Dinuclear and tetranuclear iron(III) complexes containing the μ-oxo-di-μ-acetato motif

Fundamental electron-transfer and proton-coupled electron-transfer properties of Ru(iv)-oxo complexes

Reorganization energies (λ) of electron transfer (ET) and proton-coupled ET (PCET) from electron donors to isolated Ru^IV(O) complexes were determined to be in the range of 1.70–1.88 eV (ET) and 1.20–1.26 eV (PCET).

Non-heme μ-Oxo- and bis(μ-carboxylato)-bridged diiron(iii) complexes of a 3N ligand as catalysts for alkane hydroxylation: stereoelectronic factors of carboxylate bridges determine the catalytic efficiency

The stereoelectronic factors of carboxylate bridges in diiron(iii) complexes determine the efficiency of catalytic alkane hydroxylation with m-CPBA.

Syntheses, emission properties and intramolecular ligand exchange of zinc complexes with ligands belonging to the tmpa family

The zinc complexes [(L1)(2)Zn(MeOH)(2)](OTf)(2), [(L1)ZnCl(2)], [(L2)ZnCl(2)], [(L2)Zn(OTf)(H(2)O)]OTf and [(Me-bispic)ZnCl(2)] of the ligands N-[(2-pyridyl)methyl]-2,2'-dipyridylamine (L1), N-[bis(2-pyridyl)methyl]-2-pyridylamine (L2) and N-methyl-[bis(2-pyridyl)methyl]amine (Me-bispic) were synthesised and characterised. The first copper(I) complexes of the ligands L1 and L2 were also synthesised and structurally characterised. [(L1)ZnCl(2)] showed unexpected fluxional behaviour in solution and revealed an interesting intramolecular ligand exchange mechanism in the coordination sphere of the zinc ion. Furthermore, strong blue emission was observed under UV-light excitation.

Novel rectangular [Fe4(mu4-OHO)(mu-OH)(2)](7+) versus "butterfly" [Fe4(mu3-O2](8+) core topology in the Fe(III)/RCO2(-)/phen reaction systems (R = Me, Ph; phen = 1,10-phenanthroline): preparation and properties of [Fe4(OHO)(OH)(2)(O2CMe)(4)(phen)(4)](ClO4)(3), [Fe4O2(O2CPh)(7)(phen)(2)](ClO4), and [Fe4O2(O2CPh)(8)(phen)(2)]

The preparations, X-ray structures, and detailed physical characterizations are presented for three new tetranuclear Fe(III)/RCO(2)(-)/phen complexes, where phen = 1,10-phenanthroline: [Fe(4)(OHO)(OH)(2)(O(2)CMe)(4)(phen)(4)](ClO(4))(3).4.4MeCN.H(2)O (1.4.4MeCN.H(2)O); [Fe(4)O(2)(O(2)CPh)(7)(phen)(2)](ClO(4)).2MeCN (2.2MeCN); [Fe(4)O(2)(O(2)CPh)(8)(phen)(2)].2H(2)O (3.2H(2)O). Complex 1.4.4MeCN.H(2)O crystallizes in space group P2(1)/n, with a = 18.162(9) A, b = 39.016(19) A, c = 13.054(7) A, beta = 104.29(2) degrees, Z = 4, and V = 8963.7 A(3). Complex 2.2MeCN crystallizes in space group P2(1)/n, with a = 18.532(2) A, b = 35.908(3) A, c = 11.591(1) A, beta = 96.42(1) degrees, Z = 4, and V = 7665(1) A(3). Complex 3.2H(2)O crystallizes in space group I2/a, with a = 18.79(1) A, b = 22.80(1) A, c = 20.74(1) A, beta = 113.21(2) degrees, Z = 4, and V = 8166(1) A(3). The cation of 1 contains the novel [Fe(4)(mu(4)-OHO)(mu-OH)(2)](7+) core. The core structure of 2 and 3 consists of a tetranuclear bis(mu(3)-O) cluster disposed in a "butterfly" arrangement. Magnetic susceptibility data were collected on 1-3 in the 2-300 K range. For the rectangular complex 1, fitting the data to the appropriate theoretical chi(M) vs T expression gave J(1) = -75.4 cm(-1), J(2) = -21.4 cm(-1), and g = 2.0(1), where J(1) and J(2) refer to the Fe(III)O(O(2)CMe)(2)Fe(III) and Fe(III)(OH)Fe(III) pairwise exchange interactions, respectively. The S = 0 ground state of 1 was confirmed by 2 K magnetization data. The data for 2 and 3 reveal a diamagnetic ground state with antiferromagnetic exchange interactions among the four high-spin Fe(III) ions. The exchange coupling constant J(bb) ("body-body" interaction) is indeterminate due to prevailing spin frustration, but the "wing-body" antiferromagnetic interaction (J(wb)) was evaluated to be -77.6 and -65.7 cm(-1) for 2 and 3, respectively, using the appropriate spin Hamiltonian approach. Mössbauer spectra of 1-3 are consistent with high-spin Fe(III) ions. The data indicated asymmetry of the Fe(4) core of 1 at 80 K, which is not detected at room temperature due to thermal motion of the core. The spectra of 2 and 3 analyze as two quadrupole-split doublets which were assigned to the body and wing-tip pairs of metal ions. (1)H NMR spectra are reported for 1-3 with assignment of the main resonances.

