A cyano-bridged bimetallic ferrimagnet: Synthesis, X-ray structure and magnetic study

Mixing of trans-[Mn(cyclam)Cl2]Cl (cyclam = 1,4,8,11-tetraazacyclotetradecane) and potassium hexacyanochromate (K3[Cr(CN)6]) aqueous solutions instantaneously yields a 1D infinite chain complex {[Mn(cyclam)(l-CN)2Cr(CN)4]� H2O}n (1). The crystal structure of 1, crystallizing in the monoclinic system with space group P21/n has been solved from X-ray powder diffraction data following direct space approach and refined by the Rietveld method. The structure analysis of 1 reveals alternating [Cr(CN)6] 3� and [Mn(cyclam)] 3+

Spin-crossover nanocrystals with magnetic, optical, and structural bistability near room temperature.

Pressure-induced hysteresis in the high spin \leftrightarrow low spin transition in bis(2,4-bis(pyridin-2-yl)thiazole) iron(II) tetrafluoroborate

Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz)2](BF4)2 have been carried out under hydrostatic pressures up to 9.13 kbar in the 5–300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS ↔ LS transition with T1/2 = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T1/2 and a slight decrease in the residual high spin fraction at low T . Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T1/2 the surpris…

Magnetic properties of quasi-2D antiferromagnet {N(n-C5H11)4[MnIIFeIII(ox)3]}∞ below Néel temperature: revisited

Abstract Magnetic measurements of {N(n-C 5 H 11 ) 4 [Mn II Fe III (ox) 3 ]} ∞ were carried out in the 5–300 K temperature range under different applied magnetic fields up to 50 kOe with zero-field-cooled (ZFC) and field-cooled (FC) modes. The FC and ZFC χ ( T ) plots exhibited a significantly large bifurcation below the transition temperature, which was traceable even at 50 kOe of applied magnetic field. The bifurcation temperature was found to be magnetic field dependent for the lower range of magnetic fields, which can be represented by a polynomial of magnetic field. The observed magnetic transition temperature of this compound was in good agreement with the earlier reported results. The…

Synthesis, X-ray crystal structure and magnetic study of a novel μ2-1,1-azido bridged dimeric copper(II) complex

Abstract A new azido derivative of tridentate Schiff base copper(II) complex has been synthesized and characterized. X-ray single crystal structure analysis reveals that the complex [Cu2L2(N3)2(NO3)2] (1), containing 1-(N-pyridylimino)-3-aminopropane (L) as co-ligand, is a dimer in which copper(II) ions are bridged by two azido groups in end-on fashion. The coordination environment around copper(II) is distorted octahedral which is rarely observed among these types of azido bridged copper(II) dimers. Three among the four coordination sites of the basal plane of the octahedron are occupied by the nitrogen atoms of the Schiff base and the fourth site is occupied by a nitrogen atom of a μ2-1,1…

X-ray powder diffraction and LIESST-effect of the spin transition material [Fe(bpp)2](NCS)2·2H2O

Abstract We have studied the X-ray powder diffraction of the spin transition material [Fe(bpp)2](NCS)2 · 2H2O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) at room temperature. Two crystallographic phases have been observed depending on the sample history of this material. The results obtained corroborate the earlier observations from magnetic and calorimetric studies. Relatively prolonged exposure of the sample to X-rays caused a structural change. LIESST and Reverse-LIESST effects, characterised by 57Fe Mossbauer spectroscopy, have been observed in this material.

Pressure Effect Studies on the Spin‐Transition Behavior of a Dinuclear Iron(II) Compound

Magnetic studies into the effect of different hydrostatic pressures between ambient and 1.03 GPa on the high-spin (HS) i low-spin (LS) transition behavior of the dinuclear iron(II) compound [Fe II 2(PMAT)2](BF4)4·DMF (1, PMAT = 4-amino3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole, DMF = N,N-dimethylformamide) have been carried out at 2– 300 K. Under ambient pressure, the sample studied exhibits a [HS–HS] to [HS–LS] half spin transition (ST) at T½ = 208 K without any thermal hysteresis. Increasing the pressure above 0.2 GPa causes an increase (initially rapid but above 0.5 GPa more gradual) of T½ as well as a matching reduction in the residual high-spin fraction at room temperatu…

