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The reactions of Q[Au(acac)2] (Q = N(PPh3)2 (PPN; a), NPr4 (b); acac = acetylacetonato) with terminal alkynes of the type HC&tbd1;CC6H4R-4 in a 1:2 molar ratio affords the complexes Q[Au(C&tbd1;CC6H4R-4)2] (R = NO2 (1), C6H4NO2-4 (2), (E)-CH&dbd;CHC6H4NO2-4 (3)). The same alkynes react with [AuCl(CNBu^t)] in NEt3 to give the complexes [Au(C&tbd1;CC6H4R-4)(CNBu^t)] (R = NO2 (4), C6H4NO2-4 (5), (E)-CH&dbd;CHC6H4NO2-4 (6)). When NHEt2 is used instead of NEt3, attack of the secondary amine at the isonitrile ligand takes place and alkynyl carbene complexes of the type [Au(C&tbd1;CC6H4R-4){C(NHBu^t)(NEt2)}] (R = NO2 (7), C6H4NO2-4 (8), (E)-CH&dbd;CHC6H4NO2-4 (9)) are obtained. The crystal structures of 1a, 4, 7, and 9 have been determined. The cubic hyperpolarizabilities of 1a,b, 4−6, 8, 9, and the related complexes [Au(C&tbd1;CC6H4R-4)(PPh3)] (R = H (10), NO2 (11), 4-C6H4NO2 (12), (E)-CH&dbd;CHC6H4NO2-4 (13), C&tbd1;CC6H4NO2-4 (14), (Z)-CH&dbd;CHC6H4NO2-4 (15), (E)-N&dbd;CHC6H4NO2-4 (16)) have been determined by Z-scans at 800 nm. An increase in γreal is observed on replacing the coligand Bu^tNC by PPh3 (proceeding from 5 to 12 and from 6 to 13), introduction of the NO2 group (proceeding from 10 to 11), extending the arylalkynyl π-bridge (proceeding from 11 to 12−15), and replacing (Z)-CH&dbd;CH by the (E)-CH&dbd;CH linking unit (proceeding from 15 to 13).

Two photon generation of carriers in anthracene has been studied using double pulses of a dye laser. The results indicate that photoionization of triplet excitons plays an important role in the photogeneration. The triplet exciton photoionization cross section is estimated to be of the order of 10-20cm2, in agreement with early results of Holzman et al.

The complexes Ni(C&tbd1;CR)(PPh3)(η-C5H5) (R = 4-C6H4NO2 (3), 4,4‘-C6H4C6H4NO2 (4), (E)-4,4‘-C6H4CH&dbd;CHC6H4NO2 (5), (Z)-4,4‘-C6H4CH&dbd;CHC6H4NO2 (6), 4,4‘-C6H4C&tbd1;CC6H4NO2 (7), 4,4‘-C6H4N&dbd;CHC6H4NO2 (8)) have been prepared. Electrochemical data for the series of complexes NiCl(PPh3)(η-C5H5) (1), Ni(C&tbd1;CPh)(PPh3)(η-C5H5) (2), and 3−8 have been determined. Introduction of nitro substituent (in progressing from 2 to 3) results in a substantial increase in the Ni^II/III oxidation potential, all of which is lost on progressing from a one-ring (3) to two-ring (4−8) chromophore. The molecular quadratic and cubic optical nonlinearities of the series of complexes have been determined by hyper-Rayleigh scattering (HRS) and Z-scan techniques, respectively. HRS measurements at 1064 nm are consistent with an increase in β upon chromophore chain-lengthening (in progressing from 3 to 7 to 5), replacing Z by E stereochemistry (in progressing from 6 to 5), and in replacing N by CH (in progressing from 8 to 5), general trends that are maintained with the two-level-corrected data. Nonlinearities for the 18-electron nickel complexes are larger than those for related 14-electron (triphenylphosphine)gold acetylides, but smaller than those for the more easily oxidizable 18-electron (cyclopentadienyl)bis(phosphine)ruthenium acetylide analogues. Z-scan data at 800 nm reveal a negative γ for the nitro-containing complexes, consistent with the dispersion effect of two-photon states contributing to the nonlinearities. An increase in γ upon chromophore chain-lengthening (in progressing from 3 to 5, 4 and 7) and replacing Z by E stereochemistry (in progressing from 6 to 5) is observed. Nonlinearities for the extended-chromophore acetylide complexes 5 and 7 are significantly less than those for the (triphenylphosphine)gold acetylide analogues.

