Luminescent heterometallic gold-copper alkynyl complexes stabilized by tridentate phosphine

The reactions between trinuclear gold complex tppmAu(3)Cl(3) (tppm = tris(diphenylphosphino)methane), arylacetylenes HC(2)C(6)H(4)X and Cu(+) under basic conditions result in formation of the heterometallic complexes [tppm(AuC(2)C(6)H(4)X)(3)Cu](+), X = H (1), COOMe (2), CN (3), OMe (4), NH(2) (5). These compounds belong to one structural motif and consist of the heterometallic {(AuC(2)C(6)H(4)X)(3)Cu} core stabilized by the tridentate phosphine. Compounds 1-5 were characterized by polynuclear NMR and IR spectroscopy, ESI-MS and single-crystal X-ray analysis. Luminescence properties of these complexes have been studied and revealed a substantial red shift of the emission maxima with the increase in the electron donicity of the alkynyl ligands substituents in the 550-680 nm range. The theoretical calculations of the electronic structures showed that variations of the substituents on the alkynyl ligands display very little effect on the molecular structural parameters but show appreciable influence on the orbital energies and luminescence characteristics of the compounds under study.     

Luminescent heteropolynuclear or multicomponent complexes with polypyridyl-functionalized alkynyl ligands

Polypyridyl-functionalized alkynes are a class of bifunctional ligands and very useful for the design of heteropolynuclear or multicomponent arrays as optoelectronic materials at the molecular level. This article focuses on reviewing the recent progress in design of luminescent heteropolynuclear or multicomponent complexes composed of photoactive discrete subunits using 2,2'-bipyridyl, 1,10-phenanthroline or 2,2':6',2'-terpyridyl functionalized alkynyl ligands with both acetylide and polypyridyl groups. The preparation, molecular fabrication, structural features, and spectroscopic and luminescent properties are summarized to elucidate the correlation of structure and photophysical properties as well as triplet energy transfer between two or more photoactive organometallic subunits.     

Luminescent heterohexanuclear complexes with platinum alkynyl and silver diphosphine as components

Reactions between the building blocks [Ag2(mu-Ph2PXPPh2)2(MeCN)2]2+ and [Pt(C[triple bond]CC6H4R-p)4]2- (R = H, CH3) afforded strongly luminescent acetylide-linked neutral heterohexanuclear complexes Pt2Ag4(mu-Ph2PNPPh2)4 (C[triple bond]CC6H4R-p)4 (R = H, 1; CH3, 2) for X = NH, but a heterotrinuclear complex cation [PtAg2(mu-PPh2CH2PPh2)2 (C[triple bond]CC6H5)2(CH3CN)2]2+ (3(2+)) for X = CH2.     

Luminescent alkynyl platinum-cadmium complexes: structural characterization of an unusual decanuclear cluster

The reaction of (NBu(4))(2)[Pt(C triple bond CPh)(4)] with Cd(ClO(4))(2).6H(2)O in a 1:1 molar ratio yields a white solid [PtCd(C triple bond CPh)(4)](n) 1 (75% yield) together with yellow crystals of a very unusual decanuclear platinum-cadmium cluster [Pt(4)Cd(6)(C triple bond CPh)(4)(mu-C triple bond CPh)(12)(mu(3)-OH)(4)] 2 in low yield. Slow diffusion of acetonic solutions of the starting materials under aerobic conditions only produces crystals of 2 which have been shown by an X-ray analysis to be composed of a big hexanuclear cation [Cd(6)(mu(3)-OH)(4)](8+) and four [Pt(C triple bond CPh)(4)](2-) anions, held together by Pt.Cd and pi.Cd acetylide interactions. On the other hand, treatment of the insoluble product 1 with 1 equiv of NBu(4)X yields tetranuclear mixed-metal soluble complexes (NBu(4))(2)[[Pt(mu-C triple bond CPh)(4)](2)(CdX)(2)] (X = Cl A, Br 3, CN 4), which contain two platinate fragments connected by two CdX units through Pt.Cd and mainly Cd.C(alpha) interactions. All complexes are strongly emissive in the solid state at room temperature.     

