Normally,
you expect the two compounds of the same composition premises
connectivity, atom by atom and symmetry that are chemically identical. But
the scientists who investigate metal organic frameworks have discovered
a surprising exception to this rule by identifying the two isomers with
the same symmetry and bound but different gas storage properties.
A
team led by Ma Shengqian at Argonne National Laboratory, Illinois, USA,
investigating the molecular tetracarboxylate like twigs (ebdc) that can
be attached to a metal atom from any part of the bonds at four points,
one piece at each corner of the rectangle. When
the salt is heated with a bronze at 75 ° C, a crystalline phase is
formed (-phase) and a temperature of 65 ° C a phase with the property -
a property different forms (-phase). So far, it looks normal. But
when Ma completed analysis on two crystalline compounds, he found that
they have the same composition, the same atom to atom connectivity and
the same symmetry. "Another type of symmetry which maintains isomerism has not been studied previously in metal organic frameworks," said Ma.
Isomers have the same symmetry but different properties = properties
The key to what happened lies in the ligand, clearly Ma. In-phase, multiple ligands attached end to end on each unit of the copper, which on their phase-bound neighbors. This makes the big ring in-phase than in-phase. Thus,
although the same chemical units joined together - with the same kind
of bond and the overall symmetry of the same, the property - the
property is still different. In
particular, the area available for hydrogen absorption was
significantly higher in-isomer: 'This means that it is possible to
boost gas storage capacity by finding isomers - a new isomer of unknown
structure, "said Ma. Paul
Forster, a materials chemist at the University of Nevada, Las Vegas,
USA, was fascinated by what he calls a form of isomerism is 'very
unusual'. 'Structure
- a structure that is identical in composition and connectivity, but
differ on the hole geometry, providing a unique and important
opportunity to address questions related to the kinetics and
thermodynamics of the synthesis of hybrid materials, "he said.
