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In the room-temperature ionic liquid (IL) of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide ([C8mim][TFSA]), the complex formation of Ni2+ with molecular liquids (MLs), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN), has been examined using ultraviolet (UV)-visible spectroscopy. The overall stability constants log βn, enthalpies , and entropies of the equilibria have been determined to elucidate the mechanism of complex formation. From a comparison of such thermodynamic parameters of the present [C8mim][TFSA] systems with those of the previous systems of 1-ethyl-3-methylimidazolium-based IL, [C2mim][TFSA], the effects of the octyl chain of the imidazolium cation, [C8mim]+, on the complex formation of Ni2+ with MLs have been demonstrated. In [C8mim][TFSA]–ML systems, more stable complexes are formed with MLs in the sequence of AN > DMSO ≫ MeOH. This sequence differs from that of DMSO ≫ AN > MeOH in [C2mim][TFSA]. For the AN systems, the stabilities of [Ni(an)n] in [C8mim][TFSA] are higher as compared to those in [C2mim][TFSA]. In contrast, for the DMSO systems, [Ni(dmso)n] is less stable in the IL with the longer alkyl chain than that in the IL with the shorter chain. The dependence of the alkyl chain length on the stabilities of [Ni(meoh)n] is the least significant among the three MLs. These varieties of the stabilities of Ni2+ complexes with the MLs have been interpreted from the thermodynamic parameters, together with the static interactions in the [C8mim][TFSA]–ML and [C2mim][TFSA]–ML solvents observed by means of 1H and 13C NMR, small-angle neutron scattering (SANS), and infrared (IR) with an ATR diamond prism.

To investigate the effects of adding Au nanoparticles (AuNPs) to TiO2 films on the crystallization, phase transformation, and photocatalysis, films of both TiO2 and TiO2 embedded with AuNPs (Au-TiO2) with various characteristics were prepared by using the dip-coating method with preheating and post-heating treatments. The AuNPs acted as anatase nucleation agents and crystallized a lot of small anatase crystals with sizes of tens of nanometers, which suppressed the growth of anatase crystals that are large enough for them to transform into rutile crystals, resulting in repression of the transformation from anatase into rutile. The AuNPs affected the progress of the photocatalytic and adsorption reactions, resulting in improved photocatalytic activity. Of all the films we tested, the Au-TiO2 film preheated at 400 °C and post-heated at 400 °C (AT400-400), which consisted of small anatase crystals with high covalent character and high crystallinity, contained dispersed AuNPs with the smallest average crystallite size and showed the highest photocatalytic activity. This high activity resulted from the high reaction rate constants for adsorption and photocatalysis.

The thermodynamics of complex formation of Ni2+ with molecular liquids (ML), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN) in the ionic liquid (IL) of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C2mim][TFSA]) has been elucidated using ultraviolet (UV)-visible spectroscopy. X-ray structural analyses for single crystals grown from Ni2+-[C2mim][TFSA]-DMSO and -AN solutions at high ML contents have shown that six DMSO oxygen or AN nitrogen atoms coordinate with Ni2+ to form octahedral structures of [Ni(dmso)6](TFSA)2 and [Ni(an)6](TFSA)2, respectively. This is the same in the case of the Co2+ complex of [Co(dmso)6](TFSA)2. UV-visible spectroscopic experiments have revealed that the TFSA- anions that initially combine with Ni2+ in the IL are replaced with ML molecules in the IL-ML systems in three steps with increasing ML content. The electron donicities of the three MLs are larger in the order of DMSO > MeOH > AN. However, the stability of each complex does not simply depend on this order; the stability is higher in the order of [Ni(dmso)n] > [Ni(an)n] > [Ni(meoh)n]. In other words, the stability of the MeOH complexes is lower than that of the AN ones, despite the higher electron donicity of MeOH. The reasons for the order of the complex stabilities have been interpreted on the molecular scale, according to the stepwise enthalpies and entropies determined, together with the strength of the hydrogen bonding between the MLs and the imidazolium ring and the formation of MeOH clusters in [C2mim][TFSA].

In the room-temperature ionic liquid (IL) of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide ([C8mim][TFSA]), the complex formation of Ni2+ with molecular liquids (MLs), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN), has been examined using ultraviolet (UV)-visible spectroscopy. The overall stability constants log βn, enthalpies , and entropies of the equilibria have been determined to elucidate the mechanism of complex formation. From a comparison of such thermodynamic parameters of the present [C8mim][TFSA] systems with those of the previous systems of 1-ethyl-3-methylimidazolium-based IL, [C2mim][TFSA], the effects of the octyl chain of the imidazolium cation, [C8mim]+, on the complex formation of Ni2+ with MLs have been demonstrated. In [C8mim][TFSA]-ML systems, more stable complexes are formed with MLs in the sequence of ANDMSO ≫ MeOH. This sequence differs from that of DMSO ≫ ANMeOH in [C2mim][TFSA]. For the AN systems, the stabilities of [Ni(an)n] in [C8mim][TFSA] are higher as compared to those in [C2mim][TFSA]. In contrast, for the DMSO systems, [Ni(dmso)n] is less stable in the IL with the longer alkyl chain than that in the IL with the shorter chain. The dependence of the alkyl chain length on the stabilities of [Ni(meoh)n] is the least significant among the three MLs. These varieties of the stabilities of Ni2+ complexes with the MLs have been interpreted from the thermodynamic parameters, together with the static interactions in the [C8mim][TFSA]-ML and [C2mim][TFSA]-ML solvents observed by means of 1H and 13C NMR, small-angle neutron scattering (SANS), and infrared (IR) with an ATR diamond prism.

The liquid structures of binary acetonitrile (AN)–dimethyl sulphoxide (DMSO) and N,N-dimethylformamide (DMF)–DMSO mixtures were investigated by the X-ray scattering method. Comparison of the X-ray scattering data of AN–DMSO liquid mixtures with those of neat AN and DMSO revealed that the intermolecular AN–DMSO interactions are practically not detected; that is, the X-ray scattering data of the liquid mixtures are well reproduced by summing up those of neat AN and DMSO weighted by their mole fractions. The same applies for DMF–DMSO mixtures. Thus, each component solvent molecule independently forms self-assembled clusters in the liquid mixtures, the structures of which are the same as those in the neat liquids. The clusters are mixed to form macroscopically homogeneous liquid mixtures. The thermodynamic quantities on mixing process for the AN–DMSO, DMF–DMSO and AN–DMF systems in the literature are well elucidated on the basis of the microscopic structure of the liquid mixtures.

