Theoretical study on a family of organic molecules with planar tetracoordinate carbon

Based on the most stable structure of C3B2H4 and its substitution of H with -Cl, -CH2OH, -CHOH, -CO and -COOH groups, a series of derivatives containing the planar tetracoordinate carbon (ptC) atoms as well as crown ether-like compounds from the assembling of C3B2H4 units have been constructed. At the B3LYP/6-311++G** and MP2/6-31G** levels of theory, these ptC compounds were predicted to be stable and they generally have large HOMO-LUMO gaps. The IR characteristic bands arising from the symmetrical and asymmetrical stretching vibrations of C-ptC, the stretching vibrations of C-B and B-H as well as the breath vibration of the two three-membered rings of C3B2 appear at 1000, 1250, 1600, 2800, and 1700 cm−1, respectively. Calculations also show that these ptC molecules have strong aromaticities and the ptC atom obeys the octal rule. Furthermore, the derivatives C3B2H2(COOH)2 and tetra-C3B2H2-16-crown-4 can serve as the chelate ligands and form stable complexes with uranyl.