Anchi Yu

Room-temperature fluorescence, phosphorescence and crystal structures of 4-acyl pyrazolone lanthanide complexes: Ln(L)3·2H2O

Abstract A series of ternary mixed ligand 4-acyl pyrazolone lanthanide complexes: Ln(L)3·2H2O [where Ln = Tb3+ or Gd3+, L = 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 (PMAP), 1-phenyl-3-methyl-4-propionyl-5-pyrazolone (PMPP), 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone (PMIP), 1-phenyl-3-methyl-4-neovaleryl-pyrazolone-5 (PMNP) and 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP)] were synthesized and characterized by FT-IR spectra, UV-vis spectra and DTA-TG analysis. Room-temperature phosphorescence was observed from the Gd3+ complexes by excitation of the sample with the fourth harmonic frequency of a Nd: YAG laser beam (γ = 266 nm) and the triplet energies of the pyrazolone ligands were evaluated. Both the fluorescence intensity and fluorescence lifetime of the Tb3+ complexes depend on the structure of the ligands and explanations are presented. The crystal structure [Tb(PMPP)3·2H2O]·EtOH was determined by X-ray diffraction. The structure was refined to R = 0.064 (Rw = 0.073). The complex is mononuclear and the central terbium ion is coordinated by eight oxygen atoms to form a square-antiprism coordination polyhedron, six of which are from the three bidentate pyrazolone ligands and the other two are from the two coordination water molecules.

Ultrafast Photoinduced Electron Transfer between Tetramethylrhodamine and Guanosine in Aqueous Solution

Photoinduced electron transfer based fluorescence correlation spectroscopy (PET-FCS) is a powerful tool to study biomolecular processes. However, some questions remain as to how to correctly interpret the PET-FCS data. In this work, we studied the PET process between tetramethylrhodamine and guanosine by means of femtosecond transient absorption spectroscopy. We derived that the charge separation rate is 4.1 × 10(9) s(-1) and the charge recombination rate is 5.2 × 10(10) s(-1) for the current system, supporting the three-state model and the interpretation on PET-FCS experiments given by Qu et al. (J. Phys Chem. B, 2010, 114, 8235). At the limit that both the charge separation and recombination rates are much faster than the process that PET-FCS reveals, the three-state model can be simplified to an equivalent two-state model with a dark state whose brightness is nonzero. We propose ways to obtain the brightness of the dark state with additional experiments, which is necessary for a PET-FCS study.

Microcavity Effect from a Novel Terbium Complex Langmuir-Blodgett Film**

By Yanyi Huang, Anchi Yu, Chun-Hui Huang,*Liangbing Gan, Xinsheng Zhao, Yong Lin, and Bei ZhangThe use of microcavities as optical resonators has re-cently been developed as a potential high-density lightsource for optical communications and color displays. Theelectromagnetic field of microcavities can be enhanced sig-nificantly, and the spontaneous emission of the materials inthe cavity can be modified. The fundamental principle ofthe cavity effect has long been known but novel phenom-ena in microcavities are still attracting scientists’ attention,in terms of both theory and experiments.

Photophysical properties of Atto655 dye in the presence of guanosine and tryptophan in aqueous solution.

Atto655 has been widely used as an excellent probing dye through photoinduced electron transfer (PET) for biochemical processes in oligonucleotides or polypeptides. However, its photophysical properties in the presence of the quenchers guanosine and tryptophan have not been carefully studied. In this work, we investigated the dynamics of PET between Atto655 and the two quenchers in aqueous solution with femtosecond transient absorption experiments. We derived that the charge separation rate is 8.1 × 10(9) s(-1) and the charge recombination rate is 7.7 × 10(10) s(-1) for the collision complex between Atto655 and guanosine and that the corresponding values for the collision complex between Atto655 and tryptophan are 4.0 × 10(11) and 5.0 × 10(12) s(-1), respectively. These experimental results are quite consistent with the prediction of Marcus-type theory for electron transfer. The implications of this work for the data analysis of PET-based fluorescence correlation spectroscopy are discussed.

The investigation of second harmonic generation from novel molecules [(E)-N-alkyl-4-{2-[4-(dialkylamino)phenyl]ethenyl}pyridazinium iodide]

(E)-N-Methyl-4-{2-[4-(dihexadecylamino)phenyl]ethenyl}pyridazinium iodide (MHPd), (E)-N-octadecyl-4-{2-[4-(dimethylamino)phenyl]ethenyl}pyridazinium iodide (OMPd), (E)-N-octadecyl-4-{2-[4-(diethylamino)phenyl]ethenyl}pyridazinium iodide (OEPd), (E)-N-octadecyl-4-{2-[4-(dibutylamino)phenyl]ethenyl}pyridazinium iodide (OBPd) have been designed and synthesized. Their Langmuir–Blodgett film forming properties and second harmonic generation were studied. According to the results observed, MHPd is the best among the four congeners. By comparing the NLO properties of OMPd with those of a known compound, OMPy [(E)-N-octadecyl-4-{2-[4-(dimethylamino)phenyl]ethenyl}pyridinium iodide], the impairing effect of the second nitrogen in the six-membered pyridazine ring was examined experimentally and theoretically.

