GROUND AND EXCITED-STATE CHIROPTICAL PROPERTIES OF ENANTIOPURE MACROCYCLIC TETRANAPHTHYL LANTHANIDE COMPLEXES - CONTROLLED MODULATION OF THE FREQUENCY AND POLARIZATION OF EMITTED LIGHT

Circular dichroism spectroscopy has revealed that strong exciton coupl ing occurs between adjacent pairs of 1-naphthyl chromophores in the ch iral sodium, calcium and europium complexes of the macrocyclic tetraam ide L-1a/b. In constitutionally isomeric complexes involving a 2-napht hyl linkage, L-2a/b, intramolecular excimer formation is observed by f luorescence emission spectroscopy as being strongest in the protonated ligand itself. The terbium and europium complexes show a well-defined circularly polarised luminescence that is independent of the nature o f excitation: UV excitation at 300 nm via the proximate naphthyl anten nae in [Tb.L-1a](3+) and [Tb.L-1b](3+) followed by intramolecular ener gy transfer results in mirror-image circularly polarised emission spec tra. The lanthanide complex serves to modulate both the frequency and polarisation of the incident light in a controlled manner.