation between O2*- and NH4+. The 1:1 complex formed between O2*- and NH4+ was detected by ESR. The binding of O2*- with NH4+ results in a positive shift of the reduction potential of O2 with increasing concentration of NH4+, leading to the acceleration of electron transfer from C60*- to O2.

Coherent nuclear dynamics in ultrafast electron transfer in a porphyrin-ferrocene dyad

Ultrafast electron transfer in a porphyrin-ferrocene dyad in which the ferrocene moiety is directly linked at the meso-position of the porphyrin was studied using femtosecond up-conversion and pump–probe techniques. The time constant of electron transfer was ∼110 fs both in benzene and tetrahydrofuran. Vibrational coherence of the 130-, 200-, and 250-cm −1 modes, which were assigned to the translation and rotation of ferrocene, was observed, and was found to be phase shifted with respect to the vibrational coherence of the 330-cm −1 mode. The relation between this behavior of vibrational modes and electron transfer is discussed.

Electrocatalytic redox of hydroquinone by two forms of l-Proline

The redox behavior, the molecular mechanism and electronic transfer of hydroquinone interacted with two forms of l-Proline, covalent-linked to glass carbon electrode surface through C N bond by electrooxidation and free dissolved in solution, were investigated by means of UV–vis and electrochemistry. The UV–vis spectrum showed that the reaction between free l-Proline and hydroquinone did not involve strong chemical bond. However, the electrochemical behavior of covalent-linked l-Proline is different from that of free one. Owing to electrostatic effect, the form of covalent-linked l-Proline favors electron transfer and enhances the reversibility of redox for hydroquinone. This phenomenon is conformed by cyclic voltammogram with a significant increase in peak current of hydroquinone redox and rate constant of electron transfer. It was found that it is a three-electron-transfer reaction. On the contrary, the form of free l-Proline unfavors electron transfer, resulting in a decrease in peak current of hydroquinone and rate constant, and the hydrogen bond was formed in the interaction.

Kinetics and mechanism of electron transfer in intact photosystem II and in the isolated reaction center: Pheophytin is the primary electron acceptor

The mechanism and kinetics of electron transfer in isolated D1/D2-cyt(b559) photosystem (PS) II reaction centers (RCs) and in intact PSII cores have been studied by femtosecond transient absorption and kinetic compartment modeling. For intact PSII, a component of approximately 1.5 ps reflects the dominant energy-trapping kinetics from the antenna by the RC. A 5.5-ps component reflects the apparent lifetime of primary charge separation, which is faster by a factor of 8-12 than assumed so far. The 35-ps component represents the apparent lifetime of formation of a secondary radical pair, and the approximately 200-ps component represents the electron transfer to the Q(A) acceptor. In isolated RCs, the apparent lifetimes of primary and secondary charge separation are approximately 3 and 11 ps, respectively. It is shown (i) that pheophytin is reduced in the first step, and (ii) that the rate constants of electron transfer in the RC are identical for PSII cores and for isolated RCs. We interpret the first electron transfer step as electron donation from the primary electron donor Chl(acc D1). Thus, this mechanism, suggested earlier for isolated RCs at cryogenic temperatures, is also operative in intact PSII cores and in isolated RCs at ambient temperature. The effective rate constant of primary electron transfer from the equilibrated RC* excited state is 170-180 ns(-1), and the rate constant of secondary electron transfer is 120-130 ns(-1).

Binding Modes in Metal Ion Complexes of Quinones and Semiquinone Radical Anions: Electron‐Transfer Reactivity

