Study of the Polymorphism in Copper(II) Decanoate through Its Phase Diagram with Decanoic Acid, and Texture of the Columnar Thermotropic Liquid Crystal Developable Domains in This and Similar Systems

Abstract

A new third polymorph of copper(II) decanoate has been found by two methods: from the crystallization of the salt− acid solution and from a specific thermal treatment of the polymorph obtained in n-heptane. The new polymorph, whose crystal structure has been solved for the first time, is the most stable from the thermodynamic point of view. It presents a bilayer structure, but with two different types of paddle-wheels catenae with opposite orientations. This polymorphism as well as the temperature vs composition phase diagram of the system, [(1 − x) C 9 H 21 CO 2 H + (x) (C 9 H 21 CO 2 ) 2 Cu], were solved by differential scanning calorimetry, Fourier transform infrared spectroscopy, Xray diffraction, pair distribution function, and optical microscopy. The singularities of the phase diagram are (a) a Krafft-like process of molecular association of the copper(II) decanoate into the acid solution, at about T = 361.5 K and x = 0.022 (forming salt-acid adducts of 1:1 stoichiometry); (b) a fusion transition as an invariant (T = 379.1 K) of the solid salt in excess from the copper(II) decanoate crystal phase to the discotic liquid crystal, forming homeotropic developable domains (seen for the first time in these systems) of the pure salt into the saturated acid solution. These domains are seen not only in the copper(II) decanoate but also in other members of the series, at high salt concentration in the corresponding acid solution, and allow identification of the hexagonal columnar discotic structure of the mesophase (with the exception of the copper(II) butanoate, where the tetragonal domains with tilted disks, paddle-wheels, were seen in the same salt−acid region).

Production and Characterization of a New Copper(II) Propanoate-Isonicotinamide Adduct Obtained via Slow Evaporation and using Supercritical CO2 as an Antisolvent

“…Figure a,b shows the structures of Cu­(C 3 ) 2 and the Cu 2 (C 3 ) 4 (INA) 4 adduct obtained at 100 K. The color change from the original cyan of the Cu­(C 3 ) 2 to a lighter blue can be attributed to the change in the coordination of the copper from five (square pyramidal) in the alkanoate to six (distorted octahedral) in the adduct. The paddle-wheel structure of Cu­(C 3 ) 2 is constructed by four bridging carboxylate ligands (μ 3 ) that form catenae in a one-dimensional (1D) coordination polymer arrangement (Figure a), typical of all the Cu­(II) alkanoates. − The paddle wheels, and therefore the catenae, disappear in the new complex, where two-metal units are coordinated by two bridging (μ 2 ) and two chelating carboxylates (μ 2 ) from the propionate anions, and four N atoms from INA molecules. Each Cu ion in the binuclear unit is coordinated by four O atoms (two of them from two different bridging carboxylates, and the other two from the chelating carboxylate), in the plane approximately, while the N atoms are in the apical vertices of the distorted octahedron (see Figure b).…”

“…The synthesis and behavior of copper­(II) alkanoates has been widely studied during the last decades. − The paddle-wheel configuration in which the carboxylate ligands bond both copper­(II) atoms with a bridging ligand confers on these compounds interesting features. They present monotropic polymorphism and mesomorphism, as a hexagonal columnar discotic liquid crystal .…”

Unraveling the Decomposition Process of Lead(II) Acetate: Anhydrous Polymorphs, Hydrates, and Byproducts and Room Temperature Phosphorescence

“…Anhydrous lead­(II) acetate belongs to the family of metal alkanoates, which have shown their ability to present polymorphism − and/or polymesomorphism . ,− In particular, the lead­(II) alkanoate series has been studied in depth for some decades. − These compounds present two mesophases, rotator (members with n ≥ 4, with n being the number of C atoms) , and a liquid-crystal phase (6 ≤ n ≤ 12). The shortest members of the series ( n ≤ 7) ,, show also a great tendency to form different kinds of glass states: regular, rotator, and liquid-crystal glasses .…”

New Advances in the One-Dimensional Coordination Polymer Copper(II) Alkanoates Series: Monotropic Polymorphism and Mesomorphism

“…The texture in the CDLC observed by optical microscopy consists of developable domains (Figure 13, part 4), which in fact are honeycomb structures in which the director axis (in this case, the direction of the 1D coordination polymer) is bent and grows in a spiral. 75,76 The distance (H) has also been observed in the highly concentrated mixtures of the decanoic acid− copper(II) decanoate phase diagram, 25 where the same developable domains are formed in the CDLC phase (see Figure SI.18, Supporting Information).…”

“…Copper­(II) alkanoates have been studied for a long time by a number of authors, − using a great variety of techniques (DCS, DTA, FTIR, − Raman, , and NMR spectroscopies, dilatometry, conductance, EXAFS, , and single crystal − and powder , X-ray diffraction). Moreover, there are several reviews discussing general aspects of the copper­(II) alkanoate series.…”