Abstract A series of D 3 (Fe II, Ru II, Zn II, Hg II) and D 2d (Cu I, Ag I, Zn II) octupolar metal complexes featuring different functionalized bipyridyl ligands has been synthesized, and their thermal, linear (absorption and emission), and nonlinear optical (NLO) properties were determined. Their quadratic NLO susceptibilities were determined by harmonic light scattering at 1.91 μm, and the molecular hyperpolarizability (β 0) values are in the range ...