1,8‐Dipyrenylnaphthalenes: Syntheses, Molecular Structure, and Spectroscopic Properties

Syntheses of the 1,8‐dipyrenylnaphthalenes 1 – 3 are reported. The stereoisomers 1 and 2 were separated; their structural assignment is based on 1 H NMR, on the optical activity of 2 , and on X‐ray structure analyses of 1 and 2 . Kinetic parameters for the isomerisation 2 ⇌ 1 were determined by optical rotation measurements. – Emission spectra of 1 – 3 are discussed in comparison to monopyrenyl compounds 4 and 8 . For 1 and 3 typical ‘excimer‐like’ fluorescence is observed. The difference between 1 and 2 clearly demonstrates the dependence of excimer interactions between the pyrene units on the mutual orientation of the π‐systems involved. – On the basis of X‐ray analyses the molecular structures of 1 – 3 are discussed with emphasis on π…π‐interactions between the pyrene units.