René M Williams

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Verified

René verified their affiliation via an institutional email.

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• Dr. in Physical Organic Chemistry
• Professor (Assistant) at University of Amsterdam

Femtosecond transient absorption spectroscopy of thin films of two types of morphologies of diketopyrrolo-pyrrole low band gap polymer / fullerene-adduct blends are presented and indicate triplet state formation by charge recombination, an important loss channel in organic photovoltaic materials. At low laser fluence (approaching solar intensity) c...

Photoinduced charge separation in a mixture of Perylene Red (N,N'-bis(2,6-di-isopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxylic acid bis-imide) and pyrene, organized in thin solid film on quartz, was studied by means of steady-state absorption and emission spectroscopy and by femtosecond transient absorption spectroscopy. Stead...

A molecular square with dimensions of about 4 nm, incorporating sixteen pyrene chromophores attached to four ditopic bay-functionalized perylene bisimide chromophores, has been synthesized by coordination to four Pt(II) phosphine corner units and fully characterized via NMR spectroscopy and ESI-FTICR mass spectrometry. Steady-state and time-resolve...

A covalently functionalized fullerene comprising an electron donating aniline group coupled to the fullerene unit by a saturated heterocyclic bridge is shown to undergo a photoinduced intramolecular electron transfer process that causes quenching of the fluorescence of the adduct and strong decrease of triplet population in polar solvents. VIS-abso...

Metal coordination compounds are currently a focus of research in developing new photosensitizers for materials and medicinal applications. As an abundant element in the earth's crust aluminum is a suitable target element. However, only limited studies are available on its use in photoactive systems. We now report the facile preparation of a librar...

Metal coordination compounds are currently a focus of research in developing new photosensitizers for materials and medicinal applications. As an abundant element in the earth’s crust aluminum is a suitable target element. However, only limited studies are available on its use in photoactive systems. We now report the facile preparation of a librar...

ATTO 565, a Rhodamine-type dye, has garnered significant attention due to its remarkable optical properties, such as a high fluorescence quantum yield, and the fact that it is a relatively stable structure and has low biotoxicity. ATTO 565 has found extensive applications in combination with microscopy technology. In this review, the chemical and o...

The long-lived green luminescence of human bone (that has been heated to 600 °C for a short duration) is attributed to a carbon quantum dot material (derived from collagen) encapsulated and protected by an inorganic matrix (derived from bone apatite) and is more intense in dense rigid and crystalline parts of (healthy) human bones. The strong colla...

ATTO 565, a Rhodamine-type dye, has garnered significant attention due to its remarkable optical properties, such as a high fluorescence quantum yield, it is a relatively stable structure, and has low biotoxicity. ATTO 565 has found extensive applications in combination with microscopy technology. In this review, the chemical and optical properties...

Adding zinc (II) cations and formate anions improves the thermal phase stability of α-FAPbI3 materials, and the spin-coated thin films of such doped FAPbI3 (produced using MACl) show an increased emission lifetime of up to 3.7 μs on quartz (for FA0.8MA0.2PbI3). This work investigates the effects of zinc and formate on the phase stability and time-r...

The covalent combination of a cyanine dye (IR-783) with a tetraphenyl porphyrin unit through an ether linkage results in a photoactive system capable of producing singlet oxygen. The synthesis, characterization and photophysical properties of the resulting novel free base porphyrin–cyanine conjugate named TPPO-IR-783 (TOI) is reported. Excited stat...

Perovskite/Silicon Tandem Solar Cells (PSTSCs) represent an emerging opportunity to compete with industry-standard single junction crystalline silicon (c-Si) solar cells. The maximum power conversion efficiency (PCE) of single junction cells is set by the Shockley–Queisser (SQ) limit (33.7%). However, tandem cells can expand this value to ~ 45% by...

Adding zinc (II) and formate anions improves the thermal phase-stability of alpha-FAPbI3 materials and the spin-coated thin films of such doped FAPbI¬3 show an increased emission lifetime of up to 3.7 microsecond on quartz. This work investigates the effects of zinc and formate on the stability and time resolved photoluminescence of FAPbI3 perovski...

