Synthesis,Spectroscopic and Electrochemical Studies of Novel Transition Metal Complexes with Quadridentate Schiff Base

A novel quadridentate, N₂O₂ type Schiff base, synthesized from 1,4‐bis‐(o‐aminophenoxy)butane and 2‐hydroxynaphthalin‐1‐carbaldehyde, forms stable complexes with transition metal ions such as Co(II), Cu(II) and Ni(II) in DMF. Microanalytical data, elemental analysis, magnetic measurements, UV‐visible and IR‐spectra as well as conductance measurements were used to confirm the structures. Electrochemical measurements show that metal complexes undergo quasi‐reversible one‐electron redox processes. The voltammetric results also revealed that the CuL complex has the highest electron transfer rate indicating that both the Cu(II) and Cu(I) forms appear in a similar planar configuration, so the electron transfer does not require larger reorganization of the complex.     

Direct Electron Transfer of Hemoglobin on a Carbon Ionic Liquid Electrode with TiO2 Nanopatricle as Enhancer

Room temperature ionic liquids (RTILs) N‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) was fabricated and applied to adsorb the hemoglobin (Hb) and TiO₂ nanoparticles on the electrode surface step by step to form a Hb modified electrode noted as TiO₂/Hb/CILE. UV‐Vis and FT‐IR spectra showed that Hb in the film retained its native conformations. Cyclic voltammetric experiments indicated that a pair of well‐defined quasi‐reversible redox peaks appeared with the formal potential (E^0′) located at ?0.251 V (vs. SCE) at pH 7.0 phosphate buffer solution (PBS), which was the characteristic of heme Fe(III)/Fe(II) redox couples. Electrochemical parameters of the Hb in the film such as the electron transfer coefficient (α), the electron transfer number (n) and the standard electron transfer rate constant (k_s) were estimated as 0.469, 0.87 and 0.635 s^?1, respectively.     

Electronic Properties of Mono‐Substituted Tetraferrocenyl Porphyrins in Solution and on a Gold Surface: Assessment of the Influencing Factors for Photoelectrochemical Applications

Two unsymmetric meso‐tetraferrocenyl‐containing porphyrins of general formula Fc₃(FcCOR)Por (Fc=ferrocenyl, R=CH₃ or (CH₂)₅Br, Por=porphyrin) were prepared and characterized by a variety of spectroscopic methods, whereas their redox properties were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) approaches. The mixed‐valence [Fc₃(FcCOR)Por]ⁿ⁺ (n=1,3) were investigated using spectroelectrochemical as well as chemical oxidation methods and corroborated with density functional theory (DFT) calculations. Inter‐valence charge‐transfer (IVCT) transitions in [Fc₃(FcCOR)Por]⁺ were analyzed, and the resulting data matched closely previously reported complexes and were assigned as Robin–Day class II mixed‐valence compounds. Self‐assembled monolayers (SAMs) of a thioacetyl derivative (Fc₃(FcCO(CH₂)₅SCOCH₃)Por) were also prepared and characterized. Photoelectrochemical properties of SAMs in different electrolyte systems were investigated by electrochemical techniques and photocurrent generation experiments, showing that the choice of electrolyte is critical for efficiency of redox‐active SAMs.     

Modulating the Optoelectronic Properties of Large,Conjugated, High‐Energy Gap,Quaternary Phosphine Oxide Hosts: Impact of the Triplet‐Excited‐State Location

