Design of Carborane Molecular Architectures via Electronic Structure Computations

Quantum-mechanical electronic structure computations were employed to explore initial steps towards a comprehensive design of polycarborane architectures through assembly of molecular units. Aspects considered were (i) the striking modification of geometrical parameters through substitution, (ii) endohedral carboranes and proposed ejection mechanisms for energy/ion/atom/energy storage/transport, (iii) the excited state character in single and dimeric molecular units, and (iv) higher architectural constructs. A goal of this work is to find optimal architectures where atom/ion/energy/spin transport within carborane superclusters is feasible in order to modernize and improve future photoenergy processes

Structure and bonding of CH<SUB>2</SUB>Li<SUB>2</SUB> dimers

As models for polymeric dilithiomethane, a number of head-to-tail andhead-to-head CH<SUB>2</SUB>Li<SUB>2 </SUB> dimer structures were optimized by means of ab initio molecular orbital calculations using the RHF/STO-3G minimal basis method. Split valence basis RHF/4-31G single point calculations indicated VIII, with four lithium atoms bridging two perpendicular CH<SUB>2</SUB> units, to be the most stable geometry for (CH<SUB>2</SUB>Li<SUB>2</SUB>)<SUB>2</SUB>. The dimerization energy at this level of theory, 37 kcal/mole, is already considerable; it should be even larger with higher association. Possible trimer and polymer structures are suggested