Ashutosh Ghosh

Synthesis, chemical characterization, structural data and solid state behaviour of N, N′-diethyl-1, 2-ethanediamine complexes of nickel(II) thiocyanate

Abstract [NiL 2 (NCS) 2 ]·H 2 O ( 1 ) and [NiL 2 (NCS) 2 ] ( 2 ) (L = N, N′-diethyl-1, 2-ethanediamine) have been synthesized from solution. The species 1 on deaquation transforms to [NiL 2 (NCS) 2 ] ( 1a ) which subsequently undergoes an irreversible exothermic phase transition (118–142°C; Δ H = −3.8kJ mol −1 ) accompanied by a pinkish-blue to blue thermochromism producing an isomer [NiL 2 (NCS) 2 ] ( 1b ). The pinkish-blue species 2 on heating shows an endotherm (82–120°C; Δ H =kJ mol −1 ) yielding the species 1b . Single crystal X-ray structure analyses of 1 and 2 have been carried out. The metal atoms in both the complexes, lying at crystallographic inversion centres, display distored octahedral geometries with four amine nitrogen atoms defining the equatorial plane and two isothiocyanato groups in trans axial positions.

Thermochromism in copper(II) complexes: thermal, spectroscopic, solid-state broadline 1H NMR and room-temperature single-crystal x-ray analysis of bis(N,N′-dimethyl-1,2-ethanediamine)copper(II) dinitrate

Abstract The complex bis(N,N′-dimethyl-1,2-ethanediamine)copper(II) dinitrate, Cu (NN′-dmen)2(NO3)2, undergoes a first-order thermochromic phase transition at ca 148°C, changing from blue-violet to blue. The low-temperature phase has been characterized by X-ray crystallography. The copper ion possesses distorted (4+2) octahedral geometry with two five-membered chelate rings, in the δλ conformation, forming the CuN4 plane [CuN = 2.000(6) and 2.033(7) A] and oxygens from the two nitrate groups weakly coordinated in the two axial coordination sites [CuO = 2.506(8) A]. The broad-line 1H NMR indicates the onset of a dynamic disorder of diamine chelate rings at the phase transition temperature region. The electronic spectrum broadens on phase transition.

Synthesis, characterisation and solid state thermal behaviour of nickel(II) diamine complexes

Summary[NiL2X2] (L =N,N′-dimethyl-1,2-ethanediamine; X = Cl−, CF3CO2−, CC13CO2− and CBr3CO2−), [NiL2C2O4] · H2O and [NiL2X2] · 2 H2O (X = Br−, 0.5 SO42− and 0.5 SeO4−) have been synthesised and their thermal studies carried out. Thermally induced phase transition phenomena are noticed in [NiL2X2] (X = CF3CO2− and CCl3CO2−) and their probable mechanisms are described. [NiL2X2] (X = Br−, 0.5 SO42− and 0.5 SeO42−) and [NiLX2] (X = Cl−, 0.5 C2O42− and 0.5 SO42−) have been prepared by solid state pyrolysis from the respective parent diamine complexes. [NiL2X2] have been made in solid state by temperature arrest technique from [NiL2(CX3CO2)2] (X = Cl− and Br−).

Phase transition and decomposition of A2MX4 [A = (C2H5)4N; M = Co(II), Ni(II) AND Cu(II); X = Cl and Br] in the solid state

Abstract A 2 MBr 4 undergoes endothermic reversible phase transitions at subambient and above ambient temperatures. The cooling curve of A 2 MBr 4 (M = Cu and Ni) above 400 K is split compared to the corresponding heating curve and the nature of splitting appears to be dependent on time. The low temperature phase transitions are due to orientation of both t d cations and anions and the high temperature phases are probably followed by the formation of several intermediate structures.

