PCM Model Research Articles

Stereoselective Bromoboration of Acetylene with Boron Tribromide: Preparation and Cross-Coupling Reactions of (Z)-Bromovinylboronates.

The mechanism of acetylene bromoboration in neat boron tribromide was studied carefully by means of experiment and theory. Besides the syn-addition mechanism through a four-center transition state, radical and polar anti-addition mechanisms are postulated, both triggered by HBr, which is evidenced also to take part in the Z/E isomerization of the product. The proposed mechanism is well supported by ab initio calculations at the MP2/6-31+G* level with Ahlrichs' SVP all-electron basis for Br. Implicit solvation in CH2Cl2 has been included using the PCM and/or SMD continuum solvent models. Comparative case studies have been performed involving the B3LYP/6-31+G* with Ahlrichs' SVP for Br and MP2/Def2TZVPP levels. The mechanistic studies resulted in development of a procedure for stereoselective bromoboration of acetylene yielding E/Z mixtures of dibromo(bromovinyl)borane with the Z-isomer as a major product (up to 85%). Transformation to the corresponding pinacol and neopentyl glycol boronates and stereoselective decomposition of their E-isomer provided pure (Z)-(2-bromovinyl)boronates in 57-60% overall yield. Their reactivity in a Negishi cross-coupling reaction was tested. An example of the one-pot reaction sequence of Negishi and Suzuki-Miyaura cross-couplings for synthesis of combretastatin A4 is also presented.

Detecting Students’ Misconception in Simple Harmonic Motion Concepts Using Four-Tier Diagnostic Test Instruments

This research aims to develop the test instrument that is feasible in terms of validity, reliability, and difficulty level and to identify students' misconceptions in simple harmonic motion concepts. The development stages used in this research were the modifications result from Oriondo Dalo-Antonio, which included: (1) planning and design development, (2) trying out, and (3) measurement and interpretation of results. The instrument has been developed and categorized as effective because it is declared valid and reliable based on the criteria of the lowest and highest limit of the INFIT MNSQ which is 0.77 and 1.30, all test items are fitted with the PCM model, and the instrument's reliability has an item reliability value of 0.73 with a good category. The test instrument was applied to 60 students of the tenth-grade of senior high school. Based on the results, the four-tier test instrument developed was able to identify students' conceptual understanding of 36.4%, and 17.7% of students only understood parts of concepts, 40.7% of students experienced misconceptions, and 5.2% of students did not know the concept. The biggest misconception occurred in the subtopic frequency of simple harmonic motion by 75%, the relationship of the rope length with the pendulum vibration period by 60%, and 58.3% about the relationship between the total spring constant and the spring frequency. The instrument developed in this research was able to detect students' misconceptions, especially student learning experiences about simple harmonic motion

Theoretical investigation using DFT of quinoxaline derivatives for electronic and photovoltaic effects

Photovoltaic properties of solar cells based on fifteen organic dyes have been studied in this work. B3LYP/6-311G (d,p) methods are realized to obtain geometries and optimize the electronic properties, optical and photovoltaic parameters for some quinoxaline derivatives. The results showed that time dependent DFT investigations using the CAM-B3LYP method with the polarized split-valence 6-311G (d,p) basis sets and the polarizable continuum model PCM model were sensibly able to predict the excitation energies, the spectroscopy of the compounds. HOMO and LUMO energy levels of these molecules can make a positive impact on the process of electron injection and dye regeneration. Gaps energy ΔEg, short-circuit current density Jsc, light-harvesting efficiency LHE, injection driving force ΔGinject, total reorganization energy λtotal and open-circuit photovoltage Voc enable qualitative predictions about the reactivity of these dyes.

Structure and electronic spectra of neutral and protonated forms of anticonvulsant drug lamotrigine.

In this work, the geometry, acid-base properties, pKa, electronic spectra, and fluorescence spectrum of anticonvulsant drug lamotrigine (LTG) are investigated with the DFT/TD-DFT method and PCM solvent model. Calculated transition with the B3LYP functional at 295 nm corresponds to experimental absorption transition at 306 nm in water. In acidic conditions, the computed maximum transition occurs at 249 nm, comparing with experimental one at 270 nm. The dependence of calculated transitions on density functional used and different solvents in PCM model was studied. The computed transition of fluorescence is at 435 nm, while experimental occurs at 370 nm. Maps of electrostatic potential (MEPs) for S0 and S1 reveal that the ground state of LTG is more polar than the first excited state. Structurally, in the excited state of LTG, the triazine ring is noticeably distorted. Graphical Abstract Molecular elecrostatic potentials for S0 and S1 states of the lamotrigine molecule.

