Struktur-Reaktivitäts-Beziehungen bei koordinativ-ungesättigten Chelatkomplexen. VI. Synthese,Adduktbildung, Redoxpotentiale und photochrome lodderivate von Eisen(II)-Komplexen Schiffscher Basen mit elektronenziehenden Substituenten

Structure Reactivity Correlations in Coordinatively Unsaturated Chelate Complexes. VI. Synthesis, Adduct Formation, Redox Potentials, and Photochromic Iodine Derivatives of Iron(II) Complexes with Schiff Base Ligands Possessing Electron-Withdrawing Substituents Iron(II) complexes of the type 1 have been prepared by different synthetic methods. In contrast to similar chelates of the “saloph” and “salen” types, the high-spin complexes 1 form stable high-spin diadducts ( 1a – 1d ) and an unusual triadduct ( 1e ) with pyridine. The oxidation potentials of the Fe^II/Fe^III couple as measured by cyclic voltammetry are dependent on the solvent as well as the equatorial ligand substituents. The potentials are more positive in pyridine than in DMF, indicating a stabilization of Fe^II by pyridine. The redox potentials are discussed with respect to those of other metals in the same ligand environment. The complexes form iodine derivatives which show photochromic behaviour in THF solution. The rate of the reaction with dioxygen in the solid state as well as in pyridine solution decreases in the order 1f > 1a ≈ 1b > 1c ≈ 1d > 1e and correlates with the increasing oxidation potentials.     

Struktur-Reaktivitäts-Beziehungen bei koordinativ ungesättigten Chelatkomplexen. VII Zum Einfluß axialer Basen auf den Spin-Grundzustand und die Charge-Transfer-Spektren von Eisenkomplexen eines farblosen,porphyrin-verwandten [N4]-Makrocyclus

Structure Reactivity Correlations in Coordinatively Unsaturated Metal Chelate Complexes. VII. Effect of Axial Bases on the Spin Ground State and the Charge Transfer Spectra of Iron Complexes with a Colorless Porphyrine-like [N₄]-Macrocycle In contrast to similar macrocycles without the carbonyl substituents R², the iron(II) complexes 3 react with several bases to form stable adducts. With imidazole, dark red diamagnetic (S = 0) sesqui- and diadducts have been isolated. They are oxidized quickly by air to give dark green polymeric low-spin (S = 1/2) iron(III) derivatives with one imidazolate anion as a bridging axial ligand. With pyridine, ammonia, methanol etc. intense red monoadducts are formed which are intermediate-spin (S = 1) complexes. Preparation of 3a in the presence of water results in a very instable yellow product which appears to be a high-spin (S = 2) diadduct. All the iron(II) complexes are extremely sensitive to air. The spectra of the iron(III) derivatives exhibit a single CT band in the visible region. The energy of the sharp maximum is strongly influenced by axial ligands and can be used to characterize the coordination properties of several bases.     

ESR-Untersuchungen zu Struktur- und Bindungsverhältnissen von tri- und bicyclischen Cobalt(II)- und Kupfer(II)-Chelaten mehrzähniger Schiffscher Basen des Typs M(O N N O) und M(S N)2 sowie zur Sauerstoffadduktbildung der Cobalt(II) Chelate

Structural and Bonding Properties of Quadridentate and Bidentate Cobalt(II) and Copper(II) Schiff Base Complexes and Oxygenation Behavior of the Co^II Complexes. An ESR Study ESR investigations on the low-spin cobalt(II) chelates bis(benzoylacetaldehyde)-ethylendiimine-cobalt(II), bis(benzoylacetaldehyde)-1,2-cyclohexandiimine-cobalt(II) and bis(p-chlor-β-mercaptozimtaldanilato)-cobalt(II) as well as the corresponding copper(II) chelates are reported. The large anisotropy of the g tensor of the Co^II chelates caused by strong spin-orbit interactions, and the position of the maximum g tensor component g_x in the molecules obtained by comparison with the ESR spectra of the Cu^II complexes predicts a MO for the unpaired electron which consists mainly of the Co d_yz obital. In solution (CHCl₃/pyridine) the Co^II chelates react immediately with molecular oxygen forming [CoL_n(O₂)(py)] species characterized by ESR spectra with strongly reduced g tensor anisotropy and small ⁵⁹Co hyperfine coupling constants. The unpaired electron appears to be mainly localized in the O₂-part of hte molecules. The CoN₂S₂ coordination sphere shows a lower affinity to oxygen than the CoN₂O₂ type complexes. In the CuN₂O₂ complexes the unpaired electron is found to be in a MO containing the Cu d_xy orbital. Due to remarkable covalency¹⁴ N and H hyperfine interactions are observed in the ESR spectra. Analyzing the hyperfine coupling constants the extent of unpaired spin density on the N donor atoms and the N-2s/2p hybridization degree is estimated.     