A two-dimensional imaging system of X-ray absorption fine structure (XAFS) has been developed at beamline BL-4 of the Synchrotron Radiation Center of Ritsumeikan University. The system mainly consists of an ionization chamber for I(0) measurement, a sample stage, and a two-dimensional complementary metal oxide semiconductor (CMOS) image sensor for measuring the transmitted X-ray intensity. The X-ray energy shift in the vertical direction, which originates from the vertical divergence of the X-ray beam on the monochromator surface, is corrected by considering the geometrical configuration of the monochromator. This energy correction improves the energy resolution of the XAFS spectrum because each pixel in the CMOS detector has a very small vertical acceptance of ∼0.5 µrad. A data analysis system has also been developed to automatically determine the energy of the absorption edge. This allows the chemical species to be mapped based on the XANES feature over a wide area of 4.8 mm (H) × 3.6 mm (V) with a resolution of 10 µm × 10 µm. The system has been applied to the chemical state mapping of the Mn species in a LiMn(2)O(4) cathode. The heterogeneous distribution of the Mn oxidation state is demonstrated and is considered to relate to the slow delocalization of Li(+)-defect sites in the spinel crystal structure. The two-dimensional-imaging XAFS system is expected to be a powerful tool for analyzing the spatial distributions of chemical species in many heterogeneous materials such as battery electrodes.

Reactions of a tetravanadate anion, [V(4)O(12)](4-), with a series of lanthanide(III) salts yield three types of lanthanide complexes of macrocyclic polyoxovanadates: (Et(4)N)(6)[Ln(III)V(9)O(27)] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6)], (Et(4)N)(5)[(H(2)O)Ho(III)(V(4)O(12))(2)] (7), and (Et(4)N)(7)[Ln(III)V(10)O(30)] [Ln = Er (8), Tm (9), Yb (10), Lu (11)]. Lanthanide complexes 1-11 are isolated and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and extended X-ray absorption fine structure spectroscopy (EXAFS). Lanthanide complexes 1-6 are composed of a square-antiprism eight-coordinated Ln(III) center with a macrocyclic polyoxovanadate that is constructed from nine VO(4) tetrahedra through vertex sharing. The structure of 7 is composed of a seven-coordinated Ho(III) center, which exhibits a capped trigonal-prism coordination environment by the sandwiching of two cyclic tetravanadates with a capping H(2)O ligand. Lanthanide complexes 8-11 have a six-coordinated Ln(III) center with a 10-membered vanadate ligand. The structural trend to adopt a larger coordination number for a larger lanthanide ion among the three types of structures is accompanied by a change in the vanadate ring sizes. These lanthanide complexes are examined by EXAFS spectroscopies on lanthanide L(III) absorption edges, and the EXAFS oscillations of each of the samples in the solid state and in acetonitrile are identical. The Ln-O and Ln···V bond lengths obtained from fits of the EXAFS data are consistent with the data from the single-crystal X-ray studies, reflecting retention of the structures in acetonitrile.

The XAFS spectra were measured at around the Ag K-edge of the Ag(I) ion in nitromethane (NM) with a variety of concentrations of pyridine (PY). In NM without PY, the Ag(I) ion is tetrahedrally solvated by four NM molecules similar to those in most solvents. The Ag–O bond length in NM solvent is longer than that in aqueous solution, indicating the low donating ability of NM. The mono-, bis-, tris-, and tetrakis-pyridine complexes are formed in NM by the addition of PY. The EXAFS analyses reveal that the structure of the formed PY complex in NM is linear for Ag(py)(nm)+, linear for Ag ( py ) 2 + , triangular for Ag ( py ) 3 + , and tetrahedral for Ag ( py ) 4 + . The longer Ag–O bond length for Ag(py)(nm)+ than that for Ag ( nm ) 4 + and the release of bound NM molecules at the formation of Ag(py)(nm)+ are interpreted to be due to the strong σ donating property of PY. The Ag–N bond length (220 pm) for Ag ( py ) 3 + is intermediate between 216 pm for Ag ( py ) 2 + and 228 pm for Ag ( py ) 4 + . The formation equilibria of Ag ( py ) 3 + and Ag ( py ) 4 + are analyzed on the basis of the changeover of EXAFS spectra as a function of the total concentrations of Ag+ and PY in NM.

The liquid structures of benzene, toluene, aniline, benzaldehyde and nitrobenzene were investigated by the X-ray scattering method. The X-ray scattering data were analysed by a method without constructing any structure models. The obtained liquid structure of benzene is different from the previous X-ray scattering results which were derived from the quasi-lattice structure for the liquid based on the crystal structure of benzene. This is because a molecular arrangement which is not found in the crystal structure is left out of consideration. In liquid toluene, benzaldehyde and nitrobenzene, two molecules are associated with the dipole–dipole interaction in the antiparallel fashion. Two aniline molecules are hydrogen-bonded in liquid aniline. The third molecule weakly interacts with the other two in liquid toluene, aniline and benzaldehyde. In liquid nitrobenzene, the parallel dipole–dipole interaction of the third molecule with another one is present in the coplanar form. The substituent effect on the liq...

The liquid structures of water-tetrahydrofuran (THF) and water-acetone binary mixtures were investigated by the X-ray scattering method. Comparison of the X-ray scattering data revealed that only one kind of intermolecular water-organic molecule interaction is commonly involved throughout all mole fractions of these liquid mixtures, in addition to the intermolecular water-water and organic molecule-organic molecule interactions, which are present in neat water and organic liquids, respectively. On the basis of this finding, we proposed a new analytical method for studying liquid mixtures. By this method the structural information on the intermolecular water-organic molecule interaction as well as the concentrations of the intermolecular water-water, water-organic molecules, and organic molecule-organic molecule interactions were obtained. Combining the concentrations of the intermolecular water-water interaction with the concentrations of water in the liquid mixtures, the number of water-water hydrogen bonds at various mole fractions was experimentally determined for the first time. From the dependence of the number of water-water hydrogen bonds on the composition of the liquid mixtures, the change of the size of the self-associated water-water clusters was deduced.

