BOPHY-Fullerene C60 Dyad as a Photosensitizer for Antimicrobial Photodynamic Therapy

A novel BOPHY–fullerene C₆₀ dyad ( BP-C₆₀ ) was designed as a heavy-atom-free photosensitizer (PS) with potential uses in photodynamic treatment and reactive oxygen species (ROS)-mediated applications. BP-C₆₀ consists of a BOPHY fluorophore covalently attached to a C₆₀ moiety through a pyrrolidine ring. The BOPHY core works as a visible-light-harvesting antenna, while the fullerene C₆₀ subunit elicits the photodynamic action. This fluorophore–fullerene cycloadduct, obtained by a straightforward synthetic route, was fully characterized and compared with its individual counterparts. The restricted rotation around the single bond connecting the BOPHY and pyrrolidine moieties led to the formation of two atropisomers. Spectroscopic, electrochemical, and computational studies disclose an efficient photoinduced energy/electron transfer process from BOPHY to fullerene C₆₀. Photodynamic studies indicate that BP-C₆₀ produces ROS by both photomechanisms (type I and type II). Moreover, the dyad exhibits higher ROS production efficiency than its individual constitutional components. Preliminary screening of photodynamic inactivation on bacteria models (Staphylococcus aureus and Escherichia coli) demonstrated the ability of this dyad to be used as a heavy-atom-free PS. To the best of our knowledge, this is the first time that not only a BOPHY–fullerene C₆₀ dyad is reported, but also that a BOPHY derivative is applied to photoinactivate microorganisms. This study lays the foundations for the development of new BOPHY-based PSs with plausible applications in the medical field.     

Nitroxide‐mediated radical copolymerization of methyl methacrylate controlled with a minimal amount of 9‐(4‐vinylbenzyl)‐9H‐carbazole

The controlled nitroxide‐mediated homopolymerization of 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) and the copolymerization of methyl methacrylate (MMA) with varying amounts of VBK were accomplished by using 10 mol % {tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino} nitroxide relative to 2‐({tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino}oxy)‐2‐methylpropionic acid (BlocBuilder?) in dimethylformamide at temperatures from 80 to 125 °C. As little as 1 mol % of VBK in the feed was required to obtain a controlled copolymerization of an MMA/VBK mixture, resulting in a linear increase in molecular weight versus conversion with a narrow molecular weight distribution (M_w /M_n ≈ 1.3). Preferential incorporation of VBK into the copolymer was indicated by the MMA/VBK reactivity ratios determined: r_VBK = 2.7 ± 1.5 and r_MMA = 0.24 ± 0.14. The copolymers were found significantly “living” by performing subsequent chain extensions with a fresh batch of VBK and by ³¹P NMR spectroscopy analysis. VBK was found to be an effective controlling comonomer for NMP of MMA, and such low levels of VBK comonomer ensured transparency in the final copolymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

X-ray crystal structures of <Emphasis Type="Italic">p</Emphasis>-halogenated 6,6-diphenylfulvenes

Crystal structures of a series of p-halogenated 6,6-diphenylfulvenes 2–5 are reported and comparatively discussed including the known structure of the non-halogenate parent compound 1. The molecular structures show twisted conformations of the plane aryl and fulvene subunits against each other, rather unaffected by the different halogen substituents. The packing structures exclusively involve C–H···X (X = F, Cl, π) contacts while Hal···Hal and π-stacking interactions do not occur.     

2-Aminobenzamide and 2-Aminobenzoic Acid as New MALDI Matrices Inducing Radical Mediated In-Source Decay of Peptides and Proteins

One of the mechanisms leading to MALDI in-source decay (MALDI ISD) is the transfer of hydrogen radicals to analytes upon laser irradiation. Analytes such as peptides or proteins may undergo ISD and this method can therefore be exploited for top-down sequencing. When performed on peptides, radical-induced ISD results in production of c- and z-ions, as also found in ETD and ECD activation. Here, we describe two new compounds which, when used as MALDI matrices, are able to efficiently induce ISD of peptides and proteins: 2-aminobenzamide and 2-aminobenzoic acid. In-source reduction of the disulfide bridge containing peptide Calcitonin further confirmed the radicalar mechanism of the ISD process. ISD of peptides led, in addition to c- and z-ions, to the generation of a-, x-, and y-ions both in positive and in negative ion modes. Finally, good sequence coverage was obtained for the sequencing of myoglobin (17 kDa protein), confirming the effectiveness of both 2-aminobenzamide and 2-aminobenzoic acid as MALDI ISD matrices.     