THEORETICAL INVESTIGATION OF MOLECULAR STRUCTURE, HOMOLUMO, HYPERPOLARIZABILITY, NBO ANALYSIS AND DENSITY OF STATES CALCULATION OF BUTENAFINE

Molecular geometry vibrational wave number of butenafine was investigated using HartreeFock and DFT method with HF and B3LYP/6-31+G(d,p) basis set. The potential energy distribution of the vibrational wave number is found to be in good agreement with experimental values. A detailed NBO analysis of butenafine was done with B3LYP method. U-V visible absorption spectra of the titled molecule is calculated by PCM model using water as solvent. The U-V visible spectra of the titled molecule dissolved in water were recorded in the range of 200-900 nm. The calculated values of U-V spectra are the most reproduced experimental data. The density of states, Homo-lumo and electrostatic potentials were calculated and analyzed. The dipole moment and hyperpolarizability result shows the butenafine has non linear optical properties. The natural bonding analysis was calculated by HF and B3LYP method.

Light emission colour modulation study of oxyluciferin synthetic analogues via QM and QM/MM approaches.

Firefly oxyluciferin is the chemical product of bioluminescence responsible for light emission. Experiments have already shown that different analogues of natural oxyluciferin, exhibit different emission colours. In particular, the structure of natural oxyluciferin has been modified by atom or group substitutions. However, a rationalization of the origin of the bioluminescence emission colour modulation of these analogues has still not been reported. For these reasons, the aim of this study is to explain the influence of structural modifications within the natural oxyluciferin on the colour modulation of bioluminescence. To do this, natural firefly oxyluciferin and three synthetic analogues whose experimental bioluminescence spectra are red- and blue-shifted compared to the natural one were studied. The absorption and emission transition energies have been calculated at the Time-dependent density functional theory (TD-DFT) level using both quantum mechanics (QM) and quantum mechanics/molecular mechanics (QM/MM) methods. Moreover, the solvent (water using the PCM model) and the protein surrounding effect have also been considered. The predicted emission spectra are in quite good agreement with the available experimental spectra, validating the methodology followed in this study. In particular, it was demonstrated that using the QM/MM approach, and considering explicitly the protein environment, the experimental bioluminescence spectra can be reproduced. Furthermore, this study shows that the substitution within the oxyluciferin structure causes a change of its electronic distribution and energies of the HOMO and LUMO orbitals involved in the vertical transitions, leading to different light emission colours. This work will promote future studies focused on luciferin mutations guided by the prediction of their bioluminescence emission spectra.

Acceptor/Donor End Capped Phenylene-Thiophene Co-oligomers Toward Efficiencies Organic Electronic Devices

In this paper, geometrical (in ground and excited states), electronic, optical and charge transfer properties, (ionization potentials (IP), electron affinities (EA) and HOMO-LUMO gaps (ΔEH-L), as well as the lowest excitation energies (Eex) and reorganization energies) of the phenylene-tiophene oligomers are studied by the density functional theory (DFT) and Time-dependent DFT approaches. Based on the density functional theory (DFT/B3LYP and CAM –B3LYP functional with 6-31G (d,p) basis set), we will highlight the effect of terminal acceptor/donor (CN, NO2, and CF3) /OCH3, N(CH3)2 substituents on thiophene-phenylene derivatives. The excited state indicates more planar structures of the co-oligomers, which leads to a decrease in the (HOMO-LUMO) gap compared with the ground state, especially when the acceptor character increases. Furthermore, the vinyl spacer and cyanide ((–CN) functional group (Compound C8) stabilize the LUMO levels of energy and improve the transport properties of the thiophene-phenylene derivatives. Comparing with the donor groups, the results show that the electron withdrawing substituents are remarkable on the energy levels of the frontier molecular orbitals, and on the transport charge proprieties in these co-oligomers. Thus, the LUMO energy levels become more stabilized for co-oligomers having more acceptor moieties and the HOMO–LUMO energy gap is reduced, therefore, the improvement of the conduction properties of these species is, then, observed. Moreover, the absorption spectra, computed in the presence or not of solvent at PCM model in chloroform, shows that the increase of acceptor character induces a red shift and important absorption intensity. The decrease injection barrier and smaller reorganization energies are revealing that our designed co-oligomers would be an efficient hole as well as electron transfer materials. The predicted values have shown that the designed derivatives would be efficient for the organic field effect transistors, photovoltaics and light emitters.

