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The new polynucleating tripodal proligand $\text{H}_6\text{tren(dpa)}_3$, containing thirteen nitrogen donors of four different types, was designed, synthesized, and isolated in good yield (${\sim }$60%) via a transition-metal-free triple N-arylation of $\text{H}_6$tren with HXdpa (X $=$ Br or F), using $\text{K}_2\text{CO}_3$ or $\text{Cs}_2\text{CO}_3$ as a base ($\text{H}_6$tren $=$ tris(2-aminoethyl)amine, HXdpa $=$ 6-halogeno-$N$-(pyridin-2-yl)pyridin-2-amine). HFdpa was prepared with excellent yield (90–92%) by reaction of 2,6-difluoropyridine with 2-aminopyridine in LiH/toluene/pyridine and was found more reactive than HBrdpa, affording higher conversion and higher yield. Use of $\text{Cs}_2\text{CO}_3$ turned out to be essential for achieving high regioselectivity and eliminating overarylation almost completely.

Two new paramagnetic supramolecular helicates with the formula (X@[Ni2L3])3+ (X = Cl, or Br; L = a bis-pyrazolylpyridine ligand) have been prepared and are described. Helicates of this metal are very rare with virtually no prior examples of them acting as hosts of anionic species. The persistence of the new assemblies in solution has been demonstrated unambiguously by mass spectrometry and paramagnetic 1H NMR. This has allowed us to establish the preference of the coordination [Ni2] host for Cl− over Br−, in agreement with DFT calculations. These results show the promise of the use of metallohelicates as suitable systems for the selective encapsulation of specific anions in solution. [ABSTRACT FROM AUTHOR]

We provide definitive experimental proof that the archetypal string-like compound [Cr5(tpda)4(NCS)2] has alternating long and short Cr–Cr separations in the solid state, as conjectured by F. A. Cotton, rather than essentially equally spaced Cr atoms, as initially claimed (H2tpda = N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine). Single-crystal X-ray data collected from 292 to 3 K revealed that the misinterpretation is caused by pseudo-merohedral twinning and that bond length alternation is enhanced at low temperature. [ABSTRACT FROM AUTHOR]

Tetragallium(III) complex in [Ga4(L4‐Py)2(dpm)6] ⋅ EtOH, with H3L4‐Py=2‐(hydroxymethyl)‐2‐(pyridin‐4‐yl)propane‐1,3‐diol and Hdpm=dipivaloylmethane, was investigated as a diamagnetic analogue of tetrametallic, propeller‐like single‐molecule magnets (SMMs). The chiral molecular structure partitions the six CH2 protons of each tripodal (L4‐Py)3− ligand into two diastereotopic sets. The two signals were clearly detected by 1H NMR spectroscopy in C6D6, proving that Λ and Δ enantiomers interconvert slowly over NMR timescale. Density functional theory calculations provided quantitative agreement with the observed values of chemical shifts and scalar coupling constants across both geminal and long‐range interaction pathways. The solid‐state structure suggests the occurrence of a lower symmetry stereoisomer (27 mol%), which was clearly identified in the NMR spectra. Since high spin Fe3+ forms distinctly more inert complexes than Ga3+, comparable or greater configurational stability is expected for the isostructural FeIII4, FeIII3CrIII, and FeIII3VIII SMMs, which are difficult to investigate by solution NMR because of the strong paramagnetism. [ABSTRACT FROM AUTHOR]

The synthesis of potassium- and lithium-containing cyclic clusters has been carried out to study the influence of the alkali metal ion on the properties of the core of the clusters. Synthesizing the potassium clusters turned out to be a failure but lithium clusters were successfully derived. Results show that the metal ion in complexes 1 to 3 tunes the magnetism of the core. Its j value is related to the ionic radius of the guest ion which also determines the exact pattern at the bridging methoxide ligands.

The structure and magnetic properties of a mixed-valence heptanuclear manganese cluster, (Mn7(OMe)12(dbm)6)*CHCl3*14MeOH are examined. The structure and solid-state magnetic behavior of the dimeric complex (Mn(super III)(sub 2)(OMe)2(dbm)4) was also investigated. Proton NMR spectra in solution strongly support valence localization and indicate that the observed solid-state structure may be caused by static disorder effects.

A study was conducted to determine the spectroscopic characterization of a Schiff base diquinone ligand that formed two valence tautomeric species with cobalt ions having a transition temperature within room temperature. The Schiff base biquinone ligands were either denoted as Cat-N-BQ or Cat-N-SQ. The CoIII(Cat-N-BQ)(Cat-N-SQ) was the cobalt complex formulated and characterized. Results indicated that the cobalt complex manifested a valence tautomeric equilibrium in solution. The valence tautomerism distinguished a complex formed by a ligand containing a nitrogen donor atom.

The reaction of (N(CH3)sub4)OH with FeCl3 and thme in a methanolic medium gives (N(CH3)4)2(OFe6(H-3thme)3(OCH3)3Cl6).2Hsub2O, where thme = 1,1,1-tris(hydroxymethyl)ethane. The structure has three methoxo bridges, which link two Fe(III) units to six terminally coordinating Cl- ligands. Variable temperature magnetic susceptibility values show antiferromagnetic coupling for the hexanuclear complex core in a singlet ground state. The Fe-mu6-O-Fe interactions are unusually large, which are explained using molecular orbital calculations at the extended Huckel level.

Polymetallorganosiloxanolates form a class of nanoscale metal ion clusters. Two Cu complexes, Na4((PhSiO2)sub12Cu4).8nBuOH and K4((C2H3SiO2)sub12Cu4).6nBuOH have Cu-atoms present as Cu2O6 units and show a large antiferromagnetic exchange coupling. Whereas ((PhSiO2)sub6Cu6(O2SiPh)6).6EtOH has a sandwiched structure present in S = 3 ground state. Magnetic susceptibility and high frequency electron paramagnetic resonance are employed to study magnetic anisotropy in spin clusters.