The purposeful modulation of the optoelectronic properties was realised on the basis of a series of the large, conjugated, phosphine oxide hosts 9,9‐bis‐{4′‐[2‐(diphenylphosphinoyl)phenoxy]biphenyl‐4‐yl}‐9H‐fluorene (DDPESPOF), 9,9‐bis‐{3′‐(diphenylphosphinoyl)‐4′‐[2‐(diphenylphosphinoyl)phenoxy]biphenyl‐4‐yl}‐9H‐fluorene (DDPEPOF), 9‐[4′‐(9‐{4′‐[2‐(diphenylphosphoryl)phenoxy]biphenyl‐4‐yl}‐9H‐fluoren‐9‐yl)biphenyl‐4‐yl]‐9H‐carbazole (DPESPOFPhCz) and 9‐[4′‐(9‐{3′‐(diphenylphosphoryl)‐4′‐[2‐(diphenylphosphoryl)phenoxy]biphenyl‐4‐yl}‐9H‐fluoren‐9‐yl)biphenyl‐4‐yl]‐9H‐carbazole (DPEPOFPhCz). The last two are quaternary with fluorenyls as linking bridges, diphenylphosphine oxide (DPPO) moieties as electron acceptors and diphenylethers and carbazolyls as two different kinds of electron donors. Owing to the fine‐organised molecular structures and the mixed indirect and multi‐insulating linkages, all of these hosts achieve the same first triplet energy levels (T₁) of 2.86 eV for exothermic energy transfer to phosphorescent dopants. The first singlet energy levels (S₁) and the carrier injection/transportation ability of the hosts were accurately modulated, so that DPESPOFPhCz and DPEPOFPhCz revealed extremely similar optoelectronic properties. However, the T₁ state of the former is localised on fluorenyl, whereas the carbazolyl mainly contributes to the T₁ state of the latter. A lower driving voltages and much higher efficiencies of the devices based on DPESPOFPhCz indicated that the chromophore‐localised T₁ state can suppress the quenching effects through realising independent contributions from the different functional groups to the optoelectronic properties and the embedding and protecting effect on the T₁ states by peripheral carrier transporting groups.     

Modification of Electrode Surfaces by Self‐Assembled Monolayers of Thiol‐Terminated Oligo(Phenyleneethynylene)s

The wire‐like properties of four S‐(4‐{2‐[4‐(2‐phenylethynyl)phenyl]ethynyl}phenyl) thioacetate derivatives, PhC≡CC₆H₄C≡CC₆H₄SAc ( 1 ), H₂NC₆H₄C≡CC₆H₄C≡CC₆H₄SAc ( 2 ), PhC≡CC₆H₂(OMe)₂C≡CC₆H₄SAc ( 3 ) and AcSC₆H₄C≡CC₆H₄C≡CC₆H₄SAc ( 4 ) (Figure 1 ), all of which possess a high degree of conjugation along the oligo(phenyleneethynylene) (OPE) backbone, were investigated as self‐assembled monolayers (SAMs) on gold and platinum electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The redox probe [Fe(CN)₆]₄^? was used in both the CV and impedance experiments. The results indicate that the thiolates derived from thioacetate‐protected precursor molecules 1 and 2 form well‐ordered monolayers on a gold electrode, whereas SAMs derived from 3 and 4 exhibit randomly distributed pinholes. The electron tunnelling resistance and fractional coverage of SAMs of all four compounds were examined using electron tunnelling theory. The analysis of the results reveal that the well‐ordered SAMs of 1 and 2 exhibit higher charge‐transfer resistance in comparison to the defect‐ridden SAMs of 3 and 4 . The additional steric bulk offered by the methoxy groups in 3 is likely to prevent efficient packing within the SAM, leading to a microelectrode behaviour, when assembled on a gold electrode surface. The protected dithiol derivative 4 probably binds to the surface through both terminal groups which prevents dense packing and leads to the formation of a monolayer with randomly distributed pinholes. Atomic force microscopy (AFM) was used to examine the morphology of the monolayers, and height images gave root‐mean‐square (RMS) roughness′s which are in agreement with the proposed SAM structures.     

Solvatochromism in Binary Solvent Mixtures by Means of a Penta‐tert‐butyl Pyridinium N‐Phenolate Betaine Dye

The solvatochromic behavior of a penta‐tert‐butyl prydinium N‐phenolate betaine dye was studied using UV‐visible spectrophotometry in several binary mixture solvents. The solvent polarity parameter, E_T (1) (kcal. mol^?1) was calculated from the position of the longest‐wavelength intramolecular charge transfer absorption band of this penta‐tert‐butyl betaine dye. For binary solvent mixtures, all plots of E_T (1) versus the mole fraction of a more polar component are nonlinear owing to preferential solvation of the probe by one component of the binary solvent mixture. In the computation of E_T (1) it was assumed that the two solvents mixed interact to form a common structure with an E_T (1) value not always intermediate between those of the two solvents mixed. The results obtained are explained by the strong synergism observed for some of the binary mixtures with strong hydrogen bond donors (HBD) solvents such as alcohols.     

