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Shiv Nadar University

(SoNS) School of Natural Sciences

Chemistry

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Crystal Growth and Design

Erratum: Experimental and theoretical charge density analysis of polymorphic structures: The case of coumarin 314 dye (Crystal Growth and Design (2010) 10 (1516) DOI: 10.1021/cg900649m)

The effect of the substitution of one Cu2+ ion (S=1/2) by Mg2+ ion (S=0) on the magnetic property of the linear-chain spin trimer compound Ca3 Cu3 (PO4) 4 was studied using dc magnetic susceptibility in Ca3 Cu2 Mg (PO4) 4 together with those in Ca3 Cu3 (PO4) 4 and Ca3 Cu2 Ni (PO4) 4 for comparison. A remarkable difference is observed among the results obtained in the Mg and the Ni substituted compounds. A clear signature of the reduction in the net spin of the trimers in Ca3 Cu2 Mg (PO4) 4 was found below 65 K, which is compatible with the presence of the Cu2-Cu1-Mg trimers in the singlet ground state, together with those of the type Cu2-Cu1-Cu2 and Mg-Cu1-Mg in the doublet state. However, no signature of the reduction in the net spin of the trimers was observed in Ca3 Cu2 Ni (PO4) 4. This finding suggests that the type of trimers present in Ca3 Cu2 Mg (PO4) 4 and Ca3 Cu2 Ni (PO4) 4 are different. Furthermore, a singlet ground state is partially realized in a quantum spin trimer system Ca3 Cu2 Mg (PO4) 4. {\textcopyright} 2010 The American Physical Society.

Physics

Physical Review B - Condensed Matter and Materials Physics

Magnetic properties of the spin trimer compound Ca3 Cu 2 Mg ( PO4 ) 4 from susceptibility measurements

P 31 nuclear-magnetic-resonance (NMR) studies have been performed in trimer spin chain compound Ca3 CuNi2 (PO4) 4, in the temperature range 4-300 K. In the range 16-300 K, the spectrum corresponds to a typical overlap of two powder patterns, consistent with two inequivalent phosphorous sites, having different shift parameters. A comparison of the isotropic hyperfine field (H hf iso) and the axial part (H hf ax) obtained in the paramagnetic phase of Ca3 CuNi2 (PO4) 4, with those obtained in Ca3 Cu3 (PO4) 4, suggest a stronger interchain exchange interaction in Ca3 CuNi2 (PO4) 4, which is possibly the reason for the higher antiferromagnetic transition temperature in Ca3 CuNi2 (PO4) 4. The temperature dependence of the spin-lattice relaxation rate (1/ T1) shows a clear signature of long-range magnetic order in Ca3 CuNi2 (PO4) 4 below 16 K (TN). TN agrees quite satisfactorily with that obtained from the derivative of the molar susceptibility versus T plot. The NMR line shape below TN shows the signature of a considerable distribution of the internal magnetic field in the ordered state with the existence of two magnetic sublattices with opposite direction of polarization with respect to the direction of the external magnetic field. A comparison of the behavior of the 1/ T1 data in Ca3 CuNi2 (PO4) 4 with those in Sr3 Cu3 (PO4) 4 clearly suggests that the mechanism of the relaxation changes from a two magnon-mediated Raman process in the former to a three magnon-mediated process in the latter. {\textcopyright} 2010 The American Physical Society.

NMR study of a magnetic phase transition in Ca3 CuNi2 ( PO4 ) 4: A spin trimer compound

Physical Review B

Energetics and electronic structure of phenyl-disubstituted polyacetylene: A first-principles study

The PT-symmetric complexi?ed Scarf II potential V(x) =-V 1sech2 x + iV2sechx tanh x, V1 &gt; 0, V2 ≠= 0, is revisited to study the interplay among its coupling parameters. The existence of an isolated real and positive energy level that has recently been identfied as a spectral singularity or zero-width resonance is here demonstrated through the behaviour of the corresponding wavefunctions and some property of the associated pseudo-norms is pointed out. We also construct four different rationally extended supersymmetric partners to V(x), which are PT-symmetric or complex non-PT-symmetric according to the coupling parameters range. A detailed study of one of these partners reveals that SUSY preserves the V(x) spectral singularity existence. © 2010 IOP Publishing Ltd.

Fulltext

Journal of Physics A: Mathematical and Theoretical

An update on the PT-symmetric complexified Scarf II potential, spectral singularities and some remarks on the rationally extended supersymmetric partners

We have used in situ low-energy electron microscopy (LEEM) to correlate the atomic and electronic structure of graphene films on polycrystalline Ni with nm-scale spatial resolution. Spatially resolved electron scattering measurements show that graphene monolayers formed by carbon segregation do not support the π-plasmon of graphene, indicating strong covalent bonding to the Ni. Graphene bilayers have the Bernal stacking characteristic of graphite and show the expected plasmon loss at 6.5 eV. The experimental results, in agreement with first-principles calculations, show that the π-band structure of free-standing graphene appears only in films with a thickness of at least two layers and demonstrate the sensitivity of the plasmon loss to the electronic structure. © 2010 American Chemical Society.

