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Leaching of chemicals from adhesion promoters is, in particular, problematic for the food, water, pharmaceutical, and MedTech industries where any chemical contamination is unacceptable. A solution to this issue is to employ covalently attached nanoscale polymer brushes as adhesive layers for plastics. One of the industrially most relevant adhesion targets in that respect is poly(dimethylsiloxane) (PDMS), being used for many high-end applications such as catheters and breast implants. In this work, we have synthesized a novel surface-immobilized poly(2-hydroxyethyl methacrylate)-based brush adhesive containing reactive hydrosilane groups that can bond directly to PDMS. Two different medical grades of addition-cured PDMS were molded on top of titanium substrates already coated with the polymer brush. Titanium plates were used for the chemical analysis, and titanium rods were used for adhesion testing. Adhesion testing revealed a high adhesive force, in which cohesive failure was observed in the bulk PDMS. The necessity of the hydrosilane group in the polymer brush adhesive layer was demonstrated in comparative studies using similar brushes lacking this functionality.

The vast compositional space of Prussian blue analogues (PBAs), formula A(x)M[M'(CN)(6)](y)center dot nH(2)O, allows for a diverse range of functionality. Yet, the interplay between composition and physical properties-e.g., flexibility and propensity for phase transitions-is still largely unknown, despite its fundamental and industrial relevance. Here we use variable-pressure X-ray and neutron diffraction to explore how key structural features, i.e., defects, hydration, and composition, influence the compressibility and phase behavior of PBAs. Defects enhance the flexibility, manifesting as a remarkably low bulk modulus (B-0 approximate to 6 GPa) for defective PBAs. Interstitial water increases B-0 and enables a pressure-induced phase transition in defective systems. Conversely, hydration does not alter the compressibility of stoichiometric MnPt(CN)(6), but changes the high-pressure phase transitions, suggesting an interplay between low-energy distortions. AMnCo(CN)(6) (A(I) = Rb, Cs) transition from F (4) over bar 3m to P (4) over bar n2 upon compression due to octahedral tilting, and the critical pressure can be tuned by the A-site cation. At 1 GPa, the symmetry of Rb0.87Mn[Co(CN)(6)](0.91) is further lowered to the polar space group Pn by an improper ferroelectric mechanism. These fundamental insights aim to facilitate the rational design of PBAs for applications within a wide range of fields.

The widespread application of quantum dots greatly profits from their broad absorption band. However, the variable nature of excitations within these bands is expected to result in undesired excitation energy dependence of steady state emission properties. We demonstrate the different role played by hot and cold carrier trapping in determining fluorescence quantum yields. Our analysis relates the energetic parameters with the available knowledge on the dynamics of charge trapping. It turns out that detrapping processes play a pivotal role in determining steady state emission properties. We studied excitation dependent photoluminescence quantum yields (PLQY) in different CdSe/CdxZn1-xS (x = 0, 0.5, and 1) quantum dots to identify best performing heterostructures in terms of shell thickness and composition. Our rationalization of the observed behavior is focused on the modulation of trapping and detrapping rates. The combination of experimental results and PLQY kinetics modeling reveals the need to consider hot-carrier trapping, supporting recent dynamics observations. This work provides a deeper insight into the trapping process in quantum dots, relating its energetics and dynamics.

The modulation of noncovalent bonding interactions by redox processes is a central theme in the fundamental understanding of biological systems as well as being ripe for exploitation in supramolecular science. In the context of host-guest systems, we demonstrate in this article how the formation of inclusion complexes can be controlled by manipulating the redox potential of a cyclophane. The four-electron reduction of cyclobis(paraquat-p-phenylene) to its neutral form results in altering its binding properties while heralding a significant change in its stereoelectronic behavior. Quantum mechanics calculations provide the energetics for the formation of the inclusion complexes between the cyclophane in its various redox states with a variety of guest molecules, ranging from electron-poor to electron-rich. The electron-donating properties displayed by the cyclophane were investigated by probing the interaction of this host with electron-poor guests, and the formation of inclusion complexes was confirmed by single-crystal X-ray diffraction analysis. The dramatic change in the binding mode depending on the redox state of the cyclophane leads to (i) aromatic donor-acceptor interactions in its fully oxidized form and (ii) van der Waals interactions when the cyclophane is fully reduced. These findings lay the foundation for the potential use of this class of cyclophane in various arenas, all the way from molecular electronics to catalysis, by virtue of its electronic properties. The extension of the concept presented herein into the realm of mechanically interlocked molecules will lead to the investigation of novel structures with redox control being expressed over the relative geometries of their components.

