Magnesium-containing Zintl phase compounds Yb 14 MgSb 11 and Ca 14 MgSb 11 have been prepared by annealing the mixture of the elements at 1075−1275 K. These compounds are isostructural with the Zintl compound Ca 14 AlSb 11 and crystallize in the tetragonal space group I4 1 /acd (Z = 8). Singlecrystal X-ray data (90 K) were refined for Yb 14 MgSb 11 [a = 16.625(9) Å, c = 22.24(2) Å, V = 6145(8) Å 3 , and R1/wR2 (0.0194/0.0398)] and Ca 14 MgSb 11 [a = 16.693(2) Å, c = 22.577(5) Å, V = 6291(2) Å 3 , R1/wR2 (0.0394/0.0907)].This structure type has been shown to be highly versatile with a large number of phases with the general formula A 14 MPn 11 (A = Ca, Sr, Ba, Yb, Eu; M = Mn, Zn, Nb, Cd, Group 13 elements; Pn = Group 15 elements). The two compounds reported in this paper are the first Mg-containing analogs. Replacing M with Mg, which is divalent with no d-orbitals, probes electronic structure and properties of this structure type. Mg 2+ is well-known to prefer tetrahedral geometry and allows for integration of the properties of a main group analog isoelectronic to the transition metal (Mn 2+

Organic diradicals are uncommon species that have been intensely studied for their unique properties and potential applicability in a diverse range of innovative fields. While there is a growing class of stable and well characterized organic diradicals, there has been recent focus on how diradical character can be controlled or modulated with external stimuli. Here we demonstrate that a diiron complex bridged by the doubly oxidized ligand tetrathiafulvalene-2,3,6,7tetrathiolate (TTFtt 2−) undergoes a thermally induced Fe-centered spin-crossover which yields significant diradical character on TTFtt 2−. UV-vis-Near-IR, Mössbauer, NMR, and EPR spectroscopies with magnetometry, crystallography, and advanced theoretical treatments suggest that this diradical character arises from a shrinking TTFtt 2− π-manifold from the Fe(II)-centered spin-crossover. The TTFtt 2− centered diradical is predicted to have a singlet ground state by theory and variable temperature EPR. This unusual phenomenon demonstrates that inorganic spin transitions can be used to modulate organic diradical character. Results and Discussion Synthesis and Structural Parameters Complex 1 was synthesized via reaction with the deprotected proligand 2,3,6,7-tetrakis(2cyanoethylthio)tetrathiafulvalene (TTFtt(C2H4CN)4) in good yield. Complex 1 was insoluble in all solvents we investigated which precluded detailed characterization but is pure as indicated by combustion analysis and behaves as a suitable synthon for subsequent chemistry. Complex 1 can be doubly oxidized with [Cp2Fe][BAr F 4] to form 2 which is more soluble, enabling common solution characterization including 1 H NMR and cyclic voltammetry measurements (Figure S1-S2). Oxidation from 1 to 2 could be ligandcentered (TTFtt 4− →TTFtt 2−), metal-centered (2 Fe(II)→2 Fe(III)), or some intermediate case, but the data acquired for 2 supports a TTFtt 2− structure arising from ligandcentered oxidation (Chart 1B, see below). Compound 2 was structurally characterized via singlecrystal X-ray diffraction (SXRD) at 293 K (2-HT; Figure S3) and 100 K (2-LT; Figure 1). In both structures TTFtt 2− is bridged between two TPA-capped Fe centers with two outer-sphere BAr F 4 − counter anions. The most striking difference between these temperatures is markedly longer Fe bond lengths in 2-HT. The Fe-Npyridine and Fe-Namine bond lengths in 2-LT are 1.958(6)-1.979(6) and 2.017(6) Å (Figure 1), respectively. These values are consistent with Fe-N bonds in other low-spin complexes with a Fe-TPA moiety. 16,17 In 2-HT, these bonds are 0.18-0.19 and 0.244(11) Å longer than their counterparts at 100 K, respectively, and are consistent with high-spin Fe-TPA complexes. The shorter Fe bonds at lower temperature indicate that 2 exhibits a temperature dependent spincrossover as observed in related compounds. 16,21

Two coordination polymers of the type Co­(BPDC)­(N-ox), with BPDC being 4,4′-biphenyldicarboxylate and N-ox being pyridine N-oxide (PNO) or isoquinoline N-oxide (IQNO), have been synthesized and characterized. The compounds feature 2D and 3D metal–organic networks that encapsulate Co­(II)-based chains in a rigid superstructure. The dc and ac magnetic properties of these Co­(BPDC)­(N-ox) materials have been investigated alongside those of a related Co­(BDC)­(PNO) compound (where BDC is 1,4-benzenedicarboxylate), which contains a smaller dicarboxylate linker. These Co­(II)-containing coordination polymers exhibit slow magnetic relaxation, as observed by ac susceptibility measurements. The observed magnetic behavior of all compounds is consistent with an antiferromagnetic interaction between canted Co spins along the 1D skeleton, resulting in single-chain magnet behavior. In the case of Co­(BPDC)­(IQNO), weak interchain magnetic interactions yield 3D antiferromagnetic order while the inherent magnetic behavior stemming from the chain component is maintained. The combination of these effects in this material puts it at the frontier between single-chain magnets and classical bulk antiferromagnets. This work contributes to the limited group of materials featuring the organization of single-chain magnets within a coordination polymer superstructure.

The absence of a metal–metal multiple bond in a dimeric manganese hydride catalyst supported by β-diketiminate ligands, [(2,6-iPr2PhBDI) Mn(μ-H)]2, was investigated with density functional theory in conjunction with experimental evidence.