When biomolecules meet 2-hydrazinopyrazine: from theory through experiment to molecular levels using a wide spectrum of techniques.

The design of drug structures that are non-toxic, easily transported and permeable to cellular barriers is currently one of the most growing research trends. Indeed, the structural similarity of 2-hydrazinopyrazine (2HP) to pyrazinamide, which has been successfully used in anti-tuberculosis therapy, makes 2HP a promising research object. Thus, herein, a complete analysis of the structure of 2HP and its physicochemical and cytotoxic properties was performed. Calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) binding studies were conducted, which demonstrated the higher affinity of 2HP to BSA. Furthermore, cytotoxicity tests were performed, which proved that 2HP was non-toxic to human skin keratinocyte cells. Accordingly, 2HP was initially classified as a compound with potential application. Physicochemical investigations were performed using a wide range of experiments, which were supported by DFT calculations using the B3LYP functional and 6-311+G** basis set. The good correlation, high quality and correctness of the obtained parameters were proven although the data was obtained using independent techniques. Additionally, 42 tautomeric (prototrophic) forms of 2HP were found by searching the conformational hyperspace. The most energy stable 2HP conformer structure and the partial charge distribution were established. The preferred 2HP ionic forms preferred were presented, and models of the equilibrium occurring in aqueous solution were proposed. The hydrophilic character of 2HP was established based on the partition coefficient values determined by both experiment and theory. The PCM and SMD solvent models of water and n-octanol were used.

Calculations of pKa Values of Selected Pyridinium and Its N-Oxide Ions in Water and Acetonitrile.

Pyridine, its N-oxide, and their derivatives are exciting classes of organic bases. These compounds show widespread biological activity, and they are often used in synthesis. In this work results on theoretical calculations of acid dissociation constants as pKa of pyridine, its N-oxide, and their derivatives were done based on the thermodynamic cycle in water and acetonitrile. Additionally, gas-phase basicity (GB) and proton affinity (PA) values were computed for systems studied. All pKa values were obtained using B3LYP, M06-2X, and G4MP2 methods in the gas phase, which were combined with the PCM model calculations (at the Hartree-Fock method) and with the use of four different scale factors alpha. Theoretical GB, PA, and pKa values were then compared with the available experimental ones. Results obtained from B3LYP and M06-2X methods are quite similar and compatible with experimental ones in terms of quality with correlation coefficients values R2 higher than 0.9, whereas results received from G4MP2 deviate strongly. The calculated pKa values are highly sensitive to the scale factors alpha used in the computational procedure. Root-mean-square deviations (RMSD) between both theoretically and experimentally available pKa values of systems studied were also computed. The RMSD values are lower than 0.8 for the best results, suggesting that the theoretical model presented in this work is promising for applications for pKa calculations of different classes of compounds.

Molecular salts of terephthalic acids with 2-aminopyridine and 2-aminothiazole derivatives as potential antioxidant agents; Base-Acid-Base type architectures

