Hydrothermal synthesis, structural characterisation and magnetic behaviour of hybrid complexes of N-(phosphonomethyl)iminodiacetate

Two new compounds containing multidentate chelating organic residues of N-(phophonomethyl)iminodiacetic acid (H₄pmida), [M(pyr)(H₂O)₄][M₂(Hpmida)₂(pyr)(H₂O)₂]·2(H₂O) (where pyr=pyrazine and M=Co²⁺ or Ni²⁺ for I and II, respectively) have been synthesised and structurally characterised by single-crystal and powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermal analysis and solid-state ³¹P MAS NMR. The compounds contain discrete binuclear anionic [M₂(Hpmida)₂(pyr)(H₂O)₂]²⁻ units in which one pyrazine ligand bridges two M²⁺ cations which are completely trapped inside three five-membered chelate rings formed by the Hpmida³⁻ ligands. These moieties close pack in the ac plane via a series of strong and highly directional O–HO hydrogen bonds leading to the formation of anionic layers. One-dimensional cationic coordination polymers are placed in-between and strongly hydrogen-bonded to these layers. The magnetic properties of these two materials are also reported.     

Second-sphere coordination in hexaamminecobalt(III) salt with organic sulphonate anion: Synthesis, characterisation and X-ray crystal structure of [Co(NH3)6](CH3SO3)3

Reaction of hexaamminecobalt(III) chloride with the silver salt of methanesulphonic acid in aqueous medium (1:3 molar ratio) forms hexaamminecobalt(III) methanesulphonate, [Co(NH₃)₆](CH₃SO₃)₃, in high yield. This cobalt(III) complex has been characterized by spectroscopic techniques (UV/visible, IR and NMR) and its solubility product determined. The X-ray crystal structure shows that the [Co(NH₃)₆]³⁺ cations interact at the second sphere by sharing edges with the anions, via N–H  O hydrogen bonds. The structure is related to that of [Co(NH₃)₆]Cl(CH₃SO₃)₂, but is modified to accommodate additional anions in place of Cl⁻.     

Structure characterization of several oxalate-bridged transition-metal coordination polymers

Four oxalate-bridged transition-metal supramolecular compounds [Co₂(im)₄(ox)₂] 1, [Co(im)₂(ox)] 2, [Mn(2,2′-bpy)(ox)] 3 and [Fe(H₂O)₂(ox)] 4 (im, imidazole; ox, oxalate; bpy, bipyridine) were obtained from the simple hydrothermal reactions of Mⁿ⁺oxL (M, transition metal; L, aromatic N-donor ligand) system. They all exhibit the 1-D chain structures, consisting of the (or ML²⁺) units linked by oxalate bridges. Interestingly, the 1-D oxalate chains in the title compounds are further self-assembled into the 3-D supramolecular networks through the interchain various secondary bonding interactions. Because the units adopt the different configuration, the oxalate chains show either zigzag type as in compounds 1–3 or linear type as in compound 4. Compounds 1 and 2 are isomeric, and only in packing modes of interchain im molecules there exists the difference.     

A new polar supramolecular 3D framework [Zn(pyz)(H2O)4]pht

A new Zn(II) complex, [Zn(pyz)(H₂O)₄]pht (1) (pyz=pyrazine; pht=1,2-benzenedicarboxylate) has been hydrothermally synthesized and characterized. Complex 1 features a novel polar 3D framework with a 1D polycationic chain , between which pht²⁻ dianions are encapsulated via the supramolecular interaction. Its powder SHG is of about three times as large as that of KH₂PO₄.     

Hydrothermal synthesis and crystal structural characterization of two new modified polyoxometalates constructed of positive and negative metal–oxo cluster ions

Two new interesting polyoxometalate derivatives 1 and 2 constructed of modified metal–oxo cluster ions carrying positive and negative changes, respectively, was hydrothermally prepared and structurally characterized by IR, ESR, XPS, elemental analysis and X-ray crystallography. The result of structure determination shows that compound 1 and 2 are isostructural and both contain polyoxocation and polyoxoanion, and both cation and anion are built on mixed Mo–V tetra-capped pseudo-Keggin units with P centre, [Mo₈V₈O₄₀(PO₄)]ⁿ⁻, bonded to four or two [Ni(2,2′-bipy)₂H₂O]²⁺ complexes, respectively, via terminal oxygen of the capping V atoms. Magnetism measurement indicates that there exists antiferromagnetic interaction in complex 1 and 2.     

