A Series of Cu^II-Azide Polymers of Cu₆ Building Units and the Role of Chelating Diamine in Controlling their Dimensionality: Synthesis, Structures, and Magnetic Behavior

Four new neutral copper-azido polymers [Cu6(N3)12(aem)2]n(1), [Cu6(N3)12(dmeen)2(H2O)2]n (2), [Cu6(N3)12(N,N′-dmen)2]n (3), and [Cu6(N3)12(hmpz)2]n (4) [aem = 4-(2-aminoethyl)morpholine; dmeen = N,N-dimethyl-N′-ethylethylenediamine; N,N′-dmen = N,N′-dimethylethylenediamine and hmpz = homopiperazine] have been synthesized by using 0.33 mol equiv of the chelating diamine ligands with Cu(NO3)2·3H2O/CuCl2·2H2O and an excess of NaN3. Single crystal X-ray structures show that the basic unit of these complexes, especially 1−3, contains very similar CuII6 building blocks. But the overall structures of these complexes vary widely in dimensionality. While 1 is three-dimensional (3D) in nature, 2 and 3 have a two-dimensional (2D) arrangement (with different connectivity) and 4 has a one-dimensional (1D) structure. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in all the four complexes. The experimental susceptibility data have been analyzed by some theoretical model equations

A Series of Cu^II-Azide Polymers of Cu₆ Building Units and the Role of Chelating Diamine in Controlling their Dimensionality: Synthesis, Structures, and Magnetic Behavior

Four new neutral copper-azido polymers [Cu6(N3)12(aem)2]n(1), [Cu6(N3)12(dmeen)2(H2O)2]n (2), [Cu6(N3)12(N,N′-dmen)2]n (3), and [Cu6(N3)12(hmpz)2]n (4) [aem = 4-(2-aminoethyl)morpholine; dmeen = N,N-dimethyl-N′-ethylethylenediamine; N,N′-dmen = N,N′-dimethylethylenediamine and hmpz = homopiperazine] have been synthesized by using 0.33 mol equiv of the chelating diamine ligands with Cu(NO3)2·3H2O/CuCl2·2H2O and an excess of NaN3. Single crystal X-ray structures show that the basic unit of these complexes, especially 1−3, contains very similar CuII6 building blocks. But the overall structures of these complexes vary widely in dimensionality. While 1 is three-dimensional (3D) in nature, 2 and 3 have a two-dimensional (2D) arrangement (with different connectivity) and 4 has a one-dimensional (1D) structure. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in all the four complexes. The experimental susceptibility data have been analyzed by some theoretical model equations

Mixed Azide and 5-(Pyrimidyl)tetrazole Bridged Co(II)/Mn(II) Polymers: Synthesis, Crystal Structures, Ferroelectric and Magnetic Behavior

The reaction of pyrimidine-2-carbonitrile, NaN3 in the presence of Co(NO3)2·6H2O or MnCl2·4H2O leads to the formation of complexes [Co(pmtz)(μ1,3-N3)(H2O)]n (1) and [Mn(pmtz)(μ1,3-N3)(H2O)]n (2) respectively, under hydrothermal condition [pmtz =5-(pyrimidyl)tetrazolate]. These two complexes have been fully characterized by single crystal X-ray diffraction. Complex 1 crystallizes in a non-centrosymmetric space group Aba2 in the orthorhombic system and is found to exhibit ferroelectric behavior, whereas complex 2 crystallizes in the P21/c space group in the monoclinic system. Variable temperature magnetic characterizations in the temperature range of 2−300 K indicate that complex 1 is a canted antiferromagnet (weak ferromagnet) with Tc = 15.9 K. Complex 1 represents a unique example of a multiferroic coordination polymer containing tetrazole as a co-ligand. Complex 2 is a one-dimensional chain of Mn(II) bridged by a well-known antiferromagnetic coupler end-to-end azido ligand. In contrast to the role played by the end-to-end azido pathway in most of the transition metal complexes, complex 2 showed unusual ferromagnetic behavior below 40 K because of spin canting

Self-Assembly of a Nanoscopic Prism via a New Organometallic Pt₃ Acceptor and Its Fluorescent Detection of Nitroaromatics

A nanoscale-sized cage with a trigonal prismatic shape is prepared by coordination-driven self-assembly of a predesigned organometallic Pt3 acceptor with an organic clip-type ligand. This trigonal prism is fluorescent and undergoes efficient fluorescence quenching by nitroaromatics, which are the chemical signatures of many explosives

Mixed Azide and 5-(Pyrimidyl)tetrazole Bridged Co(II)/Mn(II) Polymers: Synthesis, Crystal Structures, Ferroelectric and Magnetic Behavior

