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Two dinuclear double oxygen-bridged iron(III) complexes made of the Fe2(μ2-OR)2 diamond-core cluster resulting from the coordination between iron(III) cations with calix[4]arene ligands and bearing two lower-rim-appended salicylideneamine (4) or o-methoxy-salicylideneamine coordinating sites (5), connected to the macrocyclic platform via three methylene bridges and displaying a salen-type coordination pocket, were synthesized and characterized using single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), high-resolution mass spectrometry (HRESI-MS), IR, TG-DSC and EA techniques. Independent of the presence of the o-methoxy group in the salicylideneamine moieties, the as-formed complexes contained two nonequivalent iron(III) atoms, both adopting a distorted octahedral coordination N2O4-environment but differing in the cis and trans positions of the nitrogen atoms within the metal coordination sphere, as attested by single-crystal X-ray diffraction and DFT-B3LYP calculations. The possible reason for the observed coordination mode of the macrocyclic ligands is their conformational behavior upon coordination with Fe(III) cations, as confirmed by DFT-B3LYP analysis. 57Fe Mössbauer spectroscopy study showed that both Fe(III) atoms were present in high spin states at room temperature and at 80 K in the studied coordination compounds. The methoxy groups located at the ortho position of the salicylideneamine coordinating fragments were observed to influence the energy of the frontier orbitals, resulting in an increase in the bandgap energy from 1.97 eV to 2.07 eV, as experimentally established by solid-state voltammetry study of 42-Fe2 exp and 52-Fe2 exp, respectively. The interplay between the steric and electronic factors, emerging from the o-methoxy group within coordinating salicylideneamine moieties, seemed to have a negligible effect on the electronic properties of the prepared clusters but significantly impacted the frontier orbital energy distribution, according to both experimental data and theoretical calculations. [ABSTRACT FROM AUTHOR]

A series of new manganese complexes of general formula 32-Mn4Xn , displaying a highly-reproducible [Mn II2 Mn III2 ] cluster core formation, was observed when tetra-p-adamantylcalix[4]arene 3 was used in combination with N,N′-chelating auxiliary ligands, such as bipy (32-Mn4(bipy)2, bipy = 2,2′-bipyridyl) and phen (32-Mn4(phen)2, phen = 1,10-phenanthroline), as well as with DMF/H2O solvent molecules (32-Mn4(dmf)4, 32-Mn4(dmf)2(H2O)2), acting as O-donor coligands, in the crystalline phase. Single-crystal X-ray diffraction revealed that the involvement of auxiliary ligands in coordination with Mn-ions results in the distortion of their coordination sphere and leads to the controlled compression of the {Mn4}-cluster core of complexes. Moreover, the appearance of adamantyl groups at the upper rim of the macrocyclic backbone of 3 influences the crystalline self-assembly of obtained clusters, providing a preferable "side-to-head" orientation of the cluster molecules within the crystal, leading to the observation of relatively higher {Mn4}⋯{Mn4} distances than those revealed for the earlier reported calix[4]arene supported {Mn4} clusters. All 32-Mn4Xn clusters demonstrated ferromagnetic interactions between the metal atoms within the cluster core independent of the nature of the O-donor or N-donor auxiliary ligands. [ABSTRACT FROM AUTHOR]