The synthesis of 2-ferrocenylbenzo[b]-thiophene, 3-ferrocenylbenzo[b]thiophene, 1,1-bis(2-indene)-ferrocene, and the two isomers of 1,1'-bis(2-benzo[b]-thiophene)ferrocene was efficiently achieved by using the palladium-catalyzed Negishi C,C cross-coupling reaction of the appropriate bromobenzo[b]thiophene derivative with ferrocenylzinc chloride. The accessibility of differently substituted benzo[b]thiophenes and a comparison with indene analogues allowed an in-depth investigation on how the geometric modifications and the presence of sulfur affect their physical properties. The molecular structure of 3-ferrocenylbenzo[b]-(t)hiophene has been determined by X-ray diffraction. Electrochemistry and UV-vis-NIR spectroscopy, in particular the appearance upon oxidation of a charge transfer absorption in the NIR region, are rationalized through quantum chemistry calculations and in the framework of the Hush theory.

A detailed photophysical investigation of the photocatalytic water oxidation system based on the tetraruthenium polyoxometalate [Ru4(μ-O)4(μ–OH)2(H2O)4(γ-SiW10O36)2]10– (1) as the catalyst, the tetranuclear ruthenium dendrimer [Ru{(μ-2,3-dpp)Ru(bpy)2}3]8+ (2) as the light-harvesting photosensitizer, and persulfate (S2O82–) as the sacrificial electron acceptor has shown that the water oxidation mechanism proceeds through an unusual, “anti-biomimetic” pathway: The first photochemical event is indeed a reductive quenching of the excited photosensitizer by the catalyst, followed by electron scavenging by the sacrificial electron acceptor, both occurring on the picosecond time scale within ion-paired species. As an unprecedented photoreaction mechanism for molecular water oxidation systems, these results suggest a new way to combine photosensitizers and catalysts, taking advantage of suitable chemical interactions and alternative photoinduced processes for the construction of efficient water-splitting devices.

Four imidazo-anthraquinone derivatives (2a-d) functionalized with different aromatic and heteroaromatic groups were synthesized, characterized and their coordination behaviour against selected anions and cations tested. Acetonitrile solutions of probes 2a-d showed charge-transfer absorption bands in the 407-465 nm range whose positions depend on the electron donor strength of the (hetero)aromatic systems appended to the electron-acceptor anthraquinone group. The four probes were also emissive with fluorescence bands in the 533-571 nm interval. The recognition ability of 2a-d was evaluated in the presence of F-, Cl-, Br-, I-, OCN-, BzO-, ClO4-, AcO-, HSO4-, H2PO4- and CN-. Of all anions tested, only F-, AcO- and H2PO4- were able to induce the appearance of new red-shifted absorption bands in the probes that were ascribed to a deprotonation process involving the N-H moiety of the imidazole ring, especially when F- was used. Moreover addition of F-, AcO- and H2PO4- induced moderate quenching in the emission of 2a-d together with the appearance of a new red-shifted emission band. The UV-visible and emission behaviour of the four probes in the presence of Cu2+, Co2+, Mg2+, Fe3+, Ba2+, Fe2+, Ni2+, Ca2+, Zn2+, Pb2+, Cd2+, Cr3+, Al3+, K+ and Li+ was also assessed. Of all cations tested, only addition of the trivalent cations Fe3+, Cr3+ and Al3+ induced the appearance of a new blue-shifted emission in 2a-d that were ascribed to a preferential coordination of these metals with the acceptor part of the probes. Moreover trivalent cations induced an important quenching of the emission for 2a-d., Fundação para a Ciência e a Tecnologia (FCT)

Different classes of chromophores have been developed for the dye solar cell (DSC), including as the two main classes organometallic dyes, with Ru-based complexes and Zn-porphyrin complexes, and metal-free dyes. They result in different recombination behavior by electron transfer at the titania/dye/electrolyte interface, where the dye molecule plays a pivotal role. We present an overview of the main factors that control recombination depending on dye structural and electronic properties: the substituent’s nature, the size and nature of the π bridge, the type of absorption onto the titania surface, and the structure of the donor electron moiety or anchoring group. Different recombination mechanisms arise, including direct recombination to redox electrolytes and through a dye cation intermediate. This work is supported by Generalitat Valenciana under project PROMETEO/2009/058 and by Ministerio de Economia y Competitividad of Spain (Consolider HOPE CSD2007-00007, MAT2010-19827).

