Carboxylic acid-tuned nickel(ii) clusters: syntheses, structures, solution behaviours and magnetic properties

Three novel cicada-like nickel(ii) clusters, formulated as [Ni₆(bdped)₂(mba)₆(Hdmpz)₂(NO₃)₂(H₂O)₂]·4MeCN (SD/Ni6b), [Ni₅(bdped)₂(tca)₆(Hdmpz)(MeOH)₂(H₂O)]·MeOH (SD/Ni5a) and [Ni₄(Hbdped)₂(ba)₄(Hdmpz)₂]·2NO₃·2MeCN (SD/Ni4a), were obtained by tuning the auxiliary carboxylic acids, where H₂bdped = 1,2-bis-(3,5-dimethylpyrazol-1-yl)-ethane-1,2-diol; Hmba = 2-methylbenzoic acid; Hdmpz = 3,5-dimethyl-1H-pyrazole; Htca = 3-thiophenecarboxylic acid; and Hba = benzoic acid. The structures of SD/Ni6b, SD/Ni5a and SD/Ni4a are built from a central Ni₄O₄ opened cube, appending two to zero NiNO₅ octahedra. The solution behaviours of SD/Ni6b, SD/Ni5a and SD/Ni4a were studied in detail via an ESI-MS technique and their solution stabilities were confirmed. Magnetic analysis indicated the presence of Ising-type anisotropy: D = -13, -10, and -11 cm^-1 for SD/Ni6b, SD/Ni5a, and SD/Ni4a, respectively; moreover, dominantly ferromagnetic interactions were found between magnetic centers: J₁ = 6.5 cm^-1, J₂ = -0.44 cm^-1 and J₁ = 5.9 cm^-1, J₂ = 2.6 cm^-1 for SD/Ni5a and SD/Ni4a, respectively. Besides, the photocurrent signals were observed and they reached the maximum very quickly for these three nickel(ii) clusters and then their current intensities remained almost constant, which provide a possibility to be used for light-harvesting and photo-related catalysis.

A rod-like hexanuclear nickel cluster based on a bi(pyrazole-alcohol) ligand: structure, electrospray ionization mass spectrometry, magnetism and photocurrent response

An unusual one-dimensional zig-zag hexanuclear Ni(ii) cluster has been easily and successfully constructed using a designed multidentate pyrazole-alcohol ligand.

A high-nuclearity complex containing a decanuclear iron(iii)/oxo cage in a football-like structure and rare (R-/S)-hemiacetalate ligands in a butterfly-like format

A challenge in the field of high nuclearity Fe(iii)/oxo cluster chemistry remains the development of new synthetic methods to such molecules. In this work, the employment of pyridine-2-carboxaldehyde (py-2-al) in high-nuclearity transition-metal cluster chemistry has provided access to an unprecedented decanuclear iron(iii) complex, [Fe₁₀(NO₃)₇(O)₆(OH_0.5)₂((S)-py-hemi)₄((R)-py-hemi)₄]·4H₂O (1) ((R-/S)-py-hemi = (R-/S)-pyridine-2-carboxaldehyde hemiacetalate). The synthesis, beautiful structure and the physical characterization (thermal gravimetric analysis, X-ray powder diffraction, proton nuclear magnetic resonance, magnetic susceptibility) of complex 1 are described in this contribution. Complex 1 provides a new route to obtain high nuclearity magnetic clusters with beautiful structures.

The employment of pyridine-2-carboxaldehyde in high-nuclearity cluster chemistry has provided access to a decanuclear iron(iii)/oxo cage in football-like structure and unusual (R-/S)-hemiacetalate ligands in butterfly-like format.