A simple approach for determining a liquid structure using X-ray scattering data, in which a liquid structure is uniquely evaluated without construction of any plausible structure models, has been applied to liquid acetonitrile, acetone and cyclohexane. For a pair of molecules, a given point within a molecule is located at the origin with a given molecular orientation. The site of the given point of another molecule is defined by the polar coordinates and the molecular orientation is treated by three Eulerian angles. These parameters are optimized by a non-linear least-squares calculation applied to X-ray scattering data. The reliability of the method was examined by determining the liquid structure of polar acetonitrile and the obtained intermolecular interatomic distances are in good agreement with the previously reported values. The method was then successfully applied to the determination of the liquid structure of acetone and cyclohexane. Especially for nonpolar cyclohexane, the construction of a variety of plausible structural models is very difficult. It was revealed that acetone has an ordered liquid arrangement similar to that found in its crystal, although the intermolecular distances in liquid acetone are different from those in the crystal. On the other hand, the liquid structure of cyclohexane is disordered.

The local structures around silicon and phosphorous atoms in R 2 O–SiO 2 –P 2 O 5 (R = Li, Na and K) glasses have been investigated using Si and P K-edge XAFS spectroscopy by transmission mode at BL-4 and BL-3 at the synchrotron facility in Ritsumeikan University. As a result of XANES and EXAFS analyzes, six-coordinated silicon atoms were observed in the glasses. The fraction of six-coordinated silicon atom changed with increasing of the concentration of alkali oxide and P 2 O 5 . For the change of concentration of alkali oxide, it takes maximum values which are 60% in Li 2 O, 90% in Na 2 O and 85% in K 2 O system at 20 mol% alkali oxide. It gradually increased up for the increase of the concentration of P 2 O 5 to 55% in Li 2 O, 80% in Na 2 O and 90% in K 2 O system. The Si–O inter-atomic distance in the glasses changes from 1.63 to 1.79 A with increasing the fraction of six-coordinated silicon atom. On the other hand, it was not observed the local structural change around the phosphorous atom.

Intermolecular interactions between water and N,N-dimethylformamide (DMF) in their mixtures were investigated by Raman spectroscopic and X-ray diffraction methods and by molecular orbital calculations. The Raman spectroscopic and X-ray diffraction measurements indicated the formation of water-DMF associates or clusters in the mixtures. Theoretical calculations for the electron density of H2O-HOH-OH2, of electron density on the oxygen atom of the water molecule in the DMF-HOH-DMF associate due to the accumulation of electrons transferred from DMF to the oxygen atom of the terminal water molecule. The increase resulted in a larger donicity of the terminal H2O compared to normal water. Although the donor number DN of the water molecule in the DMF-H2O-DMF associate was not determinable, it was estimated to be DN ∼ 30 from the behavior of the preferential solvation of the cobalt(II) ion in water-DMF mixtures.

The liquid structure of acetonitrile (AN), propionitrile (PN), acrylonitrile (ACN), and benzonitrile (BN) was investigated by the transmission mode X-ray diffraction method with a newly developed CCD detector at room temperature and one atmospheric pressure. The nitriles were shielded in a thin wall glass tube. The reduced intensities, si(s), extracted from the measured intensities were compared with those obtained by the X-ray diffraction measurements with the θ–θ type reflection mode for benzonitrile and N,N-dimethylformamide (DMF) as the reference. In all the nitriles it was found that molecules are arrayed in the zigzag form as found in previous studies for AN. The non-bonding N···C (nitrile carbon) distance between the anti-parallel adjacent molecules was 340 pm for all nitriles. The intermolecular C···C distance between next neighbour molecules was 420 pm for CH2···CH2 in AN, 430 pm for CH3···CH3 in PN, 425 pm for CH···CH in ACN, and 390 pm for C6H5···C6H5 in BN. The short C6H5···C6H5 distance was explained in terms of the π–π stacking interactions of the aromatic rings. DMF molecules interact each other through dipole–dipole interactions, and the O···C distance of 320 pm at the O···H–CO– interaction through the formyl proton may partly contribute to the intermolecular interactions. The distance between parallel DMF molecules in a plane was estimated to be 743 pm. The diffraction data were well explained in terms of a weak layered structure of DMF, and the layers were separated by about 365 pm.

The solvation structure of chloride, bromide, and iodide ions, X − , in dimethyl sulfoxide (DMSO) has been investigated by using Raman spectroscopy and large angle X-ray diffraction under ambient conditions. The positively charged sulfur atom in DMSO interacts with X − and slightly positively charged methyl groups in the coordinating molecules also interact with X − . The X − S, X − ···C, and X − ···O distances are determined as follows: Cl − S: 416, Cl − ···C: 363, Cl − ···O: 543, Br − S: 433, Br − ···C: 372, Br − ···O: 544, I − S: 437, I − ···C: 374 and I − ···O: 520 pm. The coordination numbers of DMSO molecules around the anions are six, seven and eight for Cl − , Br − and I − ions, respectively, with the uncertainty of ±1. Rather large uncertainties in the measured solvation numbers suggest large fluctuations in the solvation structure of the anions.

We have constructed an x-ray absorption fine structure (XAFS) spectrometer at BL-4 using the compact superconducting synchrotron radiation (SR) source at Ritsumeikan University. BL-4 is simply designed and consists of a slit, a double-crystal monochromator, and two detectors. The mechanical movement of the monochromator is in the range from 15° to 75°. By using Si(220), Ge(220), and InSb(111) crystals, the XAFS spectrometer covers the K-edge absorption energies of elements from silicon to zinc under atmospheric pressure. The incident x-ray intensity is measured by an ionization chamber with a path length of 4.5 cm. The transmitted x-ray intensity after passing through a sample is monitored by either an ionization chamber with a path length of 31 cm or a scintillation counter. The steep decrease of x-ray intensities above 5 keV is characteristic of the spectrum of photons emitted from the compact SR source and the photon flux at 10 keV is two to three orders of magnitude smaller than that at 5 keV. Hence, ...

A beamline equipped on the compact superconductive synchrotron radiation (SR) facility at Ritsumeikan University was designed for performing extended X-ray absorption fine structure (EXAFS) analyses of solutions and solids. The introduction of three different crystals, Si(220), Ge(220), and InSb(111), as the monochromator of the EXAFS spectrometer covers the K-edge absorption energy range of elements with low atomic numbers from silicon (atomic number 14) through zinc (30). The LIII-edge of the iodide ion could be measured by Si(220) and Ge(220). It is, however, not possible to measure the absorption of the bromide ion with this equipment. Using this spectrometer, the solvation structure of Cl- and I- ions was investigated in water, methanol, and ethanol under atmospheric pressure.

