Transformations in Thin Solid Layers: The Reversible Polymerization-Depolymerization of 2,6-Di-n-propyl- l,3>5,7-tetraoxa-2,6-dibora-4,8-octalindiones at Low Temperatures

The course of Aggregation of molecules of the title compound ( lb) through different, spectroscopically discernible and chemically identifiable forms of associations could be followed by matrix isolation and thin film infrared and UV-visible spectroscopy. It was found that molecules of l b in thin films form clusters which at low temperatures interact weakly, probably through the carbonyl oxygens of one and the boron atoms of the neighbouring molecules. On warming to 260 K this association gradually takes the form of more defined chelate bonds, probably with ordered three-dimensional intermolecular structures. Above this temperature spontaneous formation of crystallites of the previously reported 'hot' and 'cold' modifications was observed. Studies with films of varying thickness indicate an interdependence of crystallite size and lattice energies.