Tommaso Carofiglio

Very strong binding and mode of complexation of water-soluble porphyrins with a permethylated β-cyclodextrin

Abstract Heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin in a pH=7.0 aqueous solution binds meso -tetrakis(4-carboxyphenyl) porphyrin and its zinc complex to yield 2:1 complexes with exceptionally high binding constants. The mode of binding, involving the inclusion of two opposite aryl groups in the cyclodextrin cavity, is clearly defined by a detailed NMR analysis.

Rapid prototyping of multilayer thiolene microfluidic chips by photopolymerization and transfer lamination

A new fabrication process is described allowing rapid prototyping of multilayer microfluidic chips using commercial thiolene optical adhesives. Thiolene monomer liquid is photopolymerized across transparency masks to obtain partially cured patterns supported on thin polyethylene sheets. The patterns are easily laminated and transferred to a substrate due to the elastomeric nature and adhesiveness of partially cured thiolene. The process characteristics are evaluated by realizing several test structures and fluidic chips. As an example of application, the operation of a microfluidic bead array sensor for pH measurements is then described in some detail.

Fullerene/Porphyrin Multicomponent Nanostructures on Ag(110): From Supramolecular Self-Assembly to Extended Copolymers

A novel two-step bottom-up approach to construct a 2D long-range ordered, covalently bonded fullerene/porphyrin binary nanostructure is presented: in the first place, reversible supramolecular interactions between C60 and 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin are exploited to obtain large domains of an ordered binary network, subsequently a reaction between fullerene molecules and the amino-groups residing on porphyrin units, triggered by thermal treatment, is used to freeze the supramolecular nanostructure with covalent bonds. The resulting nanostructure resists high temperature treatments as expected for an extended covalent network, whereas very similar fullerene/porphyrin nanostructures held together only by weak interactions are disrupted upon annealing at the same or at lower temperatures.

Design of acidochromic dyes for facile preparation of pH sensor layers

AbstractEight new acidochromic dyes have been synthesised that can be used for optically monitoring pH in the range from 3 to 12. Their corresponding pKa values have been both measured and calculated theoretically by means of density functional theory. The synthesis of these new dyes is facile without the need for chromatographic purification. The dyes can be covalently linked to polymers containing hydroxyl functions such as cellulose, polyurethane hydrogel, and hydroxyalkyl methacrylate. The resulting sensor layers exhibit significant colour changes both in the UV and in the visible spectral range. FigureSensor layers based on covalently immobilised pH indicator dyes show fast and fully reversible colour changes.

Bulky melamine-based Zn-porphyrin tweezer as a CD probe of molecular chirality†‡

The transfer of chirality from a guest molecule to an achiral host is the subject of significant interest especially when, upon chiral induction, the chiroptical response of the host/guest complex can effectively report the absolute configuration (AC) of the guest. For more than a decade, dimeric metalloporphyrin hosts (tweezers) have been successfully applied as chirality probes for determination of the AC for a wide variety of chiral synthetic compounds and natural products. The objective of this study is to investigate the utility of a new class of melamine-bridged Zn-porphyrin tweezers as sensitive AC reporters. A combined approach based on an experimental CD analysis and a theoretical prediction of the prevailing interporphyrin helicity demonstrates that these tweezers display favorable properties for chiral recognition. Herein, we discuss the application of the melamine-bridged tweezer to the chiral recognition of a diverse set of chiral guests, such as 1,2-diamines, α-amino-esters and amides, secondary alcohols, and 1,2-amino-alcohols. The bulky periphery and the presence of a rigid porphyrin linkage lead, in some cases, to a more enhanced CD sensitivity than that reported earlier with other tweezers.

