The novel link between planar mobius aromatic and third order nonlinear optical properties of metal-bridged polycyclic complexes

Metal-bridged polcyclic aromatic complexes, exhibiting unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement, have been established as unique "carbonloong chemistry". Herein, the electronic structures, aromaticities, absorption spectra and third order nonlinear optical (NLO) responses of metal-bridged polcyclic aromatic complexes (M = Fe, Re, Os and Ir) are investigated using the density functional theory computations. It is found that the bridge-head metal can stabilize and influence rings, thus creating pi-, sigma- and metalla-aromaticity in an extended, pi-conjugated framework. Interestingly, metal radius greatly influence the bond, aromaticity, liner and third order NLO properties, which reveals useful information to develop new applications of metal regulatory mechanism in NLO materials field. Significantly, the novel relationship between the aromaticity and third order NLO response has firstly been proposed, that the metal-bridged polycyclic complex with larger aromaticity will exhibit larger third order nonlinear optical response. It is our expectation that the novel link between aromaticity and NLO response could provide valuable information for scientists to develop the potential NLO materials on the basis of metal-bridged polycyclic complexes.