Second-order nonlinear optical properties of transition metal complexes

This contribution presents an overview of the principal classes of second-order nonlinear optical (NLO) transition metal (organometallic and coordination) complexes and illustrates how organometallic and coordination chemistry can offer a very large variety of NLO structures in relation to the metal nd configuration, oxidation state, spin state, etc. Moreover, metal complexes can satisfy the very different demands of second-order NLO materials such as switchable, tuneable, and multidimensional NLO properties, depending on the subtle interplay of structure-property relationships. Recent advances and perspectives in metal complexes as NLO materials are also presented.