Bonding of Atomic Phosphorus to Polycyclic Hydrocarbons and Curved Graphitic Surfaces Santiago Melchor, † Jose A. Dobado, † J. Andreas Larsson,* ,‡ and James C. Greer ‡ Contribution from Grupo de Modelizacio ´ n y Disen ˜ o Molecular, Departamento Quı ´mica Orga ´ nica, Campus FuentenueVa, UniVersidad de Granada, 18071 Granada, Spain, and NMRC, UniVersity College, Lee Maltings, Prospect Row, Cork, Ireland Received July 1, 2002 ; E-mail: alarsson@nmrc.ucc.ie Abstract: We present a theoretical study of the bonding of atomic phosphorus to planar hydrocarbons and to curved graphite-like surfaces. We find that bonding of phosphorus to planar polycyclic hydrocarbons induces curvature away from the phosphorus atom, as defined by the pyramidalization angle. Similarly, bonding of atomic phosphorus to the [5,5] fulvalene-circulene semifullerene and buckminsterfullerene is only possible on the convex side of the carbon surface. On the other hand, we find the interaction of atomic phosphorus with the concave side of fullerene-like surfaces to be nonbonding for both quartet and doublet spin states. We find the prerequisite for stable epoxy-type bonds within these systems is the ability of the carbon atoms to maintain or induce curvature away from the P‚‚‚CdC bond. I. Introduction The interaction between phosphorus and carbon based materi- als is of interest for many fields of chemistry as varied as organic synthesis, doping of carbon systems, and fullerene chemistry. The bonding of atomic phosphorus to double bonds, conjugated double bonds, and aromatic bonds has not been fully explored. This is true in particular for the newer forms of carbon: the fullerenes and nanotubes. Our study examines the bonding of phosphorus to buckminsterfullerene (1), the [5,5] fulvalene- circulene semifullerene (2), 1-5 pyracyclene (3), pyrene (4), and ethene (5). The molecules considered vary in their geometric and electronic structures. We find, however, that there are generic effects associated with phosphorus bonding to these molecules in terms of bond energies, magnitude of charge transfer, electronic densities, and pyramidalization angles. Our choice of molecules allows us to reasonably extrapolate the behavior we observe to a broader set of organic and fullerene systems. We will relate our findings to recent studies of the nonbonding interaction of nitrogen and phosphorus with the inside of fullerene cages. 6-18 Many endohedral dopant atoms from the first and second rows of the periodic table, and for metallic dopants studied, reveal that endohedral dopant atoms bond to the inside wall of the fullerene, with the exception of the noble gas atoms and, as recently observed, nitrogen and phosphorus. The latter two dopant atoms, like the rare gases, occupy a central position in the fullerene cage. Experimental and theoretical findings confirm that the properties of endohedral group V atoms are only slightly perturbed by the surrounding C 60 cage; 6-8,14-15 the dopant atom and host’s chemical and electronic properties are largely undisturbed. There are recent semiempirical studies indicating bonding interactions for endohedral phosphorus doping of buckminsterfullerene; 19-21 however, these calculations are in conflict with experimental studies 6-13 and ab initio calculations. 14-16 Recently it has been shown that the internal curvature of C 60 inhibits covalent bonding of fluorine, and that the F atom prefers to bond to the exterior of (5,5) single wall nanotubes. 22 * To whom correspondence should be addressed. Phone: +353 (0)21 490 4166. Fax: +353 (0)21 427 0271. † Universidad Granada. ‡ NMRC, University College Cork. (1) Abdouzarak, A. H.; Marcinow, Z.; Sygula, A.; Sygula, R.; Rabideau, P. W. J. Am. Chem. Soc. 1995, 117, 6410. (2) Rabideau, P. W.; Abdouzarak, A. 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