Melamine-Bridged Bis(porphyrin-ZnII) Receptors: Molecular Recognition Properties

Dimeric metalloporphyrin hosts with tweezer-like structures have been synthesized by reacting the cyanuric chloride scaffold, CC, with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, P, and 5-(4-aminophenyl)-10,15,20-trimesitylporphyrin, M, to yield the homoconjugates free bases PP and MM and the heterodyad PM. Metalation with Zn(II), gives three structurally related ditopic receptors P(Zn)P(Zn), P(Zn)M(Zn), and M(Zn)M(Zn) with differential steric hindrance and conformational rigidity. The solution structure and supramolecular properties of these porphyrin dimers have been investigated as isolated molecules and in the presence of aliphatic alpha,omega-diamines of general formula H(2)N-(CH(2))(n)-NH(2) (n = 4-8) by spectroscopic and theoretical studies including multidimensional NMR, UV-vis, molecular modeling, and computational NMR methods. Binding constants in the range 4.2 x 10(6) to 3.4 x 10(7) M(-1) are observed in dichloromethane at 298 K, with a 3 orders of magnitude increase as compared to monodentate nBuNH(2), thus indicating the occurrence of a host-guest ditopic interaction. Linear correlation graphs are obtained by plotting the Soret band shift (Delta nu, cm(-1)) of the complex as a function of the diamine chain length. Combined NMR evidence and OPLS 2005 Force Field conformational analysis point to a mutual adaptation of both the binding partners in the host-guest complex, whose geometry is mainly dictated by the steric impact of the bulky substituents at the porphyrin periphery.

Stereoselective Photopolymerization of Tetraphenylporphyrin Derivatives on Ag(110) at the Sub-Monolayer Level

We explore a photochemical approach to achieve an ordered polymeric structure at the sub-monolayer level on a metal substrate. In particular, a tetraphenylporphyrin derivative carrying para-amino-phenyl functional groups is used to obtain extended and highly ordered molecular wires on Ag(110). Scanning tunneling microscopy and density functional theory calculations reveal that porphyrin building blocks are joined through azo bridges, mainly as cis isomers. The observed highly stereoselective growth is the result of adsorbate/surface interactions, as indicated by X-ray photoelectron spectroscopy. At variance with previous studies, we tailor the formation of long-range ordered structures by the separate control of the surface molecular diffusion through sample heating, and of the reaction initiation through light absorption. This previously unreported approach shows that the photo-induced covalent stabilization of self-assembled molecular monolayers to obtain highly ordered surface covalent organic frameworks is viable by a careful choice of the precursors and reaction conditions.

Continuous-flow synthesis of an efficient methanofullerene acceptor for bulk-heterojunction solar cells

We report on a three-step, continuous-flow synthesis of [6,6]-phenyl-C61-butyric acid tert-butyl ester (PCBtB), a promising electron-acceptor methanofullerene for solution-processed bulk-heterojunction solar cells, through the integrated use of three elements in a microstructured flow-reactor that eliminate the need of isolation steps, with a definite safety and environmental advantage.

Solid-supported Zn(II) porphyrin tweezers as optical sensors for diamines

A melamine-bridged bis-Zn(II) porphyrin dyad covalently attached onto amino-functionalized TentaGel polymer beads or controlled pore glass (CPG) undergoes a reversible and marked colour change from purple to green upon exposure to a biogenic diamine such as cadaverine both in organic and aqueous media.

Microelectrode voltammetry for studying host-guest complexation equilibria. An analysis of the possibilities of the method

Abstract The use of microelectrode voltammetry in the study of host-guest complexation is described. A digital simulation approach to describe the complexation as a second-order CE mechanism for any kinetic condition is proposed. For a completely mobile equilibrium, the constant can be determined by the very simple relationship (I1/I1,0) = (1 + DrK[L]b)/(1 + K[L]b), where I1/I1,0 is the ratio of the limiting current in the presence and absence of the host species, Dr is the ratio of the diffusion coefficients of the complex and the guest species, K is the equilibrium constant and [L]b is the bulk equilibrium concentration of the host species. Advantage is gained from the linear dependence of the limiting current on the diffusion coefficient of the reactant which allows an enlargement of the measurement range. The potential applicability of the method to electroinactive guest species was also explored by using it in a competitive procedure. Agreement was found between the theoretical results and those relative to the ferrocenecarboxylic acid + β-cyclodextrin and ferrocenecarboxylic acid + p-nitrophenol + β-cyclodextrin systems in aqueous solution at pH 9.2.