Properties of [Fe(Salten)Cl] Being a Precursor for Spin-Crossover Compounds in Polycrystals and Vitrified Acetonitrile Solutions

The complexes of precursor with pentadentate Salten ligand has been shown to have high-spin state (S = 5/2) in a single crystal and polycrystalline phase and contain both high-spin and low-spin (S = 1/2) fractions in vitrified acetonitrile solutions. A correlation between ESR spectrum shape and crystallinity degree has been tracked for polycrystalline phase. The majority of complexes in crystals has been found to form exchange-coupled clusters. The ESR spectra of vitrified solutions have shown several types of high-spin centers and two kinds of low-spin complexes with different g-factors. On the basis of quantum chemical calculations, conclusion was drawn for the most likely structural form of the precursor in single crystal and polycrystalline samples and possible supramolecular associates in frozen solutions.     

Structural and Magnetic Chemistry of NdBaCo2O5+δ

The crystallographic and magnetic structures of the oxygen-deficient perovskites NdBaCo₂O_5+δ (δ=0, 0.38, 0.5, 0.69) have been studied as a function of temperature by neutron powder diffraction. Long-range G-type antiferromagnetic order is realized for all samples apart from that with δ=0.5. The lack of magnetic order for δ=0.5 can be understood on the basis of a crystal-field-induced spin-state ordering between low-spin and high-spin Co³⁺. Contrary to studies of similar materials with smaller lanthanides, the δ=0 material exhibits no evidence of long-range charge ordering. No evidence of a spin-state transition as observed in YBaCo₂O₅ is found for any of our samples.     

A correlation between spin state and electrochemical electron-transfer rate for tris(N,N-disubtituted dithiocarbamato) iron(III) complexes

The electrochemical electron-transfer rate constants for the redox systems Fe(IV)L₃⁺/Fe(III)L₃ (L=N,N-disubstituted dithicarbamate ion) and Fe(III)L₃/Fe(II)L₃^? with a variety of substituents were measured at a platinum electrode in acetonitrile with the galvanostatic double-pulse method. It is known that each of the Fe(III) complexes exists both in a highspin state ⁶A₁ and a low-spin state ²T₂ in equilibirium of which position is widely changed by a subtle change in substituent. The standard rate constants for Fe(IV)L₃⁺/Fe(III)L₃ were larger or smaller than those for Fe(III)L₃/Fe(II)L₃^? according as the Fe(III)L₃ complexes are predominantly low- or high-spin complexes. Since the Fe(IV) and Fe(II) complexes are low-and high-spin complexes respectively, these findings suggest that electrochemical electron-transfer reactions accompanied by a spin-state change are slower than those without it. Such spin-state effect on electrode reactions has rarely been discussed so far.     

Optimization of crystal packing in semiconducting spin-crossover materials with fractionally charged TCNQδ− anions (0 < δ < 1)

Co-crystallization of the prominent Fe(ii) spin-crossover (SCO) cation, [Fe(3-bpp)₂]²⁺ (3-bpp = 2,6-bis(pyrazol-3-yl)pyridine), with a fractionally charged TCNQ^δ− radical anion has afforded a hybrid complex [Fe(3-bpp)₂](TCNQ)₃·5MeCN (1·5MeCN, where δ = −0.67). The partially desolvated material shows semiconducting behavior, with the room temperature conductivity σ_RT = 3.1 × 10⁻³ S cm⁻¹, and weak modulation of conducting properties in the region of the spin transition. The complete desolvation, however, results in the loss of hysteretic behavior and a very gradual SCO that spans the temperature range of 200 K. A related complex with integer-charged TCNQ⁻ anions, [Fe(3-bpp)₂](TCNQ)₂·3MeCN (2·3MeCN), readily loses the interstitial solvent to afford desolvated complex 2 that undergoes an abrupt and hysteretic spin transition centered at 106 K, with an 11 K thermal hysteresis. Complex 2 also exhibits a temperature-induced excited spin-state trapping (TIESST) effect, upon which a metastable high-spin state is trapped by flash-cooling from room temperature to 10 K. Heating above 85 K restores the ground-state low-spin configuration. An approach to improve the structural stability of such complexes is demonstrated by using a related ligand 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) to obtain [Fe(bzimpy)₂](TCNQ)₆·2Me₂CO (4) and [Fe(bzimpy)₂](TCNQ)₅·5MeCN (5), both of which exist as LS complexes up to 400 K and exhibit semiconducting behavior, with σ_RT = 9.1 × 10⁻² S cm⁻¹ and 1.8 × 10⁻³ S cm⁻¹, respectively.

