Arulmozhiraja, SundaramCoote, MichelleLu, DiSalem, GeoffreyWild, Stanley (Bruce)2015-12-101089-5639http://hdl.handle.net/1885/58676This paper presents a combined experimental and theoretical study of the electronic spectrum of the natural adamantane-type polyarsenical Arsenicin A. Experiments reveal that this molecule strongly absorbs UV light in the absence of an obvious chromophore. The observed absorbance is supported by the time-dependent density functional (TD-DFT) calculations with B3LYP, M06-L, and M06-2X functionals combined with the 6-311+G(3df,2pd) basis set, as well as by symmetry-adapted cluster/configuration interaction (SAC-CI) theory. The theoretical investigations reveal that the absorption is facilitated by through-space and through-bond interactions, between the lone pairs on the arsenic and oxygen atoms and the α-bonding framework of the molecule, that destabilize occupied and stabilize unoccupied molecular orbitals.Keywords: Absorbances; Adamantanes; Basis sets; Electronic spectrum; Functionals; Lone pair; Oxygen atom; Theoretical investigations; Theoretical study; Through-bond interactions; Time-dependent density; Ultraviolet absorption; UV light; Absorption; Arsenic; Chemic201110.1021/jp200956b2016-02-24