Linear Optical, Quadratic and Cubic Nonlinear Optical, Electrochemical, and Theoretical Studies of “Rigid‐Rod” Bis‐Alkynyl Ruthenium Complexes

Abstract

The syntheses of oligo(p‐phenylene ethynylene)s (OPEs) end‐functionalized by a nitro acceptor group and with a ligated ruthenium unit at varying locations in the OPE chain, namely, trans‐[Ru{(C≡C‐1,4‐C6H4)nNO2}(C≡CR)(dppe)2] (dppe=1,2‐bis(diphenylphosphino)ethane; n=1, R=1,4‐C6H4C≡C‐1,4‐C6H4C≡CPh, 1,4‐C6H4NEt2; n=2, R=Ph, 1,4‐C6H4C≡CPh, 1,4‐C6H4C≡C‐1,4‐C6H4C≡CPh, 1,4‐C6H4NO2, 1,4‐C6H4NEt2; n=3, R=Ph, 1,4‐C6H4C≡CPh), are reported. Their electrochemical properties were assessed by cyclic voltammetry, their linear optical properties and quadratic and cubic nonlinear optical properties were assayed by UV/Vis/NIR spectroscopy, hyper‐Rayleigh scattering studies employing nanosecond pulses at 1064 nm, and broad spectral range Z‐scan studies employing femtosecond pulses, respectively, and their linear optical properties and vibrational spectroscopic behavior in the formally RuIII state was examined by UV/Vis/NIR and IR spectroelectrochemistry, respectively. The potentials of the metal‐localized oxidation processes are sensitive to alkynyl‐ligand modification, but this effect is attenuated on π‐bridge lengthening. Computational studies employing time‐dependent density functional theory were undertaken on model complexes, with a 2D scan revealing a soft potential‐energy surface for intra‐alkynyl‐ligand aryl‐ring rotation; this is consistent with the experimentally observed blueshift in optical absorption maxima. Quadratic optical nonlinearities are significant and cubic NLO coefficients for these small complexes are small. The optimum length of the alkynyl ligands and the ideal metal location in the OPE to maximize the key coefficients have been defined.

Hybrids of gold nanoparticles and oligo(p-phenyleneethynylene)s end-functionalized with alkynylruthenium groups: Outstanding two-photon absorption in the second biological window

“…470 nm, shifting only slightly on π-bridge-lengthening (Fig. 4b) [25,35]. These results indicate that the LUMOs of 1a-3a are most likely localized on the OPE ligand, whereas the LUMOs of 1b-3b are most likely localized at the 4-nitrophenylethynyl ligand, consistent with reports for analogues [21,25,35].…”

“…S10, S16, S22 in the ESM), the singlets confirming trans configurations at the ruthenium center. The FT-IR spectra of all complexes contain a stretching vibration characteristic of the alkynyl fragment (C≡C) ligated to ruthenium in the range 2045-2058 cm -1 , consistent with the spectra of analogues [21,24,25]. A single-crystal X-ray diffraction study was undertaken on 1a, confirming its composition (Figs.…”

“…The spectra of 1a-3b display low-energy absorption bands assigned to the characteristic MLCT transitions of trans-Ru(dppe)2 bis(alkynyl) complexes (Table 2) [21,25,35]. The MLCT bands of the examples with peripheral phenyl groups red-shift on moving from the complex with one PE group (1a, λmax = 340 nm) to that with two (2a, λmax = 391nm), and then three (3a, λmax = 415 nm) (Fig.…”

DANPY (dimethylaminonaphthylpyridinium): an economical and biocompatible fluorophore

“…57 Larger organic molecules can have much higher TPA cross sections, including several carbazole derivatives engineered for combined SHG/TPEF imaging, 6 as can organometallic complexes that incorporate large, conjugated ligands with values on the order of 1000 GM. 58 In sum, the small size and simplicity, synthetic approachability, and high photostability of DANPY-1 makes it a compelling candidate for TPEF.…”

Ruthenium Alkynyl Complexes in Non-Linear Optics

“…Not surprisingly, the most efficient purely organic quadratic NLO materials are dipolar with a donor-bridgeacceptor composition, and this is also true of organometallics. The most NLO-efficient dipolar metal alkynyl complexes have generally featured an electron-rich ligated metal donor linked by an arylalkynyl bridge to an organic acceptor group, although the metal centre has also been employed in the bridge [26] and as an acceptor group. [27] With the ligated metal unit as donor in a donor-bridge-acceptor composition, trends in the key coefficient b…”