Toward the synthetic control of the HOMO-LUMO gap in binuclear systems: insights from density functional calculations.

Computational methods based on density functional theory have been applied to address the design of tailored HOMO-LUMO gap bimetallic complexes. We focus our attention on the [Cp*Fe-(L)-FeCp*] system, where two ferrocenyl units are linked through the dianion of fused ring ligands such as pentalene, s-indacene, dicyclopenta-[b,g]-naphthalene, dicyclopenta-[b,i]-anthracene and dicyclopenta-[b,l]-tetracene. Our DFT calculations on the title organometallic complexes suggest a controlled decrease in the HOMO-LUMO gap, which is desirable for studies on electron-transfer phenomena, as well as the design potential devices for molecular electronic purposes.

Inside a superatom: the M7q (M=Cu, Ag, q=1+, 0, 1-) case.

All-electron relativistic density functional calculations are performed to obtain the electronic structure and nucleus-independent chemical shifts (NICS) of D(5h) pentagonal-bipyramidal (PBP) Cu(7)(q) and Ag(7)(q) (q=1+,0,1-) clusters. Scalar and spin-orbit relativistic effects are taken into account at two levels: the two-component zero-order regular approximation (ZORA) Hamiltonian and fully relativistic four-component calculations via the Dirac equation. These clusters are treated by including the spin-orbit effect in the jellium model, within the double-valued point group (D(5h)*) establishing the symmetry correlations between the molecular and the atomic spinors given by the full rotation group. These clusters show highly spherical aromaticity, which is suggested to increase the hardness of the superatom. Thus, the calculations suggest that the paramagnetic Cu(7) and Ag(7) clusters can be regarded as pseudohalogens.