Heats of solution of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) in acetonitrile, 1,2-dichloroethane, N,N-dimethylformamide, dimethyl sulfoxide, nitromethane, propylene carbonate, pyridine and water were measured at 25 °C and the enthalpies of the transfer of 18-crown-6 from waterto the aprotic solvents were derived. The thermodynamic quantities, Δ G1°, Δ H1° and TΔ S1°, for the formation of the[M(18-crown-6)]+ (M+ = Na+, K+, Rb+, Cs+, NH4 +) complexeswere determined by titration calorimetry in dimethyl sulfoxide containing0.1 mol dm-3 (C2H5)4NClO4 as a constant ionic medium at 25 °C. These thermodynamic quantities suggest that the complexationof 18-crown-6 with the alkali-metal ions mainly reflects the different solvationof 18-crown-6 and also the different degree of solvent structure.

The structure of liquid formamide has been investigated by means of X-ray diffraction and NMR at high temperatures and high pressures (HTHP). The temperatures were fixed at 298 K and 373 K, and the pressures employed were 0.1, 20, and 40 MPa for the X-ray diffraction studies, while the NMR measurements were carried out over the temperature range from 300 K to 395 K at 0.1 MPa and over the pressure range from 0.1 to 200 MPa at 298 K. Formamide has a network structure consisting of a mixed ring and head-and-tail-type linear structures through N-H⋯O hydrogen bonds at 298 K and 0.1 MPa, and the ring structure, which has weaker hydrogen bonds than the linear structure, is broken with increasing temperature to change to the linear-type structure. On the other hand, the linear structure changes to the ring structure, having a more compact molecular arrangement than the linear one, with the increase in pressure.

Thermodynamic data of the complexation of cobalt(II), nickel(II), and copper(II) ions with pyridine (py), 2-methylpyridine (2Me-py), 3-methylpyridine (3Me-py), and 4-methylpyridine (4Me-py) have been determined by calorimetry and spectrophotometry in acetonitrile (MeCN) containing 0.1 mol dm-3 (C2H5)4NClO4 as a constant ionic medium at 25 °C. The calorimetric and spectrophotometric data for py, 3Me-py, and 4Me-py revealed the formation of [ML]2+, [ML2]2+, [ML3]2+, and [ML4]2+ (M = Co2+, Ni2+, Cu2+; L = py, SMe-py, 4Me-py). For 2Me-py, on the other hand, the formation of only one complex, [M(2Me-py)]2+ (M = Co2+, Ni2+), was detected. The stepwise thermodynamic quantities and the individual electronic spectra of the complexes suggest that all of these have a six-coordinate octahedral structure. The stability of the [M(2Me-py)]2+ (M = Co2+, Ni2+) complexes is much lower than that of the corresponding py, 3Me-py, and 4Me-py complexes. The difference in the stability of the 2Me-py complexes is mainly due to their unfavorable entropy changes because the differences of enthalpies for all the complexes are not so significant. The free energies for the formation of the mono complexes follow the order Mn(II) > Co(II) > Ni(II) > Cu(II) < Zn(II) for the py, 3Me-py, and 4Me-py systems. The ΔH°1 values vary in the same order and the ΔS°1 values are similar. Hence, the stability difference of the mono complexes originates from the enthalpic term

Improvements of XAFS (X-Ray Absorption Fine Structure) measurements in the time domain are summarized and several examples of structure determination of reaction intermediates by the EXAFS (Extended X-Ray Absorption Fine Structure) method are given. The local structure around the copper(II) or cobalt(II) ion is described in the reaction intermediate in the metal substitution reaction of the homodinuclear mercury(II) porphyrinato (5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin; H6tpps) complex in an acetate buffer determined by the stopped-flow EXAFS (SF-EXAFS) method, which was developed by us. Comparison of the bond lengths in the intermediates with those in the reactants and the products of the metal substitution reaction, the structure of which has been determined by the same method, revealed the cause of the instability of the reaction intermediates.

The local structure around the cobalt(II) ion in the reaction intermediate formed during the metal substitution reaction of the homodinuclear mercury(II) porphyrin (5,10,15,20-tetrakis(4- sulfonatophenyl)porphyrin; H2tpps4- ) complex with a cobalt(II) ion in an acetate buffer has been determined by the stopped-flow EXAFS method. The structure of the reactant and the product of the above reaction has also been determined by the same method. The coordination geometry around the cobalt(II) ion in the heterodinuclear intermediate, [Hg(tpps)Coll]2- , is six-coordinate octahedral with four additional water and/or acetate oxygen atoms. The Coll-N and Coll-O bond lengths in the intermediate are 212(2) and 221(1) pm, respectively. The product, [Coll(tpps)]4-, has a six-coordinate octahedral structure, the Coll-N and Coll-O bond lengths being 203(1) and 215(1) pm, respectively. The Coll-N bond length in the intermediate is ca. 9 pm longer than that in the product. The Coll-O bond length in the intermediate is also ca. 9 pm longer than that of 212(1) pm in the reactant, the cobalt(II) acetato complex, and ca. 6 pm longer than that in the product. The longer Coll-O bond in the intermediate as compared to those in the reactant and in the product appears to be responsible for the instability of the intermediate. The oxidized product, [Colll(tpps)]3-, has a six-coordinate structure with two additional Colll-O bonds. The Colll-N and Colll-O bond lengths are 189(1) and 197(2) pm, respectively, and are much shorter than those in [Coll(tpps)]4-.

The solution structure of the manganese(II) ion in acetonitrile (methyl cyanide, AN) has been determined by an X-ray diffraction technique: there are 6.0 ± 0.2 Mn−N bonds and the Mn−N bond length is 221 ± 1 pm. The solvation structures of the manganese(II) ion in propiononitrile (ethyl cyanide, PN), butyronitrile (propyl cyanide, BuN), isobutyronitrile (isopropyl cyanide, iBuN), valeronitrile (butyl cyanide, VN), and benzonitrile (phenyl cyanide, BzN) have been determined by extended X-ray absorption fine structure spectroscopy. The manganese(II) ion in all of these nitriles is six-coordinate octahedral with an Mn−N bond length of 221 ± 1 pm. The activation parameters for solvent exchange on the manganese(II) ion in the six nitriles have been determined by the nuclear magnetic resonance line broadening technique at various temperatures and pressures. The values of the rate constant ( , s-1), activation enthalpy (ΔH⧧, kJ mol-1), activation entropy (ΔS⧧, J mol-1 K-1), and activation volume (ΔV⧧, cm3 mol-1)...

