Neutral Transition Metal Complexes Research Articles

Synthesis, Study, and Application of Pd(II) Hydrazone Complexes as the Emissive Components of Single-Layer Light-Emitting Electrochemical Cells.

For the first time, square planar Pd(II) complexes of hydrazone ligands have been investigated as the emissive components of light-emitting electrochemical cells (LECs). The neutral transition metal complex, [Pd(L1)2]·2CH3OH (1), (HL1 = (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinhydrazide), was prepared and structurally characterized. Complex 1 displays quasireversible redox properties and is emissive at room temperature in solution with a λmax of 590 nm. As a result, it was subsequently employed as the emissive material of a single-layer LEC with configuration FTO/1/Ga/In, where studies reveal that it has a yellow color with CIE(x, y) = (0.33, 0.55), a luminance of 134 cd cm-2, and a turn-on voltage of 3.5 V. Protonation of the pendant pyridine nitrogen atoms of L1 afforded a second ionic complex [Pd(L1H)2](ClO4)2 (2) which is also emissive at room temperature with a λmax of 611 nm, resulting in an orange LEC with CIE(x, y) = (0.43, 0.53). The presence of mobile anions and cations in the second inorganic transition metal complex resulted in more efficient charge injection and transport which significantly improved the luminance and turn-on voltage of the device to 188.6 cd cm-2 and 3 V, respectively. This study establishes Pd(II) hydrazone complexes as a new class of materials whose emissive properties can be chemically tuned and provides proof-of-concept for their use in LECs, opening up exciting new avenues for potential applications in the field of solid state lighting.

Correction: The quest for single component molecular metals within neutral transition metal complexes

Correction for ‘The quest for single component molecular metals within neutral transition metal complexes’ by Mariana F. G. Velho et al., J. Mater. Chem. C, 2021, DOI: 10.1039/d1tc01407b.

The quest for single component molecular metals within neutral transition metal complexes

The first Single Component Molecular Metals (SCMM) were reported twenty years ago. This review will address their main design, synthetic routes and physical properties.

Intermetallic Competition in the Fragmentation of Trimetallic Au-Zn-Alkali Complexes.

Cationization is a valuable tool to enable mass spectrometric studies on neutral transition-metal complexes (e.g., homogenous catalysts). However, knowledge of potential impacts on the molecular structure and catalytic reactivity induced by the cationization is indispensable to extract information about the neutral complex. In this study, we cationize a bimetallic complex [AuZnCl3 ] with alkali metal ions (M(+) ) and investigate the charged adducts [AuZnCl3 M](+) by electrospray ionization mass spectrometry (ESI-MS). Infrared multiple photon dissociation (IR-MPD) in combination with density functional theory (DFT) calculations reveal a μ(3) binding motif of all alkali ions to the three chlorido ligands. The cationization induces a reorientation of the organic backbone. Collision-induced dissociation (CID) studies reveal switches of fragmentation channels by the alkali ion and by the CID amplitude. The Li(+) and Na(+) adducts prefer the sole loss of ZnCl2 , whereas the K(+) , Rb(+) , and Cs(+) adducts preferably split off MCl2 ZnCl. Calculated energetics along the fragmentation coordinate profiles allow us to interpret the experimental findings to a level of subtle details. The Zn(2+) cation wins the competition for the nitrogen coordination sites against K(+) , Rb(+) , and Cs(+) , but it loses against Li(+) and Na(+) in a remarkable deviation from a naive hard and soft acids and bases (HSAB) concept. The computations indicate expulsion of MCl2 ZnCl rather than of MCl and ZnCl2 .

Thiazyl Trifluoride (NSF3) Adducts and Imidodifluorosulfate (F2OSN-) Derivatives of Hg(OTeF5)2.