Co-crystallization of the cationic complex [Fe(3-bpp)2]²⁺ with fractionally charged TCNQ^δ− anions (0 < δ < 1) affords semiconducting spin-crossover (SCO) materials. The abruptness of SCO is strongly dependent on the interstitial solvent content.     

Komplexbildung der späten 3d-Elemente mit Arensulfonyl-thioharnstoffen,Arensulfonylmonothio- und Arensulfonyl-dithiocarbamidsäureestern

Complex Formation of the Late 3d-Elements with Arenesulfonylthioureas, Arenesulfonyl-monothio-, and Arenesulfonyldithiocarbamic Acid Esters Arenesulfonylthioureas (SPT-H, SAT-H, SMT-H), arenesulfonylmonothio-, and arenesulfonyldithiocarbamic acid esters (STCO-H, STCS-H) form neutral 1,2-chelates with copper(II), nickel(II), and cobalt(II), but not with iron(II) and manganese(II). Basing on the ESCA data, ESR and VIS spectra differences of the structure are proved: Four-membered rings (coordination of the sulfonamide function by nitrogen) are present in the copper(II) chelates, but six-membered ones (coordination of the sulfonamide function by one oxygen atom of the sulfonyl group) in the nickel(II) chelates. In the case of the complexes Co(SPT)₂, Co(SAT)₂, and Co(SMT)₂ both types of structure are realized by the formation of a high-spin and a low-spin isomer. The bonding behaviour of the ligands in the new complexes is discussed and in this connection both the IR spectra of SAT-H and its complexes and the selectivity of the copper(II) extraction from acidic solutions by the ligands STCO-H and STCS-H are explained.     

Stabilization of unusual electronic configurations of transition elements in elongated six-coordinated oxygen sites of a K2NiF4 structure

The A′_xA_2?xLi_0.5M_0.5O₄ matrix deriving from the K₂NiF₄ structure has an elongated MO₆ octahedron; it has been used to stabilize anisotropic electronic configurations such as high-spin Fe⁴⁺, low-spin Co⁴⁺, medium-spin Co³⁺, low-spin Ni³⁺, or low-spin Cu³⁺. The choice of ions to be stabilized was based on a simple model for predicting the electronic configuration of a dⁿ ion in a tetragonally distorted octahedral environment.     

Metal Complexes with Macrocyclic Ligands. PartXLV Axial coordination tendency in reinforced tetraazamacrocyclic complexes

The Cu²⁺ and Ni²⁺ complexes of three reinforced tetraazamacrocycles, containing a piperazine subunit and one or two alkyl substituents at the other two N-atoms have been prepared and their structural properties studied. In solution, the Ni²⁺ complexes are square-planar and show no tendency to axially coordinate a solvent molecule or an N ion. In contrast, the Cu²⁺ complexes change their geometry depending upon the donor properties of the solvent, being square-planar in MeNO₂ and pentacoordinate in DMF. They also easily react in aqueous solution with N to give ternary species with pentacoordinate geometry, the stabilities of which have been determined. In the solid state, the X-ray crystal structures of three Cu²⁺ complexes also show both geometrical arrangements, two having a square-planar, the other one a distorted square pyramidal geometry. The difference behavior of Ni²⁺ and Cu²⁺ stems from the fact that the structural change from square-planar to square-pyramidal can easily be accomplished for Cu²⁺, whereas, for Ni²⁺, it is accompanied by an electronic rearrangement from the low-spin to the high-spin configuration. The relatively rigid ligands cannot Adapt to the somewhat larger high-spin Ni²⁺ion.     