Oxo-Vanadium(IV) Dihydrogen Phosphate: Preparation, Magnetic Study, and Heterogeneous Catalytic Epoxidation

A layered oxo-vanadium(IV) dihydrogen phosphate, {VO(H2PO 4)2} n has been synthesized hydrothermally and characterized by several physicochemical methods. Single-crystal X-ray analysis (crystal system, tetragonal; space group, P4/ ncc; unit cell dimensions, a = b = 8.9632(4), c = 7.9768(32) A) of {VO(H2PO4) 2} n reveals that the compound has an extended two-dimensional structure. The VO2+ moieties are connected through bridging H 2PO4 (-) ions, and this type of connection propagates parallel to the crystallographic ab plane which gives rise to a layered structure. The layers are staked parallel to the crystallographic c axis with a separation between the layers of ca. 4.0 A. Magnetic suscep…

Microstructural and magnetic characterization of dusts from a stone crushing industry in Birbhum, India

Abstract Stone dust sample collected from a stone crushing industry situated at Muhammad Bazar in Birbhum, India, is studied for its physical characterization using various techniques. Morphology and compositional analysis of the stone dust by scanning electron microscopy (SEM) reveal that the dust is an agglomeration of many tiny particles (0.32–2.12 μm), mostly having sharp edges, as well show microstructure heterogeneity. Elements present in the sample are detected by energy dispersive X-ray spectrometry (EDX). The X-ray diffraction (XRD) pattern analysis shows that the sample mainly contains minerals like anorthite, augite, esseneite and albite. An overall antiferromagnetic interaction …

Contradicting Reports on Magnetic Properties of Layered Molecule-Based Material N(n-C3H7)4[FeIIFeIII(C2O4)3]

Uncompensated magnetization in the layered molecular antiferromagnet {N(n-C5H11)4[MnIIFeIII(ox)3]}∞

Abstract Studies on the magnetic properties of the molecular antiferromagnetic material {N( n -C 5 H 11 ) 4 [Mn II Fe III (ox) 3 ]} ∞ , carried out by various physical techniques (AC/DC magnetic susceptibility, magnetization, heat capacity measurements and Mossbauer spectroscopy) at low temperatures, have been presented. Different experimental observations complement each other and provide a clue for the observation of an uncompensated magnetization below the Neel temperature and short-range correlations persisting high above T N . It is understood that the honeycomb layered structure of the compound contains non-equivalent magnetic sub-lattices, (Mn II –ox–Fe III A –...) and (Mn II –ox–Fe …

Rod-like ferrites obtained through thermal degradation of a molecular ferrimagnet

This paper presents the characteristics of iron oxides obtained through thermal degradation of a molecular ferrimagnet, {N(n-C4H9)4[Fe II

Mossbauer spectroscopic study of the thermal spin crossover in [Fe(II)(isoxazole)(6)](ClO(4))(2)

The (57)Fe Mossbauer spectroscopy of mononuclear [Fe(II)(isoxazole)(6)](ClO(4))(2) has been studied to reveal the thermal spin crossover of Fe(II) between low-spin (S = 0) and high-spin (S = 2) states.Temperature-dependent spin transition curves have been constructed with the least-square fitted data obtained from the Mossbauer spectra measured at various temperatures between 84 and 270 K during a cooling and heating cycle. This compound exhibits an unusual temperature-dependent spin transition behaviour with T(C)(down arrow) = 223 and T(C)(up arrow) = 213 K occurring in the reverse order in comparison to those observed in SQUID observation and many other spin transition compounds. The comp…

Microstructural and magnetic characterization of fly ash from Kolaghat Thermal Power Plant in West Bengal, India

Abstract This paper reports on the physical nature of the fly ash sample of the Kolaghat Thermal Power Plant, India with an emphasis on its ultrafine nature. This paper also deals with the measurement of the magnetic properties of the fine particles of the fly ash sample. Particle sizes of this fly ash sample estimated from the SEM images lie within 0.16–5.50 μm, and the EDX spectral analysis indicates the presence of O, Al, Si, C, Fe, Mg, Na, K and Ti in this sample. From the XRD study, it is found that physical nature of conglomeration in the fly ash is crystalline and the major components are mullite (Al 6 Si 2 O 13 ) and quartz (SiO 2 ). Additionally, the presence of hematite, microclin…

