11 research outputs found
Competitive coordination aggregation for V-shaped [Co3] and disc-like [Co7] complexes: Synthesis, magnetic properties and catechol oxidase activity
No full textUnique dependence on the nature of metal salt and reaction conditions for coordination assembly reactions of varying architecture and nuclearity have been identified in V-shaped [Co3L4] and planar disc-like [Co7L6] compounds: [CoII3L2(μ-L)2(μ-OH2)2(CF3CO2)2] (1) and [CoII7(μ-L)6(μ-OMe)6]Cl2 (2) (HL = 2-(3-ethoxypropylimino)methyl-6-methoxyphenol). At room temperature varying reaction conditions, cobalt-ligand ratios and use of different bases allowed unique types of coordination self-assembly. The synthetic marvel lies in the nature of aggregation with respect to the two unrelated cores in 1 and 2. Complex 1 assumes a V-shaped arrangement bound to L-, water and a trifluoroacetate anion, while 2 grows around a central CoII ion surrounded by a CoII6 hexagon bound to methoxide and L-. Magnetic measurements revealed that the intermetallic interactions are antiferromagnetic in nature in the case of complex 1 and ferromagnetic in the case of 2 involving high spin cobalt(ii) ions with stabilization of the high-spin ground state in the latter case. In MeCN solutions complexes 1 and 2 showed catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBCH2) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) in air. The kinetic study in MeCN revealed that with respect to the catalytic turnover number (kcat) 2 is more effective than 1 for oxidation of 3,5-DTBCH2
Metal ion substitution and aldehyde exchange for CuII4 aggregates from two types of piperazine-based Schiff base ligands: Synthesis, X-ray structures, magnetic studies and theoretical validation
No full text‐L)} Fragments: Synthesis, Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity
No full text(μ‐L)} Fragments: Synthesis, Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity
No full textHeterodinuclear [Co-Ln] complexes of semicarbazide-arm bearing ligand: synthesis from the cleavage of starting [Co-Co] complex, structures and magnetic properties
No full textThe heterometallic bridging potential of the anion of 1-(2-hydroxy-3-methoxybenzylidene)-semicarbazide (HL) to CoIIand four 4f ions was examined during a 4f ion coordination-driven cleavageof [Co2(m-OH2)(O2CCMe3)4(HO2CCMe3)4](Co2-Piv) and scrambling of pivalate anions from the startingmaterial. Room-temperature reactions with four different lanthanide nitrate salts yielded [CoLnL(m2-OOCCMe3)4(CH3OH)].3CH3OH [Ln = Gd (1), Tb (2), Dy (3) and Ho (4)]. The formation in solution and thecrystallization in the solid state indicated that the reactions inhibit any further aggregation ofCo-Lncores to higher order aggregates. After scrambling, the pivalate ions in [Co-Ln] show three types ofcoordination modes to sustain the dinuclear aggregates with varying degrees of distortion in thedinuclear entities bound to a single L ion. Atom economy was maintained with respect to the pivalateions as no external addition of these anions was made. The dc magnetic measurements revealed thepresence of weak ferromagnetic interactions in complexes1and2and weak antiferromagneticinteractions in complexes3and4
Synthetic diversity and change in nuclearity in [Co-Dy] coordination aggregates: bridge removal, solvent induced structural reorganization and AC susceptibility measurements
No full textUnusually Distorted Pseudo-Octahedral Coordination Environment Around CoII from Thioether Schiff Base Ligands in Dinuclear [CoLn] (Ln = La, Gd, Tb, Dy, Ho) Complexes: Synthesis, Structure, and Understanding of Magnetic Behavior
No full textSolvent-induced structural transformation from heptanuclear to decanuclear [Co–Ln] coordination clusters: trapping of unique counteranion and understanding of aggregation pathways
