Multi-centred hydrogen bonds between water and perchlorate anion

Results of classical molecular dynamics simulations are presented for the re-orientational dynamics of water hydrogen bonded to perchlorate anion. Different mechanisms of bond formation are presented. Due to its regular tetrahedron geometry the perchlorate anion can make classical as well as bifurcated and trifurcated hydrogen bonds. The angular variation of water in the first solvation shell of perchlorate suggests the transitional character of multi-centred hydrogen bonds. As a result water molecules can slide around the anion.     

无溶剂一锅法Al(ClO_4)_3催化合成α-氨基膦酸酯

以无水高氯酸铝为催化剂,将芳香醛、芳香胺及亚磷酸酯在无溶剂条件下一锅法反应,高效地合成了α-氨基膦酸酯,该催化剂优于其它已发现的催化剂[如Mg(ClO4)2,BiCl3,AlCl3等],建立了一种适用于含有钝化基团的芳香胺的α-氨基膦酸酯的新合成方法.     

分光光度法测定水溶液中的有机酸含量

利用水溶液中的有机酸在高氯酸羟胺(HAP)和N,N′-二环己基碳酰亚胺(DCC)存在的条件下生成的羟肟酸,以及羟肟酸在酸性高氯酸铁溶液中显色的性质,建立了一种分光光度测定水中有机酸含量的方法。对显色剂的酸度、浓度、加入体积、HAP和DCC的浓度、加入体积以及显色反应的温度、反应时间对吸光度的影响进行了考察。结果表明,该显色反应在反应条件:0.0687mol/LHAP1.0mL、0.6mol/LDCC0.5mL、震荡均匀后室温下放置反应15min、0.02mol/L酸性高氯酸铁溶液(高氯酸浓度0.3mol/L)显色条件下具有最大的吸光度;并对正丁酸、正戊酸、苯甲酸进行了线性关系考察。结果表明,该检测方法具有仪器简单、操作方便、线性范围较宽、准确度高等优点,可用于那些不易从水溶液中萃取的有机酸的测定,也可用于液相色谱洗脱液中有机酸的测定。     

Zn[(L)Proline]2: an eligible candidate for the synthesis of xanthenediones in water

An efficient route for the condensation of aldehydes with dimedone in the presence of Zn[(L)Proline]₂ in water has been reported. Hydrophilicity of the catalyst is the main attribute of this reaction. The water‐mediated reaction using catalytic amounts of recyclable catalyst avoids the use of expensive, corrosive reagents and toxic solvents and provides operational simplicity. Moreover, column chromatography and recrystallization of product are not required as the crude products itself are very pure and hence can be used for target‐oriented synthesis on a large scale. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and biomimetic mineralization of l‐proline substituted polyphosphazenes as bulk and nanofiber

This work presents the synthesis of polyphosphazenes bearing L ‐proline methyl ester (ProOMe) and 4‐hydroxy‐l ‐proline methyl ester (HypOMe), aiming for new bioactive polymers for bone repair. The polymers were characterized by ¹H and ³¹P NMR, FTIR, DSC, and TGA. Electrospun fibers were prepared using poly[bis(l ‐proline methyl ester)phosphazene] (PProP), and their potential for biomimetic mineralization, as well as the bulk material, were tested in simulated body fluid (1×SBF). Samples were analyzed between 24 h and 3 weeks of incubation using SEM/EDS and FTIR. After 24 h, spherical and flower‐like shapes of calcium phosphates (CaP) were crystallized on the bulk samples. The nanofibers presented spherical CaP crystals attached to them after 48 h of incubation. The Ca/P molar ratio of the crystals varied from 1.5 to 1.6. According to this study, PProP presents bioactivity in vitro, and its fibers offer sites for CaP nucleation like the collagen fibers in bone. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1318–1327     

Is gadolinium a helical antiferromagnet or a collinear ferromagnet?

Controversial issues concerning the nature of magnetic ordering in gadolinium are briefly reviewed. The recent experimental results are shown to resolve most of such issues in that they rule out the possibility of a helical spin structure in Gd and clearly bring out the role of longrange dipolar interactions in stabilising collinear ferromagnetic order for temperatures between the spin-reorientation temperature and the Curie point Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India.     

Synthesis and Evaluation of GdIII‐Based Magnetic Resonance Contrast Agents for Molecular Imaging of Prostate‐Specific Membrane Antigen

Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate‐specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR‐based molecular imaging. We have synthesized three new high‐affinity, low‐molecular‐weight Gd^III‐based PSMA‐targeted contrast agents containing one to three Gd^III chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA‐based MR molecular imaging.     

UV Emission of Gd3+ in the Presence of Cu2+: Towards Luminescence Quenching through Quantum Cutting?

The first investigation into the ultraviolet (UV) photoluminescence of gadolinium(III) in the presence of copper(II) is reported. A melt‐quenched barium phosphate glass was used as a model matrix. The optical spectroscopy assessment shows that with increasing CuO concentration the Cu²⁺ absorption band grows steadily, whereas the UV emission from Gd³⁺ ions is progressively quenched. The data, thus, suggests the existence of a Gd³⁺→Cu²⁺ energy‐transfer process ocurring through quantum cutting. A downconversion/cross‐relaxation pathway proceeding through a virtual state in Gd³⁺ is proposed. These findings suggest gadolinium(III) could potentially be used in the optical sensing of copper(II).