The single‐molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(η5‐C5R5)2]+ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(η5‐C5Me5)2]BArF are revealed. Multireference quantum mechanical calculations show a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach‐like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible for the SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(η5‐C5Bn5)2]BF4 and [Fe(η5‐C5Bn5)2]PF6, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems.

Four new quasi-1D Ni-lantern chain complexes of the form [Ni(SOCR)(L)] (R = Ph, L = DABCO (1); R = Ph, L = pyz (2); R = CH, L = DABCO (3); R = CH, L = pyz (4)) were prepared from the reaction of [Ni(SOCR)(EtOH)], R = CH or Ph, with the N,N'-donor bridging ligands pyrazine (pyz) or 1,4-diazabicyclo[2.2.2]octane (DABCO). Reaction of [Ni(tba)(EtOH)], (tba = thiobenzoate) with the mono-N donor ligand quinuclidine (quin) gave the discrete Ni-lantern complex [Ni(tba)(quin)] (5), whereas reaction with pyridine led to fragmentation of the lantern and formation of the known [Ni(tba)(py)] (6). Single-crystal X-ray diffraction reveals 2-4 to be 1D chain complexes comprising DABCO or pyz ligands which bridge the Ni-lantern units. Complex 5 forms dimers through two equivalent NiS interactions. The Ni-Ni distances within the Ni-lanterns are 2.5316(18)-2.595(2) Å for the 1D chain complexes 2-4, and 2.5746(4) Å in the dimeric complex 5, respectively. Comparing the solid state magnetism of 5 to precursor [Ni(tba)(EtOH)] demonstrates a change in coupling upon change of capping ligand. Meanwhile, chains 1-4 exhibit magnetic properties consistent with an S = 1 system, due to a mixed valent system where the two Ni centers differ in spin state, while 5 possesses two S = 1 Ni(ii) centers. DFT calculations confirm low-spin S = 0 {NiS} and high-spin S = 1 {NiO} centers in each lantern. Fits to the magnetic susceptibility data of the chains suggest a weak antiferromagnetic mean field interaction is present that is largely 1-D in nature, though neither pyrazine nor DABCO promote significant magnetic interaction between neighboring Ni-lanterns.

We present the syntheses and characterization of several salts of a trigonal prismatic cobalt(ii) complex with a 1,3,5-triaminocyclohexane (tach)-derived ditopic ligand. The air- and moisture-stable tetraphenylborate salt (2) shows slow magnetic relaxation under both zero and applied dc fields. This complex also exhibits an unexpected ability to interact with a cationic sodium guest ion, highlighting the ambifunctional binding nature of amide groups within an iminopyridine scaffold.

The synthesis and structure-activity relationships of a homologous series of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid gadolinium(III) complexes bearing thiol-terminated alkyl sidechains from three to nine carbons in length are reported. The observed binding with human serum albumin (HSA) of the compounds having C-3 through C-7 sidechain lengths was inhibited by homocysteine in a manner consistent with single-site binding. The observed binding with HSA of the compounds having C-8 and C-9 sidechain lengths was only partly inhibited by homocysteine, consistent with multi-site binding. The binding affinity of the C-7 compound could be related to the HSA oxidation state. 2D 1H–1H NMR TOCSY provided evidence of covalent binding of the europium analog of the C-6 compound to HSA-Cys34. The longitudinal water-proton MRI relaxivities of the gadolinium complexes at 7 Tesla increased upon binding to HSA. Based on these results, the C-6 and C-7 compounds were identified as promising redox-sensitive MRI contrast agents.

Formal syntheses of tetracyclic terpenoids frondosin B and liphagal are described. Both synthetic routes rely on the use of platinum-catalyzed α,β-unsaturated carbene formation for the key C–C bond forming transformations. The successful route toward frondosin B utilizes a formal (4 + 3) cycloaddition, while the liphagal synthesis features the vinylogous addition of an enol nucleophile as a key step. Both synthetic routes are discussed, revealing insights into structural requirements in the catalytic α,β-unsaturated carbene reaction manifold.