Structural parameters of solvated neodymium(III), gadolinium(III), thulium(III) and ytterbium(III) ions in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures have been obtained by an extended X-ray absorption fine structure (EXAFS) method. It revealed that the metal–oxygen bond length is shortened and the coordination number is thus decreased with increasing DMA content in the mixture. Interestingly, the decrease in the coordination number takes place evidently at a lower DMA content for the thulium(III) ion than the neodymium(III) ion, i.e., the geometry change is more favorable for the metal ion with a smaller ionic radius. 89Y NMR chemical shifts also demonstrate that the coordination number decreases with increasing DMA content in the mixture, and the profile of varying coordination number is similar to that for the thulium(III) ion. This indicates that the strong solvation steric effect operates with both thulium(III) and yttrium(III) ions in the DMF–DMA mixture. Variations of metal–oxygen bond length for other metal systems in the mixture indicate that, relative to the thulium(III) ion, the gadolinium(III) ion experiences a less strong solvation steric effect, and the neodymium(III) ion even less. Structural parameters have also been determined for a series of lanthanoid(III) ions in both DMF and DMA. The LnIII–O bond length in DMA is generally shorter than that in DMF, and the difference is smallest for the lanthanum(III) ion, and largest for the lutetium(III) ion. The difference is thus larger for a metal ion with a smaller ionic radius, implying that the solvation steric hindrance is enhanced with decreasing ionic radius.

The solvation structure of the silver(1) ion in neat N,N -dimethylformamide (DMF), neat acetonitrile (AN) and their mixtures has been determined by the X-ray diffraction method at 25 °C. In neat DMF and AN, the silver(1) ion forms the tetrahedral [Ag(dmf) 4 ]+ and [Ag(an) 4 ]+ complexes with the AgO and AgN bond lengths of 233(1) and 226(1) pm, respectively. The tetrahedral [Ag(dmf) 2 (an) 2 ]+ complex is the predominant species in 3:1 and 2:1 DMF:AN molar mixtures.In the 1:2 DMF-AN mixture, the tetrahedral [Ag(dmf)(an) 3 ]+ complex is formed as the main species. The silver(1) ions are present as an equilibrium mixture of [Ag(dmf) 2 (an) 2 ]+ and [Ag(dmf)(an) 3 ]+ (ca. 1:1) in the 1:1 DMF-AN mixture.Thus, a preferential solvation of the silver(1) ion by AN occurs in DMF-AN mixtures, as expected from their solvation energies in each solvent. The AgO bond length in the [Ag(dmf) 2 (an) 2 ]+ and [Ag(dmf)(an)3]+ complexes is 237(3) and 241(3) pm, respectively, and increases with the number of AN molecules within the complexes. On the other hand, the AgN bond length remains practically unchanged by the coordination of DMF molecules; 224(2) pm in [Ag(dmf) 2 (an) 2 ]+ and 324(1) pm in [Ag(dmf)(an) 3 ]+.

It has been known that blends of poly(e-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) show a miscibility window in a relatively narrow range of copolymer composition in SAN. In order to study the interactions in this miscibility window in detail, FTIR and calorimetric measurements were carried out by using low molecular weight analogues corresponding to monomers of each polymer, because respective homopolymer pairs are not miscible. The FTIR study showed shifts of spectral peaks that is thought as a proof of presence of specific interactions. The acid−base self-interaction energies (Eii) and association energies for respective pairs (Eij) were also estimated by the detailed study of interactions by calorimetry. If the FTIR results were combined with the calorimetric ones, the acid−base spectral shifts of peaks, Δνab (CO stretch, C⋮N stretch, and benzene ring out-of-plane CH bending), indicated a linear relation with Eij values that fits well with Drago's treatment based on quantum mechanics...

The complexation of 1, 4, 7, 10-tetraoxacyclododecane (12-crown-4) with sodium, potassium, rubidium, cesium and ammonium ions has been studied by titration calorimetry in N, N-dimethylformamide (DMF) and water containing 0.1mol dm-3 (C2H5)4NClO4 and (C2H5)4NCl, respectively, as constant ionic media at 25°C. A very small heat of complexation other than the heat of dilution of titrant was evolved in the course of the titration of sodium, potassium, rubidium, cesium and ammonium ions with 12-crown-4 in water; thus, the complexation of 12-crown-4 with these cations is expected to be very weak. The formation of [M(12-crown-4)]+ and [M(12-crown-4)2]+ (M=Na+, K+, Rb+, Cs+) complexes was revealed in DMF, and their formation constants, reaction enthalpies and entropies were determined. On the other hand, no significant heat ascribable to complexation was liberated for the ammonium 12-crown-4 DMF solutions, and the formation of the ammonium 12-crown-4 complex was very weak, practically negligible. The cavity size of 12-crown-4 is 57pm in radius, while the alkali-metal ion has an ionic radius of 116-181pm. Since 12-crown-4 is too small to fully accommodate any alkali-metal ion, the formation of the [M(12-crown-4)]+ and [M(12-crown-4)2]+ (M=Na+, K+ Rb+, Cs+) complexes results. The formation constants, enthalpies and entropies for the [M(12-crown-4)]+ (M=Na+, K+, Rb+, Cs+) complexes do not differ significantly by metal ions. Thus, in DMF, 12-crown-4 is not able to distinguish metal ions having different sizes.

Complexation of the zinc(II) ion with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) has been calorimetrically studied in 4-methylpyridine (4Me-py) containing 0.1 mol dm−3 (n-C4H9)4NClO4 as a constant ionic medium at 25°C. The formation of [ZnL]2+, [ZnL2]2+, and [ZnL3]2+ (L=bpy, phen), and their formation constants, reaction enthalpies and entropies were determined. Our EXAFS (extended X-ray absorption fine structure) measurements showed that the solvation structure of the manganese(II), cobalt(II), and nickel(II) ions is six-coordinate octahedral in 4Me-py and 3-methylpyridine (3Me-py), while that of the zinc(II) ion is four-coordinate tetrahedral in 4Me-py. Since [ZnL3]2+ is expected to have an octahedral structure, a tetrahedral-to-octahedral structural change should take place at a certain step of complexation. The thermodynamic parameters, especially reaction entropies, indicate that the structural change occurs at the formation of [Zn(bpy)2]2+ and [Zn(phen)]2+.

