Second-order non-linear optical response of metallo-organic compounds: towards switchable materials

A series of coordination compounds, [M(PM-L)2(NCS)2], with large aromatic ligands (PM-L) and a divalent metal ion (MII=Mn, Fe, Co, Ni and Zn) have been synthesized. The magnetic data are consistent with divalent metal ions in an octahedral ligand field environment. Hyper-Rayleigh scattering measurements show an enhancement of the molecular hyperpolarizabilities (β) from Ni compounds (with two unpaired electrons) to Mn compounds (five unpaired electrons). In the case of the Fe(II) metal ion, the influence of the ligand on the β values is reported. This work provides attractive information for the design of switchable materials based on the spin-crossover phenomenon.