No full textFive new cobalt(II/III)–lanthanide(III)-based coordination aggregates, [LnIII3CoII2CoIII2(L1)2(O2CCMe3)8(OH)4(OMe)2(H2O)4]·Ln(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2·2MeOH·2H2O (where Ln = Tb (1), Ho (3), and H2L1 = N-(2-hydroxyethyl)-salicylaldimine), TbIII3CoII3CoIII4(L1)4(O2CCMe3)9(OH)10(H2O) (4) and LnIII3CoII2CoIII5(L1)4(O2CCMe3)10(OH)10 (Ln = Dy (5), Ho (6)) have been synthesized and characterized, including structural analysis via single-crystal X-ray diffraction. The dysprosium analogue (2) of 1 and 3 was previously reported by us. The heptanuclear monocationic clusters in 1 and 3 were formed by placement of seven metal ions (4 Co and 3 Ln) in a vertex shared dicubane structure from the control of two Schiff base anions and crystallized in the presence of in situ generated and literature unknown counter anions Tb(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2− and Ho(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2−. Interesting solvent-induced cluster structure transformation was observed on dissolving the heptanuclear aggregates in MeCN for the formation of decanuclear clusters 4–6. These high nuclearity clusters consist of a vertex shared heptanuclear dicubane part and a curved trinuclear chain linking the two cubic halves. The dicubane unit differs from that of the heptanuclear precursors in the presence of CoII/III at the shared vertex as opposed to LnIII and the absence of OMe− bridges. HRMS (+ve) analysis shed light on the pathway of formation of these heptanuclear molecules, while at the same time revealing a different aggregation process for the decanuclear clusters
Inhibition of ligand arm hydrolysis and carboxylate coordination directed formation of μ4-oxido-bridged [Cu4] complexes: Synthesis, X-ray structure and functional activity
No full textThe dinuclear copper(II) complex [Cu2(µ–L2NH)2(OH2)2](ClO4)4 (1) was obtained following one imine side arm hydrolysis of HL1 (2,6-bis-[{3-(diethylamino)propylimino}methyl]-4-methylphenol). Introduction of carboxylates inhibited the hydrolysis and resulted in two tetranuclear copper(II) complexes [Cu4(µ4–O)(µ–L1)2(µ1,3–O2CCH3)4]·H2O (2a) and [Cu4(µ4–O)(µ–L1)2(µ1,3–O2CC2H5)4]·H2O (2b). Use of perchlorate and carboxylate salts of copper(II) for the reactions under study with HL1 has directed these reactions. Perchlorate anions in presence of H2O molecules, as hydrolytic nucleophiles, triggered imine arm hydrolysis and bridging carboxylate anions allowed transformation of copper(II) bound H2O molecule to μ4-oxido central nucleating group via hydroxido-bridge. The complexes were obtained from simultaneous chelation and bridging by the hydrolyzed and as used ligand anions L2NH− and HL1− respectively. These complexes have been characterized in the solid state by X-ray crystallography and FT-IR spectroscopy. Solution phase stability of Cu2-based fragments was studied by UV–vis absorption spectroscopy. Solution properties have been examined for substrate binding in catechol oxidase activity and binding affinity for biomacromolecules like DNA and Human Serum Albumin
From tetranuclear to pentanuclear [Co‒Ln] (Ln = Gd, Tb, Dy, Ho) complexes across the lanthanide series: effect of varying sequence of ligand addition
No full textTwo new families of cobalt(II/III)‒lanthanide(III) coordination aggregates have been reported: Tetranuclear [LnIII2CoIII2L2(N‒BuDEA)2(O2CCMe3)4(H2O)2]•(MeOH)n•(H2O)m (Ln = Gd, 1; Tb, 2; Dy, 3; n=2, m=10 for 1 and 2; n=6, m=2 for 3) and Pentanuclear LnIII2CoIICoIII2L2(N‒BuDEA)2(O2CCMe3)6(MeOH)2 (Ln = Dy, 4; Ho, 5) formed from the reaction of two aggregation assisting ligands H2L (o‒vanillin oxime) and N‒BuDEAH2 (N‒butyldiethanolamine). A change in preference from lower to higher nuclearity structure was observed on going across the lanthanide series brought about by the variation in size of the LnIII ions. An interesting observation was made for the varying sequence of addition of the ligands in the reaction medium paving the way to access both structural types for Ln = Dy. HRMS (+ve) of solutions gave further insight into the formation of the aggregates via different pathways. The tetranuclear complexes adopt a modified butterfly structure with a more complex bridging network while trapping of an extra CoII ion in the pentanuclear complexes destroy this arrangement putting the Co‒Co‒Co axis above the Ln‒Ln axis. Direct current (dc) magnetic susceptibility measurements reveal weak antiferromagnetic coupling in 1. Complexes 2 and 5 display no slow magnetic relaxation, whereas complexes 3 and 4 display out‒of‒phase signals at low temperature. All compounds were analyzed with DFT and CASSCF calculations and information about the single-ion anisotropies and mutual 4f‒4f / 4f‒3d magnetic interactions were derived