The reaction of pyrimidine-2-carbonitrile, NaN3 in the presence of Co(NO3)2·6H2O or MnCl2·4H2O leads to the formation of complexes [Co(pmtz)(μ1,3-N3)(H2O)]n (1) and [Mn(pmtz)(μ1,3-N3)(H2O)]n (2) respectively, under hydrothermal condition [pmtz =5-(pyrimidyl)tetrazolate]. These two complexes have been fully characterized by single crystal X-ray diffraction. Complex 1 crystallizes in a non-centrosymmetric space group Aba2 in the orthorhombic system and is found to exhibit ferroelectric behavior, whereas complex 2 crystallizes in the P21/c space group in the monoclinic system. Variable temperature magnetic characterizations in the temperature range of 2−300 K indicate that complex 1 is a canted antiferromagnet (weak ferromagnet) with Tc = 15.9 K. Complex 1 represents a unique example of a multiferroic coordination polymer containing tetrazole as a co-ligand. Complex 2 is a one-dimensional chain of Mn(II) bridged by a well-known antiferromagnetic coupler end-to-end azido ligand. In contrast to the role played by the end-to-end azido pathway in most of the transition metal complexes, complex 2 showed unusual ferromagnetic behavior below 40 K because of spin canting

Self-Assembly of a Nanoscopic Prism via a New Organometallic Pt₃ Acceptor and Its Fluorescent Detection of Nitroaromatics

A nanoscale-sized cage with a trigonal prismatic shape is prepared by coordination-driven self-assembly of a predesigned organometallic Pt3 acceptor with an organic clip-type ligand. This trigonal prism is fluorescent and undergoes efficient fluorescence quenching by nitroaromatics, which are the chemical signatures of many explosives

Image Comparison Based On Local Pixel Clustering

Image comparison is a fundamental step for monitoring images and has wide applications in many disciplines of sciences, including satellite imaging, medical research, quality control and so forth. This problem, however, is complicated because (i) the observed images often contain noise, (ii) the image intensity functions are discontinuous and have spatial structures. In the literature, a vast majority of the methods are intensity-based. However, such an approach is often questionable in real life situations where small changes in the background may not indicate an actual meaningful change in the images as long as the boundaries of the image objects remain the same. In this article, we propose a flexible and effective image comparison method based on local pixel clustering and construct a test statistic based on the Variation of Information metric. This is a feature based image comparison technique where edges or the jump points are considered as the primary features. Numerical examples and statistical properties show that the proposed image comparison method performs well in various real life scenarios.</p

Cu^II-Azide Polynuclear Complexes of Three Different Building Clusters with the Same Schiff-Base Ligand: Synthesis, Structures, Magnetic Behavior, and Density Functional Theory Studies

Three copper-azido complexes [Cu₄(N₃)₈(L¹)₂­(MeOH)₂]_<i>n</i> (<b>1</b>), [Cu₄(N₃)₈(L¹)₂] (<b>2</b>), and [Cu₅(N₃)₁₀(L¹)₂]_<i>n</i> (<b>3</b>) [L¹ is the imine resulting from the condensation of pyridine-2-carboxaldehyde with 2-(2-pyridyl)­ethylamine] have been synthesized using lower molar equivalents of the Schiff base ligand with Cu­(NO₃)₂·3H₂O and an excess of NaN₃. Single crystal X-ray structures show that the basic unit of the complexes <b>1</b> and <b>2</b> contains Cu^II₄ building blocks; however, they have distinct basic and overall structures due to a small change in the bridging mode of the peripheral pair of copper atoms in the linear tetranuclear structures. Interestingly, these changes are the result of changing the solvent system (MeOH/H₂O to EtOH/H₂O) used for the synthesis, without changing the proportions of the components (metal to ligand ratio 2:1). Using even lower proportions of the ligand, another unique complex was isolated with Cu^II₅ building units, forming a two-dimensional complex (<b>3</b>). Magnetic susceptibility measurements over a wide range of temperature exhibit the presence of both antiferromagnetic (very weak) and ferromagnetic exchanges within the tetranuclear unit structures. Density functional theory calculations (using B3LYP functional, and two different basis sets) have been performed on the complexes <b>1</b> and <b>2</b> to provide a qualitative theoretical interpretation of their overall magnetic behavior

Self-Assembly of Molecular Nanoball: Design, Synthesis, and Characterization

The design and self-assembly of two new flexible supramolecular nanoballs are described. These assemblies incorporate two flexible tritopic amide and ester building blocks and were prepared in excellent yields (96−97%) via coordination driven self-assembly. The first resulted from the reaction of 4 equiv of a new tritopic ester ligand N,N‘,N‘ ‘-tris(4-pyridylmethyl) trimesic ester and 3 equiv of C4 symmetric Pd(NO3)2. The second analogous structure was obtained by the self-assembly of a flexible N,N‘,N‘ ‘-tris(3-pyridylmethyl) trimesic amide and Pd(NO3)2. The assemblies were characterized with multinuclear NMR spectroscopy, electrospray ionization mass spectroscopy, elemental analysis, and TGA. Mass spectrometry along with NMR data and TEM view confirms the existence of the two assemblies. MM2 force field simulations of the cages showed a ball shape with the diameter of the inner cavity of about 2.1 and 1.8 nm for 2a and 2b, respectively, which were also corroborated by TEM analysis