Design of Molecular Chains Based on the Planar Tetracoordinate Carbon Unit C2Al4

B3LYP DFT study revealed that the planar tetracoordinate carbon (ptC) molecules, C2Al4E8 (E = CH3, NH2, and OH), could be condensed to one-dimensional molecular chains containing planar or quasi-planar C2Al4 units by eliminating CH4, NH3, and H2O molecules. Natural bond orbital analyses indicate that the electronic structures of C2Al4 moieties in the chains, including ionic and covalent bonding, do not change significantly in comparison with those of the free C2Al4E8 (E = CH3, NH2, and OH) ptC species. The reason for the structural evolution from ptC units to the molecular chains is discussed. Because of the eliminations of stable hydride molecules (CH4, NH3, and H2O), the condensations are thermodynamically favorable, which implies the promise to synthesize the materials experimentally.