Thermochromism in copper(II) halide salts.  4.  Bis(diethylammonium)tetrachlorocuprate(II), structure of the high-temperature phase and physical characterization of its two phases

Bloomquist, D.R.; Pressprich, M. R.; Willett, Roger D.

doi:10.1021/ja00230a020

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“…Thus, the analysis of the spectra obtained shows that the high-temperature phase of DEACC-I is characterized by a distorted tetrahedral position of the surrounding of the copper ion and the low-temperature one -by the coexistence of the anions of quadratic and tetrahedral forms. These conclusions agree entirely with the results of the x-ray structural analysis and investigations carried out with application of resonance methods [1]. Taking into account the data of [1], we may conclude that redistribution of the hydrogen bonds occurs during phase-transition.…”

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“…These conclusions agree entirely with the results of the x-ray structural analysis and investigations carried out with application of resonance methods [1]. Taking into account the data of [1], we may conclude that redistribution of the hydrogen bonds occurs during phase-transition. The length of these bonds is increased upon attainment of the phase-transition temperature in the regime of heating, as a result of which the hydrogen bonds become weaker.…”

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“…The compounds of the group A 2 MeCl 4 and AMeCl 3 (Me = Cu, Co) [1-5] with an alkylammonium cation, to which the crystals of diethylaminetetrachlorocuprate -[NH 2 (C 2 H 5 ) 2 ] 2 CuCl 4 (DEACC) -are related, constitute a new class of thermochromic materials. According to [1], these crystals at T t = 323 K undergo a thermochromic phase transition of the first kind accompanied by a sharp change in the color of a sample from green to yellow in the regime of heating. The hydrogen bonds that influence the degree of deformation of the metal-haloid polyhedra play an important role in the phenomena of thermochromism, which, in turn, is manifested in the change in the absorption spectra.…”

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“…It corresponds to the thermochromic phase transition, which, unlike the case of DEACC crystals, actually has a continuous character. At the same time, the temperature dependence of the absorption coefficient in the vicinity of T t displays a kind of a global hysteresis in the form of a double loop (the dependence in the regime of heating does not coincide with the dependence in the regime of cooling), which, by analogy with DEACC, can be related to the phenomenon of the coexistence of phases in the vicinity of the presumed phase transition [1,2]. Based on the data obtained, we may draw a conclusion on displacement of the phase-transition temperature T t in comparison with DEACC-II by about 2 K to the side of low temperatures.…”

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Electronic spectra and nature of transitions in [NH2(C2H5)2]2CuxZn1−x Cl4 (x = 0.5, 1) crystals

2004

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The absorption spectra of the [NH 2 (C 2 H 5 ) 2 ] 2 CuCl 4 crystals grown from a solution in ethyl alcohol and also of solid solutions of [NH 2 (C 2 H 5 ) 2 ] 2 Zn 0.5 Cu 0.5 Cl 4 in the visible spectral region have been investigated in the vicinity of thermochromic phase transitions. It is shown that the phenomenon of thermochromism in these crystalline compounds is primarily related to the replacement of the square-planar geometry of the coordination surrounding of the Cu 2+ ion by a tetrahedral one.Introduction. Thermochromic crystals have attracted the attention of researchers in connection with their possible use as sensitive materials of sensor technology and also in recording optical information. The compounds of the group A 2 MeCl 4 and AMeCl 3 (Me = Cu, Co) [1-5] with an alkylammonium cation, to which the crystals of diethylaminetetrachlorocuprate -[NH 2 (C 2 H 5 ) 2 ] 2 CuCl 4 (DEACC) -are related, constitute a new class of thermochromic materials. According to [1], these crystals at T t = 323 K undergo a thermochromic phase transition of the first kind accompanied by a sharp change in the color of a sample from green to yellow in the regime of heating. The hydrogen bonds that influence the degree of deformation of the metal-haloid polyhedra play an important role in the phenomena of thermochromism, which, in turn, is manifested in the change in the absorption spectra.At room temperature, the [NH 2 (C 2 H 5 ) 2 ] 2 CuCl 4 crystals grown from a solution in ethyl alcohol (from now on, DEACC-I) belongs to the space group P2 1 ⁄ n. The parameters of the elementary cell are: a = 7.362 A°, b = 15.025 A°, c = 45.193 A°, β = 89.94 o , and Z = 12. One asymmetric structural group includes three tetrahedrally and nine octahedrally coordinated ions [CuCl 4 ] 2− in an abnormally large cell. All DEA + cations participate in the formation of the two-dimensional network of strong hydrogen bonds N-H⋅⋅⋅Cl parallel to the plane (bc). The high-temperature phase is also monoclinic with the space group P2 1 ⁄ c (a = 25.055 A°, b = 10.531 A°, c = 15.455 A°, β = 100.63 o , and Z = 8) [1].The temperature of the thermochromic phase transition in these crystals is greatly determined by the conditions of their growing. For the crystals grown from an aqueous solution (from now on, DEACC-II) it was equal to T t = 311 K (in the regime of heating) [2,4].In view of the thermochromic character of the indicated phase transition, absorption spectroscopy has turned out to be an effective tool for studying its nature [4]. The studies of DEACC-II crystals have shown that a phase transition is associated with changes in the coordination surrounding of the copper ion. Here, just as in the case of DEACC-I, the high-temperature phase is characterized by a distorted tetrahedral position of the surrounding of the copper ion, whereas the low-temperature one is characterized by the co-existence of the anions of the plane quadratic and tetrahedral forms (each surrounding of the copper ion yields two absorption bands). A sharp change in the config...

