Transforming carbon dioxide into a methanol surrogate using modular transition metal-free Zintl ions.

Although not the only greenhouse gas, CO is the poster child. Unsurprisingly, therefore, there is global interest across industrial and academic research in its removal and subsequent valorisation, including to methanol and its surrogates. Although difficult to study, the heterogenous pnictogens represent one important category of catalytic materials for these conversions; their high crustal abundance and low cost offers advantages in terms of sustainability.

Pyrazolate-supported Cr(μ-O) cores; homovalent CrIII3 and mixed-valent CrIII2Cr.

The thermally assisted reaction of Cr(NO)·9HO, 4-Cl-pzH, and EtN yielded electrochemically active trinuclear Cr-oxo-pyrazolate complexes with formula (PhP)[Cr(μ-O)(μ-4-Cl-pz)X], X = Cl (1) and Br (2). Magnetic susceptibility measurements and EPR spectroscopy show that 1 has an antiferromagnetically coupled CrO-core with an = 1/2 ground state and isotropic exchange of = -12.7 cm.

Pathways of cluster growth: infra-red multi-photon dissociation spectroscopy of a series of Re-Si clusters, [ReSi], = 3-9.

Infra-red multiple-photon dissociation spectroscopy on Xe-tagged Re/Si clusters, [ReSi], = 3-9, reveals intense absorption features around 400 cm, along with, in some cases, additional bands in the 250-350 cm window. A survey of the potential energy surface using density functional theory in conjunction with particle swarm optimisation indicates a growth pattern based on a growing network of Si atoms wrapped around the Re centre: the Si units can be viewed as fragments of a putative 16-vertex Frank-Kasper polyhedron. The structural evolution for the [ReSi] series differs significantly from the iso-electronic Mn series studied previously, where the metal ion is typically bound externally to the surface of a growing 3-dimensional Si cluster, the differences reflecting the greater accessibility of 5d 3d electron density.

Fe-Fe bonding in the rhombic Fe cores of the Zintl clusters [FeE] (E = Sn and Pb).

We report here the synthesis and characterization of two endohedral Zintl-ion clusters, [FeSn] and [FePb], which contain rhombic Fe cores. The Fe-Fe bond lengths are all below 2.5 Å, distinctly shorter than in the corresponding Cu clusters, indicating the presence of Fe-Fe bonding.

Thermodynamics of phase transitions in Zintl clusters from density functional theory: making and breaking of bonds in BaGe.

Density functional theory, in conjunction with the quasi-harmonic approximation, has been used to study the equilibrium between the orthorhombic and tetragonal phases of BaGe. A transition from the high-temperature tetragonal phase containing isolated Ge units to the low-temperature orthorhombic phase, where precisely half of the Ge units are polymerised along one axis, is predicted at 930 K, somewhat higher than the experimental value of 630 K. An analysis of the phonon density of states shows that the lower entropy of the orthorhombic phase is not associated directly with the polymerisation of the Ge units, but rather with the contraction of the unit cell, which raises the frequencies of ion-ion modes involving the relative motions of the Ba and Ge units.