Octupolar trisporphyrin conjugates exhibiting strong two-photon absorption

We report octupolar trisporphyrin conjugates, derived from the symmetrical functionalization of a triphenylamine core with three ethynylporphyrin wings, exhibiting largely enhanced two-photon absorption (TPA) compared to the porphyrin monomers. Octupolar trisporphyrin conjugate tris-H₂P was synthesized by the Pd(0)-catalyzed Sonogashira cross-coupling reaction of tris(4-iodophenyl)amine with 5,10,15-tri-(p-tolyl)-20-ethynylporphyrin, and fully characterized by various spectroscopic methods and elemental analysis. The optimized geometry of tris-H₂P obtained by semi-empirical AM1 calculations reveals that tris-H₂P adopts a propeller-shaped structure. Our photophysical studies strongly manifest that the trisporphyrin conjugates are promising octupolar fluorophores with effective π-conjugation over the porphyrin wings through the octupolar core. The trisporphyrin conjugates exhibit much larger TPA cross-section values in comparison with the monomers; the TPA cross-section σ⁽²⁾ value of tris-ZnP (11,800 GM) exceeds that of mono-ZnP (630 GM) by about 20 times.     

2,2′-Bipyrimidine transition metal complexes: Synthesis, reaction chemistry and solid state structures

2,2′-Bipyrimidine metal complexes with Ti, Mo, Fe, Ru, Pt, Ag, and Cu transition metal atoms have been synthesized and structurally characterized. These molecules were prepared by following synthesis methodologies. The reaction of 2,2′-bipyrimidine (1; bipym) with {[Ti](μ-σ,π-CCSiMe₃)₂}AgOTf ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti, OTf = OSO₂CF₃) (2) in a 1:1 molar ratio gave [{[Ti](μ-σ,π-CCSiMe₃)₂}Ag(bipym)]OTf (3) which on further treatment with another equivalent of 2 produced [({[Ti](μ-σ,π-CCSiMe₃)₂}Ag)₂(μ-1,2,3,4-bipym)](OTf)₂ (4). As consequence thereof, the coordination number of Ag(I) was changed from 3 to 4. A platinum-bipym complex with two acetylide substituents was accessible by the gradual reaction of 1 with K₂[PtCl₄] (5) and two equivalents of HCCR (7a, R = SiMe₃; 7b, R = Fc; 7c, R = Rc; Fc = (η⁵-C₅H₄)(η⁵-C₅H₅)Fe; Rc = (η⁵-C₅H₄)(η⁵-C₅H₅)Ru) in di-iso-propylamine and in presence of [CuI]. Originating from cis-[(bipym)Pt(CCR)₂] (8a, R = SiMe₃; 8b, R = Fc; 8c, R = Rc) diverse multinuclear complexes with two, three or four different transition metals could be obtained. These are: [((CO)₄Mo)(μ-1,2,3,4-bipym)Pt(CCFc)₂] (10), [(AgClO₄)(μ-1,2,3,4-bipym){[Pt(μ-σ,π-CCFc)₂]AgOClO₃}] (12), [(McCC)₂Pt(μ-1,2,3,4-bipym)({[Ti](μ-σ,π-CCSiMe₃)₂}M)]X (15a, Mc = Fc, M = Cu, X = PF₆; 15b, Mc = Rc, M = Cu, X = PF₆; 15c, Mc = Fc, M = Ag, X = ClO₄), and [(McCC)₂Pt(μ-1,2,3,4-bipym)PtCl₂] (17). Like other organometallic Pt-Ag tweezer complexes, compound 12 decomposed to give FcCC-CCFc (13). During prolonged stirring of 15a and 15b, respectively, [(McCC)₂Pt(μ-1,2,3,4-bipym)({[Ti](μ-σ,π-CCSiMe₃)(μ-σ,π-CCH)}M)]X (15′a, M = Cu, X = PF₆; 15′b, M = Cu, X = PF₆) was formed.The structures of 8b, 8c, 15a′, and 15b′ in the solid state are reported. All complexes exhibit the anticipated planar dinuclear Pt-M structure (M = Pt, Cu, Ag) with the 2,2′-bipyrimidine unit in a μ-1,2,3,4-bridging mode.Electrochemical investigations were carried out with 8a, 8b, and 8c and show that no significant influence of R on the bipym redox potentials exists. The typical redox behavior for the bipym, ferrocene, ruthenocene units and platinum were observed.     

