Photoswitchable Arylazopyrazole-Based Ruthenium(II) Arene Complexes

A new family of donor-functionalized photoswitchable arylazopyrazole-based ligands (<b>3</b>–<b>5</b>) was synthesized and characterized. The new ligands have been employed to prepare a series of novel photoswitchable half-sandwich ruthenium­(II) cymene complexes of the type [(η⁶-<i>p</i>-cymene)­Ru­(L)­Cl]⁺ (L = 1-(2-methylenepyridyl)-4-(phenyldiazenyl)-3,5-dimethyl-1<i>H</i>-pyrazole (<b>6a</b>), 1-(2-methylenepyridyl)-4-((4-bromophenyl)­diazenyl)-3,5-dimethyl-1<i>H</i>-pyrazole (<b>6b</b>), 1-(2-benzothiazolyl)-3,5-dimethyl-4-arylazopyrazole (<b>7</b>)). All of the complexes have been fully characterized by ¹H NMR, ¹³C NMR, and UV–vis spectroscopy and elemental analyses. In addition, the structure of complex <b>6a</b> was determined by X-ray crystallography. The UV–vis spectroscopic studies show that both the ligands and metal complexes exhibit excellent trans to cis photoisomerization of the arylazopyrazole moiety upon irradiation with 365 nm UV light. The cis isomer of the compounds can be switched back nearly quantitatively to the more stable trans form with 530 nm irradiation. Coordination of the metal ion has no significant influence on the photoswitching properties of the ligands. DFT and TD-DFT calculations were performed for geometry optimization of the ligands and to complement the experimental findings of the electronic transitions and absorption bands observed. The data obtained from these studies were in good agreement with the experimental results. These excellent photoswitchable properties make the new cationic Ru­(II) azo compounds described in these studies interesting candidates for their potential application as photoswitchable systems in catalytic and medicinal chemistry

A Study of Wave Confinement and Optical Force in Polydimethlysiloxane&ndash;Arylazopyrazole Composite for Photonic Applications

A refractive index of dielectrics was modified by several methods and was known to have direct influence on optical forces in nanophotonic structures. The present contribution shows that isomerization of photoswitching molecules can be used to regulate refractive index of dielectrics in-situ. In particular, spectroscopic study of a polydimethylsiloxane&ndash;arylazopyrazole (PDMS&ndash;AAP) composite revealed that refractive index of the composite shifts from 2.0 to 1.65 in trans and cis states, respectively, of the embedded AAP. Based on this, a proposition is made for a waveguide structure, in which external UV/Vis source reversibly regulates the conformation of the PDMS&ndash;AAP core. Computational study is performed using Maxwell&rsquo;s equations on buried waveguide structure. The simulation, implemented in PYTHON, sequentially utilizes empirical refractive indices of the composite in the isomeric states in lieu of regulation by a source. The simulation revealed highly confined wave propagations for injected signals of 340 and 450 nm wavelengths. It is observed that the cis state suppresses higher order mode when propagating UV wavelength but allows it for visible light. This modal tuning demonstrated that single mode can be selectively excited with appropriate waveguide dimensions. Further impact of the tuning is seen in the optical force between waveguide pair where the forces shift between attractive and repulsive in relation to the isomeric state of the PDMS&ndash;AAP core. These effects which stem from the adjustment of refractive index by photoisomerization suggests that in-situ regulation of index is achievable by successful integration of photoswitching molecules in host materials, and the current PDMS&ndash;AAP composites investigated in this study can potentially enhance nanophotonic and opto-mechanical platforms

Synthesis and characterization of [( η 6 -arene)RuCl 2 (R 2 AsCH=CH 2 )] and tethered arsinopropylarene�ruthenium(II) complexes.

The complexes [(η6-arene)RuCl2(R2AsCH=CH2)] [arene = MeC6H5, R = Ph (1a), R = Cy (1b); p-MeC6H4Me, R = Ph (2a), R = Cy (2b); o-MeC6H4Me, R = Ph (3a), R = Cy (3b); 1,3,5-Me3C6H3, R = Ph (4a); p-MeC6H4CHMe2, R = Ph (5a), R = Cy (5b); 1,2,4,5-Me4C6H2, R =

Isomerization-hydroboration-oxidation strategy: Access to long chain AB- and AA-type oleyl based monomers and polymers thereof

A strategy to convert by isomerization-hydroboration-oxidation reaction the internal double bond of oleic acid to a terminal alcohol function, leading to linear long-chain ,-difunctional substrates has been investigated. Using this strategy, oleic acid-based AB- and AA-monomers were prepared and characterized by FTIR-ATR and NMR spectroscopy. Thermoplastic aliphatic linear polyesters, polycarbonates, and polyurethanes were then synthesized by reacting the so-formed bio-based monomers via polycondensation in bulk, using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as an organocatalyst. Thus, starting from easily available bio-based starting compound, the synthesis of linear long methylene chain aliphatic polyesters, polycarbonates, and polyurethanes (by isocyanate free route) is reported. The structural and thermal characterizations of the synthesized polymers were performed by means of NMR, SEC, DSC, and TGA experiments