The complexation of sodium ion with 1,4,7,10-tetraoxacyclododecane (12-crown-4) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) has been studied by titration calorimetry in pyridine (PY) containing 0.1 mol dm-3 (C2H5)4NClO4 as a constant ionic medium at 25 °C. The calorimetric titration data were well explained in terms of the formation of the [Na(12-crown-4)]+, [Na(12-crown-4)2]+, and [Na(18-crown-6)]+ complexes, and their formation constants, reaction enthalpies, and entropies were determined. The formation of [Na(18-crown-6)]+ is much pronounced in PY over N,N-dimethylformamide (DMF) and water, and the stability order is PY > DMF > water. The enthalpy values for the formation of [Na(18-crown-6)]+ are all negative in PY, DMF, and water, and increase in the order PY < DMF < water. The complexation is the least exothermic in water, though sodium ion is the most weakly solvated in water. This is because 18-crown-6 is much stabilized in water by forming hydrogen bonds with water molecules. Despite the stronger electron pair-donating ability of PY than DMF, the complexation is more exothermic in PY than in DMF. This is ascribed to the different solvation number of the sodium ion in P Y and DMF, i.e., the sodium ion is coordinated with a smaller number of solvent molecules in the former solvent than in the latter.

The structure of the solvated manganese(II) ion and the manganese(II) complexes with pyridine (py), 3-methylpyridine (3Me-py) and 4-methylpyridine (4Me-py) in N,N -dimethylformamide (DMF) has been studied by means of X-ray diffraction at 23°C. It was revealed that the manganese(II) ion binds with six DMF molecules and has an octahedral structure in DMF. The MnO (DMF) bond length within [Mn(dmf) 6 ] 2+ is 221(1) pm, practically the same as that (220 pm) within [Mn(H 2 O) 6 ] 2+ in water. The non-bonding Mn … C (DMF) distance is 315(2) pm and the MnOC bond angle is thus 130°. It was also shown that the structure of [Mn(L)] 2+ (L = py, 3Me-py, 4Me-py) is octahedral in DMF. The MnO and MnN bond lengths are 222(1) pm for [Mn(py)(dmf) 5 ] 2+ , 223(1) pm for [Mn(3Me-py)(dmf) 5 ] 2+ and 222(1) pm for [Mn(4Me-py)(dmf) 5 ] 2+ , and are virtually the same as the MnO one within [Mn(dmf) 6 ] 2+ . However, the non-bonding Mn … C (DMF) distances within [Mn(L)(dmf) 5 ] 2+ are longer (321–322 pm) and the corresponding MnOC bond angles (134–135°) are wider than those within [Mn(dmf) 6 ] 2+ . Thus, in DMF the steric interaction between DMF molecules and pyridines in the first coordination sphere of the manganese(II) ion is quite large.

Reactions of a tetravanadate anion, [V4O12]4–, with a series of lanthanide(III) salts yield three types of lanthanide complexes of macrocyclic polyoxovanadates: (Et4N)6[LnIIIV9O27] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6)], (Et4N)5[(H2O)HoIII(V4O12)2] (7), and (Et4N)7[LnIIIV10O30] [Ln = Er (8), Tm (9), Yb (10), Lu (11)]. Lanthanide complexes 1–11 are isolated and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and extended X-ray absorption fine structure spectroscopy (EXAFS). Lanthanide complexes 1–6 are composed of a square-antiprism eight-coordinated LnIII center with a macrocyclic polyoxovanadate that is constructed from nine VO4 tetrahedra through vertex sharing. The structure of 7 is composed of a seven-coordinated HoIII center, which exhibits a capped trigonal-prism coordination environment by the sandwiching of two cyclic tetravanadates with a capping H2O ligand. Lanthanide complexes 8–11 have a six-coordinated LnIII center with a 10-membered vanadate ligand. ...

Many empirical parameters have been suggested to measure solvent effects in chemical reactions. Gutmann's donor number has been a successful parameter to quantify the electron-donating property of the solvent molecule; it is defined as the enthalpy change of the addition reaction of solvent molecule to SbCl(5) in 1,2-dichloroethane. Calorimetric measurements can be applied to determine the quantity. Because the existence of water is critical for reactions in organic solvents, we have analyzed the enthalpy change using the titration calorimetry while considering the complexation with water. The determined donor numbers of formamide, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and 1,1,3,3-tetramethylurea (TMU) are 22.4, 26.5, 30.0, and 40.4, respectively. The values of DMF and DMSO are in perfect agreement with those of Gutmann. A reliable value for TMU is obtained for the first time on the basis of the enthalpy change for the addition reaction.

The metal-substitution reaction of the homodinuclear mercury(II) porphyrin complex, [Hg2(tpps)]2− (H2tpps4− = tetrakis(4-sulfonatophenyl)porphyrin), with copper(II) has been studied by the EXAFS (extended X-ray absorption fine structure) method in an acetate buffer (pH 5.6). The tetrahedral mercury(II) acetato complex (rHg–O = 219 pm, rHg–O = 262 pm) reacts with the porphyrin to form the homodinuclear mercury(II) porphyrin, [Hg2(tpps)(CH3COO)2]4− (rHg–N = 222 pm, rHg–O = 265 pm), with a deformed structure, where two mercury(II) bind to two pyrrole nitrogens from upper and lower sides and pyrrole nitrogens are ruffled. The mercury(II) porphyrin was replaced with the distorted octahedral copper(II) acetato complex (rCu–O = 197 pm, rCu–O = 225 pm) to form the square planar copper(II) porphyrin, [Cu(tpps)]4− (rCu–N = 200 pm). The reaction mechanism of the large catalytic effect of mercury(II) on the copper(II) porphyrin formation is discussed from the structure of Hg2(tpps)2−, and the structure of the heterod...

