Organometallic Complexes for Non-Linear Optics. 51. Second- and Third-Order Non-Linear Properties of Alkynylgold Complexes

Chris Corkery, The University of Western Ontario
Adam Barlow,
Bandar Babgi,
Marek Samoc,
Stijn van Cleuvenbergen,
Inge Asselberghs,
Koen Clays,
Marie P. Cifuentes,
Mark G. Humphrey,

Abstract

The alkynes HC≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2 (4) and HC≡CC6H4-4-C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2 (6) and gold alkynyl complexes Au{C≡CC6H2-2,5-(OEt)2-4-C≡CC6H4-4-NO2}(PPh3) (7), Au(C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2)(PPh3) (8), and Au(C≡CC6H4-4-C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2)(PPh3) (9) have been synthesized. The linear optical properties and quadratic optical non-linearities of 7–9 have been measured, the latter by hyper-Rayleigh scattering at 1064 nm, and compared with data for the previously reported complexes Au(C≡CC6H4-4-NO2)(PPh3) (10) and Au(C≡CC6H4-4-C≡CC6H4-4-NO2)(PPh3) (11). The optical absorption maximum red-shifts and the first hyperpolarizabilities increase on π-system lengthening and on introduction of electron-releasing substituents on the π-bridge ring adjacent to the metal centre. The cubic non-linear optical properties of 1,4-{(PCy3)Au(C≡C)}2C6H4 (12) and {(PCy3)Au(C≡C-4-C6H4C≡C)}6C6 (13) have been assessed by wide spectroscopic range femtosecond Z-scan studies; the maximal values of the imaginary component and the effective two-photon absorption cross-section increase markedly on proceeding from linear complex 12 to 6-fold-symmetric complex 13, an increase that is maintained when data are scaled by relative molecular weight.