A water-dispersible PEGylated conjugated oligomer (PEGTVFVBN) is synthesized for two-photon fluorescence imaging applications. PEGTVFVBN could aggregate into nanoparticles of ~ 110 nm size in H 2 O , which show a fluorescence quantum yield of 0.12, 20 times higher than that for its cationic counterpart (TVFVBC). Two-photon fluorescence measurement reveals a maximum two-photon absorption (TPA) cross-section of 263 GM at 780 nm based on molecules for PEGTVFVBN nanoparticles in H 2 O , while the TPA spectra of TVFVBC are barely detectable under the same experimental conditions. The N , N' -diacetylchitobiotic acid conjugated derivative (ChPEGTVFVBN) could also aggregate into nanoparticles of ~ 90 nm sizes, showing a slightly smaller fluorescence quantum yield of 0.08 and a maximum TPA cross-section of 213 GM at 780 nm. ChPEGTVFVBN could be specifically internalized by vimentin over expressing Hela cells through a receptor mediated endocytosis, giving two-photon fluorescence images in a bright and high contrast manner. In addition, both PEGTVFVBN and ChPEGTVFVBN show low cytotoxicity, which is essential for cell imaging applications. This study thus highlights the molecular engineering strategy of PEGylation to construct robust TPA materials for two-photon fluorescence imaging applications.

A methylene bridge link connecting the ortho-positions within the triphenylamine scaffold increases the molecular planarity significantly. The one-photon spectroscopies of bridged triphenylamine molecules show considerable extended conjugation relative to their triphenylamine counterparts, leading to enhanced two-photon absorption (TPA) cross-sections. Various substituents at the scaffold have been prepared and studied. Using a femtosecond laser source Z-scan method, the TPA cross-sections were characterized. The maximum magnitude of the TPA cross-section is ∼4800 GM, which is four times that of its triphenylamine counterpart.

Near-infrared (NIR) absorption in the range of 0.75-2.5 mm is in great demand for a variety of applications but currently the majority of commercial NIR devices are based on inorganic materials due to the limited number of organic materials that are active in this range. Here we present the preparation and optical studies of a new series of stable azulene-containing NIR chromophores whose absorption can be tuned in the range of 0.6-1.7 mu m. DFT calculation revealed that the protonation-induced low excitation gap was attributable to the substantial intramolecular charge transfer.

A water-dispersible orange emitter (Pyrene4BTF–PEG–TAT) containing pyrene as the donor core and benzothiadiazole as the acceptor is synthesized through click chemistry for one- and two-photon fluorescence imaging application. Pyrene4BTF–PEG–TAT has an emission maximum at 586 nm in water with a large Stokes shift of 181 nm. It self-assembles into nanoparticles with diameters of ∼190 nm in water. The nanoparticles have a fluorescence quantum yield of 0.11 and a two-photon absorption (TPA) cross-section of 512 GM at 820 nm based on molecule. Pyrene4BTF–PEG–TAT could be effectively internalized by HeLa cells to show bright red fluorescence upon both one- and two-photon excitation. The successful demonstration of the first water-dispersible pyrene-based TPA material will trigger more research on developing red emitters for bioimaging applications.

A phenylacetylene macrocycle (PAM) derivative containing triphenylamine as the framework was synthesized in one-step Sonogashira coupling. The photophysical and electrochemical properties were investigated in details. This hexamer shows significant enhancement in two-photon absorption cross-section relative to reported PAM derivatives.

A glucopyranose functionalized star-shaped oligomer, N-tris{4,4',4''-[(1E)-2-(2-{(E)-2-[4-(benzo[d]thiazol-2-yl)phenyl]vinyl}-9,9-bis(6-2-amido-2-deoxy-1-thio-β-D-glucopyranose-hexyl)-9H-fluoren-7-yl)vinyl]phenyl}phenylamine (TVFVBN-S-NH(2)), is synthesized for two-photon fluorescence imaging. In water, TVFVBN-S-NH(2) self-assembles into nanoparticles with an average diameter of ∼49 nm and shows a fluorescence quantum yield of 0.21. Two-photon fluorescence measurements reveal that TVFVBN-S-NH(2) has a two-photon absorption cross-section of ∼1100 GM at 780 nm in water. The active amine group on the glucopyranose moiety allows further functionalization of TVFVBN-S-NH(2) with folic acid to yield TVFVBN-S-NH(2) FA with similar optical and physical properties as those for TVFVBN-S-NH(2). Cellular imaging studies reveal that TVFVBN-S-NH(2) FA has increased uptake by MCF-7 cells relative to that for TVFVBN-S-NH(2), due to specific interactions between folic acid and folate receptors on the MCF-7 cell membrane. This study demonstrates the effectiveness of glycosylation as a molecular engineering strategy to yield water-soluble materials with a large two-photon absorption (TPA) cross-section for targeted cancer-cell imaging.

