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Solids: background theory
Published in Michael de Podesta, Understanding the Properties of Matter, 2020
Notice that the repulsive component in Equation 6.42 is one twelfth of the attractive component. The expression yields the cohesive energy per ion in a simple-cubic ionic solid. In order to convert this into a cohesive energy per mole, we must multiply this figure by the number of formula units in a mole. Note that in the simple two-component ionic solids we have been considering, each chemical formula unit contains two ions (e.g. Na+ and Cl−). We therefore expect to find that the cohesive energy per mole for such a substance is: () U=2NAu mol−1
Introduction
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
To get from the microscopic level to the macroscopic scale, a quantity known as “the mole” (abbreviated mol) is defined. A mole of items, regardless of size, shape, or color, all of which are assumed to be identical, is equal to 6.022 × 1023. This is a constant and is referred to as Avogadro’s number. When one mole of atoms of an element is collected, the atoms have a collective mass (molecular mass for a molecule, or a formula mass for a formula unit) in grams. For comparison sake, one dollar bill or one small paper clip has a mass of about 1 gram. The more general term used to refer to either molecular mass or formula mass is molar mass.
Cu(II) complexes with coordinated pyrazine-dioxide: pyrazine-bridged chains
Published in Journal of Coordination Chemistry, 2022
Christopher P. Landee, Diane A. Dickie, Mark M. Turnbull, Jan L. Wikaira
The disorder of the tetrafluoroborate anion and the partial occupancy lattice water molecule are intimately related (see Figure SI.1). The anion is two-site disordered and refined to occupancies of 0.582(4)/0.418(4). The partial lattice water molecule refined independently to an occupancy of 0.418(7), identical to that of the minor BF4− component. In terms of space, this is logical as the major BF4- component and the water molecule would overlap if both were present at the same time. When present, the water molecule serves as a hydrogen bond donor to the BF4− anion and to the uncoordinated pzdo oxygen atom (O14) and as a hydrogen bond acceptor to the coordinated lattice water molecule (see Table 3). It should be noted that the water content from X-ray refinement, while close, does not agree with the combustion analysis data which indicate the presence of one lattice water molecule per formula unit. Once isolated from the mother liquor, the crystals are not stable indefinitely (stability is clearly dependent upon the relative humidity), which we associate with the loss of the lattice water molecule.
Two 3D Cd(II) coordination polymers pillared by linear ligand: synthesis, structure and luminescent properties
Published in Inorganic and Nano-Metal Chemistry, 2021
Qiao-Zhen Sun, Hao Liu, Bo Zhao, Yan-Ling Ai, Hao-Zhe Jin, Bing-Guang Zhang
In order to verify the thermal stability of compounds 1 and 2, TG analysis the two complexes was performed under N2 atmosphere with a heating rate of 10 °C/min. For 1, the first weight loss of 3.82% over the range of 82–162 °C is attributed to the removal of one lattice water and one coordinated water molecule per formula unit (calcd = 3.62%). Then, the whole framework begins to decompose (Figure 3). For 2, the first weight loss of 8.68% over the range of 95–287 °C is attributed to the removal of one lattice water and two coordinated water molecules per formula unit (calcd = 8.48%). Then, the whole framework begins to decompose. Powder X-ray diffraction experiments were carried out for 1 and 2. The patterns for the bulk product are in fair agreement with the patterns based on single-crystal X-ray solution in position, indicating the phase purity of the as-synthesized samples (Figure 4).
2D ferrous nitroprussides stabilized through organic molecules as pillars: preparation, crystal structure and related properties
Published in Journal of Coordination Chemistry, 2021
Y. Avila, J. Rodríguez-Hernández, P. M. Crespo, M. González M., E. Reguera
The information derived from the recorded TG traces could be summarized as follows: 1) the formed solids have anhydrous character, which is congruent with the IR results; 2) in the interlayer region two organic molecules per formula unit are found, except for 4-(2-pyridin-4-ylethyl)pyridine, where the weight loss corresponds to the evolution of only one molecule; 3) the axial NO and CN ligands evolve at relatively low temperature, which is associated to the activation of transversal vibrational modes, facilitating the rupture of their Fe-NO and Fe-CNAxial bonds in the nitroprusside ion, a mechanism that could explain the lower stability for molecules that do not form bridges between neighboring layers, e.g. 1,3-oxazole, 1H-pyrazole, etc. According to the IR and TG results, the formula unit for the solids considered herein is Fe(L)2[Fe(CN)5NO] for L = 1,3-oxazole, 1H-pyrazole, pyridazine, imidazo[1,2-a]pyridine, and pyridine-3-carbaldehyde; and Fe(L)[Fe(CN)5NO] with 4-(2-pyridin-4-ylethyl)pyridine. These formula units are congruent with the results obtained from the structural study (discussed below).