International audienceThe 2,7-fluorenyl-bridged Fe(?5-C5Me5)(?2-dppe)[C≡C(2,7-C13H6Bu2)C≡C]Fe(?5-C5Me5)(?2-dppe) (1a), its extended analogue Fe(?5-C5Me5)(?2-dppe)[C≡C(1,4-C6H4)C≡C(2,7-C13H6Bu2)C≡C(1,4-C6H4)C≡C](?5-C5Me5)(?2-dppe)Fe (1b), and the corresponding mononuclear complexes Fe(?5-C5Me5)(?2-dppe)[C≡C(2-C13H7Bu2)] (2a) and Fe(?5-C5Me5)(?2-dppe)[C≡C(1,4-C6H4)C≡C(2-C13H7Bu2)] (2b), which model half of these molecules, have been synthesized and characterized in their various redox states. The molecular wire characteristics of the dinuclear complexes were examined in their mixed-valent states, with progression from 1a[PF6] to 1b[PF6] resulting in a sharp decrease in electronic coupling. The cubic nonlinear optical properties of these species were investigated over the visible and near-IR range, a particular emphasis being placed on their multiphoton absorption properties; the complexes are shown to function as redox-switchable nonlinear chromophores at selected wavelengths, and the more extended derivatives are shown to exhibit the more promising NLO performanc

Large increases in molecular two-photon absorption, the onset of measurable molecular three-photon absorption, and record molecular four-photon absorption in organic π-delocalizable frameworks are achieved by incorporation of bis(diphosphine)ruthenium units with alkynyl linkages. The resultant ruthenium alkynyl-containing dendrimers exhibit strong multiphoton absorption activity through the biological and telecommunications windows in the near-infrared region. The ligated ruthenium units significantly enhance solubility and introduce fully reversible redox switchability to the optical properties. Increasing the ruthenium content leads to substantial increases in multiphoton absorption properties without any loss of optical transparency. This significant improvement in multiphoton absorption performance by incorporation of the organometallic units into the organic π-framework is maintained when the relevant parameters are scaled by molecular weights or number of delocalizable π-electrons. The four-photon absorption cross-section of the most metal-rich dendrimer is an order of magnitude greater than the previous record value.

International audienceFour new mononuclear alkynyl complexes each featuring a terminal 2-fluorenyl group, namely Fe(η5-C5Me5)(CO)2[C≡C(2-C21H25)] (2), Ru(κ2-dppe)2Cl[C≡C(2-C21H25)] (3), Ru(κ2-dppe)2[C≡C(4-C6H4NO2)][C≡C(2-C21H25)] (4), and [Fe(η5-C5Me5)(κ2-dppe)_C≡C(C5H4N)-CH2(2-C13H9)_][PF6] (5[PF6]), have been synthesized and characterized, and their redox, absorption, and emission properties have been studied. For the two ruthenium derivatives 3 and 4, these studies are complemented by spectroelectrochemical investigations, Z-scan measurements, and DFT calculations. Fluorimetric studies reveal that these compounds are poorly or not luminescent, and, when luminescent, that the detected weak luminescence most likely originates from a higher lying ligand-centred (LC) excited state presumably located on fluorene. Finally, the third-order nonlinear optical (NLO) properties of 3 and 4 are reported. It is shown that the bis-alkynyl complex 4 is significantly more active than 3 and that both compounds exhibit two-photon absorption (TPA) around 860–1050 nm, with TPA cross-sections above 350 GM. In addition, it is shown that both species should give rise to a marked switching of their cubic NLO properties in this spectral range upon oxidation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

The synthesis and characterization of a set of redox-active iron and ruthenium alkynyl complexes of general formula [[M]Cl (1-p) {C≡CC 6 H 5-m (C≡CFlu) m } (1+p) ][PF 6 ] n are reported (n = 0-1; m = 1-2; [M] = [Fe(η 5-C 5 Me 5)(κ 2-dppe)] and p = 1 or [M] = [trans-Ru(κ 2-dppe) 2 ] and p = 0-1). The linear and third-order nonlinear optical properties of these new organometallic complexes featuring phenylalkynyl ligands functionalized by 2-fluorenyl (Flu) groups were studied in their stable redox states. Their first electronic transitions are assigned with the help of DFT calculations. We show here that these compounds possess significant third-order NLO responses in the near-IR range for molecules of their size. In particular, the remarkably large 2PA activities of the new Ru(II) compounds in the 600-800 nm range (Z-scan) make them attractive nonlinear chromophores. Structure-property studies emphasize the importance of para-vs. meta-connection of the 2-fluorenylethynyl units on the phenylalkynyl core, and also reveal that upon progressing from mono-to bis-alkynyl complexes, a further increase of the 2PA cross-section can be obtained while maintaining linear transparency in the visible range.

A nonametallic organometallic-coordination complex (4), assembled from redox-active ferrocenyl (Fc) and Ru( 2-dppe) 2 fragments (dppe = 1,2-bis(diphenylphosphino)ethane) as peripheral donor groups and a central Zn(II) tetraphenylporphyrin (ZnTPP) core, has been prepared and characterized. Complex 4 is obtained in one step from a pentametallic organometallic porphyrin precursor following substitution of the peripheral chloride ligands by ferrocenylalkynyl moieties (CCFc). The spectroelectrochemistry of 4, and that of previously reported porphyrins featuring related peripheral electron-rich d 6-transition metal alkynyl units, has been investigated; the optical and redox properties of 4 are briefly discussed, and its potential, and that of a related pentanuclear tetraferrocenyl ZnTPP complex, to function as redox-switchable chromophores is examined. Preliminary studies of the cubic NLO properties of 4 have been undertaken by Z-scan studies at 560 nm and 630 nm, the results from which are also reported.