Accessing the Triplet State in Heavy‐Atom‐Free Perylene Diimides

Previous studies of perylenediimides (PDIs) mostly utilized the lowest singlet excited state S₁. Generation of a triplet excited state (T₁) in PDIs is important for applications ranging from photodynamic therapy to photovoltaics; however, it remains a formidable task. Herein, we developed a heavy‐atom‐free strategy to prompt the T₁←S₁ intersystem crossing (ISC) by introducing electron‐donating aryl (Ar) groups at the head positions of an electron‐deficient perylenediimide (PDI) core. We found that the ISC efficiency increases from 8 to 54 % and then to 86 % by increasing the electron‐donating ability of head‐substituted aryl groups from phenyl (p‐PDI) to methoxyphenyl (MeO‐PDI) and then to methylthioxyphenyl (MeS‐PDI). By enhancing the intramolecular charge‐transfer (ICT) interaction from p‐PDI to MeO‐PDI, and then to MeS‐PDI, singlet oxygen generation via energy‐transfer reactions from T₁ of PDIs to ³O₂ was demonstrated with the highest yield of up to 80 %. These results provide guidelines for developing new triplet‐generating PDIs and related rylene diimides for optoelectronic applications.     

Synthesis and characterization of a thiadiazole/benzoimidazole‐based copolymer for solar cell applications

In this study, we synthesized a new polymer, PCTDBI , containing alternating carbazole and thiadiazole‐benzoimidazole (TDBI) units. This polymer (number‐average molecular weight = 25,600 g mol^?1), which features a planar imidazole structure into the polymeric main chain, possesses reasonably good thermal properties (T_g = 105 °C; T_d = 396 °C) and an optical band gap of 1.75 eV that matches the maximum photon flux of sunlight. Electrochemical measurements revealed an appropriate energy band offset between the polymer's lowest unoccupied molecular orbital and that of PCBM, thereby allowing efficient electron transfer between the two species. A solar cell device incorporating PCTDBI and PCBM at a blend ratio of 1:2 (w/w) exhibited a power conversion efficiency of 1.20%; the corresponding device incorporating PCTDBI and PC₇₁BM (1:2, w/w) exhibited a PCE of 1.84%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

The photochromic behaviour of two viologen salts modulated by the distances between the halide anions and the cationic N atoms of viologen

In recent years, viologens and their derivatives have received much attention due to their various potential applications, ranging from electro‐ or photochromic devices to clean energy. Generally, viologen compounds exhibit a colour change upon being subjected to an external stimulus. However, the chromic mechanism is still ambiguous, because there are many electron‐transfer pathways for a chromic compound that need to be considered. Thus, exploring new chromic viologen‐based compounds with one pathway should be important and meaningful. In this article, two new viologen‐based derivatives, namely 1‐(2‐cyanobenzyl)‐4,4′‐bipyridinium chloride (o‐CBbpy·Cl), C₁₈H₁₄N₃⁺·Cl^? ( 1 ), and 1‐(2‐cyanobenzyl)‐4,4′‐bipyridinium bromide (o‐CBbpy·Br), C₁₈H₁₄N₃⁺·Br^? ( 2 ), have been synthesized and characterized. Interestingly, both isomorphic compounds possess only one electron‐transfer pathway, in which 1‐(2‐cyanobenzyl)‐4,4′‐bipyridinium cations (o‐CBbpy) and halide anions are employed as electron donors and acceptors, respectively. Salts 1 and 2 consist of o‐CBbpy cations involved in π–π interactions and hydrogen‐bond interactions, and halide anions weakly hydrogen bonded to the viologen cations. The salts show different photoresponsive characteristics under identical conditions, which should be mainly related to the distances between the halide cations and the cationic N atoms of o‐CBbpy but not the electronegativities of the halogen atoms. These results should not only help in understanding that the distance of the electron‐transfer pathway plays an important role in viologen‐based photochromism, but should also guide the design and synthesis of additional photochromic materials.     

