Exchange interactions in a trigonal chromium (III) dimer. Optical spectroscopy of tris-(μ-hydroxo)-bis-[(1,4,7-trimethyl-1, 4,7-triazacyclononane) chromium(III)] triperchlorate

High-resolution absorption, luminescence, Zeeman and MCD experiments were performed on single crystals of the title compound. The singlet-triplet and triplet-quintet exchange splittings in the ground state are 138 and 267 cm^?1, respectively. The corresponding exchange parameters are 2J= ?128 cm^?1 and j = 1.6 cm^?1. The zero-field splitting in the ground level is ?2.25 cm^?1. The lowest-energy emitting state is a ³E state, split into four spinor components with a total spread of 8 cm^?1.     

Magnetic chains formed from tetra-coordinate Co(II) complexes

Two tetra-coordinate Co(II) complexes, [CoCl₂(bzfupy)₂] and [CoCl₂(p-tol)₂] with N-donor ligands, are apparently mononuclear systems. The magnetic susceptibility at low temperature attains a maximum which is a fingerprint of the exchange interaction. The exchange coupling constant fitted to a model of 1D-magnetic chain yields J/hc = ?0.50 cm^?1 and ?0.57 cm^?1, respectively. The magnetic interaction is mediated by the π-π stacking in the first complex, and the short Cl…Cl contacts in the second.     

Vibrational energy exchange of the DF (ν=2) state with DF (ν=0)

The energy transfer rate for the reaction DF (ν=1) + DF (ν=1)^k_νν→ DF (ν=0) + DF (ν=2) + ΔE=91.6 cm^?1 has been studied in a combined shock-tube laser-induced fluorescence experiment at temperatures from 295 to 720°K. The rate coefficient k_νν for the exothermic reaction was found to vary as T^?1 when expressed in units of cm³/mole sec. At T=295°K, the probability of the reaction is approximately 0.2 per collision.     

The structure and magnetic properties of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2

A new μ₃-O triiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NO₃)(CH₃OH)₂ (HOBZ = benzoic acid) has been synthesized, its structure has been determined and variable temperature magnetic susceptility has also been measured. In the molecule, three iron atoms formed an equilateral triangle with μ₃-O in center. The fitting to the magnetic susceptibility showed that an intramolecular antiferromagnetic exchange interaction occurred between iron atoms with J=-25.51 cm^?1, and a weaker intermolecular autiferromagnetic exchange interaction occurred with zJ' = ?2.30 cm^?1.     

Vibrational relaxation of HF(υ = 3,4)

The vibrational relaxation of pure HF(υ = 3 and υ = 4) has been studied by pumping HF directly from υ = 0 to υ = 4. The relaxation rates of υ = 3 and υ = 4 were determined to be k³_T = (2.8 ± 0.4) × 10^?11 cm³ molecule^?1 s^?1 and k⁴_T = (7.2. ± 0.5) × 10^?11 cm³ molecule^?1 s^?1 at 293 K. It is shown that sigle quantum energy transfer can account for all the vibrational relaxation.     

Vibrational deactivation of HF(υ = 1) in the H2O + HF dimer: HF(υ = 1) + H2O(000) → HF(υ = 0) + H2O(001) + ΔE

The vibration-vibration energy transfer in the near-resonant collision HF(υ = 1) + H₂O(000) → HF(υ = 0) + H₂O(001) + ΔE = 205 cm^?1 has been investigated on the basis of the model of the nonrigid H₂O-HF dimer formation for temperatures not greatly higher than room temperature. The energy mismatch ΔE is considered to be removed by the slow translational motion of two molecules in the complex about their equilibrium separation. A strong negative temperature dependence of the energy exchange rate is shown between 300 and 500 K.     