Reactions of Hg(OTeF5)2 with excess amounts of NSF3 at 0 °C result in the formation of NSF3 adducts having the compositions [Hg(OTeF5)2·N≡SF3]∞ (1), [Hg(OTeF5)2·2N≡SF3]2 (2), and Hg3(OTeF5)6·4N≡SF3 (3). When the reactions are carried out at room temperature, oxygen/fluorine metatheses occur yielding the F2OSN- derivatives [Hg(OTeF5)(N═SOF2)·N≡SF3]∞ (4) and [Hg3(OTeF5)5(N═SOF2)·2N≡SF3]2 (5). The proposed reaction pathway leading to F2OSN- group formation occurs by nucleophilic attack by a F5TeO- group at the sulfur(VI) atom of NSF3, followed by TeF6 elimination. Tellurium hexafluoride formation was confirmed by (19)F NMR spectroscopy. The NSF3 molecules are terminally N-coordinated to mercury, whereas the F2OSN- ligands are N-bridged to two mercury atoms. The compound series was characterized by low-temperature single-crystal X-ray diffraction and low-temperature Raman spectroscopy. Several structural motifs are observed within this structurally diverse series. These include the infinite chain structures of the related compounds, 1 and 4; 2, a dimeric structure which possesses an (HgO(μ))2 ring at its core; 3, a structure based on a cage comprised of a (HgO(μ))3 ring that is capped on each face by μ(3)-oxygen bridged F5TeO- groups; and 5, a dimeric structure possessing two distorted (Hg3O2N) rings that are formally derived from 3 by replacement of a F5TeO- group by a F2OSN- group in each ring. Quantum-chemical calculations were carried out to gain insight into the bonding of the μ(3)-oxygen bridged teflate groups observed in structure 3. Compounds 1-5 represent a novel class of neutral transition metal complexes with NSF3, providing the first examples of NSF3 coordination to mercury. Compounds 4 and 5 also provide the only examples of F2OSN- derivatives of mercury that have been characterized by single-crystal X-ray diffraction.

Calculation of Ionization Potential and Electron Affinity of the Optoelectronic Material Iridium (III) Metal Complexes Containing the 2-phenyl Pyridine-Type Ligands

Solid state ionization potential and electron affinity of iridium (III) metal complexes containing the 2-phenyl pyridine-type ligands was calculated using density functional theory (DFT). It is shown that the calculated results are in well agreement with the experimental values. With this approach, it is convince to obtain solid state ionization potentials and electron affinities of a range of neutral transition metal complexes.

Transition metal complexes of 3-aryl-2-substituted 1,2-dihydroquinazolin-4(3H)-one derivatives: New class of analgesic and anti-inflammatory agents

Five-coordinate, neutral transition metal complexes of newly designed pyridine-2-ethyl-(3-carboxylideneamino)-3-(2-phenyl)-1,2-dihydroquinazolin-4(3H)-one ( L) were synthesized and characterized. The structure of ligand is confirmed by single crystal X-ray diffraction studies. The compounds were evaluated for the anti-inflammatory activity by carrageenan-induced rat paw edema model while their analgesic activity was determined by acetic acid-induced writhing test in mice wherein the transition metal complexes were found to be more active than the free ligand.

Monomeric and polymeric copper and zinc tripyrrins

Neutral transition metal complexes of different alpha,omega-dimethyltripyrrins TrpyMX with M = Cu(II) and Zn(II) have been prepared with a variety of anionic halogeno and pseudohalogeno ligands X, and have been studied with respect to coordination modes and structural distortion. Only four- and five-coordinate species have been observed throughout the series. All four-coordinate species display unstrained, but distorted tetrahedral or strained and distorted square-planar coordination environments for zinc(II) and copper(II) species, respectively, thus following the expectations from simple ligand field arguments. Five-coordinate species do not form easily and were observed either in donor solvents or in the solid as 1D coordination polymers with distorted trigonal-bipyramidal coordination and different topologies.

Cationic and Neutral Transition Metal Complexes with a Tetramethylfulvene or Trimethylallyldiene Ligand

AbstractFor Abstract see ChemInform Abstract in Full Text.

