Boron - The Forgotten Element? Clusterization of Physical-Chemistry, Materials Science, Biochemistry and Mathematics

J.Z. DAVALOS; R. NOTARIO; M. CANLE-L.; J.A. SANTABALLA; M.I. FERNANDEZ; D.J. KLEIN; D. BHATTACHARYA; V. ROSENFELD; J. RUE; D.R. ALCOBA; G.E. MASSACCESI; O.B. OÑA; A. TORRE; L. LAIN; D. HNYK; J. HOLUB; M. LONDESBOROUGH; A. FRANCES-MONERRIS; D. ROCA-SANJUAN; N.L. ALLAN; C. VIÑAS; F. TEIXIDOR; J.M. OLIVA

La Coruña

Congreso; XXXV Reunión Bienal de la Real Sociedad Española de Química; 2015

Real Sociedad Española de Química

Since the disclosure of borane compounds, used for rocket fuel in the 1950s during the Soviet Union - USA space career, an enormous amount of literature of synthesis of boranes and their derivatives has appeared in the literature [1]. In the last 15 years we have been involved with the determination of the electronic structure of heteroborane derivatives, such as carboranes, as ground states [2] and excited states [3]. The knowledge of the electronic structure of molecular architectures built from polyhedral heteroboranes, through quantum chemical computations, leads to very interesting results, such as the possibility of using chains, rings and three-dimensional structures as molecular magnets [4], the use of borane structures to produce new lasers [5], and the determination of the yet-unknown role of boron, if any, in biology [6]; the {massatomic}(%) content of boron in human beings is {70}x10^-6 !, as compared to {3.1} and {18} for nitrogen and carbon respectively. Why do we have such tiny amounts of boron as compared to carbon or nitrogen? Why does boron have such rich architectural molecular constructs as compared to nitrogen? As compared to carbon, there is only a difference of one electron! Clusterization of boron compounds - polyhedral (metala)heteroboranes - is due to the need of satisfying (quantum) valencies when combined - namely, a chemical bond - but having less electrons than carbon; hence clusterization occurs, such as in the icosahedral dianion B12H12 2-. We also use the construction of hypothetically stable borane structures by concatenating pentagonal structures (energy minima) in order to study unsolved problems in mathematics, such as the number of (symmetry-unique) molecules that can be built given a number of building units (self-avoiding walks). References: [1] R.N. Grimes, Carboranes, 2nd Ed, Elsevier (2011). [2] J.M. Oliva, N.L. Allan, P.V.R. Schleyer, C. Viñas, F. Teixidor, "Strikingly long C···C distances in 1,2-disubstituted o-carboranes and their dianions", J. Am. Chem. Soc. 127 (2005) 13358. [3] M.G.S. Londesborough, D. Hnyk, J. Bould, L. Serrano-Andres, V. Sauri, J.M. Oliva, P. Kubat, T. Polívka, K. Lang, "Distinct photophysics of the isomers of B18H22 explained", Inorganic Chemistry 51 (2012) 1471. [4] J.M. Oliva, D.R. Alcoba, O.B. Oña, A. Torre, L. Laín, J. Michl, "Toward (car)borane-based molecular magnets", Theor. Chem. Acta (2015) 134:9. [5] L. Cerdán, J. Braborec, I. Garcia-Moreno, A. Costela, M.G.S. Londesborough, "A borane laser", Nature Commun. 6 (2015) 5958. [6] (a) M. Scholz, E. Hey-Hawkins, "Carbaboranes as pharmacophores: Properties, synthesis, and application strategies", Chem. Rev. (2011). (b) F. Issa, M. Kassiou, M. Rendina, "Boron in drug discovery: Carboranes as unique pharmacophores in biologically active compounds", Chem. Rev. (2011).