Experimental and theoretical investigations on magneto-structural correlation in trinuclear copper(II) hydroxido propellers

Selective Formation, Reactivity, Redox and Magnetic Properties of MnIII and FeIII Dinuclear Complexes with Shortened Salen-Type Schiff Base Ligands

“…Taking into account the suggested magneto-structural relationship [ 23 ], the Fe–O–Fe angle should be close to 101° for 4b and around 103° for 6a and 6e , even if this remains just a speculation in the absence of their crystal structures. Regardless, the small difference between 6a (X = t Bu) and 6e (X = Cl) is most probably not related to the substituent X, which is far and in an unfavorable position for inducing any electronic effect on the coupling constant, differently from what we observed in trinuclear copper(II) hydroxido propellers with electronically-modulated tridentate Schiff base ligands [ 43 ].…”

When the Metal Makes the Difference: Template Syntheses of Tridentate and Tetradentate Salen-Type Schiff Base Ligands and Related Complexes

“…The high-dilution template method under the same reaction conditions of boiling methanol affords trinuclear species of general formula [Cu 3 (µ 3 -OH)( G L) 3 ](ClO 4 ) 2 when operating in a basic medium, Equation ( 3) [39,66,[76][77][78][79][80]. Of sure interest is the combined effect of the electronic features of the substituent on the G-salH on the reaction product: the electron donor methoxy group (G = 5-OMe) leads invariably to the dinuclear species even in excess of NaOH as source of the bridging OH group, while the electron withdrawing nitro group (G = 5-NO 2 ) yields only to the trinuclear compounds also in defect of base [39].…”

“…Of sure interest is the combined effect of the electronic features of the substituent on the G-salH on the reaction product: the electron donor methoxy group (G = 5-OMe) leads invariably to the dinuclear species even in excess of NaOH as source of the bridging OH group, while the electron withdrawing nitro group (G = 5-NO 2 ) yields only to the trinuclear compounds also in defect of base [39]. Furthermore, the electronic effect exerted by the substituent G in position 5 (Me, H, Br, NO 2 ) is able to efficiently modulate the Cu•••Cu magnetic super-exchange in these spin-frustrated systems [76]. Alternatively, in the presence of a stronger coordinating anion compared to ClO 4 -, such as Cl -, N 3 -, NCO -, NCS -, etc., the dinuclear species [Cu 2 (µ-X) 2 ( G L) 2 ] are obtained and stabilized in the solid state.…”

“…3 G-salNa + 3 Cu(ClO 4 ) 2 + 3 diamine + NaOH → [Cu 3 (µ 3 -OH)( G L) 3 ](ClO 4 ) 2 + 4 NaClO 4 + 3 H 2 O (diamine = en, tn) (3)A triply-bridging hydroxido ligand occupies the fourth coordination site of each of the three copper(II) ions with a bond distance slightly varying around 2.00 Å and giving rise to a global propeller-like structure formed by the three [Cu( G L)] + blades. Additional elongated Cu•••O apical positions (2.30-2.50 Å) are occupied by the oxygen atom of the adjacent blade, thus increasing the coordination toward square pyramidal and with a partial cubane Cu 3 O 4 core (Figure3b)[76]. Further additional apical interactions of the copper(II) ions with perchlorate anions and/or solvent molecules are also active in practically all the known derivatives[39,76,78,80].The addition of a base (excess of Et 3 N or stoichiometric NaOH) to a suspension of the mononuclear [Cu( G L)(L')](ClO 4 ) or dinuclear [Cu 2 (µ-G L) 2 ](ClO 4 ) 2 derivatives in methanol leads to their conversion into the trinuclear species [Cu 3 (µ 3 -OH)( G L) 3 ](ClO 4 ) 2 as a result of the increasing concentration of OH − ions into the basic medium[39,64,66,78].…”

Homoleptic CoII, NiII, CuII, and ZnII Complexes Based on 8‐Hydroxylquinoline Schiff Base Derivative: a Combined Synthetic, Spectral, Structural, and Magnetic Study

“…They are generally prepared in high yields by condensation of any primary diamine with two equivalents of salicylaldehyde derivatives , . Mono‐condensed Schiff bases have also been obtained either by direct,, or metal template,, reactions between carbonyl units and appropriate amino alcohol, diamine or aminothiol substrates, yielding a large variety of tridentate ligands featuring ONX‐donor sets (X = O, N, and S) , . Metal complexes prepared with these ligands show diverse structure features, topology, nuclearity as well as supramolecular architectures, depending on the experimental conditions (metal‐to‐ligand ratios, supporting anions, solvents, etc) , , .…”