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Three zwitterionic meso-substituted A3B- and AB2C-porphyrins containing one sulfonato alkylpyridinium substituent and three or two alkoxy-substituted phenyl groups were synthesized in good yield and fully characterized as to their physicochemical properties by a variety of techniques. This new series of inner salt donor-acceptor meso-substituted porphyrin derivatives were prepared for possible application as amphiphilic probes for membrane insertion in the area of combined second-harmonic and two-photon fluorescence cellular microscopy. To this end, the linear and nonlinear optical properties of the compounds were characterized, together with their electrochemical and spectroelectrochemical properties in non-aqueous media. The neutral design of such molecules enabled us to determine their second order non-linear properties, both by Electric Field Induced Second Harmonic Generation and Hyper–Rayleigh Scattering. Two-photon absorption cross sections of these dyes were also measured by the two-photon induced fluorescence method. The zwitterionic nature of the inner salt results in very specific solvent-dependent redox-properties, which could be rationalized in terms of solvent-dependent ion-pairing. The overall data electrochemical and photophysical data indicates that these new porphyrinic systems should be good probes for membrane potential sensing.

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.

Five new non-ionic water-soluble two-photon dyes for fluorescence microscopy built around a diketopyrrolopyrrole central core were designed, prepared and characterized by 1 H and 13 C NMR, UV-Visible spectroscopy, HRMS and IR. Excitation and emission wavelengths were tuned by modifying the lengths of the conjugated systems and the nature of the substituents surrounding the diketopyrrolopyrrole central core. These fluorescent dyes are highly photostable and present high one- and two-photon brightness. Their application in confocal and two-photon excited fluorescence microscopy was performed on HeLa cell cultures with low power excitation.

Multi-photon intravital imaging has become a powerful tool to investigate the healthy and diseased brain vasculature in living animals. Although agents for multi-photon fluorescence microscopy of the microvasculature are available, issues related to stability, bioavailability, toxicity, cost or chemical adaptability remain to be solved. In particular, there is a need for highly fluorescent dyes linked to particles that do not cross the blood brain barrier (BBB) in brain diseases like tumor or stroke to estimate the functional blood supply. Plant virus particles possess a number of distinct advantages over other particles, the most important being the multi-valency of chemically addressable sites on the particle surface. This multi-valency, together with biological compatibility and inert nature, makes plant viruses ideal carriers for in vivo imaging agents. Here, we show that the well-known Tobacco mosaic virus is a suitable nanocarrier for two-photon dyes and for intravital imaging of the mouse brain vasculature.

Transforming synaptic input into action potential output is a fundamental function of neurons. The pattern of action potential output from principal cells of the mammalian hippocampus encodes spatial and nonspatial information, but the cellular and circuit mechanisms by which neurons transform their synaptic input into a given output are unknown. Using a combination of optical activation and cell type-specific pharmacogenetic silencing in vitro, we found that dendritic inhibition is the primary regulator of input-output transformations in mouse hippocampal CA1 pyramidal cells, and acts by gating the dendritic electrogenesis driving burst spiking. Dendrite-targeting interneurons are themselves modulated by interneurons targeting pyramidal cell somata, providing a synaptic substrate for tuning pyramidal cell output through interactions in the local inhibitory network. These results provide evidence for a division of labor in cortical circuits, where distinct computational functions are implemented by subtypes of local inhibitory neurons.

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]

Two groups of one-dimensional (1D) boron containing two-photon absorbing fluorophores have been prepared and characterized. One group includes boron atoms incorporated in the conjugated or pseudo conjugated central core and the other contain a boron cluster as an acceptor group at one end of the fluorophores. Two boron containing central cores (with two boron atoms) have been explored: the cyclodiborazane and the pyrazabole moieties. The chosen boron cluster, p-carborane, contains 10 boron atoms. All the prepared fluorophores present high two-photon absorption cross-sections. Some water-soluble as well as lipophylic dyes have been prepared and used in bio-imaging. (C) 2011 Elsevier B.V. All rights reserved.

