The Design, Syntheses, and Photophysics of Novel Pt(II) Polypyridyl Arylacetylides and Arylthiolates

Herein, the approach towards the modulation of the distinct excited states in Pt(¿¿¿¿¿¿¿¿¿¿) complexes through careful consideration of the nature of the coordination sphere and solvent environment was successfully realized. The developed variety of Pt(¿¿¿¿¿¿¿¿¿¿) polypyridyl arylacetylide complexes possessed the desired dark and emissive charge-transfer or ligand-localized excited states, depending on the nature of ligands. The photophysical properties were studied in detail by UV-Vis absorption spectroscopy, steady-state and time resolved photoluminescence methods (gate pulsing, pulse sampling, and time-correlated single photon counting) in the solutions and glasses. The excited states of compounds, lacking emission from their lowest triplet state, were effectively studied using nanosecond transient absorption spectroscopy together with time-resolved step-scan FT-IR. The analogous DFT calculations showed an excellent agreement with experiment and provided the insights into the frontier orbitals and ultimately the origins of the vibrations in the ground and excited states. Additionally, the bidentate coordination of terpyridyl in Pt(¿¿¿¿¿¿¿¿¿¿) arylthiolates was studied by the array of static and dynamic spectroscopic methods in combination with electrochemistry. The resulting data unveiled that the Pt(II) terpyridyl bisarylthoilates, where terpyridyl acts as a bidentate chelate, resembles charge-transfer photophysics of Pt(II) bipyridyl arylthiolate rather than Pt(II) terpyridyl arythiolate, where terpyridyl acts as tridentate ligand. The fine control of the rich photophysical properties of the reported Pt(II) polypyridyl complexes makes them good candidates for a variety of applications, especially in energy related areas

The Design, Syntheses, and Photophysics of Novel Pt(II) Polypyridyl Arylacetylides and Arylthiolates

Herein, the approach towards the modulation of the distinct excited states in Pt(¿¿¿¿¿¿¿¿¿¿) complexes through careful consideration of the nature of the coordination sphere and solvent environment was successfully realized. The developed variety of Pt(¿¿¿¿¿¿¿¿¿¿) polypyridyl arylacetylide complexes possessed the desired dark and emissive charge-transfer or ligand-localized excited states, depending on the nature of ligands. The photophysical properties were studied in detail by UV-Vis absorption spectroscopy, steady-state and time resolved photoluminescence methods (gate pulsing, pulse sampling, and time-correlated single photon counting) in the solutions and glasses. The excited states of compounds, lacking emission from their lowest triplet state, were effectively studied using nanosecond transient absorption spectroscopy together with time-resolved step-scan FT-IR. The analogous DFT calculations showed an excellent agreement with experiment and provided the insights into the frontier orbitals and ultimately the origins of the vibrations in the ground and excited states. Additionally, the bidentate coordination of terpyridyl in Pt(¿¿¿¿¿¿¿¿¿¿) arylthiolates was studied by the array of static and dynamic spectroscopic methods in combination with electrochemistry. The resulting data unveiled that the Pt(II) terpyridyl bisarylthoilates, where terpyridyl acts as a bidentate chelate, resembles charge-transfer photophysics of Pt(II) bipyridyl arylthiolate rather than Pt(II) terpyridyl arythiolate, where terpyridyl acts as tridentate ligand. The fine control of the rich photophysical properties of the reported Pt(II) polypyridyl complexes makes them good candidates for a variety of applications, especially in energy related areas

Ligand-Localized Triplet-State Photophysics in a Platinum(II) Terpyridyl Perylenediimideacetylide

The synthesis, electrochemistry, and photophysical behavior of a Pt­(II) terpyridyl perylenediimide (PDI) acetylide (<b>1</b>) charge-transfer complex is reported. The title compound exhibits strong (ε ≈ 5 × 10⁴ M^–1cm^–1) low-energy PDI acetylide-based π–π* absorption bands in the visible range extending to 600 nm, producing highly quenched singlet fluorescence (Φ = 0.014 ± 0.001, τ = 109 ps) with respect to a nonmetalated PDI model chromophore. Nanosecond transient absorption spectroscopy revealed the presence of a long excited-state lifetime (372 ns in 2-methyltetrahydrofuran) with transient features consistent with the PDI–acetylide triplet state, ascertained by direct comparison to a model Pt­(II) PDI–acetylide complex lacking low-energy charge-transfer transitions. For the first time, time-resolved step–scan FT-IR spectroscopy was used to characterize the triplet excited state of the PDI–acetylide sensitized in the title compound and its associated model complex. The observed red shifts (∼30–50 cm^–1) in the CO and CC vibrations of the two Pt­(II) complexes in the long-lived excited state are consistent with formation of the ³PDI acetylide state and found to be in excellent agreement with the expected change in the relevant DFT-calculated IR frequencies in the nonmetalated PDI model chromophore (ground singlet state and lowest triplet excited state). Formation of the PDI triplet excited state in the title chromophore was also supported by sensitization of the singlet oxygen photoluminescence centered at ∼1275 nm in air-saturated acetonitrile solution, Φ­(¹O₂) = 0.52. In terms of light emission, only residual PDI-based red fluorescence could be detected and no corresponding PDI-based phosphorescence was observed in the visible or NIR region at 298 or 77 K in the Pt­(II) terpyridyl perylenediimideacetylide