Iron complexes of terdentate nitrogen ligands: formation and X-ray structure of three new dicationic complexes

Dicationic iron complexes were obtained upon complexation of the ligands 6,6″-di(p-tolyl)-2,2′:6′,2″-terpyridine (L¹) or 2,6-bis-(3-mesitylpyrazol-1-yl)pyridine (L²) with iron dichloride or iron trichloride. They were characterized by X-ray diffraction and FT-IR spectroscopy. Single crystal structure determinations of , and all show six-coordinate metal center. These complexes were obtained from L¹FeCl₂ and L²FeCl₂ during recrystallization attempts. (L¹)₂Fe²⁺ was shown to be a high-spin complex, whereas (L²)₂Fe²⁺ was shown to be low-spin. For , two independent dications of very similar geometry but with distinctive distortion were observed by X-ray analysis.     

Rare gas–iodine complexes in the ion-pair states

Luminescence and luminescence excitation spectra in the vicinity of the optical–optical double resonance transitions to the I₂(, v_f = 8 and 9, J_f ≈ 55) levels have been measured at the bulb conditions for the I₂ + Rg mixtures (Rg = He, Ar, Xe) at the rare gas pressures 2–20 Torr and room temperature. Luminescence attributed to the RgI₂ complexes in the ion-pair states has been observed for the first time. It is argued that the complexes can be formed by direct optical excitation from the complexes or colliding pairs. Besides, the RgI₂ complexes in the ion-pair states can be formed in nonadiabatic internal conversion processes from the one. The complexes have rather long lifetime, especially in the case of Xe, and decay radiatively and nonradiatively forming I₂ molecules in different ion-pair states.     

The limiting partial molar volume and apparent molar volume of glycylglycine in aqueous KCl solution at 298.15 and 308.15 K

Apparent molar volumes V_Φ of glycylglycine in aqueous KCl solutions have been obtained from densities at 298.15 and 308.15 K measured with a vibrating-tube densimeter. These data have been used to deduce partial molar volumes of transfer from water to different KCl–water mixtures. values are positive. This result arises from the interaction of KCl with the charged centers of glycylglycine. The results show that depends less on temperature. Hydration numbers are calculated from data and are interpreted in terms of various interactions.     

Ion pairing, H-bonding, and π–π interactions in copper(II) complex-organo-networks derived from a proton-transfer compound of the 1,10-phenanthroline-2,9-dicarboxylic acid

The one-pot reaction between the novel proton transfer compound (pydaH₂)²⁺(phendc)²⁻, LH₂, and Cu(II) afforded the compounds (pydaH)₂[Cu(phendc)₂]·10H₂O, 1, and (pydaH)₂[Cu(phendc)(phendcH)]₂·5H₂O, 2, where pyda=2,6-diaminopyridine, and phendcH₂=1,10-phenanthroline-2,9-dicarboxylic acid. The single crystal X-ray diffraction analysis of 1 and 2 revealed that these are two novel self-assembled 3D Cu(II) complex-organo-networks, in which (pydaH)⁺ ions and [Cu(phendc)₂]²⁻ or complex units are held together by ion pairing, H-bonding, and π–π interactions. Magnetic measurements over the temperature range 1.8–310 K revealed no significant magnetic coupling between Cu(II) centers in 1 or 2.     

UV photodissociation of N-methylpyrrole: The role of πσ states in non-hydride heteroaromatic systems

The photophysics of jet-cooled N-methylpyrrole molecules following excitation to their first excited singlet state (the ¹A₂ state, arising from a 3s/σ^*←π electron promotion) has been investigated by resonance enhanced multiphoton ionisation spectroscopy, by measurements of wavelength resolved ‘action’ spectra for forming CH₃ photoproducts, and by velocity map imaging studies of these CH₃ products (in their v = 0 and v₂ = 1 vibrational levels). CH₃ products are observed at all excitation wavelengths within the NMP absorption band. Direct dissociation on the ¹A₂ potential energy surface (PES) yields ‘fast’ CH₃ fragments, with an average total kinetic energy release (TKER) of 6500 cm⁻¹, but this product channel is only observed in a narrow wavelength range near the absorption band origin. All of the measured CH₃ images also show a broad component, peaking at lower TKER (1700 cm⁻¹); this component extends beneath the ‘fast’ feature in images recorded at wavelengths near the origin, and accounts for all of the CH₃ products observed at shorter photolysis wavelengths. These products are attributed to decay of highly vibrationally excited ground state molecules formed by radiationless transfer from the ¹A₂ state. Similarities and differences with the results of previous studies of the H + pyrrolyl products arising in the UV photodissociation of pyrrole are discussed in terms of the likely nuclear motions on the relevant ground and excited PESs (along R_N–CH3/R_N–H), and the possible couplings between these surfaces. The present study confirms that the proposed model of ¹πσ^* state induced bond fission in heteroaromatic molecules [A.L. Sobolewski, W. Domcke, Chem. Phys. 259 (2000) 181] is also applicable to non-hydride substituted heteroaromatics, but that mass effects can have an important influence on the subsequent nuclear dynamics.     