Synthesis, structure, and magnetic properties of tetranuclear cubane-like and chain-like iron(II) complexes based on the N(4)O pentadentate dinucleating ligand 1,5-bis[(2-pyridylmethyl)amino]pentan-3-ol

The tetranuclear complexes [Fe(4)(pypentO)(pym)(3)(Oac)(NCS)(3)] x 1.5EtOH (1), [Fe(4)(pypentO)(pym)(Oac)(2)(NCS)(2)(MeO)(2)(H(2)O)] x H(2)O (2), [Fe(2)(pypentO)(NCO)(3)](2) (3), and [Fe(2)(pypentO)(N(3))(3)](2) (4) have been prepared, and their structure and magnetic properties have been studied (pypentOH = 1,5-bis[(2-pyridylmethyl)amino]pentan-3-ol, pymH = 2-pyridylmethanol). The X-ray diffraction analysis of 1 (C(43)H(53)N(10)O(7.5)S(3)Fe(4), monoclinic, P2(1)/n, a = 11.6153(17) A, b = 34.391(17) A, c = 14.2150(18) A, beta = 110.88(5) degrees, V = 5305(3) A(3), Z = 4) and 2 (C(31)H(45)N(7)O(10)S(2)Fe(4), monoclinic, C2/c, a = 19.9165(17) A, b = 21.1001(12) A, c = 21.2617(19) A, beta = 104.441(10) degrees, V = 8652.7(12) A(3), Z = 8) showed a Fe(4)O(4) cubane-like arrangement of four iron(II) atoms, four mu(3)-O bridging ligands, one (1) or two (2) syn-syn bridging acetates. The X-ray diffraction analysis of 3 (C(40)H(46)N(14)O(8)Fe(4), monoclinic, P2(1)/c, a = 11.7633(18) A, b = 18.234(3) A, c = 10.4792(16) A, beta = 99.359(18) degrees, V = 2217.7(6) A(3), Z = 2) and 4 (C(34)H(46)N(26)O(2)Fe(4), monoclinic, P2(1)/c, V = 4412.4(10) A(3), a = 23.534(3) A, b = 18.046(2) A, c = 10.4865(16) A, beta = 97.80(2) degrees, Z = 4) showed a zigzag bis-dinuclear arrangement of four iron(II) cations, two mu(2)-O bridging pypentO ligands, four mu(2)-N-cyanato bridging ligands (3) or four end-on azido bridging ligands (4): they are the first examples of cyanato and azido bridged discrete polynuclear ferrous compounds, respectively. The Mössbauer spectra of 1 are consistent with four different high-spin iron(II) sites in the Fe(4)O(4) cubane-type structure. The Mössbauer spectra of 3 are consistent with two high-spin iron(II) sites (N(5)O and N(4)O). Below 190 K, the Mössbauer spectra of 4 are consistent with one N(5)O and two N(4)O high-spin iron(II) sites. The temperature dependence of the magnetic susceptibility was fitted with J(1) approximately 0 cm(-1), J(2) = -1.3 cm(-1), J(3) = 4.6 cm(-1), D = 6.4 cm(-1), and g = 2.21 for 1; J(1) = 2.6 cm(-1), J(2) = 2.5 cm(-1), J(3) = - 5.6 cm(-1), D = 4.5 cm(-1), and g = 2.09 for 2; J(1) = 1.5 cm(-1), J(2) = 0.2 cm(-1), D = - 5.6 cm(-1), D' = 4.5 cm(-1), and g = 2.14 for 3; and J(1) = - 2.6 cm(-1), J(2) = 0.8 cm(-1), D= 6.3 cm(-1), D' = 1.6 cm(-1), and g = 2.18 for 4. The differences in sign among the J(1), J(2), and J(3) super-exchange interactions indicate that the faces including only mu(3)-OR bridges exhibit ferromagnetic interactions. The nature of the ground state in 1-3 is confirmed by simulation of the magnetization curves at 2 and 5 K. In the bis-dinuclear iron(II) compounds 3 and 4, the J(2) interaction resulting from the bridging of two Fe(2)(pypentO)X(3) units through two pseudo-halide anions is ferromagnetic in 3 (X = mu(2)-N-cyanato) and may be either ferro- or antiferromagnetic in 4 (X = end-on azido). The J(1) interaction through the central O(alkoxo) and pseudo-halide bridges inside the dinuclear units is ferromagnetic in 3 (X = mu(2)-N-cyanato) and antiferromagnetic in 4 (X = end-on azido). In agreement with the symmetry of the two Fe(II) sites in complexes 3 and 4, D (pentacoordinated sites) is larger than D' (octahedral sites).