Search

The syntheses of trans-[Ru(C≡CC6H4-4-CHO)(C≡CC6H4-4-R)(dppe)2] (R=H (9 a), NO2 (9 b), CHO (9 c), C≡CC6H3-3,5-Et2 (9 d), (E)-CHCHC6H4-4-tBu (9 e); dppe=1,2-bis(diphenylphosphino)ethane), trans-[Ru(C≡CC6H4-4-R)Cl(dppe)2] (R=C≡CC6H3-3,5-Et2 (11 a), (E)-CHCHC6H4-4-tBu (11 b), (E)-CHCHC6H4-4-NO2 (11 c)), 1,2,4,5-{trans-[(dppe)2(RC6H4C≡C)Ru{C≡CC6H4-4-(E)-CHCH}]}4C6H2 (R=H (14 a), C≡CC6H3-3,5-Et2 (14 b), (E)-CHCHC6H4-4-tBu (14 c)), 1-I-3,5-{trans-[(L2)2(R)Ru{C≡CC6H4-4-(E)-CHCH}]}2C6H3 (L2=1,1-bis(diphenylphosphino)methane (dppm)), R=Cl (15 a); L2=dppe, R=C≡CPh (15 b), R=C≡CC6H4-4-NO2 (15 c)), 1-Me3SiC≡C-3,5-{trans-[(L2)2(R)Ru{C≡CC6H4-4-(E)-CHCH}]}2C6H3 (L2=dppm, R=Cl (16 a); L2=dppe, R=C≡CPh (16 b)), 1-HC≡C-3,5-{trans-[(dppe)2(R)Ru{C≡CC6H4-4-(E)-CHCH}]}2C6H3 (R=Cl (17 a), R=C≡CPh (17 b)), and 1,3,5-{trans-[(dppe)2(3,5-R2-C6H3C≡C)Ru{C≡CC6H4-4-(E)-CHCH}]}3C6H3 (R=(E)-CHCHC6H4-4-C≡C-trans-[Ru(C≡CPh)(dppe)2] (18)) are reported together with those of the precursor alkynes 1-RC≡C-3,5-Et2C6H3 (R=SiMe3 (2), H (3), C6H4-4-C≡CSiMe3 (5), C6H4-4-C≡CH (6)). The identities of 9 c, 9 d, 9 e, 11 a, and trans-[Ru{C≡CC6H4-4-(E)-CHCHC6H4-4-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.

The wavelength dependence of the cubic nonlinearity of ligated platinum-terminated polyynes trans, trans-{(p-MeC6H4)3P}2(p-MeC6H4)Pt(C[triple bond]C)n Pt(p-C6H4Me){P(p-C6H4Me)3}2 (n = 3-6, 8, 10, 12) has been examined by femtosecond Z-scan studies in the wavelength range 520-1500 nm and the results rationalized by density functional theory calculations on the model complexes trans, trans-(H3P)2(C6H5)Pt(C[triple bond]C)n Pt(C6H5)(PH3)2 (n = 2-8, 10, 12). Although the final states for one- and two-photon transitions are not the same in these centrosymmetric molecules, the Z-scan studies reveal coincidences in one-photon absorption with features in the frequency dependencies of both real and imaginary parts of the cubic hyperpolarizability, as well as inflections in the frequency dependencies of the real part of gamma that correspond to resonances in the imaginary part of gamma. The theoretical studies suggest that the linear absorption spectra are dominated by X(1)A g --n(1)B(3u) transitions, with the first state of B(3u) symmetry playing a steadily diminishing role upon oligoyne chain lengthening. The theoretical studies also predict a red-shift of two-photon absorption (TPA) profile with increasing conjugation length, and a significant enhancement on proceeding from the shortest to the longest chromophore, trends that are observed experimentally. The experimental low-energy TPA maxima for these complexes can be approximated by a simple Gaussian profile. The sp-carbon chain-length dependence of linear and nonlinear absorption maxima enable an estimate (neglecting saturation) of 660 and 1000 nm for the infinite carbon chain, carbyne.

