Synthesis of photo- and electroactive stilbenoid dendrimers carrying dibutylamino peripheral groups

Molecular geometry optimization, two-photon absorption and electrochemistry of new diphenylethylene derivatives linking with benzophenone moiety through ether covalent bond

This paper presents the molecular geometry optimization, two-photon absorption and electrochemistry of new dyes containing benzophenone part, including 4-(p-benzoyl-benzyloxy)yl-4'-nitro-diphenylethylene (C1), 4-[N-methyl-N-(2-(p-benzoyl-benzyloxy)yl-ethyl]-4'-nitro-diphenylethylene (C2), 4-[N-ethyl-N-(2-(p-benzoyl-benzyloxy)yl-ethyl]-4'-nitro-diphenylethylene (C3), and 4-N, N-bis[(2-(p-benzoyl-benzyloxy)yl-ethyl]-4'-nitro-diphenyl ethylene (C4). The molecular structural parameters show that the coplanarity of diphenylethylene moiety is diminished in the excited state for C1, while it is enhanced for C2, C3 and C4. The electron density distribution of frontier orbital suggests that the derivatives exhibit (π, π) transition with internal charge transfer character, and the extent of charge transfer of C2, C3 and C4 is larger than that of C1. The derivatives display remarkable two-photon absorption (TPA) induced up-converted emission under 800 nm Ti: Sapphire femtosecond laser excitation. The maximal TPA emission wavelength of C2, C3 and C4 is red-shifted with respect to that of C1. TPA cross sections of C2, C3 and C4 are larger than those of C1. The cyclic voltammograms and the fluorescence lifetimes of the derivatives were determined and discussed.

Synthesis and spectroscopy of novel branched fluorescent dyes containing benzophenone parts and the possibility as fluorescence probes

This paper describes a new fluorescent family of branched dyes containing benzophenone unit including 4-N, N-diphenylamino-4'-phenacyl-stilbene (C1), 4,4'-di(4-benzoylphenylethylene)yl-triphenylamine (C2) and 4,4',4″-tri(4-benzoylphenylethylene)yl-triphenylamine (C3). Benzophenone part is coupled with core through C-C double bond. The chemical structures of the derivatives are characterized with (1)H and (13)C nuclear magnetic resonance and elemental analysis. Strong π-π stacking interactions are discovered with the analysis of the X-ray crystallographic data of C1. The absorption maxima and emission maxima of the derivatives exhibit gradual bathochromic shift from C1 to C3. The optical density of C1, C2 and C3 are shown to be related to the number of branches. The changes of dipole moments between the excited and ground states for C1, C2 and C3 were estimated to be 4.356, 8.091 and 8.479 Derby, respectively by Lippert equation, confirming that the internal charge transfer (ICT) dominates the process of excited singlet state. The possibility as fluorescence probes of the derivatives on the estimation of what region of micelles interacting with samples was evaluated.

Control of Surface Functionality in Poly(phenylenevinylene) Dendritic Architectures

The efficient synthesis of new asymmetric poly(phenylenevinylene) dendritic macromolecules using a stepwise convergent-growth approach is described. By an iterative methodology that made use of the Horner-Wadsworth-Emmons (HWE) reaction, dendrons and dendrimers up to the third generation, with eight different functional groups located at the periphery, were prepared in good yields. Both the number and placement of functionalities can be accurately controlled to afford a large variety of dendritic architectures.

Synthesis and Properties of a Fluorene-Capped Isotruxene: A New Unsymmetrical Star-Shaped π-System

An unsymmetrical star-shaped pi-system (1) with an isotruxene core and three fluorene arms has been synthesized, and its photophysical, electrochemical, and thermochemical properties have been investigated and compared with the corresponding symmetrical truxene derivatives 2a-d (Kanibolotsky, A. L.; Berridge, R.; Skabara, P. J.; Perepichka, I. F.; Bradley, D. D. C.; Koeberg, M. J. Am. Chem. Soc. 2004, 126, 13695-13702). Stronger electronic couplings between the arms in 1 vs 2a-d lead to lower optical band gap, larger splitting in oxidation potentials, and superior thermostability. [structure: see text]

Dendrimer Interior Functional Group Conversion and Dendrimer Metamorphosis−New Approaches to the Synthesis of Oligo(dibenzyl sulfone) and Oligo(phenylenevinylene) Dendrimers

A series of [G1] to [G3]-oligo(dibenzylsulfide) dendrimers containing up to 21 interior dibenzylsulfide moieties was prepared as starting materials toward the syntheses of two new series of oligo(dibenzyl sulfone) and oligo(phenylenevinylene) dendrimers using two different dendrimer-to-dendrimer conversion strategies. The first strategy entailed the interior functionalization of the [G1] to [G3]-oligo(dibenzylsulfide)s to the corresponding [G1] to [G3]-oligo(dibenzyl sulfone)s via hydrogen peroxide oxidation. Successful conversions of up to 21 interior dibenzylsulfide moieties to the corresponding dibenzyl sulfone groups were demonstrated. The second involved the skeletal rearrangements, also named as dendrimer metamorphosis, of the [G1] and [G2]-oligo(dibenzyl sulfone) dendritic backbones to the corresponding [G1] and [G2]-oligo(phenylenevinylene)s dendrimers via the Ramberg-Backlund (RB) reaction. Up to nine RB rearrangements on a dendrimer skeleton were realized and the conversion efficiency of each single RB rearrangement reaction was found to be 96%.

Synthesis and photoluminescent properties of 1,1'-binaphthyl-based chiral phenylenevinylene dendrimers

New chiral, soluble binaphthyl derivatives that incorporate stilbenoid dendrons at the 6,6'-positions have been prepared. The synthesis of the new enantiopure dendrimers was performed in a convergent manner by Horner-Wadsworth-Emmons (HWE) reaction of the appropriately functionalized 1,1'-binaphthyl derivative (R)-1 and the appropriate dendrons (R)(2n)G(n)-CHO. Different electroactive units were incorporated in the peripheral positions of the dendrons in order to tune both the optical and electrochemical behavior of these systems. Fluorescence measurements on the chiral dendrimers reveal a strong emission with maxima between 409 and 508 nm depending upon the substitution pattern. Finally, the redox properties of the dendrimers were determined by cyclic voltammetry, showing the influence of the functional groups at the peripheral positions of the dendrimer on the redox behavior of these systems.

Novel synthesis of protected thiol end-capped stilbenes and oligo(phenylenevinylene)s (OPVs)

The first general procedures for preparation of thiol end-capped stilbenes and oligo(phenylenevinylene)s (OPVs) with tert-butyl- and acetyl-protected thiol termini have been developed. These reactions proceed via Br/Li exchange, McMurry, and Wittig-type reactions. The thiol functionality is protected against strong basic and acidic reaction conditions as a t-Bu sulfide. As a key point in the method, reprotection of the thiol group is accomplished by means of acetyl chloride and boron tribromide. The novel strategy forms the basis for stepwise introduction of 4-mercaptostyryl units in OPVs. The new mono-, di-, and trimercapto OPVs have potential applications as one, two, and three terminal molecular devices in gold nanoparticle clusters, self-assembled monolayers, and optoelectronic devices.