Thermally induced isomerization and decomposition of N-methyl-1,3-propanediamine complexes of nickel(II) in the solid state

Abstract [NiL 2 (H 2 O)Cl]Cl· n H 2 O (L= N -methyl-1,3-propanediamine: n =0 and 1). [NiL 2 X 2 ] [X = Br, CF 3 CO 2 and CCl 3 CO 2 ], and [NiL 2 ,(H 2 O)Y]·H 2 O (Y = SO 4 and SeO 4 ) have been synthesized and their thermal investigations have been carried out in the solid state. [NiL 2 (H 2 O)Cl]Cl· n H 2 O and [NiL 2 (H 2 O)Y]·H 2 O exist in the trans form. On deaquation they transform to cis -[NiL 2 Cl 2 ] and cis -[NiL 2 Y]. [NiL 2 (SO 4 )] undergoes a reversible endothermic phase transition (117–169 °C Δ H = 6.5 kJ mol −1 ). The complex trans -[NiL 2 (CF 3 CO 2 ) 2 ] has been found to transform into its isomer upon heating, showing an endotherm (135–150 °C, Δ H = 18.9 kJ mol −1 ); on keeping the product in a humid atmosphere (relative humidity 60–70%), it reverts to its original form. [NiL 2 Cl 2 ], [NiLCl 2 ] and [NiL(SO 4 )] have been synthesized pyrolytically in the solid state from their parent diamine complexes. All the complexes possess octahedral geometry and diamine is chelated in all of them except in [NiL(SO 4 )] where it is bridged. The occurrence of phase transition phenomena is supposed to be due to conformational changes in the six-membered chelate rings.

Thermally induced isomerisation and decomposition of diethylenetriamine complexes of nickel(II) in the solid state

SummaryComplexes [NiL2]X2·nH2O (L=diethylenetriamine; n=O when X=CF3CO2 or CCl3CO2; n=1 when X=Cl or Br, and n=3 when X=0.5SO4 or 0.5SeO4) and NiLX2·nH2O (n=1 when X=Cl or Br; n=3 when X=0.5SO4 or 0.5SeO4) have been synthesised and investigated thermally in the solid state. NiLSO4 was synthesised pyrolytically in the solid state from [NiL2]SO4·[NiL2]X2 (X=Cl or Br) undergo exothermic irreversible phase transitions (242–282° C and 207–228° C; ΔH=−11.3 kJ mol−1 and −1.9 kJ mol−1 for [NiL2]Cl2 and [NiL2]Br2, respectively). [NiL2]-phenomenon (158–185° C; ΔH=2.0 kJ mol−1). NiLX2· nH2O (n=1 or 3) undergo simultaneous deaquation-isomerisation upon heating. All the complexes possess octahedral geometry.

Thermal phase transition and decomposition of N-methyl-1,2-ethanediamine complexes of nickel(II) in the solid state

Abstract [NiL3]X2H2O(L=Nmethyl-1,2-ethanediamine; X− = Cl− and Br−), [NiL3]X2 (X− = NO3− and BF4−) and [NiL2X2] (X− = Cl−, Br−, NCS−, CF3CO−2 and CCl3CO−2) have been synthesized and their thermal studies have been investigated in the solid state. [NiL3]Br2, [NiL2Br2] (X− = Cl− and Br− ), [NiLCl2] and NiL0.5Cl2 have been synthesized pyrolytically in the solid state from their corresponding parent diamine complexes. [NiL2X2] (X− = Cl− and Br−) undergo endothermic reversible phase transition whereas [NiL3]X2 (X− = N0−3 and BF−4 ) and [NiL2(CF3CO2)2] show endothermic time dependent reversible phase transition. All the complexes except NiL0.5Cl2 possess octahedral geometry. NiL0.5Cl2 possesses an unusually high magnetic moment (5.8 B.M. at 28 °C).

