Structure of a System Report

A polymeric structure can be generated by intermolecular coordination of a metalloporphyrin equipped with a suitable ligand. Fleischer (18,90) solved the crystal structure of a zinc porphyrin with one 4-pyridyl group attached at the meso position. In the solid state, a coordination polymer is formed (75, Fig. 30). The authors reported that the open polymer persists in solution, but the association constant of 3 x 104 M 1 is rather high, and it seems more likely, in the light of later work on closed macrocycles (see above), that this system forms a cyclic tetramer at 10-3 M concentrations in solution (71,73). 

Olanzapine appears to exist in at least five polymorphic forms, and the structure of Form II has been reported [32]. Two molecules form centrosymmetric dimmers stabilized by a series of C—H - rc interactions, and the dimmers are connected by a system of intermolecular N—C—and C—H S hydrogen bonds. The structure of a monoclinic polymorph of isoxsuprine hydrochloride has been reported [33], The molecular conformation existing in the new monoclinic polymorph was found to be very similar to that existing in the known triclinic polymorph. 

We have only just started to explore empirical access to FMO parameters based on these similarities 52). Recently, others have reported empirical equations for calculating IP s and EA s for a variety of Ji-bonded systems 64). This approach used a large number of parameters for the underlying rc-system, heteroatom substitution, and the substituents on the 7t-system. However, we aim at calculating FMO parameters from fundamental atomic data while taking due account of the bond structure of a molecule. 

Odelius and co-workers reported some time ago an important study involving a combined quantum chemistry and molecular dynamics (MD) simulation of the ZFS fluctuations in aqueous Ni(II) (128). The ab initio calculations for hexa-aquo Ni(II) complex were used to generate an expression for the ZFS as a function of the distortions of the idealized 7), symmetry of the complex along the normal modes of Eg and T2s symmetries. An MD simulation provided a 200 ps trajectory of motion of a system consisting of a Ni(II) ion and 255 water molecules, which was analyzed in terms of the structure and dynamics of the first solvation shell of the ion. The fluctuations of the structure could be converted in the time variation of the ZFS. The distribution of eigenvalues of ZFS tensor was found to be consistent with the rhombic, rather than axial, symmetry of the tensor, which prompted the development of the analytical theory mentioned above (89). The time-correlation... 

The closely related dilithiated compound 208, also with a central four-membered ring, was obtained from starting compound 207 in DME (Scheme 71). The molecule represents the first bis(aUyl)dianion system consisting of six carbon atoms involving eight jt electrons (6C-8 7r). The crystal structure of 208 was reported . ... 

The crystal structure of a type A azapentalene, a substituted derivative of pyrazolo [ 3,4-dlthi azole 284, has been reported,370 but it would be desirable to have information on unsubstituted type A systems, as well as on derivatives of type B lacking sulfur. 

Antohi (34) has reported several possible isozyme structures of a malic acid decarboxylating enzyme in Bacillus subtilis, and Peak (35) has reported the same in Euglena gracilis this must be kept in mind for the Leuconostoc oenos system. It is possible that the enzymatic activities that we have reported (6,7,8) may be the result of isozyme interactions of the same protein. 

Although the structures of a series of 6-substituted 4-methoxypyran-2-ones have been established by chemical means, their alternative formulation as derivatives of 2-methoxy-pyran-4-ones was mainly excluded on the basis of an absorption at 1733 cm-1 attributable to the pyran-2-one system (59JA2427). This report concludes that pyran-2-ones exhibit their first carbonyl band at ca. 1725 cm-1, whereas pyran-4-ones absorb at ca. 1667 cm-1. Similarly, absorption at 1724 cm-1 indicated a pyran-2-one structure for yangonin (98), the major constituent of kava resin, and this has been confirmed by an unambiguous synthesis. Pseudoyangonin (99) absorbs at 1667 cm-1, characteristic of a pyran-4-one (60JCS502). Comparison of the spectra of some constituents of the rosewoods with that of yangonin established them as pyran-2-ones. The products from the reaction of malonyl chloride with some 1,3-diketones were identified in part by IR spectroscopy. 

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