Reactions of the tetrahedral clusters MoIr3(μ-CO)3(CO)8(η-L) (L = C5HMe4, C5Me5) with the carbonylmetalate anions [Mo(CO)3(η-L)]- afford the trigonal bipyramidal clusters Mo2Ir3(μ3-H)(μ-CO)2(CO)9(η...

Reaction of WH(CO) 3 (η-C 5 Me 5 ) with IrCl(CO) 2 (4-H 2 NC 6 H 4 Me) affords WIr 3 (μ-CO) 3 (CO) 8 (η-C 5 Me 5 ) in low yield. A structural study reveals a WIr 2 -centred plane of bridging carbonyls, in contrast to the crystal structure of WIr 3 (CO) 1 1 (η-C 5 H 5 ) (all-terminal carbonyl distribution). DFT calculations reveal an increasing proclivity to adopt an all-terminal CO disposition for clusters MIr 3 (CO) 1 1 (η-C 5 H 5 ) in the gas phase on proceeding from M =Cr to Mo and then W, consistent with structural studies in the solid state for which the tungsten-containing cluster is the only all-terminal example. Increasing electron donation from the ligands in the tungsten system (either from phosphine substitution or cyclopentadienyl permethylation) suffices to impose a plane of bridging carbonyls in the ground state structure. 1 3 C NMR fluxionality studies reveal that CO exchange mechanism(s) for WIr 3 (CO) 1 1 (η-C 5 H 5 ) and the related tetrahedral cluster W 2 Ir 2 (CO) 1 0 (η-C 5 H 5 ) 2 are very fast and involve all carbonyls on the clusters. DFT calculations on MIr 3 (CO) 1 1 (η-C 5 H 5 ) (M=Cr, Mo) substantiate a 'merry-go-round' mechanism for carbonyl scrambling in these systems, a result which is consistent with the scrambling behaviour seen in the NMR fluxionality studies on the W-containing congener.

A combination of UV-vis-NIR spectroscopy, femtosecond Z-scan measurements, and time-dependent density functional theory (TD-DFT) calculations have been used to comprehensively investigate the linear optical and nonlinear optical (NLO) properties of pi-delocalizable metal-functionalized oligo(phenyleneethynylene)s. A range of unsymmetrically or symmetrically end-functionalized mono-, di-, tri-, penta-, hepta-, and nona(phenyleneethynylene)s were synthesized, with larger examples bearing varying numbers of 2,5-di(hexyloxy)phenyl groups to ensure sufficient solubility of the metal complex derivatives. The effect of incorporating varying numbers of solubilizing substituents in the OPE bridge, peripheral group modification, OPE lengthening, coligand variation, and metal location in the OPE on the linear optical properties has been established, with the first three molecular modifications resulting in significant changes in the optical absorption maxima. TD-DFT calculations reveal that the most intense transition in the linear optical spectra is localized on the OPE bridge and involves excitation from acetylenic to cumulenic molecular orbitals that are not greatly spatially separated from one another. The nonlinear optical properties are dominated by two-photon absorption, which for all but 1,4-{trans-[RuCl(dppm)(2)]C[triple bond]C}(2)C(6)H(4) appears as a band around 11,400 cm(-1) and a sharp increase of nonlinear absorption at frequencies17,000 cm(-1). Surprisingly, there is relatively little influence of the length of the OPE bridge on the magnitude of the two-photon absorption cross sections, which are in the range 300-1000 GM.

Lewis addition between the metalloligand [RuCp(C[triple bond]Cpy-4)(dppf)] (1) (dppf = (C(5)H(4)PPh(2))(2)Fe) and MCl(2)(CH(3)CN)(2) gives [RuCp(C[triple bond]Cpy-4)(dppf)](2)[MCl(2)] (M = Pd (2) and Pt (3)), all of which have been spectroscopically and crystallographically characterized. The mixed-metal adducts show the d(6)-d(8)-d(6) metal alignment maintained by the trans disposition of the directionally rigid 4-ethynylpyridine at the centrosymmetric square-planar metal center. Electrochemical studies of these and the related known complexes trans-[RuCl(C[triple bond]Cpy-4)(dppm)(2)] (4) and [trans-RuCl(C[triple bond]Cpy-4)(dppm)(2)](2)[MCl(2)] (dppm = Ph(2)PCH(2)PPh(2)) (M = Pd (5) and Pt (6)) suggest that the spacer-linked heterotrinuclear network is able to stabilize the oxidized Ru(III) better than the metalloligand precursor. Cubic nonlinear optical responses are also generally higher for the heterometallic complexes. The gamma(real) value of the PdRu(2) dppm complex 5 is among the largest for linear organometallic complexes.