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confidence: 88%

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confidence: 88%

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confidence: 99%

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Electronic spectra and nature of transitions in [NH2(C2H5)2]2CuxZn1−x Cl4 (x = 0.5, 1) crystals

2004

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“…For example, X-ray single crystal, IR, NMR, EPR, magnetic susceptibility and calorimetric measurements, etc. in the last few decades [4][5][6][7][8][9]. These complexes showed abrupt color change on heating in the solid state.…”

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Synthesis and Spectrothermal Studies of Thermochromic Diamine Complexes of Cobalt(III), Nickel(II) and Copper(II) Squarate. Crystal Structure of [Co(en)3](sq)1.5 · 6H2O

Yeşılel

Ölmez

Soylu

2006

Transition Met Chem

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New adducts of ethylenediamine (en), N,N-dimethylethylenediamine (ndmen) and N,N¢-dimethylethylenediamine (dmen) with squarate as counter-ions were synthesized and characterized by physico-chemical methods (IR and UV/ vis spectroscopy, magnetic susceptibility and thermoanalytical measurements). The crystal structure of tris(ethylenediamine)cobalt(III) 1.5 squarate hexahydrate, [Co(en) 3 ](sq) 1.5 AE 6H 2 O, was determined by single crystal X-ray diffraction. Co(III), Ni(II) and Cu(II) ions in the monomeric octahedral tris(ethylenediamine)cobalt(III) 1.5 squarate hexahydrate (1), tris(ethylenediamine)nickel(II) squarate 0.5 hydrate (2) and diaquabis(ethylenediamine)copper(II) squarate dihydrate (3) are chelated by ethylenediamines through two amine nitrogen atoms. Cu(II) atoms in the diaquabis(ndmen)copper(II) squarate (4) and diaquabis(dmen)copper(II) squarate (5) monomeric octahedral complexes are coordinated by ndmen and dmen molecules through two amine nitrogen atoms in a bidentate chelating manner. Water molecules complete the octahedral coordination. The orange (1), violet (4) and violet (5) complexes upon heating transform to claret, green and green species on dehydration, respectively, which revert immediately after cooling in the open atmosphere. The violet (3) complex upon heating loses water molecules yielding a deep blue dehydrated species, which on further heating undergoes an exothermic phase transition accompanied by thermochromism, deep blue to brown in the solid state. The decomposition mechanism and thermal stability of the solid complexes are interpreted in terms of their structures. The final decomposition products -the respective metal oxides -were identified by IR spectroscopy.

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Chromogenic Materials, Thermochromic

Greenberg

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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Thermochromism is a reversible change in spectral properties as a result of heating and cooling. Usually the response is visible. It is observed in complexed metals, in both inorganic and organic materials generally, and in all phases of matter, though predominately in solids and solutions. There are thousands of examples in the solid and liquid phases, a few examples of which are given here. These examples have been selected to indicate the scope of transition mecanisms tat contribute to this interesting chromogenic materials category. The breadth of the subject is evident from the bibliography. It includes, on the one hand, literature that has been generated in the circle of the inorganic chemist, as well as references that are from the literature of the physicist and also the organic chemist. Indeed, thermochromism is an encompassing subject.

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Thermochromism in copper(II) halide salts. 4. Bis(diethylammonium)tetrachlorocuprate(II), structure of the high-temperature phase and physical characterization of its two phases

Cited by 72 publications

References 0 publications

Electronic spectra and nature of transitions in [NH2(C2H5)2]2CuxZn1−x Cl4 (x = 0.5, 1) crystals

Electronic spectra and nature of transitions in [NH2(C2H5)2]2CuxZn1−x Cl4 (x = 0.5, 1) crystals

Synthesis and Spectrothermal Studies of Thermochromic Diamine Complexes of Cobalt(III), Nickel(II) and Copper(II) Squarate. Crystal Structure of [Co(en)3](sq)1.5 · 6H2O

Chromogenic Materials, Thermochromic

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