Synthesis, characterization, electrochemistry and luminescence studies of heterometallic gold(I)-rhenium(I) alkynyl complexes

The present work provides a brief summary review of the chemistry of luminescent gold(I) alkynyls and their ability to form heterometallic complexes. A series of luminescent heterometallic gold(I)-rhenium(I) alkynyl complexes has been synthesized and characterized. Their electrochemical and photophysical properties have been studied and their emission origins elucidated.     

On the biological properties of alkynyl phosphine gold(i) complexes

Golden times for metal-based drugs? Alkynyl triphenylphosphine gold(I) complexes display interesting biological properties and show high potential for future drug development. They are strong inhibitors of the enzyme thioredoxin reductase, trigger antiproliferative effects in tumor cells, and influence tumor cell metabolism, mitochondrial respiration, and angiogenesis in zebrafish embryos.     

Syntheses, structures, and magnetic properties of a family of tetra-, hexa-, and nonanuclear Mn/Ni heterometallic clusters

A family of Mn(III)/Ni(II) heterometallic clusters, [Mn(III)(4)Ni(II)(5)(OH)(4)(hmcH)(4)(pao)(8)Cl(2)]·5DMF (1·5DMF), [Mn(III)(3)Ni(II)(6)(N(3))(2)(pao)(10)(hmcH)(2)(OH)(4)]Br·2MeOH·9H(2)O (2·2MeOH·9H(2)O), [Mn(III)Ni(II)(5)(N(3))(4)(pao)(6)(paoH)(2)(OH)(2)](ClO(4))·MeOH·3H(2)O (3·MeOH·3H(2)O), and [Mn(III)(2)Ni(II)(2)(hmcH)(2)(pao)(4)(OMe)(2)(MeOH)(2)]·2H(2)O·6MeOH (4·2H(2)O·6MeOH) [paoH = pyridine-2-aldoxime, hmcH(3) = 2, 6-Bis(hydroxymethyl)-p-cresol], has been prepared by reactions of Mn(II) salts with [Ni(paoH)(2)Cl(2)], hmcH(3), and NEt(3) in the presence or absence of NaN(3) and characterized. Complex 1 has a Mn(III)(4)Ni(II)(5) topology which can be described as two corner-sharing [Mn(2)Ni(2)O(2)] butterfly units bridged to an outer Mn atom and a Ni atom through alkoxide groups. Complex 2 has a Mn(III)(3)Ni(II)(6) topology that is similar to that of 1 but with two corner-sharing [Mn(2)Ni(2)O(2)] units of 1 replaced with [Mn(3)NiO(2)] and [MnNi(3)O(2)] units as well as the outer Mn atom of 1 substituted by a Ni atom. 1 and 2 represent the largest 3d heterometal/oxime clusters and the biggest Mn(III)Ni(II) clusters discovered to date. Complex 3 possesses a [MnNi(5)(μ-N(3))(2)(μ-OH)(2)](9+) core, whose topology is observed for the first time in a discrete molecule. Careful examination of the structures of 1-3 indicates that the Mn/Ni ratios of the complexes are likely associated with the presence of the different coligands hmcH(2-) and/or N(3)(-). Complex 4 has a Mn(III)(2)Ni(II)(2) defective double-cubane topology. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1-4. Fitting of the obtained M/(Nμ(B)) vs H/T data gave S = 5, g = 1.94, and D = -0.38 cm(-1) for 1 and S = 3, g = 2.05, and D = -0.86 cm(-1) for 3. The ground state for 2 was determined from ac data, which indicated an S = 5 ground state. For 4, the pairwise exchange interactions were determined by fitting the susceptibility data vs T based on a 3-J model. Complex 1 exhibits out-of-phase ac susceptibility signals, indicating it may be a SMM.     

