Rosettes dimer

The method of preparation of the catalyst has been found to alter the effect of the promoter (196). With standard VPO prepared with an organic solvent, the effects of cobalt and of iron were found to be the same as those previously described 182,193-195,202,208). The improvement in catalytic performance is proposed to be a consequence of the stabilization of dimers, which are the proposed active sites. However, catalysts prepared from V0P04 2H2O in organic solvents are not characterized by a promotional effect of iron. This lack of promotion is attributed to the loss of crystallinity and surface area of the rosette crystals formed by in the preparation. Similarly, the increase in activity attributed to cobalt is thought to be a structural effect, influencing the development of the (100) plane of (VO)2P207. 

Anionic Rosette Ribbon Built of Guanidinium and Hydrogen Carbonate Dimer... 

Each supramolecular rosette comprises a quasihexagonal assembly of two GM+ and four HC units connected by strong Nqm-H- -Ohc and Ohc-H- -Ohc hydrogen bonds. The (HC )2 dimer is shared as a common edge of adjacent rosettes and makes full use of its remaining acceptor sites in linking with GM+. However, each GM+ in... 

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