Proton-conducting membranes: poly (N-vinyl pyrrolidone) complexes with various ammonium salts

The present study focuses on the proton-conducting polymer electrolytes; poly (N-vinyl pyrrolidone)–ammonium thiocyanate and poly (N-vinyl pyrrolidone)–ammonium acetate prepared by solution casting technique. The XRD analysis indicates the amorphous nature of the polymer electrolytes. The Raman spectra of the C=O vibration of pure polymer PVP at 1,663 cm^?1 has been appeared as doublet in the polymer electrolytes. The introduction of this new peak in the salt-doped polymer electrolytes may be due to interaction of the cation with the polymer. The room temperature ionic conductivity σ _303κ has been found to be high, 1.7?×?10^?4 S cm^?1 for 80 mol% PVP–20 mol% NH₄SCN and 1.5?×?10^?6 S cm^?1 for 75 mol% PVP–25 mol% CH₃COONH₄. The polymer electrolytes have been tested for their application in Zn–air battery.     

Spectrophotometric study of complexes of mercury(II) with mono- and dithiosemicarbazones

The formation of complexes at pH 4.7 of the Hg(II) with five monothiosemicarbazone and two dithiosemicarbazone has been studied. The mercury(II) reacts with monothiosemicarbazones of salicylaldehyde (λ_max = 363 nm, E = 1.69 × 10⁴liters · mol^?1cm^?1), pi-colinadehyde (λ_max = 363 nm, E = 2.38 × 10⁴liters · mol^?1cm^?1), 6-methyl-picolinaldehyde (λ_max = 363 nm, E = 2.28 × 10⁴liters · mol^?1cm^?1), di-2-pyridylketone (λ_max = 380 nm, E = 2.08 × 10⁴liters · mol^?1cm^?1), and o-naphthoquinone (λ_max = 540 nm, E = 1.03 × 10⁴liters · mol^?1cm^?1) and with dithiosemicarbazones of 1,4-dihydroxyphthalimide (λ_max = 430 nm, E = 2.56 × 10⁴liters · mol^?1cm^?1) and dipyridylglyoxal (λ_max = 363 nm, E = 2.37 × 10⁴liters · mol^?1cm^?1). A critical comparison of the stoichiometry and apparent stability constant of complexes with mono- and dithiosemicarbazones is given.     

The crystal structure of iododimethyl(trimethylamine)aluminum

The crystal structure of iododimethyl(trimethylamine)aluminium has been determined from single-crystal X-ray diffraction data collected by counter methods. I(CH₃)₂Al · N(CH₃)₃ crystallizes in the othorhombic space group Pnma with cell dimensions a=12.59(1), b=10.75(1), c=7.58(1)å, and p_calc=1.58 g·cm^?3 for Z=4. Least-squares refinement gave a final weighted R Value of 0.071 for 574 independet observed reflections. Each monomeric molecule lies on a crystallographic mirror plane with the trimethylamine and iododimethylaliminium groups in a staggered configuration about the aluminum  nitrogen bond.     

Magnetic exchange interaction in amide complexes of uranium (IV) tetrachloride

Magnetic exchange interaction in uranium (IV) complexes has been observed in UCl₄ · 3DMBA and UCl₄ · 3MAA with maxima at 135 and 142 K on the magnetic susceptibility—temperature curve, respectively. According to the Heisenberg model 2J_ex is obtained to be ?94 and ?99 cm^?1, respectively.     

Spectrophotometric study of the copper(II)-2,2′-dipyridyl-2-pyridylhydrazone complex formation

The reaction of copper(II) ions with 2,2′-dipyridyl-2-pyridylhydrazone (DPPH) has been studied. Two copper complexes were found to be formed. One at pH 6.5 to 8.5 and the other at pH 11.9 to 12.6 with molecular extinction coefficients of 1.9 × 10⁴M^?1 · cm^?1 at the absorption maximum of 478 nm and 3.8 × 10⁴M^?1 · cm^?1 at 448 nm, respectively. A sensitive spectrophotometric procedure for the determination of copper at less than a 1-ppm level is proposed.     

