Magnetic properties of Cu(II) bischelate complexes with 3-imidazoline nitroxides. 1. Anab initio analysis of spin density delocalization channels

Spin density redistribution between the paramagnetic centers Cu²⁺, N-O, and N’-O’ of bischelate complexes CuL₂ of the copper ion with enaminoketone 3-imidazoline nitroxides (L) are investigated using an ab initio RHF (restricted Hartree-Fock) approach. The most important channels of unpaired electron delocalization over the systems of π- and Σ-bonds in such complexes are revealed. The conformation dependence of spin density localized on paramagnetic centers and delocalized due to a distortion of the structure of the environment of the Cu²⁺ ion from square planar to tetrahedral is analyzed and explained. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 5, pp. 840–849, September-October, 1997.     

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Nucleon-nucleon interaction and some reactions with3He,3H

Experimental measurements and theoretical calculations are discussed for theA = 3 nuclei. With the sum rule formalism, the need for a better bound state is investigated. Some reactions on³He and³H like electron scattering, photodisintegration,-capture involve transitions to the continuum but with the work developed by Merkuriev, Gignoux and Laverne (1976) some progress is possible. The same realisticNN interactions used for calculating the bound state wave function of the three nucleon system are incorporated in the scattering equations based on the Faddeev approach.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.     

Coloring of universal graphs

LetG be a graph andr a cardinal number. Extending the theorem of J. Folkman we show that if eitherr or clG are finite then there existsH with clH = clG andH (G) _r ¹ . Answering a question of A. Hajnal we show that countably universal graphU ₃ satisfiesU ₃ (U₃) _r ¹ for every finiter.     

Calcul théorique des énergies de divers arrangements géométriques de la molécule (η5-C5H5)2TiCl2

The molecular energy of the complex (η⁵-C₅H₅)₂TiCl₂ has been calculated for experimental geometry and for several hypothetical forms by a semi-empirical CNDO/2 approach. The energy difference between experimental (quasi-tetrahedral) geometry and a planar geometry is ca. 20 kcal mol^?1. This difference is sufficiently high to explain the difficulty of the inversion process.     

2-Vinylcyclobutanones by Cycloaddition of Vinylketenes to Simple Olefins

Selected [2+2]-cycloadditions of three alkylvinylketenes 2 to one mono- and seven dialkyl-olefins 3 yielded eleven 2-alkyl-2-vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl-elimination from α,β-unsaturated acid chlorides 1 ; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]-cycloadditions were fully regio- and stereoselective with respect to the olefin 3 , but less so with respect to the ketene 2 , so that - where possible - two stereoisomers of 4 resulted, namely A and B , whose configurations were determined from their ¹H-NMR, spectra, mechanistic considerations and, in one case, 4f , by chemical correlation with a previously known cycloadduct 8 .