Boron-containing two-photon-absorbing fluorophores have been prepared as new bifunctional molecules, potentially useful in two-photon excited microscopy (TPEM) and boron neutron capture therapy. They are based on a one-dimensional conjugated system containing a p-carborane entity at one end of the molecule and various electron-donating groups containing oxygen or nitrogen atoms at the other end. We investigated their one- and two-photon photophysical properties. They showed efficient fluorescence in an organic solvent, as well as in water for two of them, allowing microscopy on cell cultures. High two-photon absorption cross sections were determined in the 700-900 nm range. TPEM images were obtained with these new p-carborane-containing fluorophores, with laser intensities in the submilliwatt range.

A series of cyanine fluorophores based on fused aromatics as an electron donor for DNA sensing and two-photon bioimaging were synthesized, among which the carbazole-based biscyanine exhibits high sensitivity and efficiency as a fluorescent light-up probe for dsDNA, which shows selective binding toward the AT-rich regions. The synergetic effect of the bischromophoric skeleton gives a several-fold enhancement in a two-photon absorption cross-section as well as a 25- to 100-fold enhancement in two-photon excited fluorescence upon dsDNA binding.

We report herein the molecular engineering of an efficient two-photon absorbing (TPA) chromophore based on a donor-donor bis-stilbenyl entity to allow conjugation with biologically relevant molecules. The dye has been functionalized using an isothiocyanate moiety to conjugate it with the amine functions of poly(ethylenimine) (PEI), which is a cationic polymer commonly used for nonviral gene delivery. Upon conjugation, the basic architecture and photophysical properties of the active TPA chromophore remain unchanged. At the usual N/P ratio (ratio of the PEI positive charges to the DNA negative charges) of 10 used for transfection, the transfection efficiency and cytotoxicity of the labeled PEI/DNA complexes were found to be comparable to those of the unlabeled PEI/DNA complexes. Moreover, when used in combination with unlabeled PEI (at a ratio of 1 labeled PEI to 3 unlabeled PEI), the labeled PEI does not affect the size of the complexes with DNA. The labeled PEI was successfully used in two-photon fluorescence correlation spectroscopy measurements, showing that at N/P = 10 most PEI molecules are free and the diffusion coefficient of the complexes is consistent with the 360 nm size measured by quasielastic light scattering. Finally, two-photon images of the labeled PEI/DNA complexes confirmed that the complexes enter into the cytoplasm of HeLa cells by endocytosis and hardly escape from the endosomes. As a consequence, the functionalized TPA chromophore appears to be an adequate tool to label the numerous polyamines used in nonviral gene delivery and characterize their complexes with DNA in two-photon applications.

We report here the synthesis and characterization of a new type of non-ionic blue fluorescent water-soluble chromophores specifically designed for two-photon absorption microscopy. The water solubility is induced by introduction of short oligo(ethylene glycol) monomethyl ether moieties. This work has led to low molecular weight dyes with efficient two-photon absorption cross sections and high fluorescence quantum yield in organic solvents as well as in aqueous solutions.

New organic "donor–donor" bis-stilbenyl conjugated chromophores arranged in increasing dimensionality (1D to 3D) have been synthesized in high yields by multiple Heck coupling. The central core is based on a biphenyl, triphenylenyl or spiro-bifluorenyl group when the donor part at each extremity is based on a 3,4,5-tridodecyloxyphenyl group that ensures a high solubility in organic solvents and favors the catalytic coupling reactions. Femtosecond two-photon absorption measurements in solution have evidenced improved two-photon absorption cross-sections (≅ 10-19 cm 4/ GW ) that depend on the arrangement of the chromophores.

