Mer Isomers Research Articles

Structural Systematics of Lanthanide(III) Picrate Solvates: Molecular, Mononuclear Ln(pic)3(trimethylphosphate)3 Arrays

Adducts of the form Ln(pic)3(tmp)3 (Ln=lanthanide(iii); pic=picrate=2,4,6-trinitrophenoxide; tmp=trimethylphosphate, (MeO)3PO) have been prepared for extremal Ln=La, Lu and some intermediate members, also Y, and characterised by single crystal X-ray structure determinations as unsolvated, mononuclear, molecular species. The lanthanide atom has nine-coordinate, tri-capped trigonal prismatic stereochemistry in all cases, the picrate components behaving as O,O′-bidentate ligands chelating through the phenoxy- and an adjacent O-nitro oxygen atom, thus: [Ln(tmp-O)3(pic-O,O′)3]. Two isomeric forms are found, one mer in which the three unidentate tmp-O ligands coordinate in cis-sites spanning the upper and lower triangles and a capping site of the coordination sphere, and fac, in which all three unidentate ligands occupy the mutually cis-sites of one triangular face. The mer isomer has been described as an isomorphous series in a monoclinic P21/c, Z 4, form, for Ln=La, Ce, Pr, Nd, Sm, Gd, Lu, and Y, presumptively accessible for the full gamut of Ln. The fac-isomer also crystallises in a monoclinic P21/c form, Z 8, two independent molecules of similar stereochemistry here comprising the asymmetric unit and described for Ln=Eu, Lu(isomorphous); it has also been described in a triclinic P, Z 2 form for Ln=La.

Quantum-chemical studies of homoleptic iridium(III) complexes in OLEDs: fac versus mer isomers

A series of facial fac-[Ir(5-R-bzq)3] and meridional mer-[Ir(5-R-bzq)3] Ir(III) complexes bearing benzo[h]quinoline-based ligands have been studied with the help of density functional theory (DFT) methods. A detailed electronic structure comparison of the two isomers has been addressed to point out the differences in their stability and photophysical properties. An influence of substituent impact on optical and electronic properties of Ir(III) homoleptic complexes was also explored by introducing into the cyclometalated ligands substituents characterized with different electronic properties, e.g., R = H, F, OPh, NMe2, C6F5, and p-C6H4-NPh2. The results herein show that fac and mer isomers exhibit remarkable differences in stability and photophysical properties. The introduction of different functional groups into bzq ligands, despite very similar geometrical structures, significantly affected HOMO and LUMO energy levels and energy gaps of the examined Ir(III) complexes.

Synthesis and Computational Study of a Pyridylcarbene Fe(II) Complex: Unexpected Effects of fac/ mer Isomerism in Metal-to-Ligand Triplet Potential Energy Surfaces.

The synthesis and the steady-state absorption spectrum of a new pyridine-imidazolylidene Fe(II) complex (Fe-NHC) are presented. A detailed mechanism of the triplet metal-to-ligand charge-transfer states decay is provided on the basis of minimum energy path (MEP) calculations used to connect the lowest-lying singlet, triplet, and quintet state minima. The competition between the different decay pathways involved in the photoresponse is assessed by analyzing the shapes of the obtained potential energy surfaces. A qualitative difference between facial ( fac) and meridional ( mer) isomers' potential energy surface (PES) topologies is evidenced for the first time in iron-based complexes. Indeed, the mer complex shows a steeper triplet path toward the corresponding 3MC minimum, which lies at a lower energy as compared to the fac isomer, thus pointing to a faster triplet decay of the former. Furthermore, while a major role of the metal-centered quintet state population from the triplet 3MC region is excluded, we identify the enlargement of iron-nitrogen bonds as the main normal modes driving the excited-state decay.

Fac vs Mer Selection in Octahedral Complexes of the N-Benzyl-Substituted Triazolylpyridine Diad with Labile Metal Ions (Zinc(II), Iron(II), and Nickel(II))

Pseudo-octahedral complexes built on chelating ligands offer valuable isomeric properties such as the formation of fac vs mer isomers, and Λ vs Δ enantiomers. This article discusses factors guiding the fac vs mer selection of complexes built from the triazolyl-pyridine platform bearing a benzyl substituent, in conjunction with labile metal ions such as zinc(II), iron(II), and nickel(II). Critical parameters that are explored include the geometrical flexibility of the individual metal ion, and the nature of the counteranion. In essence, it was observed that ions which can withstand significant distortions in their first coordination sphere, such as zinc(II), generally prefer forming the mer isomer irrespective of the counteranion, whereas ions with more restricted geometry, such as iron(II), are directed either to a fac arrangement by small, tetrahedral anions such as tetrafluoroborate or perchlorate or to a mer organization by counteranions of lower symmetry, such as triflate. The molecular interactions o...

