Chiral Interconversions of Pd and/or Au Bis-Metalated [32]Octaphyrins(1,0,1,0,1,0,1,0) Involving Hu?ckel and Mo?bius Macrocyclic Topologies: A Theoretical Prediction

摘要

Several Pd and/or Au bis-metalated [32]-noctaphyrins(1,0,1,0,1,0,1,0) were theoretically designed with richnconformations of Hückel or Möbius topology. The conformationsnand hence properties of macrocycles were tuned by twisting thenactive pyrrolic ring either clockwise (through multistep reactionsnwith several Hückel and Möbius macrocyclic intermediates) ornanticlockwise (via a direct Hückel−Hückel chiral interconversion).nThe encapsulated metal atoms, M1, M2 = Pd, Au, give differentnimpacts on these two reaction processes. Facile occurrences ofnchiral interconversions between two enantiomers of bis-metalatednoctaphyrins were predicted with the largest activation barrier lessnthan 40 kcal/mol. Some Au-coordinated octaphyrins (M1 = Au)nwere demonstrated to be thermodynamically stable with largennegative nucleus-independent chemical shift (NICS) values, whichnare comparable to those of the synthetic Pd-coordinatedncomplexes. The free-base [32]octaphyrins(1,0,1,0,1,0,1,0) displaynthe characteristic absorption spectra with distinct sharp Soret-likenbands. After metalation, the Soret-like bands are red-shifted in different degrees along with the appearance of rather weak Q-likenband. The heterometal-coordinated complexes (i.e., M1 ≠ M2) show stronger and more splitting absorptions than thenhomometal-coordinated ones with M1 = M2. The hyperpolarizabilities sharply augment with the metalation in Hückel systemsndue to the destruction of the centrosymmetry and the increase in polarizability by coordinated metal atoms.