Amine selective coloration with chromoacerands
Amine selective complexation of some azophenol-dyed crowns with concurrent coloration and molecular structures of two sec. amine-dyed crown complexes are reported as well as selective colorations of enantiomeric amines with chiral azophenol crowns and of diamines with bisazophenol crown. INTRODUCTION A variety of complexes and inclusion compounds between tcationic or neutral guest and neutral host, e.g. crowns, cryptands, cyclodextrins, and antibiotics has been studied to develop the phase-transfer catalysis and to elucidate the mechanism of enzyme/substrate and naturally occurring ionophore /metal cation interactions so far. On the other hand, studies on complexation involving the coulombic attractive force between oppositely charged hosts and guests have been expected to draw a new trend in molecular recognition, since this additional binding force will affect the stability and selectivity of the complex other than ion-dipole interaction and/or hydrogen bonding. Previously we reported design and syntheses of a series of ligands which c selectively bind a given metal ion and undergo concurrently color ch gel e.g. lithium ion selective color tion with azophenol-dyed crowns?7 and azophenol spherand-like cyclophanefj, sion with benzothiazolylphenol crowns,'j and their application to lithium ion analyses. BP thium ion specific fluorescent emisAMINE SELECTIVE COMPLEXATION-COLORATION5 Now we wish to report selective complexation of protonated amines by the use of azophenol crowns 1-6 and podand 7 which have a phenol group in the cavity to yield the corresponding ammonium phenolate complex 1 0 (Scheme 1 ). The colored complex 1 0 must be differentiated from simple ion-dipole type complexes by an additional binding force, that is, coulombic interaction between the host phenolate anion and the guest ammonium cation. We recently observed such a perching type complexation of protonated amines by the phenolate anion and ether oxygens of the azophenol crowns.