Partha Pratim Jana

A combined experimental and computational study of supramolecular assemblies in ternary copper(II) complexes with a tetradentate N-4 donor Schiff base and halides

Three new copper(II) complexes, [Cu(L)(Cl)]ClO4 (1), [Cu(L)(Br)]ClO4 (2) and [Cu(L)(I)]ClO4 (3), have been prepared from a tetradentate symmetrical Schiff base, N,N′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L), and characterized by elemental analysis, IR and UV-Vis spectroscopy and single-crystal X-ray diffraction studies. Extended supra-molecular networks were generated through different weak non-covalent forces. Density functional theory (DFT) calculations were employed to estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The interplay between the anion–π and π–π interactions is also analyzed and a mutual reinforcement of both interactions is demonstrated. The assignment of the contribution of each interaction and its mutual influence is certainly important to shed light on the delicate mechanism that governs the molecular recognition and crystal packing.

Structures of NiCd6+δ (−0.32 ≤ δ ≤ 0.35) – a γ-brass related phase, and NiCd1+δ (0 ≤ δ ≤ 0.05) – a Ti2Ni type phase in the nickel–cadmium system

The crystal structures of the binary cadmium-rich complex metal alloys NiCd6+δ (−0.32 ≤ δ ≤ 0.35) and NiCd1+δ (0 ≤ δ ≤ 0.05) were studied by means of single crystal X-ray diffraction. The partitioning of the NiCd6+δ structure into clusters grouped around all 16 high symmetry points of the face centered cubic cell leads to the identification of two partial structures forming replicas of two disjointed, interpenetrating, zinc blende-type nets. In one partial structure the nodes are NiTi2-type Ni4Cd18 and bcc-type NiCd26 clusters. This substructure is ordered and compositionally more or less invariant in the whole homogeneity range with the fixed composition Ni5Cd44. The complementary substructure varies in composition and exhibits vacancy, substitutional and positional disorders. The structure of NiCd1+δ (0 ≤ δ ≤ 0.05) can be described by a 34-atom Ti2Ni-type cluster.

Lanthanide(III) morpholine 4-dithiocarbamate complexes: Pr(III) derivative shows first example of polymeric lanthanide(III) dithiocarbamate

Three lanthanide(III) morpholine 4-dithiocarbamate complexes [Ln(Phen)(Mph-Dtc)3]·xCH2Cl2 [Ln = Pr (1), Nd (2) and Eu (3); Mph-Dtc = morpholine 4-dithiocarbamate; x = 2 (1) or 1 (2, 3)] have been prepared from the reaction of the potassium salt of morpholine 4-dithiocarbamate with lanthanide nitrates and phenanthroline. Complexes 1–3 were characterized by various analytical techniques and their solid state structures were established by single crystal X-ray diffraction analysis. The Ln(III) ions are nine or eight coordinated in 1 and 2, 3 respectively. Interestingly, oxygen atom of one of the three coordinated Mph-Dtc ligands is further coordinated to a Pr(III) ion of the adjacent molecule. Thus, it results in the formation of an one-dimensional (1D) polymeric structure. Thermal stability and optical properties of 1–3 have been investigated.

Site preference and ordering induced by Au substitution in the γ-brass related complex Au-Cr-Zn phases.

The crystal chemistry of the ternary Au-Cr-Zn alloy was studied by means of synthesis, single crystal X-ray diffraction, and electron structure calculations. While the compound CrZn(∼17) represents the binary end-point of the homogeneity range, the inclusion of Au proves to be very site specific, and at the limiting composition Au10Cr4Zn89 the structure is completely ordered. The crystallographic site occupancy pattern calculated by the Local Density Approximation (LDA)-Density Functional Theory (DFT) parametrized extended Hückel (eH) Mulliken charge populations in Au10Cr4Zn89 agrees very well with the experimentally found site occupancy pattern.

AuCd4: a Hume-Rothery Phase with VEC of 1.8 and icosahedral and trigonal-prismatic clusters as building blocks.

The η phase in the Au-Cd binary system has been synthesized, and the structure has been analyzed by single-crystal X-ray diffraction. The compound η-AuCd(4) crystallizes in the hexagonal space group P6(3)/m (No. 176). The unit cell contains ∼273 atoms. The compound AuCd(4) represents a √3a × √3a × c superstructure of the AgMg(4) type. The structure can be well described by icosahedral and trigonal-prismatic clusters. A phase transition to the high-temperature ε phase occurs exothermically at around 578 K. The compound is formed at a sharp valence electron concentration of 1.8 e/a. The compound can be understood within the framework of the Hume-Rothery stabilization mechanism.

Structural Impact of Platinum on the Incommensurably Modulated γ-Brass Related Composite Structure Pd(15)Zn(54).

The crystal structure of three incommensurately modulated γ-brass related composite structures in the Pd-Zn-Pt system has been solved from X-ray single crystal diffraction data using a 3 + 1-dimensional super space description. The compounds Pt(x)Pd(15-x)Zn(54) (x ≈ 6, 7, 10) crystallize in orthorhombic superspace group Fmmm(α00)0s0 (F = [(1/2, 1/2, 0, 0); (1/2, 0, 1/2, 0); (0, 1/2, 1/2, 0)] with the following fundamental cell dimensions: a = 4.265(1) Å, b = 9.132(1) Å, c = 12.928(2) Å, q ≈ 0.629a*; a = 4.284(1) Å, b = 9.151(2) Å, c = 12.948(4) Å, q ≈ 0.628a*; and a = 4.288(1) Å, b = 9.140(4) Å, c = 12.926(7) Å, q ≈ 0.627a*. Each structure is built by two sub-lattices-pentagonal antiprismatic columns parallel to [100] and a zigzag chain of Zn atoms running along the center of the column.