By the application of simultaneous target analysis of multiple femtosecond transient absorption data sets we have identified two loss channels within multi-chromophoric light harvesting arrays. Perylene bisimide-calix[4]arene arrays composed of up to three different types of perylene bisimide (PBI) chromophores, orange (o), red (r), and green (g) P...

Within this work, we review the metal coordination effect on the photophysics of metal dipyrrinato complexes. Dipyrrinato complexes are promising candidates in the search for alternative transition metal photosensitizers for application in photodynamic therapy (PDT). These complexes can be activated by irradiation with light of a specific wavelengt...

Within this work we review the metal coordination effect on the photophysics of metal dipyrrinato complexes. Dipyrrinato complexes are promising candidates in the search for alternative transition metal photosensitizers for application in photodynamic therapy (PDT). These complexes can be activated by irradiation with light of a specific wavelength...

Antibiotics have become increasingly less effective due to development of microbial resistances. About a century ago, photodynamic therapy started out as anti-tumour therapy then later, it became clinically used to treat a wide range of medical conditions, such as non-malignant diseases, [Formula: see text]., dermatological, ophthalmic and cardiova...

The conformational dependence of the matrix element for spin–orbit coupling and of the electronic coupling for charge separation are determined for an electron donor–acceptor system containing a pyrene acceptor and a dimethylaniline donor. Different kinetic and energetic aspects that play a role in the spin–orbit charge transfer intersystem crossin...

The use of a single component porphyrin thin-film for photodynamic antimicrobial chemotherapy is unexplored. Herein, a porphyrin with good film formation properties is used to make thin layers, by physical vapor phase deposition, that are stable in aqueous media and can generate singlet oxygen upon 650 nm excitation. The synthesis and photophysical...

The conformational dependence of the matrix element for spin-orbit coupling and of the electronic coupling for charge separation are determined for an electron donor-acceptor system containing a pyrene acceptor and a dimethylaniline donor. Different kinetic and energetic aspects that play a role in the spin-orbit charge transfer intersystem crossin...

The conformational dependence of the matrix element for spin-orbit coupling and of the electronic coupling for charge separation are determined for an electron donor-acceptor system containing a pyrene acceptor and a dimethylaniline donor. Different kinetic and energetic aspects that play a role in the spin-orbit charge transfer intersystem crossin...

Porphyrinoids are pyrrole-containing macrocycles with varied core sizes, which have found many applications beyond the original chemical and biological aspects. Porphyrin research has a long history, covering a wide variety of disciplines of natural sciences, including photosynthesis, P450-related biocatalysis, organic photovoltaic cells, photodyna...

The increasing number of hospital-acquired infections demand the development of innovative antimicrobial treatments. Antimicrobial photodynamic therapy (aPDT) is a versatile technique which relies on the production of reactive oxygen species (ROS) generated by light-irradiated photosensitizers (PS) in the presence of oxygen (O2). 1H-Phenalen-1-one...

The use of halogens in the crystal engineering of supramolecular porphyrin assemblies has been a topic of strong interest over the past decades. With this in mind we have characterized a series of direct meso-halogenated porphyrins using single crystal X-ray crystallography. This is accompanied by a detailed conformational analysis of all deposited...

The use of halogens in the crystal engineering of porphyrin scaffolds has been a topic of strong interest over the past decades. Previously, this was focused on the introduction of a variety of halogens on the meso-phenyl groups of the porphyrin. However, investigations into the effects of direct halogenation of porphyrins at the meso-position on t...

Archetypal phosphine/borane frustrated Lewis pairs (FLPs) are famed for their ability to activate small molecules. The mechanism is generally believed to involve two‐electron processes. However, the detection of radical intermediates indicates that single‐electron transfer (SET) generating frustrated radical pairs could also play an important role....

Chlorins that bear a gem‐dimethyl group, which facilitates their resistance to oxidation, are of interest for applications in photomedicine. Herein, we present the synthesis and the photophysical properties of two geminal‐dimethyl chlorins (dihydroporphyrins) and their free base counterparts that act as efficient singlet oxygen generators and thus...

Featured Application Understanding the nature and chemistry of defects and rational passivation through compositional engineering by using doping can help to realize higher power conversion efficiencies of perovskite solar cells. Abstract In order to reach the theoretical efficiency limits of lead-based metal halide perovskite solar cells, the vol...

