Organometallic complexes for nonlinear optics: Part 23. Quadratic and cubic hyperpolarizabilities of acetylide and vinylidene complexes derived from protected and free formylphenylacetylenes

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The acetylenes 4-HCCC 6H 4R [R=CH{OC(O)Me} 2 ( 1), CHO(CH 2) 3O ( 2)], ruthenium complexes [Ru(4-CCC 6H 4R)(PPh 3) 2(η-C 5H 5)] [R=CH{OC(O)Me} 2 ( 3), CHO ( 4)], [Ru( n-CCHC 6H 4R)Cl(dppm) 2]PF 6 [ n=4, R= CHO(CH 2) 3O ( 7); R=CHO, n=3 ( 11), 2 ( 15)], and [Ru( n-CCC 6H 4R)Cl(dppm) 2] [ n=4, R= CHO(CH 2) 3O ( 8); n=3, R=CHO ( 12)], and gold complexes [Au( n-CCC 6H 4R)(L)] [ n=4, R=CHO, L=PPh 3 ( 5), PMe 3 ( 6); n=4, R= CHO(CH 2) 3O , L=PPh 3 ( 9), PMe 3 ( 10); n=3, R=CHO, L=PPh 3 ( 13), PMe 3 ( 14)] have been prepared, and 9 characterized by a single crystal X-ray diffraction study. Electrochemical data for the ruthenium complexes reveal reversible or quasi-reversible (alkynyl complexes) or irreversible (vinylidene complexes) processes assigned to the Ru II/III couple; the effect on E 1/2 values of the various structural modifications across 3, 4, 7, 8, 11, 12 and 15 are discussed. The molecular quadratic and cubic optical nonlinearities of 1– 15 have been determined by the hyper-Rayleigh scattering technique at 1064 nm and the Z-scan technique at 800 nm, respectively; β values increase on increasing the acceptor strength, proceeding from 3-acceptor-substituted to 4-acceptor-substituted arylalkynyl ligand, and an increasing phosphine donor strength, whereas γ values increase on increasing the number of phosphine aryl groups (i.e. increasing delocalization) proceeding from PMe 3 to PPh 3-containing complex.