Structural and magnetic diversity in metal-dicyanamido polymer moieties: Paramagnetic and antiferromagnetic 1D chain compound and weakly ferromagnetic 2D motif

Abstract The reaction of M(NO 3 ) 2 · x H 2 O (M = Cu, Ni and Co; x  = 3 for Cu and x  = 6 for Co/Ni), imidazole (Im) and sodium dicyanamide (dca) afforded the complexes [M(Im) 2 (dca) 2 ] (where M = Cu for 1 , M = Ni for 2 , and M = Co for 3 ). All of them have been characterized structurally by single crystal X-ray diffraction measurements. X-ray analysis reveals that the dicyanamido ligand features the μ 1,3 bridging mode that led to the formation of two-dimensional structure of complex 1 while complexes 2 and 3 attribute an infinite one-dimensional chain like structure to generate the fascinating molecular assemblies. The {N(CN) 2 } − ligands present in the complexes 2 and 3 are coordin…

Maghemite polymer nanocomposites with modulated magnetic properties

A method is presented for the production of maghemite polymer nanocomposites with modulated magnetic properties. Magnetic nanocomposites prepared using this method show regular variation in the magnetic blocking temperature from 2 K to 300 K, and variation in the saturation magnetization from 0 to 50 emu g � 1 (Fe2O3). The method is based on the in situ formation of maghemite nanoparticles in nitrogen-base polymer matrixes. The particle size can be varied regularly from 1.5 nm to 16 nm by changing the ratio of iron loading in the polymer and/or the Fe(II)/Fe(III) ratios. The particles are isolated and uniformly distributed within the matrix. The mate

Spin Crossover Phenomenon in Nanocrystals and Nanoparticles of [Fe(3-Fpy)2M(CN)4] (MII = Ni, Pd, Pt) Two-Dimensional Coordination Polymers

The two-dimensional spin crossover (SCO) polymers [Fe(3-Fpy)2M(CN)4] (MII = Ni(1), Pd(2), Pt(3)) were nanostructured in the form of nanocrystals and nanoparticles, and their chemical, structural, and physical characterization was carried out using different experimental methods (powder X-ray diffraction, magnetic susceptibility measurements, Mossbauer and infrared spectroscopy, transmission and scanning electronic microscopy, etc.). Surfactant-free nanocrystals of average dimensions 400 × 400 × 30 nm (1a, 1a*, 2a, 3a) were synthesized from water in oil microemulsions (w/o) while nanoparticles of average size 200 × 100, 100 × 60, and 70 × 30 nm were obtained in poly(vinylpyrrolidone) (PVP) c…

Anomalous Spin Transition Observed in Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate Dihydrate

Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) thiocyanate dihydrate undergoes a two-step singlet (1A1) ⇄ quintet (5T2) transition in which both steps are associated with thermal hysteresis. Thermal cycling of the sample results in its conversion to a second phase which displays a single-step transition with a very narrow hysteresis loop. This second phase slowly reverts to the initial phase on standing at 300 K. The interconversions are completely reversible. The spin state changes have been monitored by measurement of magnetism and Mossbauer spectra and by differential scanning calorimetry (DSC) studies.

Metal-to-metal electron transfer and magnetic interactions in a mixed-valence Prussian Blue analogue

Abstract In search of a new Prussian Blue analogue exhibiting fascinating magnetic properties, potassium manganese hexacyanoferrate, K 0.2 Mn 0 . 66 II Mn 1.44 III [ Fe 0.2 II Fe 0.8 III ( CN ) 6 ] O 0.66 ( CH 3 COO ) 1.32 ] , 7.6H2O, has been synthesized. This compound undergoes a paramagnetic to ferrimagnetic transition at 10 K. Temperature and magnetic field-dependent magnetization studies of this compound have revealed different spin alignments below and above 3 K. The nature of possible magnetic interactions between the nearest neighbor magnetic centers has been discussed in order to explore the origin of the observed magnetic interactions. Mossbauer spectroscopic study at different te…

Synchrotron powder-diffraction study of the spin transition compound [Fe(bpp)2](NCS)2·2H2O and soft X-ray-induced structural phase conversion