Chlorins that bear a gem-dimethyl group, which attributes their resistance to oxidation, are of interest for applications in photomedicine. Herein, we present the synthesis and the photophysical properties of two geminal-dimethyl chlorins (dihydroporphyrins) and their free base counterparts that act as efficient singlet oxygen generators and thus e...

In order to reach the theoretical efficiency limits of lead-based metal halide perovskite solar cells, the voltage should be enhanced because it suffers from nonradiative recombination. Perovskite materials contain intrinsic defects that can act as Shockley-Read-Hall recombination centers. Several experimental and computational studies have charact...

Triplet formation by charge recombination is a phenomenon that is encountered in many fields of the photo-sciences and can be a detrimental unwanted side effect, but can also be exploited...

We report a detailed characterization of Eu3+ and Tb3+ complexes derived from a tripyridinophane macrocycle bearing three acetate side arms (H3tpptac). Tpptac3- displays an overall basicity (∑ log KiH) of 24.5, provides the formation of mononuclear ML species, and shows a good binding affinity for Ln3+ (log KLnL = 17.5-18.7). These complexes are al...

Featured Application Doping lead perovskite materials with a few percent of zinc-halides increases their stability at ambient conditions, enhances their properties and improves the efficiency of the corresponding solar cell devices. Abstract Recent work of ten different groups shows that the application of zinc-halides in lead perovskite materials...

We present a one-step method to produce air-stable, large grain mixed cationic lead perovskite films and powders under ambient condition. The introduction of 2.5 wt% of Zn(II), confirmed by X-Ray Diffraction (XRD), results in stable thin films which show the same absorption and crystal structure after two weeks of storage under ambient conditions....

This CDF file contains an interactive form of the Classical Marcus theory of electron transfer, to easily calculate and visualise driving force, reorganization energy, the rate and more. This CDF file can be opened with the freely available CDF player: https://www.wolfram.com/cdf-player/ It is a follow up to my "introduction to electron transfer"....

We designed and synthesized cinchona alkaloid derivates PMI-BnCPD, 1 and PMI-dHQD, 2, in which a fluorescent perylene monoimide unit is linked to the quinuclidine fragment. The latter acts as an electron donor, quenching the perylene imide fluorescence in polar solvents. In the organocatalytic application of these compounds, the electron donor is d...

Nowadays, lignins are receiving an increasing interest from the scientific community. Indeed, this biopolymer, formerly considered a waste‐product of the paper industry, appears today as an interesting oil equivalent in many fields. In this context, many chemical modifications of lignins have been presented to valorize this attractive feedstock. Ho...

Mixed cationic lead perovskites containing formamidinium and methylammonium can be stabilized by incorporating ZnI₂as an “internal desiccant”. Next to prolonged stability under ambient conditions we show with XRD that the use of an additive, 3-chloropropyl ammonium chloride, influences crystal formation by orienting the crystals. These...

Very photostable tetrachloro-metalloporphyrins were developed as sensitizers for visible-light-driven water oxidation coupled to cobalt based water-oxidation catalysts in concentrated (0.1 M) phosphate buffer solution. Potassium persulfate (K2S2O8) acts as a sacrificial electron acceptor to oxidize the metalloporphyrin photosensitizers in their exc...

Highly electron deficient benzo[ghi]perylenetriimide (BPTI) chromophores were persistently anchored to a metal oxide electrode surface and reversible formation of their radical anions was shown in air-saturated aqueous buffer solution. Our results show a very low reaction-rate constant of BPTI(.-) with O2 (k=1.92±0.05×10(-2) s(-1) ). BPTI is a robu...

This is a literature Thesis made by Master student Aram Farawar on Perovskites. It may be usefull for anyone interested in the field.

A series of new benzo[ghi]perylenetriimide (BPTI) derivatives has been synthesized and characterized. These remarkably soluble BPTI derivatives show strong optical absorption in the range of λ=300-500 nm and have a high triplet-state energy of 1.67 eV. A cyanophenyl substituent renders BPTI such a strong electron acceptor (Ered =-0.11 V vs. the nor...