Fluorene as the π-spacer for new two-photon absorption chromophores

We report herein the design and synthesis of two new quadrupolar D-π-A-π-D chromophores containing diphenyl amine and dicyanobenzene or 2,1,3-benzothiadiazole as electron donor (D) and acceptor (A), respectively, which are bridged by fluorene linkage (π). The introduction of coplanar fluorenes is highly beneficial for the enhancement of two-photon absorption (TPA), where 1b displays a TPA cross section (σ₂) of up to 1975±207 GM.     

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Four cyclometalated Pt(II) complexes, i.e., [(L²)PtCl] (1b), [(L³)PtCl] (1c), [(L²)PtCCC₆H₅] (2b) and [(L³)PtCCC₆H₅] (2c) (HL² = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2′-bipyridine and HL³ = 4-[p-(N,N′-dibutyl-N′-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2′-bipyridine), have been synthesized and verified by ¹H NMR, ¹³C NMR and X-ray crystallography. Unlike previously reported complexes [(L¹)PtCl] (1a) and [(L¹)PtCCC₆H₅] (2a) (HL¹ = 4,6-diphenyl-2,2′-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer (¹MLCT) (dπ(Pt) → π^∗(L)) transitions (ε ∼ 2 × 10⁴ dm³ mol⁻¹ cm⁻¹) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c. Meanwhile, with the introduction of electron-donating arylamino groups in the ligands of 1a and 2a, complexes 1b and 2b display stronger phosphorescence in CH₂Cl₂ solutions at room temperature with bathochromically shifted emission maxima at 595 and 600 nm, relatively higher quantum yields of 0.11 and 0.26, and much longer lifetimes of 8.4 and 4.5 μs, respectively. An electrochromic film of 1b-based polymer was obtained on Pt or ITO electrode surface, which suggests an efficient oxidative polymerization behavior. An orange multilayer organic light-emitting diode with 1b as phosphorescent dopant was fabricated, achieving a maximum current efficiency of 11.3 cd A⁻¹ and a maximum external efficiency of 5.7%. The luminescent properties of complexes 1c and 2c are dependent on pH value and solvent polarity, which is attributed to the protonation of arylamino units in the C^N^N cyclometalating ligands.     

Heterotrimetallic and heterotetrametallic transition metal complexes

The synthesis of the ruthenium σ-acetylides (η⁵-C₅H₅)L₂Ru-CC-bipy (4a, L = PPh₃; 4b, L₂ = dppf; bipy = 2,2′-bipyridine-5-yl; dppf = 1,1′-bis(diphenylphosphino)ferrocene) is possible by the reaction of [(η⁵-C₅H₅)L₂RuCl] (1) with 5-ethynyl-2,2′-bipyridine (2a) in the presence of NH₄PF₆ followed by deprotonation with DBU. Heterobimetallic Fc-CC-NCN-Pt-CC-R (10a, R = bipy; 10b, R = C₅H₄N-4; Fc = (η⁵-C₅H₅)(η⁵-C₅H₄)Fe; NCN = [1,4-C₆H₂(CH₂NMe₂)₂-2,6]⁻) is accessible by the metathesis of Fc-CC-NCN-PtCl (9) with lithium acetylides LiCC-R (2a, R = bipy; 2b, R = C₅H₄N-4).The complexation behavior of 4a and 4b was investigated.Treatment of these molecules with [MnBr(CO)₅] (13) and {[Ti](μ-σ,π-CCSiMe₃)₂}MX (15a, MX = Cu(NCMe)PF₆; 15b, MX = Cu(NCMe)BF₄; 16, MX = AgOClO₃; [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti), respectively, gave the heteromultimetallic transition metal complexes (η⁵- C₅H₅)L₂Ru-CC-bipy[Mn(CO)₃Br] (14a: L = PPh₃; 14b: L₂ = dppf) and [(η⁵-C₅H₅)L₂Ru-CC-bipy{[Ti](μ-σ,π-CCSiMe₃)₂}M]X (17a: L = PPh₃, M = Cu, X = BF₄; 17b: L₂ = dppf, M = Cu, X = PF₆; 18a: L = PPh₃, M = Ag, X = ClO₄; 18b: L₂ = dppf, M = Ag, X = ClO₄) in which the appropriate transition metals are bridged by carbon-rich connectivities.The solid-state structures of 4b, 10b, 12 and 17b are reported. The main structural feature of 10b is the square-planar-surrounded platinum(II) ion and its linear arrangement. In complex 12 the N-atom of the pendant pyridine unit coordinates to a [mer,trans-(NN′N)RuCl₂] (NN′N = 2,6-bis-[(dimethylamino)methyl]pyridine) complex fragment, resulting in a distorted octahedral environment at the Ru(II) centre. In 4b a 1,1′-bis(diphenylphosphino)ferrocene building block is coordinated to a cyclopentadienylruthenium-σ-acetylide fragment. Heterotetrametallic 17b contains a (η⁵-C₅H₅)(dppf)Ru-CC-bipy unit, the bipyridine entity of which is chelate-bonded to [{[Ti](μ-σ,π-CCSiMe₃)₂}Cu]⁺. Within this arrangement copper(I) is tetra-coordinated and hence, possesses a pseudo-tetrahedral coordination sphere.The electrochemical behavior of 4, 10b, 12, 17 and 18 is discussed. As typical for these molecules, reversible oxidation processes are found for the iron(II) and ruthenium(II) ions. The attachment of copper(I) or silver(I) building blocks at the bipyridine moiety as given in complexes 17 and 18 complicates the oxidation of ruthenium and consequently the reduction of the group-11 metals is made more difficult, indicating an interaction over the organic bridging units.The above described complexes add to the so far only less investigated class of compounds of heteromultimetallic carbon-rich transition metal compounds.     

