Ananta Kumar Ghosh

Structural diversity in manganese squarate frameworks using N,N-donor chelating/bridging ligands: syntheses, crystal structures and magnetic properties

Three new polymeric squarato-bridged manganese complexes {[Mn(H(2)O)(2)(bpe)(sq)].bpe.H(2)O}(n) (1), [Mn(2)(H(2)O)(4)(phen)(2)(sq)(2)](n) (2) and [Mn(2)(H(2)O)(2)(phen)(4)(sq)].(sq).8(H(2)O) (3) [bpe, 1,2-bis(4-pyridyl)ethane; phen, 1,10-phenanthroline; sq, squarate dianion] have been synthesized and characterized by single crystal X-ray diffraction analysis and variable temperature magnetic studies. Complex 1 is a 2D rectangular grid-like structure, achieved through flexible bpe bridging ligands and squarate dianions. On the other hand the use of chelating phen instead of bpe gives rise to a 1D polymeric chain in complex 2 and to a dinuclear entity in 3. In all the three complexes weak interactions play a vital role in stabilizing the solid-state structure. Variable temperature (2-300 K) magnetic studies indicate weak antiferromagnetic coupling between the metal centres in all the complexes.

Towards rational design of supramolecular helices using linear pseudohalides in Cd(II) - 2,2′-biimidazole system

Three cadmium complexes, [Cd(H2biim)2(SCN)2] (1), [Cd(H2biim)2(SeCN)2] (2) and [Cd(H2biim)2(dca)2] (3) [H2biim = 2,2′-biimidazole; dca = dicyanamide] have been synthesized and characterized by X-ray single crystal structure analysis. In complexes 1 and 2 monomeric units assemble into supramolecular helix whereas in 3 monomeric units assemble into supramolecular 2-D grid with (4,4) net topology. The appearance of helical topology in complexes 1 and 2 is due to the linear nature of SCN−/SeCN− whereas (4,4) net topology in complex 3 is due to the bent nature of dca−. In each case R12(7) hydrogen bonding synthon is attained facilitating the helical and (4,4) net topology.

Synthesis, crystal structure and magnetic behavior of a croconato bridged Cu(II) complex: effect of C–H⋯O interaction in controlling the coordination bond formation in organic–inorganic hybrid

A 2-D croconato bridged complex of Cu(II), [{Cu(C5O5)(bpee)}·0.5H2O]n (1) [bpee, trans-1,2-bis(4-pyridyl)ethylene] has been synthesized by in situ hydrothermal reaction and characterized by X-ray diffraction analysis, variable temperature magnetic susceptibility measurement and EPR study. The structure determination reveals that the adjacent 2-D sheets are extended to 3-D supramolecular architecture through π–π and trifurcated C–H⋯O interactions, which inhibit the oxygen atom of croconate from forming the usual bridging mode.

Thermal Investigation of 1,2-propanediamine complexes of nickel(II) in the solid phase

Thermal studies have been carried out on [NiL3]X2·n H2O, whereL=1,2-propanediamine;X=Cl−, Br−, SCN−, 1/2SO42− and 1/2 SeO42−; andn= 2, 1.5 and 0. [Ni2L5(NCS)2](SCN)2 and [NiL2SO4] have been synthesized pyrolytically in the solid-state from their mother diamine complexes. The deaquation behaviour of [NiL3]SO4·2 H2O appears interesting, and its monohydrate undergoes a solid-state reaction (88–102°) without mass loss, showing an exothermic peak at 95 °C (ΔH=− 5.1 kJ mole−1).ZusammenfassungThermische Untersuchungen wurden an [NiL3]X2,n H2O ausgeführt, wobeiL-1,2-Propandiamin;X=Cl−, Br−, SCN−, 1/2 SO42− und 1/2 SeO42−;n=2, 1.5 und 0. [Ni2Ls(NCS)2](SCN)2 und [NiL2SO4] wurden ausgehend von den entsprechenden Diaminkomplexen pyrolytisch im festen Zustand synthetisiert. Das Dehydratisierungsverhalten von [NiL3]SO4·2 H2O scheint interessant zu sein, und beim entsprechenden Monohydrat wird eine ohne Massenverlust verlaufende Festkörperreaktion (88–102°) beobachtet, die sich durch einen exothermen Peak bei 95 °C (ΔH=− 5.1 kJ mol−1) zu erkennen gibt.РезюмеПроведено термическ ое исследование комплексов типа [N3L3]Х2· nН2O, где L=1,2-пропандиамин,Х=Сl−, Br−, SCN−, 1/2 SO42-, 1/2SeO42-, an=2, 1.5 и 0. Комплексы типа [Ni2L5(NCS)2](SCN)2 и [NiL2SO4] были получены в твердом состоянии путем пиролиза соотв етствующих диаминов ых комплексов. Дегидрат ация комплекса [N3L3]SО4·2 Н2О протекает с п отерей одной молекул ы воды, а образующийся моног идрат затем в области темпе ратур 88–102° подвергает ся твердотельной реакц ии без потери веса, показывая при эт ом экзотермический п ик при 95 °С ΔН=− 5.1 кдж·моль−1.

Phase transition and decomposition of tetraethylammonium tetrahalomanganate in the solid state

Abstract The synthesis, magnetic and electronic spectral studies of tetrahedral tetrahalometallates have drawn much attention since 1958 [1]. A lot of studies have been made with tetraalkyltetrahalometallates due to their temperature-dependent spectral, magnetic, thermal, etc., properties [2]. Tetramethylammoniumtetrahalometallates undergo high-temperature normal phase transition to the incommensurate phase on cooling. The incommensurate phase undergoes a transition to the commensurate phase on further cooling [2]. Low-temperature phase transitions of tetraethylammoniumtetrachlorometallates of first-row transition metals are known [3], but the phase transitions of the corresponding tetrabromo compounds and aboveambient temperature phase transitions of [NEt 4 ] 2 MX 4 are not yet reported. The present paper reports the phase transitions of [NEt 4 ] 2 MnX 4 (X = Cl or Br) starting from 233 K to their corresponding decomposition temperatures. It also includes their thermal decompositions.