Supplementary

A water-soluble Pt(II)-porphyrin with a high potential for one-electron oxidation (1.42 V vs. NHE) proves very suitable for visible-light driven water oxidation in neutral phosphate buffer solution in combination with a variety of water oxidation catalysts (WOCs). Two homogeneous WOCs (iridium(N-heterocyclic carbene) and Co4O4-cubane complexes) and...

By importing a different data-set it is possible to apply the analysis model to other measurements/datasets. You can only change one 'k' at a time (in the K-matrix). Keep the rest fixed (or the analysis may not run. Success, René

This is a zip file of a Gloratan project based on the data and model described in the JPCB-2013 paper. J. Phys. Chem. B 2013, 117, 11239−11248. By importing a different data-set it is possible to apply the analysis model to other measurements/datasets. You can only change one 'k' at a time (in the K-matrix). Keep the rest fixed (or the analysis may...

In addition to the commonly observed single molecule fluorescence intensity fluctuations due to molecular reorientation dynamics, a perylene bisimide-calixarene compound (1) shows additional on-off fluctuations due to its ability to undergo intramolecular excited state electron transfer (PET). This quenching process is turned on rather sharply when...

OPEN ACCESS: Photoinduced charge transport in 1,1-diphenylethene and 2,3-diphenylbutadiene functionalized with an electron donating dimethylamino group and an electron accepting cyano group is reported. UV-spectroscopy reveals that in these compounds, which incorporate a cross-conjugated spacer, a direct charge transfer transition is possible. It i...

The light-driven reduction of protons for the production of molecular hydrogen in multicomponent systems depends on electron relays such as viologens. We describe here the effect of viologens appended with guest moieties (adamantane or bile acid) on the efficiency of a system composed of a cyclodextrin-appended photosensitizer [Ir(ppy)2(pytl-βCD)]C...

Bifunctional molecules that combine independent push-pull fluorophores and azo photochromes have been synthesized to create fluorescent structures upon light-induced migration in neat thin films. Their photochromic and emissive properties have been systematically investigated and interpreted in light of those of the corresponding model compounds. F...

The structure and reactivity of a covalently linked catechol-ortho-benzoquinone (hemiquinone) is studied by UV-Vis and IR absorption spectroscopy. Nanosecond transient absorption spectroscopy of the hemiquinone reveals the formation of bi-radical state consisting of two semiquinone units. It is a long-lived state resulting from proton coupled elect...

The combination of platinum nanoparticles with a tripodal osmium complex that anchors to the metal surface leads, under visible light irradiation, to the formation of solvated electrons. The formation kinetics is limited by the detachment of the electron from the platinum surface into the solution, the particle showing a type of capacitor behavior....

Cationic cyclometalated iridium complexes containing two anionic phenylpyridine (ppy) ligands and the neutral bidentate triazole-pyridine ligand, 2-(1-substituted-1H-1,2,3-triazol-4-yl)pyridine (pytl), were investigated. The complexes display a rich and reversible electrochemical behavior, upon investigations by cyclic voltammetry in strictly aprot...

Light-driven catalytic three component systems for the reduction of protons, consisting of a cyclodextrin-appended iridium complex as photosensitizer, a viologen-based electron relay, and cyclodextrin-modified platinum nanoparticles as the catalyst, were found to be capable of producing molecular hydrogen effectively in water, using a sacrificial e...

The incorporation of fullerene-C60 and of C60 adducts into Triton X-100 (TX100) micelles and into liposomes made of phosphatidyl-ethanolamine from Escherichia coli has been studied. Incorporation curves and UV-Vis absorption spectra for the liposomes are presented. Flash photolysis experiments in TX100 micelles in the presence of the electron donor...

A calix[8]arene derivative has been found to form a water soluble complex with fullerene-C60, but not with C70, which allows extraction of C60 from e.g. toluene into the aqueous phase. Charge transfer character of the complex is evident from strong charge transfer absorption around 440 nm measured in water. Molecular modeling calculations indicate...

A simple theoretical model is presented that describes orientation effects in electron transfer. In this model the twist and dihedral angles between electron donor (D) and acceptor (A) play a role in the distance dependence of charge transfer (CT), next to the conventional distance dependence of electron transfer that is not influenced by the angle...