Thermal studies of N1-isopropyl-2-methyl-1,2-propanediamine complexes of zinc(II) and cadmium(II) in the solid phase

Abstract CdL3(ClO4)2, ZnL2X2, CdL2X′2 · nH2O (where L is N1-isopropyl-2-methyl-l,2-propane-diamine, X is Cl, Br, I, ClO4, SCN, 0.5SO4 and 0.5SeO4; n = 0 when X′ is Cl, Br, I, SCN and 0.5SO4; n = 3 when X′ is ClO4; n = 4 when X′ is 0.5SeO4) and MLX2 (M is Zn(II) or Cd(II) and X is Cl, Br and I) were synthesized from solution. The species CdL2(ClO4)2 and MLX2 (M is Zn(II) or Cd(II) and X is Cl, Br and I) were synthesized from the corresponding parent complexes by the temperature-arrest technique. CdL2(SCN)2 exists in two isomeric forms and both have been synthesized. One of the isomers undergoes an irreversible phase transition (102–120°C, ΔH = 12.8 kJ mol−1) and transforms to the other form in the solid phase. ZnL2(ClO4)2 shows a reversible phase transition (178–208°C, ΔH = 9.2 kJ mol−1) upon heating in the solid phase. CdL2(ClO4)2 undergoes a reversible phase transition (73–98°C, ΔH = 4.4 kJ mol−1) and then on further heating shows time-dependent reversible phase transitions (136–190°C, ΔH = 15.3 kJ mol−1) in the solid phase. The phase transition in CdL2(SCN)2 is due to the change in coordination mode of the thiocyanate ion, whereas in CdL2(ClO4)2, the time-dependent reversible phase transition is due to conformational changes in the diamine chelate rings.

Solid state thermal isomerisation of diethylenetriamine complexes of NiX2 (X=NO3, ClO4, BF4 and CF3SO3)

Summary[Ni(dien)2]X2·nH2O (dien=diethylenetriamine; n=0, X=NO3 or CF3SO3; n=0.5, X=ClO4 or BF4 and n=2, X=CF3SO3) complexes have been prepared and investigated thermally in the solid state. [Ni(dien)2](NO3)2 (1) and [Ni(dien)2](CF3SO3)2 (2) undergo endothermic irreversible phase transitions (209–247°C and 184–205°C; ΔH=5.6 kJ mol−1 and 7.7 kJ mol−1 for (1) and (2), respectively). [Ni(dien)2](ClO4)2·0.5H2O (3) shows an endothermic irreversible phase transition after deaquation (201–216°C; ΔH=7.7 kJ mol−1). [Ni(dien)2](BF4)2·0.5H2O also shows an endothermic irreversible phase transition after deaquation, accompanied by partial decomposition. All the complexes possess octahedral geometry with the ligands arranged meridionally. The phase transitions are explained in terms of conformational changes of the triamine chelate rings.

Thermally induced solid-state isomerisation and decomposition of 2,2-dimethyl-1,3-propanediamine nikel(II) complexes

SummaryComplexes [NiL3]Br2·H2O (L=2,2-dimethyl-1,3-propanediamine), [NiL2X2] (X=Cl, Br, NCS, CF3CO2, HCCl2CO2 or CCl3CO2 and X2=SO4 or SeO4) and [NiL(HCCl2CO2)2]·H2O have been synthesised and their thermal studies have been investigated in the solid state. The complexes, [NiL2X2] (X=Cl or Br) and NiLX2 (X=Cl or HCCl2CO2) have been isolated thermally in the solid state. All the complexes possess octahedral geometry. [NiL2Br2] and [NiL2(CF3CO2)2] exist in two interconvertible isomeric forms. ΔH for the conversions were determined. [NiL2(HCCl2CO2)2] (5) undergoes an irreversible phase transition (178–188°C; ΔH=4.4kJ mol−1]. NiL(HCCl2CO2)2·H2O shows an exothermic irreversible phase transition (104–128°C; ΔH=−5.8 kJ mol−1) after losing water. The phase transitions are assumed to be due to the conformational changes in the chelate ring of diamine.