Ionic combined nonlinear optical bis-chromophore zinc complexes : Langmuir-Blodgett film and second harmonic generation study

Abstract Two novel ionic combined amphiphilic nonlinear optical bis-chromophore zinc complexes: bis(E)-[2-(4-dimethylaminophenyl)ethenyl]-1-octadecyl pyridinium bis (2-thione-1,3-dithiol-4,5-dimercapto)zinc (3) and bis(E)-[2-(4-dimethyl amino phenyl) ethenyl]-1-octadecyl quinolinium bis (2-thione-1,3-dithiol-4,5-dimercapto) zinc (4) were synthesized by combining a bis-negatively charged zinc complex anion: bis (2-thione-1,3-dithiol-4,5-dimercapto) zinc with a hemicyanine cation (E)-[2-(4-dimethylamino phenyl) ethenyl]-1-octadecyl pyridinium (1) or a quinoline modified hemicyanine (E)-[2-(4-dimethyl amino phenyl) ethenyl]-1-octadecyl quinolinium (2). Their Langmuir films at the air/water interface, the transfer of the Langmuir films to form LB films and the vertical homogeneity of the LB films were investigated. The Langmuir films of the bis-chromophore complexes are more stable than their corresponding dye iodides. Strong second-order nonlinearities from the LB monolayers were observed and the second-order susceptibilities (χzzz(2)) were evaluated to be 230 pm V−1 for 3 and 330 pm V−1 for 4, which were 1.9 or 1.7 times that of the corresponding dye iodide.

The subtle role of heteroaromatics in the second-order susceptibility in a series of amphiphilic styryl dye Langmuir–Blodgett films

A series of amphiphilic styryl dyes: 2-(4-dihexadecylaminostyryl) benzothiazole methiodide (BTM), 2-(4-dihexadecylaminostyryl) benzoxazole methiodide (BOM), and 2-(4-dihexadecylaminostyryl) benzimidazole methiodide (BIM), were synthesized; their monolayers were successfully deposited on quartz slides by the Langmuir–Blodgett technique and formed H aggregates. Second-order susceptibilities χzzz(2) of the monolayers were determined with a polarized laser beam (Nd:YAG, λ=1.064 μm). The values of χzzz(2) are 215, 132, and 67 pm V−1 for BTM, BOM and BIM, respectively. Charge distributions over the entire molecules for the dye models were calculated using the MINDO/3 method in the MOPAC 7.0 program. Experimental data and semiempirical quantum chemical calculation results show that electron deficiencies of the heteroaromatic rings play an important role in determining the second harmonic generation of organic dye LB films.

Dissecting Multivalent Lectin–Carbohydrate Recognition Using Polyvalent Multifunctional Glycan-Quantum Dots

Multivalent protein–carbohydrate interactions initiate the first contacts between virus/bacteria and target cells, which ultimately lead to infection. Understanding the structures and binding modes involved is vital to the design of specific, potent multivalent inhibitors. However, the lack of structural information on such flexible, complex, and multimeric cell surface membrane proteins has often hampered such endeavors. Herein, we report that quantum dots (QDs) displayed with a dense array of mono-/disaccharides are powerful probes for multivalent protein–glycan interactions. Using a pair of closely related tetrameric lectins, DC-SIGN and DC-SIGNR, which bind to the HIV and Ebola virus glycoproteins (EBOV-GP) to augment viral entry and infect target cells, we show that such QDs efficiently dissect the different DC-SIGN/R-glycan binding modes (tetra-/di-/monovalent) through a combination of multimodal readouts: Förster resonance energy transfer (FRET), hydrodynamic size measurement, and transmission electron microscopy imaging. We also report a new QD-FRET method for quantifying QD-DC-SIGN/R binding affinity, revealing that DC-SIGN binds to the QD >100-fold tighter than does DC-SIGNR. This result is consistent with DC-SIGN’s higher trans-infection efficiency of some HIV strains over DC-SIGNR. Finally, we show that the QDs potently inhibit DC-SIGN-mediated enhancement of EBOV-GP-driven transduction of target cells with IC50 values down to 0.7 nM, matching well to their DC-SIGN binding constant (apparent Kd = 0.6 nM) measured by FRET. These results suggest that the glycan-QDs are powerful multifunctional probes for dissecting multivalent protein–ligand recognition and predicting glyconanoparticle inhibition of virus infection at the cellular level.

Langmuir-Blodgett Films and Second-Order Nonlinear Optical Property of a Phthalocyanine-Fullerene Dyad

Abstract The Langmuir-Blodgett films of a new copper phthalocyanine-fullerene dyad were fabricated. Its second harmonic gernation property from the films were studied.

Second Harmonic Generation in Langmuir-Blodgett Films of a Novel Phenylhydrazone Dye

Abstract The LB films of a new phenylhydrazone dye, 4-hexadecanoxynaphthyl-4′-nitro phenylhydrazone, were prepared. The second harmonic generation (SHG) from monolayer and multilayers of the dye was measured. The dependence of SHG on number of layers is weaker than the expected square law.