Heterometallic Pt-Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](μ-σ,π-CCPh)₂}AgX (3a, [Pt] = (bipy′)Pt, X = FBF₃; 3b, [Pt] = (bipy′)Pt, X = FPF₅; 3c, [Pt] = (bipy)Pt, X = OClO₃; 3d, [Pt] = (bipy′)Pt, X = BPh₄; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](CCPh)₂ (1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF₄; 2b, X = PF₆; 2c, X = ClO₄; 2d, X = BPh₄). In 3a-3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](μ-CCPh)₂}₂Ag]X (8a, [Pt] = (bipy)Pt, X = BF₄; 8b, [Pt] = (bipy′)Pt, X = PF₆; 8c, [Pt] = (bipy)Pt, X = BF₄) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](CCPh)₂ units. Within this structural arrangement the phenyl acetylides of individual [Pt](CCPh)₂ entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt-Ag 2.8965(3) Å). The respective silver carbon distances Ag-C_α (2.548(7), 2.447(7) Å) and Ag-C_β (3.042(7), 2.799(8) Å)(PtC_αC_βPh) confirm this structural motif.Complexes 8a-8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-CCPh)₂}₂Ag]X (9a, [Pt] = (bipy)Pt, X = BF₄; 9b, [Pt] = (bipy′)Pt, X = PF₆; 9c, [Pt] = (bipy)Pt, X = ClO₄). In the latter molecules the organometallic cation [{cis-[Pt](μ-σ,π- CCPh)₂}₂Ag]⁺ is set-up by two nearly orthogonal positioned [Pt](CCPh)₂ entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhCC units are η²-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.     

Synthesis,spectral, thermal and BVS investigations on ZnS4N^N/N coordination environment: Single crystal X-ray structures of bis(dibenzyldithiocarbamato)(N^N)Zinc(II) complexes (N^N = 1,10-phenanthroline,tetramethylethylenediamine and 4,4′-bipyridine)

The current paper describes the synthesis and spectral investigations on the adducts of [Zn(dbzdtc)₂] (1) with 1,10-phen (2), tmed (3), 2,2′-bipy (4) and 4,4′-bipy (5) (where, dbzdtc = dibenzyldithiocarbamate anion, 1,10-phen = 1,10-phenanthroline, tmed = tetramethylethylenediamine, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridne) and single crystal X-ray structures of [Zn(dbzdtc)₂(1,10-phen)] (2) and [Zn(dbzdtc)₂(tmed)] (3) and [Zn(dbzdtc)₂(4,4′-bipy)] (5). ¹H and ¹³C NMR spectra of 1,10-phen, tmed, 2,2′-bipy and 4,4′-bipy adducts were recorded. ¹H NMR spectra of the complexes show the drift of electrons from the nitrogen of the substituents forcing a high electron density towards sulfur via the thioureide π-system. In the ¹³C NMR spectra, the most important thioureide (N¹³CS₂) carbon signals are observed in the region: 206–210 ppm. Fluorescence spectra of complexes (2) and (4) show intense fluorescence due to the presence of rigid conjugate systems such as 1,10-phenanthroline and 2,2′-bipyridine. The observed fluorescence maxima for complexes with an MS₄N₂ chromophore in the visible region are assigned to the metal-to-ligand charge transfer (MLCT) processes. Single crystal X-ray structural analysis of (2) and (3) showed that the zinc atom is in a distorted octahedral environment. Bond Valence Sum was found to be equivalent to 1.865 for (2), 1.681 for (3) supporting the correctness of the determined structure. BVS of (3) deviates from the formal oxidation number of zinc due to the non-aromatic, sterically hindering tetramethyl bonding end of tmed. Thermal studies on the compounds show the formation of Zn(NCS)₂ as an intermediate during the decay.     