Behavior of Halogen Bonds of the Y−X⋅⋅⋅π Type (X,Y=F,Cl, Br,I) in the Benzene π System,Elucidated by Using a Quantum Theory of Atoms in Molecules Dual‐Functional Analysis

The nature of halogen bonds of the Y?X‐?‐π(C₆H₆) type (X, Y=F, Cl, Br, and I) have been elucidated by using the quantum theory of atoms in molecules (QTAIM) dual‐functional analysis (QTAIM‐DFA), which we proposed recently. Asterisks (?) emphasize the presence of bond‐critical points (BCPs) in the interactions in question. Total electron energy densities, H_b( r _c), are plotted versus H_b( r _c)?V_b( r _c)/2 [=(?²/8m)?²ρ_b( r _c)] for the interactions in QTAIM‐DFA, in which V_b( r _c) are potential energy densities at the BCPs. Data for perturbed structures around fully optimized structures were used for the plots, in addition to those of the fully optimized ones. The plots were analyzed by using the polar (R, θ) coordinate for the data of fully optimized structures with (θ_p, κ_p) for those that contained the perturbed structures; θ_p corresponds to the tangent line of the plot and κ_p is the curvature. Whereas (R, θ) corresponds to the static nature, (θ_p, κ_p) represents the dynamic nature of the interactions. All interactions in Y?X‐?‐π(C₆H₆) are classified by pure closed‐shell interactions and characterized to have vdW nature, except for Y?I‐?‐π(C₆H₆) (Y=F, Cl, Br) and F?Br‐?‐π(C₆H₆), which have typical hydrogen‐bond nature without covalency. I?I‐?‐π(C₆H₆) has a borderline nature between the two. Y?F‐?‐π(C₆H₆) (Y=Br, I) were optimized as bent forms, in which Y‐?‐π interactions were detected. The Y‐?‐π interactions in the bent forms are predicted to be substantially weaker than those in the linear F?Y‐?‐π(C₆H₆) forms.     

Electrochemical oxidation of 4‐tert‐butylcatechol in the presence of β‐cyclodextrin: Interplay between E and CE mechanisms

Electrochemical behavior of 4‐tert‐butylcatechol (H₂Q) in the presence of β‐cyclodextrin (β‐CD) was studied using cyclic voltammetry and hydrodynamic voltammetry. An electrochemical model in which both H₂Q and its oxidized form (Q) created inclusion complexes with β‐CD was proposed, and it was concluded that both free (as a result of complex‐dissociation reaction) and complex species could performed electron transfer. The heterogeneous rate constant for electron transfer of the inclusion complexes and their kinetic and thermodynamic parameters were obtained using digital simulation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 507–513, 2012     

Orientational Preference of Long,Multicenter Bonds in Radical Anion Dimers: A Case Study of π‐[TCNB]22− and π‐[TCNP]22−

The similar shape and electronic structure of the radical anions of 1,2,4,5‐tetracyanopyrazine (TCNP) and 1,2,4,5‐tetracyanobenzene (TCNB) suggest a similar relative orientation for their long, multicenter carbon?carbon bond in π‐[TCNP]₂^2? and in π‐[TCNB]₂^2?, in good accord with the Maximin Principle predictions. Instead, the two known structures of π‐[TCNP]₂^2? have a D_2h(θ=0°) and a C₂(θ=30°) orientation (θ being the dihedral angle that determines the rotation of one radical anion relative to the other along the axis that passes through center of the two six‐membered rings). The only known π‐[TCNB]₂^2? structure has a C₂(θ=60°) orientation. The origin of these preferences was investigated for both dimers by computing (at the RASPT2/RASSCF(30,28) level) the variation with θ of the interaction energy (E_int) and the variation of the E_int components. It was found that: 1) a long, multicenter bond exists for all orientations; 2) the E_int(θ) angular dependence is similar in both dimers; 3) for all orientations the electrostatic component dominates the value of E_int(θ), although the dispersion and bonding components also play a relevant role; and 4) the Maximin Principle curve reproduces well the shape of the E_int(θ) curve for isolated dimers, although none of them reproduce the experimental preferences. Only after the (radical anion)^.? ??? cation⁺ interactions are also included in the model aggregate are the experimental data reproduced computationally.     

