Lariat ethers 12 and 13 with appended phenanthridine fluorophoric units have been prepared as potential fluorescent chemosensor molecules for alkaline metal salts possessing aromatic anions. The starting 8-ethyloxycarbonylamino-6-methylphenanthridine (1) was converted via 2, 3, 6 and 7 to N-(2-tosylethyl)-derivatives 4 and 8 suitable for N-alkylations of diaza- and aza-18-crown-6. However, the alkylations failed, giving the 2-oxazolidinone derivative 5 formed by intramolecular cyclization of phenanthridine N-carbamate derivatives 4 and 8 in basic conditions. The phenanthridine derivative 10 having benzyl instead carbamate protection on 8-amino group successfully alkylated mono- and diaza-crown ethers, giving lariats 12 and 14. Subsequent removal of benzyl protection groups in acidic conditions gave lariats 13 and 15. Lariat 12 was found to form unique Na- and K-picrate complexes with the metal cation bound in the crown cavity and picrate anion intercalated between phenanthridine units