Synthesis of bitetrathiafulvalenes with FeCl3-mediated homo-coupling of tetrathiafulvalenylmagnesium bromide and formation of nanostructures from bitetrathiafulvalenes having long alkylthio chains

The FeCl₃-mediated homo-coupling of 4,5-bis(alkylthio)-4′-tetrathiafulvalenylmagnesium bromide 5 produced the corresponding bitetrathiafulvalene derivatives 2a-d in moderate yields (25-51%). Bitetrathiafulvalenes 2c and 2d having long alkylthio chains formed nanostructures and showed bulk electric conductivities (σ_rt = 2.6 − 8.0 × 10⁻⁵ S cm⁻¹) in the neutral state owing to the fastener effect. Interestingly, the nanofiber of tetrakis(dodecylthio)bitetrathiafulvalene 2d exhibited a p-type semiconductivity as detected by AFM.     

Syntheses and catalytic activities of Group 4 metal complexes derived from C(cage)-appended cyclohexyloxocarborane trianion

The reaction of Li[closo-1-Me-1,2-C₂B₁₀H₁₀] with cyclohexene oxide produced closo-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C₂B₁₀H₁₀ (1) in 86% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol gave the corresponding cage-opened potassium salt of the carborane anion, [nido-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C₂B₉H₁₀]⁻ (2) in 82% yield. Deprotonation of (2) with two equivalents of n-butyllithium in THF at −78 °C, followed by its further reaction with anhydrous MCl₄ · 2THF (M = Ti, Zr) produced the corresponding d⁰-half-sandwich metallacarboranes, closo-1-M(Cl)-2-Me-3-(2′-σ-O-cyclohexyl)-η⁵-2,3-C₂B₉H₉ (3 M = Zr; 4 M = Ti), in 59% and 51% yields, respectively. Reaction of Li[closo-1,2-C₂B₁₀H₁₁] with Merrifield’s peptide resin (1%) in refluxing THF gave the ortho-carborane-functionalized polymer (5) in 88% yield. The corresponding closo-1-polystyryl-2-(2′-hydroxycyclohexyl)-1,2-C₂B₁₀H₁₀ (6) was produced in 94% yield by refluxing a mixture of the lithium salt of (5) and cyclohexene oxide in THF for 2 days. Compound (6) was decapitated, deprotonated and then reacted with ZrCl₄ · 2THF to produce a polymer-supported d⁰-half-sandwich metallacarborane closo-1-Zr(Cl)-2-polystyryl-3-(2′-σ-O-cyclohexyl)-η⁵-2,3-C₂B₉H₉ (7) in 41% yield. Compounds (3) and (7), in the presence of MMAO-7 (13% ISOPAR-E), were found to catalyze the polymerization of ethylene and vinyl chloride in toluene to give high molecular weight PE (9.4 × 10³ (M_w/M_n = 1.8)) and PVC (2.1 × 10³ (M_w/M_n = 1.6)), respectively.     

Steric and electronic effects in stabilizing allyl-palladium complexes of “P-N-P” ligands, X2PN(Me)PX2 (X = OC6H5 or OC6H3Me2-2,6)

The chemistry of η³-allyl palladium complexes of the diphosphazane ligands, X₂PN(Me)PX₂ [X = OC₆H₅ (1) or OC₆H₃Me₂-2,6 (2)] has been investigated.The reactions of the phenoxy derivative, (PhO)₂PN(Me)P(OPh)₂ with [Pd(η³-1,3-R′,R″-C₃H₃)(μ-Cl)]₂ (R′ = R″ = H or Me; R′ = H, R″ = Me) give exclusively the palladium dimer, [Pd₂{μ-(PhO)₂PN(Me)P(OPh)₂}₂Cl₂] (3); however, the analogous reaction with [Pd(η³-1,3-R′,R″-C₃H₃)(μ-Cl)]₂ (R′ = R″ = Ph) gives the palladium dimer and the allyl palladium complex [Pd(η³-1,3-R′,R″-C₃H₃)(1)](PF₆) (R′ = R″ = Ph) (4). On the other hand, the 2,6-dimethylphenoxy substituted derivative 2 reacts with (allyl) palladium chloro dimers to give stable allyl palladium complexes, [Pd(η³-1,3-R′,R″-C₃H₃)(2)](PF₆) [R′ = R″ = H (5), Me (7) or Ph (8); R′ = H, R″ = Me (6)].Detailed NMR studies reveal that the complexes 6 and 7 exist as a mixture of isomers in solution; the relatively less favourable isomer, anti-[Pd(η³-1-Me-C₃H₄)(2)](PF₆) (6b) and syn/anti-[Pd(η³-1,3-Me₂-C₃H₃)(2)](PF₆) (7b) are present to the extent of 25% and 40%, respectively. This result can be explained on the basis of the steric congestion around the donor phosphorus atoms in 2. The structures of four complexes (4, 5, 7a and 8) have been determined by X-ray crystallography; only one isomer is observed in the solid state in each case.     