Publisher Summary This chapter describes the structure and nonlinear optical (NLO) property relationships for organometallic systems. Both quadratic and cubic molecular nonlinearities obtained for specific complexes are extremely large, suggesting that the potential for application of organometallics still remains. The most popular complexes subjected to NLO study are ferrocenyl and alkynyl complexes—reassuring that these are the most stable of organometallics, thereby satisfying an important materials requirement for putative applications. NLO behavior arises from the interaction of electromagnetic fields with matter. The consequent generation of new field components (differing in amplitude, phase, frequency, path, polarization, etc.) is of enormous technological importance for optical devices, with potential applications in data storage, communication, switching, image processing, and computing. These applications have generated a need for materials with exceptional NLO properties and satisfactory materials properties (processing, stability, etc.). Two unit systems are commonly employed in describing NLO properties: the SI (MKS) and the Gaussian (cgs) systems. This chapter describes a number of popular techniques used for the measurement of second- and third-order NLO properties of organometallic molecules.

There is much interest in nonlinear absorbing chromophores for applications in photonics, nanophotonics and biophotonics. We have performed studies of dispersion of the nonlinear absorption cross sections and the refractive nonlinearities of organic and organometallic nonlinear chromophores using the technique of Z-scan, with a tunable amplified femtosecond laser system. Z-scan is less sensitive than the popular technique of two-photon induced fluorescence but has advantages of being suitable for non-fluorescent substances and providing information on both absorptive and refractive nonlinearities. We have analysed the experimental results in terms of simple models and using the Kramers-Kronig transformation as shown in this paper for Coumarine 307 and an organometallic dendrimer. The dispersion curves are often dominated by two-photon resonances but inclusion of other nonlinear mechanisms seems to be necessary for better understanding of their features.

The linear (absorption and emission) and nonlinear optical (NLO) properties of a series of D(3) [(Fe(II), Ru(II), Ni(II), Cu(II), Zn(II)] octupolar metal complexes featuring the 4,4'-bis[(dibutylamino)styryl]-2,2'-bipyridine ligand are reported. Zinc(II), nickel(II), and copper(II) complexes exhibit similar absorption spectra in the visible region (lambda(ILCT) = 474-476 nm) which are assigned to intraligand charge-transfer (ILCT) bands. The quadratic and cubic NLO properties are strongly influenced by the nature of the metallic center. Harmonic light scattering studies at lambda = 1.91 microm reveal that these chromophores display large first hyperpolarizabilities beta(1.91) in the range of (211-340) x 10(-30) esu; replacing the Zn(II) metal ion by Ni(II) or Cu(II) results in a decrease of the static beta(0) coefficient by a factor of 1.5-1.6. Z-scan measurements at 765 and 965 nm reveal relatively large two-photon absorption cross-sections [650sigma(2)2200 GM], showing that both beta and sigma(2) values can be tuned by simple modification of the metal ion.

Publisher Summary This chapter describes the structure and nonlinear optical (NLO) property relationships for organometallic systems. Both quadratic and cubic molecular nonlinearities obtained for specific complexes are extremely large, suggesting that the potential for application of organometallics still remains. The most popular complexes subjected to NLO study are ferrocenyl and alkynyl complexes—reassuring that these are the most stable of organometallics, thereby satisfying an important materials requirement for putative applications. NLO behavior arises from the interaction of electromagnetic fields with matter. The consequent generation of new field components (differing in amplitude, phase, frequency, path, polarization, etc.) is of enormous technological importance for optical devices, with potential applications in data storage, communication, switching, image processing, and computing. These applications have generated a need for materials with exceptional NLO properties and satisfactory materials properties (processing, stability, etc.). Two unit systems are commonly employed in describing NLO properties: the SI (MKS) and the Gaussian (cgs) systems. This chapter describes a number of popular techniques used for the measurement of second- and third-order NLO properties of organometallic molecules.

