mr*" and "nr*" excitation energies calculated by the INDO/S method13 at these geometries (Table I) reflect the experimental trends correctly but are a little too low, as was also the case for other imines.5•6 The structure assignment of the nitrene 4 is based on its ESR signal at 0.8124 T (9.3 GHz; assuming E = 0, \D/hc\ = 1.65 cm™1),14 a sharp UV peak at 33 560 cm™1, whose intensity follows that of the ESR signal,15 and on photochemical trapping with CO in Ar at 36 K. The IR spectrum of this matrix, containing 2, 3, CO, and presumably 4, was unchanged for many hours in the dark, but on UV irradiation7' a weak band of 1-norbornyl isocyanate at 2263 cm™1 appeared16 (IR, MS, and GC comparison with an authentic sample).To our knowledge, the above results represent the first observation of geometrical isomerism at a strained bridgehead double bond. Taken together with prior work,2™6 they suggest that the C=N stretching frequencies are typically reduced by about 100 cm™1 in Zzvm-azacycloheptene rings and by about 200 cm™1 in iranr-azacyclohexene rings, respectively, relative to an unstrained imine.Acknowledgment. This work was supported by the National Science Foundation (CHE 81-21122).
Nous avons Qtudid les spectres XANES de complexes du Mn(II),Mn(III), Mn(1V) , dont la structure et les proprietes electroniques sont parfaitement connues. Nous distinguons trois zones : preseuil, seuil et post-seuil. Nous discutons les variations observees en fonction du degre d'oxydation, de la g6ometrie et de la nuclearits. Les preseuils prdsentent une structure que nous comparons d la levee de ddggnerescence des orbitales d obtenue par spectroscopie visible et proche infra-rouge. Un deplacement important du seuil est observd lorsque la nuclearit6 et/ou la ggometrie varie. Les differences dans la partie post-seuil, pour le chromophore Kn(III)O6 sont lieec d la stereochimie de l'octaedre.
The potentially penta‐ or hexadentate Schiff base ligands result from the condensation of salicylaldehyde or its 5‐nitro derivative with diaminopropanol or tri‐ or tetraamines.
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