Interaction of free functional group with platinum(II) center in cyclometalated complexes: A structural and photophysical property investigation

A series of flexible multidentate ligands containing N,P-donor, 2-[N-(diphenylphosphino)methyl]amino-pyridine (L¹), 2-[N-bi-(diphenylphosphino) methyl]amino-pyridine (L²), 2-[N-(diphenylphosphino)methyl]amino-7-methyl-1,8-naphthyridine (L³) and 4-[(N-diphenylphosphino)methyl]amino-pyridine) (L⁴) have been synthesized. The mono- and dinuclear cyclometalated platinum(II) complexes [Pt(C^N^N)L¹]ClO₄ (HC^N^N = 6-phenyl-2,2′-bipyridine), [Pt₂(C^N^N)₂L¹](ClO₄)₂, [Pt₂(C^N^N)₂L²](ClO₄)₂, [Pt(C^N^N)L³]ClO₄ and [Pt₂(C^N^N)₂L⁴](ClO₄)₂ were prepared and their structures determined by X-ray crystal analysis. These complexes exhibit long-lived bright orange emissions ranging from 560 to 610 nm in the solid state at room temperature. In solution, dinuclear complexes have emissions with higher quantum yields than mononuclear complexes. This can be attributed to intramolecular interaction of free functional group with Pt(II) at axial position, resulting in the quenching of phosphorescence for platinum(II) complexes in the ³MLCT excited state.     

A Bootstrap Procedure for Adaptive Selection of the Test Statistic in Flexible Two‐Stage Designs

Adaptive two‐stage designs allow a data‐driven change of design characteristics during the ongoing trial. One of the available options is an adaptive choice of the test statistic for the second stage of the trial based on the results of the interim analysis. Since there is often only a vague knowledge of the distribution shape of the primary endpoint in the planning phase of a study, a change of the test statistic may then be considered if the data indicate that the assumptions underlying the initial choice of the test are not correct. Collings and Hamilton proposed a bootstrap method for the estimation of the power of the two‐sample Wilcoxon test for shift alternatives. We use this approach for the selection of the test statistic. By means of a simulation study, we show that the gain in terms of power may be considerable when the initial assumption about the underlying distribution was wrong, whereas the loss is relatively small when in the first instance the optimal test statistic was chosen. The results also hold true for comparison with a one‐stage design. Application of the method is illustrated by a clinical trial example.     

Crystal engineering of mixed-ligand frameworks: Ligand-directed assembly and structural diversity

Four new coordination networks based on dipyridyl linkages 2,6-(N,N′-di(4-pyridyl)amino)pyridine (dpap) or 1,3-bis(4-pyridyl)propane (bpp) and different dicarboxylates have been synthesized and structurally characterized. Using dpap to react with two different dicarboxylates, maleic acid (H₂mal) and 4,4′-sulfonyldibenzoate (H₂sdba), respectively, two different two-dimensional (2D) coordination polymers of Cd(II), [Cd(dpap)(mal)]_n (1) and {[Cd(dpap)(sdba)] · 2H₂O}_n (2) were obtained. Compound 1 features a 42-membered bimetallic macrocyclic structural motif which is extended by mal groups to form a 2D network. In the case of 2, two different layers can be achieved depending on the conformation of sdba. The layer has a (8²10) net topology with Cd as nodes and dpap, sdba bridges as the connectors. The overall structure of {[Mn(dpap)(sdba)] · 1.5H₂O}_n (3) similar to that of 2 despite the presence of different metal ions. When dpap was replaced by bpp to react with Co(NO₃)₂ · 6H₂O, another 1D coordination polymer, {[Co(bpp)(H₂O)₄] · sdba}_n(4) was constructed. The 1D chains join sdba to make an overall 3D supramolecular architecture by hydrogen-bonding interactions ( (22), (12)). The Cd coordination polymers exhibit strong solid-state luminescence emission at room temperature. Thermal stability of these crystalline materials has been explored by thermogravimetric analysis of mass loss.     

Coordination network solids based on Cu(II) coordination compounds with 1,4-bis-(1,2,4-triazol-1-yl)-butane as a flexible alkyl spacer ligand: Synthesis, characterization and X-ray structures

The coordination chemistry of three selected copper(II) salts with the flexible ligand 1,4-bis(1,2,4-triazol-1-yl)butane (abbreviated as btb) is described. This ligand acts as a bidentate ligand, bridging copper(II) ions, thereby generating polymers in 2D and 3D network solids.     