Molecular salts of terephthalic acid (TA) with 2-amino-4-chloropyridine (ACP), 2-amino-6-methylpyridine (AMP), 2-aminothiazole (AT) and 2-amino-5-methylthiazole (AMT), were prepared with an intent to get new crystalline materials with improved physical properties. Crystals of the desired compounds were obtained through slow evaporation technique. The solid state structures reveal that proton transfer from acid to aromatic nitrogen of the base occurs, thus affording molecular salts of general representation AT-TA-AT (1), AMT-TA-AMT (2), AMP-TA-AMP (3) and ACP-TA-ACP (4). The NH2 group at position 2 of each amino base is still available to interact with CO to afford planar fragment. The COOH functional groups in TA at para position with respect to each other accommodated the respective base in a 1:2 M ratio (acid:base, respectively) to give almost planar Base-Acid-Base (BAB) fragments. The resultant molecular salts were structurally characterized with the help of FT-IR and X-ray diffraction. The antimicrobial (selected strains), antioxidant (2,2-DiPheny-1-Picry-l-Hydrazyl, DPPH and 2,2′-Azino-Bis(3-ethylbenzoThiazoline-6-Sulphonic acid, ABTS) and enzyme inhibition (AChE, BChE and AGS) potencies of the synthesized Base-Acid-Base type, molecular salts were explored. In addition to improved physical properties, all molecular salts showed promising biological activities.The optimization, natural bonding orbitals (NBOs) and FT-IR analysis of the molecular salts were carried out by DFT/B3LYP/6-311G (d,p) level in PCM model with ethanol solvent. However, frontier molecular orbitals (FMOs) analysis was performed utilizing TD-DFT/B3LYP/6-311G (d,p) level. A comparative analysis reveals that consistency is found between the experimental and theoretical findings of geometric parameters and vibrational frequencies. The inter-molecular hydrogen bond (IHB) and hyper conjugative interactions are characterized by NBO analysis. The chemical stability of molecules is evaluated by FMOs. The energies of FMOs are also used to calculate the global reactivity descriptor parameters. The obtained high softness values indicated that entitled compounds might be biologically active.

DFT-based reactivity and combined QSAR, molecular docking of 1,2,4,5-Tetrazine derivatives as inhibitors of Pim-1 kinase

In the present work we have calculated several DFT reactivity descriptors for 1,2,4,5-Tetrazine at the B3LYP/6–311++G(d,p) level of theory in order to analyze its reactivity in vacuum and solvent phases. Whereas, the influence of the solvent was taken into account employing the PCM model. DFT-based descriptors such as (electronic chemical potential, electrophilicity, condensed Fukui function….) have been determined to predict the reactivity of 1,2,4,5-Tetrazine. A series of eighteen 1,2,4,5-Tetrazine derivatives was studied by using two computational techniques, namely, quantitative structure activity relationship (QSAR) and molecular docking. QSAR models of the antitumor activity of some 1,2,4,5-Tetrazine derivatives were established in gas and solvent phases which exhibited good statistical values for both cases. Whereas, multiple linear regression (MLR) procedure was used to obtain the best QSAR models and the leave-one-out (LOO) method to estimate the predictivity of our models. The most and the least active compounds were docked with the protein (3C4E) to confirm those obtained results from QSAR models and elucidate the binding mode between this type of compounds and corresponding protein.

Molecular properties of 5-(1H-Benzo[D]Oxa, thia, imid azole-2-Yl)-2-methyl quinazolin-4-ol fluorescent brighteners: Theoretical and experimental approach

A series of seven new fluorescent brighteners 5-(1H-benzo[d]oxazole, thiazole, imidazole-2-yl)-2-methyl quinazolin-4-ol were synthesized by chemical reaction of 2-Methyl-4-oxo-3,4-dihydroquinazoline-5-carboxylic acid and derivatives of 2-aminophenol/2-aminothiophenol/1,2-phenylenediamine attributes to its computational and experimental comparison. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations was performed by PCM model maintaining C1 symmetry in ground state both in gas and DMF solvent. The electronic distribution over the molecules has built up strong relationship with its fluorescence quantum efficiency. HOMO and LUMO energies defined electron donor acceptor relationship and shows two distinct plane which are less responsive towards the π-π electronic transition and has inductive electronic effect control their fluorescence properties. The fluorescent brighteners 6a-6g exhibits 0.6–22% and 0.6–7.4% deviation for UV-absorption and fluorescence emission respectively. The theoretical and experimental results for absorption and emission are in well agreement that certainly believe to perform theoretical calculations before experimental setup. The thermally stable fluorescent brightening agents have been systematically investigated. The color space method was used to evaluate the brightening values on polyester fabrics in terms of L*, a* and b*.

Vibrational Fingerprint of Erlotinib: FTIR, RS, and DFT Studies

In this study, we provide the first Fourier-transform infrared absorption spectroscopy (FTIR) and Raman spectroscopy (RS) analysis of a vibrational fingerprint of erlotinib, a drug which is applied in non-small cell lung cancer therapy, in solid state and solution in different pH conditions. Additionally, the performed DFT theoretical calculations in vacuum and PCM models support the interpretation of vibrational spectra and give insight into an optimized spatial configuration of the investigated drug. The present considerations show vibrational structure of erlotinib and details of its molecular geometry. Furthermore, we discuss the pH condition where the protonated –NH+ and C=N+ forms occur and indicate the spectral changes characteristic for the erlotinib protonation. It is of great of importance to better understand biological activity of the drug and to develop new tyrosine kinase inhibitors.

