Dual phosphorescence from 2,3-naphtho-17-crown-5 ether in ethanol glass at 77 K

2,3-naphtho-17-crown-5 ether (I) shows an unusual dual phosphorescence in EtOH and MeOH glass at 77 K as a function of concentration of I. Compound I exhibits, however, single phosphorescence in 2-methyl tetrahydrofuran glass at 77 K in the same concentration range. Crown ethers containing six oxygen atoms do not show any dual phosphorescence at 77 K in EtOH glass in the same concentration range. The lifetime of the T-1 states of the ethers in various matrices and the phosphorescence and the lifetimes of the complexes of I with Tl+, Cs+ and K+ are reported, The blue-shifted emission of I in alcohol glass at 77 K at higher concentration is attributed to emission from a dimer of I having a ground state stabilised compared to that of the monomer of I.