Exploring the geometrical and optical properties of neutral rhenium (I) tricarbonyl complex of 1,10-phenanthroline-5,6-diol using relativistic methods

In this contribution, we studied through experimental and relativistic DFT (R-DFT) calculations, the neutral complex fac-[Re(CO)3(1,10-phenanthroline-5,6-diol)Cl] (B1) as a potential precursor compound for designing new fluorophores suitable for confocal microscopy specially in walled cells. This work also describes via DFT calculations the electronic and spectroscopic properties of the facial (fac) and meridional (mer) isomers of this compound. The calculations shows that mer-isomer is 17.5kcal/mol (in vacum) and 21.1kcal/mol (when the solvent is considered) higher in energy with respect to the fac-isomer. The calculated emission spectra of B1, indicates an emission around 620nm in acetonitrile in good agreement with the experimental reports for similar molecules. Finally, the Morokuma–Ziegler energy decomposition analysis shows a major lability for Cl ligand which is ideal for designing new compounds replacing this ligand for another ancillary ligand suitable for biological applications.

Cationic, Neutral, and Anionic Hydrides of Iridium with PSiP Pincers

This work describes synthetic routes from the known precursor [IrClH{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}] (1) to new hydride and polyhydride derivatives. Substituting the chloride ligand with triflate leads to the five-coordinate complex [IrH{κO-O3S(CF3)}{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}] (2), which can undergo reversible coordination of water (H2O) or dihydrogen (H2) to generate respectively the cationic derivative [IrH{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}(OH2)2](CF3SO3) (3) or the neutral trans-hydride-dihydrogen [IrH{κO-O3S(CF3)}{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}(η2-H2)] (6) in equilibrium. The use of acetonitrile or carbon monoxide (CO) excess instead of water produces stable analogues of 3 (complexes 4 or 5, respectively). The reaction between 1 and NaBH4 affords the tetrahydroborate derivative [IrH{κ2H-H2BH2}{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}] (7), which can be protonated with triflic acid to form 2 or with HBF4 to give the dinuclear cationic derivative [(μ:κ2H,κ2H-BH4)[IrH{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}]2](BF4) (8). The reactions of 7 with alcohols afford either the dihydride-carbonyl [IrH2{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}(CO)] (9) or the known tetrahydride [IrH4{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}] (10), depending on the ease of alcohol decarbonylation. NMR observations and density functional theory calculations on the fluxional behavior of 10 indicate that the spatial contour of the mer PSiP framework conditions hydride-ligand exchanges. Complex 10 reacts with NaH in tetrahydrofuran to form the anionic trihydride [IrH3{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}]Na (11), which exists as a mixture of fac and mer isomers in equilibrium.

Five- and Six-Coordinated Silver(I) Complexes Derived from 2,6-(Pyridyl)iminodiadamantanes: Sustained Release of Bioactive Silver toward Bacterial Eradication.

Silver(I) complexes of two designed tridentate ligands, namely, 2,6-(pyridyl)iminoditriazaadamantane (pydTAm) and 2,6-(pyridyl)iminodiadamantane (pydAm), have been synthesized and structurally characterized. [Ag(pydTAm)2](CF3SO3) (1), the hitherto unknown mer isomer of a silver(I) octahedral complex, crystallizes in a highly symmetric body-centered cubic I4̅3m space group. Quite in contrast, the AgI center in the analogous [Ag(pydAm)2](CF3SO3) (2) complex resides in a trigonal-bipyramidal geometry and crystallizes in a triclinic P1̅ space group with two crystallographically independent molecules in the asymmetric unit. Complex 1 exhibits exceptional solubility in aqueous media and leads to the efficient eradication of several bacterial strains upon sustained release of bioactive silver.

Stereoelectronic Effects in Cl2 Elimination from Binuclear Pt(III) Complexes.

