Sixty-Year Saga (1952–2013) of the Solid-State Structure of Triiron Dodecacarbonyl

This article presents the personal saga of one of the authors (LFD) in the determination of the solid-state structure of Fe₃(CO)₁₂. We also present the results of our recent determination of its solid-state structure at low temperature (100 K), in which we have used a modern area-detector diffractometer in order to examine more precisely its temperature-dependent structural variations reported by Braga et al. in 1994 from a point-detector diffractometer. These investigations provide a striking illustration of the remarkable advances over the last six decades in both computational hardware and software packages as well as the recent improvements in hardware data-collection instrumentation that have given rise to X-ray crystallography now being the most powerful (and in most cases the only unambiguous) physical method for elucidating the static structures of complex metal clusters. Other experimental measurements and resulting speculations concerning the dynamic/fluxional behavior of Fe₃(CO)₁₂ and closely related analogues in the solid state and in solution are briefly mentioned, as are recent theoretical analyses.     

Comparative analysis of structure and temperature behaviour of two copolyamides - regular KEVLAR and statistical ARMOS

In the present investigation X-ray diffraction techniques, DSC and dynamic mechanical relaxation (DMR) methods have been employed to compare the structure and thermal behaviour of Kevlar (“DuPont”, USA) and Armos (Russia) fibers. Our recent studies have indicated that the non-crystalline phase of copolyesters always contains LC smectic structure in addition to some part of the nematic LC mesophase. It turned out that the copolyamides also possess this interesting feature. Moreover, on heating of a semicrystalline copolyester always the second order phase transition from the crystalline state to condis mesophase has been observed, whereas in the case of copolyamides such a transition has the «virtual» character. As was established by other authors both polymers under study reveal the moisture content. The changes in wide angle X-ray scattering of copolyamides under heat treatment were interpreted in terms of desorption of bound water and structural rearrangement in the plane perpendicular to the chain axis involving of the hydrogen bonding between neighboring macromolecules.