Transition Metal Complexes Bearing a Phosphenium Ligand

AbstractFor Abstract see ChemInform Abstract in Full Text.

Thioantimonate(III) anions acting as bridging ligands in neutral transition metal complexes: solvothermal synthesis and characterisation of the two novel compounds [Co(C6H18N4)]2Sb4S8 and [Co(C6H18N4)]2Sb2S5 containing [Sb4S8]4– and [Sb2S5]4– anions

The two novel thioantimonate(III) compounds [Co(C6H18N4)]2Sb4S81 and [Co(C6H18N4)]2Sb2S52 were synthesised under solvothermal conditions by reacting elemental Co, Sb and S in a 95% solution of tris(2-aminoethyl)amine (tren). Compound 1 crystallises in the monoclinic space group P21/c, a = 17.936(4) Å, b = 13.442(3) Å, c = 14.000(3) Å, β = 101.73(3)°, and compound 2 crystallises in the monoclinic space group C2/c, a = 30.157(6) Å, b = 7.720(2) Å, c = 22.875(8) Å, β = 94.68(3)°. The [Sb4S8]4− anion in compound 1 is composed of two SbS3 and two SbS4 units. The two SbS4 moieties share a common edge and each SbS4 has a common edge with a SbS3 pyramid. This interconnection leads to the formation of three Sb2S2 heterorings. The two remaining terminal S atoms of the anion are bound in a monodentate fashion to the [Co(C6H18N4)]2+ cation. The [Sb2S5]4− anion in 2 is formed by two corner linked SbS3 units. Two terminal S atoms are bound to the [Co(C6H18N4)]2+ cation in a monodentate manner. Compounds 1 and 2 are the first compounds that contain thioantimonate(III) anions acting as bridging ligands. Both compounds start to decompose at about 240 °C due to the removal of the organic ligands. In the X-ray powder patterns of the decomposition products Sb2S3, CoSbS and CoS could be identified.

Molecular design and development of single-component molecular metals

This article discusses the requirements for designing single component molecular metals, derived from the results of crystal structure analyses, electrical resistivity measurements and extended Huckel tight-binding band calculations, performed on molecular conductors composed of single-component molecules of [Ni(ptdt)2] (ptdt = propylenedithiotetrathiafulvalenedithiolate) with extended TTF-ligands. The design of π molecules with a small HOMO–LUMO gap and a TTF-like skeleton is a key step to developing single-component molecular metals. A new approach is proposed to reduce HOMO–LUMO gaps. The preparation and characterization of a single-component three-dimensional molecular metal based on an analogous neutral transition metal complex molecule, [Ni(tmdt)2] (tmdt = trimethylenetetrathiafulvalenedithiolate) are reported. The details of the procedures for its synthesis are presented. Black crystals of this compound were obtained by the electrochemical method. In the crystal, which has a triclinic unit cell containing only one molecule, the planar [Ni(tmdt)2] molecules are closely packed to form the lattice plane (02). There are intermolecular short S⋯S contacts which indicate that the system is a three-dimensional conductor. The resistivity measurements show that the system is metallic down to 0.6 K. The extended Huckel tight-binding band calculation gave three-dimensional semi-metallic Fermi surfaces. A metallic crystal was also prepared with an analogous molecule [Ni(dmdt)2] (dmdt = dimethyltetrathiafulvalenedithiolate). The formation of a single component molecular metal opens the possibilities of developing various types of unprecedented functional molecular systems such as single component molecular superconductors, ferromagnetic metals composed of single component magnetic molecules, molecular metals (or superconductors) soluble in organic solvent, etc.

Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me2CO solution of the diazole to yield complexes of the general formula: [M(Iz)2] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)2] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PriIz)2] (where M = Co, Ni, Cu, Zn; PriIz = 2-isopropylimidazolate); [M(pyIz)n] (where M = CoIII, CuII, ZnII; pyIz = 2-(2′-pyridyl)imidazolate); [M(Pz)n] (where M = CoIII, NiII, CuII, ZnII; Pz = pyrazolate); [M(ClPz)n] and [M(IPz)n] (where M = CoIII, NiII, CuII, ZnII; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me2Pz)n] (where M = CoII, CuI, ZnII; Me2Pz = 3,5-dimethylpyrazolate) and [M(BrMe2Pz)n] (where M = CoII, NiII, CuI, ZnII; BrMe2Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S=\({1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}\)) model for an infinite one-dimensional linear chain, yielding best fit values of J=−62–−65cm−1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S=\({3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}\)) model with J=−4.62–−11.7cm−1 andg = 2.06–2.49.

Neutral transition metal complexes with the tridentate ligand 4-(5-methyl-4-imidazolyl)-3-thiabutanoic acid. A series of isostructural octahedral compounds

The synthesis and spectroscopic properties of the iron, cobalt, nickel and copper complexes with the ligand 4-(5-methyl-4-imidazoly)-3-thiabutanoic acid (abbreviated Hitba) are described. The compound Co(itba) 2 ( A) crystallizes in the triclinic space group P1 with a=7.600(1), b=7.697(1), c=8.2696(5) Å, α=86.745(8),β=71.321(7), γ=69.538(12)°, V=428.5 Å 3, D x=1.65 g/cm 3 for Z=1. The compound Cu(itba) 2 ( B) crystallizes in the triclinic space group P1 with a=7.789(3), b=7.794(4), c=8.138(4) Å, α=71.448(4), β=86.905(4), η=67.805(4)°, V=432.4 Å 3, D x=1.66 g/cm 3 for Z=1. In both structures the metal ion is located on the inversion centre because of symmetry considerations. The non-hydrogens were located using Fourier methods and the structures were refined by least-squares methods to residual R w values of 0.089 ( A) and 0.050 ( B). The coordination geometry of the metal ion in both compounds A and B is octahedral with the donor atoms of the two ligands in mutual trans positions. The bond distances in the cobalt compound are significantly different from those in the Jahn-Teller distorted copper compound (CoN=2.109(7), CuN=1.986(3); CoO=2.065(6), CuO=1.988(2); CoS=2.501(2), CuS=2.7146(8)). The geometry of the cobalt ion can be described as a rather regular octahedron compared with the elongated octahedral copper structure. The obtained compounds M(itba) 2 are all isostructural according to their X-ray powder patterns and IR spectra, and all show remarkably strong ligand field spectra.

Differentiation of cationic from neutral transition metal complexes using wires as field desorption emitters

Differentiation of cationic from neutral transition metal complexes using wires as field desorption emitters

Neutral transition-metal complexes as probes for solvent structure. The spectrophotometric properties of [NN′-1-methylethylenebis(o-aminobenzylideneiminato)]cobalt(II) in some pure and mixed solvents

The visible spectrum of the rigid planar complex [NN′-1-methylethylenebis(o-aminobenzylideneiminato)]-cobalt (II), [Co(meab)], has been studied in a range of pure and mixed aqueous solvent systems under deoxygenated conditions. Beer's law is obeyed in each system up to the solubility limit. Although the visible spectrum of [Co(meab)] in water is essentially featureless, maxima at 421–435 and 522–531 nm develop on addition of methanol, ethanol, n-propanol, t-butyl alcohol, acetone, and pyridine. The close similarity of the visible spectra in pure pyridine and benzene solvents suggests that this effect is not due to discrete axial ligation of [Co(meab)] by solvent molecules, as confirmed by magnetic-moment measurements in aqueous pyridine and by the isolation of a solvate, rather than a pyridine-containing complex, from saturated solutions of [Co(meab)] in pyridine. The absorption coefficient of [Co(meab)] in binary aqueous mixtures appears to be related to the structure of the bulk solvent environment.