Unusual folded structures for a tethered squaraine-cholesterol derivative in Langmuir-Blodgett films

A squaraine-cholesterol diad, 1, which has been found to be a good gelator, has been studied in films at the air-water inter face and in supported Lan gmuir-Blodgett films. Both experimental observations and simulations are co nsistent with a low-energy folded structure in which there are attractive n oncovalent interactions between the squaraine chromophore and the steroid. Although different structures seem Likely for 1 in both the crystal and org anogels, the present studies suggest that the folded structure exists in bo th uncompressed and compressed films at the air-water interface and in supp orted LB films. In both environments the squaraine chromophore shows eviden ce of squaraine-squaraine aggregation; both "J" and "H" aggregates are indi cated depending upon the conditions imposed upon the film.