Synthesis and reactivity of alkynyl niobocene complexes

The synthesis of alkynyl containing niobocene complexes with differing auxiliary ligands is described. The niobium(III) derivatives of the general formula [Nb(η⁵-C₅H₄SiMe₃)₂(CCR)(L)] where L is either carbonyl, phosphine, phosphite, or isocyanide, were prepared by the reaction of the bis(alkynyl)magnesium reagent with the corresponding cloro-niobocene precursor. In a similar manner the niobium(V) imido compounds, of the general formula, [Nb(=NR′)(η⁵-C₅H₄R″)₂(CCR)], were prepared. The characterization of these complexes is discussed. The reactivity of the alkynyl compounds towards oxidation and protonation has been studied.     

Metal alkynyl sigma complexes: synthesis and materials

Metal alkynyl complexes hold a fascination for synthetic chemists, structural chemists, and materials scientists alike. Harnessing the unique overlap of metal and carbon orbitals is a challenge that can be overcome in many ways and hence, there are many synthetic routes toward M-C=C-bond-forming reactions that utilize a wide variety of transition-metal and alkynyl reagents. Some methods can be widely applied, while others are specific to a particular metal or compound. The linear geometry of the alkynyl unit and its pi-unsaturated character have led to metal alkynyls becoming attractive building blocks for molecular wires and polymeric organometallic materials, which can possess interesting properties, such as optical nonlinearity, luminescence, liquid crystallinity, and electrical conductivity. A unique, multifaceted approach, often combining talents from all three of the above chemical disciplines, has served as a driving force behind the intense research into the development of metal alkynyl sigma complexes, the progress of which, particularly in the last ten years, is summarized in this review.     

Syntheses, structural, electrochemical and optical studies of heterobinuclear ruthenium-osmium alkynyl complexes

The complexes trans-[Os(CCC₆H₄-4-CCR)Cl(dppe)₂] (R = SiPrⁱ₃1, H 2), trans,trans-[(dppe)₂ClOs(CCC₆H₄-4-CC)RuX(dppe)₂] (X = Cl 3, CCC₆H₄-4-CCSiPrⁱ₃4), trans-[Os(CCC₆H₄-4-CCC₆H₄-4-CCR)Cl(dppe)₂] (R = SiPrⁱ₃5, H 6), and trans,trans-[(dppe)₂ClOs(CCC₆H₄-4-CCC₆H₄-4-CC)RuCl(dppe)₂] (7) have been synthesized, and the identities of 1, 2, and 6 confirmed by single-crystal X-ray diffraction studies. Cyclic voltammetry shows that the mononuclear complexes 1, 2, 5, and 6 are oxidized at potentials within a narrow range (0.45-0.49 V), in processes centered on the osmium ethynyl neighbourhood and for simplicity assigned as Os^II/III, while the heterobinuclear complexes 3, 4, and 7 exhibit lower oxidation potentials for Os^II/III and a second oxidation process assigned in a similar fashion to Ru^II/III; the difference in potential between the Os- and Ru-localized processes decreases as the π-bridge is lengthened. UV-vis-NIR spectroelectrochemical studies on 1 and 5 reveal the appearance on oxidation of a low-energy band ascribed to chloro to metal-ethynyl charge transfer. Osmium-centered oxidation at the heterobinuclear complexes 4 and 7 results in appearance of a low-energy band, which blue-shifts and increases in intensity on further oxidation to 4²⁺ and 7²⁺.     

Synthesis, spectroscopic, and structural aspects of two trinuclear cyano-bridged heterometallic complexes

Two new cyano-bridged trinuclear heterometallic complexes [Sr₂(Phen)₄(CF₃CO₂)(H₂O)₃Fe(CN)₆]·2H₂O (1) [Ca₂(Phen)₄(CF₃CO₂)(H₂O)Co(CN)₆]·2H₂O (2) (where Phen=1,10-phenanthroline) have been synthesized and their crystal structures have been determined. The structure of complex (1) features a central [Fe(CN)₆]³⁻ unit that links a monocation, [Sr(Phen)₂(OH₂)(OOCCF₃)]⁺ and a dication, [Sr(Phen)₂(OH₂)₂]²⁺ via two trans cyanide bridges. The complex (2) features a central [Co(CN)₆]³⁻ unit that links two monocations of [Ca(Phen)₂(OH₂)(OOCCF₃)]⁺ (the positions of the trifluoro acetate and water molecules are disordered over two positions) via two trans cyanide bridges. Each metal atom is seven coordinated and achieves pentagonal bipyramidal geometry. Two cocrystallized water molecules are present in both the complexes. The presence of an extensive network of hydrogen bonding imparts the overall stability to both the systems.     