Variation in crystalline architectures through supramolecular interactions in copper(II) complexes with tridentate N2O donor Schiff bases

Three copper(II) complexes, [Cu(L1)(H2O)(ClO4)]·0.5H2O (1), [Cu(L2)(H2O)(ClO4)]·0.5H2O (2), and [Cu(L2)(NCNC(OCH3)NH2)]ClO4 (3), where HL1 = 4-bromo-2-(-(quinolin-8-ylimino)methyl)phenol and HL2 = 1-(-(quinolin-8-ylimino)methyl)naphthalen-2-ol, have been prepared and characterized by elemental analysis, IR, UV–vis and fluorescence spectroscopy and single-crystal X-ray diffraction studies. The copper(II) centers assume five-coordinate square-pyramidal geometries in 1 and 2, whereas square planar copper(II) is present in 3. A methanol molecule has been inserted in the pendant end of the ligated dicyanamide in 3. Various supramolecular architectures are formed by hydrogen bonding, π⋯π, C–H⋯π, and lp⋯π interactions. Graphical abstract

γ-Brass related complex phases in Rh–Cd binary system

γ-brasses are a class of Hume-Rothery phases that attract recent attention due to their structurally complex close relation with quasicrystals (QCs) and challenges toward understanding the underlying stabilisation mechanism. A signature characteristic of the γ-phase field in many binary systems is that it accommodates a phase-bundle with exceptional compositional and structural complexities. The cubic γ-brass phase is stabilised ideally at valance electron concentration (VEC = total number of valence electrons/atoms) = 21/13 (1.615) e/a, and variations of VEC from this ideal value result in structural modifications. γ-brasses are reported between the VEC values of 1.59 and 1.77 e/a. In the course of this research program, I have been studying the γ-brass field of Rh-Cd binary system to identify all γ-brass related phases and to elucidate their crystal structures. It was previously reported that in analogy to some other related systems, a cubic γ-brass-type phase may exist in the Rh-Cd binary system. Our investigation has uncovered three new γ-brass related phases in the Rh-Cd binary system: γ-Rh8Cd43, which adopts a rhombohedral variant of a cubic giant cell structure, a monoclinic phase which is identified at approximately 15 atomic % of Rh, and a very complex cubic phase at approximately 11 atomic % of Rh. In this presentation, I will discuss crystal structures and electronic structure of γ-brass related phases in the RhCd binary system.

Thermoelectric properties of new Co–Sb–Se system

Energy is the linchpin for the growth of every developing country. To address the global energy supply, power conservation and energy management, generation of electricity from waste-heat resources attains more consideration. Developing and deploying affordable energy solutions and implementation of new energy technologies will develop society to achieve extraordinary affluence. Thermoelectric (TE) materials can directly convert the waste heat into electrical energy, which have the impending play in energy preservation and power generation [1]. The efficacy of the thermoelectric materials is often assessed by dimensionless figure of merit ZT = σS2/κelec+ κlat, where σ is the electrical conductivity, S is the Seebeck coefficient (thermopower), κelec is the electronic part of thermal conductivity and κlatt is the lattice part of the thermal conductivity.

Y-brass related composite structures : a (3+1)-dimensional space description

The γ-brass Hume-Rothery [1] phases which adopt at VEC values near about 21/13 presently attract attention due to their structural complexity and challenge for the understanding of the underlying stabilization mechanism. Morton, by electron microscopy studies, revealed that the γ-brass regions of Cu-Zn, Ni-Zn and Pd-Zn do not only accommodate the γ-brass phase but also a bundle of structurally related, complex phases with lower symmetry than that of the γ-phase. A bundle of γ-brass related phases in the Zn-rich region of the Ni-Zn, Pd-Zn, Pt-Zn phase diagram is investigated. Their structures have been refined from single crystal X-ray diffraction data in the conventional 3D space group using supercells [2,3]. In the course of a previous investigation of the Pd-Zn system, the structures of two γ-brass related composite compoundsPd24.3Zn75.7 and Pd21.2Zn78.8 have been described with the (3+1) dimensional space description (superspace group Xmmm(00γ)0s0 with the following lattice parameters, a = 12.929(3) Å, b = 9.112(4) Å, c = 2.5631(7) Å, q = 8/13 c* and a = 12.909(3) Å, b = 9.115(3) Å, c = 2.6052(6) Å, q = 11/18 c*, respectively) [3]. The aim of this study is to represent the structure of these previously reported phases in a coherent, modulated description to make them more readily comparable. A refinement model with a variety of modulation vectors allows to refine any intergrowth structure in the Zn rich region of the M-Zn (M=Ni,Pd,Pt) system. In order to gain an insight into expressions, cause and mechanism and structurecomposition relationship for such phases, we also study the impact of substitution on the evolution of the structure of ternary derivatives of M-Zn composite compounds by the use of (3+1) formalism. For instance, substitution of zero-valent palladium and bivalent zinc by zero-valent platinum in the structure of Pd24.3Zn75.7. This presentation will discuss about the understanding of the complexity of the atomic arrangement through the various modulation which correlates with the variation of composition of the binary and ternary phases.