Halogen photoelimination is the critical energy-storing step of metal-catalyzed HX-splitting photocycles. Homo- and heterobimetallic Pt(III) complexes display among the highest quantum efficiencies for halogen elimination reactions. Herein, we examine in detail the mechanism and energetics of halogen elimination from a family of binuclear Pt(III) complexes featuring meridionally coordinated Pt(III) trichlorides. Transient absorption spectroscopy, steady-state photocrystallography, and far-infrared vibrational spectroscopy suggest a halogen elimination mechanism that proceeds via two sequential halogen-atom-extrusion steps. Solution-phase calorimetry experiments of the meridional complexes have defined the thermodynamics of halogen elimination, which show a decrease in the photoelimination quantum efficiency with an increase in the thermochemically defined Pt-X bond strength. Conversely, when compared to an isomeric facial Pt(III) trichloride, a much more efficient photoelimination is observed for the fac isomer than would be predicted based on thermochemistry. This difference in the fac vs mer isomer photochemistry highlights the importance of stereochemistry on halogen elimination efficiency and points to a mechanism-based strategy for achieving halogen elimination reactions that are both efficient and energy storing.

Properties of Manganese(III) Ferrocenyl-β-Diketonato Complexes Revealed by Charge Transfer and Multiplet Splitting in the Mn 2p and Fe 2p X-Ray Photoelectron Envelopes.

A series of ferrocenyl-functionalized β-diketonato manganese(III) complexes, [Mn(FcCOCHCOR)3] with R = CF3, CH3, Ph (phenyl) and Fc (ferrocenyl) was subjected to a systematic XPS study of the Mn 2p3/2 and Fe 2p3/2 core-level photoelectron lines and their satellite structures. A charge-transfer process from the β-diketonato ligand to the Mn(III) metal center is responsible for the prominent shake-up satellite peaks of the Mn 2p photoelectron lines and the shake-down satellite peaks of the Fe 2p photoelectron lines. Multiplet splitting simulations of the photoelectron lines of the Mn(III) center of [Mn(FcCOCHCOR)3] resemble the calculated Mn 2p3/2 envelope of Mn3+ ions well, indicating the Mn(III) centers are in the high spin state. XPS spectra of complexes with unsymmetrical β-diketonato ligands (i.e., R not Fc) were described with two sets of multiplet splitting peaks representing fac and the more stable mer isomers respectively. Stronger electron-donating ligands stabilize fac more than mer isomers. The sum of group electronegativities, ΣχR, of the β-diketonato pendant side groups influences the binding energies of the multiplet splitting and charge transfer peaks in both Mn and Fe 2p3/2 photoelectron lines, the ratio of satellite to main peak intensities, and the degree of covalence of the Mn–O bond.

The cyclooctadiene ligand in [IrCl(COD)]2 is hydrogenated under transfer hydrogenation conditions: A study in the presence of PPh3 and a strong base in isopropanol

The interaction of [IrCl(COD)]2 with PPh3 in isopropanol has been investigated for various P/Ir ratios, in the absence or presence of a strong base (KOtBu), at room temperature and at reflux. At room temperature, PPh3 adds to the metal center to yield [IrCl(COD)(PPh3)] and additional PPh3 only undergoes rapid degenerative ligand exchange. Subsequent addition of KOtBu affords [IrH(COD)(PPh3)2] as the main compound, even for high P/Ir ratios, although very minor amounts of products having a “HIr(PPh3)3” core are also generated. Warming to the solvent reflux temperature results in a rapid (<1 h) and quantitative COD removal from the system as hydrogenated products (54.4% of cyclooctene plus 32.2% of cyclooctane according to a quantitative GC analysis) and in the eventual generation of [IrH3(PPh3)3]. The latter is observed as a mixture of the fac and mer isomers in solvent-dependent proportions. Other minor products, one of which is suggested to be mer-cis-[IrH2(OiPr)(PPh3)3] by the NMR characterization, are also generated. These results show that, contrary to certain previously published assumptions, systems of this kind are unlikely to function via a COD-containing active species in transfer hydrogenation catalysis conducted in hot isopropanol in the presence of a strong base.

XPS Fe 2p peaks from iron tris(β-diketonates): Electronic effect of the β-diketonato ligand

The Fe 2p photoelectron lines, as measured by X-ray photoelectron spectra (XPS), of a series of tris(β-diketonato)iron(III) complexes, are sensitive to the electron donating and withdrawing properties of the ligand attached to the iron atom. The maximum binding energy of the Fe 2p3/2 envelope revealed a linear relationship with the combined Gordy scale group electronegativity of the R-groups substituted on the respective β-diketonato ligand (RCOCHCOR′)−. A linear relationship between the binding energies and other electronic parameters was also obtained. Within these relationships, there are specific clusters of complexes defined by the amount of CF3 groups substituted per β-diketonato ligand. These specific clusters of complexes show an opposite trend inversely proportional to the general trend. It was also shown that the Fe 2p photoelectron peaks can be fitted with calculated multiplet splitting peaks, according to the synthetically generated multiplet splitting test spectra, as calculated by Gupta and Sen for a free Fe(III) ion. The tris(β-diketonato)iron(III) complexes containing unsymmetrically substituted β-diketonato ligands (RCOCHCOR′)−, were fitted with two different sets of multiplet splitting peaks, which are assigned to the fac and mer isomers of these complexes.

