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The empirical Clar model describes the π-electronic configurations for polycyclic aromatic hydrocarbons with closed-shell singlet ground states. However, it is not applicable to nanographenes (NGs), which usually have open-shell ground states. To model the π-electronic configurations of NGs, a new structural unit, radical half-sextet, was introduced. The modified Clar model can profoundly depict the π-electronic configurations for both nonmagnetic and magnetic NGs and thus can be used as the general model for NGs. The new model can precisely predict the favorable reaction patterns for NGs and can profoundly explain the already-known reactions of NGs.

The Lewis base stabilized borylenes and boryls are used to construct one dimension nanowires. Using the Lewis base (L) to coordinate sp2 borons, we constructed B5L5− cyclic compounds with six π-electrons. Then, using B5L5 and transition metals as building units, we further constructed half-sandwich and sandwich compounds. We found that the B5(CO)5 is the η5-ligand with stronger bonding affinity with Mn and Fe than the traditional cyclopentadiene. The calculated electronic band structures suggested that the constructed nanowire [VB5(CO)5FeB5(CO)5]∞ is an organic half-metal. The results may cast light on the future synthesis of boron-based metallocene-like molecules.

Here we establish a fundamental principle to open a relatively large band gap for graphene by hydrogenation. Specifically, the large band gap can be obtained when the number of nonmagnetic sp(2)-substructures on graphene basal plane is maximized. The principle indicates unequivocally what additive patterning should be used to attain the largest band gap for a given addition coverage. According to this principle, the graphene band gap can be continuously tuned from 0 to 5.2 eV. These findings may open a door to create graphene-based nanosystems with desired band gaps, and will become a significant foundation for graphene nanotechnology applications. (C) 2012 Elsevier B.V. All rights reserved.

A recently synthesized new molecule C131 (C60 C C70) is studied using the MNDO, AM1, PM3 and B3LYP methods. [6.6]-8 isomer is the most stable structure of C131. To create C60 C C70, the C70 cage thermodynamically prefers to open bond at the equatorial region. The strain analysis performed for the pristine C70 (D5h) and C70 in C131 revealed that the cycloaddition reaction occurring with the equatorial C–C bond can lead to a larger strain release than occurring with the polar C–C bond of C70. The results provide new insights to understand the observations of C60 C C70 as well as the previously reported C70 C C70 and C70O.