Organochalcogen-nitrogen heterocycles such as the 1,2,5-chalcogenadiazoles have a distinct tendency to establish intermolecular links in the solid state through secondary bonding interactions E...N (E = S, Se, Te). The association of these molecules was examined in detail using relativistic density functional theory. Although there is an important electrostatic component, the interaction between these molecules is dominated by contributions arising from orbital mixing, which can be interpreted as the donation of a nitrogen lone pair into the chalcogen-centered antibonding orbitals. Because of its more polar character and lower-lying antibonding orbitals, the tellurium derivatives possess the strongest association energies; these are so large that the binding strength is comparable to that of some hydrogen bonds. In the absence of steric constraints, telluradiazoles associate in a coplanar fashion forming ribbon polymers. However, bulky susbstituents could be used to direct the formation of either helical chains or discrete dimers. In addition to its strength, the coplanar dimer is characterized by being rigid, yet no activation barrier is expected for the association/dissociation process. These attributes strongly indicate that tellurium-nitrogen heterocycles have great potential as building blocks in supramolecular architecture.

Metal-organic network solids [1] represent a compromise between wholly inorganic frameworks and wholly organic solids. While this is a self-evident statement with respect to the composition of the solids, the physical properties of the networks can also be of an intermediate nature. This type of compromise is illustrated by the thermal robustness of representative metal-organic solids and, consequently, their ability to sustain pores. Pores in any solid are typically sustained by very strong bonding to compensate for the loss in enthalpy associated with creating a void. While stability is certainly a corollary of stronger bonding, another often observed, and less desirable, consequence is a loss of longrange order. Essentially, in such cases, the growth of a network assembly from solution is sufficiently rapid that the product precipitates before an ordered assembly can be achieved, resulting in loss of crystallinity. With respect to porous solids, this rapid precipitation leads to a high dispersity of pore sizes and, hence, to non-uniform sorption properties.Organophosphonates have been extensively studied as strongly coordinating ligands for prototypical hybrid inorganic-organic layered solids, [2] owing to their propensity to bridge a broad range of metal centers into two-dimensional sheets. With respect to porous solids, simple monophosphonate or linear diphosphonate ligands pack too efficiently to enable the formation of void space between the pillaring groups of the ligands. Smaller phosphonate or phosphate ions can be interspersed between the larger phosphonate pillars, but regular pores do not necessarily result, as the substitution is not necessarily regular.[3] More recent efforts to generate porosity have focused on using polyphosphonate ligands to disfavor the formation of simple layers [4][5][6] or on using template routes to form regular pores.[7] However, in general, there is an antagonistic relationship between stability and order for metal phosphonate solids: those that are robust enough to sustain pores do not typically retain high degrees of crystallinity, and, conversely, crystalline samples often do not sustain permanent pores (as shown by gas sorption).The promise of metal-organic frameworks (MOFs) has been exemplified by recent successes in gas storage and separation by materials constructed primarily from carboxylate and pyridyl ligands.[8] With metal carboxylates, the secondary building unit (SBU) approach has been successfully employed. [9] In this methodology, an organic linker with a coordinatively divergent geometry is coupled with a welldefined metal-ligand assembly (typically a cluster) to form open frameworks by design. The metal carboxylate clusters typically targeted are those with a high tendency to form with monocarboxylate anions. Thus, these SBUs play a true structure-directing role.With simple monophosphonate ligands, the default metalorganic structure formed is a simple layer. The extension of this motif to an open structure cannot be achieved without a major perturbation...

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It is estimated that about 7,000 billion barrels of oil will remain in reservoirs after production by conventional methods. This value is the target for Enhanced Oil Recovery (EOR) techniques. The purpose of the water-soluble polymers in EOR application is to enhance the rheological properties of the displacing fluids. These polymers have been successfully implemented in China’s oilfields. Given the harsh conditions present in most oil reservoirs, new problems and challenges arise with the use of such polymers. Currently partially hydrolyzed polyacrylamides (HP AMs) are the major class of polymers used for chemical EOR application. However, due to the high flexibility of HP AM chain in aqueous solutions, particularly at high temperature (HT) and at high salinity (HS), the molecular chains begin to fold irreversibly resulting in a significant loss in viscosity. In this paper, we are reporting a bench-scale development of new PAM-based polymers with improved performance in HSHT conditions. The new polymers were evaluated conditions for their viscosity performance at various temperatures and salinities. The polymers were dissolved at different concentrations in brines with TDS (Total Dissolved Solids) of 34,655 ppm and 180,000 ppm. Viscosity measured at room temperature is in the range of 30 to 120 cP at the shear rate of 6 RPM. After aging at 90 °C and 120 °C for six months under ultralow oxygen level (< 5 ppb), viscosity remains relatively stable for some polymers while show a decline for others. Compared with the conventional HPAM polymers, these new polymers have much better stability at HTHS conditions.