Application of step-scan FTIR to the research of quantum cascade lasers

The principle of step-scan Fourier transform infrared (FTIR) spectroscopy is introduced. Double modulation step-scan FTIR technique is used to obtain the quantum cascade laser's stacked emission spectra in the time domain. Optical property and thermal accumulation of devices due to large drive current are analyzed.     

Synthesis,characterization, and properties of copolymer of acrylamide and complex pseudorotaxane monomer consisting of cucurbit[6]uril with butyl ammonium methacrylate

The novel copolymers of acrylamide (AM) with complex pseudorotaxane monomer (BAMACB) of butyl ammonium methacrylate (BAMA) and cucurbit[6]uril (CB[6]) were prepared via free‐radical polymerization in aqueous solution. The copolymers containing pseudorotaxane (PAM/BAMACB) were characterized by ¹H‐NMR, FTIR, elemental analysis, TGA, and DSC. The glass transition temperature (T_g) of the copolymer PAM/BAMACB are higher than that of the copolymer of acrylamide and butyl ammonium methacrylate (PAM/BAMA) because of the enhanced rigidity and the bulky steric hindrance of BAMACB side chain in PAM/BAMACB. The molecular weights of copolymer PAM/BAMACB were obtained via static light scattering. The hydrodynamic radii of coils or aggregates were investigated by dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5999–6008, 2008     

Majorana stellar representation for mixed-spin (s, 1/2) systems

By describing the evolution of a quantum state with the trajectories of the Majorana stars on a Bloch sphere,Majorana’s stellar representation provides an intuitive geometric perspective to comprehend the quantum system with highdimensional Hilbert space.However,the representation of a two-spin coupling system on a Bloch sphere has not been solved satisfactorily yet.Here,a practical method is presented to resolve the problem for the mixed-spin(s,1/2)system and describe the entanglement of the system.The system can be decomposed into two spins:spin-(s+1/2)and spin-(s?1/2)at the coupling bases,which can be regarded as independent spins.Besides,any pure state may be written as a superposition of two orthonormal states with one spin-(s+1/2)state and the other spin-(s?1/2)state.Thus,the whole initial state can be regarded as a state of a pseudo spin-1/2.In this way,the mixed spin decomposes into three spins.Therefore,the state can be represented by(2s+1)+(2s?1)+1=4s+1 sets of stars on a Bloch sphere.Finally,some examples are given to show symmetric patterns on the Bloch sphere and unveil the properties of the high-spin system by analyzing the trajectories of the Majorana stars on the Bloch sphere.     

Two new homoisoflavanones from Polygonatum odoratum (Mill.) Druce

<正>Two new homoisoflavanones were isolated from the rhizomes of Polygonatum odoratum(Mill.) Druce and their structures were elucidated as(3R)-5,7-dihydroxy-8-methoxy-3-(4-methoxybenzyl)-6-methylchrom-an-4-one(1) and(3R)-5,7,8-trihydroxy-3-(4- hydroxybenzyl)-6-methylchroman-4-one(2),on the basis of spectral analysis.     

Synthesis, photophysical and electrophosphorescent properties of fluorene-based platinum(II) complexes

A series of platinum(II) complexes bearing tridentate cyclometalated C^N^N (C^N^N=6-phenyl-2,2'-bipyridine and π-extended R-C^N^N=3-[6'-(naphthalen-2'-yl)pyridin-2'-yl]isoquinoline) ligands with fluorene units have been synthesised and their photophysical properties have been studied. The fluorene units are incorporated into the cyclometalated ligands by a Suzuki coupling reaction. An increase in the π-conjugation of the cyclometalated ligands confers favourable photophysical properties compared to the 6-phenyl-2,2'-bipyridine analogues. The fluorene-based platinum(II) complexes display vibronic-structured emission bands with λ(max)=558-601 nm, and high emission quantum yields up to 0.76 in degassed dichloromethane. Their emissions are tentatively assigned to excited states with mixed (3)IL/(3)MLCT parentage (IL=intraligand, MLCT=metal-to-ligand charge transfer). The crystal structures of these platinum(II) complexes reveal extensive Pt(II)···π and/or π-π interactions. The fluorene-based platinum(II) complexes are soluble in organic solvents, have high thermal stability with decomposition temperature >350 °C, and can be thermally vacuum-sublimed or solution-processed as phosphorescent dopants for the fabrication of organic light-emitting diodes (OLEDs). A monochromic OLED with 3d as dopant (2 wt%) fabricated by vacuum deposition gave a current efficiency of 14.7 cd A(-1) and maximum brightness of 27000 cd m(-2). A high current efficiency (9.2 cd A(-1)) has been achieved in a solution-processed OLED using complex 3f (5 wt%) doped in a PVK (poly(9-vinylcarbazole)) host.     

Ruthenium‐Catalyzed Alkylation of Indoles with Tertiary Amines by Oxidation of a sp3 C?H Bond and Lewis Acid Catalysis

Ruthenium porphyrins (particularly [Ru(2,6‐Cl₂tpp)CO]; tpp=tetraphenylporphinato) and RuCl₃ can act as oxidation and/or Lewis acid catalysts for direct C‐3 alkylation of indoles, giving the desired products in high yields (up to 82 % based on 60–95 % substrate conversions). These ruthenium compounds catalyze oxidative coupling reactions of a wide variety of anilines and indoles bearing electron‐withdrawing or electron‐donating substituents with high regioselectivity when using tBuOOH as an oxidant, resulting in the alkylation of N‐arylindoles to 3‐{[(N‐aryl‐N‐alkyl)amino]methyl}indoles (yield: up to 82 %, conversion: up to 95 %) and the alkylation of N‐alkyl or N‐H indoles to 3‐[p‐(dialkylamino)benzyl]indoles (yield: up to 73 %, conversion: up to 92 %). A tentative reaction mechanism involving two pathways is proposed: an iminium ion intermediate may be generated by oxidation of an sp³ C? H bond of the alkylated aniline by an oxoruthenium species; this iminium ion could then either be trapped by an N‐arylindole (pathway A) or converted to formaldehyde, allowing a subsequent three‐component coupling reaction of the in situ generated formaldehyde with an N‐alkylindole and an aniline in the presence of a Lewis acid catalyst (pathway B). The results of deuterium‐labeling experiments are consistent with the alkylation of N‐alkylindoles via pathway B. The relative reaction rates of [Ru(2,6‐Cl₂tpp)CO]‐catalyzed oxidative coupling reactions of 4‐X‐substituted N,N‐dimethylanilines with N‐phenylindole (using tBuOOH as oxidant), determined through competition experiments, correlate linearly with the substituent constants σ (R²=0.989), giving a ρ value of ?1.09. This ρ value and the magnitudes of the intra‐ and intermolecular deuterium isotope effects (k_H/k_D) suggest that electron transfer most likely occurs during the initial stage of the oxidation of 4‐X‐substituted N,N‐dimethylanilines. Ruthenium‐catalyzed three‐component reaction of N‐alkyl/N‐H indoles, paraformaldehyde, and anilines gave 3‐[p‐(dialkylamino)benzyl]indoles in up to 82 % yield (conversion: up to 95 %).