Synthesis of New Cholesterol- and Sugar-Anchored Squaraine Dyes: Further Evidence of How Electronic Factors Influence Dye Formation Kuthanapillil Jyothish, Rekha R. Avirah, and Danaboyina Ramaiah* Photosciences and Photonics DiVision, Regional Research Laboratory (CSIR), TriVandrum 695 019, India d_ramaiah@rediffmail.com; rama@csrrltrd.ren.nic.in Received October 31, 2005 ABSTRACT Synthesis of new quinaldine-based squaraine dyes linked to cellular recognition elements that exhibit near-infrared absorption (>740 nm) are described. Both product analysis and theoretical calculations substantiate the interesting electronic effects of various substituents in the dye formation reaction. These results are useful in the synthesis of symmetrical and unsymmetrical squaraine dyes that can have potential biological and photodynamic therapeutical applications. Squaraine dyes have been the subject of many recent investigations. 1 The current interest in these dyes may be attributed to their interesting photochemical and photophysi- cal properties, 2 which make them attractive for a variety of applications. These include photoconductors in organic solar cells, 3 photoreceptors in copiers and laser printers, 4 IR absorbers in organic optical disks, 5 sensors for metal ions, 1e-g and as sensitizers for photodynamic therapeutical (PDT) applications. 6 Squaraine dyes in general can be considered as acceptors in conjugation with two donors D-A-D. The donor molecules can be the same or different giving rise to (1) (a) Kukrer, B.; Akkaya, E. U. Tetrahedron Lett. 1999, 40, 9125. (b) Xie, J.; Comeau, A. B.; Seto, C. T. Org. Lett. 2004, 6, 83. (c) Ros-Lis, J. V.; Garcia, B.; Jimenez, D.; Martinez-Manez, R.; Sancenon, F.; Soto, J.; Gonzalvo, F.; Valldecabres, M. C. J. Am. Chem. Soc. 2004, 126, 4064. (d) Arunkumar, E.; Forbes, C. C.; Noll, B. C.; Smith, B. D. J. Am. Chem. Soc. 2005, 127, 3288. (e) Bablo Block, M. A.; Hecht, S. Macromolecules 2004, 37, 4761. (f) Arunkumar, E.; Ajayaghosh, A.; Daub, J. J. Am. Chem. Soc. 2005, 127, 3156. (g) Wallace, K. J.; Gray, M.; Zhong, Z.; Lynch, V. M.; Anslyn, E. V. Dalton Trans. 2005, 2436. (h) Arun, K. T.; Ramaiah, D. J. Phys. Chem. A 2005, 109, 5571. (2) (a) Liang, K.; Farahat, M. S.; Perlstein, J.; Law, K. Y.; Whitten, D. G. J. Am. Chem. Soc. 1997, 119, 830. (b) Chen, H.; Farahat, M. S.; Law, K. Y.; Whitten, D. G. J. Am. Chem. Soc. 1996, 118, 2584. (c) Das, S.; Thomas, K. G.; Kamat, P. V.; George, M. V. J. Phys. Chem. 1994, 98, 9291. (d) Law, K. Y. Chem. ReV. 1993, 93, 449. (e) Kamat, P. V.; Das, S.; Thomas, K. G.; George, M. V. J. Phys. Chem. 1992, 96, 195. (3) (a) Law, K. Y.; Bailey, F. C. J. Imaging Sci. 1987, 31, 172. (b) Tam, A. C.; Balanson, R. D. IBM J. Res. DeVelop. 1982, 26, 186. (4) (a) Fabian, J.; Nakazumi, H.; Matsuoka, M. Chem. ReV. 1992, 92, 1197. (b) Emmelius, M.; Pawlowski, G.; Vollmann, H. W. Angew. Chem., Int. Ed. Engl. 1989, 28, 1445. (5) (a) Liang, K. N.; Law, K. Y.; Whitten, D. G. J. Phys. Chem. 1995, 99, 16704. (b) Piechowski, A. P.; Bird, G. R.; Morel, D. L.; Stogryn, E. L. J. Phys. Chem. 1984, 88, 934. (c) Loufty, R. O.; Hsiao, C. K.; Kazmaier, P. M. Photogr. Sci. Eng. 1983, 27, 5. (6) (a) Ramaiah, D.; Joy, A.; Chandrasekhar, N.; Eldho, N. V.; Das, S.; George, M. V. Photochem. Photobiol. 1997, 65, 783. (b) Ramaiah, D.; Eckert, I.; Arun, K. T.; Weidenfeller, L.; Epe, B. Photochem. Photobiol. 2002, 76, 672. (c) Arun, K. T.; Epe, B.; Ramaiah, D. J. Phys. Chem. B 2002, 106, 11622. (d) Ramaiah, D.; Eckert, I.; Arun, K. T.; Weidenfeller, L.; Epe, B. Photochem. Photobiol. 2004, 79, 99. (e) Beverina, L.; Abbotto, A.; Landenna, M.; Cerminara, M.; Tubino, R.; Meinardi, F.; Bradamante, S.; Pagani, G. A. Org. Lett. 2005, 7, 4257. ORGANIC LETTERS 2006 Vol. 8, No. 1 111-114 10.1021/ol052639j CCC: $33.50 © 2006 American Chemical Society Published on Web 12/08/2005