An appraisal of the Suzuki cross-coupling reaction for the synthesis of novel fluorescent coumarin derivatives

We report the chemical design and development of 3-aryl-substituted 7-alkoxy-4-methylcoumarins with enhanced fluorogenic properties. The 3-aryl substituents are installed via an optimized Suzuki–Miyaura cross-coupling (SMC) reaction between a 7-alkoxy-3-bromo-4-methylcoumarin and aryl boronic MIDA esters using Pd(OAc)2/XPhos in a catalytic system with K2CO3 in aqueous THF. Under these conditions, an exocyclic ester functionality is found to be unaffected. Subsequent saponification revealed a carboxylic acid functionality that is suitable for conjugation reactions. Evaluation of their fluorescence properties indicated that the installed 3-heteroaryl substituent, particularly benzofuran-2-yl, resulted in a significant red shift of both the excitation and emission wavelengths

In situ conjugation of dithiophenol maleimide polymers and oxytocin for stable and reversible polymer–peptide conjugates

The in situ one-pot synthesis of peptide–polymer bioconjugates is reported. Conjugation occurs efficiently without the need for purification of dithiophenol maleimide functionalized polymer as a disulfide bridging agent for the therapeutic oxytocin. Conjugation of polymers was demonstrated to be reversible and to significantly improve the solution stability of oxytocin

PEG−peptide conjugates

The remarkable diversity of the self-assembly behavior of PEG−peptides is reviewed, including self-assemblies formed by PEG−peptides with β-sheet and α-helical (coiled-coil) peptide sequences. The modes of self-assembly in solution and in the solid state are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized

Branching of substituted push-pull polyenes for enhanced two-photon absorption.

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Branching of Substituted Push-Pull Polyenes for Enhanced Two-Photon Absorption

The paper will focus on the branching of substituted push-pull polyenes in the weak to medium interaction limit. Branching of dipolar units of increasing length is achieved through connection via a central triphenylamine core, leading to three-branched structures. Linear and nonlinear optical properties of these octupolar chromophores are compared to those of their dipolar analogues. In particular, photophysical properties, solvatochromism and two-photon absorption (TPA) cross sections are investigated. Results confirm that the branching strategy leads to TPA activation in spectral regions were the dipolar units are almost transparent and that large TPA enhancement can be achieved on a very large spectral range. Localization of the emitting excited state on a single dipolar branch is also evidenced

Octupolar derivatives functionalized with superacceptor peripheral groups Synthesis and evaluation of the electron-withdrawing ability of potent unusual groups

International audienceNovel tripodal derivatives with a triphenylamine core and that bear "superacidifiers" (i.e., fluorinated sulfoximinyl blocks) or novel sulfiliminyl moieties as peripheral groups were synthesized. These new chromophores show strong absorption in the near-UV region and emission in the visible region. The fluorinated sulfoximinyl moieties were found to behave as potent auxochromic and electron-withdrawing (EW) groups, thus leading to redshifted absorption and emission. These moieties promote a core-to-periphery intramolecular charge transfer (ctp-ICT) transition, the energy of which was found to be correlated to their EW strength. In this study, we provide evidence of a linear correlation between the Hammett constant (σp) values and the electronic gap between the ground and first excited state of the three-branched derivatives. This in turn was used to derive σp values of fluorinated sulfoximinyl moieties. These EWGs show unprecedentedly high σp values, up to 1.45 relative to 0.8 for NO2. Also, by using this method, the sulfiliminyl moiety was shown to exhibit similar EW strength as NO2, while promoting improved transparency and solubility. Finally, the superior EW strength of the fluorinated sulfoximine peripheral moieties was shown to induce significant enhancement of the two-photon absorption responses in the red near-IR region of the three-branched derivatives relative to similar octupoles that bear more usual strong EW groups. These characteristics (improved nonlinear responses or transparency) open new routes for the design of nonlinear optical (NLO) chromophores for optical limiting or electro-optical modulation. Such building blocks could also be of interest for optoelectronic applications, including the development of solar cells. Copyright © 2012 WILEY-VCH Verlag GmbH andamp; Co. KGaA, Weinheim

Branching of dipolar chromophores: effects on linear and nonlinear optical properties

Structurally related chromophores of different symmetry (dipolar, V-shaped, octupolar) are investigated and compared for elucidation of the combined role of branching and charge symmetry on absorption, photoluminescence and twophoton absorption (TPA). Their design is based on the assembly of one, two or three π-conjugated dipolar branches on a central core. Two series of branched structures obtained from a central triphenylamine core and dipolar branches having different charge-transfer characters are investigated: photophysical properties are studied and TPA spectra are determined through two-photon excited fluorescence experiments using fs pulses in the 700-1000 nm range. Calculations based on time-dependent quantum-chemical approaches, as well as the Frenkel exciton model, complement experimental findings. Experiments and theory reveal that a multidimensional intramolecular charge transfer takes place from the central electron-donating moiety to the periphery of the branched molecules upon excitation, whereas fluorescence stems from a dipolar branch. Symmetry and inter-branch electronic coupling are found to be responsible for amplification of the TPA response of branched compounds with respect to their monomeric analogues. In particular, an enhancement is observed in regions where the TPA bands overlap, and TPA activation is obtained in spectral regions where the dipolar analogue is almost two-photon transparent. Thus, appropriate tuning of the number of branches, of the coupling between them, and modulation of intramolecular charge transfer from core to periphery open the way for substantial improvement of TPA efficiency or TPA induction in desired spectral regions