Two bridged-triphenylamine starburst molecules were designed and synthesized. Their electrochemical properties were studied in detail using cyclic voltammetry (CV) and square wave voltammetry (SWV) methods. The bridged molecular structure stabilizes the oxidative state and decreases the oxidation potentials, resulting in an increased HOMO energy level. Double-layer sandwich electroluminescence devices were fabricated. The bridged triphenylamine starburst 4 has shown significantly enhanced performance compared with the triphenylamine analog 3 and its ethenyl-linked derivative 6.

Spider webs are made of silk, the properties of which ensure remarkable efficiency at capturing prey. However, remaining on, or near, the web exposes the resident spiders to many potential predators, such as ants. Surprisingly, ants are rarely reported foraging on the webs of orb-weaving spiders, despite the formidable capacity of ants to subdue prey and repel enemies, the diversity and abundance of orb-web spiders, and the nutritional value of the web and resident spider. We explain this paradox by reporting a novel property of the silk produced by the orb-web spider Nephila antipodiana (Walckenaer). These spiders deposit on the silk a pyrrolidine alkaloid (2-pyrrolidinone) that provides protection from ant invasion. Furthermore, the ontogenetic change in the production of 2-pyrrolidinone suggests that this compound represents an adaptive response to the threat of natural enemies, rather than a simple by-product of silk synthesis: while 2-pyrrolidinone occurs on the silk threads produced by adult and large juvenile spiders, it is absent on threads produced by small juvenile spiders, whose threads are sufficiently thin to be inaccessible to ants.

A star-shaped glycosylated conjugated oligomer, 4,4',4 "-tris(4-(2-(4-(benzo-[d]thiazol-2-yl)phenyl)-9,9'-bis(6-thiol-beta-D-glucose)-hexyl)-fluoren-7-yl)phenylamine (TFBS), is synthesized for two-photon fluorescence imaging of live cells. The high density of hydrophilic sugar side groups induces self-assembly of TFBS into nanoparticles in water with an average diameter of 61 nm. Because of the self-assembled nanostructure, TFBS has a higher quantum yield in water (Phi = 0.10), compared to its cationic counterpart, 4,4',4 "-tris(4-(2-(4-(benzo[d]thiazol-2-yl)phenyl)-9,9'-bis(6-N,N,N-trimethylammonium)-hexyl)-fluoren-7-yl)phenylamine (TFBC) (Phi = 0.03). In addition, TFBS has a large TPA cross section (delta(max)) of similar to 1200 GM at 740 nm in aqueous media, which is significantly higher than that for TFBC. TFBS can be effectively internalized by the human cervical cancer cell line and accumulates in the cytoplasm, allowing for live cell two-photon fluorescence imaging upon 800-nm excitation. TFBS has also shown low cytotoxicity, which is essential for in vitro and in vivo cellular imaging and other clinical applications. This study demonstrates the significant advantages of glycosylation in molecular engineering of water-soluble fluorescent molecules for two-photon fluorescence imaging applications.

1,5- and 1,8-bis(bifluorenyl)anthracene were synthesized and converted to their corresponding bis(bifluorenyl)triptycenes and bis(bifluorenyl)-9,10-dihydroanthracenes. Analysis of their optical properties shows no feature of extended conjugation in the triptycene pair. The electronic spectra of the triptycene and dihydroanthracene pairs are in fact superimposable. There is definite evidence that triptycene displays zero homoconjugation effect.

A neutral (1N) and a cationic (1C) bridged-triphenylamine tetramer with large two-photon absorption (TPA) cross sections of 4340 GM ( 1N toluene) and 4150 GM (1C in methanol) were synthesized.

Triphenylamine derivatives bridged by methylene units afford a near planar molecular platform in a series of one dimer and two oligomers exhibiting increased structural rigidity compared to that of their parent triphenylamines. This series of dendrimers show significantly enhanced two-photon absorptions that are up to 3-fold that of triphenylamines with similar molecular size and structure.

