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 interface and in supported Langmuir−Blodgett films. Both experimental observations and simulations are consistent with a low-energy folded structure in which there are attractive noncovalent interactions between the squaraine chromophore and the steroid. Although different structures seem likely for 1 in both the crystal and organogels, the present studies suggest that the folded structure exists in both uncompressed and compressed films at the air−water interface and in supported LB films. In both environments the squaraine chromophore shows evidence of squaraine−squaraine aggregation; both “J” and “H” aggregates are indicated depending upon the conditions imposed upon the film.