Surface‐Tuned Electron Transfer and Electrocatalysis of Hexameric Tyrosine‐Coordinated Heme Protein

Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine‐coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self‐assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl‐terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this “disc” orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi‐reversible redox behavior with rate constant k_s values between 0.93 and 2.86 s^?1 and apparent formal potentials ${E{{0{^{\prime }}\hfill \atop {\rm app}\hfill}}}$ between ‐131.1 and ‐249.1 mV. On the MUA/MU‐modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH.     

Intimate blending of binary polymer systems from their common cyclodextrin inclusion compounds

A procedure for the formation of intimate blends of three binary polymer systems polycarbonate (PC)/poly(methyl methacrylate) (PMMA), PC/poly(vinyl acetate) (PVAc) and PMMA/PVAc is described. PC/PMMA, PC/PVAc, and PMMA/PVAc pairs were included in γ‐cyclodextrin (γ‐CD) channels and were then simultaneously coalesced from their common γ‐CD inclusion compounds (ICs) to obtain intimately mixed blends. The formation of ICs between polymer pairs and γ‐CD were confirmed by wide‐angle X‐ray diffraction (WAXD), fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). It was observed [solution ¹H nuclear magnetic resonance (NMR)] that the ratios of polymers in coalesced PC/PMMA and PC/PVAc binary blends are significantly different than the starting ratios, and PC was found to be preferentially included in γ‐CD channels when compared with PMMA or PVAc. Physical mixtures of polymer pairs were also prepared by coprecipitation and solution casting methods for comparison. DSC, solid‐state ¹H NMR, thermogravimetric analysis (TGA), and direct insertion probe pyrolysis mass spectrometry (DIP‐MS) data indicated that the PC/PMMA, PC/PVAc, and PMMA/PVAc binary polymer blends were homogeneously mixed when they were coalesced from their ICs. A single, common glass transition temperature (T_g) recorded by DSC heating scans strongly suggested the presence of a homogeneous amorphous phase in the coalesced binary polymer blends, which is retained after thermal cycling to 270 °C. The physical mixture samples showed two distinct T_gs and ¹H T_1ρ values for the polymer components, which indicated phase‐separated blends with domain sizes above 5 nm, while the coalesced blends exhibited uniform ¹H spin‐lattice relaxation values, indicating intimate blending in the coalesced samples. The TGA results of coalesced and physical binary blends of PC/PMMA and PC/PVAc reveal that in the presence of PC, the thermal stability of both PMMA and PVAc increases. Yet, the presence of PMMA and PVAc decreases the thermal stability of PC itself. DIP‐MS observations suggested that the degradation mechanisms of the polymers changed in the coalesced blends, which was attributed to the presence of molecular interactions between the well‐mixed polymer components in the coalesced samples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2578–2593, 2005     

Application of Titanium Dioxide Nanowires for the Direct Electrochemistry of Hemoglobin and Electrocatalysis

Titanium dioxide (TiO₂) nanowires were synthesized and used for the realization of direct electrochemistry of hemoglobin (Hb) with carbon ionic liquid electrode (CILE) as the substrate electrode. TiO₂‐Hb composite was casted on the surface of CILE with a chitosan film and spectroscopic results confirmed that Hb retained its native structure in the composite. Direct electron transfer of Hb on the modified electrode was realized with a pair of quasi‐reversible redox waves appeared, indicating that the presence of TiO₂ nanowires could accelerate the electron transfer rate between the electroactive center of Hb and the substrate electrode. Electrochemical behaviors of Hb on the modified electrode were carefully investigated with the values of the electron transfer coefficient (α), the electron transfer number and the heterogeneous electron transfer rate constant (k_s) as 0.58, 0.98 and 1.62 s^‐1. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid and NaNO₂ with wider linear range and lower detection limit, indicating the successful fabrication of a new third‐generation biosensor.     