The NLO properties of iron, ruthenium, osmium, nickel, and gold alkynyl complexes and some related compounds prepared in the authors’ laboratories are reviewed. Structure-property relationships for both quadratic and cubic NLO merit for these complexes have been developed from hyper-Rayleigh scattering studies at 1.064μm and Z-scan studies at 0.800μ m, respectively

Reaction of [WIr3(mu-CO)3(CO)8(eta-C5Me5)] (1c) with [W(C[triple bond]CPh)(CO)3(eta-C5H5)] afforded the edge-bridged tetrahedral cluster [W2Ir3(mu4-eta2-C2Ph)(mu-CO)(CO)9(eta-C5H5)(eta-C5Me5)] (3) and the edge-bridged trigonal-bipyramidal cluster [W3Ir3(mu4-eta2-C2Ph)(mu-eta2-C=CHPh)(Cl)(CO)8(eta-C5Me5)(eta-C5H5)2] (4) in poor to fair yield. Cluster 3 forms by insertion of [W(C[triple bond]CPh)(CO)3(eta-C5H5)] into Ir-Ir and W-Ir bonds, accompanied by a change in coordination mode from a terminally bonded alkynyl to a mu4-eta2 alkynyl ligand. Cluster 4 contains an alkynyl ligand interacting with two iridium atoms and two tungsten atoms in a mu4-eta2 fashion, as well as a vinylidene ligand bridging a W-W bond. Reaction of [WIr3(CO)11(eta-C5H5)] (1a) or 1c with [(eta-C5H5)(CO)2 Ru(C[triple bond]C)Ru(CO)2(eta-C5H5)] afforded [Ru2WIr3(mu5-eta2-C2)(mu-CO)3(CO)7(eta-C5H5)2(eta-C5R5)] [R = H (5a), Me (5c)] in low yield, a structural study of 5a revealing a WIr3 butterfly core capped and spiked by Ru atoms; the diruthenium ethyndiyl precursor has undergone Ru-C scission, with insertion of the C2 unit into a W-Ir bond of the cluster precursor. Reaction of [W2Ir2(CO)10(eta-C5H5)2] with the diruthenium ethyndiyl reagent gave [RuW2Ir2{mu4-eta2-(C2C[triple bond]C)Ru(CO)2(eta-C5H5)}(mu-CO)2(CO)6(eta-C5H5)3] (6) in low yield, a structural study of 6 revealing a butterfly W2Ir2 unit capped by a Ru(eta-C5H5) group resulting from Ru-C scission; the terminal C2 of a new ruthenium-bound butadiyndiyl ligand has been inserted into the W-Ir bond. Reaction between 1a, [WIr3(CO)11(eta-C5H4Me)] (1b), or 1c and [(eta-C5H5)(CO)3W(C[triple bond]CC[triple bond]C)W(CO)3(eta-C5H5)] afforded [W2Ir3{mu4-eta2-(C2C[triple bond]C)W(CO)3(eta-C5H5)}(mu-CO)2(CO)2(eta-C5H5)(eta-C5R5)] [R = H (7a), Me (7c); R5 = H4Me (7b)] in good yield, a structural study of 7c revealing it to be a metallaethynyl analogue of 3.

The quadrupolar ruthenium alkynyl cruciform complex is reversibly converted to tetravinylidene complex or tetraruthenium(III) tetracationic complex forms by protonation or oxidation, respectively; linear and nonlinear proto- and electrochromism studies reveal independent switching of NLO properties by the protic and electrochemical stimuli, respectively, aspects of which have been rationalized by theoretical studies.

The title compound, [RuCl(C25H22P2)2(H2O)]PF6·1.73CH4O, contains a pseudo-octahedral ruthenium complex cation with two bidentate diphosphine ligands and cis-disposed chloro and aqua ligands, together with a disordered hexa­fluoro­phosphate anion and disordered methanol solvent mol­ecules. Identification as an aqua­ruthenium(II) complex rather than a hydroxo­ruthenium(III) complex was confirmed by cyclic voltammetry.