Strategic synthesis of [Cu2], [Cu4] and [Cu5] complexes: inhibition and triggering of ligand arm hydrolysis and self-aggregation by chosen ancillary bridges.

The Schiff base ligand HL1 ({2,6-bis(allylimino)methyl}-4-methylphenol) having no coordinating donor arm has been examined for its reaction medium and ancillary bridge dependent reactivity for a hierarchical family of CuII complexes. The ligand showed a unique reactivity pattern toward CuII in solution. The bridging nature of in situ generated HO- ions in the absence and presence of externally added carboxylates (RCOO-; R = CF3, C6H5 and CH3) has been utilized to produce complexes {[Cu2(μ-L2)2(H2O)]2[Cu2(μ-L2)2(H2O)2](ClO4)6} (1) (HL2 = 3-{(allylimino)methyl}-2-hydroxy-5-methylbenzaldehyde), [Cu4(μ4-O)(μ-L1)2(μ1,3-O2CCF3)4] (2), [Cu4(μ4-O)(μ-L1)2(μ1,3-O2CC6H5)4]·H2O (3), and [Cu5(μ3-OH)2(μ-L1)2(μ1,3-OAc)2(OAc)2(H2O)4][Cu5(μ3-OH)2(μ-L1)2(μ1,3-OAc)2(OAc)3(H2O)](ClO4)3·2C2H5OH (4). The absence of carboxylate anions did not yield HO- ions in situ and triggered single ligand arm hydrolysis. The formation of tetra- and pentanuclear aggregates as well as ligand hydrolyzed dinuclear products has been rationalized to identify the possible roles of carboxylate anions in solution. Detailed characterization of the complexes in the solid state and in solution has been carried out using spectroscopic measurements, X-ray crystallography, variable temperature magnetic measurements and functional behavior. In MeOH solutions at 298 K, the complexes 1-4 showed catalytic oxidation of 3,5-di-tert-butyl catechol (3,5-DTBCH2) saturated with O2 from the air.

[1]  A. Frontera,et al.  A family of [Cu2], [Cu4] and [Cu5] aggregates: alteration of reaction conditions, ancillary bridges and capping anions , 2018 .

[2]  S. Saha,et al.  Unique trapping of paddlewheel copper(ii) carboxylate by ligand-bound {Cu2} fragments for [Cu6] assembly. , 2016, Dalton transactions.

[3]  Arindam Mukherjee,et al.  Catechol oxidase and phenoxazinone synthase: Biomimetic functional models and mechanistic studies , 2016 .

[4]  Xiaoming Liu,et al.  Mono- and tetra-nuclear copper complexes bearing bis(imino)phenoxide derived ligands: catalytic evaluation for benzene oxidation and ROP of ε-caprolactone , 2015 .

[5]  D. Dooley,et al.  Inhibition and oxygen activation in copper amine oxidases. , 2015, Accounts of chemical research.

[6]  E. Colacio,et al.  Novel anion-tunable structural diversity and new topologies in CuII complexes of a Schiff base , 2015 .

[7]  G. Sheldrick.  Crystal structure refinement with SHELXL , 2015, Acta crystallographica. Section C, Structural chemistry.

[8]  K. Hodgson,et al.  Hydroxo-Bridged Dicopper(II,III) and -(III,III) Complexes: Models for Putative Intermediates in Oxidation Catalysis , 2014, Journal of the American Chemical Society.

[9]  R. Clérac,et al.  A dodecanuclear copper(II) cage self-assembled from six dicopper building units. , 2014, Dalton transactions.

[10]  D. Das,et al.  A radical pathway in catecholase activity with nickel(II) complexes of phenol based "end-off" compartmental ligands. , 2014, Dalton transactions.

[11]  A. Giuffrida,et al.  Determination of formal redox potentials in aqueous solution of copper(II) complexes with ligands having nitrogen and oxygen donor atoms and comparison with their EPR and UV-Vis spectral features. , 2013, Journal of inorganic biochemistry.

[12]  P. Roy,et al.  Synthesis, characterization and magnetic properties of an oxido-bridged tetranuclear copper(II) complex , 2013 .

[13]  Keith S. Murray,et al.  PHI: A powerful new program for the analysis of anisotropic monomeric and exchange‐coupled polynuclear d‐ and f‐block complexes , 2013, J. Comput. Chem..

[14]  R. Clérac,et al.  Self-assembly of a pentanuclear {Cu5} complex resulting from the trapping of a Cu2+ ion by two {Cu2} building units , 2013 .

[15]  M. Drew,et al.  Insertion of a hydroxido bridge into a diphenoxido dinuclear copper(II) complex: drastic change of the magnetic property from strong antiferromagnetic to ferromagnetic and enhancement in the catecholase activity. , 2012, Inorganic chemistry.

[16]  Louis J. Farrugia,et al.  WinGX and ORTEP for Windows: an update , 2012 .

[17]  J. Atwood,et al.  Controlling the self-assembly of metal-seamed organic nanocapsules. , 2012, Angewandte Chemie.