The synthesis of the four new enantiomerically pure coordinating tectons based on iso mannide or iso sorbide backbone bearing two pyridine units as coordination sites was achieved and their structure analysed by X-ray diffraction on single crystals. The junction between the pyridine units, connected to the sugar moieties at either position 3 or 4, was achieved by ester groups. Under self-assembly conditions, a mixture of the tecton based on iso mannide bearing two nicotinoyl groups and HgCl 2 generates in the crystalline phase an enantiomerically pure single stranded helical assembly. As demonstrated by X-ray diffraction on single crystal, the infinite directional coordination networks are packed in the syn -parallel fashion, leading thus to a polar crystal. To cite this article: P. Grosshans et al., C. R. Chimie 7 (2004).

In a recent paper (New J. Chem., 2001, 25, 1520), we have analysed crystal structures of some N-aryl pyrimidinones. Based on the occurrence of two-dimensional layers in six out of nine crystals, we proposed that self-assembly in these structures might be analysed in terms of the stacking of 2D hydrogen-bonded layers. We show herein that meta-substituted phenyl pyrimidinones (Br, I, F, NO2, Me, OMe) have an overwhelming preference for the 2D polar arrangement, namely the parallel alignment of 1D chains within a layer. The molecules are arranged in chains mediated by C–H⋯O hydrogen bonds and such motifs are connected via C–H⋯O and C–H⋯halogen interactions in the lateral direction. A notable feature in these structures is that chains of dipolar molecules align in a parallel fashion to produce polar layers. The preference for 2D polarity is explained by the shape of the aryl pyrimidinone molecule and the geometry of interactions between hydrogen bonding functional groups (C–H donors, O/halogen acceptors). However, the polar layers stack in an anti-parallel manner and the crystal structures are centrosymmetric. The task of controlling parallel stacking of polar domains in the 3D crystal is a continuing challenge in our studies.

The synthesis of 2-(4-phenyl)-6-anthracenes and 4,4′-bisphenyl-2,6-anthracenes, disubstituted by saturated (decyloxy) or unsaturated ((Z)-dec-4-enyloxy) chains, is reported. All the materials are liquid crystals and exhibit smectic A and/or C phases. As compared to the saturated chains, the unsaturated ones provide a significant decrease of the transition temperatures. The presence of the central “lath-like” anthracene core in the rigid aromatic moiety is found to induce some molecular π-stackings, at short range, in the mesophases. This molecular peculiarity is thought to be in a large part responsible for the high charge-carrier mobility values measured (i.e. 2 × 10−3 cm2 V−1 s−2), despite the disordered character of the mesophases. Preliminary examination of photodimerisation revealed that the formation of photoadducts was very poor in the smectic phases as compared to the same experiment run in solution. This result was attributed to the instability of the anthracene photodimers at the too high temperatures of the mesophases.

Molecular engineering of efficient two-photon sensitive photolabile protecting groups for neuroscience will be presented as well as their nano-structuration. Application of caged glutamate in brain sciences will be emphasized.

In order to compare the polymorphism of 1-cyano-1-(4-nitrophenyl)-2-(4-methoxyphenyl)ethene CMONS crystallized in solutions to that of CMONS nanocrystals grown in the pores of dense sol-gel matrices, we have first studied the CMONS polymorphism in various solvents which were then used in the nanocrystallization processes. The different polymorphs were characterized by differential scanning calorimetry, X-ray diffraction and absorption as well as luminescence spectroscopies. The differences observed between CMONS powders and CMONS nanocrystals illustrate the role played by the silicate matrices on the polymorphism of CMONS. This matrix effect would be used to stabilize a particular polymorph of an organic phase and thus to adjust the optical properties of the nanocomposite hybrid organic–inorganic material.  2001 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

