Existence Of Isomerism Research Articles

Isomerism in double-pillared-layer coordination polymers - structures and photoreactivity.

The existence of isomerism in coordination polymeric structures offers opportunities to understand structure-function relationships. Herein the serendipitous isolation is reported of two isomeric double-pillared-layer coordination polymeric structures arising from two different types of carboxyl-ate bonding of benzene-1,4-di-carboxyl-ate ligands to zinc(II), which constitutes a new type of structural isomerism. The different bonding modes not only alter the shape and size of the pores, but also the nature of interpenetration and photoreactivity. Although two trans,cis,trans-bpeb ligands with conjugated olefin bonds are aligned in close proximity in both of the structures, one isomer undergoes a double [2 + 2] cyclo-addition reaction and the second isomer only offers an incomplete single cyclo-addition product. This work demonstrates how small changes in the structural connectivity can have an impact on the overall structural, physical and chemical properties of such materials.

Nuclear data sheets for A = 194

Spectroscopic data for known nuclei of A=194 (Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At) have been evaluated and presented with adopted level properties and associated γ rays. No experimental data exist on 194Hf and 194W, but amongst other nuclides in heavy mass region these have been included and nuclear structure calculations by 85Ro21, 85He14, 84Sa16, and 83Ba47. Except for the isotopic identification, nothing much is known about the level structure of 194Bi, 194Po, and 194At. Since the 1997 evaluation of A=194 (77Ha46), the following are the main additions to the present revision: excited state data are now available for 194Os through a 2-neutron transfer reaction and for 194Tl from 194Pb ɛ decay and (Hl,xn γ) study. New high spin data for 194Au, 194Hg, 194Tl, and 194Pb from in—beam γ—ray studies reveal band structures. A new isomer is tentatively identified in 194Bi; its ɛ decay reveals a low lying 0+ state as the first excited state in 194Pb. From α decay studies, 194At isotope has been identified. Further experimental work is needed in the following causes: in a recent neutron capture work on 194Ir, only about 60 of the 900 reported γ rays can be placed in a level scheme, although a large number of levels are indicated from primary γ rays. The existence of isomerism in 194Bi remains to be confirmed through a more detailed study of 194Bi ɛ decay. The radioactive decays of 194Os (6.0 y), 194Ir (31.85 ms), and 194Tl (33.0 min and 32.8 min) need more definitive work. The newly discovered first excited state in 194Pb with J π=0+ has been interpreted as the starting member of a collective band; however, high—spin members of such a band have not yet been found in the (hl,xn γ) studies of 194Pb.

Fourier transform infrared spectroscopy of the zeolite NaH–Y + but-1-ene system

The kinetics of transformation of but-1-ene on zeolite NaH–Y with differing degrees of Na+ ion exchange was investigated at room temperature by Fourier transform infrared spectroscopy. The process of oligomerization was detected and the existence of isomerization, polymerization, dismutation, cracking and dehydrogenation were confirmed. Evidence was found that the protons which replaced sodium ions in the zeolite are heterogeneous.