Gilbert Gordon

Electron Paramagnetic Resonance Spectra of Zinc‐Doped Copper Acetate Monohydrate

The electron paramagnetic resonance of the copper—zinc pairs in zinc‐doped copper acetate monohydrate has been observed at 77°K by using an X‐band EPR spectrometer. Single crystals containing less than 1% zinc ions were grown from a slightly acidic aqueous solution containing about 75% copper acetate and 25% zinc acetate.The experimental results could be fit to the spin Hamiltonian: H=gzβHzSz+gxβHxSx+gyβHySy+AzSzIz+AxSxIx+AySyIy. The values Az=0.0147±0.006 cm−1, Ax<0.0018 cm−1, and Ay<0.0023 cm−1 were measured for the doublet‐state cupric ions. The g values were found to be: gz=2.344±0.005, gx=2.052±0.007, and gy=2.082±0.007.These results are consistent with the model proposed by Slichter, in which he has shown that the components of the hyperfine tensor should be twice as large for a doublet species as compared to the corresponding triplet species when the exchange integral J is much larger than the components of the hyperfine tensor.Since the microsymmetry at the cupric ion site is no higher than C2v, t...

Magnetic and Optical Spectra of Two Dimeric Copper Chloride Pyridine‐N‐Oxide Complexes

The electron paramagnetic resonance spectra and the optical absorption spectra of dichlorobispyridine‐N‐oxide copper(II) [(C5H5NO)2CuCl3] and dichloromonoaquopyridine‐N‐oxide copper(II) [C5H5NOCuCl·H2O] have been observed at room temperature. The magnetic resonance studies were carried out at both X‐band and K‐band frequencies. The observed spectra could be fit to an S=1 spin Hamiltonian. The direction of the maximum zero‐field splitting did not correspond to the principal z axis of the g tensor. For (C5H5NO)2CuCl2 the angle between these two directions was about 23° and for C5H5NOCuCl·H2O the angle was about 27°. A study of the intensity of the EPR signal as a function of temperature indicated that the triplet state was about 550 cm−1 above the single ground state for (C5H5NO)2CuCl2 and about 885 cm−1 above the singlet state for the other complex. The optical spectra of both examples revealed two bands in the 8000‐to−15 000‐cm−1 region and a higher energy transition at about 22 000 cm−1.

Near infrared spectra of water and aqueous solutions

Abstract Spectra ranging from 4000 to 12,500 cm −1 were obtained with H 2 O, D 2 O, D 2 Oue5f8H 2 O mixtures, and solutions of these solvents containing various ionic species. The shapes and/or positions of these bands were influenced by both temperature and dissolved salts. In the 8300-cm −1 region, a pronounced band was observed at 8640 cm −1 with H 2 O near the boiling point, whereas with ice a broad but rather well-formed band was observed at 7990 cm −1 . In H 2 O at room temperature or below a very broad and deformed band appeared at 8310 cm −1 with a distinct shoulder around 8600 cm −1 , which became more apparent with an increase in temperature. The effect of dissolved species on the spectrum of H 2 O was very similar to the observed temperature effect, and the relative intensity of the absorption at 8640 cm −1 and at 8310 cm −1 seems to be indicative of the degree of “structure-breaking” or “structure-making” power of the dissolved species. The order of increasing structure-breaking (or decreasing structuremaking) power deduced from the spectra was C Cl − − − 4 − and Li + + + + 3 ) 4 + . This is in good agreement with the published results from measurement of other properties of solutions. Similar temperature and salt effects were also observed with other bands of H 2 O and D 2 O.

Oxygen‐17 NMR and Copper EPR Linewidths in Aqueous Solutions of Copper(II) Ion and 2,2′‐Dipyridine

Between 0° and 60°C the transverse relaxation rate of oxygen‐17 nuclei in water is increased in proportion to the concentration of diaquobis (2,2′‐dipyridine) copper(II) which exists in equilibrium with the tris(chelate) species in solutions of tris(2,2′‐dipyridine) copper(II) nitrate. The excess relaxation rate 1u2009/u2009T2p due to the presence of the paramagnetic ions is controlled by the rate of relaxation of oxygen‐17 nuclei in the coordination sphere of the [Cu(dipy)2(OH2)2]+ + species where the paramagnetic electron–oxygen‐17 hyperfine interaction ALu2009/u2009h is of the order of 1.0u2009×u2009107 Hz. This value is large in comparison with the one previously reported for diaquobis (ethylenediamine) copper(II), where the two water molecules occupy positions trans with respect to each other on the long axis of the Jahn–Teller distorted complex. The X‐band EPR spectrum of an ethanol–water glass where 2,2′‐dipyridine/copper(II) ratio is 2.00 indicates that the cis and the trans isomers of the diaquobis (2,2′‐dipyridine) cop...

