Chandi Pariya

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.

Syntheses of [Ni2(dien)2(NCS)4(H2O)] and [Ni(aepn)(NCS)2]n ((dien = bis(2-aminoethyl)amine and aepn = N-(2-aminoethyl)-1,3-propanediamine): single crystal structure analysis and thermal behaviour in the solid state

Abstract [Ni 2 (dien) 2 (NCS) 4 (H 2 O)] ( 1 ) and [Ni(aepn)(NCS) 2 ] n ( 2 ) (where dien = bis(2-aminoethyl)amine and aepn = N -(2-aminoethyl)-1,3-propanediamine) have been synthesised from solution. Single crystal X-ray structure analyses of 1 and 2 reveal that the metal atoms in both the complexes display distorted octahedral geometry with the triamine coordinating facially in 1 and meridionally in 2 . The dinuclear [Ni 2 (dien) 2 (NCS) 4 (H 2 O)] unit in 1 is bridged via a thiocyanate moiety while in 2 the nickel(II) octahedra form a polymeric chain. The species 1 on deaquation at ∼ 165°C followed by cooling yields a conglomerated mass ( 1a ). The species 2 melts at ∼ 230°C which on cooling yields conglomerated mass ( 2a ). Both 1a and 2a are amorphous; the former reverts to 1 in a humid atmosphere.

Thermochromism in nickel(II) complexes: thermal, IR spectroscopic, solid-state 1H NMR and single crystal X-ray analysis of diaqua-bis(2,2-dimethyl-1,3-propanediamine) nickel(II) nitrate☆

Abstract The newly synthesized complex [Ni(dmtn) 2 (H 2 O) 2 ](NO 3 ) 2 (dmtn = 2,2-dimethyl-1,3-propanediamine) undergoes a reversible thermochromic phase transition in the range of 180–202°C ( ΔH = 10.4kJ mol −1 ) on heating after dehydration (dehydration temperature range 43–102°C). The complex has been characterized by X-ray crystallography at room temperature. The crystals are monoclinic, space group C2 m , a = 20.385(2), b = 6.9004(4), c = 6.9552(3) A , β = 102.60(5)°, V = 954.8(1) A 3 , Z = 2 and R = 0.046. The geometry of the nickel atom in the complex is tetragonally distorted octahedral with two H 2 O molecules coordinated at the trans position. The diamine chelate rings are in the trans chair-chair conformations. The broad-line 1 H NMR of partially deuterated [Ni(dmtn- d 4 ) 2 (NO 3 ) 2 ] (deuterated amine protons) indicates the onset of dynamic disorder of the diamine chelate rings at the phase transition temperature. The high temperature IR spectral measurement shows the complex retains its trans configuration after dehydration and phase transition with NO − 3 ions coordinated as a monodentate ligand.

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.

Variable geometry of nickel(II) complexes with N1-isopropyl-2-methyl-1,2-propanediamine(L). Crystal structures of [NiL2]Br2·3H2O, [NiL2Br]Br and [NiL2(NCS)2] and solid-state thermochromism in [NiL2]Br2·3H2O

The complexes NiL2X2·nH2O (L =N1-isopropyl-2-methylpropane-1,2-diamine; n= O, X = Cl, NCS or Br; n= 3, X = Br) have been prepared and the crystal structures of [NiL2]Br2·3H2O 2, [NiL2Br]Br 3 and [NiL2(NCS)2]4 determined. The metal co-ordination in complex 2 is square planar (N4 chromophore), whereas in 3 it is a distorted trigonal bipyramid with one of the bromine atoms and the two primary nitrogen atoms defining the basal plane, the secondary nitrogen atoms being in axial positions. Complex 4 is trans octahedral with a N6 chromophore. The geometry of NiL2Cl21 is proposed to be five-co-ordinate as in 3. Complex 2 on heating, undergoes an irreversible exothermic isomerisation after dehydration transforming into 3, a unique example of a change from square-planar to trigonal-bipyramidal nickel(II), accompanied by a yellow to green thermochromism in the solid state.

Thermal studies of N,N′-diethylethane-1,2-diamine complexes of nickel(II) in the solid state

[NiL3]X2 (where L=N-phenylethane-1,2-diamine and X=I− and ClO4−), [NiL2X2] (X is Cl−, Br−, NCS−, 0.5SO42− or 0.5SeO42−) and [NiL2(H2O)2](NO3)2 have been synthesized from solution and their thermal study has been carried out in the solid phase. [NiL2Cl2] upon heating undergoes irreversible endothermic phase transition (142–152°C, ΔH=0.35 kJ mol−1) without showing any visual colour change. This phase transition is assumed to be due to conformation changes of the diamine chelate rings. NiLCl2 and NiL2.5I2 have been prepared pyrolytically from [NiL2Cl2] and [NiL3]I2 respectively in the solid state. [NiL2(H2O)2](NO3)2 upon heating undergoes deaquation-anation reaction without showing any visual colour change. [NiL2X2] (X is Cl−, Br−, NCS−), [NiL2(H2O)2](NO3)2 and [NiL2(NO3)2] possess trans-octahedral configuration, whereas, [NiL2X2] (X is 0.5SO42− or 0.5SeO42−) are having cis-octahedral configuration. Amongst the complexes, only NiLCl2 shows unusually high (5.1 BM at 27°C) magnetic susceptibility value.