The structures of solvated complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and In(III) ions in 1,1,3,3-tetramethylurea (TMU) have been determined by means of EXAFS (extended X-ray absorption fine structure) and electronic spectroscopy. The solvation structures in TMU are square pyramidal for the Mn(II) and Ni(II) ions, distorted tetrahedral for the Co(II) and Cu(II) ions, tetrahedral for the Zn(II) ion, and octahedral for the Cd(II) and In(III) ions, while in water all these metal ions are six-coordinated octahedrons. The solvation structure of Fe(II) ion is square pyramidal or trigonal bipyramidal. In the bulky TMU solvent, the coordination number should be reduced for relaxation of the sterically repulsive interaction around the solvated metal ions

The solvation structure of the iron(III) ion in N,N,-dimethylacetamide (DMA) has been determined by means of EXAFS (extended X-ray absorption fine structure) spectroscopy and the complex formation between iron(III) and thiocyanate ions has been calorimetrically and spectrophotometrically studied in DMA containing (C2H5)4NClO4 (0.4 mol dm−3) as a constant ionic medium at 25°C. The iron(III) ion is surrounded with six DMA molecules and has an octahedral [Fe(dma)6]3+ structure. Calorimetric and spectrophotometric titration data were well explained in terms of the formation of [Fe(SCN)n]3−n) (n = 1−6) and their formation constants, reaction enthalpies and entropies were determined. Electronic spectra of individual iron(III) thiocyanato complexes in DMA were also extracted. The complexation of iron(III) with thiocyanate ions in DMA is more favorable than that in N,N-dimethylformamide (DMF). The favorable formation is mainly due to the more negative reaction enthalpies in DMA than those in DMF, which is resulting from the larger steric interaction between the ligating DMA molecules around the iron(III) ion than the DMF ones.

The structures of copper(II) complexes with ethylenediamine (en) in aqueous and neat ethylenediamine solutions have been determined by the EXAFS (extended X-ray absorption fine structure) method. The copper(II) ion in en has an axially elongated octahedral structure with three en molecules. The Cu-N bond lengths in the four equatorial and two axial positions are 204(1) and 239(2) pm, respectively. The dynamic exchange reaction between en molecules in the bulk and en molecules bound to the copper(II) ion has been studied by the nitrogen-14 NMR line-broadening method

Complexation of iron(III) with thiocyanate ions has been calorimetrically and spectrophotometrically investigated in N,N-dimethylformamide (DMF) containing 0.4 mol/dm(3) (C(2)H(5))(4)NClO(4) or 1 mol/dm(3) NH(4)ClO(4) as a constant ionic medium at 25 degrees C. Calorimetric titration data were well explained in terms of the formation of [Fe(SCN)(n)]((3-n)+) (n = 1-5), and their formation constants, reaction enthalpies and entropies were determined. Electronic spectra of individual iron(III) thiocyanato complexes were also determined. The stepwise thermodynamic quantities changed monotonously, i.e. DeltaG degrees (1)DeltaG degrees (2)DeltaG degrees (3)DeltaG degrees (4),DeltaG degrees (5), DeltaH degrees (1)DeltaH degrees (2)DeltaH degrees (3)DeltaH degrees (4)DeltaH degrees (5), DeltaS degrees (1)DeltaS degrees (2)DeltaS degrees (3)DeltaS degrees (4)DeltaS degrees (5). This suggests that no extensive desolvation occurred at any step of complexation. On the basis of these thermodynamic quantities, it is postulated that the [Fe(SCN)(n)]((3-n)+) (n = 1-5) complexes have a six-coordinate octahedral structure as well as the [Fe(dmf)(6)](3+) ion, the octahedral structure of which has been confirmed by the EXAFS (extended X-ray absorption fine structure) method.

The structure of the tetrathiocyanatocadmate(II) complex in dimethyl sulfoxide (DMSO) has been studied by the EXAFS (extended X-ray absorption fine structure) and solution X-ray diffraction methods. It has been revealed that the tetrathiocyanatocadmate(II) complex has a five-coordinate structure with an additional DMSO molecule. The structure in DMSO is different from that in water and N,N-dimethylformamide, in which no solvent molecule coordinates to the central metal ion. It has also been seen that the coordination mode of the thiocyanate ions in the tetrathiocyanatocadmate(II) complex changes depending on the source of thiocyanate ions due, probably, to different hydrogen bonding abilities of the N- and S-sites of the thiocyanate ion with the counter cations, i.e., the [Cd(NCS)3(SCN)(dmso)]2− and [Cd(NCS)4(dmso)]2− complexes are formed in solutions containing NH4SCN and (C2H5)4NSCN, respectively. The Cd–N, Cd–S, and Cd–O bond lengths within [Cd(NCS)3(SCN)(dmso)]2− are, respectively, 222(1), 262(1), and...

Spectrophotometric and calorimetric studies of the complexation of iron(III) with thiocyanate ions have been performed in an aqueous solution containing 1mol dm-3 NaClO4 or NH4ClO4 as a constant ionic medium at 25°C. Spectrophotometric titration data were well explained in terms of the formation of [Fe(SCN)]2+, [Fe(SCN)2]+ and [Fe(SCN)3], and their formation constants and individual electronic spectra were determined. The [Fe(SCN)]2+, [Fe(SCN)2]+ and [Fe(SCN)3] complexes exhibit absorption maxima at 450-500nm. Enthalpies and entropies for the formation of the [Fe(SCN)]2+, [Fe(SCN)2]+ and [Fe(SCN)3] complexes were also determined from calorimetric titration data. On the basis of these thermodynamic quantities, it is postulated that the [Fe(SCN)]2+, [Fe(SCN)2]+ and [Fe(SCN)3] complexes have a six-coordinate octahedral structure.

Formation of the 2 : 1 mercury(II) porphyrin complex, Hg2(tpps)2− (H2tpps4−: tetrakis(4-sulfonatophenyl)porphyrin), in aqueous solution has been investigated. Equilibrium studies revealed that main chemical species is Hg2(tpps)2− even in a solution of a 1 : 1 molar ratio of Ctpps/CHg and the Hg2(tpps)2− complex is very stable thermodynamically. EXAFS (extended X-ray absorption fine structure) analysis of the Hg2(tpps)2− complex in aqueous solution showed that the Hg–N bond length within the complex is 215(2) pm and the bond length is much shorter than the Hg–O bond length (240 pm) within the hydrated mercury(II) ion. Thus the very strong Hg–N bond is formed upon the complexation of Hg2(tpps)2− and the strong bond formation supports the high stability of the Hg2(tpps)2− complex. Deformation of Hg2(tpps)2− is also discussed in connection with catalytic effect of mercury(II) on metalloporphyrin formation.