We report on the synthesis of hybrid molecules consisting of a porphyrin or corrole chromophore axially coordinated to a [Co-III(dmgH)(2)(Cl)](+/- 0) (dmg = dimethylglyoxime) unit via a pyridine group as potential hydrogen forming entities in H2O/THF medium. Photophysical, electrochemical, and pulse radiolysis studies on the hybrids and/or their separate components show that selective excitation of the porphyrin or corrole chromophore in its first singlet excited state leads to fast charge separation due to chromophore to cobalt electron transfer. However, this charge separation is followed by even faster charge recombination thereby preventing the accumulation of a reduced cobalt species which would lead to hydrogen production. It is important, nevertheless, that addition of a sacrificial electron donor slows the charge recombination down. In light of the latter it comes as hardly surprising that the photocatalysis experiments in the presence of a sacrificial electron donor (i.e., triethylamine) show modest rates of hydrogen production. Journal of Physical Chemistry C

Excited-state interactions between (S)- or (R) fluorescence (S)- or (R)-FBP) and thymidine (dThd) covalently linked in dyads 1 or 2 have been investigated. In both dyads, the only emitting species is (FBP)-F-1*, but with a lower fluorescence quantum yield (phi(F)) and a shorter fluorescene lifetime (tau(F)) than when free in solution. These an results indicate that dynamic quenching occurs either by electron transfer or via exciplex formation, with FBP as the charge-donating species. In acetonitrile, both mechanisms are favored, while in dioxane exciplex formation is predominating. Isomer 1 displays lower values of OF and rF than its analogue 2, indicating that the relative spatial arrangement of the chromophores plays a significant role. The triplet quantum yields (0-F) of 1 and 2 are significantly higher than the expectations based solely on 'FBP* dThd intersystem crossing quantum yields (Oisc), with OT (1) > OT (2). This can be explained in terms of intramolecular charge recombination at the radical ion pairs and/or the exciplexes, which would be again dependent on geometrical factors. The triplet lifetimes (IT) of 3FBP* dThd and free 3FBP* are similar, indicating the lack of excited-state interactions at this stage. The FBP dThd dyads could, in principle, constitute appropriate model systems for the elucidation of the excited-state interactions in noncovalent DNA ligand complexes., Financial support from the Spanish Government (Grants CTQ2010-14882 and CTQ2009-13699), Salvador Madariaga Program (Grant to M.C.J.), Juan de la Cierva Program (contract to I.V.), Generalitat Valenciana (Prometeo 2008/090), and the Universitat Politecnica de Valencia (PAID 05-11, ref 2766) is gratefully acknowledged.

The reactivity of [Fe-2(CO)(4)(kappa(2)-LL)(mu-pdt)](+) complexes (pdt = S(CH2)(3)S, propanedithiolate) with different substrates L' (L' = CO, MeCN, P(OMe)(3)) was investigated electrochemically in order to assess the influence of the chelating ligand kappa(2)-LL (LL = I-Me-CH2-I-Me (1(+)), dppe (2(+)); I-Me = 1-methylimidazol-2-ylidene). This latter ligand is effectively shown to affect the reactivity of the cations in different ways: when L' = CO, the adduct [Fe-2(CO)(4)(mu-CO)(kappa(2)-dppe)(mu-pdt)](+) (2-CO+) was clearly observed by cyclic voltammetry, whereas [Fe-2(CO)(4)(mu-CO)(kappa(2)-I-Me-CH2-I-Me)(mu-pdt)](+) (1-CO+) was not detected, although DFT calculations show that the energies of the products and the activation barriers to their formation are similar. When L' = MeCN, the adducts X-MeCN+ with X = 1, 2 are both observed, but the formation is easier when LL = dppe. Finally, the reaction of [Fe-2(CO)(4)(kappa(2)-I-Me-CH2-I-Me)(mu-pdt)](+) (1(+)) with P(OMe)(3) produces the disubstituted dication [Fe-2(CO)(2){P(OMe)3}(2)(kappa(2)-I-Me-CH2-I-Me)(mu-CO)(mu-pdt)](2+) (4(2+)) via a disproportionation reaction, while previous studies demonstrated that monocationic derivatives were obtained when LL = dppe. Complex 4[PF6](2) was fully characterized, and its X-ray crystal structure confirms the presence of a carbonyl ligand in a bridging position, which did not exist in the related P(OMe)(3)-substituted kappa(2)-dppe cations.

