Assembly of a family of 12 supramolecular compounds containing [AnOCl] (An = U, Np, Pu), via hydrogen and halogen bonds donated by substituted 4-X-pyridinium cations (X = H, Cl, Br, I), is reported. These materials were prepared from a room-temperature synthesis wherein crystallization of unhydrolyzed and valence-pure [An(VI)OCl] (An = U, Np, Pu) tectons is the norm. We present a hierarchy of assembly criteria based on crystallographic observations and subsequently quantify the strengths of the non-covalent interactions using Kohn-Sham density functional calculations. We provide, for the first time, a detailed description of the electrostatic potentials of the actinyl tetrahalide dianions and reconcile crystallographically observed structural motifs and non-covalent interaction acceptor-donor pairings. Our findings indicate that the average electrostatic potential across the halogen ligands (the acceptors) changes by only ∼2 kJ mol across the AnO series, indicating that the magnitude of the potential is independent of the metal center. The role of the cation is therefore critical in directing structural motifs and dictating the resulting hydrogen and halogen bond strengths, the former being stronger due to the positive charge centralized on the pyridyl nitrogen, N-H. Subsequent analyses using the quantum theory of atoms in molecules and natural bond orbital approaches support this conclusion and highlight the structure-directing role of the cations. Whereas one can infer that Columbic attraction is the driver for assembly, the contribution of the non-covalent interaction is to direct the molecular-level arrangement (or disposition) of the tectons.
The excitation function for production of 262 Bh in the odd-Z-projectile reaction 208 Pb( 55 Mn, n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from 262 Bh and 2 decay chains originating from 261 Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540 +180 −150 pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than five times larger than that expected based on previously reported results for production of 262 Bh in the analogous even-Z-projectile reaction 209 Bi( 54 Cr, n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the optimum energy rule proposed byŚwia˛tecki, Siwek-Wilczyńska, and Wilczyński.
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