Developing Assessment Instrument to Measure Physics Problem Solving Skills for Mirror Topic

The Problem solving skills are needed to students in physics learning. Physic problem can be seen in
 daily, such as mirror topic. Student who has problem solving skills can solve question of mirror topic
 not only by equation, but also use concepts and principles what he know. This research aimed to
 develop a valid physics assessment to measure problem-solving skills for Senior High School
 Students grade XI. The development stages include: (1) determination for general purpose, (2)
 conceptual definition, (3) operational definition, (4) establishment for indicators, (5) construction for
 grid questions, and (6) determination for test form. The development stage includes: (1) the content
 validation by experts, (2) revision of the instrument, (3) the prepation for research (4) trial and
 empirical validation. The disseminate stage was publication of journal. Subjects of this research was
 55 students of Senior High School 2 Yogyakarta. Students as subjects of this research was chosen
 who had learned mirror topic. According the result of the content validation and the empiric
 validation, assessment instrument was valid to measure physics problem solving skills in mirror
 topic. The content validation has 0,96 for all items, while the empirical validation has 0,97 ± 0,18 for
 Infit MNSQ, it means all items are in accordance with PCM model. the assessment instrument has
 value of goodness of fit un range -0.94 to 1.12 and has level of item difficulty in range -0,94 to 1.12,
 those mean all items in the assessment instrumen are good. Futhermore, the assessment instrument
 is valid in the content validation and the empirical validation and able to measure physics problem
 solving skills. Categories problem-solving skills of subjects obtained of low, medium and high
 category

Development of High-Order Thinking Skills Assessment Instrument for High School Students on Rotational Dynamics

This study aimed to develop a test instrument for high school physical reasoning abilities related to rotational dynamics. This study aimed to determine: Quality of the Instrument Quality of the Higher Order Thinking Ability Instrument in senior high school Physics, including content validity of the expert judgment, empirical validity based on item suitability using the Rasch and PCM models, reliability, and item difficulty index; and profile of high school physics advanced reasoning test scores. This research is research and development. The development model used is based on the Borg & Gall development model. The research was conducted at MAN 1 Bandar Lampung with 42 students in class XI. Using the Quest program, reliability was analyzed using the Quest program, which was represented by internal consistency values and item difficulty indexes analyzed using the Quest program. The results of the ability measurement profile are grouped into three categories presented in the analysis of the Quest program assessment. Research and development resulted in a high-quality thinking ability test instrument for high school physics. The results are the quality of the tool's content based on the actual assessment in the valid category. Empirical validity is based on the suitability of the item with the Rasch model IRT approach with highly reliable criteria. Task difficulty varies from -2.17 to 1.51. Generally, the results of measuring high-level thinking skills show that students have medium-level skills.

Relaxation dynamics of l-alanine in water medium investigated by dielectric relaxation spectroscopy.

The complex dielectric permittivity of L-alanine in aqueous medium at different concentrations and different temperatures were measured in the microwave (0.02 < ν/GHz < 20) frequency region by using open-ended coaxial probe technique. From the reflection coefficient and impedance data, the real and imaginary part of the dielectric permittivity values is determined. It is observed that there is a decrease in the real part of the dielectric permittivity up to certain frequency and an increase in the imaginary part of the dielectric permittivity with increase in the molar concentration of L-alanine in water medium. Based on the experimental data the average relaxation time values are calculated and its behavior is analyzed in terms of bound water and free water molecules. The theoretical dipole moment of L-alanine is calculated at gaseous state as well as in aqueous medium by using PCM and IEFPCM model at HF, DFT/B3LYP and MP2 calculations using 6-311G* basis set. Analysis between experimentally determined parameters and computed dipole moments were discussed. The mean molecular polarizability is calculated from the Lippincott δ function potential model and compared with the Le Fèvre method of polarizability values.