Sol-gel derived oriented multilayer ZnO thin films with memristive response

Abstract Sol-gel derived multi-layer ZnO films were prepared by spin coating technique on soda-lime glass, silica, silicon and platinum substrates from an alcoholic solution of zinc acetate dihydrate and monoethanolamine at different synthetic conditions. The curing and annealing conditions for the ZnO films were adjusted based on the study performed on the ZnO xerogel powders. Structural and morphological features as well as the thermal behavior of the samples were investigated by complementary techniques including electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analyses, and X-ray diffraction analysis. According to the electrical measurements performed on ZnO thin films sandwiched between Pt/Ti/SiO2 substrate and Ag dishes as a top electrode, the selected fabrication conditions were suitable for fulfilling the requirements of active resistive layers for the development of memristive devices

Development of microfabrication technologies enabling the realization of memristor-based devices and building blocks for logic circuits

By an innovative approach combining material research and novel hardware design , a prototype of memristive device has been realized. The aim of the reported activity herein, was to identify simple and low cost fabrication processes for the development of the memristive cell

Excited-state properties of heteroleptic iridium(III) complexes bearing aromatic hydrocarbons with extended cores

The synthesis, complete structural characterization, electrochemistry, and excited-state dynamics of a series of four bis-heteroleptic iridium(III) charge-transfer complexes composed of a single acac-functionalized and two ortho-metalated 2-phenylpyridine ligands. The formed iodophenyl complex (2) was used as a metallosynthon to introduce extended-core ethynyltolyl (3), ethynylpyrene (4), and ethynylperylene (5) residues into these structures projecting from the acac ancillary ligand. Static and dynamic photoluminescence along with ultrafast and conventional transient absorption measurements in conjunction with cyclic voltammetry were employed to elucidate the nature of the intramolecular energy-transfer processes occurring in the excited states of polychromophores 4 and 5 and are directly compared with those of model complexes 2 and 3. Upon charge-transfer excitation of these molecules, the long-lived triplet-state metal-to-ligand charge-transfer ((3)MLCT)-based photoluminescence readily observed in 2 and 3 (τ = 1 μs) is nearly quantitatively quenched, resulting from production of the associated triplet intraligand ((3)IL) excited states in 4 and 5 through intramolecular triplet-triplet energy transfer. The respective formation of the extended-core (3)*pyrenyl and (3)*perylenyl-localized excited states in 4 and 5 is confirmed by their ultrafast excited-state evolution, which ultimately generates features associated with these (3)IL excited states and their greatly extended excited-state lifetimes with respect to the parent complexes 2 and 3

Towards low voltage resistive switch in sol-gel derived TiO2/Ta2O5 stack thin films

Herein, we report a memristive response from Pt/TiO2/Ta2O5/Pt stack thin films with low SET and RESET voltages, and resistance ratio of 103. For the first time, Pt/TiO2/Ta2O5 stack thin films were produced by sol-gel procedure. The morphology and elemental composition of Pt/TiO2/Ta2O5 stacks were studied by a set of complementary techniques, including scanning electron microscopy (SEM), field-emission electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The thickness of the material was estimated from the transmittance spectrum by Pointwise Unconstrained Optimization Approach (PUMA)

Structural Refinement of Ladder-Type Perylenediimide Dimers: A Classical Tale of Conformational Dynamics

We have synthesized and thoroughly characterized two representative ladder-type acetylene-bridged perylenediimide dimers bearing long alkyl chain solubilizing groups, bis­[1-ethynyl-<i>N</i>,<i>N</i>′-bis­(1-hexylheptyl)-perylene-3,4:9,10-tetracarboxylic diimide] ([PDICC]₂, <b>1</b>) and 1,1′-ethynyl-bis­[<i>N</i>,<i>N</i>′-bis­(1-hexylheptyl)-perylene-3,4:9,10-tetracarboxylic diimide] ([PDI]₂CC, <b>2</b>). In these dimeric PDI molecules, NMR-based structural characterization became nontrivial because severe ¹H spectral broadening and greater than expected numbers of observed ¹³C resonances substantially complicated the interpretation of traditional 1-D spectra. However, rational two-dimensional NMR approaches based on both homo- and heteronuclear couplings (¹H–¹H COSY; ¹H–¹³C HSQC), in conjunction with high-level structural DFT calculations (GIAO/B3LYP/6-31G­(d,p)/PCM, chloroform), were readily applied to these structures, producing well-defined analytical characterization, and the associated methodology is described in detail. Furthermore, on the basis of dynamic NMR experiments, both <b>1</b> and <b>2</b> were found to exist in a perylene-centered conformational dynamic equilibrium (Δ<i>G</i>‡ = 13–17 kcal/mol), which primarily caused the observed ambiguities in conventional 1-D spectra

Morphologic, structural, and optical characterization of sol-gel derived TiO2 thin films for memristive devices

Sol-gel derived TiO2 thin films were prepared by spin- coating from an alcoholic solution of titanium isopropoxide. With the aim to develop titania layers suitable for memristive devices, the films were deposited onto test structures based on fused silica quartz substrates patterned with a Ti (5nm)/Pt (50nm) layer. The reported fabrication protocol is suitable for the development of a memristive device. Optical, structural, and morphological features of the samples were investigated with complementary techniques, such as scanning electron microscopy (SEM), prism coupling m-line and micro-Raman spectroscopy as well as transmittance and profilometry measurements. The quality of the surface of the obtained films was evaluated by SEM technique, and the morphology of samples deposited with different fabrication protocols was investigated. Additionally, a computer code for the refractive index and thickness estimation from the transmittance spectra was developed by unconstrained optimization procedure. The results of simulation were in good agreement with the experimental data obtained by m-line measurements. Moreover, the porosity of a specific set of test unannealed films has been estimated. TiO2 films exhibit thickness of tens of nm, and micro-Raman spectroscopy in conjunction with SEM indicate the presence of anatase phase after thermal annealing at 400 °C. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Computing Lewisham College

Title from cover. Also available via the InternetAvailable from British Library Document Supply Centre- DSC:0570. 514355(137/2002) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo