Synthesis and Photophysical Studies of Chiral Helical Macrocyclic Scaffolds via Coordination-Driven Self-Assembly of 1,8,9,16-Tetraethynyltetraphenylene. Formation of Monometallic Platinum(II) and Dimetallic Platinum(II)-Ruthenium(II) Complexes

This paper is concerned with the synthesis and reactions of enantiopure 1,8,9,16-tetraethynyltetraphenylene (3). We obtained 3 in 34% yield through four steps starting from 1,8,9,16-tetrahydroxytetraphenylene (2a) via a functional group interconversion strategy. On the basis of this chiral helical building block, three rigid helical macrocycles 14, 15, and 22 were designed. Complexes 14 and 15 were constructed via coordination-driven self-assembly with platinum(II) complexes 8 and 9b, while 22 cannot be obtained successfully. Then macrocycle 28 was designed on the structural basis of 22 to which octyl chains were introduced, in the hope of improving the solubility of the complex. Macrocycle 28 was finally formed and was characterized by NMR spectroscopy, elemental analysis, and electrospray mass spectrometry. For the enantiopure 15 and 28, circular dichroism (CD) spectra also exhibited chiral properties. Complexes 27 aid 28 both exhibited an intense emission band at 621 nm in acetonitrile at 298 K upon excitation at lambda > 420 nm.