In a previous crystallographic study of some N-arylpyrimidinones 1, we noted that: (1) C–H⋯O hydrogen bonds connect molecules in a linear array; (2) the charge transfer axis of the chromophore is aligned with the main symmetry operator of point groups 2 or m at ca. 57°, a value that is close to the ideal angle of 54.74°; (3) the methyl and chloro derivatives are isostructural. In this paper, we report the characterisation of chloride and nitrate salt adducts of 1 by X-ray diffraction and the analysis of their packing motifs. Recurrence of the same C–H⋯O supramolecular synthon in three neutral and five HCl and HNO3 adducts of 1 signifies the robustness of this weak hydrogen bond. The occurrence of a mirror plane m in a family of eight crystal structures (four Pnma, two P21/m, one Pbcm, and one Pmn21) is unusual because this symmetry operation is generally avoided due to close packing considerations. Ab initio calculations show that the bisected phenyl conformation present in these crystal structures is the most stable conformation of the pyrimidinone molecule. The presence of aryl and pyrimidinone chromophores in 1, the correct alignment of the aromatic ring in the crystal and the occurrence of 2D polar layers in some crystal structures are favourable factors for non-linear optical applications. However, a strategy for the crystallisation of these achiral molecules in non-centrosymmetric space groups is yet to be achieved. This crystal engineering study simplifies the challenge of complete 3D structural control into a modular 2D+1D problem.

The lamello-columnar mesophase of a [1]benzothieno[3,2-b][1]benzothiophene-2,7-dicarboxylate (BTBT) derivative has been investigated by means of X-rays on an aligned sample. The most probable model of molecular organisation corresponds to an assembly of microcolumns made of alternatively crossed molecules, within the smectic layers. The preliminary investigation by a time-of-flight technique revealed that the mesophase exhibits a bipolar charge transport, with comparable electron and hole mobility values in the order of 2 × 10−3 cm2 V−1 s−1. The high mobility values obtained for this disordered smectic phase can be explained by the improved π-overlap between sandwich-like packed aromatic moieties in the short-range columnar stackings.

In this paper, we considered the case of low molecular weight bimesogenic liquid crystals containing a siloxane moiety as the central part of their molecular architecture. For some of these compounds, both ferro- and antiferroelectric mesophases are present. Two distinct smectic structures can develop as a function of temperature, the first one at high temperature corresponding to a synclinic molecular arrangement with elongated molecules, and the second one at lower temperature corresponding to an anticlinic organisation with V-shaped molecules. Numerical calculations of the energy of different conformations of these bimesogenic molecules presented here indicate that there is no difference in energy between V-shaped and linear conformations regardless of the number of silicon atoms in the siloxane moiety. Thus a microscopic model of the synclinic–anticlinic phase transition is developed where the driving force is indeed a free energy difference between the two phases, and not a difference of energy between the V-shaped and linear conformations. The model explains why the anticlinic SmCA phase is more stable than the synclinic SmC one, why the synclinic SmC phase is generally the higher temperature one, and why in some organosiloxane materials the anticlinic SmCA phase is not present.

Six molecular complexes formed between 4-hydroxy-4'-nitrobiphenyl/stilbene and a 4-substituted pyridine-1-oxide [methyl (1,2), cyano (3,4), and nitro (5,6)] have been studied with the specific aim of assessing a new design strategy for the molecular complexation of new materials that show quadratic nonlinear optical behavior. Five of them (1-4 and 6) exhibit second harmonic generation (SHG) activity when illuminated with 1064-nm Nd 3+ :YAG laser light and, hence, crystallize in noncentrosymmetric space groups. The biphenyl/stilbene component forms a two-dimensional slab structure mediated by phenyl···phenyl (C···H and C···C) interactions, and the polar axes of the biphenyl/stilbene are in an antiparallel alignment. In complexes 1-5, the pyridine-1-oxide component occupies the interslab spaces and is bound to the slabs with strong O-H···O and O-H···N and weak C-H···O hydrogen bonds. In complexes 1-4, the pyridine-1-oxide component is arranged in a herringbone motif, with an optimal orientation thus contributing favorably to the bulk NLO efficiency. This efficiency is equivalent to that of 3-methyl-4-nitropyridine-1-oxide (POM). Complexes 1 and 2 have similar crystal structures in space group P2 1 and comparable lattice constants. Similarly, 3 and 4 have identical crystal packing patterns in space group Pca2 1 . In 5 (space group P2 1 /a), the 4-nitropyridine-1-oxide occupies the space between the slabs in the form of antiparallel dimers. In complex 6 (space group P2 1 ), the slab structure is much changed, without any interslab spacing, and the 4-nitropyridine-1-oxide is also involved in slab formation. Crystals of 6 show a detectable SHG activity equivalent to that of urea.