Ligand Exchange in Pd(II)-NaCl-H<Subscript>2</Subscript>O and Pd(II)-HCl-H<Subscript>2</Subscript>O Systems: Quantum-Chemical Consideration

The behavior of potassium tetrachloropalladate(II) in media simulating biological liquids is studied. The rate of aquation in aqueous NaCl solutions is shown to be higher than the rate at which the Cl^? ligand enters the inner coordination sphere of the Pd atom. In HCl solutions, the formation of the Pd chloro complexes predominates due to protonation of water molecules in the composition of aqua complexes. The reactions of replacement of the ligands (H₂O molecules and H₃O⁺ ion) in the planar Pd(II) complexes by the chloride ion are studied by the ZINDO/1 method. All the complexes containing H₂O and H₃O⁺ ligands, except for [Pd(H₂O)₄]²⁺, contain intramolecular hydrogen bonds. The ZINDO/1 and RHF/STO-6G(d) calculations revealed “nonclassic” symmetrical O? H?O hydrogen bond in the [[Pd(H₂O)₃(H₃O)]³⁺ and trans-[Pd(H₂O)₂(H₃O)Cl]²⁺ complexes. The replacement of the H₃O⁺ ion by the Cl^? ion at the first three steps is thermodynamically more advantageous than the displacement of water molecules from the metal coordination sphere. The logarithms of stepwise stability constants of Pd(II) chloro complexes are found to correlate linearly with the enthalpies (ZINDO/1, PM3) of reactions of H₂O replacement by Cl^?.     

Synthesis,characterization and magnetic properties of mixed-valence iron complexes with 2-pyridyl oximes

Abstract

Two new mixed-valence iron complexes with 2-pyridyl oximes, [Fe(mpko)₃Fe(H₂O)₂(NO₃)](NO₃)·2H₂O (1) (mpko^? = methyl(2-pyridyl)ketone oximate) and [{Fe(dpko)₃}₂Fe](ClO₄)·4H₂O (2) (dpko^? = bis(2-pyridyl)ketone oximate), have been prepared by reaction of Fe^III with mpkoH in methanol (1) and Fe^II with dpkoH in methanol/water (2). Dinuclear Fe^II(low-spin)Fe^III(high-spin) and trinuclear Fe^II(low-spin)Fe^III(high-spin)Fe^II(low-spin) cations are present in the crystal structure of 1 and 2, respectively. Intermolecular hydrogen bonds in 1 lead to weak antiferromagnetic interactions between pairs of neighboring Fe^III centers, which allows observation of single-ion zero-field splitting effects.     

Infrared Spectroscopic Studies on the Surface Chemistry of High‐Surface‐Area Gallia Polymorphs

Polymorphs α, β, and γ of Ga₂O₃ having hexagonal (corundum‐type), monoclinic and cubic (spinel‐type) structure, respectively, were prepared in a high‐surface‐area form, and characterized by powder X‐ray diffraction. Nitrogen adsorption at 77 K showed these gallia samples to have specific surface areas of 77 (α‐Ga₂O₃), 40 (β‐Ga₂O₃) and 120 m² g^?1 (γ‐Ga₂O₃). Fourier transform infrared spectroscopy of adsorbed carbon monoxide (at 77 K) and pyridine (at room temperature) showed that the three gallia polymorphs have a very similar surface Lewis acidity, regardless of their different crystal structures. This Lewis acidity was assigned, mainly, to coordinatively unsaturated tetrahedral Ga³⁺ ions situated on the surface of the small crystallites which constitute the different metal oxide varieties. Ga³⁺···CO adducts formed after CO adsorption gave (in all cases) a characteristic C–O stretching band at 2195–2200 cm^?1, while Lewis‐type adducts formed with adsorbed pyridine were characterized by IR absorption bands at 1610–1612 and 1446–1450 cm^?1. The three (partially hydroxylated) gallia polymorphs showed also a very weak Brønsted acidity, which they manifested by forming hydrogen‐bonded adducts with both CO and pyridine; however no protonation of adsorbed pyridine occurred.     

