Binding Motifs of Doubly- and Singly-charged Proton-bound Clusters of B12F122– and Diaminoalkanes

The complexation of perfluorinated dodecaborate, B12F122–, with protonated diaminoalkanes, [H2N(CH2)nH2N] (n = 2 – 12), are studied with a combination of infrared multiple photon dissociation (IRMPD) action spectroscopy and ion mobility spectrometry. Singly-charged clusters of the form [B12F12 + H2N(CH2)nH2N + H]– (n = 2 – 12) and doubly-charged clusters of the form [2B12F12 + H2N(CH2)nH2N + 2H]2– (n = 2 – 12) are observed and characterized experimentally and computationally. For the singly-charged clusters, low-energy structural motifs associated with monodentate and bidentate binding of the diaminoalkane are computed, as well as a conformation involving intramolecular hydrogen bonding between the amino moieties. For the doubly-charged clusters, the doubly-protonated diaminoalkane acts as a tether between two B12F122– cages. Major product channels of the singly-charged and the doubly-charged species are found to be the formation of HB12F122– via proton transfer and the loss of B12F122–. The fragmentation of HB12F12–leads to several secondary products, including [B12F11 + N2]–. Collision cross sections (CCSs) for the singly-charged clusters are reported and the major subpopulation of the gas-phase ensemble for the different singly-charged species is the bidentate conformation.