Synthesis and photophysics of two diketopyrrolopyrrole-based small band gap oligomers, end-capped at both ends with C(60) are presented. Upon photoexcitation of the oligomer, ultrafast energy transfer to the fullerene occurs ( approximately 0.5 ps), followed by an electron transfer reaction. Femtosecond transient absorption has been used to determi...

The photo-fading of crystal violet (CV), one of the earliest synthetic dyes and an ink component, is examined both in solution and on paper. Aqueous solutions of CV were exposed to UV light (365nm) and samples were taken at constant time intervals and analysed with a High Performance Liquid Chromatography-Photo Diode Array (HPLC-PDA) and Liquid Chr...

A new donor-bridge-acceptor (D-B-A) dyad consisting of ruthenium(II) and iridium(III) species separated by an homoconjugated bridge derived from 7,7-diphenylnorbornane [Ir-Nor-Ru](3+) has been synthesised. The photophysical and electrochemical properties of the heterodinuclear complex have been compared with those of the analogous homodinuclear com...

Novel heteroleptic iridium complexes containing the 1-substituted-4-phenyl-1H-1,2,3-triazole (phtl) cyclometalating ligand have been synthesized. The 3+2 Huisgen dipolar cycloaddition method (‘click’ chemistry) was utilized to prepare a class of bidentate ligands (phtl) bearing different substituents on the triazole moiety. By using various ligands...

Essentially complete photoinduced electron transfer quenching of the fluorescence of a perylene-calixarene compound occurs in poly(methyl acrylate) and poly(vinyl acetate) above their glass transition temperatures (T(g)), but the fluorescence is completely recovered upon cooling the polymer matrix to a few degrees below the T(g). The switching can...

The synthesis and photophysical properties of an asymmetrically substituted perylene-bis(dicarboximide), (PDI), system (1) containing a methylene bridged 4-methoxy-benzene donor and a solubilizing branched C-13 alkyl chain are described. As compared to most PDIs, the fluorescence of 1 is strongly quenched in polar (but not in non-polar) solvents du...

A calix[4]arene scaffold has been functionalized with an electron-accepting perylene bisimide as well as an electron-donating pyrene unit. Steady-state and time-resolved spectroscopy indicate a strong charge-transfer (CT) interaction between these two units in all investigated solvents. The signatures of the radical anion of the perylene bisimide a...

Synthesis and photophysics of a series of thiophene-thienopyrazine small band gap oligomers, end-capped at both ends with C(60), are presented. In these triads, a photoinduced electron transfer reaction occurs between the oligomer as a donor and the fullerene as an acceptor. Femtosecond photoinduced absorption has been used to determine the rates f...

Novel 2-(1-substituted-1H-1,2,3-triazol-4-yl)pyridine (pytl) ligands have been prepared by "click chemistry" and used in the preparation of heteroleptic complexes of Ru and Ir with bipyridine (bpy) and phenylpyridine (ppy) ligands, respectively, resulting in [Ru(bpy)(2)(pytl-R)]Cl(2) and [Ir(ppy)(2)(pytl-R)]Cl (R=methyl, adamantane (ada), beta-cycl...

a b s t r a c t A method for assembling Pt nanoparticles (5 nm diameter) on indium tin oxide (ITO) and highly oriented pyrolytic graphite (HOPG) electrodes, via the potential-assisted deposition of pre-formed perthiolated-b-cyclodextrin-capped Pt nanoparticles is described. Cyclic voltammetry allowed control over the surface coverage of monodispers...

Two photoactive cyclodextrin hosts have been prepared and studied in participation on photophysical processes, one with a ruthenium tris(bipyridyl) core which forms a trimeric host and the other with an appended anthracene unit. An acetylide functionalized bipyridyl cyclodextrin, , was prepared by palladium coupling of mono-6-propargyl permethylate...

Here we report the synthesis and characterization of four quinoline-derived foldamers with increasing oligomeric length; dimer O2P, tetramer O4P, pentamer O5P, and nonamer O9P functionalized with on one end an oligo(p-phenylene vinylene) (OPV) and on the other end a perylene bisimide (PB) chromophore. (1)H NMR confirms the formation of the expected...

The synthesis, electrochemical and photophysical properties of a branched molecule 3,5-bis(pyrene-1-yl)-4′-phenyl-2,2′:6′,2″-terpyridine are reported. Spectroscopy in different solvents reveals that an optical electron transfer from the pyrene donor to the terpyridyl electron acceptor can occur in polar media, as the system displays both charge tra...