[18]  Nigel G. R. Hearns,et al.  New phenoxido-bridged quasi-tetrahedral and rhomboidal [Cu4] compounds bearing μ4-oxido or μ(1,1)-azido ligands: synthesis, chemical reactivity, and magnetic studies. , 2011, Inorganic chemistry.

[19]  F. Mautner,et al.  Trinuclear, tetranuclear, and polymeric Cu(II) complexes from the first use of 2-pyridylcyanoxime in transition metal chemistry: synthetic, structural, and magnetic studies. , 2011, Inorganic chemistry.

[20]  M. Johnsson,et al.  Synthesis, crystal structure, and magnetic properties of the copper selenite chloride Cu5(SeO3)4Cl2. , 2010, Inorganic chemistry.

[21]  Nigel G. R. Hearns,et al.  New mu(4)-oxido-bridged copper benzoate quasi-tetrahedron and bis-mu(3)-hydroxido-bridged copper azide and copper thiocyanate stepped cubanes: core conversion, structural diversity, and magnetic properties. , 2010, Inorganic chemistry.

[22]  R. Gennis,et al.  Characterization of the Semiquinone Radical Stabilized by the Cytochrome aa3-600 Menaquinol Oxidase of Bacillus subtilis* , 2010, The Journal of Biological Chemistry.

[23]  J. Klinman,et al.  Kinetic and structural analysis of substrate specificity in two copper amine oxidases from Hansenula polymorpha. , 2010, Biochemistry.

[24]  A. Ozarowski,et al.  High-field EPR and magnetic susceptibility studies on binuclear and tetranuclear copper trifluoroacetate complexes. X-ray structure determination of three tetranuclear quinoline adducts of copper(II) trifluoroacetate. , 2009, Journal of the American Chemical Society.

[25]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[26]  Hui Wu,et al.  Synthesis, structure, and properties of a tetranuclear copper(II) tridentate Schiff-base complex with a pseudo-double-cubane core , 2005 .

[27]  J. Reedijk,et al.  Proton NMR spectroscopy and magnetic properties of a solution-stable dicopper(II) complex bearing a single mu-hydroxo bridge. , 2005, Inorganic chemistry.

[28]  K. Harms,et al.  Aerobic oxidation of 2,3,6-trimethylphenol to trimethyl-1,4-benzoquinone with copper(II) chloride as catalyst in ionic liquid and structure of the active species. , 2004, Journal of the American Chemical Society.

[29]  C. Barnes,et al.  Ligand Flexibility and Dual Complexation Modes on Reaction of 1,2- bis (2′-pyridylethynyl)Benzene with Copper(I) Halides , 2003 .

[30]  R. Mukherjee,et al.  Catecholase activity of dinuclear copper(II) complexes with variable endogenous and exogenous bridge , 2002 .

[31]  L. Rossi,et al.  Catecholase activity of a series of dicopper(II) complexes with variable Cu-OH(phenol) moieties. , 2002, Inorganic chemistry.

[32]  J. V. Van Beeumen,et al.  Purification, characterization, and preliminary crystallographic study of copper-containing nitrous oxide reductase from Pseudomonas nautica 617. , 2000, Biochemistry.

[33]  E. Monzani,et al.  Mechanistic, Structural, and Spectroscopic Studies on the Catecholase Activity of a Dinuclear Copper Complex by Dioxygen , 1999 .

[34]  Louis J. Farrugia,et al.  WinGX suite for small-molecule single-crystal crystallography , 1999 .

[35]  A. Rompel,et al.  Substrate specificity of catechol oxidase from Lycopus europaeus and characterization of the bioproducts of enzymic caffeic acid oxidation 1 , 1999, FEBS letters.

[36]  Maria Cristina Burla,et al.  SIR97: a new tool for crystal structure determination and refinement , 1999 .

[37]  J. Trombe,et al.  Synthesis and magnetic properties of a series of bi- and tri-nuclear complexes of copper(II) with the unsymmetrical tetradentate Schiff-base ligand 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid, H2fsaaep, and crystal structures of [{Cu(Hfsaaep)Cl}2] and [{Cu(fsaaep)(H2O)}2] , 1999 .

[38]  J. Bridson,et al.  Magnetostructural Correlations in Bis(&mgr;(2)-phenoxide)-Bridged Macrocyclic Dinuclear Copper(II) Complexes. Influence of Electron-Withdrawing Substituents on Exchange Coupling. , 1996, Inorganic chemistry.

[39]  M. Nardelli,et al.  PARST95 – an update to PARST: a system of Fortran routines for calculating molecular structure parameters from the results of crystal structure analyses , 1995 .

[40]  R. Blessing,et al.  An empirical correction for absorption anisotropy. , 1995, Acta crystallographica. Section A, Foundations of crystallography.

[41]  A. W. Addison,et al.  Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate , 1984 .

[42]  C. Spiro,et al.  The synthesis, redox properties, and ligand binding of heterobinuclear transition-metal macrocyclic ligand complexes. Measurement of an apparent delocalization energy in a mixed-valent copper(I)copper(II) complex , 1981 .

[43]  Glen B. Deacon,et al.  Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination , 1980 .