Mer-Tri-chlorido-tris-(tetra-hydro-thio-phene-κS)iridium(III): preparation and comparison with other mer-tri-chlorido-tris-(tetra-hydro-thio-phene-κS)metal complexes.

The title complex, [IrCl3(C4H8S)3], was prepared according to a literature method. A suitable crystal was obtained by diffusion of pentane into a di-chloro-methane solution and analyzed by single-crystal X-ray diffraction at 100 K. The title complex is isotypic with mer-tri-chlorido-tris-(tetra-hydro-thio-phene-κS)rhodium(III). However, the orientation of the tetra-hydro-thio-phene rings is different from an earlier report of mer-tri-chlorido-tris-(tetra-hydro-thio-phene-κS)iridium(III) deposited in the Cambridge Structural Database. The IrS3Cl3 core shows a nearly octa-hedral structure with various bond angles within 1-2° of the perfect 90 or 180° expected for an octa-hedron. The structure of the title compound is compared with the previous iridium complex as well as the rhodium and other octa-hedral metal tris-tetra-hydro-thio-phene compounds previously structurally characterized. DFT calculations were performed, which indicate the mer isomer is significantly lower in energy than the fac isomer by 50.1 kJ mol-1, thereby accounting for all compounds in the CSD being of the mer geometry. Powder X-ray diffraction of the bulk material showed that the preparation method yielded only the isomorph reported in this communication.

X-ray and electronic structure of tris(benzoylacetonato-κ2O,O′)iron(III)

Solid state crystal data of d5 tris(benzoylacetonato-κ2O,O′)iron(III), [Fe(ba)3], are presented. The mer isomer crystallized in the solid state. Density functional theory calculations show that both fac and mer isomers of [Fe(ba)3] can exist. Both fac and mer [Fe(ba)3] are high spin d5 complexes with the same ordering of the d-based molecular orbitals in order of increasing orbital energy, namely dxy < dyz ≈ dxz < dz2 ≈ dx2-y2.

Jahn-Teller distortion in tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato]manganese(III) isomers: An X-ray and computational study

The solid state crystal data of a mer isomer of the [Mn(CF3COCHCOC4H3S)3] complex, [Mn(tfth)3], exhibits elongation Jahn-Teller distortion (elongation of the metal-ligand bonds along the z-axis and shortening of the metal-ligand bonds along both the x and y-axes). Density functional theory calculations (DFT) show that one fac and three mer isomers of [Mn(tfth)3] can exist. The difference between the three mer isomers of [Mn(tfth)3] is that the Jahn-Teller elongation of the two trans axial Mn-O bonds along the z-axis occur along three different Otfth-Mn-Otfth bonds. DFT calculations further show that the ground state geometry of all the [Mn(tfth)3] isomers exhibits elongation Jahn-Teller distortion.

Geometrical isomers of tris(β-diketonato)metal(III) complexes for M = Cr or Co: Synthesis, X-ray structures and DFT study

Solid state crystal data of three tris(β-diketonato)metal(III) complexes (M=Cr or Co), representative of the three different molecular symmetries that these complexes can obtain, namely D3, C3 or C1 symmetry, are presented and compared with related experimental structures. Density functional theory calculations show that both fac and mer isomers of tris(β-diketonato)metal(III) complexes containing unsymmetrical β-diketonato ligands can exist, in agreement with experimental NMR data. The orbital ordering for both the S=3/2 [Cr(acac)3] and S=0 [Co(acac)3] (Hacac=acetylacetone) complexes in order of increasing orbital energy is: dxy<dxz,dyz<dz2,dx2-y2.