The vibrational spectrum of (trimethylenemethane)iron tricarbonyl

A vibrational assignment for the trimethylenemethane molecule, in [C(CH₂)₃]Fe(CO)₃, has been proposed for the first time. CC₃ stretches were found at 1348 (E) and 918 cm⁻¹ (A₁), with skeletal deformations at 802 cm⁻¹ (A₁, out-of-plane), and 471 cm⁻¹ (E, in plane). The Fe(CO)₃ vibrations were closely similar to those in analogous complexes.     

Spectrophotometric determination of microamounts of mercury(II) and sulfide ions in aqueous solution

Ammonium (2′,3′-dihydroxy pyridyl-4′-azo)benzene-4-arsonate (DHP-4A) provides a simple, rapid, and sensitive spectrophotometric microdetermination of mercury(II) in aqueous solution. The magenta colored 1:2 metal to ligand complex formed has a molecular extinction coefficient 6.25 × 10⁴ liters mol^?1 cm^?1 at the maximum absorption of 535 nm in highly alkaline medium. Beer's law is obeyed up to 3.8 ppm and Sandell's sensitivity (for an absorbance of 0.001) is 0.0032 μg of mercury(II)/cm². The mercury(II) complexed with DHP-4A has also been used in microdetermination of sulfide ions using ligand exchange reaction. The optimum concentration range of sulfide ions which can reproducibly be determined is 0.16-5.05 μg/10 ml and sensitivity of sulfide ions determination (for an absorbance 0.001) is 7.3 × 10^?4 μg/cm².     

An extraction-spectrophotometric determination of palladium with 4-(2-pyridylazo)resorcinol in the presence of diphenylguanidine

A new, sensitive spectrophotometric determination of palladium has been developed, based on the extraction of the red Pd(II) chelate with 4-(2-pyridylazo)resorcinol in the presence of N,N′-diphenylguanidine into n-butanol; the sensitivity of the method according to Sandell is S = 1.12 μg cm^?2, ?₅₃₀ = 9.4 × 10⁴ liters mol^?1 cm^?1, and palladium can be determined at concentrations from 0.21 to 1.91 μg ml^?1.     

The absorption spectrum of carbon monoxide in the CO(3Π r,a) state between 215 nm and 285 nm

Bye-beam excitation of a He/CO mixture the CO(³Π _r ,a) state was sufficiently populated to allow the measurement of the absorption spectrum. The (0, 0), (1, 1), (2, 2) and (0, 1) bands of thec ³Π←a ³Π system of CO have been observed and the molecular constantsT _e =92036.0 cm^?1 (for the band head), ω _e =2249.5 cm^?1, ω _e x _e =29.5 cm^?1 have been derived for CO(c). A new electronic state withT _e =91854.3 cm^?1, ω _e =848.4 cm^?1, ω _e x _e =9.8 cm^?1,B _e =1.351 cm^?1, and α _e =0.021 cm^?1 was identified to be a³Σ state. It seems to be very likely that this state is the CO (3pσ,³Σ,j) state discussed in the literature. The results indicate a perturbation of the υ=1 levels of the new state by the CO (c,υ=0) levels. Another strong perturbation is found in the υ=4 levels. The three CO(³Σ,b,υ′=0,1,2)←CO (a,υ″=0) bands were also investigated yielding for CO(b):T _e =83778 cm^?1, ω _e =2335 cm^?1, ω _e x _e =59 cm^?1 andB _e =1.86 cm^?1.     

Etude structurale par spectrometrie infrarouge et raman des composes de coordination: bis(pyridine)- trichloro aluminium(III) et bis(pyridine)tribromo aluminium(III)

The compounds AlX₃-2Py (X = Cl or Br, Py = C₅H₅N or C₅D₅N) have been prepared by using a method based on an exchange of organic ligands. The infrared and Raman spectra, which have been recorded between 50 and 4000 cm^?1, give strong evidence for the existence of the anion AlCl₄^? (or AlBr₄^?) and show that the cation is AlX₂(Py)⁺₄. The comparison of the spectra with those of the compound NiX₂(Py)₄., and of the cations trans-AlX₂(THF)₄⁺ and cis-AlX₂(bipy)₂⁺ indicates that the cation AlX₂(Py)₄⁺ has the helical configuration (helical trans-octahedron) and allows the assignment of the vibrations.     

