Inclusion of Methyl 2-Naphthalenecarboxylate and Dimethyl 2,3-, 2,6-, and 2,7-Naphthalenedicarboxylates by Cyclodextrins in Aqueous Solution

Abstract

Abstract In aqueous solution, inclusion complexes of several naphthalenecarboxylate derivatives with α-, β-, γ-, and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (α-CD, β-CD, γ-CD, and TM-β-CD) have been investigated by means of absorption and fluorescence spectroscopy. β-CD and TM-β-CD form 1:1 inclusion complexes with methyl 2-naphthalenecarboxylate (2NC), dimethyl 2,7-naphthalenedicarboxylate (27DNC), dimethyl 2,6-naphthalenedicarboxylate (26DNC), and dimethyl 2,3-naphthalenedicarboxylate (23DNC). α-CD forms a 2:1 α-CD–2NC inclusion complex as well as a 1:1 inclusion complex with 2NC. With 27DNC, α-CD forms a 1:1 inclusion complex alone, whereas α-CD forms a 2:1 α-CD–guest inclusion complex with 26DNC. γ-CD forms 1:1 inclusion complexes with all the naphthalenecarboxylate derivatives examined. In addition to the 1:1 inclusion complex, γ-CD forms a 2:2 γ-CD–guest inclusion complex with 27DNC (or 26DNC) through the association of the 1:1 inclusion complexes. From the 2:2 inclusion complex, the excimer fluorescence of the guest has been observed. In the case of 23DNC, γ-CD forms a 1:2 γ-CD–guest inclusion complex, from which no excimer fluorescence has been observed.