Ti0.99Pd0.01O2−δ: A New Pt‐free Catalyst for High Rates of H2+O2 Recombination with High CO Tolerant Capacity

A platinum‐free H ₂ /O ₂ recombination catalyst , Ti_0.99Pd_0.01O_2?δ, is synthesized by a solution combustion method where Pd²⁺ ions adsorb protonic H₂^δ+ ion and oxygen on the oxide ion vacancy sites (see picture). The rate of H₂+O₂ recombination at 50 °C is 15 μmoles g^?1 s^?1, which is much higher than that of Pt‐containing catalysts.

     

Reactivity in the gas phase. Behaviour of isoxazoles under negative ion chemical ionization conditions

[M ? H⁺]^? ions of isoxazole (la), 3-methylisoxazole (1b), 5-methylisoxazole (1c), 5-phenylisoxazole (1d) and benzoylacetonitrile (2a) are generated using NICI/OH^? or NICI/NH₂^? techniques. Their fragmentation pathways are rationalized on the basis of collision-induced dissociation and mass-analysed ion kinetic energy spectra and by deuterium labelling studies. 5-Substituted isoxazoles 1c and 1d, after selective deprotonation at position 3, mainly undergo N ? O bond cleavage to the stable α-cyanoenolate NC ? CH ? CR ? O^? (R = Me, Ph) that fragments by loss of R? CN, or R? H, or H₂O. The same α-cyanoenolate anion (R = Ph) is obtained from 2a with OH^?, or NH₂^?, confirming the structure assigned to the [M ? H⁺]^? ion of 1d, On the contrary, 1b is deprotonated mainly at position 5 leading, via N? O and C(3)? C(4) bond cleavages, to H? C ≡ C? O ^? and CH₃CN. Isoxazole (1a) undergoes deprotonation at either position and subsequent fragmentations. Deuterium labelling revealed an extensive exchange between the hydrogen atoms in the ortho position of the phenyl group and the deuterium atom in the α-cyanenolate NC ? CD = CPh ? O^?.     

Lanthanoid‐Peroxo‐Komplexe mit μ3‐η2:η2:η2‐(O22—)‐Koordination. Die Kristallstrukturen von [Ln4(O2)2Cl8(Py)10] · Py mit Ln = Sm,Eu, Gd

Lanthanoid Peroxo Complexes with μ₃‐η²:η²:η²‐(O₂^2—) Coordination. Crystal Structures of [Ln₄(O₂)₂Cl₈(Py)₁₀] · Py mit Ln = Sm, Eu, Gd The four‐nuclear peroxo complexes [Ln₄(O₂)₂Cl₈(Py)₁₀]·py (py = pyridine) with Ln = Sm ( 1 ·py), Eu ( 2 ·py) und Gd ( 3 ·py) are formed as pale yellow ( 1 ·py) and colourless ( 2 ·py and 3 ·py) crystals by action of atmospheric oxygen on heated solutions of the anhydrous trichlorides LnCl₃ in pyridine/ diacetone alcohol (4‐hydroxy‐4‐methyl‐2‐pentanone). According to the X‐ray structural analyses the three complexes crystallize isostructural in the triclinic space group PP1¯ with two formula units per unit cell. 1—3 form centrosymmetrical molecular structures, in which the four lanthanoid atoms in coplanar array are linked via the two peroxo groups in a hitherto unobserved μ₃‐η²:η²:η² coordination. Additionally, they are bonded by four �μchloro bridges. Two of the Ln atoms complete their coordination sphere by three pyridine molecules each, the other two by two chlorine atoms and two pyridine molecules. The gadolinium compound is additionally characterized by its complete vibrational spectrum (i.r. and Raman).     

Metal String Complexes: Synthesis,Crystal Structures and Magnetic Properties of Heptanuclear Nickel(II) Complexes, [Ni7(μ7-teptra)4X2] (teptra = tetrapyridyltriamido,X = Cl−, NCS−)