Electron Paramagnetic Resonance Spectra of Two Zinc‐Doped and Nickel‐Doped Copper Chloride Pyridine‐N‐Oxide Complexes

The electron paramagnetic resonance spectra of zinc‐doped dichlorobispyridine‐N‐oxide copper(II) [(C5H5NO)2Cu(Zn)Cl2] and zinc‐doped dichloromonoaquopyridine‐N‐oxide copper(II) [C5H5NOCu(Zn)Cl2·H2O] have been observed at liquid‐nitrogen temperature. The data could be fit to the usual S=½ spin Hamiltonian. The g values obtained in this study for the copper—zinc pairs agree with the g values obtained for the copper—copper pairs in the pure material to within experimental uncertainty. Copper hyperfine splittings and chlorine superhyperfine splittings were also observed. The magnetic parameters for (C5H5NO)2Cu(Zn)Cl2 are gz=2.323, gx=2.056, gy=2.080, Az=129×10−4 cm−1, Ax=Ay<10×10−4 cm−1, A′=25×10−4 cm−1, and B′=7×10−4 cm−1, while for C5H5NOCu(Zn)Cl2·H2O gz=2.306, gx=2.056, gy=2.083, Az=139×10−4 cm−1, and Ax=Ay<10×10−4 cm−1 obtain. An analysis of the data with a simple LCAO MO approach suggests relatively strong metal—ligand bonds.The data obtained from the study of nickel‐doped (C5H5NO)2CuCl2 could be fit to ...

Magnetic and Optical Spectra of Copper Monochloroacetate 2.5 Hydrate

The electron paramagnetic resonance spectra of copper monochloroacetate 2.5 hydrate, Cu(O2CCH2Cl)2·2.5H2O, [Cu(ClAc)2], and zinc‐doped Cu(ClAc)2 have been observed at both K‐band and X‐band frequencies. The EPR spectrum of the pure material was characteristic of a species with a spin of one, while the spectrum from zinc‐doped Cu(ClAc)2 revealed an additional spectrum due to a species with a spin of ½. The g values for both the copper—copper pairs and the copper—zinc pairs were identical with values gz=2.38 and gx=gy=2.07. The hyperfine coupling constant for the copper—copper pairs was about 84×10−4 cm−1, while in the copper—zinc spectrum it was about 158×10−4 cm−1. These results are consistent with the assumption of a weakly coupled interaction. The temperature variation of the doubly integrated intensity of the derivative spectrum indicated that the triplet state lies some 230 cm−1 above the singlet ground state. In the optical absorption spectrum of Cu(ClAc)2 three bands were observed. A very intense ba...

Determination of oxygen-18 in inorganic compounds

A relatively simple and rapid method has been developed for the analysis of the oxygen-18 content of many inorganic compounds including water. The samples are heated with silver cyanide at 500 degrees and the carbon dioxide formed is separated from the other products by means of a methylcyclohexane slush at -130 degrees and analysed mass spectrometrically.

The silver-catalyzed homomolecular oxygen exchange reaction☆

Abstract The silver-catalyzed homomolecular exchange reaction between oxygen-16 and oxygen-18 has been studied in the 500–700 °C temperature range. In the presence of silver wire between 500 ° and 575 °, the activation energy is 29.4 kcal/mole and the order of the reaction with respect to oxygen is 0.52. At 650 °, the order of the reaction with respect to the oxygen pressure decreases to 0.20 and the activation energy for the process is only 16.5 kcal/mole. The effect of the silver catalyst on the heterogeneous exchange between oxygen gas and sodium molybdate, sodium chromate, and potassium sulfate was also studied and these results are compared with those in the absence of the catalyst. A comparison of the activity of silver with that of the other noble metals as catalysts for the oxygen exchange reaction is made.

Oxygen-18 exchange reactions between gaseous oxygen and certain oxygen-containing inorganic salts☆

Abstract Rate measurements have been carried out on the 18O exchange reaction between oxygen gas and certain alkali metal chromates, molybdates, tungstates, phosphates and sulphates in the 600–850°C temperature range. It was observed that the rate of exchange was influenced by the nature of the cation and the nature of the central atom. In the alkali metal chromate series, the potassium salt exhibited the least tendency to exchange, but the activation energy for the exchange process was observed to decrease with an increase in the cation radius. In contrast, both the rate of exchange and the activation energy decreased as the effective nuclear charge of the central atom increased, as the central atom-oxygen bond distance decreased, and as the oxidation state of the central atom increased. A mechanism is proposed for the exchange reaction and a correlation between the rate of exchange and various thermal and thermodynamic properties is presented.

The homomolecular exchange of oxygen isotopes at high temperatures

Abstract The homomolecular exchange reaction of oxygen isotopes between molecular species of oxygen: 16 O 2 + 18 O 2 = 2[ 16 O 18 O] was investigated in the 685–750° temperature range. Below 100 torr, the rate of exchange was found to be second order with respect to the total oxygen pressure which suggests the formation of an [O 4 ] species for the exchange reaction. The rate of the reaction increased with an increase in the surface to volume ratio of the quartz reaction vessel. The activation enthalpy was 47·8 kcal/mole and the activation entropy was −37 e.u.