Lie symmetries and solitons in nonlinear systems with spatially inhomogeneous nonlinearities

Using Lie group theory and canonical transformations, we construct explicit solutions of nonlinear Schr?dinger equations with spatially inhomogeneous nonlinearities. We present the general theory, use it to show that localized nonlinearities can support bound states with an arbitrary number solitons, and discuss other applications of interest to the field of nonlinear matter waves.     

Tunable control of the frequency correlations of entangled photons

We experimentally demonstrate a new technique to control the type of frequency correlations of entangled photon pairs generated by spontaneous parametric downconversion. Frequency-correlated and frequency-anticorrelated photons are produced when a broadband pulse is used as a pump. The method is based on the control of the group velocities of the interacting waves and can be applied in any nonlinear medium and frequency band of interest.     

Robust Inclusion Complexes of Crown Ether Fused Tetrathiafulvalenes with Li+@C60 to Afford Efficient Photodriven Charge Separation

Inclusion complexes of benzo‐ and dithiabenzo‐crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li⁺@C₆₀ ( 1? Li⁺@C₆₀ and 2? Li⁺@C₆₀). The strong complexation has been quantified by high binding constants that exceed 10⁶ M ^?1 obtained by UV/Vis titrations in benzonitrile (PhCN) at room temperature. On the basis of DFT studies at the B3LYP/6‐311G(d,p) level, the orbital interactions between the crown ether moieties and the π surface of the fullerene together with the endohedral Li⁺ have a crucial role in robust complex formation. Interestingly, complexation of Li⁺@C₆₀ with crown ethers accelerates the intersystem crossing upon photoexcitation of the complex, thereby yielding ³(Li⁺@C₆₀)*, when no charge separation by means of ¹Li⁺@C₆₀* occurs. Photoinduced charge separation by means of ³Li⁺@C₆₀* with lifetimes of 135 and 120 μs for 1? Li⁺@C₆₀ and 2? Li⁺@C₆₀, respectively, and quantum yields of 0.82 in PhCN have been observed by utilizing time‐resolved transient absorption spectroscopy and then confirmed by electron paramagnetic resonance measurements at 4 K. The difference in crown ether structures affects the binding constant and the rates of photoinduced electron‐transfer events in the corresponding complex.     

Peripherally and Axially Carboxylic Acid Substituted Subphthalocyanines for Dye‐Sensitized Solar Cells

A series of subphthalocyanines (SubPcs) bearing a carboxylic acid group either at the peripheral or axial position have been designed and synthesized to investigate the influence of the COOH group positions on the dye‐sensitized solar cell (DSSC) performance. The DSSC devices based on SubPcs with axially substituted carboxylic acid groups showed low photovoltaic performance, whereas peripherally substituted one exhibited higher power conversion efficiency owing to improved injection from LUMO of SubPcs to the TiO₂ conduction band.     

An Efficient and Modular Route to Sequence‐Defined Polymers Appended to DNA

Inspired by biological polymers, sequence‐controlled synthetic polymers are highly promising materials that integrate the robustness of synthetic systems with the information‐derived activity of biological counterparts. Polymer–biopolymer conjugates are often targeted to achieve this union; however, their synthesis remains challenging. We report a stepwise solid‐phase approach for the generation of completely monodisperse and sequence‐defined DNA–polymer conjugates using readily available reagents. These polymeric modifications to DNA display self‐assembly and encapsulation behavior—as evidenced by HPLC, dynamic light scattering, and fluorescence studies—which is highly dependent on sequence order. The method is general and has the potential to make DNA–polymer conjugates and sequence‐defined polymers widely available.     

Mechanically Interlocked Single‐Wall Carbon Nanotubes

Extensive research has been devoted to the chemical manipulation of carbon nanotubes. The attachment of molecular fragments through covalent‐bond formation produces kinetically stable products, but implies the saturation of some of the C? C double bonds of the nanotubes. Supramolecular modification maintains the structure of the SWNTs but yields labile species. Herein, we present a strategy for the synthesis of mechanically interlocked derivatives of SWNTs (MINTs). In the key rotaxane‐forming step, we employed macrocycle precursors equipped with two π‐extended tetrathiafulvalene SWNT recognition units and terminated with bisalkenes that were closed around the nanotubes through ring‐closing metathesis (RCM). The mechanically interlocked nature of the derivatives was probed by analytical, spectroscopic, and microscopic techniques, as well as by appropriate control experiments. Individual macrocycles were observed by HR STEM to circumscribe the nanotubes.     

Synthesis and characterization of palladium(II) complexes [PdX2(p-diben)] (X = Cl,Br, I,N3, or NCO; p-diben = N,N′-bis(4-dimethylaminobenzylidene)ethane-1,2-diamine): crystal structure of [Pd(N3)2(p-diben)]

Five new complexes of general formula [PdX₂(p-diben)], where p-diben = N,N′-bis(4-dimethylaminobenzylidene)ethane-1,2-diamine) (1) and X = Cl (2), Br (3), I (4), N₃ (5), or CNO (6), were synthesized and characterized by physicochemical and spectroscopic methods. The crystal structure of compound (5) was determined by single-crystal X-ray diffraction. Complexes 2–6 were characterized as N,N-chelated products. The crystal structure confirmed this formulation for [Pd(N₃)₂(p-diben)], besides showing the isomerism inversion of one of the C=N bonds, caused by Pd(II) coordination.