Oligothiophene-2-yl-vinyl bridged mono- and binuclear ruthenium(II) tris-bipyridine complexes: Synthesis, photophysics, electrochemistry and electrogenerated chemiluminescence

A series of mono- and binuclear ruthenium(II) tris-bipyridine complexes tethered to oligothienylenevinylenes have been synthesized and characterized by ¹H NMR, ¹³C NMR and TOF-MS spectrometry. Photophysics, electrochemistry and electrogenerated chemiluminescence (ECL) properties of these complexes are investigated. The electronic absorption spectra of the mononuclear ruthenium complexes show a significant red shift both at MLCT (metal-to-ligand charge transfer) and π-π^∗ transitions of oligothienylenevinylenes with increase in the number of thiophenyl-2-yl-vinyl unit. For the binuclear complexes these two absorption bands are overlapped. All the metal complexes have very weak emission compared to that of the reference complex Ru(bpy)²⁺₃. The first reduction potentials of all mononuclear ruthenium complexes are less negative than that of Ru(bpy)²⁺₃, due to the moderate electron-withdrawing effect of oligothienylenevinylenes. For binuclear ruthenium complexes, only one Ru(II/III) oxidation peak (E_1/2 = 0.96 V vs. Ag/Ag⁺) was observed, suggesting a weak interaction between two metal centers. Three successive reduction processes of bipyridine ligands are similar among all ruthenium complexes except for RuTRu, which has a very sharp peak owing to the accumulation of neutral product on the electrode surface. All these ruthenium complexes exhibited different ECL property in CH₃CN solution without any additional reductant or oxidant. For three mononuclear ruthenium complexes, the ECL intensity strengthens with increase in the number of thiophene-2-yl-vinyl unit. However, the ECL efficiency dramatically decreased in the binuclear ruthenium complexes. The ECL efficiencies of all the reported complexes do not exceed that of Ru(bpy)²⁺₃, where the ECL efficiency decreases in the order of RuTRu > Ru3T > Ru2T > RuT > Ru2TRu (RuT,bis-2,2′-bipyridyl-(4-methyl-4′-(2-thienylethenyl)-2,2′-bipyridine) ruthenium dihexafluorophosphate; Ru2T, bis-2,2′-bipyridyl-(4-methyl-4′-{(E)-2-[5-((E)-2-thienylethenyl)-thienylethenyl]}-2,2′-bipyridine) ruthenium dihexafluorophosphate; Ru3T, bis-2,2′-bipyridyl-(4-methyl-4′-{(E)-2-{(E)-2-[5-((E)-2-thienylethenyl)-thienylethenyl]}}-2,2′-bipyridine) ruthenium dihexafluorophosphate; RuTRu, bis-2,2′-bipyridyl-ruthenium-bis-[2-((E)-4′-methyl-2, 2′-bipyridinyl-4)-ethenyl]-thienyl-bis-2,2′-bipyridyl-ruthenium tetrahexafluorophosphate; Ru2TRu, bis-2,2′-bipyridyl-ruthenium-(E)-1,2-bis-{2-[2-((E)-4′-methyl-2,2′-bipyridinyl-4)-ethenyl]-thienyl}-ethenyl-bis-2,2′-bipyridyl-ruthenium tetrahexafluorophosphate).     

