Cooperativity of dynamics of 18-crown-6 molecule forming one-dimensional chain in Cs2(18-crown-6)3[Ni(dmit)2]2

Abstract

Heat capacity of Cs2(18-crown-6)3[Ni(dmit)2]2 was measured by adiabatic calorimetry. A broad thermal anomaly was observed around 225 K. The entropy gain (about 52 J K(-1) mol(-1)) is much larger than that expected for twofold disordering of 18-crown-6 assumed in the previous structure analysis. The shape of thermal anomaly was qualitatively explained by a linear Ising model developed for cooperative disordering in polymers. The 18-crown-6 molecules forming a one-dimensional chain in the crystal are orientationally disordered with moderate cooperativity.

Elucidation of Structure and Dynamics in Solid Octafluoronaphthalene from Combined NMR, Diffraction, And Molecular Dynamics Studies

“…the small molecular jumps which provide the mechanism for the full rotation of the molecules). In particular, correlated motions are seen to modify the energy landscape explored by a system in a nontrivial way and must be understood if the goal of creating effective molecular machines is to be realized. , Molecular dynamics simulations are uniquely suited to looking at these effects and are highly complementary to experimental NMR studies in probing complex motional processes.…”

Formation of p-Phenylenediamine−Crown Ether−[PMo12O40]4- Salts

“…In this context, we have been introducing supramolecular cation structures between inorganic or organic cations and crown ethers as the countercations of [Ni(dmit) 2 ] (dmit 2- = 2-thioxo-1,3-dithiole-4,5-dithiolate). − This approach allows us to modify and modulate the assembled structures of the [Ni(dmit) 2 ] - anions in the crystal and thus to modify the magnetic properties of the [Ni(dmit) 2 ] - salts . By using this approach, relatively large and complex cations, which consist of an organic ammonium cation such as anilinium and p -phenylenediammonium (H 2 PPD 2+ ), with crown ethers were also introduced into the crystal, which gave rise to a spin ladder of interactions of S = 1 / 2 spin on [Ni(dmit) 2 ] - anions …”

Supramolecular Rotor: Adamantylammonium([18]crown-6) in [Ni(dmit)2]- Salt

“…We have previously introduced supramolecular cations of ammonium−crown ether molecular assemblies in electrically conducting and magnetically active [Ni(dmit) 2 ] salts (dmit 2- = 2-thione-1,3-dithiole-4,5-dithiolate). , This approach allows us to design structurally diverse cations in the [Ni(dmit) 2 ] crystals. For example, the simple combination of alkali-metal ions (M + ) and crown ethers yielded a molecular rotator of (Cs + ) 2 ([18]crown-6) 3 in [Ni(dmit) 2 ] salts. , Quaternary ammoniums (R−NH 3 + ) are capable of forming molecular assemblies of (R−NH 3 + )([18]crown-6) in solids, where the size of the −NH 3 + moiety fits the cavity of [18]crown-6 . On the basis of these designing strategies, we have already reported the supramolecular cations of (R−NH 3 + )([18]crown-6) in the [Ni(dmit) 2 ] - salts .…”

“…The Δ H B value at low temperature corresponds to the line width of the sharp signal (motional ADNH 3 + unit).

3 Temperature dependence of the full width at half-maximum (Δ H A : open circles) and the peak-to-peak line width of the differential spectrum (Δ H B : filled circles) of 1 H NMR for salt 1 together with Δ H A of salt 2 (triangles) 8a. The inset shows the temperature variation of 1 H NMR spectra at (i) 360 K, (ii) 230 K, and (iii) 120 K.

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“…The Δ H A value in the temperature range above 250 K was ∼20 kHz, while that at 120 K (Δ H A = 40 kHz) was twice that at room temperature. Lowering of the temperature was observed to lead to broadening of the Δ H A value in the temperature range from 360 to 120 K. The molecular rotation of [18]crown-6 in (Cs + ) 2 ([18]crown-6) 3 [Ni(dmit) 2 ] - 2 ( 2 ) has been identified as a thermally activated motion in the temperature range above 220 K, resulting in a rapid decrease in Δ H A from 60 kHz ( T < 220 K) to ∼8 kHz ( T > 220 K) as shown in Figure (triangles) 8a. The Δ H A value of thermally frozen [18]crown-6 has been estimated as ∼60 kHz in salt 2 ,8a suggesting that the maximum rotation frequency of [18]crown-6 at 220 K was about 60 kHz.…”