Nickel alkynyl and allenylidene complexes: Synthesis and properties

Copper-catalyzed reaction of [Cp(PPh₃)NiCl] with the terminal alkynes H-CC-C(O)R (R = O-Menthyl, NMe₂, Ph) yields the alkynyl complexes [Cp(PPh₃)Ni-CC-C(O)R]. Subsequent O-methylation with either [Me₃O]BF₄ or MeSO₃CF₃ affords cationic allenylidene complexes, [Cp(PPh₃)NiCCC(OMe)R]⁺X¯ (X = BF₄, SO₃CF₃). N-Alkylation of Cp(PPh₃)Ni-pyridylethynyl complexes likewise gives cationic allenylidene complexes. [Cp(PPh₃)Ni-CC-C(CH)₄N] adds BF₃ at nitrogen. Modification of the ligand sphere in these nickel allenylidene complexes is possible by replacing PPh₃ by PMe₃ in the alkynyl complex precursors. The first allenylidene(carbene)nickel cation, [Cp(SIMes)NCCC(OMe)NMe₂]⁺, is accessible by successive reaction of [Cp(SIMes)NiCl] with H-CC-C(O)NMe₂ and [Me₃O]BF₄. By the analogous sequence an allenylidene complex containing the chelating (diphenylphosphanyl)ethylcyclopentadienyl ligand can be prepared. DFT Calculations were carried out on the allenylidene complex cation [Cp(PPh₃)NiCCC(OMe)NMe₂]⁺ and on its precursor, the alkynyl complex [Cp(PPh₃)Ni-CC-C(O)NMe₂]. Based on the spectroscopic data and a X-ray structure analysis the bonding in the new nickel allenylidene complexes is best represented by several resonance forms, an alkynyl resonance form considerably contributing to the overall bond.     

Synthesis of luminescent heterometallic bis-lanthanide complexes via selective, sequential metallation

A modular synthetic method for the differential incorporation of two lanthanide ions into a single molecular scaffold is reported; the mixed bimetallic Tb/Eu complex displays an interesting solvent polarity-dependent ratiometric luminescence.     

UO22+-polycarboxylate heterometallic complexes: structure,spectra, and photocatalytic properties

[Cu₂(UO₂)₄(suc)₄(pac)₄] (1), [(Cu(H₂O)₂)(4,4′-bipy)₂][(UO₂)₂(H₂O)₂(Hca)₂]·3H₂O (2), and [(Cu(H₂O)₂)(UO₂)(bta)]·4H₂O (3) were synthesized by the reaction of succinic acid and 3-pyridinecarboxylic acid, citric acid and 4,4′-bipyridine, or 1,2,4,5-benzenetetracarboxylic acid ligands with Cu(NO₃)₂·3H₂O and UO₂(CH₃COO)₂·2H₂O. The complexes were characterized by IR and UV–vis spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction, and photoluminescence spectroscopy. Photocatalytic activities of the complexes were also investigated.     

Luminescent,optical, magnetic and metamaterial behavior of cerium complexes

The complexes of cerium with nitrogen, oxygen and sulfur donor ligands were prepared by conventional method. These newly synthesized complexes were characterized by FTIR, UV–Vis, DART Mass, TGA, PXRD, SEM and TEM techniques. The magnetic studies were carried out by the vibrating sample magnetometer. The optical constants were measured by absorption and reflection spectra as a function of wavelength. The concentration dependence of refractive index and absorption was observed by the experimental method, which reveals that these parameters are affected by change in concentration. The optical band gap obtained from Tauc-plot indicates its probability to be a good semiconductor. The luminescence behavior of these cerium complexes was observed by the absorption and emission spectra and the emission life time was calculated by their life time spectra.     