4-Nitrophenol derivatives are interesting chromophores for nonlinear optics (NLO), being typical donor-acceptor system connected by π conjugation. Due to the presence of the acidic phenolic proton, they also readily form salts with suitably selected organic and metallic bases. The so-formed 4-nitrophenolates have increased molecular hyperpolarizabilities (β). The phenolate and nitro oxygens are strong hydrogen bond acceptors and the nitro group has a tendency to coordinate with metal centers. This opens up two different engineering routes to build NLO materials from these chromophores: (a) organic-organic and (b) metal-organic salts. This paper reviews the crystal packing and nonlinear optical (NLO) efficiency in nitrophenolate crystals engineered through these routes and presents the crystal structure of a new NLO efficient organic-organic salt, I-hydroxy-4-methylpyridinium 3-hydroxy-2,4,6-trinitrophenolate (P2 1 ). In this crystal both the multidipolar anion and dipolar cation are NLO chromophores. The anions form herringbone mediated chain with intra and intermolecular O-H....O hydrogen bonds and the cations are attached to them through strong O-H....O - hydrogen bonds.

Triethylene glycol terminated poly(aryl ether) dendritic branches with an aldehyde function at the focal point have been prepared and attached to C60 by a 1,3-dipolar cycloaddition.

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⊂(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 °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 I4132.

Oligophenylenevinylene derivatives substituted with long alkyl chains on one end and a carboxylic acid function on the other end have been prepared and the dimeric polycatenar calamitic supramolecules resulting from hydrogen bonding of their acid functions show columnar liquid crystalline phases.

Fullerene derivatives in which an oligophenylenevinylene (OPV) group is attached to C60 through a pyrrolidine ring have been prepared by 1,3-dipolar cycloaddition of the azomethine ylides generated in situ from the corresponding aldehydes and sarcosine. Electrochemical and photophysical studies have revealed that ground-state electronic interactions between the covalently bonded OPV moiety and the fullerene sphere are small. The photophysical investigations have also shown that both in dichloromethane and benzonitrile solution an efficient singlet−singlet OPV → C60 photoinduced energy-transfer process takes place, and occurrence of electron transfer, if any, is by far negligible relative to energy transfer. The C60−OPV derivatives have been incorporated in photovoltaic devices, and a photocurrent could be observed showing that photoinduced electron transfer does take place under these conditions. However, the efficiency of the devices is limited by the fact that photoinduced electron transfer from the OPV...

A set of three aryl dimethyl pyrimidinones have been studied and their crystal structures described in terms of networks of C+H’’’O and C+H’’’N hydrogen bonds. Two of the three molecules in this study di4er in the replacement of a chloro group by a methyl group and obey the chloro+methyl exchange rule in that they have nearly identical crystal structures. However, and in contrast to other pairs of compounds so related, the chloro and methyl groups here are not merely isosteric but also form similar polarization-induced Cl’’’Ph and CH3’’’Ph contacts. These conjugated molecules may o4er some scope for nonlinear optical studies. ( 2000 Academic Press

The tetra(4-methoxyphenyl)phosphonium iodide C28H28O4PI (MOPPI) is a crystal built up with quasi octupolar tetrahedral chromophores having quadratic nonlinear optical (NLO) properties. The calculated values of the highest tensor component βxyz for the hyperpolarizable chromophore, in its most stable S4 geometry, vary from 4.23 to 9.23 × 10-30 esu, depending on the methods of calculation. Given the linear absorption maximum at 255 nm, this reveals a good hyperpolarizability−transparency tradeoff. The crystal is twinned by merohedry. The crystal structure was solved until a reliability factor R = 0.048 using 2189 untwinned reflections. The material crystallizes in the noncentrosymmetric orthorhombic space group P212121 with Z = 4 and the unit cell parameters a = b = 10.131(3) A, c = 25.682(6) A. The cation−anion arrangement corresponds to a NaCl-type model weakly distorted. Signal of second harmonic of a crystalline powder at 1.06 μm is nearly equivalent to that of urea.

