Aluminum carbide cluster anions Al n C 2 − (n = 5−13) were observed as the most dominant products in the gas-phase reactions of laser-ablated Al n − with organic molecules, such as methanol, ethanol, pentane, acetonitrile, or acetone. Density functional theory calculations predicted two possible isomeric structures for Al n C 2 − : isomers in which two carbons are dissociated (type D) as in the case of the bulk aluminum carbide and novel isomers in which two carbons form an acetylide-like C 2 unit. The latter isomers are further categorized into three types depending on the location of the C 2 unit: the C 2 unit is encapsulated within the Al cage (type I), contained in the surface of Al clusters (type S), or attached to the surface of Al clusters (type O). Size-dependent behavior of the adiabatic electron affinities of Al n C 2 determined by photoelectron spectroscopy was explained in terms of polymorphism as a function of size (n): type I for n = 5−8, type D for n = 9−11, type D or O for n = 12, and type O for n = 13. The tendency in which the position of the C 2 unit was shifted from the inside to outside with the increase in n was ascribed to the balance between the stabilizations gained by forming Al−C bonds and Al−Al bonds. The smaller Al n C 2 − clusters (n = 5−8) prefer to surround the acetylide-like C 2 unit with the Al atoms so as to maximize the number of Al−C bonds, whereas larger ones (n = 12 and 13) prefer to attach the C 2 unit onto the surface of the Al clusters so as to maximize the number of Al−Al bonds.
A soluble polymer of cyclic structure has been obtained by radical polymerization of diallyleyanamide. A kinetic analysis of the polymerization indicated that the overall rate of the system is first‐order with respect to concentration of initiator and either first‐ or second‐order with respect to monomer concentration, depending on the solvent used. The molecular weight of the polymer is independent of the concentration of the initiator and the monomer. The intramolecular abstraction of hydrogen is proposed as a termination reaction.
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A series
of Au
x
Si4
– cluster anions (x = 1–4) were generated
most abundantly by laser ablation of a Au4Si alloy target.
Photoelectron spectroscopy and density functional theory (DFT) calculation
of Au
x
Si4
– (x = 1–4) revealed that Au3Si4
– can be viewed as an electronically closed
superatom and is composed of a Si4 unit whose three adjacent
edges of a single facet are bridged by three Au atoms. Such phase-segregated
structure is facilitated by aurophilic interaction between the three
Au atoms and results in a large permanent dipole moment (4.43 D).
DFT calculations on an electronically equivalent superatom Au4Si4 predicted a new structure in which the uncoordinated
Si atom of Au3Si4
– is bonded
by Au+. This Au4Si4 is much more
stable than a cubic structure previously reported and has a large
HOMO–LUMO gap (1.68 eV) and a small permanent dipole moment
(0.41 D).
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