Pd(0) and Pd(II) derivatives with heteroannularly bridged chiral ferrocenyl diphosphine ligands - A stereochemical analysis

The ligands (S_c, S_p)-1-diphenylphosphino-2,1′-(1-dicyclohexylphosphinopropanediyl)ferrocene, (S_c, S_p)-PP^CyPF, and (S_c, S_p)-1-diphenylphosphino-2,1′-(1-diphenylphosphinopropanediyl)ferrocene, (S_c, S_p)-PP^PhPF, have been used in the synthesis of the new Pd(0) and Pd(II) derivatives [Pd(PP^CyPF)(DMFU)] (1) (DMFU = dimethylfumarate), [Pd(PP^CyPF)(MA)] (2) (MA = maleic anhydride), [Pd(η³-2-Me-C₃H₄)(PP)]OTf (PP = PP^CyPF, 3; PP^PhPF, 4) (OTf = triflate), [PdRR′(PP)] (R = Me, R′ = Cl, PP = PP^CyPF, 5, PP^PhPF, 6; R = R′ = Me, PP = PP^CyPF, 7, PP^PhPF, 8; R = R′ = C₆F₅, PP = PP^CyPF, 9, PP^PhPF, 10). The molecular structure of 7 has been determined by X-ray diffraction. In the cases of complexes 1-4 two isomers are formed depending on the orientation of the ancillary ligand with respect to the ferrocenyl core. The stereochemistry of these complexes has been determined. In complex 6 the two possible isomers are obtained whereas in complex 5 the derivative with the Me group trans to PPh₂ is selectively formed. Restricted rotation of the pentafluorophenyl groups with respect to the Pd-C bond has been found in 9 and 10. In all derivatives the conformation of the ferrocenyl ligand is the same as that seen by X-ray diffraction and deduced from NMR data.     

Synthesis,crystal structure and some properties of new perrhenate and pertechnetate complexes of Nd and Am with 2,6-bis(tetramethylfurano)-1,2,4-triazin-3-yl)-pyridine,tris(2-pyridylmethyl)amine and N,N′-tetraethylmalonamide

The coordination complexes of trivalent f-element pertechnetates and perrhenates with some N-donor ligands were determined by using X-ray structural analysis: Nd³⁺ perrhenate with 2,6-bis(tetramethylfurano)-1,2,4-triazin-3-yl)-pyridine ([Nd(FBTP)₃ReO₄](ReO₄)₂ · 2H₂O (I)), tris(2-pyridylmethyl)amine ([Nd(TPA)(ReO₄)₃] (II)) and N,N′-tetraethylmalonamide ([Nd(TEMA)₄](ReO₄)₃ (III)). The coordination number of Nd is 10 in I, 9 in II and 8 in III. The complexes of Nd³⁺ pertechnetate and Am³⁺ pertechnetate with TPA have been also synthesized (Nd(TPA)(TcO₄)₃ (IV) and Am(TPA)(TcO₄)₃ (V)). The structure II does not change on replacement of perrhenate by pertechnetate and neodymium by americium.     

Cyclopentadienylaluminum donor-acceptor complexes - Molecular and supramolecular structure

Lewis acid-base complexes of cyclopentadienylaluminum derivatives Me_xCp_3−x Al (x = 0-2) and trimethylaluminum with selected aromatic amines (L): dmap = 4-dimethylaminopyridine, py-Me = 4-methylpyridyne, were synthesized and characterized by ¹H, ¹³C, ²⁷Al NMR: Cp₃Al · dmap (1), Cp₃Al · py-Me (2), MeCp₂Al · dmap (3), MeCp₂Al · py-Me (4), Me₂CpAl · dmap (5), Me₂CpAl · py-Me (6), Me₃Al · py-Me (7). ¹H NMR studies of 3-6 revealed small amounts of the ligand redistribution products. The crystal structures of 1, 2 and 3 were determined by single X-ray diffraction studies. The compounds 1, 2 and 3 are monomeric with Cp ligands bonded to the aluminum center in η¹(σ), η¹(π) manner. The change of Cp-Al bond character from η¹(π) to η¹(σ) was found to reasonable correlate with the aromaticity of Cp⁻ ligand described by HOMA index. Analysis of close intra- and intermolecular contacts showed presence of CH?π interactions leading to the formation of 2-D supramolecular networks. It was found that these interactions impact on the coordination sphere of aluminum and the conformation of Cp ring.     

Syntheses and characterization of η-cyclopentadienyl and η-indenyl ruthenium(II) complexes of arylazoimidazoles: The molecular structure of the complex [(η-C5H5)Ru(PPh3)(C6H5-NN-C3H3N2)]

The complex [(η⁵-C₅H₅)Ru(PPh₃)₂Cl] (1) reacts with several arylazoimidazole (RaaiR′) ligands, viz., 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et), gave complexes of the type [(η⁵-C₅H₅)Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (2), R = H, R′ = CH₃ (3), R = H, R′ = C₂H₅ (4), R = CH₃, R′ = H (5), R, R′ = CH₃ (6), R = CH₃, R′ = C₂H₅ (7)}. The complex [(η⁵-C₉H₇)Ru(PPh₃)₂(CH₃CN)]⁺ (8) undergoes reactions with a series of N,N-donor azo ligands in methanol yielding complexes of the type [(η⁵-C₉H₇) Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (9), R = H, R′ = CH₃ (10), R = CH₃, R′ = H (11), R = CH₃, R′ = C₂H₅ (12)}, respectively. These complexes were characterized by FT IR and FT NMR spectroscopy as well as by analytical data. The molecular structure of the complex [(η⁵-C₅H₅)Ru(PPh₃)(C₆H₅-NN-C₃H₃N₂)]⁺ (2) was established by single crystal X-ray diffraction study.     

