Preparation, characterisation and thermal behaviour of N-(3-aminopropyl)-1,3-propanediamine complexes of nickel (II) in the solid state

The complexes [Ni(dpt)2]X2 • nH2O (where dpt is N-(3-aminopropyl)-1,3-propanediamine; n = 0 when X is I, NCS or ClO4; n = 1 when X is Cl, Br or NO3; n ≫ 1 when X is 0.5SO4 and 0.5SeO4), Ni(dpt)X2 • nH2O (n = 0 when X is Cl or NO3; n = 1 when X is Br or I; n = 2 when X is NO3; n = 3 when X is 0.5SO4 or 0.5SeO4), [Ni(aepn) 2)]I2, Ni(aepn)I2 (where aepn is N-(2-aminoethyl)-1,3-propanediamine, [Ni(dien) 2]I2 and Ni(-dien)I2 (where dien is diethylenetriamine) have been synthesised from the solution and thermal investigations upon them have been carried out in the solid state. [Ni(dpt) 2]X2 (X is Br or NO3) undergoes endothermic reversible phase transitions upon heating (198–212°C, ΔH = 3.5 kJ mol−1 and 205–222°C for [Ni(dpt) 2]Br2 and [Ni(dpt) 2](NO3)2 respectively). Ni(dpt)I2 shows exothermic irreversible phase transition during heating (193–220°C; ΔH = 4.1 kJ mol−1). The thermal stabilities of dpt complexes are compared with those of the corresponding aepn and dien complexes

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

[Cd(aepn)₂]X₂•nH₂O (where aepn is N-(2-aminoethyl)-1,3-propanediamine, and n = 1 when X is Cl⁻ and Br⁻, n = 0 when X is 0.5SO²⁻₄, 0.5SeO²⁻₄, NO⁻₃ and I⁻), Cd(aepn)X₂ (where X is Cl⁻, Br⁻, I⁻, 0.5SeO²⁻₄, 0.5SO²⁻₄ and SCN⁻) and Cd(dpt)X₂•nH₂O (where dpt is N-(3-aminopropyl)-1,3-propanediamine, and n = 1 when X is 0.5SO²⁻₄ and 0.5SeO²⁻₄, n = 0 when X is Cl⁻, Br⁻, I⁻ and SCN⁻) have been synthesised and investigated thermally in the solid state. The species Cd(aepn)Cl₂, Cd(aepn)SO₄ and Cd(aepn)SeO₄ 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)SO₂•H₂O 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] (NO₃)₂ and Cd(aepn)I₂ 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

Syntheses and crystal structures of two isomers of CuL²(NO³)²• 2H²O (L = N¹-isopropyl-2-methyl-1,2-propanediamine) and their thermochromism in the solid state

Two isomeric complexes, [CuL₂](NO₃)₂ • 2H₂O, (1, red) and [CuL₂](H₂O)](NO₃)₂ • H₂O, (2, blue) (L=N¹-isopropyl-2-methyl-1,2-propanediamine) have been synthesised and their X-ray crystal structures have been determined. Both the isomers possess the same space group, P2₁\n. However, 1 is square planar and 2 is square pyramid having N₄ and N₄O chromophore, respectively around copper (II). The red isomer (1) upon heating loses water molecules yielding a violet dehydrated species, 1a which on further heating undergoes an exothermic phase transition accompanied by thermochromism, violet (1a) to blue-violet (1b) in the solid state. (1a) and (1b) are probably conformational isomers and they revert to 1 in humid atmosphere. The blue isomer (2) upon heating transforms to blue-violet species on dehydration, which reverts immediately after cooling in open atmosphere

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 NiL2Cl2 1 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

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

[NiL₂(NCS) ₂]•H₂O (1) and [NiL₂(NCS) ₂] (2) (L = N, N′-diethyl-1, 2-ethanediamine) have been synthesized from solution. The species 1 on deaquation transforms to [NiL₂(NCS) ₂] (1a) which subsequently undergoes an irreversible exothermic phase transition (118–142°C; ΔH = −3.8kJ mol⁻¹) accompanied by a pinkish-blue to blue thermochromism producing an isomer [NiL₂(NCS) ₂] (1b). The pinkish-blue species 2 on heating shows an endotherm (82–120°C; ΔH = 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) ₂(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

[Ni₂(dien) ₂(NCS) ₄(H₂O)] (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 [Ni₂(dien) ₂(NCS) ₄(H₂O)] 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