Jean-François Nicoud

Diketopyrrolopyrrole‐Porphyrin Conjugates with High Two‐Photon Absorption and Singlet Oxygen Generation for Two‐Photon Photodynamic Therapy

Two-photon photodynamic therapy is a promising therapeutic method which requires the development of sensitizers with efficient two-photon absorption and singlet-oxygen generation. Reported here are two new diketopyrrolopyrrole-porphyrin conjugates as robust two-photon absorbing dyes with high two-photon absorption cross-sections within the therapeutic window. Furthermore, for the first time the singlet-oxygen generation efficiency of diketopyrrolopyrrole-containing systems is investigated. A preliminary study on cell culture showed efficient two-photon induced phototoxicity.

Water-Soluble, Donor–Acceptor Biphenyl Derivatives in the 2-(o-Nitrophenyl)propyl Series: Highly Efficient Two-Photon Uncaging of the Neurotransmitter γ-Aminobutyric Acid at λ=800 nm†

By using two-photon (TP)[1] photoreleasable neurotransmitters like glutamate (Glu) or γ-aminobutyric acid (GABA), neuronal processes can be activated or inhibited with high temporal and spatial control (with around one micron three-dimensional precision) with reduced photodamage to cells or organs, and with deeper penetration of the light beam into living tissue compared to that of UV photoactivation.[2]

Status and perspective for molecular nonlinear optics: from crystals to polymers and fundamentals to applications

Abstract Over the past two years, the field of molecular nonlinear optics has benefited from both upstream rejuvenation (the emergence of new molecular engineering guidelines) and downstream application-oriented breakthroughs, helping to bring the field closer to industrial developments. In the fundamentals areas, traditional perspectives based on the paranitroaniline ‘molecular diode’ template are being enlarged to encompass three-dimensional multicharge transfer ‘multipolar’ systems with dipolarless ‘octupoles’, demanding that earlier models and experiments be thoroughly revisited. Furthermore, the relevance of polar structures primarily targeted towards quadratic nonlimear optics has been extended to cubic all-optical processes based on a cascaded sequence of quadratic processes. In the application domain, progress in crystal growth is best illustrated by the demonstration of low threshold pulsed near-IR optical parametric oscillators based on stable organic or organomineral crystals. Functionalized polymers have confirmed their current supremacy as organic optoelectronic device materials with the reports of low voltage electro-optic modulation in integrated waveguide structures and high modulation bandwidth.

A Liquid Crystalline Supramolecular Complex of C60 with a Cyclotriveratrylene Derivative

Cyclotriveratrylene (CTV) derivatives substituted with 9 (1) or 18 (2) long alkyl chains have been prepared. Whereas no liquid crystalline behavior has been observed for 1, the CTV derivative 2 has mesomorphic properties. Indeed, at room temperature compound 2 exhibits a nematic phase characterized by cybotactic groups with a local lamello-columnar order. Both CTV derivatives 1 and 2 are able to form supramolecular complexes with C60 in the solid state. In both cases, the 2:1 host-guest species have been obtained as brown compounds. No liquid crystalline behavior was observed for the supramolecular complex [C60 is included in (1)2]. In contrast, observation of the brown product obtained from C60 and the CTV derivative 2 directly after preparation by polarized optical microscopy revealed a fluid birefringent phase at room temperature. When the sample is heated above 70 degrees C, the birefringence of the texture under the microscope disappears and the X-ray diffraction pattern is transformed into a pattern characteristic of a cubic phase. For the first time in thermotropic liquid crystals, the space group of this cubic phase can be assigned as I4(1)32.

A Copper(I) Bis‐phenanthroline Complex Buried in Fullerene‐Functionalized Dendritic Black Boxes

Virtual inaccessibility to external contact was revealed by electrochemical investigations for a bis(1,10-phenanthroline)copper(I) core embedded in dendrimers with up to 16 peripheral fullerene units (shown schematically). With increasing numbers of fullerene units, less and less light is available to the core, and the small quantity of light energy that reaches the central Cu(I) complex is returned to the external fullerenes by energy transfer-the central core is buried in a dendritic black box.

Molecular Engineering of Photoremovable Protecting Groups for Two-Photon Uncaging†

The photochemical release of theactive molecule is usually induced by an initial one-photonabsorption process, leading to a limited spatial localization ofthe released substance. To overcome this obstacle, two-photon (TP) excitation has recently emerged as a verypromising technique to obtain spatial control.

Molecular tectonics: from enantiomerically pure sugars to enantiomerically pure triple stranded helical coordination network

The self-assembly between a bis-monodentate tecton based on two pyridine units connected to an enantiomerically pure isomannide stereoisomer and HgCl2 leads to the formation of an enantiomerically pure triple stranded helical infinite coordination network which was structurally characterised by X-ray diffraction on single crystal.

Photolabile Glutamate Protecting Group with High One- and Two-Photon Uncaging Efficiencies

A π‐extended [2‐(2‐nitrophenyl)propoxy]carbonyl (NPPOC) derivative has been prepared as an efficient UV and near‐IR photolabile protecting group for glutamate. This glutamate cage compound exhibits efficient photorelease upon one‐photon excitation (εΦ=990 M−1 cm−1 at 315 nm). In addition, it also shows efficient photorelease in activation of glutamate receptors in electrophysiological recordings. Combined with a high two‐photon uncaging cross‐section (δΦ=0.45 GM at 800 nm), its overall properties make this new cage—3‐(2‐propyl)‐4′‐methoxy‐4‐nitrobiphenyl (PMNB)—for glutamate a very promising tool for two‐photon neuronal studies.

Photochemical tools to study dynamic biological processes.

Light‐responsive biologically active compounds offer the possibility to study the dynamics of biological processes. Phototriggers and photoswitches have been designed, providing the capability to rapidly cause the initiation of wide range of dynamic biological phenomena. We will discuss, in this article, recent developments in the field of light‐triggered chemical tools, specially how two‐photon excitation, “caged” fluorophores, and the photoregulation of protein activities in combination with time‐resolved x‐ray techniques should break new grounds in the understanding of dynamic biological processes.

The thermotropic mesophase structure of two long-chain alkyl pyridinium halides

Abstract The thermotropic phase transitions and the mesophase structure of two long-chain alkyl pyridinium halides are described. From small angle X-ray diffraction, optical microscopy, differential scanning calorimetry and dilatometry, the single liquid-crystalline phase found in each material is identified as smectic A. It is argued that the molecules within a layer are oriented alternately and packed in an interdigitated fashion, with the anions sandwiched between the pyridinium rings.