Computer Simulations of Chiromagnetic Nanoparticles

The light-matter interaction is one of our main tools for transmitting, processing and storing energy and information. We have recently demonstrated that imprinting chirality on paramagnetic cobalt oxide nanoparticles allows the absorption of light to be modulated by an external magnetic field over a wide range of wavelengths.1 The chirality transfer mechanism involved doubly-coordinated cysteine molecules occupying and distorting octahedral positions around Co(lll) atoms at the surface, as demonstrated by the B3L YP/6-31G geometry optimizations and ab initio molecular dynamics simulations. The DFT calculations also demonstrated that spin density is highly localized in the Co(ll) atoms at the tetrahedral positions of the lattice. Calculated electronic circular dichroism was in excellent agreement with the experimentally measured spectra and provided a detailed description of the individual electronic transitions for both alpha and beta electrons. The behavior of paired and unpaired electrons was very distinct, with alpha electrons being preferably excited to LUMO, which was located on a Co(lll) surface atom, whereas beta electrons close to the gap were excited to other orbitals besides LUMO (Figure 1). The possibility to pump electronic density into a surface site opens many possibilities in photocatalysis applications and magnetooptics. References: (1) Yeom, J.; Santos, U. S.; Chekini, M.; Cha, M.; de Moura, A. F.; Kotov, N. A. Science 359: 309-314 (2018). -