A novel series of iridium complexes with alkenylquinoline ligands: Theoretical study on electronic structure and spectroscopic property

The ground and the lowest-lying triplet excited state geometries, electronic structures, and spectroscopic properties of a novel series of neutral iridium(III) complexes with cyclometalated alkenylquinoline ligands [(C^N)₂Ir(acac)] (acac = acetoylacetonate; C^N = 2-[(E)-2-phenyl-1-ethenyl]pyridine (pep) 1; 2-[(E)-2-phenyl-1-ethenyl]quinoline (peq) 2; 1-[(E)-2-phenyl-1-ethenyl]isoquinoline (peiq) 3; 2-[(E)-1-propenyl]pyridine (pp) 4; 2-[(E)-1-fluoro-1-ethenyl]pyridine (fpp) 5) were investigated by DFT and CIS methods. The highest occupied molecular orbital is composed of d(Ir) and π(C^N) orbital, while the lowest unoccupied molecular orbital is dominantly localized on C^N ligand. Under the TD-DFT with PCM model level, the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized ground and triplet excited state geometries, respectively. The calculated lowest-lying absorptions at 437 nm (1), 481 nm (2), 487 nm (3), 422 nm (4), and 389 nm (5) are attributed to a {[d_x²-y²(Ir) + d_xz(Ir) + π(C^N)] → [π∗(C^N)]} transition with metal-to-ligand/intra-ligand charge transfer (MLCT/ILCT) characters, and the calculated phosphorescence at 582 nm (1), 607 nm (2), 634 nm (3), 515 nm (4), and 491 nm (5) can be described as originating from the ³{[d_x²-y²(Ir) + d_xz(Ir) + π (C^N)] [π∗(C^N)]} excited state with the ³MLCT/³ILCT characters. The calculated results revealed that the phosphorescent color of these new Ir(III) complexes can be tuned by changing the π-conjugation effect strength of the C^N ligand.     

Heterobi- to heterotetrametallic transition metal complexes constructed from ferrocenecarboxylate and [{[Ti](μ-σ,π-CCSiMe3)2}M] units

A series of copper(I) and silver(I) carboxylates received from various ferrocenecarboxylic acids was synthesized and used in the preparation of heterooligometallic Ti-Cu(Ag)-Fe complexes. The silver(I) salts [FcCO₂Ag] (2a) and [FcCHCHCO₂Ag] (2b) (Fc = ferrocenyl, (η⁵-C₅H₄)Fe(η⁵-C₅H₅)) were obtained through deprotonation of the respective acids FcCO₂H (1a) and FcCHCHCO₂H (1b) with NEt₃, followed by a reaction with [AgNO₃]. The heterotrimetallic complexes {[Ti](μ-σ,π-CCSiMe₃)₂}AgO₂CFc (4a) and {[Ti](μ-σ,π-CCSiMe₃)₂}AgO₂CCHCHFc (4b), where [Ti] denotes the (η⁵-C₅H₄SiMe₃)₂Ti unit, were obtained from the reaction of 2a and 2b with the organometallic π-tweezer compound [Ti](CCSiMe₃)₂ (3). The related heterotrimetallic copper(I) complex {[Ti](μ-σ,π-CCSiMe₃)₂}CuO₂CFc (9a) was prepared via two synthetic routes. First, salt 2a was reacted with [(η²-Me₃SiCCSiMe₃)CuBr]₂ (10) to give the alkyne-stabilized copper(I) carboxylate [(η²-Me₃SiCCSiMe₃)(CuO₂CFc)₂]₂ (11). Subsequent reaction of 11 with four equivalents of 3 afforded 9a. Alternatively, 9a and its analogues {[Ti](μ-σ,π-CCSiMe₃)₂}CuO₂C-E-Fc (E = trans-CHCH (9b), CH₂CH₂ (9c)), were prepared from acidolysis of the Cu-C_Me bond in {[Ti](μ-σ,π-CCSiMe₃)₂}CuMe (8) with acids 1a-1c. An analogous reaction between HO₂CfcPPh₂M(CO)₅ (M = Cr (14a), Mo (14b), W (14c); fc = ferrocene-1,1′-diyl) and 8 at−30 °C gave the alkyne/ferrocene-bridged heterotetrametallic compounds {[Ti](μ-σ,π-CCSiMe₃)₂}CuO₂CfcPPh₂M(CO)₅ (M = Cr (15a), Mo (15b), W (15c)). Reversing the reaction steps so that {[Ti](μ-σ,π-CCSiMe₃)₂}CuO₂CfcPPh₂ (12) was prepared first and then reacted with M(CO)₅(thf) (M = Cr (13a), Mo (13b), W (13a)) gave complicated reaction mixtures from which pure 15a-15c could not be isolated. The solid-state structures of 5, 7, 9a, and 11 have been corroborated by single-crystal X-ray structural studies and the electrochemical behavior of acids 1a-1c and of complexes 4a, 4b and 9a-9c was studied by cyclic voltammetry.     