Received: May 28, 1999Revised: September 10, 1999 [Z13481][1] L. Brammer, J. M. Charnock, P. L. Goggin, R. J. Goodfellow, A. G.Orpen, T. F. Koetzle, J. Chem. Soc. Dalton Trans. 1991, 1789–1798.[2] P. S. Pregosin, H. Ruegger, F. Wombacher, G. van Koten, D. M. Grove,I. C. M. Wehman-Ooyevaar, Magn. Reson. Chem. 1992, 30, 548–551.[3] J. M. Casas, L. R. Falvello, J. Fornie´s, A. Martin, A. J. Welch, Inorg.Chem. 1996, 35, 6009–6014.[4] P. Hobza, R. Zahradnik, Chem. Rev. 1988, 88, 871–897.[5] A. D. Buckingham, P. W. Fowler, J. M. Hutson, Chem. Rev. 1988, 88,963–988.[6] The physical meaning of the individual components is as follows: E

The synthesis of fullerene-functionalized dendritic branches (fullerodendrons) containing C60 spheres at each branching unit has been carried out by a convergent approach using successive esterification and deprotection steps. The tert-butyl protected fullerodendrons containing one, three or seven methanofullerene subunits can be characterized by ESMS owing to their reduction in the electrospray source. The MS analysis of the reduced species also confirmed that all the methanofullerene subunits in the fullerodendrons of highest generation behave as independent redox centers, as shown by their electrochemical behavior.

Amphiphilic methanofullerene derivative 1 is water soluble and micellar aggregation has been evidenced by small-angle X-ray scattering measurements and UV/Vis spectroscopy. Thanks to the high solubility of 1 in polar solvents widely used in sol–gel processing, successful inclusion of 1 in the sol–gel could be easily achieved. The optical limiting properties of the doped sol–gel samples have been evaluated and a fast S1–S0 relaxation has been observed for these samples. This observation appears to be consistent with the presence of micellar aggregates of 1 in the sol–gel. Indeed, the interactions between the fullerene spheres of neighbouring molecules in the clusters may be at the origin of this fast S1–S0 relaxation as already shown in solid C60-films.

a ´´ ´ Abstract We report our recent progress in the synthesis and the study of donor-linked fullerenes. The synthesis of C polyadducts 60 with well defined three-dimensional structure provides versatile building blocks for the preparation of porphyrin-fullerene derivatives with unusual stereochemical and electronic properties. Phenanthroline ligands substituted with fullerene- functionalized dendritic wedges and their copper(I) complexes have been prepared. Electrochemical and photophysical investigations have shown that the bis(phenanthroline)copper(I) central core is somehow buried in a dendritic black box. Finally, fullerene-oligophenylenevinylene hybrids have been synthesised in order to provide a molecular approach to photovoltaic conversion, and to prevent the morphology problems resulting from the phase separation in donor-acceptor composites. © 2000 Elsevier Science Ltd. All rights reserved.

Fullerene-functionalized dendrons containing a C 60 sphere at each branching unit have been prepared by a convergent approach using successive DCC-mediated esterifications followed by cleavage of a t -butyl ester moiety under acidic conditions.

Tris(2,2′-bipyridine)Zn(II) tetrakis(2-chloro-4-nitrophenolate)Zn(II), [Zn(bpy)3][Zn(CNP)4] 1, is a new octupolar material for quadratic nonlinear optics. 1, a chiral metal–organic complex, crystallizes in space group C2. Refinement of the Flack parameter supports the description of the [Zn(bpy)3]2+ cation as the Δ enantiomer. The counterion is an octupolar, tetrahedral assembly of 2-chloro-4-nitrophenolate chromophores around a Zn2+ ion. A second harmonic generation signal equal to 5 × urea is observed. A complex having a slightly different stoichiometry, bis(2,2′-bipyridine)-bis(2-chloro-4-nitrophenolate)Zn(II), crystallizes in the centrosymmetric space group P. The structure of bis(2-chloro-4-nitrophenolate)Zn(II) pentahydrate, a precursor of 1 with P symmetry, is described.

