Bis[bis­(methoxy­carbimido)amine‐κ2N,N′]bis­(perchlorato‐κO)copper(II) bis­[bis­(methoxy­carbimido)amine‐κ2N,N′]bis­(methanol‐κO)copper(II) bis­(perchlorate) methanol disolvate

The title compound, [Cu(ClO₄)₂(C₄H₉N₃O₂)₂][Cu(C₄H₉N₃O₂)₂(CH₄O)₂](ClO₄)₂·2CH₃OH, comprises two independent Cu^II species lying on different inversion sites. In the Cu complexes, a distorted octa­hedral geometry arises (from basic square‐planar N₄ coordination) from the weak coordination of two perchlorate ions (as Cu—O) in one species and two methanol mol­ecules in the other (also as Cu—O). Inter­actions between the O atoms of the perchlorate anions or methanol groups and the imide or amine NH groups afford an extensive inter­molecular hydrogen‐bonding network.     

Electrochemical formation and clevage of bis-imidazolyls

Bis-(2,4,5-triphenylimidazolyls) result from the dimerization of 2,4,5-triphenylimidazolyls and from the nucleophilic attack of 2,4,5-triphenylimidazole anions upon 2,4,5-triphenylimidazolylium cations. The isomeric bis-imidazolyls consist of imidazole and isoimidazole systems. Imidazoles undergo only anodic oxidation, isoimidazoles only cathodic reduction. Therefore the bis-imidazolyls may be analyzed from their electrochemical behaviour. Bis-(2,4,5-triphenylimidazolyl)-1,2′ and bis-(2,4,5-triphenylimidazolyl)-1,4′ undergo reductive bond cleavage in an ē.c?.ē. mechanism from which 2,4,5-triphenyl-imidazole anions result. The electrochemical properties of one of the bis-imidazolyls agree with that of 1,4,5-triphenyl-2-(2,4,5-triphenylisoimidazolyl-4)-imidazole and not with that of bis-(2,4,5-triphenylimidazolyl)-2,4′ as reported in literature.     

Thermodynamic properties of the spin-Peierls transition in CuGeO3

We present an investigation of the spin-Peierls transition atT _SP=14.5 K in polycrystalline CuGeO₃ through specific-heat and thermal-expansion measurements. Clear second-order phase-transition anomalies are found in both properties atT _SP, although only a small entropy of S0.1 Rn2 is released at the transition. Most of the entropy is released atT _SP<T<150 K, where the temperature dependence of the magnetic contribution to the specific heat as well as the thermal expansion exhibit extrema atT ^*40 K. These are caused by one-dimensional antiferromagnetic fluctuations along the Cu chains, possibly accompanied by structural fluctuations. Using Ehrenfest's relation, a hydrostatic pressure coefficient (T _SP/_p)_p0 (0.45±0.06) K/kbar is derived.