Comparison of X-ray photoelectron spectroscopy multiplet splitting of Cr 2p peaks from chromium tris(β-diketonates) with chemical effects

X-ray photoelectron spectra (XPS) measurements of a series of chromium(III) β-diketonato complexes of the Cr 2p spectra was fitted with calculated multiplet peaks. The XPS of these Cr(III) complexes did not exhibit fine structure, however, well-defined line shapes could be fitted to the Cr 2p3/2 envelope. The splitting patterns obtained for the Cr(III) β-diketonato complexes compared well with the multiplet splitting predicted by Gupta and Sen for the free Cr(III) ion. The Cr(III) β-diketonato complexes containing unsymmetrically substituted β-diketonato ligands, which display both the fac and mer isomers, could be fitted with two sets of multiplets and were useful in determining the ratio between the fac and mer isomers, which was compared with the Boltzman calculated ratio obtained from density functional theory energies. The obtained binding energy of the first multiplet splitting peak of the Cr 2p3/2 envelope was found to be dependent on the combined Gordy group electronegativity of the R-groups substituted on the β-diketonato ligand (RCOCHCOR′)−.

Manganese-Vanadate Hybrids: Impact of Organic Ligands on Their Structures, Thermal Stabilities, Optical Properties, and Photocatalytic Activities.

Manganese(II)-vanadate(V)/organic hybrids were prepared in high purity using four different N-donor organic ligands (2,6:2',2″-terpyridine = terpy, 2,2'-bipyrimidine = bpym, o-phenanthroline = o-phen, and 4,4'-bipyridine = 4,4'-bpy), and their crystalline structures, thermal stabilities, optical properties, photocatalytic activities and electronic structures were investigated as a function of the organic ligand. Hydrothermal reactions were employed that targeted a 1:2 molar ratio of Mn(II)/V(V), yielding four hybrid solids with the compositions of Mn(terpy)V2O6·H2O (I), Mn2(bpym)V4O12·0.6H2O (II), Mn(H2O)(o-phen)V2O6 (III), and Mn(4,4'-bpy)V2O6·1.16H2O (IV). The inorganic component within these hybrid compounds, that is, [MnV2O6], forms infinite chains in I and layers in II, III, and IV. In each case, the organic ligand preferentially coordinates to the Mn(II) cations within their respective structures, either as chelating and three-coordinate (mer isomer in I) or two-coordinate (cis isomers in II and III), or as bridging and two coordinate (trans isomer in IV). The terminating ligands in I (terpy) and III (o-phen) yield nonbridged "MnV2O6" chains and layers, respectively, while the bridging ligands in II (bpym) and IV (4,4'-bpy) result in three-dimensional, pillared hybrid networks. The coordination number of the ligand, that is, two- or three-coordinate, has the predominant effect on the dimensionality of the inorganic component, while the connectivity of the combined metal-oxide/organic network is determined by the chelating versus bridging ligand coordination modes. Each hybrid compound decomposes into crystalline MnV2O6 upon heating in air with specific surface areas from ∼7 m(2)/g for III to ∼41 m(2)/g for IV, depending on the extent of structural collapse as the lattice water is removed. All hybrid compounds exhibit visible-light bandgap sizes from ∼1.7 to ∼2.0 eV, decreasing with the increased dimensionality of the [MnV2O6] network in the order of I > II ≈ III > IV. These bandgap sizes are smaller by ∼0.1-0.4 eV in comparison to related vanadate hybrids, owing to the addition of the higher-energy 3d orbital contributions from the Mn(II) cations. Each compound also exhibits temperature-dependent photocatalytic activities for hydrogen production under visible-light irradiation in 20% methanol solutions, with threshold temperatures of ∼30 °C for III, ∼36 °C for I, and ∼40 °C for II, IV, and V4O10(o-phen)2. Hydrogen production rates are ∼142 μmol H2 g(-1)·h(-1), ∼673 μmol H2 g(-1)·h(-1), ∼91 μmol H2 g(-1)·h(-1), and ∼218 μmol H2 g(-1)·h(-1) at 40 °C, for I, II, III, and IV, respectively, increasing with the oxide/organic network connectivity. In contrast, the related V4O10(o-phen)2 exhibits a much lower photocatalytic rate of ∼36 H2 g(-1)·h(-1). Electronic structure calculations based on density-functional theory methods show that the valence band edges are primarily derived from the half-filled Mn 3d(5) orbitals in each, while the conduction band edges are primarily comprised of contributions from the empty V 3d(0) orbitals in I and II and from ligand π* orbitals in III. Thus, the coordinating organic ligands are shown to significantly affect the local and extended structural features, which has elucidated the underlying relationships to their photocatalytic activities, visible-light bandgap sizes, electronic structures, and thermal stabilities.