Abstract We have studied the high spin and low spin structural phases of the two-step spin transition compound [Fe(bpp) 2 ](NCS) 2 ·2H 2 O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) of different sample history with X-ray synchrotron ( λ  ∼ 0.32 A) powder diffraction at different temperatures as well as with usual X-ray ( λ  ∼ 1.54 A) powder diffraction at room temperature by performing rapid repeated scans at regular intervals of time. A structural phase transition occurs only during the first step of the spin transition. Time dependent interconversions of the two crystallographic phases have been observed at room temperature for this material. The results indicate that a soft X-ray (Cu-K α )-ind…

γ-Fe2O3 nanoparticle in NaY-zeolite matrix: Preparation, characterization, and heterogeneous catalytic epoxidation of olefins

Abstract Nano-sized crystals of maghemite iron oxide (γ-Fe 2 O 3 ) were synthesized onto the surface of NaY-zeolite crystals by immobilizing a polynuclear iron complex [Fe 4 O 2 (O 2 CCH 3 ) 7 (bpy) 2 ](ClO 4 ) (bpy = 2,2′-bipyridine) and subsequent calcination of the material in oxygen. Superparamagnetic γ-Fe 2 O 3 particles with sizes ∼5 nm were formed on the surface of the zeolite matrix. The nano-composite, γ-Fe 2 O 3 @NaY has been subsequently subjected for thorough characterization with several spectroscopic techniques as well as magnetic and transmission electron microscopic measurements. This confirms the formation of maghemite nanoparticles on a NaY-zeolite surface. γ-Fe 2 O 3 @NaY…

Study of thermal spin crossover in [Fe(II)(isoxazole)(6)](BF4)(2) with Mossbauer spectroscopy

Fe-57 Mossbauer spectroscopy of the mononuclear [Fe( II)( isoxazole)(6)]( BF4)(2) compound has been studied to reveal the thermal spin crossover of Fe( II) between low- spin ( S = 0) and high- spin ( S = 2) states. A temperature-dependent spin transition curve has been constructed with the least- square fitted data obtained from the Mossbauer spectra measured at various temperatures in the 240 - 60 K range during the cooling and heating cycle. The compound exhibits a temperature- dependent two- step spin transition phenomenon with T-SCO ( step 1) = 92 and TSCO ( step 2) = 191 K. The compound has three highspin Fe( II) sites at the highest temperature of study; among them, two have slightly …

Synthesis, X-ray crystal structure and magnetic study of a μ 1,5-dca bridged ferromagnetic dimeric copper(II) complex

Reaction of Cu(NO3)2 · 3H2O, 1-(N-salicyalideneimine)-2-(N,N-dimethyl)-aminoethane (HL1), LiClO4, and sodium dicyanamide (Nadca) in aqueous medium affords a dimeric complex [Cu2(L1)2 (μ1, 5-dca)](ClO4) (1). Single crystal X-ray analysis reveals that 1 is dinuclear with copper(II) ions bridged by a single dicyanamide group in end-to-end fashion. The coordination environment around copper(II) is square planar. Two nitrogens and oxygen of the tridentate Schiff-base ligand (HL1) occupy three coordination sites of the square plane while the remaining site is occupied by the nitrogen of a terminal nitrile of the bridging dca. The nitrogen of the other terminal nitrile group of the μ1,5-dca ligand…

Synthesis, X-ray crystal structure and magnetic study of a dicyanamido bridged 1D chain nickel(II) complex

Abstract Reaction of Ni(NO3)2 · 6H2O and sodium dicyanamide (Nadca) yields a 1D infinite chain complex {[Ni(dien)(μ1,5-dca)(H2O)](NO3)}n (1) (where dien = diethylenetriamine). The coordination environment in complex 1 around the nickel(II) ions is distorted octahedron. Three nitrogen atoms of the ligand diethylenetriamine and an oxygen atom of H2O molecule constitute the four coordination sites of the basal plane of the octahedron. Of two axial positions of the octahedron, one position is occupied by the nitrogen atom of a μ1,5-dca anion the remaining coordination site is occupied by a nitrogen atom of another end-to-end bridging dca from an adjacent [Ni(dien)(μ1,5-dca)(H2O)] moiety, yieldi…