The dyads 3, 4, and 6, combining the Bodipy chromophore with a Pt(bpy)(bdt) (bpy = 2,2'-bipyridine, bdt = 1,2-benzenedithiolate, 3 and 6) or a Pt(bpy)(mnt) (mnt = maleonitriledithiolate, 4) moiety, have been synthesized and studied by UV-vis steady-state absorption, transient absorption, and emission spectroscopies and cyclic voltammetry. Comparison of the absorption spectra and cyclic voltammograms of dyads 3, 4, and 6 and those of their model compounds 1a, 2, 5, and 7 shows that the spectroscopic and electrochemical properties of the dyads are essentially the sum of their constituent chromophores, indicating negligible interaction of the constituent chromophores in the ground state. However, emission studies on 3 and 6 show a complete absence of both Bodipy-based fluorescence and the characteristic luminescence of the Pt(bpy)(bdt) unit. Dyad 4 shows a weak Pt(mnt)-based emission. Transient absorption studies show that excitation of the dyads into the Bodipy-based (1)pi pi* excited state is followed by singlet energy transfer (SEnT) to the Pt(dithiolate)-based (MML)-M-1'CT (mixed metal-ligand to ligand charge transfer) excited state (tau(3)(SEnT) = 0.6 ps, tau(4)(SEnT) = 0.5 ps, and tau(6)(SEnT) = 1.6 ps), which undergoes rapid intersystem crossing to the (MMLL)-M-3'CT state due to the heavy Pt(II) ion. The (MMLL)-M-3'CT state is then depopulated by triplet energy transfer (TEnT) to the low-lying Bodipy-based 3 pi pi* excited state (tau(3)(TEnT) = 8.2 ps, tau(4)(TEnT) = 5 ps, and tau(6)(TEnT) = 160 ps). The transition assignments are supported by TD-DFT calculations. Both energy-transfer processes are shown to proceed via a Dexter electron exchange mechanism. The much longer time constants for dyad 6 relative to 3 are attributed to the significantly poorer coupling and resonance of charge-separated species that are intermediates in the electron exchange process. J Am Chem Soc

The boron dipyrrin (Bodipy) chromophore was combined with either a free-base or a Zn porphyrin moiety (H(2)P and ZnP respectively), via an easy synthesis involving a cyanuric chloride bridging unit, yielding dyads Bodipy-H(2)P (4) and Bodipy-ZnP (5). The photophysical properties of Bodipy-H(2)P (4) and Bodipy-ZnP (5) were investigated by UV-Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. The comparison of the absorption spectra and cyclic voltammograms of dyads Bodipy-H(2)P (4) and Bodipy-ZnP (5) with those of their model compounds Bodipy, H(2)P, and ZnP shows that the spectroscopic and electrochemical properties of the constituent chromophores are essentially retained in the dyads indicating negligible interaction between them in the ground state. In addition, luminescence and. transient absorption experiments show that excitation of the Bodipy unit in Bodipy-H(2)P (4) and Bodipy-ZnP (5) into its first singlet excited state results in rapid Bodipy to porphyrin energy transfer-k(4) = 2.9 x 10(10) s(-1) and k(s) = 2.2 x 10(10) s(-1) for Bodipy-H(2)P (4) and Bodipy-ZnP (5), respectively-generating the first porphyrin-based singlet excited state. The porphyrin-based singlet excited states give rise to fluorescence or undergo intersystem crossing to the corresponding triplet excited states. The title complexes could also be used as precursors for further substitution on the third chlorine atom on the cyanuric acid moiety. Inorg Chem