Crystallographic and structural characterization of heterometallic platinum complexes Part VI. Heterohexanuclear complexes

This review classifies and analyzes heterohexanuclear platinum clusters into seven types of metal combinations:Pt₅M, Pt₄M₂, Pt₃M₃, Pt₂M₄, PtM₅, Pt₂M₃M′, and Pt₂M₂M₂′. The crystals of these clusters generally belong to six crystal classes: monoclinic, triclinic, orthorhombic, tetragonal, trigonal and cubic. Among the wide range of stereochemistry adopted by these clusters, octahedral and capped square-pyramidal are the most common. Although platinum is classified as a soft metal atom, it bonds to a variety of soft, borderline and hard metals. Nineteen different heterometal ions are involved in hexanuclear platinum clusters. The shortest Pt-M bond distance in the case of M being a non-transition element is 2.395(4) Å for germanium and for M being a transition metal ion it is 2.402(2) Å for Cobalt. The shortest Pt-Pt bond distance observed in these clusters is 2.532 Å. Several relationships between the structural parameters are identified and discussed. Some clusters exist in two isomeric forms and some show crystallographically independent molecules within the same crystal. Such isomers and independent molecules are examples of distortion isomerism.      

Crystallographic and structural characterization of heterometallic platinum complexes Part V. Heteropentanuclear complexes

This review classifies and analyzes over eighty heteropentanuclear Pt complexes. There are eight types of metal combinations: Pt₄M, Pt₃M₂, Pt₂M₃, PtM₄, Pt₃MM′, Pt₂M₂M′, PtM₂M′₂ and PtM₃M′. The five metal atoms are in a wide variety of arrangements: trigonal-bipyramidal (most common), square-pyramidal, spike-triangular, butterfly, cubane, linear and one unique. Platinum bonds to a variety of triad partner metal atoms, soft, through borderline to hard. The shortest Pt-M bond distances for non-transition and transition M are 2.406(4) Å (M = Ge) and 2.30(1) Å (M = Co). The shortest Pt-Pt bond distance is 2.580(1) Å. Several relationships between the structural parameters were found and are discussed. Several complexes exist in two isomeric forms and others contain two crystallographically independent molecules. Both the isomers as well as independent molecules are examples of distortion isomerism.      

Spectral,magnetic and thermal studies on homometallic and heterometallic complexes of piperanol thiosemicarbazone

Piperanol thiosemicarbazone (HL) has been interacted with Ag⁺, Co(II), Ni(II) or Cu(II) binary to produce [Ag(HL)]EtOH · NO₃, [Ag₂(L)(H₂O)₂]NO₃, [Co(L)₃], [Cu(L)(H₂O)₃(OAc)]H₂O or [Ni(L)₂] and template with Ag⁺ to form [Cu₂Ag₂(L)₂(OH)₂(H₂O)₄]NO₃ and [NiAg(L)₂(H₂O)₂]NO₃. The prepared complexes are characterized by microanalysis, thermal, magnetic and spectral (IR, ¹H NMR, ESR and electronic) studies. Ag⁺ plays an important role in the complex formation. The variation in coordination may be due to the presence of two different metal ions and the preparation conditions. The outside nitrate is investigated by IR spectra. The outer sphere solvents are detected by IR and thermal analysis. Ni(II) complexes are found diamagnetic having a square-planar geometry. Cu(II) is reduced by the ligand to Cu(I). The cobalt complex is found diamagnetic confirming an air oxidation of Co(II) to Co(III) having a low spin octahedral geometry. The ligand and its metal complexes are found reducing agents which decolorized KMnO₄ solution in 2N H₂SO₄. CoNS and NiNS are the residual parts in the thermal decomposition of [Co(L)₃] and [Ni(L)₂].