A cofacially stacked perylenediimide (PDI) dimer with a xanthene linker was studied under a variety of conditions (solvent, temperature) and serves as a model for the molecular interactions occurring in solid films. Intrinsically, the PDI units have a fluorescence quantum yield (Phi F) close to unity, but Phi F is lowered by a factor of 6-50 at roo...

Molecular Photonics Group, Van't Hoff Institute for Molecular Sciences (HIMS), UniVersiteit Van Amsterdam, Nieuwe Achtergracht 129, 1018 WV Amsterdam, The Netherlands, and Department of Physics and Astronomy, Vrije UniVersiteit, de Boelelaan 1081, 1081 HV Amsterdam, The Netherlands ReceiVed: NoVember 22, 2007 Perylene bisimide-calix[4]arene arrays...

Novel covalent fullerene C(60)-perylene-3,4:9,10-bis(dicarboximide) (C(60)-PDI) dyads (1-4) were synthesized and characterized. Their electrochemical and photophysical properties were investigated. Electrochemical studies show that the reduction potential of PDI can be tuned relative to C(60) by molecular engineering through altering the substituen...

Luminescent ruthenium trisbipyridine complexes containing one or two mercapto-alkyl chain(s) on one of the bipyridyl units have been synthesized through a new strategy. The electrochemical and photophysical properties, determined in solution and in the solid state were compared. Deposition on electrode surfaces (gold, platinum and indium tin oxide)...

The photophysical properties of two supramolecular building blocks oc and oc2 consisting of a perylene bisimide chromophore substituted with either one or two calix[4]arene units in the N-imide position as well as those of the reference compound oref without calix[4]arene substituents were investigated. A complete picture of the processes taking pl...

A simple and effective nonlithographic method to produce a novel organization of noble metal nanoparticles into horseshoe-like nanostructures via self-assembly is described. The adsorption of Au nanoparticles stabilized with the dendrimer 1,2,3,4,5,6-hexakis[(3',5'-bis(benzyloxy)benzyl)sulfanylmethyl]benzene (S(6)G(1)) on hydrophilic surfaces (nati...

We report a simple method of forming Au nanostructure arrays over large areas. A thin film of oligothiodendrimer-stabilised Au nanoparticles was prepared via spin-coating on a solid substrate. The morphology of the adsorbed thin films is found to be markedly sensitive to the hydrophobicity of the underlying substrate. Adsorption on hydrophilic surf...

The supramolecular assembly containing an electron donor, zinc 5,10,15,20-meso-tetraferrocenylporphyrin, and a pyridine-substituted fulleropyrrolidine as an electron acceptor, has been investigated. A comparison of the photophysical properties of the separate components and of the assembled system revealed a photoinduced electron-transfer process f...

Two n-type molecular materials are covalently combined into a new photovoltaic component for polymer solar cells. Light harvesting by the perylenediimide results in very fast energy transfer to the fullerene unit, as shown with femtosecond transient absorption spectroscopy in toluene solution. Two energy transfer rates are observed of 2.5 x 10(12)...

Novel dyads containing [60]fullerene–perylenediimide units were developed as light-harvesting acceptors for the preparation of efficient solar cells. The antenna was grafted onto C$_{60}$ with the aim to improve the absorption spectrum of materials used in bulk-heterojunction devices. Electrochemical and photophysical studies of these dyads in solu...

Rod-shaped nanocrystals are formed by self assembly of t-Bu-phenyl substi-tuted tetra(carboxamido)perylenes (BPP) in different solvents. The structure and the di-mensions of the nano-rods may be controlled by the choice of the hydrogen-bond ac-cepting capacity of the solvent (DMSO, DMF, DMAc, HMPA), by the concentration and by the composition of so...

Photoinduced intra-molecular energy transfer in two ketoprofen(KP)-naproxol(NPX) diastereomers proceeds via two pathways. Very fast singlet–triplet energy transfer (k=1.2×1011s−1) from KP to NPX occurs for a small percentage (6%) and the major pathway is triplet–triplet energy transfer (k∼3×109s−1). This was shown with femtosecond transient absorpt...