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A relation between the quadrupole coupling constant e2Qqzz and asymmetry parameter η has been found for a series of meta-substituted iodobenzene derivatives. The relationships e2Qqzz(η) for electrondonor and electron-acceptor substituents have the same form but different numerical values of parameters. The average time of full electron transfer via tunneling has been evaluated.

35Cl, (79,81)Br, and (127)I NQR (nuclear quadrupole resonance) spectroscopy in conjunction with X-ray crystallography is potentially one of the best ways of characterizing secondary bonding of metal cations such as Ag(+) to halogen donor atoms on the surfaces of very weakly coordinating anions. We have determined the X-ray crystal structure of Ag(O(3)SCH(2)Cl) (a = 13.241(3) A; b = 7.544(2) A; c = 4.925(2) A; orthorhombic; space group Pnma; Z = 4) and compared it with the known structure of Ag(O(3)SCH(2)Br) (Charbonnier, F.; Faure, R.; Loiseleur, H. Acta Crystallogr., Sect. B 1978, 34, 3598-3601). The halogen atom in each is apical (three-coordinate), being weakly coordinated to two silver ions. (127)I NQR studies on Ag(O(3)SCH(2)I) show the expected NQR consequences of three-coordination of iodine: substantially reduced NQR frequencies nu(1) and nu(2) and a fairly small NQR asymmetry parameter eta. The reduction of the halogen NQR frequency of the coordinating halogen atom in Ag(O(3)SCH(2)X) becomes more substantial in the series X = Cl < Br < I, indicating that the coordination to Ag(+) strengthens in this series, as expected from hard-soft acid-base principles. The numbers of electrons donated by the organic iodine atom to Ag(+) have been estimated; these indicate that the bonding to the cation is weak but not insignificant. We have not found any evidence for the bonding of these organohalogen atoms to another soft-acid metal ion, thallium. A scheme for recycling of thallium halide wastes is included.

NQR (nuclear quadrupole resonance) spectroscopy is potentially one of the best ways of characterizing the bonding of metal cations such as zirconocene cations and Ag+ to halogen donor atoms in weakly coordinating anions and neutral ligands such as halocarbons. Known coordination of organoiodine atoms to silver ions was studied by 127I NQR spectroscopy in [Ag(p-C6H4I2)](PO2F2), [Ag(o-C6H4I2)]N03 , [Ag(CH2I2)2]PF6, and the explosive [Ag(CH2I2)]NO3 ; a possible case of iodocarbon coordination to a mercury atom in C5Cl5HgCl ·CH2I2 was also investigated. Both the low-frequency (ca. 300 MHz) and the high-frequency (ca. 500 MHz) NQR signals were detected for each compound, and, for the first time, the quadrupole coupling constants e2Qqzz/h and asymmetry parameters ηof coordinated organohalogen atoms were obtained. As compared to the free iodocarbons, substantial (4 - 12%) reductions of e2Qqzz/h and substantial increases in η (to about 20 - 40%) were found in the iodocarbon complexes of silver, but not of mercury. From approximate theoretical analysis of the data, it appears that the electronic interaction of silver and iodine is quite substantial.

This is a review of investigations on iodo-benzoic acid, iodohippuric acid, and iodophenol derivatives by NQR, NMR, and emission Mössbauer spectroscopy. The influence of intermolecular, intramolecular, and bifurcated O-H…I and O-H…O bonds on the properties of iodine-carbon bonds is demonstrated. Ionized and non-ionized forms of tyrosine differ by the probability of H-bond formation. The simultaneous use of 127I NQR and emission Mössbauer 125I spectroscopy open the possibility to determine the types of tellurium-organic substances formed in the process of K-decay of 125I.

The full127I NQR spectra of a series of iodo-substituted phenols and phenylmercury phenoxides have been studied. The quadrupole coupling constants and asymmetry parameters have been determined. The character of the OH...Hal hydrogen bond has been found to depend on the nature of substituents in the ring. Correlation dependences of the asymmetry parameters on the sum of the substituents resonance constants have been found for both coordinated as well as for non-coordinated iodine atoms.

We have studied the complete127I spectra and obtained the values of the quadrupole coupling constants e2Qqzz and the asymmetry parameters η in a series of substituted α-iodothiophenes. Using an additive scheme, we have calculated e2Qqzz and determined the substituent increments.

1. For a series of iodonium compounds of the Ar2IX type, it has been found that the127I NQR parameters — the quadrupole coupling constant e2Qqzz, the asymmetry parameter η, and the frequency field constant ϖv/ϖEz -vary regularly with the nature of the cation and the character of substitution in the ring. 2. Strengthening of the coordination interactions leads to a sharp jump in the frequency field constant ∂v/∂Ez and a significant change in the asymmetry parameter η. 3. For this series of compounds, a linear, correlation has been established between the values of e2Qqzz and η.

Br79 NQR frequencies of a number of bromothiophene derivatives have been measured at 77°K. The frequencies correlate with Hammett δ values and this correlation demonstrates the importance of the inductive effect. The influences of more than one substituent on the thiophene ring are additive.

We were the first to study the complete NQR spectra of iodine for a number of haloaliphatic compounds. An additive scheme for calculating the NQR frequencies in the HnCl4−n series was constructed. The values of the asymmetry parameters in the studied compounds were analyzed.

Im Rahmen einer Diskussion uber den Mechanismus der Bildung von 1,1 , l-Trinitro- athan wird die Komplexbildung von Halogentrinitromethanen mit .Dioxan, Dimethylsulfoxid, Dimethylnitrosamin, Diphenylnitrosamin, Diazodimedon, Durol, Pyridin- "N-oxid, N-Methyl-succinimid und Tetrahydrofuran untersucht.

The127I NQR spectra of the tetraiodo-, triiodonitro-, and diiodonitrotrifluoromethylthioethylenes were studied. The frequencies of the iodine atoms increase when electron-acceptor substituents are inserted into the molecule of iodoethylenes.

Iodonitromethane forms nσ complexes with organic ligands with low127I asymmetry parameters and positive charge on the iodine atom.

NQR spectroscopy was used to find the localization of formal positive charge on the chlorine and bromine atoms in ClOSO2F and BrOSO2F.

A considerable increase in the quadrupole coupling constants (e2Qqzz) and significant decrease in the asymmetry parameterη is found in carborane-containing CBICl2 and PhCBIX compounds in comparison with the corresponding phenyl and diphenyl derivatives.

The complete79Br and127I NQR spectra of a number of bromo and iodo derivatives of acetylene were studied for the first time, and the field constants of the NQR frequencies were determined. It was found that the asymmetry parameters in them are low. Changes in the field constants are determined by the competing conjugation of the iodine atom and the corresponding substituents.