Whittall, Ian R.Humphrey, Mark G.Houbrechts, StephanMaes, JoachimPersoons, AndréSchmid, SiegbertHockless, David C.R.2026-01-012026-01-010022-328XORCID:/0000-0002-4433-6783/work/162949509https://hdl.handle.net/1885/733800004The complexes 1-(HC ≡ C)-3,5-C6H3[M]2 ([M] = trans-C ≡ CRuCl(dppm)2 (1), C ≡ CNi(PPh3)(η5-C5H5) (2)) and 1,3,5-C6H3(C ≡ CAu(PPh3))3 (3) have been prepared by extensions of well-established σ-acetylide synthetic methodologies, and 1 and 3 have been structurally characterized. Steric restrictions preclude coordination of three trans-RuCl(dppm)2 or Ni(PPh3)(η5-C5H5) moieties about the central 1,3,5-triethynylbenzene unit, a problem which the smaller Au(PPh3) group does not experience. The quadratic optical nonlinearities at 1.06 μm have been investigated by hyper-Rayleigh scattering with the C2h symmetry complexes 1 and 2 having significantly larger βHRS than their monometallic [M]C ≡ CPh ([M] = trans-RuCl(dppm)2 (4) and Ni(PPh3)(η5-C5H5) (5)) counterparts. The D3h symmetry octopolar complex 3 has a similar nonlinearity to its dipolar monometallic analogue Au(C ≡ CPh)(PPh3) (6). Complexes 1, 2 and 3 have λmax similar to 4, 5 and 6 (i.e., no loss of optical transparency is observed), but have significantly larger oscillator strengths for the important optical transitions.We thank the Australian Research Council (MGH), the Belgian Government (Grant No. IUAP-16) (AP), the Belgian National Science Foundation (Grant No. G.2103.93, 9.0012.92 and 9.0011.92) (AP) and the University of Leuven (Grant No. GOA 95/1) (AP) for support of this work, and Johnson-Matthey Technology Centre for the generous loan of ruthenium salts. I.R.W. was the recipient of an Australian Postgraduate Research Award (Industry), M.G.H. holds an ARC Australian Research Fellowship, and S.H. is a Research Assistant of the Belgian National Fund for Scientific Research.7enAcetylideAlkynylGoldNickelNonlinear opticsRutheniumSusceptibility1997-10-1710.1016/S0022-328X(97)00320-30031576284