Application of NiMoO4 Nanorods for the Direct Electrochemistry and Electrocatalysis of Hemoglobin with Carbon Ionic Liquid Electrode

In this paper NiMoO₄ nanorods were synthesized and used to accelerate the direct electron transfer of hemoglobin (Hb). By using an ionic liquid (IL) 1‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) as the basic electrode, NiMoO₄ nanorods and Hb composite biomaterial was further cast on the surface of CILE and fixed by chitosan (CTS) to establish a modified electrode denoted as CTS/NiMoO₄‐Hb/CILE. UV‐vis and FT‐IR spectroscopic results showed that Hb in the film retained its native structures without any conformational changes. Electrochemical behaviors of Hb entrapped in the film were carefully investigated by cyclic voltammetry with a pair of well‐defined and quasi‐reversible redox voltammetric peaks appearing in phosphate buffer solution (PBS, pH 3.0), which was attributed to the direct electrochemistry of the electroactive center of Hb heme Fe(III)/Fe(II). The results were ascribed to the specific characteristic of NiMoO₄ nanorods, which accelerated the direct electron transfer rate of Hb with the underlying CILE. The electrochemical parameters of Hb in the composite film were further carefully calculated with the results of the electron transfer number (n) as 1.08, the charge transfer coefficient (α) as 0.39 and the electron‐transfer rate constant (k_s) as 0.82 s^?1. The Hb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid (TCA) in the concentration range from 0.2 to 26.0 mmol/L with a detection limit of 0.072 mmol/L (3σ), and H₂O₂ in the concentration range from 0.1 to 426.0 µmol/L with a detection limit of 3.16×10^?8 mol/L (3σ).     

Host/Guest Simulation of Fluorescent Probes Adsorbed into Low‐Density Polyethylene, 1. Excimer Formation of 1,3‐Di(1‐pyrenyl)propane

Molecular dynamics and Rotational Isomer State/Monte Carlo techniques with a Dreiding 1.01 Force Field are employed to study the excimer formation of isolated 1,3‐di(1‐pyrenyl)propane and the probe adsorbed into a low‐density polyethylene (LDPE) matrix model. The probability of formation of each molecular conformer at several temperatures was calculated using these theoretical techniques. Conformational statistical analysis of the four torsion angles (ϕ₁, ϕ₂, θ₁, θ₂) of Py3MPy showed that the angles —C—C^ar— (ϕ₁, ϕ₂) present two states c ^± = ±90°; and the angles —C—C— (θ₁, θ₂), the three trans states = 180°, g ^± = ±60°. The correlation of θ₁–θ₂ torsion angles showed that the most probable pairs were g⁺g^– and g^–g⁺ for the excimer‐like specimens, although these angles are distorted because of interactions with the polymer matrix. The temperature dependence of the excimer‐formation probability revealed that this process was thermodynamically controlled in the isolated case. When the probe was adsorbed into the LDPE matrix, the excimer formation process was reversed at T = 375 K. At T >  375 K, the behavior was similar to the isolated case but, at T < 375 K, excimer formation probability increased with temperature as found experimentally by steady‐state fluorescence spectroscopy. This temperature was coincident with the onset of the LDPE melting process, determined experimentally by thermal analysis.     

Red to Blue High Electrochromic Contrast and Rapid Switching Poly(3,4‐ethylenedioxypyrrole)–Au/Ag Nanocomposite Devices for Smart Windows

Poly(3,4‐ethylenedioxypyrrole) (PEDOP)–Ag and PEDOP–Au nanocomposite films have been synthesized for the first time by electropolymerization of the conducting‐polymer precursor in a waterproof ionic liquid, 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, followed by Ag/Au nanoparticle incorporation. That the Ag/Au nanoparticles are not adventitious entities in the film is confirmed by a) X‐ray photoelectron spectroscopy, which provides evidence of Ag/Au–PEDOP interactions through chemical shifts of the Ag/Au core levels and new signals due to Ag–N(H) and Au–N(H) components, and b) electron microscopy, which reveals Au nanoparticles with a face‐centered‐cubic crystalline structure associated with the amorphous polymer. Spectroelectrochemistry of electrochromic devices based on PEDOP–Au show a large coloring efficiency (η_max=270 cm² C^?1, λ=458 nm) in the visible region, for an orange/red to blue reversible transition, followed by a second, remarkably high η_max of 490 cm² C^?1 (λ=1000 nm) in the near‐infrared region as compared to the much lower values achieved for the neat PEDOP analogue. Electrochemical impedance spectroscopy studies reveal that the metal nanoparticles lower charge‐transfer resistance and facilitate ion intercalation–deintercalation, which manifests in enhanced performance characteristics. In addition, significantly faster color–bleach kinetics (five times of that of neat PEDOP!) and a larger electrochemical ion insertion capacity unambiguously demonstrate the potential such conducting‐polymer nanocomposites have for smart window applications.     