A series of new tetrathiafulvalene (TTF) derivatives bearing dimethoxycarbonyl and phenyl or phthalimidyl groups fused to the TTF core (6 and 15-18) has been synthesized as potential soluble semiconductor materials for organic field-effect transistors (OFETs). The electron-withdrawing substituents lower the energy of the HOMO and LUMO levels and increase the solubility and stability of the semiconducting material. Crystal structures of all new TTF derivatives are also described, and theoretical DFT calculations were carried out to study the potential of the crystals to be used in OFET. In the experimental study, the best performing device exhibited a hole mobility up to 7.5 × 10-3 cm2 V-1 s-1). © 2010 American Chemical Society., EU by the EC FP7 ONE-P large-scale project (no. 212311), Marie Curie EST FuMASSEC, DGI, Spain (Contract Nos.CTQ2006-06333/BQU and CTQ2010-19501/BQU), Generalitat de Catalunya, (2009SGR00516), and the programme “Juan de la Cierva”(MICINN). We also thank Stefan T. Bromley for his advice regarding the DFT calculations and CESGA for the use of their installations. The work in Mons is also supported by the European ONE-P project as well as by the Belgian National Fund for Scientific Research (FNRS). Y.O. and J.C. are FNRS research fellows.

7 páginas, 4 figuras, 4 tablas, esquemas., Electron-transfer reactions between iron and cobalt complexes were studied in β-cyclodextrin (βCD), 2-hydroxypropyl-β-cyclodextrin (HβCD), and 18-crown-6 ether (18C6) solutions. The results were rationalized taking as the basis the Marcus−Hush formalism. We employed two different approaches, depending on the kind of receptor and solvent, to obtain the reorganization and reaction free energies that determine the reaction rate constant. The opposite trends in reactivity observed in βCD and HβCD solutions and the behavior in solutions of 18C6 are explained., This work was financed by D.G.I.C.Y.T. (CTQ2008-00008/BQU) and the Conserjería de Educación y Ciencia de la Junta de Andalucía.

peer-reviewed The electrochemical properties of cytochrome c (cyt c) immobilized on multilayer nanozeolite-modified electrodes have been examined in aqueous and nonaqueous solutions. Layers of Linde type-L zeolites were assembled on indium tin oxide (ITO) glass electrodes followed by the adsorption of cyt c, primarily via electrostatic interactions, onto modified ITO electrodes. The heme protein displayed a quasi-reversible response in aqueous solution with a redox potential of +324 mV (vs NHE), and the surface coverage (Gamma*) increased linearly for the first four layers and then gave a nearly constant value of 200 pmol cm(-2). On immersion of the modified electrodes in 95% (v/v) nonaqueous solutions, the redox potential decreased significantly, a decrease that originated from changes in both the enthalpy and entropy of reduction. On reimmersion of the modified electrode in buffer, the faradic response immediately returned to its original value. These results demonstrate that nanozeolites are potential stable supports for redox proteins and enzymes. ACCEPTED peer-reviewed