Two derivatives (X=Cl, CN) of 1,2-ditolylnaphthalene were prepared as models to investigate their conformational behavior that could involve rotation of either of the tolyl rings. The existence of anti and syn atropisomers was evident from their 1H NMR spectra at room temperature indicating two pairs of well-resolved singlets for the methyl protons. Dynamic 1H NMR studies estimated the rotation barrier to be about 76–82kJmol−1, a value consistent with selective rotation of the 2-tolyl ring in the conformation inter-conversion.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

One dihydropyrene-thiophene and a series of three dihydropyrene-phenylenevinylene copolymers were synthesized in this work. The core dihydropyrene unit was shown to remain intact in the polymer backbone by H-1 NMR studies. Thermal studies indicated higher stability of the dihydropyrene unit in the copolymers compared with the parent molecule, with one of the dihydropyrene-phenylenevinylene copolymers exhibited a single-step onset degradation temperature at 400 degrees C. Extended conjugation effect in the copolymers was evident based on spectroscopic analysis despite a mismatch of macrocyclic dihydropyrene units and small conjugation partners (thiophene and phenylenevinylene). The copolymers exhibited relatively small bandgaps. All four copolymers exhibit blue light emission in photoluminescence studies. Their emission spectra are essentially identical, suggesting that their emission properties were dominated by the dihydropyrene chromophore but independent of the spacer group (thiophene or phenylenevinylene). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1795-1803, 2009

Incorporation of π electron-rich dihydropyrene units into the polymer backbone of polythiophene afforded a conducting polymer with narrow bandgap energy of about 1.0eV. Doping of this polymer with iodine showed an optimum conductivity of about 1.0Scm−1. The quinoid character and a small highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) separation in the dihydropyrene are believed to account for the observed semi-conducing properties of this dihydropyrene–thiophene copolymer. The dihydropyrene unit in the copolymer was found to exhibit a significantly higher thermal stability than the parent molecule.

High-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations were used to investigate the attachment of allyl and propargyl alcohols on Si(1 1 1)-7×7 under ultra-high vacuum conditions. The HREELS spectra of chemisorbed allyl alcohol (AA) show the concurrent appearance of characteristic stretching vibrations of Si−H (2104 cm−1) and Si−O (795 cm−1) coupled with the retention of vibrational features of CC stretching (1657 cm−1) and (sp2)C−H stretching (3012 and 3102 cm−1). These results clearly demonstrate the dissociative reaction nature via the hydroxyl group for the chemisorption of AA on Si(1 1 1)-7×7, which was further supported by XPS and DFT studies. A similar reaction pathway was found for propargyl alcohol (PA) adsorbed on the same Si(1 1 1)-7×7 surface. Our studies suggest that OH dissociation is highly favorable compared to [2+2]-like cycloadditions via CC/CC for organic reactions on silicon surfaces, which may be explained by the large spatial separation between the adjacent adatom-rest atom pair on Si(1 1 1)-7×7.

A dithiacyclophane was employed as a precursor to the title compound. A conformational study of the dithiacyclophane revealed a unique phenomenon in its terphenyl unit: one ring is rigidly held, the other terminal ring undergoes free rotation and the central ring exhibits restricted mobility. The aromatic protons of the biphenyl unit are all shielded by the dihydropyrene unit and well resolved in the H-1 NMR spectrum, consistent with a ring current effect extended to eight conjugated carbon atoms away from the molecular plane of dihydropyrene. (C) 2008 Elsevier Ltd. All rights reserved.

Regioselectivity for the 5,8,15,18-substituted isomer over the 5,8,14,17-isomer was observed in a series of mercaptan–bromide coupling reactions leading to the formation of 2,11-dithia[3.3]paracyclophanes. Their molecular assembly was established by X-ray crystallographic studies. In the crystal packing of these paracyclophanes, several types of non-covalent interactions including halogen–halogen interaction, halogen-bonding interaction, weak hydrogen-bonding interaction, etc. are observed in crystals 3a, 3b and 3c. There is evidence to indicate that weak non-covalent Br…Br, Br…S, Br…N, C–H…S, S…S and C–H…N interactions play an important role in governing their molecular assembly assumed in the solid state. The attractive interactions of Br…Br, Br…S and Br…N are also rationalised and supported in terms of the density functional theory calculations.