Fluxionality in the chemical reactions of transition metal oxide clusters: the role of metal, spin state, and the reactant molecule

The phenomenon of fluxionality in the reactions of transition metal oxide clusters provides many opportunities in various catalytic and industrial processes. To gain a better understanding into the various factors influencing this phenomenon, we have carried out an electronic structure investigation of the fluxionality pathways when W(3)O(6)(-) and Mo(3)O(6)(-) clusters react with hydrogen sulfide and ammonia. The study illustrates how the metal (W vs Mo), different spin states of the anionic metal oxide cluster (doublet vs quartet), and the nature of the nonmetal in the small molecule (O vs S vs N), all affect the fluxionality pathway. The thermodynamically facile fluxionality pathway with H(2)S detaches both the hydrogens from hydrogen sulfide and can thus be very useful in the petrochemical and desulfurization industries. The fluxionality pathway with NH(3) results in interesting metal-bound imines and bridged amines. However, the overall fluxionality process with NH(3) is found to be thermodynamically unfavorable.     

Use of Melem as a Nucleophilic Reagent to Form the Triphthalimide C6N7(phthal)3—New Targets and Prospects

Melem ( 1 ), as one of the most important representatives of the tri‐s‐triazine compounds, can be used as a nucleophilic reagent in reactions with phthalic acid derivatives. The synthesis of 2,5,8‐triphthalimido‐tri‐s‐triazine (C₆N₇(phthal)₃, 2 ) was investigated starting from phthalic anhydride or phthalic dichloride in various solvents, at different temperatures as well as in the solid state. NMR measurements (solution and solid state), IR spectroscopy and elemental analysis indicated the formation of a cyclic imide. Single‐crystal structure analysis of a 1:1 adduct of 2 with nitromethane proved the molecular structure expected for a phthalimido‐s‐heptazine. DFT calculations were performed to obtain a better insight into the structural features of compound 2 , especially the interaction of the carbonyl groups with the tri‐s‐triazine nitrogen atoms. The title compound 2 shows promising properties: it is thermally stable up to 500 °C in air and shows strong photoluminescence with a maximum emission at around 500 nm. The potential of the nucleophilic reaction of melem with other strong electrophiles provides new targets and prospects.     

Quantifying the elasticity and viscosity of geometrically confined polymer films via thermal wrinkling

We apply thermal wrinkling, which is a surface instability that occurs during thermal annealing of polymer films geometrically confined by a rigid substrate and a flexible superstrate, to study the elasticity and viscosity of chemically crosslinked polymer systems. Specifically, we study the thermal wrinkling of aluminum‐capped polyhydroxystyrene films with different extent of chemical crosslinking and find that that the rate of change of the wrinkling wavelength with annealing time and temperature has unique relationships with the elasticity and viscosity of the polymer network. With the aid of analytical expressions that relate the time‐ and temperature‐dependent evolution of the wrinkle wavelength to the elasticity and viscosity, we are able to quantify the elastic modulus and shear viscosity of geometrically confined polymer thin films as a function of the degree of crosslinking. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

N‐Heterocyclic Carbenes and Imidazole‐2‐thiones as Ligands for the Gold(I)‐Catalysed Hydroamination of Phenylacetylene

Gold(I) complexes of 1‐[1‐(2,6‐dimethylphenylimino)alkyl]‐3‐(mesityl)imidazol‐2‐ylidene (C^Imine_R), 1,3‐dimesitylimidazol‐2‐ylidene (IMes) and of the corresponding thione derivatives (S^Imine_R and IMesS) were prepared and structurally characterised. The solid‐state structure of the C^Imine_R and S^Imine_R gold(I) complexes showed monodentate coordination of the ligand and a dangling imine group that could bind reversibly to the metal centre to stabilise otherwise unstable catalytic intermediates. Interestingly, reaction of C^Imine_tBu with [AuCl(SMe₂)] led to the formation of [(C^Imine_tBu)AuCl], which rearranges upon crystallisation into the unusual complex cation [(C^Imine_tBu)₂Au]⁺, with AuCl₂^? as the counterion. The activity of the gold complexes in the hydroamination of phenylacetylene with substituted anilines was tested and compared to control catalyst systems. The best catalytic performance was obtained with [(C^Imine_tBu)AuCl], with the exclusive formation of the Markovnikov addition product in excellent yield (>95 %) regardless of the substituents on aniline.