Synthesis and structures of three 1-aminoethylidenediphosphonate compounds with transition-metal ions

Three new aminodiphosphonates, namely M(phen)(AEDPH₃)₂·4H₂O (M = Zn, (1); Ni, (2)) and Cu(phen)(AEDPH₃)₂·H₂O (4), in addition to the previously reported Co(phen)(AEDPH₃)₂·4H₂O (3), Cu(2,2′-bipy)(H₂O)(HEDPH₂)·2H₂O (5), and Cu(phen)(H₂O)(HEDPH₂)·2H₂O (6) (AEDPH₄ = 1-aminoethylidenediphosphonic acid, HEDPH₄ = 1-hydroxyethylidenediphosphonic acid, phen = 1,10-phenanthroline and 2,2′-bipy = 2,2′-bipyridyl), have been synthesized and characterized. These compounds are all synthesized at the similar condition (80 °C), whereas they illustrate different frameworks. Compounds 1, 2 and 3 are isomorphous, which contain two same chelate and one six-coordinated metal ion, and display a three-dimensional (3D) supramolecular structure through hydrogen bonds and π–π stacking interactions. Compound 4 contains a chelate and a monodentate , while the Cu ion is five-coordinated. The coordination model of Cu²⁺ in 4 is similar to that of 5 and 6. Comparing with four aminoethylidenediphosphonates, the difference of their structures is directed to the coordination model of the metal ions, while the three copper(II) diphosphonates illustrate different structures based on the deprotonized degree of the corresponding diphosphonic acids.     

Pulse radiolysis of 9-anthrylmethylammonium cation in aqueous solution

The reaction of hydrated electron with 9-anthrylmethylammonium cation to form the respective anthracene radical anion in aqueous solution has been studied by the method of pulse radiolysis. The rate constant of the reaction of with is reported. It is demonstrated that the anthracene radical anion is unstable and undergoes further reactions. The spectra of transient intermediates, leading to the final reduction products, are presented.     

Crystal structure, phase transition and thermal behaviour of dabcodiium hexaaquacopper(II) bis(sulfate), (C6H14N2)[Cu(H2O)6](SO4)2

A new organically templated metal sulfate has been synthesized and characterized. At room temperature, dabcodiium hexaaquacopper(II) bis(sulfate), (C₆H₁₄N₂)[Cu(H₂O)₆](SO₄)₂ crystallizes in the monoclinic symmetry (space group P2₁/n) with the following unit cell parameters: a = 6.9533(2), b = 12.5568(2), c = 9.9434(2) Å; β = 90.526(1)° and Z = 2. Its crystal structure is built from isolated [Cu(H₂O)₆]²⁺, and disordered ions linked together by a hydrogen-bonding network. The title compound undergoes a reversible phase transition of the first-order type at 265.7/281.8 K on heating–cooling runs. Below the phase transition temperature, the structure is fully ordered.     

Excess molar enthalpies for binary mixtures of trimethyl phosphate with alkanols {CH3(CH2)nOH, n = 0–3} at 298.15 K

The excess molar enthalpies () for the binary mixtures of trimethyl phosphate (TMP) with alkanols {CH₃(CH₂)_nOH, n = 0–3} have been measured with an isothermal calorimeter at 298.15 K and atmospheric pressure. The values are positive for all the mixtures over the whole composition range. The values increase in the order methanol < ethanol < 1-propanol < 1-butanol. The experimental results have been correlated with the Redlich–Kister equation.     

Theoretical studies on the aromaticity of η-cyclopentadienyl cobalt dithiolene complexes

Some η⁵-cyclopentadienyl cobalt dithiolene complexes CpCoS₂C₂R₂ have been optimized at B3LYP/6-311++G(d) level. The optimized geometries agree well with experiment. The analyses of nature bond orbital and nucleus-independent chemical shift (NICS) at B3LYP/6-311++G(d) and GIAO-B3LYP/6-311++G(d) levels reveal the aromatic character of the η⁵-cyclopentadienyl cobalt dithiolene complexes. However, their aromaticity is weaker than that of the isolated . There are two reasons for the change of heterocyclic aromaticity of the metal dithiolene in the η⁵-cyclopentadienyl cobalt dithiolene complexes with respect to that of the isolated . The better equalization of bond lengths in the isolated cation is the first reason. The other reason is that the contribution to the NICS from the metallic cobalt atom is much larger in the isolated cation . The planar character of cyclopentadienyl is destroyed slightly in the complexes. At the same time, the size of cyclopentadienyl (Cp) becomes bigger than the isolated Cp⁻¹ and this is caused by the cobalt atom in the pentagon. The π-electron delocalization causes stronger aromaticity of the Cp in the complexes than that of the isolated Cp⁻¹.     

