(31)P NMR study of Na(2)CuP(2)O(7): an S = 1/2 two dimensional Heisenberg antiferromagnetic system

Cs2CuP2O7, a novel low-density open-framework structure based upon an augmented diamond net

The crystal structure of Cs2CuP2O7 [monoclinic, Cc, a=7.460(6), b=12.973(10), c=9.980(8) Å, β=111.95(2)°, V=895.8(12) Å3] prepared by solid-state reactions is based upon open framework formed by corner sharing between CuO4 distorted squares and P2O7 groups. The framework is porous and has a very low framework density of 13.4 Cu+P atoms per 1 nm3. Cs+ cations reside in large framework cavities. The heteropolyhedral network in the title compound is based upon three-dimensional (3;4)-connected net that has a three-membered CuP2 ring as its elementary unit. In terms of reticular chemistry, this net should be considered as an augmented diamond (dia) net. The Cu–P net can be obtained from the latter by the replacement of its nodes by the CuP2 triangles. This replacement is strongly non-centrosymmetric, since all CuP2 triangles are oriented along the same direction, which provides a crystal chemical explanation for the absence of a symmetry centre in the structure. Cs2CuP2O7 is the first compound in the A2CuP2O7 family (A=alkaline metal), which is based upon three-dimensional copper pyrophosphate framework.

Breathing some new life into an old topic: chalcogen-nitrogen π-heterocycles as electron acceptors

Recent progress in the design, synthesis and characterization of chalcogen-nitrogen π-heterocycles, mostly 1,2,5-chalcogenadiazoles (chalcogen: S, Se and Te) and their fused derivatives, possessing positive electron affinity is discussed together with their use in preparation of charge-transfer complexes and radical-anion salts-candidate building blocks of molecule-based electrical and magnetic functional materials.

Electronic structure of Na(2)CuP(2)O(7): a nearly 2D Heisenberg antiferromagnetic system

We have employed first principles calculations to study the electronic structure and the implications for the magnetic properties of Na(2)CuP(2)O(7). Using the self-consistent tight-binding linearized muffin-tin orbital method and the Nth-order muffin-tin orbital downfolding method, we have calculated the various intrachain and interchain hopping parameters between the magnetic Cu(2+) ions. Our calculations for Na(2)CuP(2)O(7) reveal dominant intrachain hopping, but in contrast to the typical quantum spin chains the interchain hoppings are not negligible. The Wannier function plot of the Cu d(x(2)-y(2)) orbitals shows that the exchange interactions are primarily mediated by the oxygens and the distance between the oxygens in Na(2)CuP(2)O(7) is favorable for both intrachain and interchain interactions, suggesting the inapplicability of the one-dimensional Heisenberg model for this system, in agreement with recent experimental results.