Here we report that attempted preparation of low-valent CaI complexes in the form of LCa-CaL (where L is a bulky β-diketiminate ligand) under dinitrogen (N2) atmosphere led to isolation of LCa(N2)CaL, which was characterized crystallographically. The N22ˉ anion in this complex reacted in most cases as a very potent two-electron donor. Therefore, LCa(N2)CaL acts as a synthon for the low-valent CaI complex LCa-CaL, which was the target of our studies. The N22ˉ anion could also be protonated to diazene (N2H2) that disproportionated to hydrazine and N2. The role of Ca d orbitals for N2 activation is discussed.

Surface critical behavior (SCB) refers to the singularities of physical quantities on the surface at the bulk phase transition. It is closely related to and even richer than the bulk critical behavior. In this work, we show that three types of SCB universality are realized in the dimerized Heisenberg models at the (2+1)-dimensional O(3) quantum critical points by engineering the surface configurations. The ordinary transition happens if the surface is gapped in the bulk disordered phase, while the gapless surface state generally leads to the multicritical special transition, even though the latter is precluded in classical phase transitions because the surface is in the lower critical dimension. An extraordinary transition is induced by the ferrimagnetic order on the surface of the staggered Heisenberg model, in which the surface critical exponents violate the results of the scaling theory and thus seriously challenge our current understanding of extraordinary transitions.

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The cationic complex BeOCO+ is produced in a solid neon matrix. Infrared absorption spectroscopic study shows that it has a very high antisymmetric OCO stretching vibration of 2418.9 cm–1, which is about 71 cm–1 blue-shifted from that of free CO2. The quantum chemical calculations are in very good agreement with the experimental observation. Depending on the theoretical method, a linear or quasi-linear structure is predicted for the cation. The analysis of the electronic structure shows that the bonding of Be+ to one oxygen atom induces very little charge migration between the two moieties, but it causes a significant change in the σ-charge distribution that strengthens the terminal C–O bond, leading to the observed blue shift. The bonding analysis reveals that the Be+ ← OCO donation results in strong binding due to the interference of the wave function and a charge polarization within the CO2 fragment and hybridization to Be+ but only negligible charge donation.