9,10-Phenanthrenequinone (PQ) and 1,10-phenanthroline-5,6-dione (PTQ) form 1:1 and 2:1 complexes with metal ions (M (n+)=Sc (3+), Y (3+), Mg (2+), and Ca (2+)) in acetonitrile (MeCN), respectively. The binding constants of PQ--M (n+) complexes vary depending on either the Lewis acidity or ion radius of metal ions. The one-electron reduced species (PTQ(-)) forms 1:1 complexes with M (n+), and PQ(-) also forms 1:1 complexes with Sc(3+), Mg(2+), and Ca(2+), whereas PQ(-) forms 1:2 complexes with Y(3+) and La(3+), as indicated by electron spin resonance (ESR) measurements. On the other hand, semiquinone radical anions (Q(-) and NQ(-)) derived from p-benzoquinone (Q) and 1,4-naphthoquinone (NQ) form Sc(3+)-bridged pi-dimer radical anion complexes, Q(-)--(Sc(3+))(n)--Q and NQ(-)--(Sc(3+))(n)-NQ (n=2 and 3), respectively. The one-electron reduction potentials of quinones (PQ, PTQ, and Q) are largely positively shifted in the presence of M (n+). The rate constant of electron transfer from CoTPP (TPP(2-)=dianion of tetraphenylporphyrin) to PQ increases with increasing the concentration of Sc(3+) to reach a constant value, when all PQ molecules form the 1:1 complex with Sc(3+). Rates of electron transfer from 10,10'-dimethyl-9,9'-biacridine [(AcrH)(2)] to PTQ are also accelerated significantly by the presence of Sc(3+), Y(3+), and Mg(2+), exhibiting a first-order dependence with respect to concentrations of metal ions. In contrast to the case of o-quinones, unusually high kinetic orders are observed for rates of Sc(3+)-promoted electron transfer from tris(2-phenylpyridine)iridium(III) [Ir(ppy)(3)] to p-quinones (Q): second-order dependence on concentration of Q, and second- and third-order dependence on concentration of Sc(3+) due to formation of highly ordered radical anion complexes, Q()--(Sc(3+))(n)--Q (n=2 and 3).

Preparation and characterization of diethylene glycol bis(2-aminophenyl) ether-modified glassy carbon electrode

Diethylene glycol bis(2-aminophenyl) ether (DGAE) diazonium salt was covalently electrografted on a glassy carbon (GC) surface and behavior of this novel surface was investigated. Synthesis of DGAE diazonium salt (DGAE-DAS) and in situ modification of GC electrode were performed in aqueous media containing NaNO 2, keeping the temperature below +4 °C. For the characterization of the modified electrode surface by cyclic voltammetry, dopamine (DA) was used to prove the attachment of the DGAE-DAS on the GC surface. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) were used to observe the molecular bound properties of the adsorbates at the DGAE-modified GC surface (GC-DGAE). The EIS results were analyzed using the Randles equivalent circuit. The charge transfer resistance on bare GC and the modified surface were calculated using the model equivalent circuit for the ferrocene redox system. Surface coverage was found as 0.4 showing the presence of high pinhole and defects in the modified electrode. The rate constant of electron transfer through the monolayer was calculated for ferrocene. Working potential range and the stability of the DGAE-modified GC electrode was also determined.

Interaction between Mitochondrial CYP27B1 and Adrenodoxin: Role of Arginine 458 of Mouse CYP27B1

A molecular modeling study of CYP27B1 suggests that Arg458 of mouse CYP27B1 is involved in interaction with adrenodoxin (ADX). Thus, we generated CYP27B1 mutants R458K and R458Q and revealed their enzymatic properties. Substrate-induced difference spectra and K(m) values for 1alpha-hydroxylation of 25(OH)D3 indicate that the replacement of Arg458 with Lys or Gln does not affect substrate binding. However, these mutants showed remarkable decreases of both kcat values and the ratio of product formation to NADPH oxidation (coupling efficiency). A high K(m) value of R458Q for ADX concentration and a decrease of rate constant of the first electron transfer seem reasonable considering that the conversion from Arg to noncharged Gln abolishes salt-bridge formation with the acidic residue of ADX. On the other hand, R458K showed atypical kinetics for ADX concentration with Hill's constant of 2.0 and high catalytic activity at high ADX concentration by increase of coupling efficiency. These results suggest that conformational change of R458K by binding the two ADX molecules is essential for 1alpha-hydroxylation of 25(OH)D3. On the other hand, binding one ADX molecule is sufficient for the conformational change of the wild-type CYP27B1, judging from its Michaelis-Menten-type kinetics for ADX concentration with high coupling efficiency. These results suggest that ADX functions as an effector for the oxygen transfer reaction in addition to being an electron donor for CYP27B1.

