Synthesis, structures and properties of self-assembling quaternary ammonium dansyl fluorescent tags for porous and non-porous surfaces.

A series of H2O and/or EtOH soluble, self-assembling quaternary ammonium salts containing a dansyl (DNS) fluorescent moiety suitable for attachment to both porous ([DNS-NH-(CH2)3-NMe2-R+][X-] (2; R = -Si(OMe)3, X- = Cl-) and non-porous (3a; R = -PO(OEt)2, 3b; -PO(Oi-Pr)2, 3c; -(PO(OH)2, X- = Br-), 4; ([DNS-NH-(CH2)3-NMe2-(CH2)3-NH(CH2PO(OEt)2)2 +][Br-], 5; R = -((CH2)3SCOCH3, X- = Cl-), 6a; (R = -(CH2)nO(C6H4)CO(C6H5), n = 3, X- = Br-, 6b; n = 3, X- = Cl-, 6c; n = 3, X- = I-, 6d; n = 4, X- = Br-, 6e; n = 4, X- = I-, 6f; n = 6, X- = Br-, 6g; n = 6, X- = Cl-, 6h; n = 6, X- = I-), 7; (R = -CH2-CH[double bond, length as m-dash]CH2, X- = Br-) surfaces were prepared from the precursor dansyl amine (1; DNS-NH-(CH2)3-NMe2). Compounds 1-7 were characterized by NMR (1H, 13C, 29Si (2), 31P (3a-c, 4)) spectroscopy, HRMS, UV-Vis and fluorescence spectroscopy. Additional characterization of compounds 1 and 7 were carried out by X-ray structure determinations. Physical attachment of compound 2 to cotton surfaces after immersion in solutions containing fluorescent dyes was verified by exposure to UV light and by complexation with bromo-phenol blue that rendered the surfaces visibly blue in colour. Phosphorus containing dansyl fluorescent dye, 3c, was attached to a stainless steel surface by exposure to an aqueous solution containing this dye, resulting in the formation of a self-assembled fluorescent monolayer. UV cure of plastic surfaces (polypropylene, silicon medical tubing) coated with compound 6a resulted in the covalent attachment of the dyes.