The structure of pyridine (py) complexes with copper(II) and copper(I) ions in aqueous solution has been studied by the EXAFS (extended X-ray absorption fine structure) method. The results of the EXAFS analyses of copper(II) solutions containing the [Cu(py)]2+, [Cu(py)2]2+, [Cu(py)3]2+ and [Cu(py)4]2+ complexes as the main species, respectively, revealed that all copper(II) pyridine complexes have an axially-elongated octahedral structure with additional water molecules. The equatorial Cu—O and Cu—N bond distances within the complexes are found to be slightly lengthened on increasing the number of pyridine molecules bound to the copper(II) ion and the axial Cu—O bond length is lengthened in [Cu(py)4]2+. It was also shown that the tris(pyridine)copper(I) complex is formed in a copper(I) solution containing a large excess of pyridine. No water molecules coordinate to the copper(I) ion and thus the complex has a three-coordinate triangular structure.

The coordination structure of the cobalt(II) ion and its chloro complexes of low concentration (∼20 mmol dm −3 ) in hexamethylphosphoric triamide (HMPA) has been explored by laboratory EXAFS (extended X-ray absorption fine structure) modified for fluorescence detection. The cobalt(II) ion is four-coordinated in HMPA, unlike other oxygen-donor solvents such as water and N,N -dimethylformamide (DMF). The CoO (HMPA) bond lengths within complexes are revealed to be 194(1), 195(1), 194(1) and 202(2) pm for [Co(hmpa) 4 ] 2+ , [CoCl(hmpa) 3 ] + , [CoCl 2 (hmpa) 2 ] and [CoCl 3 (hmpa)] − , respectively. The CoO bond length is significantly shorter than that within six-coordinate [Co(H 2 O) 6 ] 2+ (208 pm) or [Co(dmf) 6 ] 2+ (206 pm), and remains practically unchanged upon formation of mono- and dichloro complexes. On the other hand, the CoCl bond length is 224(1), 227(1) and 229(1) pm within [CoCl(hmpa) 3 ] + , [CoCl 2 (hmpa) 2 ] and [CoCl 3 (hmpa)] − , respectively, all of which are appreciably shorter than that within the six-coordinate [CoCl(H 2 O) 5 ] + (235 pm). The origin of the different thermodynamic behavior of chloro complexation of cobalt(II) in HMPA from that in DMF will be discussed on the basis of these structural data.

The structure of the mono- and bis(aminocarboxylato)copper(II) complexes in aqueous solution has been studied by the EXAFS (extended x-ray absorption fine structure) method. All the complexes examined in the present study have an axially elongated octahedral structure. The equatorial CuO and CuN bond lengths within mono- and bis(aminocarboxylato)copper(II) as well as hexaaquacopper(II) are practically the same within experimental uncertainties. The axial CuO distances within the complexes are also the same.

EXAFS (extended X-ray absorption fine structure) spectra were measured for N,N-dimethylformamide (DMF) solutions containing cobalt(II) ion and its chloro complexes of low concentration (20–40 mmol dm−3) by a laboratory EXAFS spectrometer modified for the fluorescence detection. The analysis of the EXAFS data for a cobalt(II) perchlorate DMF solution showed that cobalt(II) ion in DMF has an octahedral structure with six DMF molecules. The Co-O (DMF) bond length within [Co(dmf)6]2+ in DMF is 206(1) pm and is practically the same as that within [Co(H2O)6]2+ (208 pm) in water within experimental uncertainties. It was also shown that the tri- and tetrachlorocobaltate(II) complexes in DMF have a tetrahedral structure. The Co–O and Co–Cl lengths within [CoCl3(dmf)]− in DMF are 202(1) and 227(1) pm, respectively. The Co–Cl distances within [CoCl]2− in DMF and in water are the same and 229(1) pm.

The structure of copper(II) complexes with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) in aqueous solution has been studied by EXAFS and spectrophotometric methods. The EXAFS data and electronic spectra for solutions containing [Cu(bpy)]2+, [Cu(bpy)2]2+ and [Cu(bpy)3]2+ complexes as the main species, respectively, showed that the mono(2,2′-bipyridine)copper(II) complex has an axially elongated octahedral structure with four additional water molecules and the tris(2,2′-bipyridine)copper(II) complex also has a distorted octahedral structure. On the other hand, the bis(2,2′-bipyridine)copper(II) complex has a five-coordinate trigonal bipyramidal structure with an additional water molecule. It was also shown that the structure of the mono- and tris(1,10-phenanthroline)copper(II) complexes is axially elongated octahedral similar to the relevant 2,2′-bipyridine complexes. The structure of the bis(1,10-phenanthroline)copper(II) complex was not determinable by the present transmission mode EXAFS experiment because of its very low solubility in water.

The structure of iron(III) complexes with 1, 2-dihydroxybenzene-3, 5-disulfonate (tiron4-) ion in aqueous solution has been studied by means of extended X-ray absorption fine structure (EXAFS) spectroscopy. EXAFS analyses of solutions containing [Fe(tiron)]-, [Fe(tiron)2]5- and [Fe(tiron)3]9- complexes as the main species, respectively, revealed that the complexes have an octahedral structure. The Fe-O bond lengths within the [Fe(H2O)6]3+, [Fe(tiron)(H2O)4]-, [Fe(tiron)2(H2O)2]5- and [Fe(tiron)3]9- complexes are 202(1), 205(1), 202(1) and 204(1) pm, respectively, and are practically the same as that within the [Fe(H2O)6]3+ ion (200pm) determined by the X-ray diffraction method. The Fe-O distances are thus practically the same for all the complexes, within experimental uncertainties. The similar distances may reflect the pure electrostatic interaction between iron(III) ion and oxygen atom in ligands.

The formation of isothiocyanato complexes of manganese(II), cobalt(II), and nickel(II) has been studied by calorimetry and spectrophotometry in N,N-dimethylformamide (DMF). The formation of a series of mononuclear [M(NCS)] + , [M(NCS) 2 ], [M(NCS) 3 ] − , and [M(NCS) 4 ] 2− (M=Mn, Co, Ni) complexes is proposed for all the metal ions examined

The solvation structure of divalent transition-metal ions, manganese(II), iron(II), cobalt(II), nickel(II), copper(II), and zinc(II), in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) has been studied by the EXAFS (extended X-ray adsorption fine structure) method. All the metal ions examined show the coordination number n=6, suggesting a six-coordinate octahedral structure in DMF. The manganese(II), cobalt(II), nickel(II), and copper(II) ions also show n=6 in DMA as well as in DMF