Organometallic complexes for nonlinear optics, 47 - synthesis and cubic optical nonlinearity of a stilbenylethynylruthenium dendrimer.

The synthesis of the 1st generation dendrimer 1,3,5-{trans-[Ru(C≡C-3,5-(trans-[Ru(C≡CPh)(dppe)(2) (C≡CC(6) H(4) -4-(E)-CHCH)])(2) C(6) H(3) )(dppe)(2) (C≡CC(6) H(4) -4-(E)-CHCH)]}(3) C(6) H(3) proceeds by a novel route that features Emmons-Horner-Wadsworth coupling of 1,3,5-C(6) H(3) (CH(2) PO(OEt)(2) )(3) with trans-[Ru(C≡CC(6) H(4) -4-CHO)Cl(dppe)(2) ] and 1-I-C(6) H(3) -3,5-(CH(2) PO(OEt)(2) )(2) with trans-[Ru(C≡CPh)(C≡CC(6) H(4) -4-CHO)(dppe)(2) ] as key steps. The stilbenylethynylruthenium dendrimer is much more soluble than its ethynylated analog 1,3,5-{trans-[Ru(C≡C-3,5-(trans-[Ru(C≡CPh)(dppe)(2) (C≡CC(6) H(4) -4-C≡C)])(2) C(6) H(3) )(dppe)(2) (C≡CC(6) H(4) -4-C≡C)]}(3) C(6) H(3) and, in contrast to the ethynylated analog, is a two-photon absorber at telecommunications wavelengths.

Syntheses, Electrochemical, Linear Optical, and Cubic Nonlinear Optical Properties of Ruthenium-Alkynyl-Functionalized Oligo(phenylenevinylene) Stars.

The syntheses of trans-[Ru(C≡CC6 H4 -4-CHO)(C≡CC6 H4 -4-R)(dppe)2 ] (R=H (9 a), NO2 (9 b), CHO (9 c), C≡CC6 H3 -3,5-Et2 (9 d), (E)-CHCHC6 H4 -4-tBu (9 e); dppe=1,2-bis(diphenylphosphino)ethane), trans-[Ru(C≡CC6 H4 -4-R)Cl(dppe)2 ] (R=C≡CC6 H3 -3,5-Et2 (11 a), (E)-CHCHC6 H4 -4-tBu (11 b), (E)-CHCHC6 H4 -4-NO2 (11 c)), 1,2,4,5-{trans-[(dppe)2 (RC6 H4 C≡C)Ru{C≡CC6 H4 -4-(E)-CHCH}]}4 C6 H2 (R=H (14 a), C≡CC6 H3 -3,5-Et2 (14 b), (E)-CHCHC6 H4 -4-tBu (14 c)), 1-I-3,5-{trans-[(L2 )2 (R)Ru{C≡CC6 H4 -4-(E)-CHCH}]}2 C6 H3 (L2 =1,1-bis(diphenylphosphino)methane (dppm)), R=Cl (15 a); L2 =dppe, R=C≡CPh (15 b), R=C≡CC6 H4 -4-NO2 (15 c)), 1-Me3 SiC≡C-3,5-{trans-[(L2 )2 (R)Ru{C≡CC6 H4 -4-(E)-CHCH}]}2 C6 H3 (L2 =dppm, R=Cl (16 a); L2 =dppe, R=C≡CPh (16 b)), 1-HC≡C-3,5-{trans-[(dppe)2 (R)Ru{C≡CC6 H4 -4-(E)-CHCH}]}2 C6 H3 (R=Cl (17 a), R=C≡CPh (17 b)), and 1,3,5-{trans-[(dppe)2 (3,5-R2 -C6 H3 C≡C)Ru{C≡CC6 H4 -4-(E)-CHCH}]}3 C6 H3 (R=(E)-CHCHC6 H4 -4-C≡C-trans-[Ru(C≡CPh)(dppe)2 ] (18)) are reported together with those of the precursor alkynes 1-RC≡C-3,5-Et2 C6 H3 (R=SiMe3 (2), H (3), C6 H4 -4-C≡CSiMe3 (5), C6 H4 -4-C≡CH (6)). The identities of 9 c, 9 d, 9 e, 11 a, and trans-[Ru{C≡CC6 H4 -4-(E)-CHCHC6 H4 -4-tBu}2 (dppe)2 ] (12 and 12') were confirmed by single-crystal X-ray diffraction studies. The electrochemical properties of 9 a-e, 11 a-b, 14 a-c, 15 a-c, 16 b, 17 a, 17 b, and 18 were assessed by cyclic voltammetry; the studies reveal that potentials for the fully/quasi-reversible metal-centered oxidation processes decrease upon introduction of solubilizing alkyl substituents and increase upon increasing acceptor substituent strength; other structural variations have little impact. UV/Vis-NIR spectroscopic studies on these complexes reveal lowest-energy metal-ligand charge transfer (MLCT) bands that redshift upon increasing the acceptor substituent strength, blueshift on alkyl incorporation, and gain in intensity on progression from linear to star complexes. Low-temperature UV/Vis-NIR spectroelectrochemical studies of 14 a-c show the appearance of an intense low-energy band at 7400-7900 cm-1 that is redshifted upon π-system lengthening and alkyl substituent incorporation. The cubic nonlinear optical properties of 9 d, 9 e, 14 a-c, 15 a-c, 16 b, 17 a, b, and 18 were assayed by femtosecond Z-scan studies at benchmark wavelengths (750 and 800 nm) in the near-IR region, with nonlinearity increasing upon nitro incorporation; the values for the E-ene-linked dendrimers in these studies are much larger than yne-linked analogues. Compounds 9 d, 9 e, 14 a-c, and 18 were further examined by broad-spectral-range femtosecond Z-scan studies; the cruciform complexes have appreciable multiphoton absorption cross-sections, with maximal values close to two and three times the wavelength of the linear optical absorption maxima.