Dualists of two-dimensional and three-dimensional classes of molecules: benzenoids and diamondoids
Presented by Prof. Balaban ALEXANDRU
Type: Keynote Lecture
The traditional allotropic forms of carbon, multilayer graphene and diamond, are “honorary hydrocarbons” with huge numbers of carbon atoms surrounded by a negligible number of hydrogen atoms. Enumerations of benzenoids should consider both definitions, including or excluding helicenes. Dualists offer simple classifications for catafusenes, perifusenes, and coronoids as having acyclic, triangular, or larger rings, respectively. Catafusenes can be encoded simply by means of numbers formed by digits 0, 1, 2. Eric Clar developed a ‘winner-takes-all’ theory for aromatic sextets. Claromatics are the most stable among isomers. Biparametric correlations in terms of numbers of rings and of longest acene chains operate well in QSAR. Dias produced formula periodic tables for benzenoids based on two types of quaternary carbons. Diamondoids can be classified into catamantanes (regular or irregular), perimantanes, and coronamantanes according to their dualists, which are isomorphic to staggered alkane rotamers. The Balaban-Schleyer simple coding of catamantanes in terms of numbers formed by digits 1,2,3,4 is now generally accepted based on their dualists. Diamondoids can also be grouped in formula periodic tables using partitioned formulas according to quaternary, tertiary, and secondary CHn goups (n = 0, 1, and 2, respectively), and information about their dualists. The table for regular catamantanes presents interesting symmetries, but for irregular ones the situation is more complicated and not fully understood. Invariants for dualists helped in assigning structures to chromatographically separated diamondoids from petroleum. A few computational challenges are listed.