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The tetranuclear iron(III) compounds [Fe4(μ3-O)2(μ-LZ)4] (1–3) were obtained by reaction of FeCl3 with the shortened salen-type N2O2 tetradentate Schiff bases N,N'-bis(salicylidene)-o-Z-phenylmethanediamine H2LZ (Z = NO2, Cl and OMe, respectively), where the one-carbon bridge between the two iminic nitrogen donor atoms guide preferentially to the formation of oligonuclear species, and the ortho position of the substituent Z on the central phenyl ring selectively drives towards Fe4 bis-oxido clusters. All compounds show a flat almost-symmetric butterfly-like conformation of the {Fe4(μ3-O)2} core, surrounded by the four Schiff base ligands, as depicted by both the X-ray molecular structures of 1 and 2 and the optimized geometries of all derivatives as obtained by UM06/6-311G(d) DFT calculations. The strength of the antiferromagnetic exchange coupling constants between the iron(III) ions varies among the three derivatives, despite their magnetic cores remain structurally almost unvaried, as well as the coordination of the metal ions, with a distorted octahedral environment for the two-body iron ions, Feb, and a pentacoordination with trigonal bipyramidal geometry for the two-wing iron ions, Few. The different magnetic behavior within the series of examined compounds may be ascribed to the influence of the electronic features of Z on the electron density distribution (EDD) of the central {Fe4(μ3-O)2} core, substantiated by a Quantum Theory of Atoms In Molecules (QTAIM) topological analysis of the EDD, as obtained by UM06 calculations 1–3. [ABSTRACT FROM AUTHOR]

The syntheses of trans-IRu(4,4'-C≡CC6H4C≡CC6H4NO2)Cl(dppe)2] (19) and the systematically varied complexes trans-[Ru(4,4',4"-C≡CC6H4X2C6H4Y2C6H4NO2)Cl(L2)2] [L2 = dppe, X2 = C≡C, Y2 = (E)-CH=CH (12), C≡C (18); L2 = dppe, X2 (E)-CH=CH, Y2 C≡C (14), (E)-CH=CH (16); L2 = dppm, X2 = C≡C, Y2 = (E)-CH=CH (13); L2 dppT, X2 = (E)-CH=CH, Y2 = C≡C (15), (E)-CH=CH (17)] are reported, the latter being donor-bridge-acceptor complexes varying in bridge composition by replacement of yne with E-ene linkages, together with their cyclic voltarpmetric data, linear optical, and quadratic nonlinear optical response data. RuII/IIIoxidation potentials increase on replacing yne linkage by E-ene linkage at the phenylene adjacent to the metal center, and on replacing dppe by dppm co-ligands. The low-energy optical absorption maxima occur in the region 20400-23300 cm-1 and are metal-to-ligapd charge-transfer (MLCT) in origin; these bands undergo a blue-shift upon π-bridge lengthening by addition of phenyleneethynylene units, and on replacing E-ene linkages by yne linkages. Time-dependent density functional theory calculations on model complexes have suggested assignments for the low-energy bands. The optical spectra of selected oxidized species contain low-energy ligand-to-metal charge transfer (LMCT) bands centered in the region 9760-11800 cm-1. Quadratic molecular nonlinearities from hyper-Rayleigh scattering (HRS) studies at 1064 nm reveal an increase in the two-level-corrected βo value on π-bridge lengthening, a trend that is not seen with β values because of the blue-shift in )χmax for this structural modification. Replacing yne linkages by E-ene linkage at the phenylene adjacent to the metal center or dppm co-ligand by dppe results in an increase in β and βo values. In contrast, quadratic molecular nonlinearities by HRS at 1300 nm or electric field-induced second- harmonic generation (EFISH) studies at 1907 nm do not afford clear trends. [ABSTRACT FROM AUTHOR]

The cis influence of a series of anionic ligands X and Y has been evaluated through the magnitude of the Pt-P coupling constants for compounds of formula trans-[PtXY(PPh3)2]. The order of decreasing cis influence was found to be I > Cl > SePh ∼ SPh ∼ SEt > NO3 > AcO ∼ NO2 > H > Me > Ph > mtc (mtc = N,N-dimethylmonothiocarbamato-S); moreover, the cis influences of the various ligands was found to be additive. The X-ray structures of three representative compounds (t-4: X = Cl, Y = NO3; t-5: X = Cl, Y = AcO and t-12: X = Y = NO2) have also been determined. [ABSTRACT FROM AUTHOR]

Neutral and cationic cyclopentadienone (CpO) N‐heterocyclic carbene (NHC) bis‐carbonyl iron(0) complexes bearing, appended to the NHC ligand, either a terminal amino group on the lateral chain, [Fe(η4‐CpO)(CO)2(κC‐NHC(CH2)nNH2)] with n = 2 (2a) and 3 (2b), or a cationic NMe3+ fragment, [Fe(η4‐CpO)(CO)2(κC‐NHC(CH2)2NMe3)](I) (3), were prepared and characterized in terms of their structure, stability and reactivity. The photochemical properties of 2a and 2b were examined both in organic solvents and in water, revealing the photoactivated release of one CO ligand followed by the formation of the chelated complex [Fe(η4‐CpO)(CO)(κ2C,N‐NHC(CH2)2NH2)] (4), whose molecular structure was confirmed by single crystal X‐ray diffraction studies. This metallacyclization occurs only in the case of 2a, with the ethylene spacer between NHC ring and NH2 group in the lateral chain, allowing the formation of a stable 6‐membered ring. On the other hand, 2b undergoes decomposition upon irradiation. The reactivity in aqueous solutions revealed the chemical speciation of the complexes at different pH and especially under physiological conditions (phosphate buffer solution at pH 7.4 and 37 °C). The lack of data on the biological properties of iron(0) complexes prompted us to preliminarily investigate their cytotoxicity against model cancer cells (AsPC‐1 and HPAF‐II), along with a determination of their lipophilicity. Cyclopentadienone iron(0) complexes bearing an amino functionality on the lateral chain of the ancillary N‐heterocyclic carbene ligand show cytotoxicity properties against pancreatic cancer AsPC‐1 and HPAF‐II cells comparable to carboplatin. [ABSTRACT FROM AUTHOR]