Three-centered model of ultrafast photoinduced charge transfer: Continuum dielectric approach

A theoretical description of photoinduced charge transfer involves explicit treating both the optical formation of the nuclear wave packet on the excited free energy surface and its ensuing dynamics. The reaction pathway constitutes two-stage charge transfer between three centers. Manifestations of fractional charge transfer at first stage are explored. An expression for time dependent rate constant of photoinduced charge transfer is found in the framework of the linear dielectric continuum model of the medium. The model involves both the intramolecular vibrational reorganization and the Coulombic interaction of the transferred charge with the medium polarization fluctuations and allows to express the rate in terms of intramolecular reorganization parameters and complex dielectric permittivity. The influence of the vibrational coherent motion in the locally excited state on the charge transfer dynamics has been explored. The dependence of the ultrafast photoinduced charge transfer dynamics on the excitation pulse carrier frequency (spectral effect) has been investigated. The spectral effect has been shown to depend on quantity of the fractional charge.

Electronic Transitions of the Soret Band of Reaction Centers fromRhodobacter sphaeroidesStudied by Femtosecond Transient Absorbance Spectroscopy

The Soret band of reaction centers from Rhodobacter sphaeroides has been systematically studied using femtosecond transient absorption spectroscopy. When the excitation wavelength was scanned over the entire Soret band, the approximate absorption spectra of the bacteriochlorophyll dimer, the monomer bacteriochlorophylls, and the bacteriopheophytins within the Soret band were determined by analyzing the ground state bleaching with about 100 fs resolution. The main contribution of H is on the blue end of the spectrum, peaking near 350 nm, P absorbs mostly on the red side of the spectrum, but probably has multiple bands, and the main absorbance of B likely lies between H and P, overlapping with P on the red side (particularly near 390 nm). The energy transfer from B to P in the QY band takes about 300 fs when Soret-band excitation is used and the time constant of overall energy transfer from H to B to P in the QY band when H is specifically excited near 350 nm is about 500 fs. Internal conversion after Soret-band excitation is the rate-limiting step for the energy-transfer process. The time constant of internal conversion for B and P is less than 300 fs, and for H it is about 500 fs.

Effect of dielectric and structural properties of solutions on the polymerizability of diallylammonium-type monomers

New polymerization systems— N , N -diallyl- N -methylammonium trifluoroacetate (D1TFA) and N , N -diallylammonium trifluoroacetate (D2TFA)—exhibit phenomena that distinguish their behavior during radical polymerization (Scheme 1) from the known cases, in particular, from the quaternary N , N -diallyl- N , N -dimethylammonium chloride (D3C). These phenomena are evidence of a substantial effect of the medium on the basic polymerization characteristics of new cationogenic monomers: the initial polymerization rate V , the average length of the polymer chain P n , and the constant of chain transfer to the monomer C m [1].

Phase solubility and inclusion complex of itraconazole with β-cyclodextrin using supercritical carbon dioxide

Phase-solubility techniques were used to assess the formation of inclusion complex between itraconazole and β-cyclodextrin. The stability constant and free energies of transfer of itraconazole from aqueous solution to the cavity of β-cyclodextrin were calculated. Itraconazole solubility in supercritical carbon dioxide (SC CO2) was measured at different temperatures and pressures. Drug formulations of itraconazole were prepared by complexation of the drug into β-cyclodextrin using SC CO2. Effects of temperature and pressure on inclusion yield of the prepared complexes were studied. The solvent-free inclusion complexes obtained from this method were characterized by UV spectroscopy, differential scanning calorimetry, powder X-ray diffraction, and scanning electron microscopy and compared to those obtained from physical mixing and coprecipitation methods. Results showed that β-cyclodextrin significantly improved solubility of itraconazole in aqueous solutions. The free energies of transfer of itraconazole from aqueous solution to the cavity of β-cyclodextrin increased negatively with increasing β-cyclodextrin concentration. Higher inclusion yields were obtained in the SC CO2 method compared to physical mixing and coprecipitation methods. Both temperature and pressure had significant effects on itraconazole solubility in SC CO2 and the inclusion yield of the complex prepared by SC CO2 method. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association