The (phosphino)tetraphenylborate ligand in ruthenium-arene chemistry

The synthesis of a series of anionic half-sandwich ruthenium-arene complexes [E][RuCl₂(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (E = Bu₄N⁺: R = Ph, 1a, ⁱPr, 1b or Cy, 1c; E = bis(triphenylphosphine)iminium or PNP⁺: R = Ph, 1a′, ⁱPr, 1b′ or Cy, 1c′) are reported. X-ray crystallographic studies of 1a′ and 1b′ confirmed the three-legged piano-stool coordination geometry. In solution, complexes 1a-c and 1a′-c′ are proposed to form monomer-dimer equilibria as a result of chloride ligand dissociation. Complexes 1a-c and 1a′-c′ also form the formally neutral zwitterionic complexes [RuCl(L)(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (L = pyridine: R = Ph, 2a, ⁱPr, 2b or Cy, 2c; L = MeCN: R = Ph, 3a, ⁱPr, 3b or Cy, 3c) via chloride ligand abstraction using AgNO₃ or MeOTf.     

Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in methanol gave the adducts [ReX(CO)₃(HLⁿ)] (1a X = Cl, n = 1; 1a′ X = Br, n = 1; 1b X = Cl, n = 2; 1b′ X = Br, n = 2; 1c X = Cl, n = 3; 1c′ X = Br, n = 3) in good yield.All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³, HL³·(CH₃)₂SO and 1b′·H₂O were also elucidated by X-ray diffraction. In 1b′, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (κS,N³) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron.The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆] (2a), [Re₂(L²)₂(CO)₆] (2b) and [Re₂(L³)₂(CO)₆] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a κS,N³-bidentate thiosemicarbazonate ligand.Some single crystals isolated in the synthesis of 2b contain [Re(L⁴)(L²)(CO)₃] (3b) where L⁴ (=2-methylamine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (κS,N²) affording a four-membered chelate ring.     

Syntheses and characterization of η-hexamethylbenzeneruthenium(II)-β-diketone complexes: their reactions with mono- and bidentate neutral ligands

The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂1 react with sodium salts of β-diketonato ligands in methanol to afford the oxygen bonded neutral complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)Cl] {R¹, R² = CH₃ (2), CH₃, C₆H₅ (3), C₆H₅ (4), OCH₃ (5), OC₂H₅ (6)}. Complex 4 with AgBF₄ yields the γ-carbon bonded ruthenium dimeric complex 7. Complex 4 also reacts with tertiary phosphines and bridging ligands to yield complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)(L)]⁺ (L = PPh₃ (8), PMe₂Ph (9)) and [{η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)}₂(μ-L)] L = 4,4′-bipyridine (4,4′-bipy) (11), 1,4-dicyanobenzene (DCB) (12) and pyrazine (Pz) (13). Complexes 2-4 react with sodium azide to yield neutral complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)N₃] {R¹, R² = CH₃ (10a), CH₃, C₆H₅ (10b), C₆H₅ (10c). All these complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures of complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′CH₃COCH-COC₆H₅)Cl] (3) and [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅] (4) were established by single crystal X-ray diffraction studies. The complex 3 crystallizes in the triclinic space group, [a = 7.9517(4), b = 9.0582(4) and c = 14.2373(8) Å, α = 88.442(3)°, β = 76.6.8(3)° and γ = 81.715(3)°. V = 987.17(9) ų, Z = 2]. Complex 4 crystallizes in the monoclinic space group, P2₁/c [a = 7.5894(8), b = 20.708(2) and c = 29.208(3) Å,β = 92.059(3)° V = 4587.5(9) ų, Z = 8].