The formation of host-guest complexes between C60 and polybenzyl ether dendrimers with different central cores (phloroglucinol, meso-tetraphenylporphyrin, cyclotriveratrylene) has been investigated in organic solvents by means of 13C-NMR and UV-Vis spectroscopy. The interior of the dendrimers with a phloroglucinol core provides the correctly sized space for the inclusion of [60]fullerene and 13C-NMR studies suggest that the guest resides near the central core. In the dendrimers containing a meso-tetraphenylporphyrin (TPP) core, the absorbance of the porphyrin Soret band is substantially reduced in the presence of [60]fullerene, thus providing evidence for close vicinity of the fullerene guest to the central core. In solution, the cyclotriveratrylene (CTV) unit alone is a poor receptor for fullerene, but its functionalization with polybenzyl ether dendrons affords an internal cavity with a more appropriate shape and dimension, thus allowing complexation. Indeed, the Ka values (order of magnitude 101–102 L mol−1) increase significantly with the generation number of the surrounding dendritic substituents.

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 CuI complex is returned to the external fullerenes by energy transfer—the central core is buried in a dendritic black box.

Dendritic derivatives containing a cyclotriveratrylene core for the complexation of fullerenes have been prepared. The association constants for the binding of fullerene derivatives determined by UV-vis titrations in CH2Cl2 and C6H6 are significantly increased as the generation number of the dendritic substituents is increased.

Sodium 3-methyl-4-nitrophenolate dihydrate (Na3M4NP) is a new stable non-linear optical crystal of Cc monoclinic symmetry. The organic anions having an average calculated molecular hyperpolarisability β xxx ≈20×10 −30 esu are organised in a herringbone motif, inducing, together with water molecules, a very dense packing of NaO 6 edge shared octahedra. A three-dimensional network of homogeneous and short hydrogen bonds close-packs the herringbone motifs in a staggered arrangement. The crystal structure is simply described and explained in relation to basic inorganic structural models.

Four non-linear optically active crystals based on organic salts obtained by bis-protonation of four diamines (trans-(±)-1,2-, trans-(1R,2R)-(–)-, cis-1,2-diaminocyclohexane or R-(–)-2-methylpiperazine) by 2-methoxy-4-nitrophenol have been prepared. Their crystal structures and non-linear optical efficiencies have been studied. The two adjacent proton acceptor sites in 1,2-diaminocyclohexanes play an important role in aligning the 2-methoxy-4-nitrophenolate chromophores in a quasi-perfect polar arrangement by anchoring through short hydrogen bonds. In the case of the methylpiperazinium derivative the symmetrical 1,4 location of proton acceptor sites directs the chromophores to near antiparallel alignment by forming short hydrogen bonds. The second harmonic generation efficiencies at 1.064 µm of Nd 3+ :YAG laser light are equivalent to that of POM (3-methyl-4-nitropyridine-1-oxide) for the three diammoniocyclohexane derivatives and equivalent to twice that of urea for the methylpiperazinium derivative.

Fullerene-functionalized dentritic wedges with a car☐ylic acid function have been attached to a phenanthroline diol derivative. Assembling of the resulting phenanthroline ligands around a copper(I) center gives the corresponding dendritic complexes with 4, 8 or 16 peripherical C 60 groups.

Highly soluble dendritic branches with fullerene subunits at the periphery and a car☐ylic acid function at the focal point have been prepared by a convergent approach, using successive DCC-mediated esterifications followed by cleavage of a t -butyl ester moiety under acidic conditions.

Amphiphilic C60 bisadducts with a polar head-group located atop the carbon sphere and pendant long alkyl chains have been prepared. Preliminary investigations have shown their ability to form stable Langmuir films at the air-water interface.