Absolute rate constants for the reaction of O(3P) aroms with n-butane and NO(M  Ar) over the temperature range 298–439 K

Absolute rate constants for the reaction of O(³P) atoms with n-butane (k₂) and NO(M  Ar)(k₃) have been determined over the temperature range 298–439 K using a flash photolysis-NO₂ chemiluminescence technique. The Arrhenius expressions obtained were k₂ = 2.5 × 10^?11exp[-(4170 ± 300)/RT] cm³ molecule^?1 s^?1, k₃ = 1.46 × 10^?32 exp[940 ± 200)/ RT] cm⁶ molecule^?2 s^?1, with rate constants at room temperature of k₂ = (2.2 ± 0.4) × 10^?14 cm³ molecule^?1 s^?1 and k₃ = (7.04 ± 0.70)×10^?32 cm⁶ molecule^?2 s^?1. These rate constants are compared and discussed with literature values.     

A rapid method for the spectrophotometric determination of palladium(II) and osmium(VIII)

Propionyl promazine phosphate is proposed as a new reagent for the rapid spectrophotometric determination of microgram amounts of Pd(II) and Os(VII). PPP instantaneously forms an orange-red 1:1 complex with Pd(II) in sodium acetate-hydrochloric acid buffer of pH 0.8 to 4.0 at room temperature. The reagent also forms an orange-red radical cation with Os(VIII) in 0.5 to 2.0 M hydrochloric acid. The Pd-PPP complex exhibits an absorption maximum at 490–500 nm with molar absorptivity of 7.1 × 10³ liter mol^?1 cm^?1. The Os-PPP radical cation has an absorption maximum at 505–515 nm with molar absorptivity of 2.21 × 10⁴ liters mol^?1 cm^?1. The Sandell sensitivity is 0.022 μg/cm² (Pd) and 0.008 μg/ cm² (Os). Beer's law is valid over the concentration range 0.2 to 21 ppm (Pd) and 0.2 to 4.2 ppm (Os). The proposed method offers the advantages of simplicity, rapidity, and without the need for heating or extraction. The reagent is used for the determination of Pd in the synthetic mixtures corresponding to Pd alloys used in jewelery and Os in osmiridium alloy.     

Studies on the magnetic property of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2 (HOBz?Benzoic acid)

The magnetic property of μ₃-oxotriiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NP₃)-(CH₃OH)₂ (HOBz? benzoic acid) has been studied. We use isosceles triangle model and molecular field correction to fit the experimental magnetic susceptibility data. It shows that an intramolecular antiferromagnetic exchange interaction occurs with J = -31.27 cm^?1, J'= -27.26 cm^?1, and a weaker intermolecular antiferromagnetic exchange interaction occurs with zJ' = - 3.76 cm^?1. We give the d⁵-d⁵-d⁵ energy level diagram of triiron(III) complex as a function of J'/J. From the diagram we can get the total spin ST of the complex as 1/2 in the ground state.     

Spectral and magnetic properties of copper(II) furoate and copper(II) thiophene-2-carboxylate

Anhydrous copper(II) furoate and copper(II) thiophene-2-carboxylate have been Synthesized. They are formulated as dimeric species with four carboxylate bridges. The thiophene and furan moieties give rise to polymeric structures. Electron spin resonance spectra and magnetic susceptibility measurements show that the dimers have a singlet ground state and a thermally populated triplet state. The exchange coupling constants, 2J, are ?322 and ?312 cm^?1 for the furoate and thiophene-2-carboxylate complexes, respectively. The electronic and infrared spectra are also discussed.