Integrable wide-free-spectral-range Fabry-Perot optical filters using free-standing LiNbO3 thin films

We demonstrate the use of free-standing thin films of a complex oxide for chip-scale optical filtering. The films are used as low-order etalons with very large free spectral ranges that exceed 6.78 THz (> 50 nm at 1550 nm) and use a small chip area (< 500 microm2) when they are integrated. The films are produced by crystal ion slicing; this process exfoliates a micrometers-thin layer of single-crystal optical material from a bulk parent by means of high-energy-ion implantation. The etalons, which are 10 microm thick with Ag deposited on both surfaces, are integrated into a silica-on-silicon waveguide block.     

Unexpected formation of a cyclic vinylene sulfate in the synthesis of ethynyl-substituted acenes

(E)-2-Styrylanthracene derivatives containing triisopropylsilylacetylene groups at the 9 and 10 positions were synthesized and characterized. The electronic properties have been studied by DFT calculations, spectroscopy and electrochemistry, revealing asymmetric resonance stabilization effects that result in the regioselective formation of an unusual cyclic vinylene sulfate.     

Synthesis,spectroscopic characterization,crystal structure and theoretical investigation of two azo-palladium (II) complexes derived from substituted (1-phenylazo)-2-naphtol

Transition Metal Chemistry - The ortho-substituted (E)-1-((2-methoxyphenyl)diazenyl)naphthalen-2-ol and the meta-substituted (E)-1-((3-methoxyphenyl)diazenyl)naphthalen-2-ol were, respectively,...     

Adiabatic invariants for dynamical systems with one degree of freedom

Adiabatic invariants for dynamical systems with one degree of freedom, whose equation of motion is (1), and where the existence of the corresponding Hamilton action integral is not imposed, are established. The adiabatic invariants may vary according to their structure. Using the theory a few particular problems, including non-autonomous Duffing and Van der Pol oscillators, are analysed. Finally, it is indicated how the adiabatic invariants can be used for finding approximate solutions, stability analyses and for plotting phase curves.     

Vibrationally induced two-level systems in single-molecule junctions

Single-molecule junctions are found to show anomalous spikes in dI/dV spectra. The position in energy of the spikes is related to local vibration mode energies. A model of vibrationally induced two-level systems reproduces the data very well. This mechanism is expected to be quite general for single-molecule junctions. It acts as an intrinsic amplification mechanism for local vibration mode features and may be exploited as a new spectroscopic tool.     

Chiral "metallo-spiralenes": helical molecules conformationally stabilised by an organometallic scaffold

The synthesis of a series of chiral cyclomanganated 2-[(eta 6-phenyl)-Cr(CO)3]pyridine complexes derived from (-)-beta-pinene enables, by a "spirogenic transformation", the preparation of four different chiral helical heterobimetallic syn-facial complexes or Cr0/Mn1-spiralenes, among which two possess a right-handed P molecular helicity and two other a left-handed M one. These organometallic helical molecules are synthesised by applying two different methods to the chiral cyclomanganated (eta 6-arene)tricarbonylchromium substrates. The first method is the so-called "Fischer route" which involves a sequential addition of PhLi and MeOTf. The second method based on reaction of the cyclomanganated complex with diphenyldiazomethane which has been tested on achiral bimetallic substrates is a reasonable neutral alternative to the "Fischer methodology" for the synthesis of Cr0/Mn1-spiralenes. The crystal structure of one of these heterobimetallic chiral helical compounds serves as a starting point in the configurational and structural assessment of the synthesised chiral (eta 6-arene)tricarbonylchromium complexes. Application of the "Fischer route" to a cyclomanganated chiral 2-phenylpyridine generates a single chiral eta 3-benzylic complex--or Mn1-spiralene--bearing a left-handed M helicity which has been characterized by X-ray diffraction analysis. Circular dichroic spectroscopic measurements underline the predominant contribution of the chiral and chirally induced aromatic chromophores to the sign of the Cotton effects and confirm the helical configurations of the considered heterobimetallic species.     

Synthesis of Planar Chiral Iridacycles by Cationic Metal π‐Coordination: Facial Selectivity,and Conformational and Stereochemical Consequences

Facial selectivity during the π‐coordination of pseudo‐tetrahedral iridacycles by neutral (Cr(CO)₃), monocationic (Cp*Ru⁺), and biscationic (Cp*Ir²⁺) metal centers was directly influenced by the coulombic imbalance in the coordination sphere of the chelated Ir center. We also showed by using theoretical calculations that the feasibility of the related metallacycles that displayed metallocenic planar chirality was dependent to the presence of an electron‐donating group, such as NMe₂, which contributed to the overall stability of the complexes. When the π‐bonded moiety was the strongly electron‐withdrawing Cp*Ir²⁺ group, the electron donation from NMe₂ resulted in major conformational changes, with a barrier to rotation of about 17 kcal mol^?1 for this group that became spectroscopically diastereotopic (high‐field ¹H NMR spectroscopy). This peculiar property is proposed as a means to introduce a new type of constitutional chirality at the nitrogen center: planar chirality at tertiary aromatic amines.     

Highly conductive molecular junctions based on direct binding of benzene to platinum electrodes

Highly conductive molecular junctions were formed by direct binding of benzene molecules between two Pt electrodes. Measurements of conductance, isotopic shift in inelastic spectroscopy, and shot noise compared with calculations provide indications for a stable molecular junction where the benzene molecule is preserved intact and bonded to the Pt leads via carbon atoms. The junction has a conductance comparable to that for metallic atomic junctions (around 0.1-1G0), where the conductance and the number of transmission channels are controlled by the molecule's orientation at different interelectrode distances.