Monothiophene IT and Derivatives

There are only few investigations on thin films of small oligomers. 

On metals, vacuum evaporated quaterthiophene (a-4T) films on Ag(lll) and solution deposited films of o -2T-a-4T on Ag sols have been studied. 

This behavior is quite similar to that of end-capped quaterthiophene [150]. Two different monolayer phases are found, a compressed saturated monolayer below 494K and a relaxed monolayer at low coverages and/or after heating the sample above 494K. This structural phase transition is reversible. 

On Ag sols molecules lie mainly flat on the surface, as determined from SERS (surface enhanced Raman spectroscopy) measurements. However, the molecules are twisted and there is evidence for a small inclination against the surface. The twisting decreases and the inclination increases with increasing chain length [151-153]. 

The observed twisting of the molecules is in fine with crystal powder X-ray diffraction data (see section 4.2.2). 

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