Electric and magnetic properties of hexaethynylbenzene

Coupled Hartree-Fock theory is used to compute the magnetizability and nucl ear shielding tensors of hexaethynylbenzene (HEB), and to map the electron current density induced by an external magnetic field. The electric quadrup ole moment and polarizability are also computed, and compared with those of benzene and ethyne. The calculations of magnetic properties demonstrate th e clear superiority of distributed-origin methods over the conventional com mon-origin method in which a single fixed origin of vector potential is use d. It is shown that the CTOCD-PZ2 formulation provides an efficient and acc urate method for the magnetic properties. The current-density maps of HEB s how the characteristic pi ring current associated with the delocalization o f pi electrons around the central ring of carbons and local circulations in the ethynyl groups. There is no evidence of a significant induced current linking the ethynyl groups, either through space or through bond. The exper imental shielding constants of HEB are well reproduced by the CTOCD-PZ2 cal culations, and an analysis of the computed shielding tensors is used to pro vide a detailed interpretation of the NMR spectrum.