Jong-Hee Kang

Synthesis of and Fluorescent Imaging with a Polymer Having t-BOC-Protected Quinizarin Moieties

The generation of patterned images in polymer films has been extensively studied and used in fundamental and applied research areas. The development of patterned color or fluorescent images, especially, is of great technological importance in the electronics industry. Recently, the generation of functional images by selective immobilization of organic dyes in the polymer film has been reported. Selective removal of acid-labile protecting groups through photoinduced chemical transformation followed by chemisorption of organic dyes from solution into the patterned polymer film has given micrometer-scale functional images. The two-step procedures described in the literature, however, have potential problems such as difficulty of dye penetration into polymer matrices and concern about longterm stability of the patterned images. To avoid these limitations, we have tried to develop a direct method of generating fluorescence images with a precursor molecule. The strategic basis for designing a precursor is that the precursor molecule is non-fluorescent and/or colorless, but becomes fluorescent and/or reveals color by photoinduced chemical changes. We have previously reported that the UV absorption maximum and fluorescence of quinizarin 1 can be readily altered and manipulated simply by blocking the intramolecular hydrogen bonds. Thus, the UV absorption maximum (479 nm) of quinizarin 1 shifts to a shorter wavelength (335 nm) on blocking the two phenols with two tert-butoxycarbonyl (t-BOC) groups. In addition, the t-BOC-protected quinizarin 2 has virtually no fluorescence, whereas quinizarin 1 is strongly fluorescent due to the quasi-aromatic structure caused by intramolecular hydrogen bonding. As a part of our continuing interest in the generation of relief and functional images with transiently protected precursor molecules in polymer films, we now report the synthesis of a novel polymer having t-BOC-protected quinizarin moieties and the generation of color and fluorescent images by photolithographic methods. To our knowledge, this is the first example of finely resolved fluorescent images with a polymer having transiently protected precursor pendants. The strategies employed for the synthesis of t-BOC-protected quinizarin monomer 7 are shown in Scheme 1. Aldol