The role of 4,4′-trimethylene-dipyridine flexibility in the construction of hybrid networks templated on aromatic alcohols

A series of zinc phosphite hybrid structures with trimethylene dipyridine as the linking ligand and templated on the aromatic alcohols, hydroquinone, 1,2,3-trihydroxybenzene, nitrophenol, and bromophenol are reported. The aromatic alcohols interact with the framework by hydrogen bonding to oxygen atoms that bridge zinc and phosphorus atoms in the inorganic portion of the network. In addition, three hydrogen-bonded networks that contain trimethylene-dipyridine and either hydroquinone or 1,2,3-trihydroxybenzene are reported. In these structures, the aromatic alcohol acts as a hydrogen bond donor to trimethylene-dipyridine. The flexibility of trimethylene-dipyridine is important to the construction of the new frameworks. Calculations using PM5 parameters demonstrate that trimethylene-dipyridine can adopt a wide variety of conformations with a minimal energy expense.     

全软成形环与缘对缘瓣膜成形术在心脏瓣膜关闭不全成形术中的疗效比较

目的:观察和比较全软成形环与缘对缘瓣膜成形术在心脏瓣膜关闭不全成形术中的疗效。方法:回顾性研究我院行心脏瓣膜关闭不全成形术患者80例,随机分为Ⅰ组与Ⅱ组,每组各40例。第Ⅰ组患者在行心脏瓣膜关闭不全成形术中使用全软成形环进行治疗,第Ⅱ组患者在手术过程进行缘对缘瓣膜成形术。比较治疗前后两组患者二尖瓣口、二尖瓣环面积和收缩期及舒张期二尖瓣环周径、左心室内径、心搏出量、射血速率、射血时间及临床有效率。结果:治疗后,两组二尖瓣形态、左心室内经、心搏出量、射血速率及射血时间均较治疗前有所改善(P0.05);且与第Ⅱ组相比,第Ⅰ组患者二尖瓣口面积、心搏出量及射血速率较大,二尖瓣环的面积、收缩期及舒张期二尖瓣环周径、左心室内径较小,射血时间明显缩短(P0.05)。第Ⅱ组治疗总有效率为95%,较第Ⅰ组(62.5%)显著升高,差异具有统计学意义(P0.05)。结论:与缘对缘瓣膜成形术相比,全软成形环在心脏瓣膜关闭不全成形术中的疗效更好,其机制可能与增大二尖瓣口面积、心搏出量及射血速率,减小二尖瓣环的面积、收缩期及舒张期二尖瓣环周径、左心室内径,缩短射血时间有关。     

Extended dissimilarity: a method of robust estimation of ecological distances from high beta diversity data

It is widely accepted that reliable ordination of ecological data requires a strong linear or ordinal relationship between the dissimilarity of sites, based on species composition, and the ecological distance between them. Certain dissimilarity measures, having the property that they take a fixed maximum value when sites have no species in common, have been shown to be strongly correlated with ecological distance. For ecological gradients of moderate length (moderate beta diversity), such measures, in conjunction with non-metric multidimensional scaling, will reliably yield successful ordinations. However, as beta diversity increases, more sites have no species in common, and such measures invariably under-estimate ecological distance for such sites. Thus ordinations of data with high species turnover (high beta diversity) may fail.Extended dissimilarities are defined using an iterative adaptation of flexible shortest path adjustment applied to the matrix of dissimilarities with fixed maximum values. By means of theoretical argument and simulations, this is shown to lead to far stronger correlations between the adjusted site dissimilarity and ecological distance for ecological gradients of greater length than previously considered. Hence ordinations of extended dissimilarities, by means of either metric or non-metric scaling techniques, are shown to outperform corresponding ordinations of unadjusted dissimilarities, with the difference increasing with increasing beta diversity.     

Structural variations in copper(I) iodide coordination polymers of sulfide and disulfide containing flexible 3-substituted pyridine ligands

The three-substituted dipyridyl ligand bis(3-pyridylmethyl)sulfide (L¹) was prepared by the reaction of 3-(chloromethyl)pyridine hydrochloride with thioacetamide under basic conditions. L¹ was reacted with CuI to give complexes with 1:2 and 1:1 molar ratios. Crystal structures of [(CuI)₂(L¹)]_∞ (1) and [CuI(L¹)]_∞ (2) were determined. In complex 1 the CuI species formed a one-dimensional staircase polymer to which L¹ was bound in a side-by-side fashion with π-π interactions between the ligands on each side. Complex 2 consisted of a one-dimensional ribbon polymer of metallomacrocycles formed from two L¹ ligands bridging Cu₂I₂ dimers which were fused within the macrocyclic ring. The analogous disulfide ligand bis(3-pyridylmethyl)disulfide (L²) was prepared by oxidation of the corresponding thiol 3-(sulfanylmethyl)pyridine. L² was reacted with CuI in 1:2 and 1:1 molar ratios and products isolated but only the 1:1 product was able to be crystallised. The crystal structure of [CuI(L²)]_∞ (3) consisted of a one-dimensional ribbon polymer of metallomacrocycles formed from two L² ligands linked through Cu₂I₂ dimers. The difference in the metallomacrocycle linking between the related structures 2 and 3 was attributed to the difference in ligand conformation.