The synthesis, characterization and properties of two unprecedented undecanuclear heterobimetallic Zn4Ln7 complexes of formula [Zn4Ln7(L)8(O2)2(OH)4(Cl)4(H2O)4]·Cl·4H2O·4CH3CN (Ln = Gd (1), Dy (2)) encapsulating two peroxide anions are presented, representing a very rare example of a 3d-peroxo-Ln system and expanding the realm of metal-peroxo complexes. These eleven metal ions are arranged in a peculiar structural motif, where Zn4 is located at the peripheral shell wrapping Ln7 in the inner core. The Zn ions are penta-coordinate in all cases, linked to the NO2 donor atoms from the L2− ligand and to a hydroxyl group, and the apical position is occupied by a chloride anion. All LnIII ions in these systems are octa-coordinate with LnO8 and LnNO7 coordination spheres. Magnetocaloric effect (MCE) behavior has been found in the Gd analogue due to multiple low lying excited states arising from antiferromagnetic Gd–Gd exchange interactions. The Dy derivative shows frequency dependent out-of-phase signals indicating the presence of slow relaxation of magnetization below 8 K under zero applied direct current (dc) field, but without reaching a maximum, which is due to a faster quantum tunneling relaxation. The effective barrier extracted from the frequency dependent data is Ueff = 11.2 K and a τ0 of 4.18 × 10−6 s.

The initial employment of 2-(2-hydroxy-3-methoxybenzylideneamino)phenol (H2L) in Mn–Ln chemistry yields four isostructural MnIII2LnIII2 clusters [MnIII2LnIII2(O)L4(CH3OH)4(Cl)2]·(Ln = Eu (1), Gd (2), Tb (3) and Dy (4)). All four isostructural clusters were structurally and magnetically characterized. Structural analyses reveal that they are tetranuclear isostructural clusters, each consisting of two dinuclear Mn–Ln entities. Static magnetic studies indicate the presence of dominant ferromagnetic interactions in complexes 3 and 4, whereas complex 2, containing Gd, allows quantification of an antiferromagnetic interaction with JMn–Gd = −0.41 cm−1. Dynamic measurements reveal that 3 exhibits slow relaxation of the magnetization and 4 displays single-molecule magnet behavior with an energy barrier of Δ = 15.8 K and a pre-exponential factor of τ0 = 7.65 × 10−7 s, while 1 and 2 do not show any out-of-phase ac susceptibility signals. This work highlights the different contributions of the respective lanthanide ions to the overall magnetic behavior in MnIII2LnIII2 systems.Four MnIII2LnIII2 (Ln = Eu (1), Gd (2), Tb (3) and Dy (4)) clusters demonstrate distinct static and dynamic magnetic properties. Remarkably, 4 exhibits out-of-phase ac signals indicating single-molecule magnet behavior.

•Two first-row transition metal complexes are reported.•1 and 2 consist of tetranuclear manganese and binuclear cobalt.•Dominant antiferromagnetic interactions between manganese ions were observed for 1.•Static magnetic measurement for 2 confirms its mixed valence CoΙΙ/CoΙΙΙ nature.The reactions of 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L) and Mn(ClO4)2·6H2O or Co(SCN)2·3H2O in the presence of triethylamine in methanol led to the formation of two new complexes [MnΙΙΙ4(HL)2(H2L)2(CH3OH)4]·4CH3OH·(ClO4)2 (1) and [CoΙΙCoΙΙΙ(H2L)2(CH3OH)(SCN)]·1.5CH3OH·1.5H2O (2), respectively. According to structural data and magnetic properties tetranuclear complex 1 contains four homo-valence manganese (ΙΙΙ) atoms, while in the binuclear complex 2 composed of hetero-valence bi- and trivalent cobalt (ΙΙ, ΙΙΙ) atoms. Weak antiferromagnetic exchange interactions between neighboring manganese ions in 1 have place. χMT for 2 was fitted using a model of isolated cobalt (ΙΙ) ion with zero-field splitting parameters and the study confirms its mixed valence CoΙΙ/CoΙΙΙ nature. No slow magnetic relaxation effects were observed for both complexes in the absence of an applied dc magnetic field.Homo-valence tetranuclear manganese and hetero-valence binuclear cobalt complexes with the formula [MnΙΙΙ4(HL)2(H2L)2(CH3OH)4]·4CH3OH·(ClO4)2 (1) and [CoΙΙCoΙΙΙ(H2L)2(CH3OH)(SCN)]·1.5CH3OH·1.5H2O (2) have been structurally and magnetically characterized.

The synthesis, characterization and properties of two unprecedented undecanuclear heterobimetallic Zn4Ln7 complexes of formula [Zn4Ln7(L)8(O2)2(OH)4(Cl)4(H2O)4]·Cl·4H2O·4CH3CN (Ln = Gd (1), Dy (2)) encapsulating two peroxide anions are presented, representing a very rare example of a 3d-peroxo-Ln system and expanding the realm of metal-peroxo complexes. These eleven metal ions are arranged in a peculiar structural motif, where Zn4 is located at the peripheral shell wrapping Ln7 in the inner core. The Zn ions are penta-coordinate in all cases, linked to the NO2 donor atoms from the L2− ligand and to a hydroxyl group, and the apical position is occupied by a chloride anion. All LnIII ions in these systems are octa-coordinate with LnO8 and LnNO7 coordination spheres. Magnetocaloric effect (MCE) behavior has been found in the Gd analogue due to multiple low lying excited states arising from antiferromagnetic Gd–Gd exchange interactions. The Dy derivative shows frequency dependent out-of-phase signals indicating the presence of slow relaxation of magnetization below 8 K under zero applied direct current (dc) field, but without reaching a maximum, which is due to a faster quantum tunneling relaxation. The effective barrier extracted from the frequency dependent data is Ueff = 11.2 K and a τ0 of 4.18 × 10−6 s.