Organometallic complexes for nonlinear optics Part 31. Cubic hyperpolarizabilities of ferrocenyl-linked gold and ruthenium complexes

The complexes [Fe{eta-C5H4-(E)-CH=CH-4-C6H4C- CX}2] [X = SiMe3 (1), H (2), Au(PCy3) (3), Au(PPh3) (4), Au(PMe3) (5), RuCl(dpPM)(2) (7), RuCI(dppe)(2) (8)] and [Fe{eta-C5H4-(E)-CH=CH-4-C6H4CH=CRuCl(dPPM)(2)}(2)](PF6)(2) (6) have been prepared and the identities of 1 and 7 confirmed by single-crystal X-ray structural studies. Complexes 1-8 exhibit reversible oxidation waves in their cyclic voltammograms attributed to the Fe-II/III couple of the ferrocenyl groups, 6-8 also showing reversible (7, 8) or non-reversible (6) processes attributed to Ru-centered oxidation. Cubic nonlinearities at 800 mn by the Z-scan method are low for 1-5; in contrast, complexes 6 and 7 exhibit large negative gamma(real) and large gamma(imag) values. A factor of 4 difference in \chi\ and two-photon absorption cross-section 62 values for 6 and 7 suggest that they have potential as protically switchable NLO materials. (C) 2002 Elsevier Science B.V. All rights reserved.