Carbon dioxide activation: synthesis and characterization of acadmium(ii) dinuclear complex with a novel µ-carbonato bridge

The cadmium(II) complex of N′-isopropyl-2-methylpropane-1,2-diamine (npda), [Cd(npda) 3 ][ClO 4 ] 2 1 in aqueous methanol absorbs CO 2 from air to form a cadmium(II) dinuclear complex, [Cd(npda) 4 (CO 3 )(H 2 O)][ClO 4 ] 2 ·H 2 O 2, the first ever example of a µ-carbonato cadmium(II) diamine complex which is characterized by elemental analysis, IR and crystal structure determination.

Thermal studies N-(2-aminoethyl)-1,3-propanediamine and N-(3-aminopropyl)-1,3-propanediamine complexes of cadmium(II)

Abstract [Cd(aepn) 2 ]X 2 · n H 2 O (where aepn is N -(2-aminoethyl)-1,3-propanediamine, and n = 1 when X is Cl − and Br − , n = 0 when X is 0.5SO 2− 4 , 0.5SeO 2− 4 , NO − 3 and I − ), Cd(aepn)X 2 (where X is Cl − , Br − , I − , 0.5SeO 2− 4 , 0.5SO 2− 4 and SCN − ), and Cd(dpt)X 2 · n H 2 O (where dpt is N -(3-aminopropyl)-1,3-propanediamine, and n = 1 when X is 0.5SO 2− 4 and 0.5SeO 2− 4 , n = 0 when X is Cl − , Br − , I − and SCN − ) have been synthesised and investigated thermally in the solid state. The species Cd(aepn)Cl 2 , Cd(aepn)SO 4 and Cd(aepn)SeO 4 have also been synthesised pyrolytically in the solid state from the corresponding parent bis-complexes. Cd(aepn) (SCN) 2 and Cd(dpt) (SCN) 2 melt on heating and exist as supercooled liquids at ambient temperature. On heating and after deaquation, Cd(dpt)SO 4 ·H 2 O shows two endothermic phase transitions (172–190°C, ΔH = 8.0 kJ mol −1 and 210–245°C, ΔH = 3.5 kJ mol −1 and the low-temperature transition is reversible (182–165°C, ΔH = −7.8 kJ mol −1 ). Conversely, the selenate analogue undergoes an irreversible endothermic phase transition (240–257°C, ΔH = 13.2 kJ mol −1 ). [Cd(aepn) 2 ] (NO 3 ) 2 and Cd(aepn)I 2 show irreversible endothermic phase transitions (198–218°C, ΔH = 5.9 kJ mol −1 for nitrate, and 195–202°C, ΔH = 8.3 kJ mol −1 for iodide). The transitions are assumed to be due to the conformational changes in the triamine chelate rings. The thermal stabilities are rationalized with respect to the carbon chain lengths of the triamine ligands.

Thermal studies of N1-isopropyl-2-methyl-1,2-propanediamine complexes of nickel(II)X2 [X = I−, CF3CO−2, 0.5SO2−4 and 0.5SeO2−4] in the solid state

Abstract The complexes NiL2X2·nH2O (L = N1-isopropyl-2-methyl-1,2-propanediamine; X = 0.5SO2−4 when n = 0; X = I− when n = 2; X = CF3CO−2 when n = 0 or 2 and X = 0.5SeO2 −4 when n = 0 or 3) have been synthesized and their thermal behaviour has been studied. All the hydrated complexes are yellow in colour and on heating lose water of hydration accompained by a yellow → light blue thermochromic transition, except in the case of the iodide complex, which retains the original yellow colour on dehydration. However, NiL2I2 undergoes an irreversible exothermic phase transition (166–193°C; ΔH = −7.5 kJ mol− 1) with change in colour from yellow to reddish yellow. NiL2(CF3CO2)2 shows a reversible phase transition (heating cycle, 144–170°C; ΔH = 3.1 kJ mol− 1; cooling cycle, 158–135°C; ΔH = − 3.1 kJ mol− 1) with no visual change in colour. All the yellow complexes possess square-planar geometry and the light blue complexes NiL2X2(X = CF3CO−2, 0.5SO2 −4 and 0.5SeO2 −4) are expected to be pentacoordinated. The phase transition occurring in NiL2X2 (X = I− and CF3CO−2) is due to conformational changes of the diamine chelate rings.

Thermally induced isomerization and decomposition of N-(2-aminoethyl)-1,3-propanediamine complexes of nickel(II) in the solid state

Abstract [Ni(aepn) 2 ]X 2 · n H 2 O, Ni(aepn)Y 2 · n H 2 O and [Ni(aepn)Z 2 ] (where aepn is N -(2-aminoethyl)-1,3-propanediamine; n = 0 when X is Cl, Br, NO 3 and ClO 4 ; n = 4 when X or Y is 0.5SO 4 or 0.5SeO 4 and Z is Cl, Br and NO 3 ) have been synthesized and investigated thermally in the solid state. [Ni(aepn) 2 ]X 2 (X is 0.5SO 4 or 0.5SeO 4 ) undergoes exothermic irreversible phase transitions on heating (238–261°C and 220–244°C for [Ni(aepn) 2 ]SO 4 and [Ni(aepn) 2 ]SeO 4 respectively, Δ H = −7.3kJ mol −1 for [Ni(aepn) 2 ]SeO 4 ); and [Ni(aepn) 2 ](ClO 4 ) 2 shows an endothermic irreversible phase transformation on heating (228–240°C, Δ H = 4.2kJ mol −1 ). All the complexes possess octahedral geometry and the latter transformation is explained in terms of conformational changes of the individual chelate ring.