On the qualitative theoretical NMR chemical shifts of model carbyne catenanes and knots

The qualitative C-13 NMR chemical shift (delta) calculated for carbyne: cyc les (C-10, C-20,..., C-60), catenanes (C10C30 and C20C30), knots (C-30 and C-60 trefoil, and C-40 and C-64 figure-8), have shown delta to tend to alte rnate along the catenane or a knot branch and to follow neither the change in the partial charge nor the change in the angles, The delta alternation i s associated with the repulsion between catenane components or knot branche s which polarizes the pi electrons so that the atoms of each C dropC bond a re differentiated to one closer to and one other further from the perturbat ion. (C) 2001 Elsevier Science B.V. All rights reserved.