George A. Vidulich

A direct hydrogen-1 and phosphorus-31 nuclear magnetic resonance cation solvation study of Al(ClO4)3, Ga(ClO4)3, In(ClO4)3, UO2(ClO4)2, and UO2(NO3)2 in water-acetone-dimethylsulfoxide and water-acetone-hexamethylphosphoramide mixtures

A competitive solvation study of Al(ClO4)3, Ga(ClO4)3, In(ClO4)3, UO2(ClO4)2, and UO2(NO3)2 in water-acetone-dimethylsulfoxide (DMSO) and water-acetone-hexamethylphosphoramide (HMPT) mixtures has been carried out by direct H1 and P31 nuclear magnetic resonance (NMR) techniques. At low temperature, proton and ligand exchange are slow enough in these systems to permit the observation of signals for bulk and coordinated molecules of water and the organic bases (DMSO and HMPT). Both DMSO and HMPT compete effectively with water for coordination sites in the Al3+, Ga3+, and In3+ systems, with steric effects dominating the HMPT results. Both Al3+ and In3+ are able to bind a maximum of two to three HMPT molecules, for example. In contrast, UO2+ is solvated selectively by the organic molecules to the allowed maximum of 4 molecules per cation. H1 and P31 NMR spectral results support the formation of only the mono-, tri-, and tetra-HMPT solvation complexes.

A direct carbon-13 nuclear magnetic resonance study of boron trihalide complexes with several ethers

Abstract The preliminary results of a direct, low-temperature 13 C NMR study of BF 3 and BCl 3 complexes with a series of ethers are reported. By lowering the sample temperature to slow exchange, it is possible to observe separate 13 C signals for coordinated and free ligand molecules. The 13 C chemical shifts at the α-carbon produced by complex formation are to lower field and they decrease in the order THF > Et 2 O > Pr 2 O ≅ Bu 2 O. The 13 C signals for all other carbon atoms in these ethers are displaced to higher field in the complexes. A preliminary interpretation in terms of ligand basicity, and possible electronic changes occurring in the complexes is presented.

Direct carbon-13 nuclear magnetic resonance study of boron trifluoride and boron trichloride complexes with ethers

A direct, low-temperature, 13C n.m.r. study of the boron trifluoride and boron trichloride complexes with several ethers has been completed. At ca.–100°, ligand exchange is slow enough to permit the observation of separate signals for bulk and co-ordinated ether molecules. The chemical shift changes induced by complex formation reflect inductive and steric effects. Doublet patterns were observed for the signals of co-ordinated ethyl s-butyl, ethyl t-butyl, and di-isopentyl ether. The most reasonable interpretation of this result appears to be hindered rotation about the O–R bond in the complex.

A direct low-temperature carbon-13 and fluorine-19 nuclear magnetic resonance study of boron trifluoride complexes with pyridines

Complexes of boron trifluoride with a series of substituted pyridines have been studied using a direct, low-temperature 13C and 19F n.m.r. technique. At temperatures from 0 to –40 °C, ligand exchange is slow enough to permit the observation of separate 13C n.m.r. signals for bulk and co-ordinated pyridine molecules. The co-ordinated pyridine shift displacements are interpreted in terms of ligand polarization and a paramagnetic effect at the nitrogen atom. The BF319F n.m.r. chemical shifts were correlated with calorimetric data in several cases, and in general provide a measure of the strength of the interaction but not of ligand basicity. Comparative complexing abilities were evaluated by studying several pyridine mixtures.

A carbon-13 nuclear magnetic resonance relaxation time study of streptoxotocin-deoxyguanosine-5′-monophosphate-deoxycytidine-5′-monophosphate interactions☆

Abstract We wish to report the observation of Watson-Crick base pairing between deoxyguanosine-5′-monophosphate (dGMP) and deoxycytidine-5′-monophosphate (dCMP), and the nature of the interaction of streptozotocin, an anticancer agent, with these mononucleotides, all in aqueous solution. Fourier transform carbon-13 ( 13 C) nuclear magnetic resonance (nmr) relaxation time (T 1 ) measurements provided the evidence for complex formation. The dCMP 13 C relaxation times are far more sensitive to the presence of dGMP rather than the antibiotic, whereas dGMP interacts strongly with both dCMP and streptozotocin. A description of these complexes and a correlation of these results with the observed clinical behavior of streptozotocin will be given.