Infrared intensities of liquids XXV: Dielectric constants, molar polarizabilities and integrated intensities of liquid toluene at 25 °C between 4800 and 400 cm

The main purpose of this paper is to present accurate infrared integrated intensities of liquid toluene, C₆H₅CH₃, at 25 °C. Also presented are the decadic molar absorption coefficients, E_m, the real and imaginary dielectric constants, ε′ and ε″, and the real and imaginary molar polarizabilities, ^′_m and ^″_m. Integrated intensities were determined as C_j, the area under bands in the spectrum, for all bands between 4800 and 440 cm⁻¹. The contributions from the different bands were separated by fitting the spectrum with classical damped harmonic oscillator bands. The uncertainties in the integrated intensities of most bands are estimated to be 5–10%, with the uncertainties in very weak bands and in shoulders possibly up to 100%. The intensity that should be assigned to the fundamentals is more difficult to estimate due to Fermi resonance with overtone and combination bands, and a best estimate is given. The integrated intensities of the fundamental vibrations and the corresponding transition dipole moments are summarized and are compared with literature values for the gas.     

Production of HO2 and O2 by multiple ionization in water radiolysis by swift carbon ions

We present a simulation of liquid water radiolysis by swift carbon ions that explicitly takes into account multiple ionization of water molecules. For high linear energy transfer (LET), this process is not negligible with respect to single ionization. The rearrangement of highly ionized water molecules is consistent with production of atomic oxygen. Multiple ionizations is shown to be responsible for creation of a large amount of radicals and O₂ molecules. The simulated yield reproduces very well direct optical measurements for swift ions with comparable LET. Our simulation for is in also agreement with experiment.     

Synthesis and characterization of a novel two-dimensional layered vanadate complex containing double helical chains

A novel two-dimensional layered vanadate complex 1 [Ni(phen)H₂O][V₂O₆] has been hydrothermally synthesized and characterized by elemental analyses, i.r., x.p.s., t.g. and single crystal X-ray diffraction. The single crystal X-ray diffraction analysis reveals that compound 1 consists of the chains covalently linked by [Ni(phen)H₂O]²⁺ subunits to form two-dimensional layered polyoxovanadate. It is interesting that the compound 1 consists of left-handed and right-handed helical chains, which are further interconnected to produce the double helical chains. The adjacent two-dimensional layers interact with each other via extensive hydrogen bonds and π–π stacking interactions to form a three-dimensional supramolecular framework.     

A simple method for predicting the frequency of the infrared inactive carbonyl stretching mode in LM(CO)5 molecules with C4V symmetry

The paper presents a new method for predicting the frequency of the b₁ mode, which is infrared-inactive, in complexes of the type LM(CO)₅ belonging to C_4V point group. The method was based on the relation λ₃=λ₄+[(1−δ/δ)](λ₁−λ₂), where δ=(λ₁−λ₂)/(λ₁−λ₂+λ₃−λ₄), λ₁, λ₂, λ₃ and λ₄ are the λ parameters of the , , b₁ and e modes, respectively. For a large numbers of complexes of the type LM(CO)₅ the average value of δ was found to be 0.80, with a standard deviation of 0.02. With the use of average value of δ, the frequencies of b₁ mode were estimated. The result obtained indicated that there exists a rather good fit between observed and calculated frequencies, with a mean error of 2.7 cm⁻¹. In addition, it was shown that the δ parameter can be used as a criterion of the correct band assignment for the complexes understudy.     

Gas-phase reactivities of charged platinum dimers with ammonia: A combined experimental/theoretical study

Computational and experimental studies of with ammonia are reported. While ammonia is dehydrogenated with either cluster type, the reaction efficiencies are quite different with  = 0.27 for [K. Koszinowski, D. Schröder, H. Schwarz, J. Phys. Chem. A 107 (2003) 4999.] and  = 0.0033 for . DFT-based relativistic calculations are consistent with this distinct behavior, with maximum energies along the reaction path of −13.3 kcal/mol for the cationic and +1.4 kcal/mol for the anionic clusters relative to the reactants. The recently proposed mechanism for the system [D. Xu. X.-Y. Chen, S.-G. Wang, Int, J. Quant. Chem. 107 (2007) 1985.] needs to be modified to account for the experimental findings.