A novel series of highly soluble distyrylbenzenes bearing poly(alkyleneoxy) and/or alkylsulfonyl solubilizing substituents has been synthesized using the stereoselective Wadsworth–Emmons reaction as a key step. The corresponding poly(alkyleneoxy) alkylsulfonyl 4,4′-disubstituted distyrylbenzene has been covalently incorporated into an acrylic monomer which has also been successfully co-polymerized with methyl methacrylate (MMA). All the 4,4′-disubstituted distyrylbenzenes and the polyacrylate based co-polymer show excellent solubility, processibility and thermal stability. Importantly, 2-(2-butoxyethoxy)ethoxy-hexylsulfonyl 4,4′-disubstituted distyrylbenzene exhibits only a minor bathochromic shift of the absorption maximum compared to those of the corresponding symmetrically 4,4′-disubstituted distyrylbenzenes; however, its third-order optical nonlinearity derived from Z-scan measurements at 800 nm is approximately twice as large as those of its symmetrically 4,4′-disubstituted counterparts.

Poly(p-phenylenevinylene) (PPV) has been incorporated into sol−gel matrixes via its soluble precursor polymer, using tetramethoxysilane (TMOS) and methyltrimethoxysilane (MTMS) as the silane monomers. Linear absorption maximum (λmax) and nonlinear refractive index n2 of the PPV in the two composite systems were compared and studied. Compared to pristine PPV, a reduction was seen in λmax and |n2| of the composite films. This paper addresses chemical and processing effects directed at minimising this matrix-induced reduction in λmax and |n2|. Of the parameters studied, the nature of the silane monomer has the greatest influence on the λmax and |n2| values of the composites. The reduction of the λmax and |n2| values in the composite films was much greater when TMOS was the matrix host. There is a smaller decrease in both |n2| and λmax if acid catalysis is used during either the sol synthesis or during the thermal transformation process, but this effect is marginal for TMOS. A differential matrix effect on λmax and |n2| is also seen in the temperature required for the conversion to PPV within the respective matrixes.

Quadratic nonlinearities for octopolar stilbenylruthenium complexes are large for compounds without strongly accepting substituents. Cubic nonlinearities |γ|800 and two-photon absorption cross-sections σ2 increase on “dimensional evolution” from linear analogues to octopolar complexes, the latter possessing some of the largest |γ|800 and σ2 values for organometallics thus far, while cubic nonlinearities Im(χ⁽³⁾)/N from the first application of electroabsorption spectroscopy to organometallics are also large, scaling with the number of metal atoms.

The molecular inorganic compounds 1,3,5-{trans-[RuCl(dppe)2]C&tbd1;C-4-C6H4C&tbd1;C}3C6H3 (1), trans-[Ru(C&tbd1;C-4-C6H4C&tbd1;CPh)Cl(dppe)2] (2), and trans-[Ru(C&tbd1;CPh)Cl(dppm)2] (3) exhibit reversible oxidation in solution, assigned to the metal-centered Ru^II/III processes. Complexes 1−3 are essentially transparent at frequencies below 20 × 10³ cm^-1, whereas the green complexes 1⁺−3⁺ have a strong absorption band centered near 11−12 × 10³ cm^-1. These absorption bands have been utilized to demonstrate facile NLO switching utilizing an optically transparent thin-layer electrochemical cell, a procedure which has applicability to evaluating the switching capability of a range of materials. This procedure has been applied to switch cubic nonlinearities, the first electrochromic switching of molecular nonlinear absorption. Oxidation of the molecules results in changes, including changes of sign, of both the imaginary (absorptive) part of the third-order nonlinearity and the real (refractive) part. Cycling between the two forms of the molecules is facile. The sign of the nonlinearity is reversed on oxidation of 1 and 2, whereas 3, a complex with negligible third-order nonlinearity in the resting state, has third-order nonlinearity switched on upon oxidation to 3⁺.

A soluble, oxidatively and thermally very stable alkynylruthenium dendrimer 1,3,5-C6H3(4-C&tbd1;CC6H4C&tbd1;C-trans-[Ru(dppe)2]C&tbd1;C-3,5-C6H3-{4-C&tbd1;CC6H4C&tbd1;C-trans-[Ru(C&tbd1;CPh)(dppe)2]}2)3, containing a large two-dimensional π-delocalized system, has been prepared using an experimentally straightforward convergent synthetic approach. The first third-order nonlinear optical (NLO) measurements of an organometallic dendrimer have been obtained using the Z-scan technique at a wavelength of 800 nm. Progression from 1,3,5-C6H3(4-C&tbd1;CC6H4C&tbd1;C-trans-[Ru(dppe)2]C&tbd1;CPh)3 to the dendrimer results in (i) no loss of optical transparency, (ii) an increase in the second hyperpolarizability, γ, which is proportionately greater than either the increase in the number of phenylethynyl groups or the extinction coefficient for the important MLCT band, and (iii) a dramatic enhancement of two-photon absorption.

Charge carrier generation through photexcitation with strongly absorbed light and very weakly absorbed light has been compared for anthracene and phenazine crystals. No attempt was made to prepare clean surfaces, but purified crystals were used. The field dependence for strongly absorbed light was similar for both crystals, superlinear at low fields, linear at high fields. For weakly absorbed light, the photo generation of charge in anthracene could be described as Onsager type behavior, generation in phenazine could not. These results are discussed in terms of the charge generation process.