Nonoxido Vanadium(IV) Compounds Involving Dithiocarbazate-Based Tridentate ONS Ligands: Synthesis, Electronic and Molecular Structure, Spectroscopic and Redox Properties.

A new series of nonoxido vanadium(IV) compounds [VL2] (L = L(1)-L(3)) (1-3) have been synthesized using dithiocarbazate-based tridentate Schiff-base ligands H2L(1)-H2L(3), containing an appended phenol ring with a tert-butyl substitution at the 2-position. The compounds are characterized by X-ray diffraction analysis (1, 3), IR, UV-vis, EPR spectroscopy, and electrochemical methods. These are nonoxido V(IV) complexes that reveal a rare distorted trigonal prismatic arrangement around the "bare" vanadium centers. Concerning the ligand isomerism, the structure of 1 and 3 can be described as intermediate between mer and sym-fac isomers. DFT methods were used to predict the geometry, g and (51)V A tensors, electronic structure, and electronic absorption spectrum of compounds 1-3. Hyperfine coupling constants measured in the EPR spectra can be reproduced satisfactorily at the level of theory PBE0/VTZ, whereas the wavelength and intensity of the absorptions in the UV-vis spectra at the level CAM-B3LYP/gen, where "gen" is a general basis set obtained using 6-31+g(d) for S and 6-31g for all the other elements. The results suggest that the electronic structure of 1-3 can be described in terms of a mixing among V-dxy, V-dxz, and V-dyz orbitals in the singly occupied molecular orbital (SOMO), which causes a significant lowering of the absolute value of the (51)V hyperfine coupling constant along the x-axis. The cyclic voltammograms of these compounds in dichloroethane solution display three one-electron processes, two in the cathodic and one in the anodic potential range. Process A (E1/2 = +1.06 V) is due to the quasi-reversible V(IV/V) oxidation while process B at E1/2 = -0.085 V is due to the quasi-reversible V(IV/III) reduction, and the third one (process C) at a more negative potential E1/2 = -1.66 V is due to a ligand centered reduction, all potentials being measured vs Ag/AgCl reference.

2‐Amino‐5‐(2‐pyridyl)‐thiadiazole as Bidentate Ligand

AbstractThe amino substituted bidentate chelating ligand 2‐amino‐5‐(2‐pyridyl)‐1,3,4‐thiadiazole (H2L) was used to prepare 3:1‐type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [FeII(H2L)3](ClO4)2·0.6MeOH·0.9H2O a 1:1 mixture of mer and fac isomers is present whereas [FeII(H2L)3](BF4)2·MeOH·H2O, [CoII(H2L)3](ClO4)2·2H2O and [NiII(H2L)3](ClO4)2·MeOH·H2O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [FeII(H2L)3]2+ complex core to exist in the low‐spin state, whereas the [CoII(H2L)3]2+ complex core resides in its high‐spin state, even at very low temperatures.

Heterometallic complexes with gold(I) metalloligands: self-assembly of helical dimers stabilized by weak intermolecular interactions and solvophobic effects.

New gold(I) alkynyl metalloligands bpylCCAuL, bpyl'CCAuPPh3 , and PPN[Au(CCbpyl')2 ] (bpyl or bpyl'=2,2'-bipyridin-5-yl or -4-yl, respectively; L=PMex Ph3-x (x=1-3), P(C6 H3 Me2 -3,5)3 , PCy3 , XyNC) have been synthesized. Ligands bpylCCH and metalloligands bpylCCAuL (L=PPh3 , PMePh2 , PCy3 , CNXy) react with MX2 (M=Fe, Zn, X=ClO4 ; M=Co, X=BF4 ) to give complexes [M(bpylCCZ)3 ]X2 (Z=H or AuL). In most cases, these complexes are mixtures of fac and mer isomers in a statistical distribution, in both CH2 Cl2 and MeCN. However, for L=PPh3 , the fac isomer is dominant in MeCN. NMR and ESI-MS studies, together with the crystal structure of [Co(bpylCCAuPPh3 )3 ](BF4 )2 , suggest that this solvent dependence is originated by the formation of helical dimers between two fac complexes in MeCN. These dimers are stabilized by solvophobic effects and multiple intermolecular interactions. Complex [Fe(Ph3 PAuCCbpdiylCCAuPPh3 )3 ](ClO4 )2 (bpdiyl=2,2'-bipyridin-5,5'-diyl) was obtained by reaction of three diauro diethynylbipyridines and Fe(ClO4 )2 .