The synthesis, crystal structures and magnetic properties of linear heptanuclear nickel(II) complexes [Ni₇(μ₇-teptra)₄X₂], (teptra = tetrapyridyltriamido), with the axial ligand X = Cl^? ( 1 ), NCS^? ( 2 ), are reported. The hepta-nuclear metal chain is helically wrapped by four syn-syn-syn-syn-syn-syn teptra^3? ligands. Both of the [Ni₇(μ₇-teptra)₄]²⁺ moiety are isostructural involving a Ni₇ linear chain unit with all of the ∠Ni-Ni-Ni being 180°, terminated by two axial ligands. Three types of Ni? Ni distances are found in these complexes. The longest ones bonded with the axial ligands are 2.383(1), 2.374(2) and 2.375(2), 2.354(2), and the intermediate ones are 2.310(1), 2.304(1) and 2.300(2), 2.303(2) Å for ( 1 ) and ( 2 ), respectively. The innermost Ni? Ni distances are the shortest ones with the distances of 2.226(2), 2.214(2) and 2.194(2), 2.206(2) Å for ( 1 ) and ( 2 ), respectively. Two terminal Ni(II) ions bonded with the axial ligands are in a square-pyramidal (NiN₄X) environment and exhibit long Ni? N bonds (?2.10 Å) which are consistent with a high-spin Ni(II) configuration. The inner five Ni(II) ions displayed short Ni? N (～1.90 Å) bond distances which are consistent with a square-planar (NiN₄), diamagnetic arrangement of a low-spin Ni(II) configuration. The magnetic measurement of ( 1 ) shows an antiferromagnetic interaction of two terminal high-spin Ni(II) ions with the coupling constant J = ?3.8 cm^?1. The Ni? Ni, Ni? N distances and magnetic behavior among tri-, penta-, and hepta-nickel(II) complexes are compared and discussed.     

ESR study of low-spin Co(II) complexes: observation of hyperfine interaction with in-plane ligand atoms

The ESR spectra of low-spin Co(II) complexes with phosphorus-containing ligands, show clearly resolved ³¹P hyperfine interaction with the in-plane ligand atoms (ca. 20 × 10^?4 cm^?1). A ²A₁ ground state is proposed on the basis of the properties of the ³¹P hfs tensor.     

A comparative study on the behaviour of 1,3-diheterocyclopentanes (X = O,O; S,S; O,S) under electron impact. The formation of thioacetyl and thiiranyl cations

The electron-impact-induced mass spectra of 1,3-dioxolane (la), 1,3-dithiolane (2a) and 1,3-oxatbiolane (3a) and their 2-methyl (1b–3b) and 2,2-dimethyl [(CH₃)₂: 1c–3c or (CD₃)₂: 1d–3d] derivatives have been studied in detail to gain further insight into their ion structures and competing reaction pathways with low-resolution, high-resolution, metastable and collision-induced dissociation (CID) techniques. For compounds 1a–1d the most significant reaction is loss of H^˙ and CH₃^˙ by α-cleavage and a subsequent formation of CHO⁺ and C₂H₃O⁺ ions. The [M ? H]⁺ ions from 1a and 1b give a C₂H₃O⁺ ion which does not have the acyl cation structure as shown by their CID spectra. In compounds 3a–3d the sulphur-containing ions predominate, the C₂H₃O⁺ now having the acyl cation structure. 1,3-Dithiolanes (2a–2d) exhibit the most complicated fragmentation patterns. Furthermore the [M ? H]⁺ ion from 2a and [M ? CH₃]⁺ ion from 2b have different structures as well as the [M ? H]⁺ ion from 2b and [M ? CH₃]⁺ ion from 2c, as shown by their CID spectra. This can be utilized to explain why 3a–3c and 2a give principally a thiiranyl cation, whereas 2b gives a mixture of this and the thioacyl cation and 2c practically only the open-chain thioacetyl cation.     

Effect of powder dispersion on the1 A 1 ⇄5 T 2 spin transition in Fe(II) complexes with 4-amino-l,2,4-triazole

A series of Fe(II) complexes with 4-amino-1,2,4-triazole ground in an agate mortar for 10 min is studied by Mössbauer spectroscopy. Strong effects of powder dispersion both on the¹ A ₁ ?⁵ T ₂ spin transition and on the structure dynamic characteristics of the complexes are found. Thus at 295 K the high-spin form of Fe(II) appears in the samples or its fraction increases; the ionicity of Fe-N bonds and the extent of distortion of the octahedral environment of iron atoms for the low-spin phases of the complexes also increase. It is established that powder dispersion markedly affects the probability of the Mössbauer effect and the vibrational spectrum of the lattice of coordination compounds. For both the low- and high-spin phases of the complexes, it is reported that the vibrational spectrum is “softened.” The main reason for these effects is supposed to be defectiveness rather than the size of the particles due to mechanical activation of the powder.