A New Approach for the Photosynthetic Antenna–Reaction Center Complex with a Model Organized Around an s‐Triazine Linker

Two new artificial mimics of the photosynthetic antenna‐reaction center complex have been designed and synthesized (BDP‐H₂P‐C₆₀ and BDP‐ZnP‐C₆₀). The resulting electron‐donor/acceptor conjugates contain a porphyrin (either in its free‐base form (H₂P) or as Zn‐metalated complex (ZnP)), a boron dipyrrin (BDP), and a fulleropyrrolidine possessing, as substituent of the pyrrolidine nitrogen, an ethylene glycol chain terminating in an amino group C₆₀‐X‐NH₂ (X=spacer). In both cases, the three different components were connected by s‐triazine through stepwise substitution reactions of cyanuric chloride. In addition to the facile synthesis, the star‐type arrangement of the three photo‐ and redox‐active components around the central s‐triazine unit permits direct interaction between one another, in contrast to reported examples in which the three components are arranged in a linear fashion. The energy‐ and electron‐transfer properties of the resulting electron‐donor/acceptor conjugates were investigated by using UV/Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. Comparison of the absorption spectra and cyclic voltammograms of BDP‐H₂P‐C₆₀ and BDP‐ZnP‐C₆₀ with those of BDP‐H₂P, BDP‐ZnP and BDP‐C₆₀, which were used as references, showed that the spectroscopic and electrochemical properties of the individual constituents are basically retained, although some appreciable shifts in terms of absorption indicate some interactions in the ground state. Fluorescence lifetime measurements and transient absorption experiments helped to elucidate the antenna function of BDP, which upon selective excitation undergoes a rapid and efficient energy transfer from BDP to H₂P or ZnP. This is then followed by an electron transfer to C₆₀, yielding the formation of the singlet charge‐separated states, namely BDP‐H₂P ^.+‐ C₆₀ ^.? and BDP‐ZnP ^.+‐ C₆₀ ^{. ?}. As such, the sequence of energy transfer and electron transfer in the present models mimics the events of natural photosynthesis.     

Influence of P‐Bonded Bulky Substituents on Electronic Interactions in Ferrocenyl‐Substituted Phospholes

2,5‐Diferrocenyl‐1‐Ar‐1H‐phospholes 3 a – e (Ar=phenyl ( a ), ferrocenyl ( b ), mesityl ( c ), 2,4,6‐triphenylphenyl ( d ), and 2,4,6‐tri‐tert‐butylphenyl ( e )) have been prepared by reactions of ArPH₂ ( 1 a – e ) with 1,4‐diferrocenyl butadiyne. Compounds 3 b – e have been structurally characterized by single‐crystal XRD analysis. Application of the sterically demanding 2,4,6‐tri‐tert‐butylphenyl group led to an increased flattening of the pyramidal phosphorus environment. The ferrocenyl units could be oxidized separately, with redox separations of 265 ( 3 b ), 295 ( 3 c ), 340 ( 3 d ), and 315 mV ( 3 e ) in [NnBu₄][B(C₆F₅)₄]; these values indicate substantial thermodynamic stability of the mixed‐valence radical cations. Monocationic [ 3 b ]⁺–[ 3 e ]⁺ show intervalence charge‐transfer absorptions between 4650 and 5050 cm^?1 of moderate intensity and half‐height bandwidth. Compounds 3 c – e with bulky, electron‐rich substituents reveal a significant increase in electronic interactions compared with less demanding groups in 3 a and 3 b .