Current Inorganic Chemistry (Discontinued) - Volume 4, Issue 3, 2014

Octacyanometalate-based coordination polymers are known to display an array of interesting physical and chemical properties. The presence of d electronic metals in these compounds leads to both orbital and spin contributions to uncompensated magnetic moments responsible for a rich variety of their magnetic properties. The different connectivity of metal ions leads to systems with different network dimensionality. The subclass of three-dimensional coordination polymers displays a long-range magnetic order at sufficiently low temperatures, which is revealed by the presence of a heat capacity anomaly. In the temperature and field dependence of the anomalous contributions to the heat capacity in these systems valuable information concerning the character of the ordered phase is encoded. The present review focuses on thermal properties of several particular examples of molecular magnets based on octacyanometalates and showing a longrange magnetic order. Methods of extraction of magnetic contribution to the total heat capacity are presented and discussed. Behavior of heat capacity and entropy close to the critical temperature as well as magnetocaloric effect are analyzed.

Water molecule is very simple in its structure and tends to form tetrahedrally arranged hydrogen bonds with other molecules. Bulk water inevitably crystallizes without being supercooled over 235 K even in a droplet with a diameter of µm. Water confined within nm spaces, being abundantly present on the earth, behaves differently from the bulk one. In this article, thermal properties of channel water confined in nanopores with hydrophilic crystalline and silica noncrystalline walls are elucidated with special attention paid to how the configurational-ordering and glass-transition phenomena depend on the pore-wall attributes and pore diameter. The former water even serves to stabilize formation of the crystalline complex framework and reveals a phase transition due to the ordering of the configuration of water molecules close to pore wall at low temperatures. Since the hydrogen-bond network formed is not conformable to that in pure water, however, the water molecules located in the pore center are left disordered with increasing the pore diameter. The latter water located in the center of pores with silica non-crystalline walls reveals intriguing pore-diameter dependence of the glass-transition temperature implying the formation of an ordered structure intrinsic to the low-temperature liquid water, while the interfacial water of one-molecular layer remains disordered without forming tetrahedrally arranged hydrogen bonds. This implication is experimentally supported by appearance of a first-order liquid-liquid phase transition in the water doped with hydroxylamine of a small amount. The information obtained must be useful to potential applications of various types of materials possessing such confined water; especially, it contributes to the issues of gas storage and fuel cells that are relevant to the structure and dynamics of confined water.

A kind of molecule-based magnets, metal-assembled complexes tend to possess low-dimensionalities for their magnetic lattices. Heat capacity calorimetry is a powerful tool for elucidation of the magnetic properties of metal-assembled complexes. Heat capacity measurements were carried out for the one-dimensional metal-assembled complexes MnIICuII(obbz).nH2O (obbz = oxamidobis(benzoato), n = 1, 5) and two-dimensional metal-assembled complexes NBu4[MIICrIII(ox)3] (Bu = n-butyl; M = Cu, Fe; ox = oxalato) and PPh4[MnIICrIII(ox)3] (Ph = phenyl). MnIICuII(obbz).5H2O undergoes an antiferromagnetic phase transition at TN = 2.18 K and have a heat capacity hump above TN, which can be reproduced well by the spin quantum number S = 2 one-dimensional ferromagnetic Heisenberg model with the intrachain exchange interaction J/kB = 0.75 K, where kB is the Boltzmann constant. Partially dehydrated MnIICuII(obbz).H2O exhibits a ferrimagnetic phase transition at Tc = 17 K and shows a heat capacity tail above Tc, which can be reproduced rather by the S = 2 two-dimensional ferromagnetic Heisenberg models. NBu4[CuIICrIII(ox)3], NBu4[FeIICrIII(ox)3], and PPh4[MnCr(ox)3] indicate ferromagnetic phase transitions at TC = 6.98 K, 12.0 K, and 5.85 K, respectively, and heat capacity tails above TC, which can be reproduced well by the two-dimensional ferromagnetic Heisenberg models of honeycomb lattice with the intralayer exchange interactions J/kB = 5.0 K, 2.5 K, and 0.95 K, respectively.

Graphene (G) and Graphene oxide (GO) are nontoxic and inexpensive two dimensional (2D) materials, which are stable at room temperature. Since the discovery of their electronic, optical, mechanical, thermal and chemical nature, G and GO have been adopted for numerous fascinating applications. In this review we discuss the possibility of employing G/GO as solid electrolyte/proton conductors, ferromagnets, electrodes or electron mediators in enzyme biosensors and as an ingredient of hybrid photocatalysts for water splitting. Both the pure form of G/GO and their selective hybrids and derivatives have been considered for discussion in each section. Nowadays, it is difficult to classify G or GO related researches separately. In most cases the functionality and application of G are necessarily associated with GO synthesis, its modification and subsequent reduction to G. However, the reduction of GO to G or reduced graphene oxide (rGO) is the source of various defects, holes, imperfections, semi hydrogenation state and band gap. All these influences affect most of the properties and utility of G/GO. Therefore, in this review we attempt to discuss functions with respect to both G and GO.