6533b836fe1ef96bd12a07e4

RESEARCH PRODUCT

Tuning up the Tc in Mn(II)Cu(II) bimetallic planes and design of molecular-based magnets

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Abstract A family of related compounds of general formula (PPh4)2Mn2[Cu((L)]3nH2O, where PPh4+ is the tetraphenylphosphonium cation and L stands for ortho-phenylenebis(oxamate) (opba, 1), ortho-phenylene (N′-methyloxamidate) (oxamate) (Meopba, 2) and ortho-phenylenebis (N′-methyloxamidate) (Me2opba, 3), have been synthesized. The X-ray absorption near-edge structure (XANES) and extended X-ray Within absorption fine structure (EXAFS) spectra at both Mn and Cu K-edges for all three compounds, as well as their powder X-ray patterns, are consistent with a layered structure built up of parallel Mn11Cu11 two-dimensional honeycomb networks separated by PPh4+ cations. Within the antonic metallic layers, the manganese (II) ion in an octahedral environment is surrounded by three square-planar Cu(L) bisbidentate moieties with Mn...Cu separation of about 5.4A. The magnetic properties of the three compounds have been investigated in the 1.8–300 K temperature range. Compounds 1–3 show characteristic ferrimagnetic behavior, with negative J values equal to − 31.8, − 32.6 and − 30.5 cm1, respectively. All three compounds show an abrupt ferromagnetic phase transition below a critical temperature Tc equal to 11.5, 13 and 8 K, for 1, 2 and 3, respectively. The magnetic ordering temperature values along this series of two-dimensional molecular-based magnets are analyzed and discussed in terms of the magnitude of the intramolecular interaction.