We have measured the third-order susceptibility, chi(3), versus concen
tration for a number of molybdenum-base metal-organic complexes in sol
ution, using independent degenerate four-wave mixing and Z-scan techni
ques. Good agreement was obtained between the degenerate four-wave mix
ing and Z-scan measurements. The variation of chi(3) with concentratio
n yielded the second-order hyperpolarizability gamma. A close correlat
ion was observed between the number of delocalized pi electrons and th
e magnitude of gamma.