Einen erheblichen Einflus auf die Redoxeigenschaften der Porphyrineinheit haben die vier Fullerengruppen in 1 (R = C12H25). Das Potential des ersten Oxidationsschrittes ist deutlich anodischer als das eines analogen Porphyrins ohne Fullerensubstituenten. Hergestellt wurde 1 durch BF3-katalysierte Kondensation eines durch doppelte Bingel-Addition erhaltenen, CHO-funktionalisierten C60-Bisaddukts mit Pyrrol.

Reaction of C60 with bis(β-keto esters) in the presence of iodine and diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene provides covalent bisadducts of C60 with high regioselectivity.

Theoretical considerations of the molecular hyperpolarizabilities (β) of donor−acceptor substituted aromatic molecules show that the transfer of a proton from the electron-donor group of an acid to the electron acceptor group of a base could increase β for both resulting ionic species relative to the corresponding neutral molecules. To take advantage of this, the cocrystallization of 4-nitrophenol with various organic bases was studied. Cocrystallization of 4-nitrophenol with 4-(dimethylamino)pyridine gives yellow crystals that display a strong second harmonic signal by the Kurtz and Perry powder test. The material crystallizes in the orthorhombic space group P212121 and is composed of 4-(dimethylamino)pyridinium 4-nitrophenolate 4-nitrophenol (DMAPNP2). Theoretical calculations of the hyperpolarizabilities predict that the values of β are greater for the 4-(dimethylamino)pyridinium and 4-nitrophenolate ions than for the corresponding neutral molecules. A second noncentrosymmetric material has been grown ...

A new nonlinear optical crystal, 2-amino-3-nitropyridinium hydrogensulfate hydrate, has been engineered following a strategy which induces the formation of herringbone motifs of chromophores. The crystal packing of such motifs is non-centrosymmetric, with a P212121 space group. The crystal stability is lowered by the presence of water molecules in the host matrix. The second harmonic generation signal at 530 nm of a powder sample is slightly lower than that of 3-methyl-4-nitropyridine N-oxide. Hydroge′nosulfate hydrate de 2-amino-3-nitropyridinium: un sel organique non-line′aire construit autour d'un chromophore bidimensionnel.Un cristal optiquement non line′aire, le sulfate acide monohydrate′ de 2-amino-3-nitropyridinium a e′te′ pre′pare′ suivant une strate′gie d'inge′nierie cristalline qui a pour but la formation de motifs herringbone organo-mine′raux. De tels motifs s'empilent de facon non centrosyme′trique (P212121). La capture d'une mole′cule d'eau fragilise la matrice anionique a laquelle s'accrochent les chromophores. La re′ponse en ge′ne′ration de second harmonique d'un e′chantillon de poudre a 530nm est plus faible que celle observe′e sur une re′fe′rence de 3-methyl-4-nitropyridine N-oxyde.

Reaction of C60 with malonic acid mono-esters in the presence of iodine and diazabicyclo[5.4.0]undec-7-ene (DBU) provides the corresponding 61-iodo-1,2-methano[60]fullerene-61-carboxylates. This cyclopropanation of C60 seems to occur via a carbenoid intermediate.

Electro-optical properties of optically active mesogenic n-alkyl sulfinates are reported. Two homologous series have been considered, and the properties have been analyzed as a function of the length of aliphatic terminal chains. It is shown that the anisotropic distribution of the transverse dipole moments of the molecules, f, decreases strongly (by about 50%) with increasing chain length for a given tilt angle; this behavior is attributed to large orientational fluctuations. It is shown also that f increases slightly with increasing chain length at a given distance from the transition temperature between the C* and A phases; this is attributed to a better defined building of different smectic sublayers. These two antagonistic effects, together with the dilution effect, act simultaneously in order to keep the spontaneous polarization practically independent of the aliphatic chain length, whereas the tilt angle of the molecules within the smectic C* layers is quite dependent of aliphatic chain length, at ...