Synthetic ferroverdins, NaFe¹¹(RQ)₃ afford trinuclear M[Fe(RQ)₃]₂ upon reaction with bivalent ions (M²⁺). A probable bonding mode is considered. Ferric ions oxidise ferroverdin to ferriverdin, Fe^III(RQ)₃. Bothfac andmer isomers can be observed for ferro- and ferriverdins but at equilibrium the preferred isomers arefac for ferro- andmer for ferriverdin. Mismatch in geometry with oxidation state gets spontaneously corrected by isomerisation. Equilibrium constants, isomerisation rates, redox potentials and EPR spectra are examined. A study on the pattern of isomer population as a function of oxidation for other 3d analogues of ferro- and ferriverdin is initiated.

A series of model complexes for the type III site, in oxidised hemocyanin, containing Cu₂(μ-0Ph)³⁺ core have been synthesised using a heptadentate ligand (H₃L) formed from the Schiff base condensation of triethylenetetramine and salicylaldehyde. The ligand provides one imine and one inbuilt imidazole nitrogen and two phenolic oxygen donors with both five- and six-membered chelate rings to each metal centre. In the pentacoordinated complexes [Cu₂(L)X]·nH₂O, a third exogenous bridging ligand is present. The TG curve indicates the loss of lattice water molecules between 70 and 125°C. The residue after decomposition is CuO above 550°C. Theg values of theX-band EPR spectrum of [Cu₂L(μ-OAc)]·2H₂O in methanol glass (77 K) are typical of a variety of bridged copper(II) dimers. The copper-copper magnetic interaction is dependent on the presence and nature of X in these complexes.

A family of dithiocarbonate sulphur bridged dinuclear copper(II) complexes containing [Cu₂^II(μ-Rx)μ-OPh)]²⁺ (R=Me, Et,ⁿPr,ⁱPr,ⁿBu, Bz; x=OCS₂) core with supporting weak imidazolidine bridge has been synthesized for the first time using aμ-bis(tetradentate) amine phenol ligand (H₃L). The ligand reacts with CuCl₂·2H₂O and different KRx in aqueous acetone in air affording crystalline [Cu₂(μ-Rx)(μ-L)]·2H₂O in excellent yields. Both the Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes have MN₂O₂ S coordination spheres. Taking the help of one exogenous bridging ligand (Rx⁻) the triply bridged Cu^II-Cu^II intimate complex is formed in a Schiff-base ligating environment. The ligand provides one imine and one inbuilt imidazolidine nitrogen and two phenolic bridging and terminal oxygen donors forming five- and six- membered chelate rings around each metal centre. In the pentacoordinated complexes [Cu₂(μ-Rx)(μ-L)]·2H₂O, dithiocarbonate ligands are present as exogenous bridging ligands. The presence of large polarizable sulphur atoms around each copper(II) centre significantly modify the nature of the complexes to be electroactive as detected by cyclic voltammetry, compared to the analogous exogenous acetate bridging complexes. The copper-copper magnetic interaction is dependent on the nature of different R groups and presence of S donors. Both electron transfer behaviours and magnetic properties of copper(II)-copper(II) complexes are assessed with respect to a heterodinuclear copper(II)-zinc(II) complex in identical ligating environment.

Low-temperature stoichiometric Schiff base reaction in air in 3:1 mole ratio between benzaldehyde and triethylenetetramine (trien) in methanol yields a novel tetraaza μ-bis (bidentate) acyclic ligand L. It was characterized by elemental analysis, IR, EI mass and NMR (¹H and¹³C) spectra. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging unit gives rise to a new type of imidazolidine-bridged ligand. A geometric optimisation was made of the synthesized ligand and its complexes by the method of molecular mechanics (MM2) method in order to establish the stable conformations. This hitherto unknown tetraaza acyclic ligand affords new cationic dicopper(I/I) and dicopper(II/II) complexes in good yield. Dicopper(II/II) complex displays weakd-d transition bands in the visible region, while dicopper(I/I) complex displays strong MLCT band in the same region. Both the dinuclear complexes are of non-intimate nature and show interesting solution electrochemical behaviour. EPR spectral study of μ-bis (imidazolidino) bridged dicopper(II/II) complex also supports the non-communicative nature of the two copper centres within the same molecule

The coordination cluster [Cu₂(𝜇-OMe)($\mu_{1,1}$-N₃)(𝜇-bcp)(N₃)]₂ (1; Hbcp = 2,6-bis(2-benzoyl-4-chloro-phenylimino)-methyl)-4-methylphenol, forming a new member within the rapidly growing family of Cu₄ cluster complexes, has been synthesized and structurally characterized by X-ray crystallography. The complex crystallizes in the monoclinic system, space group P2₁/𝑐, with unit cell parameters a = 14.620(7) Å, b = 17.923(8) Å, c = 15.008(7) Å, 𝛽 = 115.815(14)° and Z = 2. It is the first example of a rhomboidal [Cu₄] compound formed from $\mu_{1,1}$-azido clipping of two methoxido bridged [Cu₂] complexes showing asymmetric coordination from benzophenone oxygen atoms and terminal azido groups.