Perfect in-Plane [5555] Metallo-Annulene Frameworks and Nonmetallo-Annulene Complexes: A Theoretical Prediction

Inspired by the newly discovered in-plane [55555] metallo-annulene frameworks in 3D [Os]C₁₅H₁₀ ([Os] = OsL¹L² and L represents PPh₃, CO, or PEt₃ σ-ligands in axial direction) and recently proposed perfect 2D in-plane [55555] metallo-annulene complexes D_{5 h} MC₁₅H₁₀ (M = Pt, Pd, Ni), based on extensive first-principles theory calculations, we predict herein a series of perfect in-plane [5555] metallo-annulene frameworks in 3D D_{4 h} [Fe]C₁₂H₈ (1, [Fe] = Fe(CO)₂) and D_{4 h} [Co]C₁₂H₈ ⁺ (2, [Co] = Co(CO)₂) and perfect 2D in-plane [5555] nonmetallo-annulene complexes including D_{4 h} PC₁₂H₈ ^- (3), D_{4 h} SC₁₂H₈ (4), and D_{4 h} ClC₁₂H₈ ⁺ (5). Detailed bonding pattern and ring current analyses indicate that planar tetracoordinate metal or nonmetal centers participate in the delocalized π-bonding systems of the annulene complexes, rendering π-aromaticity and extra stability to the systems. Such species with a planar [12]C₁₂H₈ annulene ligand can be enlarged in 2D to form the C_{4 v} [Fe]C₃₆H₁₆ (6), D_{4 h} [Co]C₃₆H₁₆ ⁺ (7), D_{4 h} PC₃₆H₁₆ ^- (8), D_{4 h} SC₃₆H₁₆ (9), and C_s ClC₃₆H₁₆ ⁺ (10) and expanded in 3D to generate the tubular nanobelt C_{2 v} (SC₁₂H₄)₁₂ (11) via partial dehydrogenations. The NMR, IR, and UV-vis spectra of the most concerned species 1-5 are computationally simulated to facilitate their future experimental characterizations.