Simulation and performance analysis of an active PCM-heat exchanger intended for building operation optimization

This paper presents a simulation study of an active energy storage device intended to enhance building operation. This device –which is designed for installation in the ceiling plenum of an office, a mechanical room or in other convenient locations– consists of an arrangement of several panels of a phase-change material. It may be charged or discharged as required with an air stream passing between the panels, thus operating as a PCM-air heat exchanger (PCM-HX).The first part of the paper focuses on the design of the PCM-HX. Several design configurations are evaluated; investigated parameters include the PCM-HX dimensions, the number of air channels and airflow rates. The paper also includes an experimental validation of the PCM model. Performance criteria that were considered in the parametric study include the amount of stored heat, the time needed to charge/discharge the PCM storage and the overall energy density of the device.The second part of the paper evaluates different control strategies aimed at reducing peak demand and the size of HVAC system. The impact on peak load of a linear ramp for the temperature setpoint is investigated: it was found that a two hour linear ramp in temperature setpoint –together with a PCM-HX configuration with six air channels– can reduce the peak heating load by 41% as compared to a benchmark case without the PCM-HX.

Analysis of lowest energy transitions at TD-DFT of pyrene in vacuum and solvent.

Polycyclic aromatic hydrocarbons are present in interstellar medium and trapped in water ice. Among these compounds, pyrene has a controversial theoretical excitation spectrum. We carried out time-dependent density functional theory, including the long-range correction functionals, with the aim to help to understand the inversion of the first two UV bands of lower energies. The pyrene molecule was optimized at TD-DFT functionals with Def2svp basis set. The spectrum of pyrene molecule was calculated using implicit and explicit solvent models. The explicit solvent effect was studied, including a cluster of 51 water molecules. The implicit solvent PCM model was used with water and benzene as solvents. CAM-B3LYP and ωB97XD give correct band positions and the ω parameter was also optimized. NBO and frontier molecular orbitals were used to study the UV band inversion. Graphical abstract Analysis of frontier orbitals involved in the lowest energy transitions at TD-DFT of pyrene.

Dynamic simplified PCM models for the pipe-encapsulated PCM wall system for self-activated heat removal

The energy efficiency of traditional PCM wall is low in summer since the PCM storing heat in the daytime will become a secondary heat-source and release the heat into the room again at night. In this paper, a novel pipe-encapsulated PCM wall system for self-activated heat removal is proposed. It integrates PCM, nocturnal radiation cooling and gravity heat-pipe technology, and can realize automatic heat insulation and self-activated removal for buildings. Three simplified models for pipe-encapsulated PCM are developed to predict its thermal characteristics. Model Parameters are determined and identified by using genetic algorithm. The pipe-encapsulated PCM is prepared by RT28 and expanded graphite. An experiment setup is established for model validation. Results shows that the 4R2C PCM model are preferable since the identified parameters are relatively less and the accuracy is also acceptable. Furthermore, a simple application about pipe-encapsulated PCM wall is proposed based on the coupled wall model with 4R2C PCM model. Compared with conventional wall, the internal surface accumulated heat transfer of the pipe-encapsulated PCM wall with night active heat removal in 7 days can be reduced by 74.5% in hot climate. It shows great application potential for energy-saving in buildings.

Iron(III) chloride complexation in hydrothermal solutions: A combined spectrophotometric and density functional theory study

Iron(III) hydrolysis and chloride complexation in hydrothermal solutions was studied experimentally using UV–Vis spectrophotometry and based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) techniques. The strong ligand-to-metal charge transitions (LMCT) at wavelengths below 400 nm were used to obtain the number of absorbing species, molar absorptivities (ε), and equilibrium formation constants, using principle component analysis of the spectra. CAM-B3LYP calculations of molecular geometries, energies and electronic absorption spectra have been undertaken for microsolvated iron(III) hydroxo and chloro complexes with up to four Cl atoms, showing that a combination of explicit first and second shell water solvation, together with PCM models, is required to successfully simulate aqueous UV–Vis spectra. With increasing chloride concentration and temperature, iron(III) chloride complexes become important with FeCl2+, FeCl2+, FeCl3(aq) and FeCl4− forming. Upon the progressive addition of Cl− to the aquated Fe3+ ion the complex geometry changes from octahedral to tetrahedral coordination of the FeCl4− ion. The respective formation constants were derived experimentally between 25° and 200 °C and were in the range: log β0,1 = 1.42–3.24 (25–150 °C), log β0,2 = 1.98–7.37 (25–200 °C), log β0,3 = 2.98–9.03 (100–200 °C) and log β0,4 = 5.27–9.88 (150–200 °C). With increasing chloride concentration and temperature iron(III) chloride complexes become increasingly important species in acid solutions.