ACS Nano

Spatially-resolved structure and electronic properties of graphene on polycrystalline Ni

Three new transition metal complexes using 2-pyrimidineamidoxime (pmadH2) as multidentate chelating and/or bridging ligand have been synthesized and characterized. The ligand pmadH2 has two potential bridging functional groups [$\mu$-O and $\mu$-(N-O)] and consequently shows several coordination modes. While a polymeric 1D CuII complex [Cu(pmadH2)2(NO3)](NO3) (1) was obtained upon treatment of Cu(NO3)2{\textperiodcentered}3H2O with pmadH2 at room temperature in the absence of base, a high temperature reaction in the presence of base yielded a tetranuclear Cu II-complex [Cu4(pmad)2(pmadH) 2(NO3)](NO3)(H2O) (2). One of the CuII centers is in a square pyramidal environment while the other three are in a square planar geometry. Reaction of the same ligand with an equimolar mixture of both Cu(NO3)2{\textperiodcentered}3H2O and NiCl2{\textperiodcentered}6H2O yielded a tetranuclear heterometallic CuII2NiII2 complex [Cu2Ni2(pmad)2(pmadH)2Cl 2]{\textperiodcentered}H2O (3) containing both square planar (Ni II) and square pyramidal (CuII) metal centers. Complexes 1-3 represent the first examples of polynuclear metal complexes of 2-pyrimidineamidoxime. The analysis of variable temperature magnetic susceptibility data of 2 reveals that both ferromagnetic and antiferromagnetic interactions exist in this complex (J1 = +10.7 cm-1 and J2 = -2.7 cm-1 with g = 2.1) leading to a resultant ferromagnetic behavior. Complex 3 shows expected antiferromagnetic interaction between two CuII centers through -N-O- bridging pathway with J 1 = -3.4 cm-1 and g = 2.08. DFT calculations have been used to corroborate the magnetic results. {\textcopyright} 2010 The Royal Society of Chemistry.

Dalton Transactions

Use of 2-pyrimidineamidoxime to generate polynuclear homo-/heterometallic assemblies: Synthesis, crystal structures and magnetic study with theoretical investigations on the exchange mechanism

Reaction of formamide with Ni(NO3)2{\textperiodcentered}6H 2O under hydrothermal condition in a mixture of MeOH/H2O forms a two-dimensional formate bridged sheet Ni(HCOO)2(MeOH) 2 (1). X-ray structure analysis reveals the conversion of formamide to formate which acts as a bridging ligand in complex 1 where the axial sites of Ni(II) are occupied by methanol used as a solvent. An analogous reaction in presence of 4,4′-bipyridyl (4,4′-bipy) yielded a three-dimensional structure Ni(HCOO)2(4,4′-bpy) (2). DC magnetic measurements as a function of temperature and field established the presence of spontaneous magnetization with Tc (Curie temperature) = 17 and 20.8 K in 1 and 2, respectively, which can be attributed due to spin-canting. DFT calculations were performed to corroborate the magnetic results of 1 and 2. {\textcopyright} 2010 Elsevier Ltd. All rights reserved.

Polyhedron

A formate bridged Ni(II) sheet and its 3D analogue in presence of a linear organic linker: Synthesis, crystal structure and magnetic properties

The crystal structures and magnetic properties of five new transition metal-azido complexes with two anionic [pyrazine-2-carboxylate (pyzc) and p-aminobenzoate (paba)] and two neutral [pyrazine (pyz) and pyridine (py)] coligands are reported. All five complexes were synthesized by solvothermal methods. The complex [Co2(pyzc)2(N3) 2(H2O)2]n (1) is 1D and exhibit canted antiferromagnetism, while the 3D complex [MnNa(pyzc)(N3) 2(H2O)2]n (2) has a complicated structure and is weakly ferromagnetic in nature. [Mn2(paba) 2(N3)2(H2O)2] n (3), is a 2D sheet and the MnII ions are found to be antiferromagnetically coupled. The isostructural 2D complexes [Cu 3(pyz)2(N3)6]n (4) and [Cu3(py)2(N3)6]n (5) resemble remarkably in their magnetic properties exhibiting moderately strong ferromagnetism. Density functional theory calculations (B3LYP functional) have been performed to provide a qualitative theoretical interpretation of the overall magnetic behavior shown by these complexes. {\textcopyright} 2010 The Royal Society of Chemistry.

A series of transition metal-azido extended complexes with various anionic and neutral co-ligands: Synthesis, structure and their distinct magnetic behavior

The development of new high yielding cultivars of good quality with large berry size is the main objective of seedless grape breeding programme. Seedless grapes suffer from stenospermocarpy so, technique of embryo rescue employing in-ovulo culture has been adopted in grape breeding in western world which not only produce superior seedless cultivars but also curtails 7-8 years from entire breeding cycle. With respect to mean ovule age (days after pollination) and ovule-embryo growth (2.13 mm2), culturing of ovules 24 days after pollination was found to be the best. The concentration of IAA (4 mg/l) + GA3 (0.5 mg/l) proved to be most effective for germination (13.84 %). Among various media used for culturing, ovules on MS medium (1/2 macro + 1/1 micro) registered highest germination (13.75%). Chilling treatment was proved to be one of the important factors for embryo maturation and 60 days of chilling treatment at 4°C was found better than 45 days. With respect to the effect of different growth regulators on various rooting and shooting parameters IBA (1.0 mg/l) and NAA (1.5 mg/l) were found superior. While comparing different hardening strategies, glass jar with polypropylene cap (GPP) was found to be most effective as far as hardening success (66.67%) was concerned.