Small molecule complexes crystal structures

The structural information available on the reduced state of Cu2Zu2 SOD provides a view of the copper site as a very flexible system, where the Cud) ion can shift between three- and four-coordination with a water molecule weakly interacting with it, giving rise to 4 -I- 1 coordination. The latter coordination is commonly observed in small molecule complexes [a recent example is provided by Lee et al. (S6)]. It is noteworthy to point out that a concerted movement of the metal and of some of the ligands seems responsible for the coordination changes observed in the reduced yeast SOD and bovine SOD structures. In the case of yeast SOD it appears that reduction of the copper ion occurs on C5n"stallization and that crystal packing does not play a role in the process. On the contrary, in the bovine SOD example, pH and the solution-like environment of one of the subunits seem to be responsible for the probable detachment of the His-61 from Cu(I). 

The compounds M(NH3)2Ni(CN)4 (M = Zn or Cd), which consist of two-dimensional polymeric sheets of tetracyanonickelate ions bridged by coordinating diamminemetal(n) cations, function as host lattices for clathration of small aromatic molecules such as thiophene, furan, pyrrole or pyridine IR studies indicate the presence of hydrogen bonding between the host lattice ammonia and the aromatic guest molecules.A crystal structure determination of the related clathrate Cd(en)Ni(CN)4(pyrrole)2 has been reported. Similarly, the complex Cd(py)2Ni(CN)4 consists of polymeric [Cd— Ni(CN)4] layers held together by Cd-bound pyridine. 

C. X-Ray Crystal Structures of Lead(II) Small Molecule Complexes... 

The PDB contains 20 254 experimentally determined 3D structures (November, 2002) of macromolecules (nucleic adds, proteins, and viruses). In addition, it contains data on complexes of proteins with small-molecule ligands. Besides information on the structure, e.g., sequence details (primary and secondary structure information, etc.), atomic coordinates, crystallization conditions, structure factors. 

Structural aspects were discussed, but not heavily, in the first edition. The complexity of new compounds (and macromolecules) now being investigated has driven many of the technological advances in X-ray crystallographic data collection and structure solution over the last two decades. Small-molecule (m.w. < 1,000 g mol-1) structure determinations are now routinely carried out, and Co complexes constitute a significant proportion of these. Indeed, the incorporation of crystal structures in most papers reporting new synthetic coordination chemistry is now a standard feature much more so than at the time of CCC(1987) (Figure 1). Inevitably, most of the new compounds described herein have been the subject of crystal structure determinations, rather... 

One example of a cocrystal containing BEDT-TTF and ferrocene has been reported [104]. The [(BEDT-TTF Cgob lferrocene) adduct was crystallized from a carbon disulfide solution. The unit cell has been determined by single crystal X-ray diffraction but the crystal structure was not reported. An infrared spectroscopic analysis indicates that the charge transfer between the BEDT-TTF and C6o molecules is quite small. It has been suggested that such complexes may offer a means to introduce iron into the fullerene lattice. 

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