Transition metal complexes of a versatile polyalkoxy oxazolidine-based ligand derived from in situ cyclization

YesOne-pot reaction between 8-hydroxyquinoline-2-carboxaldehyde (HQC) and tris(hydroxymethyl)aminomethane (TRIS) followed by in situ cyclization yielded an oxazolidine based ligand which produced four mononuclear complexes of MnII(1), CoII(2), NiII(3), ZnII(4), a tetranuclear iron (FeIII4) complex (5) and a trinuclear cobalt (CoIICoIII2) complex (6). Magnetic studies show dominant antiferromagnetic interaction in tetranuclear iron (FeIII4) complex 5 and presence of the slow relaxation of magnetisation in 6. The compounds were also studied for their antibacterial properties. The oxazolidine ligand (H3L2) of this study showed good antimicrobial activity not only against Gram-positive bacteria but against Gram-negative bacteria too. The antimicrobial efficacy of the metal complexes (1–6) is also reported.The full-text of this article will be released for public view at the end of the publisher's embargo period on 11 Apr 2019

Ferrotoroidic ground state in a heterometallic {Cr^IIIDy^III<inf>6</inf>} complex displaying slow magnetic relaxation

© 2017 The Author(s). Toroidal quantum states are most promising for building quantum computing and information storage devices, as they are insensitive to homogeneous magnetic fields, but interact with charge and spin currents, allowing this moment to be manipulated purely by electrical means. Coupling molecular toroids into larger toroidal moments via ferrotoroidic interactions can be pivotal not only to enhance ground state toroidicity, but also to develop materials displaying ferrotoroidic ordered phases, which sustain linear magneto-electric coupling and multiferroic behavior. However, engineering ferrotoroidic coupling is known to be a challenging task. Here we have isolated a {CrIIIDyIII6} complex that exhibits the much sought-after ferrotoroidic ground state with an enhanced toroidal moment, solely arising from intramolecular dipolar interactions. Moreover, a theoretical analysis of the observed sub-Kelvin zero-field hysteretic spin dynamics of {CrIIIDyIII6} reveals the pivotal role played by ferrotoroidic states in slowing down the magnetic relaxation, in spite of large calculated single-ion quantum tunneling rates

Benzoxazole-Based Heterometallic Dodecanuclear Complex [(Dy4Cu8II)-Cu-III] with Single-Molecule-Magnet Behavior

International audienceThree Cu-Ln (Ln = Dy, Gd, Y) dodecanuclear clusters assembled by a novel ligand of the benzoxazole type are reported. The dysprosium cluster exhibits a frequency dependence of the alternating-current susceptibility and hysteresis loop at low temperature, indicating single-molecule-magnet behavior

Tailoring antibacteria agents: Sulfonamide-based dinuclear and 1D polymer Cu(II) complexes

cited By 6International audienceStarting from two bioactive sulfonamide-based ligands (HL1: 4-amino-N-(2,6-dimethoxy-4-pyrimidinyl)benzenesulfonamide; HL2: 4-amino-N-(4-methyl-2-pyrimidinyl)benzenesulfonamide) and Cu(II) salts ([Cu 2(Ac) 4] and CuCl 2, Ac = acetate), the synthesis of [Cu 2(Ac) 2(L1) 2] (1) and [Cu 2(L2) 4] (2) and Cu(L1) 2(bipy) n·2nH 2O·n(CH 3OH) (1′) (bipy = 4,4′-bipy) architectures with potential antibiotic and antiseptic activities is reported. To confirm the possibility to fulfill specific criteria and ultimately combine both properties, the bioactive sulfonamide-based complexes are structurally, electrochemically and magnetically characterized. Depending on the synthesis conditions, the Cu:sulfonamide stoichiometry and Cu···Cu communication are first varied by controlling the chemical nature of the ancillary ligand (Ac or bipy). Then, electrochemistry data support the stability of 1 and 2 dinuclear complexes, and 1′ 1D polymer, a prerequisite for their bioactivity in solution. Interestingly, the synthesis leads to architectures where the (SO 2-Ph-NH 2) moiety which is responsible for the antibacterial activity remains non-coordinated in the vicinity of Cu(II) antiseptic ions. Magnetic susceptibility measurements combined to multireference wavefunction ab initio calculations evidence a rather strong antiferromagnetic behavior in the dinuclear compounds (H = -2JS 1S 2, 2J 1 = -307.8 cm -1 in 1, 2J 2 = -63.2 cm -1 in 2) whereas chain 1′ is paramagnetic. The cooperativity quantified by the hopping integral which is available from the ab initio calculations of the exchange coupling constant is reduced by a factor of two when the number of sulfonamide ligands increases in complexes 1 and 2. In contrast, it is negligibly small in the 1D polymer 1′. These characterized bioactive sulfonamide-based Cu(II) compounds appear as promising targets, complying with the structural and electronic expectations for antibacterial and antiseptic purposes. Finally, the antibacterial activity studies question the prerequisite for cooperative metal centers to rationally design antibacterial agents since the minimum inhibitory concentration in the paramagnetic chain 1′ is greatly reduced as compared to antiferromagnetic complexes 1 and 2. © 2012 Elsevier Ltd. All rights reserved

Mechanism Elucidation of the cis-trans Isomerization of an Azole

International audienc