Reaction of the N,N-disubstituted bis-(hydroxylamino) ligand 2,6-bis [hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine, H(2)bihyat, with V(IV)OSO(4)center dot 5H(2)O in water for 6 h followed by the addition of methyl alcohol resulted in the isolation of the unsymmetrical mu-oxido divanadium(V) compound [V(2)(V)O(2)(mu(2)-O)(bihyat)(hyta)(hyto)]center dot 3H(2)O (1 center dot 3H(2)O) and of the methylhydroxylamido derivative [V(V)O(bihyat)(CH(3)NHO)]center dot H(2)O (2 center dot H(2)O). The N,N-disubstituted mono(hydroxylamino) ligands Hhyta, Hhyto, and CH(3)NHOH were formed by the decomposition of the ligand H(2)bihyat in the presence of vanadium. The structures of compounds 1 center dot 3H(2)O and 2 center dot H(2)O were determined by X-ray crystallography. The structure of 1 center dot 3H(2)O consists of one five-coordinate vanadium(V) atom and one six-coordinate vanadium(V) atom bridged by an oxido group and ligated to a tridentate bihyat(2-) and two bidentate hyta(-) and hyto(-) ligands, respectively. The two terminal oxido groups in 1 center dot 3H(2)O are syn-directed, lying on the same side of the V-O-V plane. The coordination environment of the vanadium atom in 2 center dot H(2)O approximates to a highly distorted pentagonal pyramid with the oxido ligand occupying the apical position. Compounds 1 center dot 3H(2)O and 2 center dot H(2)O were studied by multinuclear NMR ((1)H, (13)C, and (51)V) to elucidate their solution structures. The (51)V NMR of 1 center dot 3H(2)O in anhydrous CD(2)Cl(2) gave two signals at -199 and -508 ppm, which were assigned to the five- and six-coordinate vanadium(V) atoms, respectively. The resonance of the five-coordinate vanadium nucleus, in a field much lower than that expected from Rehder's [Inorg. Chem., 1988, 27, 584-587] referencing scale, was attributed to the low-energy ligand-to-metal charge transfer transition at 605 nm [epsilon(M)=5050 M(-1) cm(-1)] of 1 center dot 3H(2)O according to Pecoraro et al. [J. Am. Chem. Soc., 1992, 114, 9925-9933], Electrospray ionization-mass spectrometry studies were used to follow the decomposition products of H(2)bihyat in the presence of vanadium. Inorg Chem

The complexes of general formulas [Ru-II(terpy)(4-CO2H-4'-Mebpy)(X)](n+) (X = NO (n = 3) and NO2 (n = 1); 1, 2) and [Ru-II(terpy)(4-COGHK-4'-Mebpy)(X)] (X = NO (n = 3) and NO2 (n = 1); 3, 4) were synthesized and characterized. The complex [Ru-II(terpy)(4-CO2-4'-Mebpy)(NO2)](-)7.5H(2)O has also been characterized by X-ray crystallographic studies. It crystallizes in the triclinic system: a = 9.4982(1) angstrom, b = 13.1330(1) angstrom, c = 14.2498(2) angstrom; alpha = 110.5870(6)xbc, beta = 98.4048(5)xbc, gamma = 106.4353(5), P (1) over bar, Z = 2. The crystal structure reveals an extended hydrogen-bonding network. Two water molecules form strong hydrogen bonds with the nitro and the carboxylic oxygen atoms of two separate units of the complex, resulting in a dimeric unit. The dimers are bridged by a (H2O)(15) cluster, consisting of two cyclo-(H2O)(6) species, while an exo-H2O(8) connects them. Two more exo-H2O molecules are joined together and connect the cyclo-(H2O)(6) units with the H2O(1) of the dimeric unit. It was found that complexes 1 and 3 can be transformed into their nitro derivatives in aqueous media at neutral pH. Photorelease of NO in dry MeCN solutions was observed for complexes 1 and 3. Also, complex 2 partially releases (NO2)(-) in MeCN upon visible light irradiation. Complex 2 interacts with short fragments (70-300 bp) of calf thymus DNA shortening slightly the apparent polynucleotide length, while the conjugation of the peptide GHK to it (2) affects its DNA-binding mode. The peptide moiety of complex 4 was found to interact with the DNA helix in a synergistic way with the whole complex. Preliminary results of photocleavage of DNA by complex 2 are also reported. Inorg Chem

The nickel(II) hydride complex [(MeN2N)Ni-H] (2) was synthesized by the reaction of [(MeN2N)Ni-OMe] (6) with Ph2SiH2 and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. 2 was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N–H reductive elimination to give MeN2NH and nickel particles. The second pathway was intermolecular, with H2, nickel particles, and a five-coordinate Ni(II) complex [(MeN2N)2Ni] (8) as the products. 2 reacted with acetone and ethylene, forming [(MeN2N)Ni-OiPr] (9) and [(MeN2N)Ni-Et] (10), respectively. 2 also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [(MeN2N)Ni-Cl] (1) as catalyst, NaOiPr or NaOMe as base, and Ph2SiH2 or Me(EtO)2SiH as the hydride source. The catalysis appears to operate via a radical mechanism.